SS 321 vs SS 347
SS 321 (UNS S32100) vs SS 347 (UNS S34700): chemical composition and mechanical properties side by side.
- Strength: SS 347 minimum yield is 205 MPa vs 205 MPa for SS 321 (+0%); tensile 515 vs 515 MPa.
- Density: 7.93 vs 7.93 g/cm³ — same weight for the same dimensions.
- Pitting resistance (PREN, min): 17.0 vs 17.0 — equal.
- Typical use: SS 321 — Ti-stabilised for high temperature. SS 347 — Nb-stabilised for high temperature.
| Property | SS 321 | SS 347 |
|---|---|---|
| Family | Austenitic stainless | Austenitic stainless |
| UNS | S32100 | S34700 |
| EN / W.Nr | 1.4541 X6CrNiTi18-10 | 1.4550 X6CrNiNb18-10 |
| Basis spec | ASTM A240 | ASTM A240 |
| Density g/cm³ | 7.93 | 7.93 |
| Chemical composition, % | ||
| C | 0.08 | 0.08 |
| Mn | 2.00 | 2.00 |
| P | 0.045 | 0.045 |
| S | 0.030 | 0.030 |
| Si | 0.75 | 0.75 |
| Cr | 17.0–19.0 | 17.0–19.0 |
| Ni | 9.0–12.0 | 9.0–13.0 |
| N | 0.10 | – |
| Ti | 5×(C+N)–0.70 | – |
| Nb | – | 10×C–1.00 |
| Mechanical properties (min) | ||
| Tensile strength | 515 MPa (75 ksi) | 515 MPa (75 ksi) |
| Yield strength (0.2%) | 205 MPa (30 ksi) | 205 MPa (30 ksi) |
| Elongation | 40% | 40% |
| Hardness (max) | 217 HB | 201 HB |
| PREN (min, from spec) | 17.0 | 17.0 |
Single values are maximums; ranges are min–max; "bal" = balance. Limits are typical of the basis specification for that product form — forgings, pipe and fittings specifications differ slightly. Always check the exact specification, edition and the mill test certificate.
Frequently asked questions
What is the difference between SS 321 and SS 347?
Strength: SS 347 minimum yield is 205 MPa vs 205 MPa for SS 321 (+0%); tensile 515 vs 515 MPa. Density: 7.93 vs 7.93 g/cm³ — same weight for the same dimensions. Pitting resistance (PREN, min): 17.0 vs 17.0 — equal.
Which is stronger, SS 321 or SS 347?
SS 321 has the higher minimum yield strength (205 MPa vs 205 MPa).
Last updated 2026-11-02