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Electric Resistance Welded (ERW) Pipe Manufacturing Process

Electric Resistance Welded (ERW) Pipe Manufacturing Process

Date : 2021-03-05

Electric resistance welding (ERW Welded Pipe) is used to transport oil, natural gas and other vapor and liquid objects, which can meet various requirements of high and low pressure, and currently occupies a pivotal position in the field of transportation pipes in the world.

The electric resistance welding pipe is manufactured by cold forming a piece of steel plate into a cylindrical shape, and then passing an electric current between the two edges of the steel plate to heat the steel plate to a point of force, forcing these edges to form a weld that was not initially used Fill the material, but use low frequency alternating current to heat the edges. This low frequency process has been used from the 1920s to the 1970s. In 1970, the low frequency process was replaced by the high frequency ERW pipe process, which produced higher quality welds. Over time, it has been found that the welds of low-frequency ERW pipes are susceptible to selective joint corrosion, hook cracks and insufficient joint bonding. Therefore, low-frequency ERW is no longer used to make pipes. High-frequency processes are still used to make pipes for new pipeline construction.

Resistance welding can be divided into resistance welding and induction welding. The ERW tube is cold formed into a cylindrical shape rather than hot formed. Use electric current instead of flame to heat the edges of the strip for welding. The rotating copper disk is used as an electrode, which can raise the temperature to about 2600°F for effective welding. Unlike longitudinal submerged arc welding, ERW usually uses alternating current with a frequency of 100 to 800 kHz, or 100.000 to 800.000 cycles per second.

This process is characterized by two effects: the skin effect or the concentration of high-frequency current on the surface, and the proximity effect when the high-frequency is concentrated on two adjacent parallel inner edges in the welding wedge before the welding point. These effects minimize the heat released during the welding process. Therefore, the structure of the basic material changes in a relatively small area around the fusion line, the center of the weld. Use a scraping device to remove the molten material on the inside and outside of the weld.


ERW Pipe Manufacturing Process:


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This process is characterized by two effects: the skin effect or the concentration of high-frequency current on the surface, and the proximity effect when the high-frequency is concentrated on two adjacent parallel inner edges in the welding wedge before the welding point. These effects minimize the heat released during the welding process. Therefore, the structure of the basic material changes in a relatively small area around the fusion line, the center of the weld. Use a scraping device to remove the molten material on the inside and outside of the weld.

In the production of ERW steel pipes, only high-quality, continuous casting, fully sedated, controlled rolling, fine-grained low carbon steel is used. High-performance ERW steel pipes and tubes have high strength, corrosion resistance, high deformability, high strength and high toughness. Permanent Steel Manufacturing Co.,Ltd is one of the leading manufacturers and suppliers of ERW tubes in China. We are also one of the largest exporters of ERW pipes in China.

ERW pipe stands for resistance welded pipe. According to customer requirements, we can manufacture ERW steel pipes of different sizes and shapes. We have very large erw pipe production capacity. ERW steel pipes are used for various engineering purposes, including fences, scaffolding, line pipes, etc. The length of the ERW pipe varies from a single random to 120 feet, depending on the capacity of the rolling mill. ERW pipes have square heads or grooves for welding, threaded connections and Victaulic slotting. The surface treatment can be black or bare, or with a protective coating.


Tips: A53 Grade B Seamless is our most popular product under this specification and A53 pipe is commonly dual certified to A106 B Seamless pipe.
ASTM A53 Grade B is the material under the American steel pipe standard, API 5L Gr.B is also the American standard material, A53 GR.B ERW refers to the electric resistance welded steel pipe of A53 GR.B; API 5L GR.B Welded refers to the material Welded steel pipe of API 5L GR.B.

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ASTM Standard Seamless Pipe Quality Inspection

ASTM Standard Seamless Pipe Quality Inspection

Date : 2021-03-01

ASTM standards are widely used in Seamless steel pipe, like the API 5L/5CT, ASTM A106ASTM A53:

1. ASTM American Standard seamless pipe chemical composition analysis
Instrument analysis and chemical analysis can be used. For chemical analysis of the sample sub-melting samples, ingot drill cuttings, pipe samples. Smelting samples generally use instrumental analysis, pipe samples of finished products using chemical analysis and analysis together. Commonly used chemical analysis instruments are: infrared carbon and sulfur instrument, direct reading spectrometer, X-ray fluorescence spectrometer.

2. ASTM American Standard seamless pipe size and shape inspection

Check the contents include: wall thickness, diameter, length, curvature, ovality, port slope and blunt angle and the shape of the cross-sectional shape of steel pipe.


3. ASTM American Standard seamless pipe surface quality testing
Artificial eye examination and non-destructive examination. There are many nondestructive testing methods, such as: ultrasonic flaw detection, eddy current testing, magnetic particle inspection, magnetic flux leakage testing, electromagnetic ultrasonic flaw detection and penetration testing. Each method has its advantages and disadvantages. Suitable for testing steel surface or near surface: eddy current testing, magnetic particle testing, magnetic flux leakage testing, penetrant inspection. The penetrant inspection is limited to the inspection of the open defects on the surface of the steel pipe; magnetic particle inspection, magnetic flux leakage testing, eddy current testing is limited to ferromagnetic materials inspection. Eddy current flaw detection is more sensitive to point defects, other flaws sensitive to cracks. However, the ultrasonic flaw detection has a relatively rapid response to the test of the surface of the steel pipe. There are still some difficulties in the qualitative analysis of the steel pipe, and the ultrasonic inspection is also limited by the shape and grain size of the steel pipe.

4. ASTM American Standard seamless pipe chemical testings
Mechanical properties tests (tensile test, ductility test, hardness test), hydraulic test and corrosion test (intergranular corrosion test, hydrogen cracking resistance test -HIC, sulfur sulfide stress cracking test -SSCC) at room temperature or at a certain temperature.
 
5. ASTM American Standard seamless pipe technology performance test
Including flattening test, ring pull test, flaring and curling test, bending test.

6. ASTM American Standard seamless pipe metallographic analysis
Including low magnification and high magnification inspection.

7. Petroleum pipe thread parameter testing

Including the coupling detection, pipe thread detection and pipe body and the coupling after the tightening test.


Extended information:
1. Annealed seamless steel pipes with inner diameters above 6.0mm and wall thickness below 13mm can use W-B75 Webster hardness tester, which is very fast and easy to test, and is suitable for seamless steel pipes. Fast and non-destructive qualification inspection.
2. For seamless steel pipes with inner diameter greater than 30mm and wall thickness greater than 1.2mm, use Rockwell hardness tester to test HRB and HRC hardness.
3. For seamless steel pipes with inner diameter greater than 30mm and wall thickness less than 1.2mm, the surface Rockwell hardness tester shall be used to test the hardness of HRT or HRN.
4. For seamless steel pipes with inner diameters less than 0mm and greater than 4.8mm, use Rockwell hardness tester for pipes to test HR15T hardness.
5. When the inner diameter of the seamless steel pipe is greater than 26mm, the hardness of the inner wall of the pipe can also be tested with a Rockwell or surface Rockwell hardness tester.


Tips: ASTM A53 covers seamless and welded steel pipe with nominal wall thickness. The surface condition is usually black and hot-dipped galvanized. ASTM A53 is produced mainly for pressure and mechanical applications, and is also used for transport of steam, water, gas line pipes.

ASTM A53 ERW steel pipe is a typical carbon steel pipe. It is largely used to convey fluids at low / medium pressures such as oil, gas, steam, water, air and also for mechanical applications.

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Differences Between Seamless Casing and ERW Casing Pipe

Date : 2021-03-05

According to the manufacturing method, the steel pipe can be divided into two categories: seamless steel pipe and welded seam steel pipe. Among them, ERW steel pipe is the main variety of welded steel pipe. Today, we mainly talk about two kinds of steel pipes used as raw materials for petroleum Casing pipe: Seamless casing and ERW casing.

Seamless casing - Casing made of seamless steel pipe as raw material;
Seamless steel tubes refer to steel tubes manufactured by four methods: hot rolling, cold rolling, hot drawing, and cold drawing. There are no welds on the pipe body itself.

ERW casing - Casing made of electric welded pipe as raw material

ERW (Electric Resistant Weld) steel pipe refers to a straight seam welded pipe manufactured through a high-frequency resistance welding process. The raw material steel plate (coil) of ERW welded pipe is made of low-carbon microalloy steel rolled by TMCP (Thermo-Mechanical Control Process).


1. Outer diameter tolerance
Seamless steel pipe: Hot-rolled forming process is used, and the sizing is completed at about 8000C. The raw material composition, cooling condition and cooling state of the roller have a great influence on its outer diameter, so the outer diameter control is difficult to be accurate and fluctuates The range is larger.
ERW steel pipe: adopts cold-formed forming and sizing by 0.6% reduction. The process temperature is basically constant at room temperature, so the outer diameter control is accurate and the fluctuation range is small, which is helpful to eliminate black leather buckles;

2. Wall thickness tolerance
Seamless steel pipe: It is produced by round steel perforation, and the wall thickness deviation is large. The subsequent hot rolling can partially eliminate the unevenness of the wall thickness, but the most advanced unit can only be controlled within ±5~10%t.
ERW steel pipe: using hot-rolled coil as raw material, the thickness tolerance of modern hot-rolling can be controlled within 0.05mm.

3. Appearance
The outer surface defects of the blanks used in seamless steel pipes cannot be eliminated by the hot rolling process, and the defects can only be polished off after the finished product is finished; the spiral path left after perforation can only be partially eliminated in the wall reduction process.
ERW steel pipe uses hot-rolled coils as raw materials. The surface quality of the coils is the surface quality of ERW steel pipes. The surface quality of hot-rolled coils is easy to control and high in quality. Therefore, the surface quality of ERW steel pipes is much better than seamless steel pipes. 

4. Ovality
Seamless steel pipe: hot-rolled forming process is adopted. The raw material composition of the steel pipe, the cooling condition and the cooling state of the roll have a great influence on its outer diameter, so it is difficult to control the outer diameter accurately and the fluctuation range is large.
ERW steel pipe: adopts cold bending forming, so the outer diameter control is accurate and the fluctuation range is small.

5. Tensile test
The tensile performance indexes of seamless steel pipes and ERW steel pipes conform to API standards, but the strength of seamless steel pipes is generally at the upper limit and the plasticity is at the lower limit. In comparison, the strength index of ERW steel pipes is in the best state, and the plasticity index is 33.3% higher than the standard. The reason is that the performance of hot-rolled coils, the raw material of ERW steel pipes, is guaranteed by means of microalloying smelting, out-of-furnace refining, and controlled cold and controlled rolling; seamless steel pipes mainly rely on means to increase carbon content, which is difficult to ensure strength and plasticity. Reasonable match.

6. Hardness
The raw material of ERW steel pipe, hot-rolled coil, has extremely high precision during the rolling process, which can ensure the uniform performance of all parts of the coil.

7. Grain size
The raw material of ERW steel pipe-hot-rolled coils are made of wide and thick continuous casting billets, with a thicker fine-grained surface solidification layer, no columnar crystal regions, shrinkage and porosity, small composition deviation, and compact structure; in the subsequent rolling process The application of controlled cold and controlled rolling technology further ensures the grain size of raw materials.

8. Anti-collapse test
ERW steel pipe is due to the characteristics of its raw materials and pipe making process. Its wall thickness uniformity and ellipticity are far superior to seamless steel pipes, which is the main reason why the collapse resistance performance is higher than that of seamless steel pipes.

9. Impact test
Since the impact toughness of the base material of ERW steel pipe is several times that of seamless steel pipe, the impact toughness of the weld is the key to ERW steel pipe. By controlling the impurity content of raw materials, the height and direction of slitting burrs, the shape of forming edges, the welding angle, and the welding speed , Heating power and frequency, welding extrusion volume, intermediate frequency withdrawal temperature and depth, air cooling section length and other process parameters ensure that the impact energy of the weld reaches more than 60% of the base metal. If further optimized, the weld impact energy can be close to the base Material to achieve seamless performance.

10. Blasting test
The blasting test performance of ERW steel pipe is much higher than the standard requirement, mainly due to the high uniformity of wall thickness and uniform outer diameter of ERW steel pipe.

11.Straightness
The seamless steel pipe is formed in a plastic state, and the straightness of the pipe end is relatively difficult to control with the single ruler (3 to 4 times ruler for continuous rolling);
ERW steel pipe is cold-worked, and it has online straightening in the state of reducing diameter. In addition, it is infinite times, so the straightness is better.

12.The consumption of steel for 10,000-meter footage casing
The wall thickness of ERW steel pipe is uniform, and its wall thickness tolerance can be ignored. The control accuracy limit of seamless steel pipe wall thickness difference is ±5%t, and it is generally controlled at ±5-10%t. In order to ensure that the minimum wall thickness can meet the standard requirements and performance, the solution can only be solved by appropriately increasing the wall thickness. Therefore, in the casing of the same specification and the same weight, the ERW steel pipe is 5-10% longer than the seamless steel pipe, or even more, which reduces the steel consumption of the casing for 10,000 meters by 5-10%. Even at the same price, ERW casing virtually saves users 5-10% of purchasing costs.

To sum up:

As far as the current domestic and foreign situations are concerned, it is more seamless to use. Because ERW\'s current casing steel grade can only be controlled at the highest K55, if the steel grade is higher, China does not have this production capacity. As far as the current ERW market is concerned, Japanese production equipment and production are still used for casing. The process can reach a certain level, but it can only be produced to N80. If you want to produce steel grades of P110 or higher, it is currently difficult, so ERW can only be used for surface casing.


Tips: Straight seam steel pipe is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. Straight seam steel pipes can be divided into high-frequency straight seam steel pipes (ERW) and submerged arc welded straight seam steel pipes (LSAW)  according to the production process. Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development.

ASTM A53 Grade B is the material under the American steel pipe standard, API 5L Gr.B is also the American standard material, A53 GR.B ERW refers to the electric resistance welded steel pipe of A53 GR.B; API 5L GR.B Welded refers to the material Welded steel pipe of API 5L GR.B.


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Cold Drawn ERW Pipe, DOM Pipe

Date : 2021-03-09

Cold drawn erw pipe, which is one of the best choices for the production of multi-stage hydraulic cylinders. Its process is the same as that of precision seamless pipe cold drawing. It is precision drawn by precision resistance welding (ERW) and manufactured with EN. 10305-2 EU mechanical cold drawn carbon steel welded pipe standard.

After the electric resistance welded pipe is welded, the whole pipe body is normalized to ensure the homogeneity of the weld and the heat affected zone with the rest of the metallographic structure and mechanical properties; cold drawing and subsequent heat treatment (eliminating internal stress) and the steel pipe have good dimensions. And mechanical properties.

After the welded steel pipe is processed by cold drawing and deep processing, a high-quality steel pipe with small dimensional tolerance and good mechanical properties is obtained.

In addition, cold drawn welded pipes have significant advantages over cold drawn seamless pipes in terms of initial cost and reduced machine tool processing costs.


What is DOM tube?

DOM (Drawn Over Mandrel) refers to a production process.

To produce specialty tubing, this procedure uses a drawbench to pull tubing through a die and over a mandrel, allowing excellent control of the inside diameter and wall thickness.


Drawn Over Mandrel (DOM) Round Mechanical Tubing is a cold drawn 1020/1026 electric resistance welded tube with all the flash removed prior to cold drawing. In comparison to other tubing, DOM round steel tubing is produced to more exact OD and ID tolerances, and has the highest weld strength possible.
The DOM tube is a precision steel tube made of ERW steel pipe as raw material and processed by cold drawing.


Tips: In case ASTM A53 Grade B in ERW (electric resistance welded) pipe, the weld seam shall be done the heat treatment with a minimum 1000°F [540°C]. In this way the no untempered martensite remains.
In case ASTM A53 B pipe in cold expanded, then expansion should not exceed 1.5% of the required OD.

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What are the Reasons for the Damage of the Oil Casing Pipe?

Date : 2021-03-09

Petroleum casing pipe is widely used in oil field work tasks, so the damage of the oil casing will seriously affect the work of the oil field and greatly reduce the work efficiency. The following oil casing manufacturers take you to learn more about the factors that cause oil casing damage, and hope to avoid the corrosive factors of the oil casing as much as possible in the future.

Inclusions: 

Some sandy inclusions will be mixed into the injected water. If the injected water is not filtered, the inclusions in the water will enter the casing with the water flow, causing the gap between the casings to be no longer compact, making the casing Under normal circumstances, the strength of the support is lost in the application link, the internal stress is changed, and the casing is finally damaged.

Under normal circumstances, there is a corresponding relationship between underground pressures, the pressure of the overlying strata = the pressure of the formation crevices + the pressure of the strata framework. The increase of sand will increase the pressure of the rock formation between the casings, resulting in pressure imbalances and subsidence of the formation, which will cause the tubing and casing to bend and deform, causing damage to it.

Corrosion: 

Crude oil generally contains corrosion-resistant substances, such as CO2 and nitrides. These substances will inevitably be corrosive to oil casing during operation. In addition, the water injected during the oil extraction process also contains certain corrosion-resistant substances, which will definitely cause corrosion to the casing of the oil field.

Water injection: 

In order to effectively ensure a stable oil production rate, oil manufacturers generally inject more water during the oil extraction process. Obviously, considering that there are many cracks or fault structures in the lower layer of the oil well, there is no way to master the water injection volume in the water injection process. Too much water will seep into the cracks or faults in the lower layer of the oil field, and eventually cause corresponding internal stress changes in the lower layer, so that the internal stress experienced by the casing in the lower layer of the oil field will change, and then the internal stress of the oil casing will be unbalanced. When the oil casing cannot withstand the overload internal stress, the oil pipeline cracks and other situations will immediately occur. In addition, the complex topography and characteristics of the bottom of the oil field will also affect the oil casing. More rocks and other materials at the bottom of some oil fields will affect the use of oil casing and bring corresponding effects on the oil casing.

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Production Process of Hot-rolled Seamless Steel Pipe

Date : 2021-03-16

Hot-rolled seamless steel pipe: Hot rolling is relative to cold rolling, cold rolling is rolling below the recrystallization temperature, and hot rolling is rolling above the recrystallization temperature.

The basic processes of the production process of hot-rolled seamless steel pipes include:


Tube blank preparation and inspection △→Tube heating→Perforation→Rolling pipe→Steel pipe reheating→fixed (reduced) diameter→Heat treatment△→Finished pipe straightening→Finishing→Inspection△(Non-destructive, physical and chemical, bench inspection)→Warehousing


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There are generally three main deformation processes in the production of hot-rolled seamless steel pipes: piercing, pipe rolling, and sizing and reducing. The respective process objectives and requirements are as follows.

1. Piercing

Perforation is to pierce a solid tube into a hollow capillary. The equipment is called a piercing machine: The requirements for the piercing process are:
(1) Ensure that the wall thickness of the capillary that passes through is uniform, the ovality is small, and the geometrical dimension accuracy is high;
(2) The inner and outer surfaces of the capillary tube are relatively smooth, and there must be no defects such as scars, folds, cracks, etc.;
(3) There must be a corresponding piercing speed and rolling cycle to adapt to the production rhythm of the entire unit, so that the final rolling temperature of the capillary tube can meet the requirements of the tube rolling mill.

2. Rolling pipe

The rolled pipe is to press the perforated thick-walled capillary tube into a thin-walled waste tube to achieve the required thermal size and uniformity of the finished tube. That is, the wall thickness of the waste pipe in this process is determined according to the reduction amount of the subsequent process and the empirical formula to process the wall thickness. This equipment is called a pipe rolling mill.

The requirements for the rolling process are:
(1) When turning thick-walled capillaries into thin-walled waste pipes (reduced-wall extension), first ensure that the waste pipes have a high uniformity of wall thickness;
(2) The waste pipe has good internal and external surface quality. The selection of the tube mill and the reasonable matching of its deformation with the piercing process are the key to determining the quality, output and technical and economic indicators of the unit.

3. Fixed (reduced) diameter

The main function of sizing and reduction is to eliminate the difference in the outer diameter of the waste pipe caused by the rolling process in the previous process, so as to improve the outer diameter accuracy and roundness of the hot-rolled finished pipe. Diameter reduction is to reduce the large pipe diameter to the required size and accuracy. Tension reduction is to reduce the diameter under the action of the front and rear frame tension, while reducing the wall. The equipment used for sizing and reducing is a sizing (reducing) machine. The requirements for the sizing and reducing process are:

(1) To achieve the purpose of sizing under the conditions of a certain total reduction rate and a smaller single frame reduction rate;
(2) It can realize the task of using one size tube blank to produce multiple sizes of finished tubes;
(3) Further improve the outer surface quality of the steel pipe.

At the end of the 1980s, there was a tendency to abolish the pipe rolling process, and only use the method of perforation plus diameter reduction to produce seamless steel pipes, referred to as CPS, and it was held in Tosa, South Africa from March 1990 to July 1991. The factory has carried out industrial tests and produced steel pipes with an outer diameter of φ33.4~φ179.8mm and a wall thickness of 3.4~25mm. The minimum diameter of the fixed diameter is 101.6mm. Through practical tests, the process has acceptable quality when producing steel pipes with wall thickness greater than 10mm, but sizing and tension reduction cannot completely eliminate the spiral line of the perforated capillary when producing steel pipes with a wall thickness of less than 8mm, which affects the appearance quality of the steel pipe. 


Tips: ASTM A53 covers seamless and welded steel pipe with nominal wall thickness. The surface condition is usually black and hot-dipped galvanized. ASTM A53 is produced mainly for pressure and mechanical applications, and is also used for transport of steam, water, gas line pipes. ASTM A53 Grade B is more popular than other grades. These pipes can be bare pipes without any coating, or it may be Hot-Dipped or Zinc-Coated and manufactured by Welding or by a Seamless manufacturing process.

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Welded Vs. Seamless Stainless Steel Pipe

Date : 2021-03-23

Stainless steel pipes can be divided into stainless steel welded pipes and stainless steel seamless pipes. Many people do not know the difference between them. How to choose? The following stainless steel manufacturers will talk about the difference between the two in detail.

1. The difference in production process

Stainless steel welded pipe: It is welded by steel plate or steel strip after being crimped and formed by the unit and mold. Different welding methods can be divided into straight seam welded pipe and spiral welded pipe.

Seamless pipe: It uses round steel perforated as the raw material of the tube blank, and is made by the production process of cold rolling, cold drawing or hot extrusion.


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2. The difference between the appearance and concentricity of the steel pipe


Stainless steel welded pipe: Seam pipe is made of precise cold-rolled sheet. These cold-rolled sheets usually have a maximum wall thickness difference of 0.002 inches. The steel plate is cut to a width of πd, where d is the outer diameter of the pipe. The tolerance of the wall thickness of the slotted pipe is very small, and the wall thickness is very uniform throughout the circumference. The steel pipe has high precision, uniform wall thickness, high brightness inside and outside the pipe (the surface brightness of the steel pipe is determined by the surface grade of the steel plate), can be arbitrarily fixed length, and can be used as a thin-walled pipe.

Seamless pipe: The manufacturing process of seamless steel pipe is to punch a hole in a stainless steel billet at a temperature of 2200°f. At this high temperature, the tool steel becomes soft and spirals out of the hole after punching and drawing. Shaped out. In this way, the wall thickness of the pipeline is uneven and the eccentricity is high. The steel pipe has low precision, uneven wall thickness, low brightness on the inside and outside of the pipe, high cost of sizing, and there are pits and black spots on the inside and outside that are not easy to remove, so astm allows the wall thickness difference of seamless pipes than that of seamed pipes The difference is large, usually the pipe wall is thicker.

3. Different welding performance

Stainless steel welded pipe: due to differences in material chemical composition. The steel for the production of seamed pipes contains a chemical composition suitable for welding. For example, the mixing of elements such as silicon, sulfur, manganese, oxygen, and triangular ferrite in a certain proportion can produce a weld melt that is easy to transfer heat during the welding process, so that the entire weld can be penetrated.

Seamless pipe: The steel composition of the seamless tube is only the basic requirement of astm. Steel pipes lacking the above chemical composition, such as seamless pipes, will produce various unstable factors during the welding process, and are not easy to weld firmly and incompletely.

4. Grain size

The grain size of the metal is related to the heat treatment temperature and the time to maintain the same temperature. The grain size of the annealed seamed stainless steel tube and seamless stainless steel tube are the same. If the seam pipe adopts the minimum cold treatment, the grain size of the weld is smaller than the grain size of the welded metal, otherwise, the grain size is the same.


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5. Pipe strength

The strength of the pipeline depends on the alloy composition, so seamless stainless steel pipes and seamed stainless steel pipes containing the same alloy and the same heat treatment are essentially the same in strength.

After the tensile test and the three-dimensional vibration test, the tearing of the seamed stainless steel pipe almost all occurred in a place far away from the welding point or the heated area. This is because the weld is less impurity and the nitrogen content is slightly higher, so the strength of the weld is better than other parts. However, ASME believes that seamed stainless steel pipes can only withstand 85% of the allowable pressure. This is mainly due to data collection earlier than the improved welding equipment used today.

6. The difference in application

Stainless steel welded pipe: With its good surface effect, it is commonly used in decorative pipes, prop pipes, and product pipes. Its pressure-bearing performance is general, mainly used for conveying water, oil, gas, air, and heating hot water or steam and other generally lower pressure fluids.

Seamless pipe: With its good corrosion resistance, pressure-bearing and high-temperature resistance, stainless steel seamless pipes can be used to transport fluid pipelines in engineering and large equipment, and can also be used to transport fluids with high temperature and high pressure on boilers in power plants and nuclear power plants. Headers and pipes, etc.

Now in some industries, welded pipes can gradually replace seamless pipes. Because of their low price and stable performance, they are gradually being loved by people. Permanent Steel Manufacturing Co., Ltd has focused on the production of stainless steel welded pipes for many years and successfully cooperated with many stainless steel seamless pipes. Demand manufacturers, they have gradually used stainless steel welded pipes.

Tips: ASTM A53 covers seamless and welded steel pipe (a53b erw) with nominal wall thickness. The surface condition is usually black and hot-dipped galvanized. ASTM A53 is produced mainly for pressure and mechanical applications, and is also used for transport of steam, water, gas line pipes.

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3 Aspects to Prevent Oil Casing Pipe Damage

Date : 2021-03-23

1. Prevent drilling damage to the oil casing
In order to prevent drilling damage to the casing pipe, two points should be paid attention to:
(1) Petroleum casing with corresponding anti-corrosion performance should be selected according to the specific conditions at the bottom of the oil well;

(2) Petroleum personnel should optimize the drilling design plan before drilling operations, so that relevant personnel can reduce the wellbore curve rate and reduce the stress change of the oil casing during the drilling operation, so as to ensure the quality of the drilling and prevent damage during the drilling process Oil Casing.


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2. Optimize perforation technology to ensure cementing quality
In the perforation operation, the relevant parameters of the perforation operation should be optimized first to improve the accuracy of the perforation process and avoid damage to the oil casing during the perforation operation. The relevant management personnel of the oil company should strengthen the supervision of the implementation of the perforation process, and ensure that the relevant personnel perform the perforation operations in strict accordance with the implementation process of the perforation process to ensure the quality of cementing and the quality of the oil casing.

3. Use anti-corrosion technology to avoid damage to tubing and casing
Oil companies can use anti-corrosion technology to avoid damage to the oil casing.
The main methods are as follows:
(1) Some anti-corrosion additives should be added to the water during water injection during oil exploitation to reduce damage to the oil casing.
(2) In the face of electrochemical corrosion, a certain current can be connected to the oil casing, and the transfer of casing corrosion can be realized to avoid damage to the oil casing.
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Comparison of Straight Seam Steel Pipe and Spiral Steel Pipe

Date : 2021-03-29

The production process of straight seam steel pipes is relatively simple, and the main content of the production process is high-frequency welded straight seam steel pipes (ERW) and submerged arc welded straight seam steel pipes (LSAW). The production efficiency of straight seam steel pipes is high, the cost is low, and the economy develops rapidly. The strength design of spiral steel pipes (SSAW) is usually higher than that of straight seam steel pipes.

The main content of steel pipe production technology is submerged arc welding. Spiral steel pipes can be used to produce welded pipes with the same width of billets and different diameters, or narrow billets can be used to produce welded pipes with larger diameters. However, compared with the straight seam steel pipe of the same length, the welding length is increased by 30% and 100% respectively, and the production speed is relatively low. Therefore, most large-diameter steel pipes are welded by spirals, while most small-diameter steel pipes are welded by straight seams. In the industrial production of large-diameter straight-seam steel pipes, T-welding construction technology is adopted, that is, two small straight-seam steel pipes are butt-connected to meet the length required for enterprise projects. The defects of T-shaped straight seam steel pipes are more obvious. The residual stress in the T-shaped weld welding process is very large. The welded metal structure material is usually in a triaxial stress state, which increases the possibility of cracking.


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In the welding process and process design, the welding method of spiral steel pipe and direct welded steel pipe is the same, but it will inevitably lead to the appearance of a large number of T-shaped welds, and the welding residual stress of T-shaped welds has a great influence. Therefore, the technical defects of welding also need to be improved. The improved weld metal structure reduces the possibility of steel pipe cracking.

In addition, according to the technical specifications of submerged arc welding, each weld must be treated in time for arc ignition and arc extinguishing. However, each steel pipe cannot meet this condition when welding the circumferential seam. Therefore, there may be a problem in the arc suppression process. There are more and more welding structural defects.

When the pipeline is under internal working pressure, two main stresses can usually be generated on the pipeline wall, radial stress and axial stress. Comprehensive analysis of the stress at the weld, where α is the helix angle of the weld of the spiral structure steel pipe.

The comprehensive stress at the weld of the spiral structure is different from that of the straight seam steel pipe. Under the same working pressure, the wall thickness of the spiral steel pipe with the same diameter is smaller than that of the straight seam steel pipe.

When parallel defects appear near spiral welds, the expansion risk of spiral welds is less than that of straight welds because the force of spiral welds is very small. Since the different radial stress is the maximum stress on the steel pipe, the weld must be able to withstand the maximum load in the vertical stress direction. The load on the weld has the greatest influence, the load on the circumferential seam is the smallest, and the load factor on the spiral weld is between the two.

The development trend of pipelines is large diameter and high strength. With the increase of steel pipe diameter and steel type in my country, although spiral steel pipe and straight seam steel pipe have the same grade, spiral steel pipe has relatively high impact toughness, which is the difference between different steel pipes.


Tips: ASTM A53 Grade B is more popular than other grades. These pipes can be bare pipes without any coating, or it may be Hot-Dipped or Zinc-Coated and manufactured by Welding or by a Seamless manufacturing process. In Oil and Gas, A53 grade pipes are used in the structural and non-critical applications. 

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What are the Precautions for Ordering Seamless Steel Pipes?

Date : 2021-04-08

\"Ordering\" is the beginning of cooperation between the supplier and the buyer. In order for the buyer to obtain steel pipes that meet the requirements for use, and for the supplier to produce steel pipes that can meet the requirements of the buyer, the two parties need to fully communicate and communicate during the \"ordering\" link.

1. First select and calibrate: the orderer should determine the type of steel pipe according to the working status and use requirements of the steel pipe, whether it is a seamless steel pipe or a welded steel pipe, and the working status of the steel pipe in use: it is used to transport fluid (including fluid State and nature), or used as a mechanical component, to determine whether it meets their own requirements for use.
2. According to the \"order content\" required in the standard, select the external dimensions of the required steel pipe, including diameter, wall thickness and length.

3. The clauses in the standard related to the technical requirements for steel pipe delivery are the core content of this standard, which determines whether the steel pipe can meet the requirements of the orderer.


\"seamless


These mainly include:
(1) Steel grade, chemical composition and manufacturing method;
(2) The allowable deviation of steel pipe shape (outer diameter, wall thickness, length, curvature, ovality, pipe end shape) and its accuracy grade;
(3) Delivery status, including surface condition, heat treatment condition, pressure treatment condition and metallographic structure condition;
(4) The processing performance of the steel pipe (including bending, flattening, flaring, etc.);
(5) The specific provisions of the standard on the surface defects of steel pipes, including the type, name, severity of the defects, the allowable level after cleaning, and the roughness requirements for high-precision steel pipes;
(6) Non-destructive testing of steel pipes (including hydraulic testing, ultrasonic testing, eddy current testing, etc.).

4. According to the different guarantee conditions of different grades in the standard, select the steel grade that meets the requirements of the orderer. Confirm the manufacturing method specified in the standard, find the allowable deviation of the order specification and select the accuracy level.
5. The orderer shall, according to the material\'s requirements for the mechanical properties and processing performance of the steel pipe in the deep processing, and the relevant values of the mechanical properties and processing performance that the steel pipe can guarantee.
6. Finally put forward the order quantity and negotiate the delivery date with the supplier. After confirming all the contents, the orderer will fill in the order form.

7. If it is difficult for the orderer to complete the above clauses 4 and 5, the orderer should specify the processing method and specific processing requirements of the steel pipe material as well as the processing of the material, the use requirements of the finished parts, or the processing performance range and the corresponding delivery The status is submitted to the supplier, so that the supplier can organize the production of steel pipe products that meet the requirements of the orderer according to the agreed value.


Tips: ASTM A53 Grade B steel pipe is intended mechanical and pressure applications, but is also acceptable for and widely used in air, water, steam, and gas lines. A53 pipe is suitable for welding.

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ERW Steel Pipe & Tube Production Line

Date : 2021-05-24

The ERW steel pipe & tube rolling mill is a series of pipe machines, which use a certain width of steel strip to manufacture longitudinal welded pipes.


The erw steel pipe production line is to form various metal pipe raw materials (plain carbon steel, aluminum, stainless steel, non-ferrous metals, etc.) through extrusion deformation and other means (round pipe, square pipe, special-shaped pipe, etc.), using resistance welding technology for welding, sizing the welded pipe through squeeze rollers (making various pipe diameters), and cutting the pipe to length (according to the required length) through a computer flying saw to obtain a complete set of metal pipe products Production equipment.


First, the uncoiled steel coil is unwound and flattened into a steel strip. The flattened steel strip will be inserted into the forming machine, and the rollers in the machine will bend the steel strip into a circular tube shape, and then send the circular tube into welding Box, where high-frequency or solid-state welding machine is used for welding. The pipe is formed into the desired shape (round/square/rectangular, etc.) or size in the setting machine. Finally, cut the pipe to a certain length and tie it up.


\"Cold


The complete erw steel pipe production line mainly includes: decoiler-strip leveling-shearing butt welding machine-material cage / storage looper-forming machine-welding machine-burr removal-sizing machine-flaw detection-flying saw cutting -Initial inspection-steel pipe straightening-pipe section processing-hydraulic test-flaw detection and so on.


The related equipment of the erw steel pipe production line is mainly CNC cabinets, including: high-frequency main cabinet, high-frequency inverter cabinet, speed control cabinet (also commonly known as \"drag\"), computer flying saw CNC machine (also called \"computer flying saw Console\") etc.


Tips: In case ASTM A53 Grade B in ERW (electric resistance welded) pipe, the weld seam shall be done the heat treatment with a minimum 1000°F [540°C]. In this way the no untempered martensite remains.
In case ASTM A53 B erw pipe in cold expanded, then expansion should not exceed 1.5% of the required OD.

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The Origin and Development of Electric Resistance Welded Pipe

Date : 2021-05-31

The seamless welded pipe production technology was invented in Germany, and the technology since then is mainly in Germany. The United States is a pioneer in the development of electric resistance welded pipe (ERW welded pipe) production technology. Since its birth, there have been major technological advances almost every ten years. During this period, the United States has always been the protagonist of technological progress. Other countries can only look forward to the project and adopt the method of introducing technology. American Elihu Thomson invented the application of resistance heating to welding metals. Around 1900, a large number of pipe making methods based on the Thomson principle appeared. Several typical methods were: the method invented by the American Standard Welding Company; the method invented by the German R. Kronenberg; the method invented by the Norwegian Soennichsen and the lap resistance law. Although these methods quickly disappeared, they provided the possibility for people to use resistance energy to weld steel pipes and pointed out the future development direction.

Elihu Thomson (1853-1937) was born in England and was an electrical engineer with outstanding ability. In 1892, he and Edison founded the world-famous General Electric Company. It was this electrical engineer who invented the method of welding using resistance heat (Joule heat Q=I2R). Thomson has obtained nearly 700 patents in his lifetime, including not only AC motors and transformers, but also a variety of electric welding methods, mainly involving flash butt welding, spot welding or lap welding of steel plates, wires, bars, and steel pipes. But these None of the patents directly relates to today\'s electric resistance welded steel pipe process. Nevertheless, we should see Thomson\'s contribution to the origin of resistance welded pipes, because the basic technologies and devices required at the beginning of the birth of high-frequency steel pipes are covered in its patents.


\"erw


In 1900, the Standard Welding Company of Cleveland, Ohio, combined electric resistance welding technology with high-frequency steel pipe technology and obtained a patent. The process steps of this patent include: first forming a steel pipe with an open welded seam, and then applying current to the edges of the electrode rods in contact with the two edges, and at the same time forming butt welding of the heated edges of the other squeeze rollers.

The key point of this patent is the distance between the center of the electrode roll and the center of the squeeze roll. This distance must be set correctly to offset the adverse effects of frequency. Thomson and his partners designed a unit based on this patent, which can produce thin-walled, small-diameter steel pipes for bicycle frames. This is the earliest commercial electric resistance welded steel pipe product.

Subsequently, similar methods were adopted in Germany to produce electric resistance welded pipes. The first was Rudolf Kronenberg of Kronprinz. He successfully converted the brazing of bicycle rims into electric resistance welding, and based on his experience in rim forming and transformer production, he established a high-frequency steel tube unit similar to Standard Welding. Before World War I, the steel pipe factory was producing frames for bicycles. Since then, a number of production lines using alternating current to produce high-frequency steel pipes have been established in the United States and Germany.

Electric resistance welded pipe originated in the 1890s. What is interesting is that there have been major technological advances almost every 10 years since its birth. The early development of electric resistance welded pipe can be roughly divided into five stages: the origin stage, the commercial application stage, the multi-frequency stage, the intermediate frequency conversion stage and the high frequency stage.

As a historical review, the text focuses on the events before the 1880s. Since then, electric resistance welded pipe production technology has entered a relatively stable stage of development, but significant technological progress has been made in coil raw materials, welding technology, automatic control technology, information management, and non-destructive testing.

Since the development of electric resistance welded pipe, it has become the largest steel pipe variety, surpassing seamless steel pipe in the world, and is used in various fields.
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How to Distinguish the Thread of Oil Casing Pipe?

Date : 2021-06-07

Oil casing buckle type code: short circle (BTC), long circle (LC), buttress (BC), some imported goods are marked with the word LTC, that is, long threaded oil casing pipe.


Let us follow the oil casing manufacturers to learn more about it:

Common tubing thread

Tubing thread is commonly divided into three types: EU, NU and New Vam. These three types of buckle can be found in the tool shop, among which EU and NU are difficult to distinguish from the appearance of the buckle alone, and they are all triangular buckle types. But it can be easily distinguished from the entire pipe string, that is, EU means external thickening, and NU means no external thickening.

New Vam is actually a trapezoidal buckle (the cross section of the buckle is rectangular), and it is also not thickened outside, so it is easy to distinguish.

The three types of buckles will be described in detail below with schematic diagrams.

1) EU(External upset)

\"\"


EU is an outer thickened tubing buckle type. Three kinds of EU-related Biano logos will also be found in the process of recognizing the variable buckle joints on the shop shelves.
Among them, EUE (External Upset End) represents the outer upset end, EUP (External Upset Pin) represents the outer upset male buckle, and EUB (Extermal Upset Box) represents the outer upset female buckle.
In addition to using pin and box to indicate male and female buttons, the others indicate that there are 1. external thread; 2. male; 3. male thread. The female buckle has 1. female thread; 2. internal thread; 3. box; 4. box thread.



2) NU (Non-upset)

\"\"

NU is a kind of non-upset oil pipe joint, in addition to no external upset, NU is usually 10 threads per inch and EU is 8 threads per inch. NUE represents a non thickening end or end thickening.




3) New Vam

\"\"This thread is substantially rectangular-shaped cross section, equal pitch intervals, little taper and no external upset. The VAM with excellent performance, high connecting strength and good sealing effectcan meet requirements of different service conditions. This thread is widely used in all kinds of special thread and it belongs to the high quality special thread. VAM follow the thread specification of API, thus inherits the advantages of high bonding strength. It improved Screw seal form in order to overcome the poor sealing performance.
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Seamless Steel Pipe Normalizing, Quenching and Tempering Process

Date : 2021-06-15

1) Normalizing of seamless steel pipe
Process: The steel parts are heated to 40~60°C above the critical temperature, kept for a certain period of time, and then cooled and heat treated in the air.

Purpose: 
①Improve the organization structure and cutting performance;
②For parts with low requirements for mechanical properties, normalizing is often used as the final heat treatment;
③ Eliminate internal stress.

2) Seamless steel pipe quenching treatment
Process: The steel parts are heated to the quenching temperature, kept for a period of time, and then rapidly cooled in water, salt water or oil (individual materials are in the air).

Purpose: 
①To obtain higher hardness and wear resistance of steel parts;

②Make the steel parts get some special properties after tempering, such as higher strength, elasticity and toughness, etc.


\"\"


Seamless steel pipe quenching category:
a. Single liquid quenching
Process: The steel parts are heated to the quenching temperature, and after heat preservation, they are cooled in a quenching agent. Single-liquid quenching is only suitable for carbon steel and alloy steel parts with simple shapes and low technical requirements. When quenching, for carbon steel parts with a diameter or thickness greater than 5-8mm, use salt water or water cooling: alloy steel parts use oil cooling.

Purpose:
① Make steel parts obtain higher hardness and wear resistance;
② Make the steel parts get some special properties after tempering, such as higher strength, elasticity and toughness.

b. Double liquid quenching of seamless steel pipe
Process: The steel parts are heated to the quenching temperature. After heat preservation, they are quickly cooled to 300~400C in water, and then moved into oil for cooling.

Purpose:
① Make steel parts obtain higher hardness and wear resistance;
② Make the steel parts get some special properties after tempering, such as higher strength, elasticity and toughness.

c. Flame surface quenching of seamless steel pipe
Process: Spray a flame of mixed combustion of acetylene and oxygen on the surface of the part to quickly heat the part to the quenching temperature, and then immediately spray water on the surface of the part. Flame surface hardening is suitable for single-piece or small batch production. The surface requires hard and wear-resistant large-scale medium-carbon steel and medium-carbon alloy steel parts, such as crankshafts, gears and guide rails, which can withstand impact loads.

Purpose:
① Make steel parts obtain higher hardness and wear resistance;
② Make the steel parts get some special properties after tempering, such as higher strength, elasticity and toughness.

d. Surface induction heating quenching
Process: Put the steel part in the inductor, the inductor generates a magnetic field under the action of a certain frequency of alternating current, and the steel part generates an induced current under the action of the magnetic field, so that the surface of the steel part is rapidly heated (2~10min) to the melting temperature. At this time, water is immediately sprayed onto the surface of the seamless steel pipe. The seamless steel pipe quenched by surface induction heating has a hard and wear-resistant surface, while the core maintains good strength and toughness. Surface induction heating quenching is suitable for medium carbon steel and alloy steel pipes with medium carbon content.

Purpose:
① Make steel parts obtain higher hardness and wear resistance;
②Make the steel parts get some special properties after tempering, such as higher strength, elasticity and toughness.

3) Tempering treatment of seamless steel pipe
Process: The quenched steel parts are heated to below the critical temperature, kept for a period of time, and then cooled in air or oil. Tempering is carried out immediately after quenching and is also the last process of heat treatment.

Purpose:
① Obtain the required mechanical properties. Under normal circumstances, the strength and hardness of parts after quenching are greatly improved, but the plasticity and toughness are significantly reduced, and the actual workpiece conditions of the parts require good strength and initial properties. After selecting an appropriate tempering temperature for tempering, the required mechanical properties can be obtained.
② Stable organization and stable size.

③ Eliminate internal stress.


Tips: ASTM/ASME A53/SA53 seamless and welded steel pipe is a general, all-purpose pipe used in generator plants, refineries, compressor stations, natural gas transmission, and steam conduction. It is acceptable for welding, flanging, and bending.

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Common Defect Detection Methods for Seamless Steel Pipes

Date : 2021-08-16

Magnetic particle testing or penetration testing of seamless steel tubes can effectively find surface defects such as surface cracks, folds, heavy skins, hair lines, pinholes, etc. For ferromagnetic materials, the magnetic particle detection method should be preferred because of its high detection sensitivity; for non-ferromagnetic materials, such as stainless steel seamless steel pipes, the penetration detection method should be used.


\"Non-destructive


When there is less allowance for removal at both ends of seamless steel pipes, due to the structure of the detection device, the ends of the two ends are sometimes not effectively tested, and the ends are the most likely parts of cracks or other defects. If there is a potential crack tendency at the end, the heat effect of welding during installation may also cause the potential crack to propagate. Therefore, attention should also be paid to the inspection of a certain area of the seamless steel pipe after butt welding, and the extension of the defects of the steel pipe end should be discovered in time.

For on-line use of austenitic seamless steel pipes, when the insulation layer is damaged or where rainwater may penetrate, attention should be paid to penetration testing to find defects such as stress corrosion cracks or pitting corrosion. However, magnetic particle or penetrant testing can only detect the outer surface of the steel pipe, and cannot do anything about the defects on the inner surface. The inspection of the inner surface, especially the inspection of cracks, must be carried out by ultrasonic inspection.

Permanent Steel Manufacturing Co.,Ltd specializes in the production of various specifications of seamless steel pipes, high-pressure boiler pipes (seamless boiler tubes), fluid pipes, structural pipes, fertilizer special pipes and alloy steel pipes imported from Germany, the United States, Japan and Italy. The products sold are in compliance with national standards and are applicable to various fields such as engineering, coal mines, textiles, electric power, boilers, machinery, and military industries. The company sells to all parts of the world with good reputation, high-quality products, strong strength and low prices, and its products are deeply trusted by users.
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Mechanical Properties of Oil Casing J55 and K55 in API 5CT Specification

Date : 2021-08-16

Mechanical properties of oil casing pipe J55 and K55 in API 5CT specification:
1. Heat treatment
PSL1 requirements: In API 5CT, J55 and K55 require delivery in rolled state;
PSL2 requirements: In API 5CT, J55 and K55 oil casing should be normalized and tempered as a whole.

2. Tensile test
J55: Yield strength: 379MPa~552MPa; tensile strength ≥517MPa; minimum elongation of J55 is 19%;

K55: Yield strength: 379MPa~552MPa; tensile strength ≥655MPa; minimum elongation of K55 is 15%.


\"J55


3. Impact test
J55 and K55 in API 5CT must be subjected to impact test. The minimum size sample impact test energy is 20J, and the minimum full size sample longitudinal impact energy is 27J.

4. Wall thickness inspection
PSL1: The wall thickness measurement of J55 and K55 has no coverage requirements;
PSL2: Wall thickness measurement J55 and K55 processing full length automatic detection system surface area best coverage rate should reach 25%.

5. Non-destructive testing
PSL1: J55 and K55 do not have mandatory requirements for destructive testing;

PSL2: For all pipelines, J55 and K55 tubing and casing should be tested according to one or more standards specified in the API 5CT specification to determine the inner and outer surfaces of the pipeline. And J55 and K55 can accept L4 longitudinal defect level.


Tips: Oil casing pipes can be divided into different steel grades according to the strength of the steel itself, namely J55, K55, N80, L80, C90, T95, P110, Q125, V150, etc. Different well conditions and depths have different steel grades. In corrosive environments, the casing itself is also required to have corrosion resistance, and in places with complex geological conditions, it is also required to have anti-collapse performance.

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API 5L Line Pipe - PermanentSteel.com

Date : 2021-08-23

The API 5L line pipe is a line pipe that belongs to the American petroleum standard. API SPEC 5L-2011 (line pipe specification) is compiled and issued by the American Petroleum Institute, and is commonly used all over the world. The main materials of the tube are L245, L290, L360, L415, L480, GR.B, X42, X46, X56, X65, X70, X80, X100, etc. 

The line pipe transports the oil, steam, and water extracted from the ground through the line pipe to the oil and natural gas industrial enterprises. Line pipes include seamless pipes and welded steel pipes. The pipe ends have flat ends, threaded ends and socket ends; the connection methods are end welding, coupling connection, socket connection, etc.


\"seamless


Processing technology of API 5L line pipe:

With the development of pipeline steel plate technology and the advancement of welded pipe forming and welding technology, the application scope of pipeline welded pipe is gradually expanding, especially in the range of large-diameter group spacing. Occupying a leading position in the field of line pipes has restricted the development of stainless steel seamless line pipes. In 2004, the output of seamless line pipes was about 400,000 tons. The steel grades include X42-70, and the varieties include onshore line pipes and subsea line pipes.

The production of high steel grade line pipe adopts microalloying heating treatment process. The production cost of stainless steel seamless pipe is significantly higher than that of welded pipe. With the improvement of steel grade, such as X80 and above steel grade line pipe, there is no limit on carbon equivalent. The conventional process of seam steel pipe is difficult to meet user requirements; each 12Cr1moV alloy pipe manufacturer is carrying out scientific research to improve the corrosion resistance of its line pipes and the stable performance in low temperature and high temperature environments.

Types of tempering of API 5L line pipe:

According to the different performance requirements of pipeline steel pipes and the different tempering temperature, tempering can be divided into the following types:
1. Low temperature tempering (150-250°C)
The structure obtained by low temperature tempering is tempered martensite. Its purpose is to reduce the internal stress and brittleness of quenched steel while maintaining the high hardness and high wear resistance of the quenched steel, so as to avoid cracking or premature damage during use. It is mainly used for various high-carbon cutting tools, measuring tools, rolling bearings and carburized parts, etc. The hardness after tempering is generally HRC58-64.

2. Medium temperature tempering (250-500°C)
The structure obtained by tempering at medium temperature is tempered troostite. Its purpose is to obtain high yield strength, elastic limit and high toughness. Therefore, it is mainly used for the treatment of various hot work molds, and the hardness after tempering is generally HRC35-50.

3. High temperature tempering (500-650°C)

The structure obtained by high temperature tempering is tempered sorbite. Traditionally, the heat treatment combining quenching and high temperature tempering is called quenching and tempering treatment, and its purpose is to obtain comprehensive mechanical properties with good strength, hardness, plasticity and toughness. Therefore, it is widely used in important structural parts of automobiles and machine tools, such as connecting rods, bolts, gears and shafts. The hardness after tempering is generally HB200-330.


Permanent Steel Manufacturing Co.,Ltd, as a professional seamless pipe supplier, integrates warehousing, sales, processing, and distribution. It specializes in the management of various seamless steel pipes, as well as the on-demand seamless steel pipes of special processes, special sizes and special materials. Custom-made products are used in various industrial fields such as engineering, coal mines, textiles, electric power, boilers, machinery, and military industries.

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The Basic Principle of High Frequency Welding

Date : 2021-08-23

What is high frequency welding?


High-frequency welding is a new type of welding process that uses the skin effect and neighboring effect produced by high-frequency current to connect steel plates and other metal materials. The emergence and maturity of high-frequency welding technology is a key process in the production of ERW steel pipe. The quality of high-frequency welding directly affects the overall strength, quality level and production speed of welded pipe products.


\"ERW


The basic principle of high frequency welding:

The so-called high frequency refers to the frequency of the alternating current of 50Hz, and generally refers to the high frequency current of 50KHz to 400KHz. When high-frequency current passes through a metal conductor, two peculiar effects are produced: skin effect and proximity effect. High-frequency welding uses these two effects to weld steel pipes. So, what are these two effects?

The skin effect means that when an alternating current of a certain frequency passes through the same conductor, the current density is not uniformly distributed across all sections of the conductor. It will mainly concentrate on the surface of the conductor, that is, the density of the current on the surface of the conductor is high. The density inside the conductor is small, so we vividly call it: \"skin effect\". The skin effect is usually measured by the penetration depth of the current. The smaller the penetration depth, the more significant the skin effect. This penetration depth is proportional to the square root of the resistivity of the conductor, and inversely proportional to the square root of frequency and permeability. In layman\'s terms, the higher the frequency, the more current is concentrated on the surface of the steel plate; the lower the frequency, the more scattered the surface current is. It must be noted that although steel is a conductor, its magnetic permeability will decrease as the temperature rises. That is to say, when the temperature of the steel plate increases, the magnetic permeability will decrease and the skin effect will decrease.


\"Electrical


The proximity effect refers to the fact that when high-frequency current flows in opposite directions between two adjacent conductors, the current will flow intensively to the edges of the two conductors. Even if the two conductors have another shorter side, the current does not follow. Shorter route flow, we call this effect: \"proximity effect\".

The proximity effect is essentially due to the role of inductive reactance, which plays a leading role in high-frequency currents. The proximity effect increases as the frequency increases and the distance between adjacent conductors becomes closer. If a magnetic core is added around the adjacent conductor, the high-frequency current will be more concentrated on the surface of the workpiece.

These two effects are the basis for realizing high-frequency metal welding. High-frequency welding uses the skin effect to concentrate the energy of the high-frequency current on the surface of the workpiece; and uses the proximity effect to control the location and range of the high-frequency current flow path. The speed of the current is very fast. It can heat and melt the edges of adjacent steel plates in a short period of time, and realize butt joints through extrusion.


Tips: In case ASTM A53 Grade B in ERW (electric resistance welded) pipe, the weld seam shall be done the heat treatment with a minimum 1000°F [540°C]. In this way the no untempered martensite remains.
In case ASTM A53 B pipe in cold expanded, then expansion should not exceed 1.5% of the required OD.

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Phenomena, Causes and Treatment Methods of Boiler Tube Damage

Date : 2021-08-30

a) The following phenomena occur when the boiler tube is damaged

1. The water level of the boiler drops rapidly, the steam pressure and the feed water pressure decrease, and there is a noticeable noise when the boiler tube bursts.
2. There is a sound of steam ejecting in the combustion chamber and flue.
3. The negative pressure in the combustion chamber changes to a positive pressure, and furnace smoke is sprayed out of the furnace door.
4. The feed water flow rate is abnormally greater than the steam flow rate.
5. The exhaust gas temperature suddenly drops.

6. Unstable combustion of the boiler or cause fire extinguishing.


\"seamless


b) Reasons when the boiler tube is damaged


1. The boiler inlet water is not deaerated, causing serious corrosion in the boiler tube.
2. The circulating water in the boiler tube vaporizes, causing a steam pocket in the tube, causing the tube wall to overheat, causing convex hulls and cracks.
3. The quality of boiler feed water does not meet the standards, and the supervision of feed water and boiler water is not enough, causing thick scale inside the pipe.
4. During maintenance or installation, the inside of the pipe was blocked by foreign objects, resulting in poor water circulation, causing local overheating of the pipe and causing the convex tube to burst.
5. The furnace temperature rises and falls too fast, causing uneven heating of some parts, causing water leakage at the nozzle.
6. It was blown away by steam leaks from adjacent damaged soda pipes.
7. The feed water temperature is too low and it is not fully mixed with the furnace fire before entering the tube. Therefore, the temperature of the tube is unevenly deformed, and additional stress occurs at the furnace nozzle, causing water leakage or annular cracks at the furnace nozzle.
8. Incorrect pressure method causes uneven heating of individual parts, causing harmful stress and causing water leakage at the weld of the furnace nozzle.
9. Periodic sewage discharge is too long or the sewage valve is not closed tightly, resulting in poor water circulation, or improper operation and operation, causing damage to the water circulation.
10. The fly ash wears severely.

c) Treatment when the boiler tube is damaged

1. The boiler tube bursts, immediately stop the operation of the boiler, and stop the boiler according to the fault. But keep the induced draft fan to extract the steam in the furnace.
2. After stopping the boiler, strengthen the boiler water supply. If the water pipe has a large crack, and the water level gauge still cannot see the water level after the water supply is strengthened, the water supply should be stopped.
3. The induced draft fan should be stopped after the steam in the furnace is basically eliminated.

4. If the boiler tube is not damaged and can maintain the normal water level, and will not cause a rapid expansion of the accident, the load should be reduced. At this time, the standby boiler should be put into operation as soon as possible. When it deteriorates, the furnace should be shut down immediately.


Permanent Steel Manufacturing Co.,Ltd specializes in the production and supply of high-quality seamless boiler tubes, including high-pressure boiler tubes, medium and low pressure boiler tubes, and seamless boiler tubes, which are widely used in industrial production, heating, power generation, etc.

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Quality Requirements for Casing Pipe

Date : 2021-09-06

The material and type of casing pipe should be selected according to the drilling structure design and engineering needs. Deep-hole core drilling has a long construction period and a large casing depth. The drill pipe string will hit and wear the casing seriously during drilling. If there is a problem with the casing string in the hole, it will cause serious accidents in the hole, or even scrap Therefore, the quality of the drilled casing string must meet the following requirements.


\"steel



1. Material requirements

The material of seamless steel pipe is generally selected according to parameters such as casing depth and quality.

When choosing the casing material, the quality of the casing string should also be considered. When the casing quality is less than 10t, ordinary low carbon steel grade can be selected; for 10-20t, steel grade DZ40~DZ50 should be selected; for ≥20t, steel grade above DZ50 should be selected. In addition, the material of the casing joint should be one level higher than the steel grade requirement of the casing body.

2. Casing bending requirements

The curvature of the casing means that the casing is curved in the length direction, expressed by the measured arc height of the maximum bend of the casing, divided into local curvature (mm/m) and full length curvature (%). The general requirements for deep hole drilling are: casing diameter ≤ Φ89mm, partial curvature should be within the range of 1mm/1.5m; casing diameter> Φ89mm, local curvature should be within the range of 1mm/1m.

3. Requirement for casing ovality and wall thickness unevenness

The difference between the maximum outside diameter and the minimum outside diameter of the casing cross section is called the ellipticity (or out of roundness). Generally, it is stipulated that the ovality of the casing does not exceed 80% of the outside diameter tolerance. The diameter of the casing is less than or equal to Φ89mm, and the ovality is controlled within 0.5mm; the diameter of the casing is more than Φ89mm, and the ovality is controlled within 1.0mm.

The unequal wall thickness of the casing cross section and the longitudinal pipe body is called wall thickness unevenness. It is generally stipulated that no more than 80% of the pipe wall thickness tolerance. The diameter of the casing is less than or equal to Φ89mm, and the unevenness of the wall thickness is controlled within 0.3mm; the diameter of the casing is> Φ89mm, and the unevenness of the wall thickness is controlled within 0.5mm.

4. Casing connection method and processing quality requirements

1) There are three ways of casing connection: direct connection, flat joint connection and coupling connection.
Under normal circumstances, when the casing mass is less than 10t, the direct connection or flat joint connection is adopted; when the casing mass is more than 10t, the coupling connection mode is adopted.

2) Casing joints and coupling materials for deep holes should be heat treated to increase their strength.
3) The thread center lines at both ends of the casing joint should be coincident, and the coaxial deviation should not be greater than 0.25mm at either end.
4) Casing, joint, and coupling thread standards mainly include geological core drilling standards and petroleum drilling standards. Petroleum pipe thread standards are often implemented in deep hole and large diameter geological core drilling.

5) The machining accuracy of casing, joint, and coupling thread must be strictly in accordance with the corresponding specifications.
6) After the casing, joints, and couplings are processed and formed, the through-hole inspection shall be carried out with a standard inner diameter gauge.
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Quality Requirements of Seamless Steel Pipes in Production

Date : 2021-09-06

Quality requirements of seamless steel pipes in production:

1. Chemical composition
The chemical composition of steel is one of the most important factors affecting the performance of seamless steel pipes, and it is also the main basis for formulating pipe rolling process parameters and steel pipe heat treatment process parameters.

a. Alloying elements: intentionally added, according to the purpose.
b. Residual elements: brought in by steelmaking, properly controlled.
c. Harmful elements: strictly control (As, Sn, Sb, Bi, Pb), gas (N, H, O)

In order to improve the uniformity of the chemical composition of the steel and the purity of the steel, reduce the non-metallic inclusions of the tube blank and improve its distribution, the external refining equipment is often used to refine the molten steel, and even the electroslag furnace is used to reshape the tube blank. Smelting and refining.


\"seamless


2. Dimensional accuracy and shape
The geometric dimensions of seamless steel pipes mainly include the outer diameter, wall thickness, ellipticity, length, curvature, pipe end face cut, bevel angle and blunt edges, and cross-sectional dimensions of special-shaped steel pipes.

a. The accuracy of the outer diameter of the steel pipe: depends on the method of sizing (reducing) the diameter, the operation of the equipment, the process system, etc.
Allowable deviation of outer diameter δ=(D-Di)/Di ×100% D: Maximum or minimum outer diameter (mm)

b. Steel pipe wall thickness accuracy: It is related to the heating quality of the tube blank, the process design parameters and adjustment parameters of each deformation process, the quality of the tool and the quality of lubrication, etc.
Allowable deviation of wall thickness: ρ=(S-Si)/Si×100% S: the maximum or minimum wall thickness on the cross section (mm)

c. Ovality of steel pipe: indicates the degree of out-of-roundness of the steel pipe.
d. Steel tube length: normal length, fixed (double) length, length tolerance.
e. Steel pipe curvature: indicates the curvature of the steel pipe: the curvature per meter of the steel pipe length and the curvature of the steel pipe full length.
f. Steel pipe end face cut slope: It indicates the degree of inclination between the steel pipe end face and the steel pipe cross section.
g. The bevel angle and blunt edge of the steel pipe end face.

3. Surface quality
The standard stipulates the requirements of \"smooth and clean surface\" of seamless steel pipes.
Common defects are: cracks, hair lines, internal folds, external folds, crushing, internal straights, external straights, separation, scars, pits, convex hulls, pits (pits), scratches (abrasions) , Inner spiral, outer spiral, blue line, concave correction, roll printing, etc., are mainly divided into two categories.

a. Dangerous defects: cracks, internal folds, external folds, crushing, delamination, scarring, dents, convex hulls, etc.
b. General defects: pits, blue lines, scratches, bruises, slight inner and outer straights, roller marks, etc.

Causes:
① Due to surface defects or internal defects of the tube blank.
② Produced in the production process, such as incorrect design of rolling process parameters, unsmooth mold surface, poor lubrication conditions, unreasonable pass design and adjustment.
③ In the process of heating rolling, heat treatment and straightening of the tube billet (steel tube), if the heating temperature is not properly controlled, the deformation is not uniform, the heating and cooling rate is unreasonable, or the straightening deformation is too large to produce excessive residual stress, then It may also cause surface cracks in the steel pipe.

4. Physical and chemical properties
Including the mechanical properties at room temperature and the mechanical properties at a certain temperature (thermal strength and low temperature properties) and corrosion resistance (such as oxidation resistance, water corrosion resistance, acid and alkali resistance, etc.). Generally, it depends on the chemical composition and structure of the steel. Performance and purity of steel and heat treatment method of steel. In some cases, the rolling temperature and degree of deformation of the steel pipe will also affect the performance of the steel pipe.

5. Process performance
Including the flaring, flattening, crimping, bending, ring drawing and welding performance of steel pipes.

6. Metallographic organization
Including the low-magnification (macro) and high-magnification (micro) of the steel pipe.

7. Special requirements

Requirements other than the standards put forward by users when using steel pipes. Such as: contract attachments, technical agreements.


As a seamless tube manufacturer, Permanent Steel Manufacturing Co.,Ltd specializes in the production and supply of seamless steel pipes: thin-wall/thick-wall seamless pipes, precision seamless pipes, small-diameter seamless pipes, providing various specifications and materials, large inventory, rich experience, and can be provided according to customer requirements Customized service.

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Performance Advantages of Seamless Steel Pipes

Date : 2021-09-13

Seamless steel pipes are made of a single piece of metal and have no seams on the surface. They are made of steel ingots or solid pipe billets through perforation, and then hot-rolled, cold-rolled or cold-rolled. Seamless steel pipe is different from other steel pipes. It has strong corrosion resistance, sturdiness and durability, and adapts to different purposes. It has strong applicability in the construction process and is not restricted by natural conditions during installation. The details are as follows :


\"seamless


1. Excellent wear resistance:
The thickness of the wear-resistant layer of the seamless pipe is 3-12mm, the hardness of the wear-resistant layer can reach HRC58-62, the wear resistance is more than 15-20 times that of ordinary steel plates, and the performance of low-alloy steel plates is more than 5-10 times. It is high-chromium cast iron. The wear resistance is more than 2-5 times, and the wear resistance is much higher than that of spray welding and thermal spraying.

2. Excellent impact performance:
The seamless steel pipe is a double-layer metal structure. The wear-resistant layer and the base material are metallurgically bonded. The bonding strength is high. It can absorb energy during impact. The wear-resistant layer will not fall. It can be used for vibration and impact. Under strong working conditions, this is beyond the reach of cast wear-resistant materials and ceramic materials.

3. Excellent temperature resistance:
Alloy carbides of seamless steel pipes have strong stability at high temperatures. Wear-resistant steel plates can be used within 500°C, and other special requirements temperature can be customized to be used under conditions within 1200°C; ceramic, polyurethane, high Wear-resistant materials such as molecular materials cannot meet such high temperature requirements.

4. Excellent connection performance:
The base material of seamless steel pipe is general Q235 steel plate, which ensures the resistance and plasticity of the wear-resistant steel plate, and provides the strength against external forces. It can be connected with other structures by various methods such as welding, plug welding, and bolt connection. The connection is strong and not easy to fall. However, there are more ways to connect than other materials.

5. Excellent processing performance:
Seamless steel pipes can be processed into different standard sizes as required, and can be processed, cold-formed, welded, twisted, etc., which are convenient to use; can be tailor-welded on-site, making repair and replacement work time-saving and convenient, and greatly reducing work intensity.

6. High sex price ratio:

The price of seamless steel pipe is slightly higher than that of general steel, but considering the product life, repair costs, spare parts costs, etc., its performance-to-price ratio is much higher than that of general steel and other steels.


As a seamless tube manufacturer, Permanent Steel Manufacturing Co.,Ltd specializes in the production and supply of seamless steel pipes: thin-wall/thick-wall seamless pipes, precision seamless pipes, small-diameter seamless pipes, providing various specifications and materials, large inventory, rich experience, and can be provided according to customer requirements Customized service.

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Packaging and Transportation Methods to Avoid Scratching the Steel Pipe

Date : 2021-09-18

When transporting all kinds of pipes, you should make preparations for packaging in advance, and perform standardized operations for transportation and loading to avoid scratches on the pipes and bear unnecessary losses.

1. Choose suitable tools for loading and unloading
Most of the pipes are used in the construction and manufacturing industries. With the continuous improvement of industry standards, the requirements for pipes are gradually increasing. There are also some polished pipes that require special attention during loading and unloading. Generally, pipes are loaded and unloaded by hoisting methods. To prevent scratches, nylon belts or wire ropes with spacers should be used for hoisting. It is strictly forbidden that the wire ropes directly contact the pipes.


\"pipe


2. Stable loading and unloading
In the process of loading and unloading the truck, you should apply force steadily, and keep steady when lifting and lowering, and don\'t shake back and forth. Shaking from side to side will cause the pipes to collide and squeeze each other, causing wear and scratches on the surface. Load and unload in order to avoid forcibly lifting the pipe below, causing impact and abrasion.

3. Can be protected separately if possible
If conditions permit, each pipe should be individually packaged and wrapped with simple spacers, which can effectively prevent mutual wear. Of course, some large pipes must be packaged separately and should be operated in accordance with relevant requirements.

4. There are requirements for strapping when packaging
The strapping work requirements before transportation are very strict. The ordinary pipes are packaged in bundles. The same type and specification pipes should be bundled, and the bundles should not be mixed to avoid loose bundles of different types of pipes and mutual damage. There are also certain restrictions on the weight of each bundle, mainly for the safety of transportation and loading.

5. Use more strapping materials as much as possible
In order to ensure safety and avoid loose bundles that cause the pipes to collide with each other, strapping straps should be used as required when strapping, and each bundle should reach a certain number, and tools such as clasps should also be used between the bundles to prevent transportation during transportation. There is looseness, falling off, and scratches on the pipe.

6. Special pipes need to be packaged in containers
Some seamless tubes and stainless steel tubes should be packaged in wooden boxes or plastic boxes that meet the standards. Before packing, the boxes should be filled with foam and insulation to avoid squeezing, and plastic sheets should be used to prevent moisture. The packing boxes may be fixed to prevent collision damage to the pipe.

7. The carriage is guaranteed to be safe
Before loading the truck, clean the truck body to ensure that there are no hard objects such as stones and iron blocks to avoid scratching the pipes. Sleepers should be padded at the bottom of the carriage, and spacers should be installed around the carriage to ensure that it is not damaged during transportation. In addition, the bundled and transported pipes should also be fixed around the carriage to avoid abrasion caused by moving back and forth.
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Seamless Steel Pipe for Bearings

Date : 2021-09-22

Bearing seamless steel pipes are also called high-carbon chromium seamless steel pipes. The carbon content Wc is about 1%, and the chromium content Wcr is 0.5%-1.65%. Bearing seamless steel tubes are divided into six types: high-carbon chromium bearing seamless steel tubes, chromium-free bearing seamless steel tubes, carburized bearing seamless steel tubes, stainless bearing seamless steel tubes, medium and high temperature bearing seamless steel tubes, and antimagnetic bearing seamless steel tubes. 


\"bearing


High-carbon chromium bearing seamless steel pipe GCr15 is the world’s largest production of bearing seamless steel pipe. The carbon content Wc is about 1%, and the chromium content Wcr is about 1.5%. Since its birth in 1901, it has basically no main components for more than 100 years. Change, with the progress of science and technology, research work continues, product quality continues to improve, accounting for more than 80% of the world\'s total production of seamless bearing steel pipes. So if there is no special description for bearing seamless steel pipe, it refers to GCr15.

Bearing seamless steel tubes are steel used to make balls, rollers and bearing rings. Bearing seamless steel pipes have high and uniform hardness and wear resistance, as well as high elastic limit. The requirements for the uniformity of the chemical composition of the bearing seamless steel pipe, the content and distribution of non-metallic inclusions, and the distribution of carbides are very strict. It is one of the most stringent steel grades in all steel production.

In order to meet the above requirements for the performance of dynamic bearings, the following basic performance requirements are proposed for bearing seamless steel pipe materials:
1) High contact fatigue strength
2) After heat treatment, it should have a high hardness or a hardness that can meet the performance requirements of the bearing
3) High wear resistance, low friction coefficient
4) High elastic limit
5) Good impact toughness and fracture toughness
6) Good dimensional stability
7) Good anti-rust performance
8) Good cold and hot processing performance

Main standards for bearing steel pipe:
ASTM A 295: wearable high-carbon bearing steel pipe
ASTM A 534: wearable and cementite bearing seamless steel pipe
JIS G 4805: high-carbon chromium bearing seamless steel pipe
DIN 17230: ball bearing steel pipe
NF A 35-565: steel product
Steel grades of bearing steel Pipe:GCr15 (52100, SUJ2, SUJ3, 100Cr6, SKF3, SKF3S), 20CrNiMo (8620H, 4118H).
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How are Small-caliber Seamless Steel Pipes Made?

Date : 2021-09-27

How are small-caliber seamless steel pipes made?

①Main production process of hot-rolled seamless steel pipe (△main inspection process):

Tube billet preparation and inspection△→tube billet heating→perforation→pipe rolling→steel pipe reheating→fixed (reduced) diameter→heat treatment△→finished pipe straightening→finishing→inspection△(non-destructive, physical and chemical, bench inspection)→into storage

②Main production process of cold-rolled (drawn) seamless steel pipe:

Tube billet preparation → pickling and lubrication → cold rolling (drawing) → heat treatment → straightening → finishing → inspection


\"hot-rolled


The production process of general seamless steel pipes can be divided into two types: cold-drawn and hot-rolled. The production process of cold-rolled seamless steel pipes is generally more complicated than that of hot rolling. In the sizing test, if the surface does not respond to cracks, the pipe must be cut by a cutting machine and cut into a blank of about one meter in length. Then enter the annealing process. Annealing should be pickled with acid liquid. When pickling, pay attention to whether there is a lot of blistering on the surface. If there is a lot of blistering, it means that the quality of the steel pipe does not meet the corresponding standards. In appearance, cold-rolled seamless steel pipes are shorter than hot-rolled seamless steel pipes. The wall thickness of cold-rolled seamless steel pipes is generally smaller than that of hot-rolled seamless steel pipes, but the surface looks brighter than thick-walled seamless steel pipes. Much rough, without too many burrs on the caliber.

The delivery state of hot-rolled seamless steel pipes is generally delivered after heat treatment in the hot-rolled state. After the quality inspection, the hot-rolled seamless steel pipe must be strictly hand-selected by the staff. After the quality inspection, the surface shall be oiled, and then followed by multiple cold drawing experiments. After the hot-rolling treatment, the piercing experiment shall be carried out. , If the perforation is too large, it must be straightened. After straightening, it is transferred by the conveyor to the flaw detector for flaw detection experiment, and finally the label is affixed, the specification is arranged, and then it is placed in the warehouse.
 

Round tube billet → heating → piercing → three-roll cross rolling, continuous rolling or extrusion → pipe removal → sizing (or reducing) → cooling → straightening → hydraulic test (or flaw detection) → marking → seamless steel pipe in storage The capillary tube is made from steel ingots or solid tube blanks through perforation, and then made by hot rolling, cold rolling or cold drawing. The specifications of seamless steel pipes are expressed in millimeters of outer diameter * wall thickness.


\"astm


The outer diameter of hot-rolled seamless pipe is generally greater than 32mm and the wall thickness is 2.5-200mm. The outer diameter of cold-rolled seamless pipe can be up to 6mm and the wall thickness can be up to 0.25mm. The outer diameter of thin-walled pipe can be up to 5mm and the wall thickness is less than 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling.

Generally, seamless steel pipes are made of high-quality carbon steels such as 10, 20, 30, 35, 45, low-alloy structural steels such as 16Mn, 5MnV, or 40Cr, 30CrMnSi, 45Mn2, 40MnB, etc., hot-rolled or cold-rolled . Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid transportation pipelines. Seamless pipes made of medium carbon steel such as 45 and 40Cr are used to manufacture mechanical parts, such as stressed parts of automobiles and tractors. Generally, seamless steel pipes must be used for strength and flattening tests. Hot-rolled steel pipes are delivered in hot-rolled state or heat-treated state; cold-rolled steel pipes are delivered in heat-treated state.
 
Generally, seamless steel pipes are made of high-quality carbon steels such as 10, 20, 30, 35, 45, low-alloy structural steels such as 16Mn, 5MnV, or 40Cr, 30CrMnSi, 45Mn2, 40MnB, etc., hot-rolled or cold-rolled . Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid transportation pipelines. Seamless pipes made of medium carbon steel such as 45 and 40Cr are used to manufacture mechanical parts, such as stressed parts of automobiles and tractors. Generally, seamless steel pipes must be used for strength and flattening tests. Hot-rolled steel pipes are delivered in hot-rolled state or heat-treated state; cold-rolled steel pipes are delivered in heat-treated state.
 

Hot rolling, as the name implies, the temperature of the rolled piece is high, so the deformation resistance is small, and a large amount of deformation can be achieved. Taking the rolling of steel plate as an example, the thickness of the continuous casting billet is generally about 230mm, and after rough rolling and finishing rolling, the final thickness is 1-20mm. At the same time, due to the small width-to-thickness ratio of the steel plate, the dimensional accuracy requirements are relatively low, and the shape problem is not prone to occur, and the crown is mainly controlled. The requirements for the structure are generally achieved through controlled rolling and controlled cooling, that is, controlling the opening temperature, final rolling temperature and coiling temperature of finishing rolling to control the microstructure and mechanical properties of the strip.


Tips: API 5L X52 seamless pipe is a steel grade of API 5L which specifies the manufacture of two product levels (PSL1 and PSL2) line pipe, X52 Line Pipe can be made seamless or welded, which are widely used as pipeline in the transportation of petroleum and natural gas.

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Common Problems and Solutions of Burr Removal in ERW Welded Pipes

Date : 2021-10-06

Common problems in the removal process of internal burrs include eccentric, deep, shallow, etc., which of them will affect the quality of weld detection and reduce the yield of welded pipes. In particular, the internal burr is deeply scraped and the wall thickness of the weld is up to If the requirements are not met, the bearing capacity is insufficient here. In severe cases, the welded pipe may burst. The methods for removing burrs in ERW welded pipes are generally divided into two types: online and offline. The on-line removal method is to use the inner burr trimming blade on the inner burr trolley on the traction rod to carry out, and use the relative movement of the tool to plan off the burrs.


\"erw


1. Internal burrs shaved biased

When the internal burrs are shaved very biased, there will be steps on the inner wall of the welded pipe at the weld, and the online flaw detection of the weld will alarm and affect the weld quality of the welded pipe. The reason for the internal burr is that the internal burr on the drawbar is scraped from the internal burr on the trolley. The center line of the blade does not coincide with the center line of the burr in the welded pipe, resulting in deviation. Through the inspection of the welded pipe opening, it can be found that the internal burr removed is obviously scraped. The internal burr blade has scratched the base material. Check the position of the tow bar, adjust the position of the tow bar to ensure that the mechanical connection of the tow bar is good, so as to ensure that the tow bar will not shake during work, which will affect the quality of the internal burr. It is also necessary to check whether the internal burr trolley on the tow bar is Place it in the correct working position and check whether the blade screws on the inner burr trolley are loose.

2. Internal burr shaved deep

When the internal burr is scraped deeply, the wall thickness of the weld will not meet the requirements, resulting in insufficient pressure-bearing capacity, and in severe cases, the pipe may burst.

Through the inspection of the physical burr, it is found that the inner burr is too deep, and part of the substrate has been scraped off. When the inner burr blade is working, its working height is relatively high to the inner wall of the welded pipe. If the height of the inner burr blade does not meet the requirements, it will cause Deep inner burr scraping or shallow scraping, at this time, you need to adjust the working height of the inner burr blade to ensure that its height is within the standard range. In addition, check the fasteners on the inner burr trolley to ensure that they are tightly fitted to avoid Loose when working.

3. Shallow shaving of internal burrs

When the inner burr is shallow, it will cause the inner burr to protrude, which will seriously hinder the transportation of oil and gas. In addition, the inner burr will seriously affect the inspection quality of the weld. The fastening screw of the burr blade to ensure that it will not deviate from the correct working position due to uneven force during work, and the fixing seat of the traction rod needs to be checked to ensure that the traction rod will not be caused by looseness during work In the process of shaving internal burrs, the traction rod is not in the correct working position due to the force.

When the internal burr is shallow, since it can no longer be removed online, it needs to be removed offline by the internal burr removal device. After the offline internal burr removal is completed, offline inspection is required to ensure the quality of the weld. In addition, if the offline inspection is not Qualified, further manual inspection of the weld is required to ensure the quality of the weld and avoid the unqualified welded pipe due to the quality of the weld.

When removing internal burrs of ERW welded pipe(astm a53 erw), there are mainly problems such as offset, deep scraping, shallow scraping, etc. Each problem will affect the weld quality of the welded pipe. Therefore, in the production process of welded pipe, it is necessary to pay attention to removing the internal burr to ensure that it is removed. The subsequent internal burr meets the standard.
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Important Enlightenment About Oil Casing Damage

Date : 2021-10-06

For decades, research on oil casing pipe damage has never stopped, and oil fields in various countries have invested huge manpower and material resources in research. People have studied the form, cause, numerical simulation, measurement method, and mechanism of casing damage from different perspectives such as petroleum geology, reservoir engineering, materials science and engineering, rock mechanics, material mechanics, geomechanics, seepage mechanics, and corrosion electrochemistry. And prevention.


\"J55


However, due to the complexity of the problem of oil casing failure, the above-mentioned studies are generally carried out for a certain oil field, block and specific well conditions. Numerical simulations are often based on finite element analysis of a small local area around a single well, and lack of analysis of the above-mentioned problems. Multi-disciplinary, large-scale overall consideration, and because many problems in the failure of oil casing seem to be more suitable for analysis by means of numerical simulation, so far, no one has summarized people’s experience and knowledge of casing failure analysis for decades. Carry out expert system processing. Therefore, the treatment of casing damage is still ineffective at present, and oilfield casing damage still occurs frequently, which has become a major problem restricting the development of oilfields.

Petroleum casing damage is commonly referred to as casing damage and casing deformation in the field of petroleum engineering. Petroleum casing failure refers to the general term for the deformation, rupture, misalignment and other damage forms of the casing when the load on the casing exceeds the bearing capacity of the casing due to factors such as engineering, geological, and production dynamic changes during the oilfield production process. In the process of oil and gas field development, especially in the middle and late stages of oil and gas field development, casing damage is a chronic disease that plagues the development of the petroleum industry in my country and the world. It is also one of the key issues affecting the development of the petroleum industry and improving its benefits.

Therefore, from a large number of complex data and processes such as oilfield geology, engineering, design, construction, production and development, and workover, it is very important to correctly identify the main reason for the failure of the oil casing as soon as possible, and to correctly determine the failure mechanism of the oil casing. important. However, the early studies and judgments on the causes and mechanisms of oil casing damage were done by experts in this field. In recent years, with the development of computer technology, the wide application of finite element methods, and the deepening of human understanding of rock mechanics, seepage mechanics, and elastoplastic mechanics, numerical simulation is increasingly used in the analysis of the causes of casing deformation. In order to analyze the failure of the casing, a method of both knowledge analysis and numerical analysis has been formed. Partial waste in any way cannot completely solve the problem of oil casing damage. However, knowledge analysis is the main method or even if numerical analysis can be used, but numerical analysis cannot solve all the problems in the field, it happens to be the world where expert systems can demonstrate their capabilities.

So far, the research on the failure of petroleum casing has basically stayed on the knowledge analysis or numerical analysis of the failure form of a single casing. No one is engaged in establishing a rapid expert system that can cover the entire oil field and deal with all the failure problems of petroleum casing. Perform unified analysis and processing. The establishment of an expert system covering the entire oil casing damage has important theoretical and practical significance for the treatment of casing damage in oilfields in my country and the world.

Analysis of oil casing damage mechanism is a complex, arduous and creative work. It is a systematic engineering involving oilfield geology, drilling engineering (drill pipe), the formulation and adjustment of overall development plans, and the adoption of production measures; prevention, delay and resolution of oil casing damage is the core. This work also has important guiding significance for the geological and engineering design of the new well construction, the adjustment of the oilfield development plan, and the formulation of production measures. It is possible to quickly build an oil casing fault detection system to provide convenience for oil casing fault monitoring.
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Four Major Processes for Heat Treatment of Oil Casing Pipe

Date : 2021-11-26

Petroleum casing pipes are steel pipes used to support the walls of oil and gas wells to ensure the normal operation of the entire oil well after drilling and completion. Each well uses several layers of casing according to different drilling depths and geological conditions. Cement is used to cement the casing after the casing is down. It is different from the tubing and drill pipe and cannot be reused. It is a one-time consumable material. Therefore, casing consumption accounts for more than 70% of all oil well pipes.


\"N80


There are roughly 4 basic processes for heat treatment of oil casing, namely annealing, normalizing, quenching and tempering, commonly known as the \"four fires\" of metal heat treatment.

1. Annealing
Annealing is to heat the workpiece to an appropriate temperature, use different holding time according to the material and workpiece size, and then slowly cool it, the purpose is to make the internal structure of the metal reach or close to the equilibrium state, obtain good process performance and use performance, or for further quenching Prepare for organization.

2. Normalizing
Normalizing is to heat the workpiece to a suitable temperature and then cool it in the air. The effect of normalizing is similar to annealing, except that the resulting structure is finer. It is often used to improve the cutting performance of materials, and sometimes used for parts that are not demanding. As the final heat treatment.

3. Quenching
Quenching is to quickly cool the workpiece in a quenching medium such as water, oil, other inorganic salts, and organic aqueous solutions after heating and holding the workpiece. After quenching, the steel parts become hard and brittle. At the same time, low-temperature quenching is lower than the conventional temperature, which reduces the stress of quenching, thereby reducing the deformation of quenching, which ensures the smooth operation of heat treatment production, and provides good raw materials for subsequent wire processing.

4. Tempering
Tempering In order to reduce the brittleness of steel parts, the quenched steel parts are kept at an appropriate temperature higher than room temperature but lower than 750°C for a long time, and then cooled. This process is called tempering.

The heat treatment process of the existing steel-grade petroleum casing pipe is poor in hardenability of the heat-treated product during processing, the mechanical properties of the steel pipe are not good enough, and the protective bending effect is not good, and it is easy to break.
The heat treatment of oil casing pipe needs to be strictly implemented. The produced oil casing has good product quality, exhibits good use value and performance during use, and can maintain high strength and toughness.
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Difference Between 304 304L and 321 Stainless Steel

Date : 2021-11-26

\"L\" stands for low carbon.
304L grade Low Carbon, typically 0.035% Max
304 grade Medium Carbon, typically 0.08% Max


304 stainless steel and 321 stainless steel belong to the 300 stainless steel series.

304 stainless steel is low carbon chromium nickel stainless and heat resisting steel somewhat superior to Type 302 in corrosion resistance.


\"304

321 stainless steel is known as stabilized grades of stainless steel, is Chromium nickel steel containing titanium. Recommended for parts fabricated by welding which cannot be subsequently annealed. Also recommended for parts to be used at temperatures between 800°F and 1850°F (427 to 816°C), have good properties resistance to intergranular corrosion. The titanium element in 321 stainless steel makes it more resistant to chromium carbide formation.

321 stainless steel is basically from 304 stainless steel. They different by a very very small addition of Titanium. The real difference is their carbon content. The higher the carbon content the greater the yield strength. 321 stainless steel has advantages in high temperature environment due to its excellent mechanical properties. Compared with 304 alloy, 321 stainless steel has better ductility and resistance to stress fracture. In addition, 304L can also be used for anti-sensitization and intergranular corrosion.


304 VS. 321304 Stainless Steel321 Stainless Steel
Features
Corrosion resistance, good toughness
Abrasion resistance, high temperature resistance, creep resistance
Grade 
0Cr18Ni9 (0Cr19Ni9)  06Cr19Ni9  S30408
X10CrNiTi189 321, S32100, TP321 SUS321
Chemical composition

C: ≤0.08, Si: ≤1.0, Mn: ≤2.0, Cr: 18.0~20.0, 

Ni: 8.0~10.5, S: ≤0.03, P: ≤0.035, N≤0.1

S: 0.030, Ni: 9.00-12.00, Cr: 17.00-19.00, Ti: 5C-0.70
Tensile strength (Mpa)
520≥520
Conditional yield strength (MPa)
205-210
≥205
Elongation (%) 
40%
≥40
Hardness
HB187 HRB90 HV200
≤187HB; ≤90HRB; ≤200HV
Density 
7.93 g/cm3 
7.93 g/cm3 
Theoretical weight
Weight (kg) = thickness (mm) * width (m) * length (m) * density valueWeight (kg) = thickness (mm) * width (m) * length (m) * density value
Uses

Tableware, cabinets, indoor pipelines, water heaters, boilers, bathtubs, 

auto parts, medical appliances, building materials, chemicals, food industry, agriculture, and ship parts.

Outdoor machines for the chemical, coal, and petroleum industries.


As can be seen from the above table, the main difference is that 304 does not contain Ti, and 321 contains Ti. Ti can prevent stainless steel from sensitizing. Generally speaking, it can improve the high temperature service life of stainless steel. 304 stainless steel plate is more suitable.


The appearance and physical properties of 304 and 321 stainless steel are very similar, except for the slight difference in chemical composition:


1) 321 stainless steel requires trace amounts of titanium (Ti) (according to the ASTM A182-2008 standard, the Ti content should not be less than 5 times the carbon (C) content, but not more than 0.7%, another note, 304 and 321 The carbon (C) content is 0.08%, and 304 does not contain titanium (Ti).
2) the requirements for nickel (Ni) content are slightly different. 304 is between 8% and 11%, while 321 is between 9% and 12%.
3) the requirements for chromium (Cr) content are different. 304 is between 18% and 20%, while 321 is between 17% and 19%.

So you can use metal material analyzer or chemical analysis method to verify the composition of these two materials and make judgments.

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MS Seamless Pipe, Mild Steel Seamless Pipe Manufacturer & Exporter

Date : 2021-11-26

MS Seamless Pipe, Mild Steel Seamless Pipe Manufacturer & Exporter


Mild Steel (MS) pipes are manufactured using low carbon (less than 0.25%) steel. As MS Pipes are made from mild steel they can easily be welded and formed in various shapes and sizes for pipelining and tubing purposes.

Permanent Steel Manufacturing Co., Ltd is a well-known MS Seamless Pipe Manufacturer, known for its precision engineering, light weight, corrosion resistance, reasonable structure, complex details, and economy. We have set an example in terms of quality and performance by manufacturing and supplying MS seamless pipes. MS seamless pipes are due to their high strength and pressure-bearing capacity.It is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile transmission shafts, bicycle frames, and steel scaffolding used in construction.



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Features of Mild steel tubing:
1. Mild steel tubing with seamless is a carbon steel with a carbon content of less than 0.25%. It is also called mild steel because of its low strength, low hardness and softness.
2. The annealed structure of mild steel tubing with seamless is ferrite and a small amount of pearlite, which has low strength and hardness, and good plasticity and toughness.
3. Mild steel tubing with seamless has good cold formability and can be cold formed by crimping, bending, stamping, etc.
4. Mild steel tubing with seamless has good weldability. Easy to accept a variety of processing such as forging, welding and cutting.


Mild steel Seamless pipe is a capillary tube made of steel ingots or solid tube billets through perforation, and then hot-rolled, cold-rolled or cold-rolled. Seamless carbon steel pipe has an important position in my country\'s steel pipe industry.


Manufacturing process:

The raw material of the seamless mild steel pipe is a round tube blank. The round tube blank is cut by a cutting machine into a billet with a length of about 1 meter, and is sent to the furnace for heating via a conveyor belt. The billet is fed into the furnace and heated at a temperature of approximately 1200 degrees Celsius. The fuel is hydrogen or acetylene. The temperature control in the furnace is a key issue.

After the round tube billet comes out of the furnace, it is pierced by a pressure piercing machine. Generally, the more common piercing machine is the tapered roller piercing machine. This type of piercing machine has high production efficiency, good product quality, large perforation diameter expansion, and can wear a variety of steel types.

After piercing, the round tube billet is successively cross-rolled, continuous rolled or extruded by three rolls. After squeezing, take off the tube and calibrate. The sizing machine uses a tapered drill bit to rotate at a high speed into the steel blank to punch holes to form a steel pipe. The inner diameter of the steel pipe is determined by the length of the outer diameter of the drill bit of the sizing machine.

After the steel pipe is sized, it enters the cooling tower and is cooled by spraying water. After the steel pipe is cooled, it will be straightened. After straightening, the steel pipe is sent to the metal flaw detector (or hydraulic test) by the conveyor belt for internal flaw detection. If there are cracks, bubbles, etc. inside the steel pipe, it will be detected.

After the quality inspection of steel pipes, strict manual selection is required. After the quality inspection of the steel pipe, paint the serial number, specification, production batch number, etc. with paint. It is hoisted into the warehouse by a crane.

Heat Treatment:

Low carbon steel tubing with seamless(ms seamless pipe) has a large tendency to aging, both quenching and aging tendencies, as well as deformation and aging tendencies. When the steel is cooled from high temperature, the carbon and nitrogen in the ferrite are supersaturated, and the carbon and nitrogen in the iron can be slowly formed at normal temperature, so that the strength and hardness of the steel are improved, and the ductility and toughness are lowered. This phenomenon is called quenching aging. Low carbon steel tubing with seamless will have an aging effect even if it is not quenched. The deformation of low carbon steel tubing with seamless produces a large number of dislocations. The carbon and nitrogen atoms in the ferrite interact elastically with dislocations, and carbon and nitrogen atoms gather around the dislocation lines. This combination of carbon and nitrogen atoms and dislocation lines is called the Cochrane gas mass (Kelly gas mass). It increases the strength and hardness of steel and reduces the ductility and toughness. This phenomenon is called deformation aging. Deformation aging is more harmful to the ductility and toughness of low carbon steel than quenching aging. 

There are obvious upper and lower yield points on the tensile curve of low carbon steel. From the upper yield point until the end of the yield extension, a surface wrinkle band formed on the surface of the sample due to uneven deformation is called the Rydes belt. Many stamping parts are often scrapped. There are two ways to prevent it. A high pre-deformation method, the pre-deformed steel is placed for a period of time and the Rudes belt is also produced when stamping, so the pre-deformed steel should not be placed too long before stamping. The other is to add aluminum or titanium to the steel to form a stable compound with nitrogen to prevent deformation aging caused by the formation of Kodak air mass.

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Differences between Carbon Steel and Stainless Steel

Date : 2021-12-10

Carbon Steel

Mainly refers to the steel whose mechanical properties depend on the carbon content in the steel, and generally do not add a large amount of alloying elements. Sometimes it is also called plain carbon steel or carbon steel, which refers to iron-carbon alloys with a carbon content of less than 2% WC.

In addition to carbon, carbon steel generally contains a small amount of silicon, manganese, sulfur, and phosphorus. The higher the carbon content of carbon steel, the greater the hardness and the higher the strength, but the lower the plasticity.

Classification of carbon steel:

1. Carbon steel can be divided into three types: carbon structural steel, carbon tool steel and free-cutting structural steel according to its purpose. Carbon structural steel is further divided into two types: architectural structural steel and machine-manufactured structural steel;
2. According to the smelting method, it can be divided into open hearth steel, converter steel and electric furnace steel;
3. According to the deoxidation method, it can be divided into boiling steel (F), killed steel (Z), semi-killed steel (b) and special killed steel (TZ);
4. Carbon steel can be divided into low carbon steel (WC ≤ 0.25%), medium carbon steel (WC 0.25%-0.6%) and high carbon steel (WC>0.6%) according to the carbon content;

5. According to phosphorus and sulfur content, carbon steel can be divided into ordinary carbon steel (higher phosphorus and sulfur), high-quality carbon steel (lower phosphorus and sulfur) and high-quality high-quality steel (lower phosphorus and sulfur) ) And super high-quality steel.


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Stainless Steel

Stainless acid-resistant steel is referred to as stainless steel. It is composed of two parts: stainless steel and acid-resistant steel. In short, steel that can resist atmospheric corrosion is called stainless steel, and steel that can resist chemical media corrosion is called acid-resistant steel. Rusty steel is a high-alloy steel with more than 60% iron as the matrix and adding alloying elements such as chromium, nickel, and molybdenum.

When the chromium content in the steel exceeds 12%, the steel is not easy to corrode and rust in the air and dilute nitric acid. The reason is that chromium can form a very tight chromium oxide film on the steel surface, which effectively protects the steel from corrosion. The chromium content in stainless steel generally exceeds 14%, but stainless steel is not absolutely rust-free. In coastal areas or some places with serious air pollution, when the chlorine ion content in the air is high, the stainless steel surface exposed to the atmosphere may have some rust spots, but these rust spots are limited to the surface and will not erode the internal matrix of the stainless steel. 

Generally speaking, steel with a content of WCr greater than 12% has the characteristics of stainless steel. According to the microstructure after heat treatment, stainless steel can be divided into five categories: ferritic stainless steel, martensitic stainless steel, and austenitic stainless steel. , Austenitic-ferritic stainless steel and precipitation carbide stainless steel.

Stainless steel is usually divided into:

1. Ferritic stainless steel. Containing 12% to 30% chromium. Its corrosion resistance, toughness and weldability increase with the increase of chromium content, and its resistance to chloride stress corrosion is better than other types of stainless steel.
2. Austenitic stainless steel. The chromium content is more than 18%, and it also contains about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. Good overall performance, resistant to corrosion by various media.
3. Austenitic-ferritic duplex stainless steel. It has the advantages of austenitic and ferritic stainless steel, and has superplasticity.
4. Martensitic stainless steel. High strength, but poor plasticity and weldability.

Differences between carbon steel and stainless steel:

1. Different colors: stainless steel contains more chromium and nickel metals, and the exterior color is mostly bright silver. Carbon steel is mainly carbon and iron alloy, and other metal elements are relatively small. The main color of the outer surface is the color of iron, and the color will be much darker.
2. Different textures: stainless steel contains many other metal elements and has a smooth surface, while carbon steel contains iron and carbon and has the essence of iron, but the surface is not as smooth as stainless steel.

3. Different magnetism: the surface of carbon steel is magnetized and can be attracted by magnets. Stainless steel has no magnetism under normal conditions and will not be attracted by magnets.
4. Different carbon elements: Carbon steel mainly refers to the steel whose mechanical properties depend on the carbon content of steel, and generally do not add a large amount of alloy metal elements, in which the carbon content WC is less than 2%. In order to maintain corrosion resistance, stainless steel contains carbon content. Both are low, and the maximum does not exceed 1.2%.

5. Different alloy content: Carbon steel contains few alloying elements, only a small amount of silicon, manganese, sulfur, and phosphorus. Stainless steel contains a lot of gold elements, and the main chromium and nickel elements exceed 12%.
6. Different corrosion resistance: carbon steel contains less alloying elements and has weak corrosion resistance, while stainless steel contains more chromium-nickel metal, which has strong corrosion resistance.
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Carbon Steel vs Stainless Steel

Date : 2021-12-14

Carbon Steel 

Mainly refers to the steel whose mechanical properties depend on the carbon content in the steel, and generally do not add a large amount of alloying elements. Sometimes it is also called plain carbon steel or carbon steel, which refers to iron-carbon alloys with a carbon content of less than 2% WC.

In addition to carbon, carbon steel generally contains a small amount of silicon, manganese, sulfur, and phosphorus. The higher the carbon content of carbon steel, the greater the hardness and the higher the strength, but the lower the plasticity.

Classification of carbon steel:

1. Carbon steel can be divided into three types: carbon structural steel, carbon tool steel and free-cutting structural steel according to its purpose. Carbon structural steel is further divided into two types: architectural structural steel and machine-manufactured structural steel;
2. According to the smelting method, it can be divided into open hearth steel, converter steel and electric furnace steel;
3. According to the deoxidation method, it can be divided into boiling steel (F), killed steel (Z), semi-killed steel (b) and special killed steel (TZ);
4. Carbon steel can be divided into low carbon steel (WC ≤ 0.25%), medium carbon steel (WC 0.25%-0.6%) and high carbon steel (WC>0.6%) according to the carbon content;

5. According to phosphorus and sulfur content, carbon steel can be divided into ordinary carbon steel (higher phosphorus and sulfur), high-quality carbon steel (lower phosphorus and sulfur) and high-quality high-quality steel (lower phosphorus and sulfur) ) And super high-quality steel.


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Stainless Steel 
Stainless acid-resistant steel is referred to as stainless steel. It is composed of two parts: stainless steel and acid-resistant steel. In short, steel that can resist atmospheric corrosion is called stainless steel, and steel that can resist chemical media corrosion is called acid-resistant steel. Rusty steel is a high-alloy steel with more than 60% iron as the matrix and adding alloying elements such as chromium, nickel, and molybdenum.


When the chromium content in the steel exceeds 12%, the steel is not easy to corrode and rust in the air and dilute nitric acid. The reason is that chromium can form a very tight chromium oxide film on the steel surface, which effectively protects the steel from corrosion. The chromium content in stainless steel generally exceeds 14%, but stainless steel is not absolutely rust-free. In coastal areas or some places with serious air pollution, when the chlorine ion content in the air is high, the stainless steel surface exposed to the atmosphere may have some rust spots, but these rust spots are limited to the surface and will not erode the internal matrix of the stainless steel. 

Generally speaking, steel with a content of WCr greater than 12% has the characteristics of stainless steel. According to the microstructure after heat treatment, stainless steel can be divided into five categories: ferritic stainless steel, martensitic stainless steel, and austenitic stainless steel. , Austenitic-ferritic stainless steel and precipitation carbide stainless steel.

Stainless steel is usually divided into:

1. Ferritic stainless steel. Containing 12% to 30% chromium. Its corrosion resistance, toughness and weldability increase with the increase of chromium content, and its resistance to chloride stress corrosion is better than other types of stainless steel.
2. Austenitic stainless steel. The chromium content is more than 18%, and it also contains about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. Good overall performance, resistant to corrosion by various media.
3. Austenitic-ferritic duplex stainless steel. It has the advantages of austenitic and ferritic stainless steel, and has superplasticity.
4. Martensitic stainless steel. High strength, but poor plasticity and weldability.

Differences between carbon steel and stainless steel:

1. Different colors: stainless steel contains more chromium and nickel metals, and the exterior color is mostly bright silver. Carbon steel is mainly carbon and iron alloy, and other metal elements are relatively small. The main color of the outer surface is the color of iron, and the color will be much darker.
2. Different textures: stainless steel contains many other metal elements and has a smooth surface, while carbon steel contains iron and carbon and has the essence of iron, but the surface is not as smooth as stainless steel.

3. Different magnetism: the surface of carbon steel is magnetized and can be attracted by magnets. Stainless steel has no magnetism under normal conditions and will not be attracted by magnets.
4. Different carbon elements: Carbon steel mainly refers to the steel whose mechanical properties depend on the carbon content of steel, and generally do not add a large amount of alloy metal elements, in which the carbon content WC is less than 2%. In order to maintain corrosion resistance, stainless steel contains carbon content. Both are low, and the maximum does not exceed 1.2%.

5. Different alloy content: Carbon steel contains few alloying elements, only a small amount of silicon, manganese, sulfur, and phosphorus. Stainless steel contains a lot of gold elements, and the main chromium and nickel elements exceed 12%.
6. Different corrosion resistance: carbon steel contains less alloying elements and has weak corrosion resistance, while stainless steel contains more chromium-nickel metal, which has strong corrosion resistance.

Permanent Steel Manufacturing Co.,Ltd specializes in the production and supply of seamless steel pipes, welded steel pipes, hollow sections, stainless steel pipes, pipe fittings, etc., with more than ten years of production experience. (Fluid pipe/Boiler pipe/Fire pipe/Line pipe/Structural pipe)

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Causes of Defects in Hot-rolled Seamless Steel Pipes

Date : 2021-12-14

Hot-rolled seamless steel pipe is a round, square, and rectangular steel with a hollow section and no joints on the periphery. When the bending and torsion strength is the same, the weight is lighter. It is an economical cross-section steel. What defects are prone to appear in the production process of steel pipes? Let\'s explain it for everyone.

1) Cracks (also known as cracks). Features: The inner and outer surfaces of seamless steel pipes are linear or spiral cracks, and some are mesh-shaped and both ends and bottom of the cracks are sharp.

1. Poor steel quality, with subcutaneous pores and subcutaneous inclusions.
2. Improper heating of the tube billet.

3. The deformation pressure is too large.


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2) Hairline, features: continuous or discontinuous hair-like fine lines appear on the outer surface of the seamless steel pipe. Most of the spiral spiral direction is opposite to the direction of rotation of the punch, with a large pitch, and some are similar to a straight line.

1. Poor steel, with subcutaneous pores and subcutaneous inclusions.
2. The surface of the tube blank is incompletely cleaned.

3) Inward fold (commonly known as inner fold), features: straight or spiral zigzag defects on the inner surface of the steel pipe. For high-alloy steel pipes, such defects are irregular blocks and distributed at the entrance. If the fold is caused by centering, it is usually half a circle to a circle, and it is on the head.

1. The amount of pressing down the front of the head is too large.
2. Serious head wear.
3. During the piercing process, the metal in the central part of the blank bears strong alternating stress, so the inner wall of the waste tube is prone to inward bending during rolling.
4. The inward folding at the entrance of the high-alloy steel pipe is caused by uneven force on the roll during piercing.

4) Outer folding, characteristic: the outer surface of the seamless steel pipe is spirally folded, and the spiral direction is opposite to the spiral direction of the waste pipe on the punching machine, and the pitch is relatively large.

1. Defects such as cracks or ears remain on the surface of the tube blank.
2. Poor steel quality, inclusions or serious looseness.

5) Rolling and folding, characteristics: there are regular folding defects on the outer surface of the seamless steel pipe.

It is mainly caused by damage to the roll of the piercing machine or the roll of the tube mill.

6) Bending, characteristics: during rolling, the metal enters the gap between the rolls or the tube loses its stability, causing it to form twists and turns. After sizing, the surface of the steel tube shows local convex and concave wrinkles.

1. The outlet pipe diameter of the equalizing machine is larger than the hole type of the fixed and reducing machine.
2. Incorrect adjustment, misalignment of rolls, inconsistent center lines, etc.
3. The sizing frame is installed upside down.

7) Straight inward folding. Features: The inner surface of the seamless steel pipe is symmetrical or a single straight line folding, distributed over the entire length or part of the steel pipe.

1. The head is severely worn or stuck to metal.
2. The outer diameter of the capillary tube is larger than the width of the grooved hole, the inner diameter is too large or the tube wall is too thin.
3. Unreasonable distribution of reduction of piercing machine and tube rolling machine.
4. Before the second pass of rolling, the 90° overturning was not completed.

The above is the content of the defects in the production process of hot-rolled seamless steel pipes for everyone. I hope it will be helpful to everyone. If you want to know about other things, you can come to consult us: info@permanentsteel.com
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How to Prevent Surface Decarburization of Seamless Pipe Products?

Date : 2021-12-21

The carbon element in the seamless steel tube (smls) has a great influence on its own performance, so when the seamless tube is decarburized, its service life will be greatly reduced, and if the surface of the seamless tube is decarburized If it is not cleaned, the hardness and wear resistance of the surface layer of the seamless pipe will be reduced, and during quenching, cracks will be formed on the surface of the workpiece due to the different volume changes of the inner and outer layers. Therefore, how to prevent the surface decarburization of seamless pipes is a problem that should be paid attention to in the production process.


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The key to solving the problem of surface decarburization lies in the heat treatment process. Since the decarburization and the oxidation of the steel wire are carried out at the same time, the purpose of improving decarburization can be achieved as long as the non-tin seamless pipe is kept in contact with air as little as possible during the heat treatment process. The production process is: the first molten lead tank is used to austenitize the steel wire. The lead liquid is heated to 871℃ in advance, the steel wire is passed in the lead liquid to achieve austenitization, and then enters the oil tank for quenching, and then enters the second Two molten lead tanks are tempered (482°C). Since the steel wire is not in contact with air in the molten lead, decarburization is effectively avoided. The main problem that needs to be solved with this process is how to prevent lead dust pollution.

The atmosphere that causes decarburization on the surface of seamless pipes is mainly oxidizing gases such as oxygen, water vapor, and carbon dioxide. When these oxidizing gases contact the surface of the heated steel wire, oxidation and decarburization occur simultaneously; because the solid-solution carbon in the iron has a relatively large affinity for these gases, the carbon on the surface is removed first. The above-mentioned gases are generally brought in from outside the furnace; the iron oxide scale, rust on the surface of the seamless pipe and the residues on the surface of the steel wire after cold drawing will also decompose after being heated in the furnace and react to generate some oxidizing gases. We can purposely control the atmosphere in the furnace to make it in a reducing state, which can effectively avoid surface decarburization. For example, controlling the ratio of carbon dioxide to carbon monoxide in the furnace, at the equilibrium point, neither oxidation nor decarburization; when the ratio of carbon dioxide exceeds the equilibrium point, oxidation and decarburization will occur; when the ratio is below the equilibrium point, oxidation and decarburization will not occur . The specific value of the equilibrium point should be calculated based on the carbon content and temperature of the iron.

In addition, it is also an effective measure to inject neutral protective nitrogen into the furnace from the seamless tube. At the same time, it can maintain the positive pressure in the furnace, prevent air infiltration, and reduce or avoid decarburization of steel parts.


Go here to learn “How to Prevent Decarburization of Spiral Steel Pipe?”

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Steel Normalizing vs. Annealing

Date : 2021-12-28

Normalizing and annealing are two heat treatment processes that can be used to treat steel products.

Normalizing, also known as normalization, is a metal heat treatment process in which the workpiece is heated to 30~50°C above Ac3 or Accm, and after holding it for a period of time, it is removed from the furnace in the air or cooled by spraying water, spraying or blowing. Its purpose is to make the grain refinement and carbide distribution uniform.


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Annealing: A metal heat treatment process in which steel is slowly heated to a certain temperature, kept for sufficient time, and then cooled at an appropriate speed (usually slow cooling, sometimes controlled cooling). The purpose is to soften materials or workpieces processed by casting, forging, rolling, welding or cutting, improve plasticity and toughness, homogenize chemical composition, remove residual stress, or obtain expected physical properties. There are many annealing processes depending on the purpose, such as recrystallization annealing, isothermal annealing, homogenization annealing, spheroidizing annealing, stress relief annealing, recrystallization annealing, stabilization annealing, magnetic field annealing, etc.

The main difference between annealing and normalizing:

1. The cooling rate of normalizing is slightly faster than annealing, and the degree of undercooling is greater.
2. The structure obtained after normalizing is finer, and the strength and hardness are higher than that of annealing.
 
The choice of annealing and normalizing:

1. For low carbon steel with carbon content <0.25%, normalizing is usually used instead of annealing. Because the faster cooling rate can prevent low-carbon steel from precipitating free tertiary cementite along the grain boundary, thereby improving the cold deformation performance of stamping parts; normalizing can improve the hardness of steel and the cutting performance of low-carbon steel; In the heat treatment process, normalizing can be used to refine the grains and improve the strength of low carbon steel.

2. Medium-carbon steel with carbon content between 0.25 and 0.5% can also be normalized instead of annealing. Although the hardness of medium-carbon steel with carbon content close to the upper limit is higher after normalizing, it can still be cut and the cost of normalizing Low and high productivity.
 
3. Steel with carbon content between 0.5 and 0.75%, due to its high carbon content, the hardness after normalizing is significantly higher than that of annealing, and it is difficult to perform cutting. Therefore, full annealing is generally used to reduce the hardness and improve cutting. Processability.
  

4. High-carbon steel or tool steel with carbon content> 0.75% generally adopts spheroidizing annealing as a preliminary heat treatment. If there is a network of secondary cementite, it should be normalized first. Annealing is a heat treatment process in which the workpiece is heated to an appropriate temperature, kept for a certain period of time, and then slowly cooled. Slow cooling is the main feature of annealing. Annealed parts are generally cooled to below 550°C in the furnace and air-cooled out of the furnace. Annealing is a very widely used heat treatment. In the manufacturing process of molds or machine parts, it is often arranged as a preliminary heat treatment after forging and welding and before cutting (rough) processing. It is used to eliminate some defects caused by the previous process and prepare for the subsequent process.


Go here to learn “5 Heat Treatment Processes for Seamless Steel Pipes

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Precautions for Seamless Line Pipe Production Process

Date : 2022-01-05

Precautions for seamless line pipe production process:


1. Raw material inspection and inspection
The raw material manufacturer\'s product quality certificate, the raw material is sampled in batches, and the steel pipe manufacturer will conduct various inspections and issue an inspection report.

2. Hydrostatic pressure test

Each steel pipe shall be subjected to hydrostatic pressure test without leakage, and the test pressure shall be at least not lower than the requirements in API 5L. The test pressure holding time for seamless steel pipes of various sizes shall be no less than 5 seconds. In order to ensure that each steel pipe can reach the required test pressure, each testing machine should be equipped with a recorder to record the test pressure and holding time of each steel pipe. If there is a representative of the purchaser in the factory for inspection, these records or charts should be available for inspection by the inspector of the purchaser. The test pressure test device is checked every 4 months. The storage of verification records shall comply with the provisions of the API 5L standard.


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3. Non-destructive testing
For all seamless steel pipes, non-destructive inspection should be carried out in accordance with the provisions of the API 5L standard.

4. Tensile test
A complete tensile test should include the determination of yield strength, ultimate tensile strength and elongation.

3. Non-destructive testing
For all seamless steel pipes, non-destructive inspection should be carried out in accordance with the provisions of the API 5L stand

4. Tensile test
A complete tensile test should include the determination of yield strength, ultimate tensile strength and elongation.

5. Charpy impact test
Charpy impact test is not required for PSL1 products;
Charpy impact test of PSL2 is sampling test according to API 5L standard.

6. Appearance and surface inspection
There should be no cracks, folds, folds, scars and delamination on the inner and outer surfaces of the steel pipe, and these defects should be completely removed. The cleaning depth should not exceed the negative deviation of the nominal wall thickness, and the actual wall thickness at the cleaning site should not be less than the minimum allowable wall thickness deviation.

On the inner and outer surface of the steel pipe, the allowable depth of the straight line is as follows:
Cold drawn steel pipe: not more than 4% of the wall thickness, and the maximum depth is 0.3mm;
Hot-rolled steel pipe: not more than 5% of the wall thickness, and the maximum depth is 0.5mm.

Other local defects that do not exceed the negative deviation of the wall thickness are allowed to exist.


Tips:API seamless pipe is a steel pipe that belongs to the American petroleum standard. The steel pipe has a hollow section and is used as a pipeline for transporting fluids. For example, steel pipes for transporting oil, natural gas, gas, and water are used to make ring parts, which can improve the utilization rate of materials and simplify the manufacturing process. Saving materials and processing man-hours, such as rolling bearing rings, jack sleeves, etc., has been widely used in seamless steel pipe manufacturing.

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How to Ensure the Quality of ERW Welded Pipe in Production?

Date : 2022-07-15

How to reduce the wear of ERW pipes in production and ensure the quality of welded pipes?

From the analysis data of ERW welded pipe scrap, it can be seen that the roll adjustment process plays a very important role in the production of welded pipes. That is to say, in the production process, if the rolls are damaged or severely worn, part of the rolls should be replaced in time in the unit, or a certain type of welded pipe should be continuously and fully produced, and the entire set of rolls should be replaced.

When replacing the welded steel pipe, it is necessary to adjust the rollers accordingly to ensure the quality of the welded pipe. On the contrary, if the rolls are not adjusted properly, it is likely to cause defects such as twisting, lap welding, edge fluctuations, indentations, scratches and even large ovality on the surface of the welded pipe and the pipe body.


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The following introduces the operation method of adjusting the roll that should be mastered when changing the roll.

In general, ERW pipe specifications should be changed and the complete set of rolls replaced. The steps of adjusting the roller type are: first, pull the steel wire at the inlet and outlet of the unit out of the center line and adjust it so that the hole pattern of each frame is on the center line, and weld the steel pipe manufacturer to make the forming line meet the technical requirements.

In order to ensure the welding quality of ERW welded pipe, the forming roll, guide roll, extrusion roll and sizing roll need to be adjusted once after replacing the rolls as required, and then focus on adjusting the closed-cell type, guide roll and extrusion roll. The function of the guide roller is to control the welding seam direction and bottom line height of the welded pipe, reduce the edge extension, control the rebound of the edge of the tube blank, and ensure that the welding seam entering the extrusion roller is straight and free from distortion.

In short, in the process of ERW welded pipe welding, when the welding machine is running at a slow speed, the welded pipe workers must pay close attention to the rotation of the rollers in various parts of the welded pipe, and adjust the rollers at any time to ensure that the welding quality and process dimensions of the welded pipe meet the specifications.
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