what is the difference between 321 and 347 stainless steel？
what is the difference between 321 and 347 stainless steel in terms of corrosion resistance?
Intergranular corrosion
321: No solution treatment is required after welding to resist intergranular corrosion, suitable for pressure vessels and pipelines that are frequently welded.
347: Niobium carbides are more stable at high temperatures (600-800°C), and have slightly better corrosion resistance when used for a long time.
Pitting and crevice corrosion
The corrosion resistance of the two is similar, and 347 may perform slightly better in a fluoride-containing environment because it contains Nb.
High-temperature oxidation
The oxidation resistance temperature of 347 can reach 980°C, which is better than 900°C of 321, and is suitable for extremely high temperature scenes such as boilers and nuclear reactors.
Standard
| Standard System | 321 Stainless Steel | 347 Stainless Steel |
|---|---|---|
| ASTM | A240/A240M S32100 | A240/A240M S34700 |
| EN | 1.4541 (X6CrNiTi18-10) | 1.4550 (X6CrNiNb18-10) |
| ISO | X6CrNiTi18-10 (ISO 683-12) | X6CrNiNb18-10 (ISO 683-12) |
Chemical Composition
| Element | 321 Stainless Steel | 347 Stainless Steel |
|---|---|---|
| Cr | 17.0-19.0% | 17.0-19.0% |
| Ni | 9.0-12.0% | 9.0-13.0% |
| Ti | ≥5×C% (Titanium stabilization) | – |
| Nb+Ta | – | ≥10×C% (Niobium+Tantalum stabilization) |
| C | ≤0.08% | ≤0.08% |
Mechanical Properties
| Property | 321 Stainless Steel (Solution Annealed) | 347 Stainless Steel (Solution Annealed) |
|---|---|---|
| Yield Strength | ≥205 MPa | ≥205 MPa |
| Tensile Strength | ≥520 MPa | ≥520 MPa |
| Elongation | ≥40% | ≥40% |
