SUS321 stainless steel VS SUS321H stainless steel: what is the difference?
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The core difference between SUS321 stainless steel and US321H stainless steel (such as ASTM 321H) lies in the carbon content and the performance difference it brings. The following is a specific comparison:
SUS321 stainless steel vs SUS321H chemical composition
| Element | SUS321 (JIS G4303) | SUS321H (JIS G4303) |
|---|---|---|
| Carbon (C) | ≤0.08% | 0.04%–0.10% |
| Silicon (Si) | ≤1.00% | ≤1.00% |
| Manganese (Mn) | ≤2.00% | ≤2.00% |
| Phosphorus (P) | ≤0.045% | ≤0.045% |
| Sulfur (S) | ≤0.030% | ≤0.030% |
| Chromium (Cr) | 17.0%–19.0% | 17.0%–19.0% |
| Nickel (Ni) | 9.0%–12.0% | 9.0%–12.0% |
| Titanium (Ti) | ≥5×C% | 4×(C+N)%–0.70% |
| Nitrogen (N) | ≤0.10% | ≤0.10% |
SUS321 stainless steel vs SUS321H performance high temperature strength
321H: higher carbon content, better creep resistance and stress fracture resistance in long-term high temperature environment (such as above 800℃), suitable for working conditions with continuous high temperature load.
SUS321: lower carbon content, slightly inferior to 321H in high temperature strength, but stronger resistance to intergranular corrosion after welding.
SUS321 stainless steel vs SUS321H weldability
SUS321: low C+Ti stabilized design, low risk of carbide precipitation during welding, suitable for structures with high welding quality requirements (such as pressure vessels, pipelines).
321H: high carbon may cause sensitization of the heat affected zone of welding, and the welding process needs to be strictly controlled (such as low heat input and post-weld solution treatment).
SUS321 stainless steel vs SUS321H corrosion resistance
Intergranular corrosion: SUS321 has better resistance to intergranular corrosion after welding due to its low carbon content and titanium stabilization.
Other corrosion: Both contain 17%~19% Cr and 9%~12% Ni, and behave similarly in general corrosive environments.
Applications of SUS321 stainless steel vs SUS321H
Equipment that needs to maintain corrosion resistance after welding (such as chemical containers, heat exchangers).
Parts exposed to short-term high temperatures (such as automobile exhaust pipes, aircraft engine exhaust systems).
321H
Structural parts in long-term high-temperature environments (such as power station boiler pipes, industrial furnace components).
Scenarios that require a combination of high strength and high-temperature oxidation resistance (such as oil refining equipment, petrochemical reactors).
SUS321 stainless steel vs. SUS321H stainless steel standards
SUS321: Japanese JIS standard, corresponding to the international grade 1.4541 or UNS S32100.
321H: American ASTM standard (such as A240/A240M), corresponding to UNS S32109, emphasizing high-temperature performance.
How to choose?
Choose SUS321: weldability is preferred, short-term high temperature or medium temperature environment, and resistance to intergranular corrosion is required.
Choose 321H: long-term high temperature (>800℃), high strength and creep resistance are required, and performance optimization through heat treatment is allowed.
