310 steel (S31000): properties, composition, equivalents

310 / 310S stainless steel (UNS S31000 / S31008, EN 1.4845): 24–26 % Cr, 19–22 % Ni for continuous service to 1100 °C. 205 MPa yield, 515 MPa tensile. Composition, oxidation limits, creep, 310 vs 309 vs 321, 1.4845/SUS310S equivalents.

What is 310?

Type 310 is the heat-resisting austenitic stainless steel: 25 % chromium and 20 % nickel give a scale that stays adherent in air to about 1100 °C (2000 °F) continuous and 1150 °C intermittent — roughly 250 °C beyond 304 or 321. It also resists carburizing, nitriding and sulphur-bearing atmospheres better than the 18-8 grades, and its high nickel keeps the structure fully austenitic and ductile through repeated heating and cooling. That combination puts it in furnace muffles, radiant tubes, kiln linings, heat-treatment baskets, burner parts, thermowells and fluidized-bed components. UNS S31000; the low-carbon 310S (S31008, C ≤ 0.08 %) is the grade actually stocked as plate and pipe, and 310H (S31009) is the creep-rated version for ASME pressure parts.

Room-temperature minimums are the familiar 205/515 MPa; at 800 °C the alloy still holds about 120 MPa yield. The main service limitation is sigma-phase formation after long exposure at 650–900 °C, which embrittles the steel at room temperature — parts that cycle through that range should be inspected for cracking on cooling. Corrosion resistance in aqueous service is moderate (PREN ≈ 25) and rarely the reason for choosing 310.

EN 1.4845, JIS SUS310S, GB 06Cr25Ni20 and BS 310S24 are the same grade; the higher-silicon EN 1.4841 and the cast HK-40 are near relatives for furnace work.

310 chemical composition

ASTM A240/A240M-22 (S31000, S31008). EN 1.4845 (X8CrNi25-21): C ≤ 0.10, Cr 24–26, Ni 19–22, Si ≤ 1.5 — corresponds to 310S. EN 1.4841 (X15CrNiSi25-21, Si 1.5–2.5) is the higher-Si heat-resisting version of EN 10095.

310 mechanical properties

Minimums per ASTM A240/A276/A312/A213. Typical annealed: yield 270–310 MPa, tensile 600–650 MPa. 100 000 h creep-rupture strength (310H, typical): ≈ 35 MPa at 700 °C, 15 MPa at 800 °C, 6 MPa at 900 °C.

Impact toughness

310 requires a minimum Charpy V-notch energy of 80 J at -196 °C (typical, annealed). Fully austenitic and stable; also used for cryogenic parts, but sigma-phase embrittlement after long service at 650–900 °C sharply reduces room-temperature toughness.

310 equivalent grades

Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for 310 →

Old and superseded designations

Product forms and tolerance standards

Product forms: sheet, strip, plate (ASTM A240 — 310S is the usual flat-product grade), bar and forgings (A276, A479), seamless and welded pipe and tube (A312 TP310S, A213 TP310H, A269), fittings (A403 WP310S), wire, castings HK-40 / CK-20 (A297, A351).

Dimensional tolerances: sheet/plate: ASTM A480; bar: ASTM A484; pipe: ASTM A999.

Key property values

310 stainless steel yield strength

Minimum 205 MPa (30 ksi) annealed; typical 270–310 MPa. Typical at 600 °C ≈ 150 MPa, 800 °C ≈ 120 MPa, 1000 °C ≈ 50 MPa.

310 tensile strength

Minimum 515 MPa (75 ksi); typical 600–650 MPa annealed; ≈ 230 MPa at 800 °C.

310 hardness

Annealed max 217 HB / 95 HRB; typical 160–190 HB. Not hardenable by heat treatment.

Maximum service temperature

Oxidation in air: 1100 °C continuous, 1150 °C intermittent (thermal cycling is tolerated better than by ferritic 446 because expansion is uniform). ASME creep design: 310H to 816 °C (1500 °F). Resists dry sulphur-bearing gases to ~1000 °C (reducing atmospheres lower this), carburizing and nitriding atmospheres moderately well; poor in molten metals and salts.

Creep strength

100 000 h rupture (310H, typical): ≈ 35 MPa at 700 °C, 15 MPa at 800 °C, 6 MPa at 900 °C. For higher creep strength at 900–1100 °C use 253MA, 314, or cast HK/HP alloys.

Physical properties

Density 7.9 g/cm³, E = 200 GPa, expansion 15.9 × 10⁻⁶/K (0–100 °C), 18.5 (0–800 °C), conductivity 14.2 W/m·K, resistivity 0.78 µΩ·m, non-magnetic.

Heat treatment

Solution anneal 1040–1150 °C (1900–2100 °F), water quench or rapid air cool. Do not stress-relieve at 650–900 °C. Sigma-phase embrittlement can be reversed by re-annealing above 1050 °C.

Weldability

Good weldability with matching ER310 / E310-16 filler (fully austenitic weld metal — keep heat input low, ≤ 1.5 kJ/mm, and interpass ≤ 150 °C to avoid hot cracking; ER312 for dissimilar or highly restrained joints). No preheat; no PWHT for corrosion reasons. 310 welds are prone to micro-fissuring in thick multi-pass joints — use stringer beads.

Machining, forming and heat treatment

Machinability ≈ 35–40 % of B1112 (tough, high work-hardening, high nickel); rigid setups, sharp carbide, low speed / positive feed, flood coolant. Forming is good in the annealed state (bending, spinning, drawing) with about 20 % higher loads than 304. Hot forming 1150–980 °C followed by solution annealing.

Typical applications

• Furnace muffles, retorts, radiant tubes, kiln and oven linings
• Heat-treatment trays, baskets, fixtures and conveyor belts
• Burner components, flare tips, combustion chambers
• Thermowells, thermocouple protection tubes, sight glasses frames
• Fluidized-bed components, incinerator and waste-heat boiler parts
• Refinery tube supports and hangers, coke-oven equipment
• Cryogenic parts requiring stable austenite (secondary use)

Frequently asked questions

Related grades

Verified against ASTM A240/A240M-22; ASTM A240/A240M-22 Tables 1–2; ASTM A312/A312M-22; ASTM A213/A213M-22 (TP310H); EN 10095:2018 (heat-resisting comparison). Last checked: September 2026.