JIS SUS310S Steel: AISI 310S Equivalent — High-Temperature Stainless up to 1100°C

SUS310S (JIS G4303) is the high-temperature austenitic stainless steel — 24–26% Cr and 19–22% Ni, nearly double the chromium content of SUS304. Where SUS304 begins to scale at around 870°C (1598°F), SUS310S maintains a stable oxide film up to 1100°C (2012°F) in continuous service and 1150°C (2102°F) in cyclic service. The dense Cr₂O₃/SiO₂ scale it forms resists both oxidation and carburization, making it the standard choice for heat treatment fixtures, furnace components, kiln furniture, petrochemical furnace tubes, and radiant tubes in industrial heating systems. This guide defines the temperature and atmosphere limits where SUS310S performs, and the two failure modes that catch engineers by surprise.

1. International Equivalent Grades

2. Chemical Composition

The 25Cr-20Ni composition is specifically chosen for high-temperature stability: sufficient Cr for oxidation resistance up to 1100°C, sufficient Ni to stabilize the austenite phase at elevated temperature and prevent sigma-phase embrittlement at moderate rates.

3. Mechanical Properties

High-temperature strength is low by structural standards — SUS310S is used in furnace applications where loads are primarily thermal expansion stresses, not structural loads. For load-bearing high-temperature applications, heat-resistant alloys (Alloy 601, 330 SS) or refractory metals are specified.

4. High-Temperature Performance

Continuous vs Cyclic Service Temperature Limits

Cyclic service (repeated heating and cooling) is more damaging than continuous operation because thermal expansion cycling stresses and spalls the protective oxide scale. Once scale spalls, the fresh metal surface re-oxidizes and the scale grows thicker over time, eventually losing adhesion.

5. Oxidation & Carburization Resistance

Oxidation

SUS310S forms a tightly adherent Cr₂O₃ scale with a thin SiO₂ sublayer that limits outward Cr diffusion and inward oxygen diffusion. This scale remains stable and adherent up to ~1100°C in dry air. Wet atmospheres (steam, combustion gases with high moisture) partially dissolve the scale at elevated temperature — derate maximum service temperature by 50–80°C in steam-containing atmospheres.

Carburization Resistance

Carbon-bearing atmospheres (furnace gases, cracking atmospheres, carburizing furnace environments) attack stainless steel by diffusing C into the metal, forming chromium carbides that deplete the Cr available for passivation. SUS310S’s high Cr and Ni content provides good carburization resistance up to ~950°C. Above 1000°C in high-carbon-activity atmospheres, metal dusting (disintegration into carbon-containing powder) can occur — specify Alloy 601 or higher-alloy grades for these conditions.

6. Fabrication: Welding & Forming

Welding

SUS310S welds readily with no preheat. Recommended filler: ER310 (matching composition) or ERNiCr-3 (Alloy 82) for improved thermal fatigue resistance in cyclic service. Post-weld solution anneal at 1050–1120°C improves corrosion resistance and ductility by dissolving sensitization carbides. For furnace components that cannot be fully re-annealed, use low-heat-input welding (stringer beads, low interpass temperature) to minimize HAZ sensitization.

Forming

SUS310S has lower formability than SUS304 due to higher alloy content — work-hardening rate is slightly higher and springback is greater. Cold forming is feasible for sheet components; heavy forming operations require intermediate anneals. Hot forming at 1100–1200°C (2012–2192°F) is straightforward.

7. Common Mistakes

8. When to Choose SUS310S

9. FAQ

Q: What is the maximum service temperature for SUS310S?

1100°C (2012°F) in continuous service in dry air or mildly oxidizing atmospheres. In cyclic service (repeated heating/cooling), derate to ~1050°C (1922°F). In steam-containing or high-moisture combustion atmospheres, derate by an additional 50–80°C. Above 1100°C, consider Alloy 601 or other nickel-base heat-resistant alloys.

Q: Is SUS310S the same as AISI 310S?

Yes — JIS G4303 SUS310S and ASTM A240 Type 310S share the same 24–26% Cr / 19–22% Ni / ≤ 0.08% C composition. Both differ from AISI 310 (no suffix), which allows up to 0.25% C and is primarily for castings. When ordering, specify 310S to ensure the low-carbon, weldable grade.

Q: Can SUS310S be used for cryogenic applications?

Yes — as a fully austenitic grade, SUS310S retains excellent toughness at cryogenic temperatures (down to −196°C / −321°F). However, SUS304L and SUS316L are the standard cryogenic grades due to lower cost. SUS310S is used cryogenically only when its higher alloy content provides a specific advantage (very aggressive media, specific certification requirements).