Seamless steel pipe production process
The production methods of seamless steel pipes are roughly divided into cross-rolling method (Mennesmann method) and extrusion method. The cross-rolling method (Mennesmann method) is to first pierce the tube blank with a cross-rolling roller, and then extend it with a rolling mill. This method has a fast production speed, but has high requirements on the workability of the tube blank, and is mainly suitable for the production of carbon steel and low-alloy steel pipes.
The extrusion method is to use a piercing machine to pierce a tube blank or a steel ingot, and then use an extruder to extrude into a steel tube. This method is less efficient than the cross-rolling method and is suitable for the production of high-strength alloy steel tubes.
Both the cross-rolling method and the extrusion method must first heat the tube billet or steel ingot, and the produced steel tube is called a hot-rolled tube. Steel pipes produced by hot working methods can sometimes be cold worked as needed. There are two methods of cold working: one is the cold drawing method, which is to draw the steel pipe through a pipe drawing die to make the steel tube gradually thinner and elongated; the other method is the cold rolling method, which is the invention of the Mennesmann brothers The hot rolling mill is used in cold working methods. The cold processing of seamless steel pipes can improve the dimensional accuracy and processing finish of the steel pipe, and improve the mechanical properties of the material.
Production process of seamless steel pipe (hot rolled steel pipe)
The seamlessness of steel pipes is mainly accomplished by tension reduction, which is a continuous rolling process of hollow base material without mandrel. Under the condition of ensuring the welding quality of the mother pipe, the welded pipe tension reducing process is to heat the welded pipe as a whole to above 950 degrees Celsius, and then roll it into various outer diameters and walls by a tension reducer (the tension reducer has 24 passes) For thick finished pipes, the hot-rolled steel pipes produced by this process are essentially different from ordinary high-frequency welded pipes. After being heated by the heating furnace, the metallographic structure and mechanical properties of the weld seam and the parent body can be completely consistent. In addition, through multiple passes The secondary tension reducer rolling and automatic control make the dimensional accuracy of the steel pipe (especially the roundness and wall thickness accuracy of the pipe body) better than similar seamless pipes. In the fluid pipes produced in developed countries in the world, a large number of welded pipe seamless technology has been adopted in boiler pipes. With the development of society, the situation of domestic hot-rolled welded pipes gradually replacing seamless pipes has taken shape.