Difference Between 304 304L and 321 Stainless Steel
"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.
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. 321 | 304 Stainless Steel | 321 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 value | Weight (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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