347H vs 321H
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
347H
Stainless Steel
347H is the high-carbon niobium-stabilised grade for creep-range pressure service, combining the sensitisation resistance of 347 with code creep-rupture values. It is widely used in refinery and steam plant.
Standards: DIN 1.4912 · AISI 347H · JIS SUS347 · GB 07Cr19Ni11Nb
321H
Stainless Steel
321H is the high-carbon, titanium-stabilised variant of 321, combining sensitisation resistance with guaranteed creep strength for high-temperature pressure parts. It is used in boiler and refinery service where plain 321 lacks code strength values.
Standards: DIN 1.4878 · AISI 321H · JIS SUS321 · GB 07Cr19Ni11Ti
Chemical composition compared (%)
| Element | 347H | 321H |
|---|---|---|
| C | 0.04–0.10 | 0.04–0.10 |
| Si | ≤0.75 | ≤0.75 |
| Mn | ≤2.00 | ≤2.00 |
| P | ≤0.045 | ≤0.045 |
| S | ≤0.030 | ≤0.030 |
| Cr | 17.00–19.00 | 17.00–19.00 |
| Ni | 9.00–13.00 | 9.00–12.00 |
| Nb | 8×C–1.00 | — |
| Ti | — | 4×(C+N)–0.70 |
| N | — | ≤0.10 |
Properties compared
| Property | 347H | 321H |
|---|---|---|
| Delivery condition | Annealed | Annealed |
| Hardness | ≤217 HB (annealed) | ≤217 HB (annealed) |
| Tensile strength | 515–690 MPa | 515–690 MPa |
| Density | 7.90 g/cm³ | 7.90 g/cm³ |
| Creep service | Rated for pressure service above ~525 °C | Rated for pressure service above ~525 °C |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: 347H · 321H. Substitution decisions for certified parts stay with the design authority.