Heat-resistant casting alloys of the H series are designed for strength and oxidation resistance at high temperature rather than for aqueous corrosion resistance. Their higher carbon content provides creep strength through carbide networks; chromium supplies oxidation resistance and nickel stabilises the austenitic structure and improves resistance to carburisation and thermal cycling.
Grades in this family
| Grade | Type | UNS | EN designation | Standard | Tensile strength Rm, min. (MPa) | Yield strength Rp0.2, min. (MPa) |
|---|---|---|---|---|---|---|
| HH | 25Cr-12Ni heat-resistant steel | J93503 | ≈ 1.4837 (GX40CrNiSi25-12) | ASTM A297/A297M | 515 | 240 |
| HK | 25Cr-20Ni heat-resistant steel | J94224 | ≈ 1.4848 (GX40CrNiSi25-20) | ASTM A297/A297M | 450 | 240 |
| CK20 | 25Cr-20Ni austenitic stainless steel, cast 310 type | J94202 | — | ASTM A351/A351M, A743/A743M | 450 | 195 |
| GX40CrNiSi25-20 (1.4848) | 25Cr-20Ni heat-resistant steel | — | 1.4848 (GX40CrNiSi25-20) | EN 10295 | 450 | 220 |
Minimum values (or ranges) for separately cast test bars as specified in
Casting and processing considerations
Usually supplied as cast, without heat treatment. Room-temperature ductility is limited and decreases after service exposure, so designs should avoid sharp notches and allow for thermal expansion. Acceptance is commonly based on chemical composition; high-temperature properties are design data rather than routine release tests.
Reference data compiled from the cited standards for orientation. Always work from the current edition of the governing specification; values are not a guaranteed LOSTWAX TR delivery specification.