AISI 310S

What is AISI 310S?

AISI 310S is a heat-resisting austenitic stainless steel. It contains 24.0 to 26.0 percent chromium and 19.0 to 22.0 percent nickel. Carbon is limited to 0.08 percent, and silicon may reach 1.5 percent. The chromium forms an adherent, self-repairing oxide scale at temperatures where the scale on an 18/8 steel would spall. The nickel maintains an austenitic structure despite the high ferrite-forming chromium content.

The 310 family includes 310, 310H and 310S. Grade 310 permits up to 0.25 percent carbon. Grade 310H specifies 0.04 to 0.10 percent carbon for maximum creep strength. Grade 310S limits carbon to 0.08 percent and suits environments that contain moist corrodents below temperatures normally associated with high-temperature service. Its lower carbon content reduces sensitisation resistance concerns but also gives lower high-temperature strength than 310H.

AISI 310S contains a chromium reserve of 24 to 26 percent. This concentration passivates the surface and supports repeated oxide-scale formation over thousands of hours at temperatures around and above 1,000 degrees Celsius.

Laxcon Steels lists AISI 310S in its grades reference as an austenitic grade. The same steel is written 310S, SUS 310S, 1.4845 and S31008.

What is the chemical composition of AISI 310S?

Composition limits in weight percent are carbon 0.08 maximum, manganese 2.0 maximum, sulphur 0.03 maximum, phosphorus 0.045 maximum, silicon 1.5 maximum, chromium 24.0 to 26.0 and nickel 19.0 to 22.0.

What is AISI 310S equivalent to in other standards?

Corrected 2026-08-18 from the inherited 1.4842 to 1.4845, the EN number in production use for TYPE 310S.

Equivalence means nearest counterpart, not identity: each standards body sets its own composition window, so check the limits of the standard actually named on the order before substituting.

What is the PREN of AISI 310S?

Computed by Laxcon Steels from the composition above as PREN = Cr + 3.3Mo + 16N, the relationship published in Practical Guidelines for the Fabrication of Duplex Stainless Steels (International Molybdenum Association, third edition, 2014). The first figure uses the minimum specified chromium, molybdenum and nitrogen, so it is the floor for a conforming heat rather than a typical value; the second uses the maxima, so the two together are the width of the band one compliant grade allows. PREN ranks resistance to chloride pitting and nothing else: it does not predict crevice corrosion, stress corrosion cracking or service life, and it is not a substitute for a corrosion test. The pitting resistance reference carries the full table and the caveats.

Mechanical and physical properties

ASTM A276 places type 310S in the same Condition A group as 304 and 316. Hot-finished annealed bar must have a minimum tensile strength of 515 MPa, a minimum 0.2 percent yield strength of 205 MPa, 40 percent elongation in 50 mm and 50 percent reduction of area. ASTM A240 specifies the same tensile and yield strengths for plate. It sets a maximum hardness of 95 HRB or 217 HB. Cold-finished Condition A bar up to 12.70 mm diameter requires a tensile strength of 620 MPa and a yield strength of 310 MPa.

The density is about 7,750 kg per cubic metre, and the elastic modulus is about 200 GPa. Thermal conductivity is about 14.2 W per metre kelvin at 100 degrees Celsius and about 18.7 W per metre kelvin at 500 degrees Celsius. The mean coefficient of thermal expansion from 0 to 100 degrees Celsius is about 15.9 micrometres per metre per degree Celsius. The corresponding value for 304 is 17.2. These properties affect the response of furnace fixtures to repeated thermal cycles.

High-temperature corrosion behaviour

The 310 family resists oxidation in intermittent air service to about 1,040 degrees Celsius and in continuous air service to about 1,150 degrees Celsius. The continuous-service limit is higher because thermal cycling causes the oxide scale and the underlying metal to expand and contract at different rates. This movement can detach the scale and expose fresh metal to oxidation.

AISI 310S also resists thermal fatigue and cyclic heating. It is used at elevated temperatures in atmospheres that contain sulphur dioxide. The grade has good resistance to oxidising and carburising atmospheres. It withstands fuming nitric acid at room temperature and fused nitrates to about 425 degrees Celsius.

Sigma phase and solution treatment

Sigma phase is a hard and brittle iron-chromium intermetallic. It precipitates in AISI 310S at roughly 650 to 900 degrees Celsius. Its formation reduces room-temperature toughness and ductility. It also removes chromium from solution and reduces corrosion resistance.

Solution treatment consists of heating to 1,040 to 1,150 degrees Celsius followed by rapid cooling. The same treatment is recommended after each 1,000 hours of service above 650 degrees Celsius to restore ductility. Components exposed to prolonged high-temperature service therefore require periodic re-annealing.

Aqueous corrosion behaviour

The pitting resistance equivalent number is 24.0 at the specified composition minima and 26.0 at the maxima. The value derives from chromium because the grade contains no molybdenum and has no specified nitrogen content. Practical resistance in sea water extends to about 22 degrees Celsius and is similar to that of AISI 316. AISI 310S has better aqueous corrosion resistance than 304 and is approximately comparable with 316 because of its chromium content. It is more resistant to chloride stress corrosion cracking than 304 or 316, but it is not immune.

Applications and designations

Applications include furnace parts, muffles, retorts, radiant tubes, heat-treatment baskets, jigs, fixtures, carburising boxes, oil-burner components, kiln linings and supports. The grade is also used for heat exchangers in hot-gas service and for welding filler wire and electrodes used to join heat-resisting steels.

The nearest European counterpart is EN material number 1.4845, with the name X8CrNi25-21. The UNS designation is S31008. The Japanese designation is SUS 310S, also written without spaces as SUS310S or SS310S. Equivalence between specification systems is less exact for heat-resisting grades than for corrosion-resisting grades. The standard stated on the order therefore governs the material requirements.

Where AISI 310S is not the right choice

AISI 310S is unsuitable for reducing sulphur-bearing atmospheres. Its 19 to 22 percent nickel can form a low-melting eutectic with sulphur. This reaction attacks grain boundaries and can cause faster failure in reducing sulphidising gas than in a lower-nickel alternative. Grades intended for this duty use silicon and rare earth additions instead of nickel to maintain their scale.

AISI 310S is also unsuitable for components that are welded and then placed in wet service without solution annealing. Carbon contents up to 0.08 percent permit sensitisation in the range from 425 to 860 degrees Celsius, as in 304. Long holding periods between about 650 and 900 degrees Celsius are unsuitable unless the design includes periodic re-annealing. Sigma phase accumulates in this range and reduces toughness.

AISI 310S is not the preferred grade when maximum hot strength is required. AISI 310H specifies 0.04 to 0.10 percent carbon for that purpose and has greater high-temperature strength. AISI 310S is also unsuitable when chloride pitting resistance is the primary requirement. Its PREN range of 24.0 to 26.0 is below that of duplex grades. Duplex 2205 or super duplex 2507 should be considered for that requirement.

Other austenitic grades