316 vs 321 Stainless Steel: What's the Difference?
316 vs 321 Stainless Steel: What's the Difference?
The main difference between 316 and 321 stainless steel lies in their key additives: 316 contains molybdenum, providing excellent resistance to chloride/acid corrosion (suitable for marine and chemical environments); while 321 contains titanium, offering higher high-temperature stability and preventing intergranular corrosion in welded parts (suitable for aerospace and exhaust systems). For harsh, humid/chemical environments, choose 316; for extreme high-temperature applications, choose 321.
What grade is equivalent to 321 stainless steel?
304 grade
321 stainless steel in the annealed state is equivalent to 304 grade. If welded parts made of these grades are not post-weld annealed, or if the application temperature range is between 425-9000℃, 321 stainless steel exhibits superior corrosion resistance.
321 Stainless Steel
321 stainless steel is a titanium-containing austenitic chromium-nickel alloy. Compared to most stainless steels, this alloy has superior corrosion resistance. Furthermore, it exhibits superior strength at high temperatures compared to other stainless steels. Therefore, 321 stainless steel is ideal for high-temperature applications such as heat exchangers, accumulators, and furnaces.
316 Stainless Steel
316 stainless steel is a molybdenum-containing, low-carbon austenitic chromium-nickel alloy. Compared to most stainless steels, this alloy has superior corrosion resistance and also exhibits superior strength at high temperatures. Its molybdenum content also gives it excellent resistance to pitting corrosion in chlorinated environments, making it ideal for highly corrosive environments such as food processing plants or medical facilities.
The Equivalents of 321 and 316 Stainless Steel
| GB/T | 321 | 316 |
|---|---|---|
| ASTM/UNS | 321 / S32100 | 316 / S31600 |
| EN | X6CrNiTi18-10 (1.4541) | X5CrNiMo17-12-2 (1.4401) |
| JIS | SUS 321 | SUS 316 |
| GOST | 08Х18Н10Т | 03Х17Н14М3 |
Chemical Composition of 321 vs 316 Stainless Steel
| Element | Grade 316 Stainless Steel | Grade 321 Stainless Steel |
|---|---|---|
| C | 0.08 max | 0.08 max |
| Mn | 2.00 max | 2.00 max |
| Si | 0.75 max | 0.75 max |
| P | 0.045 max | 0.045 max |
| S | 0.030 max | 0.030 max |
| Cr | 16.00 – 18.00 | 17.00 – 19.00 |
| Ni | 10.00 – 14.00 | 9.00 – 12.00 |
| Mo | 2.00 – 3.00 | – |
| Ti | – | 5 * C – 0.70 |
Physical Properties of 321 vs 316 Stainless Steel
| Property | Grade 316 | Grade 321 |
|---|---|---|
| Density (g/cm³) | 7.98 | 7.92 |
| Melting Point (°C) | 1398 – 1420 | 1398 – 1420 |
| Specific Heat (J/kg·K) | 500 | 500 |
| Thermal Conductivity (W/m·K) | 16.2 | 16.3 |
| Electrical Resistivity (µΩ·m) | 740 | 720 |
| Modulus of Elasticity (GPa) | 193 | 193 |
| Poisson's Ratio | 0.3 | 0.3 |
| Thermal Expansion (10^-6/K) | 16.5 – 16.7 | 16.5 – 16.9 |
Comparison of Corrosion Resistance of 316 and 321 Stainless Steel
316 Stainless Steel: 316 stainless steel has very high corrosion resistance.
321 Stainless Steel: It has good corrosion resistance in the intergranular state, but its corrosion resistance is poor in high-salt or acidic environments.
Heat resistance of 316 and 321 stainless steel
316 stainless steel: Can withstand temperatures up to 870 degrees Celsius, but not for extended periods.
321 stainless steel: Suitable for continuous exposure to high-temperature environments ranging from 870 to 925 degrees Celsius.
Gnee Steel also supplies custom stainless steel 316 products in various sizes and specifications. Please send us your drawings for a quote!