SS 321 vs SS 316 difference in composition & properties.
SS 316 contains molybdenum (2–3%); SS 321 has no minimum for it. Density: SS 321 7.92 g/cm³, SS 316 7.98 g/cm³.
Key differences between SS 321 and SS 316
- SS 316 contains molybdenum (2–3%); SS 321 has no minimum for it.
- Density: SS 321 7.92 g/cm³, SS 316 7.98 g/cm³.
SS 321 vs SS 316 chemical composition (weight %)
| Element | SS 321 | SS 316 |
|---|---|---|
| C | ≤0.08 | ≤0.08 |
| Si | ≤0.75 | ≤0.75 |
| Mn | ≤2 | ≤2 |
| P | ≤0.045 | ≤0.045 |
| S | ≤0.03 | ≤0.03 |
| Cr | 17–19 | 16–18 |
| Ni | 9–12 | 10–14 |
| N | ≤0.1 | ≤0.1 |
| Ti | ≤0.7 | – |
| Mo | – | 2–3 |
Mechanical properties, equivalents and uses
| Property | SS 321 | SS 316 |
|---|---|---|
| Family | Austenitic stainless | Austenitic stainless |
| Tensile strength, MPa | ≥515 | ≥515 |
| Yield strength, MPa | ≥205 | ≥205 |
| Elongation, % | ≥40 | ≥40 |
| Hardness | ≤217 HB | ≤217 HB |
| Density, g/cm³ | 7.92 | 7.98 |
| UNS | S32100 | S31600 |
| EN | X6CrNiTi18-10 | X5CrNiMo17-12-2 |
| W.Nr | 1.4541 | 1.4401 |
| JIS | SUS321 | SUS316 |
| IS (India) | X04Cr18Ni10Ti (IS 6911) | X04Cr17Ni12Mo2 (IS 6911) |
| AISI / ASTM | AISI 321 | AISI 316 |
| Typical uses | Exhausts, bellows, hot refinery lines | Chemical, marine, pharma, chloride service |
Mechanical values: Annealed plate, sheet, strip (ASTM A240 / ASME SA240). Limits vary by standard and product form; confirm against your purchase specification.
Frequently asked questions
What is the difference between SS 321 and SS 316?
SS 316 contains molybdenum (2–3%); SS 321 has no minimum for it. Density: SS 321 7.92 g/cm³, SS 316 7.98 g/cm³.
Where are SS 321 and SS 316 used?
SS 321: Exhausts, bellows, hot refinery lines. SS 316: Chemical, marine, pharma, chloride service.
Can SS 316 replace SS 321?
Only if the purchase specification allows it. Check the governing standard, chemistry limits and mechanical properties against the order, and confirm on the mill test certificate.
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Mill test certificate (EN 10204 3.1) supplied with material; third-party inspection on request.
Reference basis: Compiled by Steel Impex India. Check each table’s source, product form and delivery condition before use. Sources, calculation methods and corrections.