SS 310 Stainless Steel & 310S Supplier

SS 310 stainless steel is the highest-alloyed of the standard austenitic heat-resisting grades, carrying 24 to 26 percent chromium and 19 to 22 percent nickel. That chromium level builds a scale that stays adherent where 304 spalls, which is why 310 and its low-carbon partner 310S are the default choice for furnace parts, kiln components and radiant tubes. Walmay supplies both UNS S31000 and UNS S31008 in sheet and plate, pipe, bar, coil and structural beams, to ASTM A240, A312, A276 and A479 with an EN 10204 3.1 certificate on every heat.

310 and 310S Products We Supply

Form	Range	Standard	Page
Sheet and plate	1.0-50 mm thick, to 2,000 mm wide	ASTM A240	310S sheet and plate
Pipe and tube	NPS 1/2-12, OD 10-325 mm	ASTM A312	310S pipe
Round bar	8-250 mm diameter	ASTM A276 / A479	310S round bar
Hot rolled coil	2.0-6.0 mm, to 1,500 mm wide	ASTM A240	310S hot coil
H-beam and profiles	Structural sections	EN 10088-4	310S H-beam

Chemical Composition

Limits to ASTM A240, in percent by mass. The only meaningful difference between the two grades is carbon.

Element	310 (UNS S31000)	310S (UNS S31008)
Carbon	0.25 max	0.08 max
Chromium	24.0-26.0	24.0-26.0
Nickel	19.0-22.0	19.0-22.0
Manganese	2.00 max	2.00 max
Silicon	1.50 max	1.50 max
Phosphorus	0.045 max	0.045 max
Sulphur	0.030 max	0.030 max

310 or 310S: Which One to Order

That single difference in carbon changes how each grade behaves.

Consideration	310	310S
Carbon	Up to 0.25 percent	Up to 0.08 percent
Creep strength at temperature	Higher, carbon strengthens the matrix	Slightly lower
Weldability	Poorer, risk of carbide precipitation	Good, the reason it exists
Sensitisation after welding	Possible, may need solution anneal	Much lower risk
Typical use	Heavy cast or machined parts held hot, not welded	Welded fabrications, sheet, plate and tube
Availability	Limited, mostly bar and castings	The commercial standard for flat and tubular product

In practice almost all mill product is supplied as 310S, and most enquiries that specify 310 are satisfied by 310S. Specify 310 only where a code or drawing calls for the higher carbon and creep strength and the part will not be welded.

310S Stainless Steel Properties

Property	Typical value
Yield strength, 0.2 percent proof	205 MPa minimum
Tensile strength	515 MPa minimum
Elongation in 50 mm	40 percent minimum
Hardness	95 HRB maximum
Density	7.98 g/cm3
Modulus of elasticity	200 GPa
Thermal conductivity at 100 C	14.2 W/m.K
Coefficient of thermal expansion, 20-100 C	15.9 micrometres per m.K
Melting range	1,400-1,450 C
Magnetic response	Non-magnetic in the annealed condition
PREN	Approximately 25

Service Temperature

Condition	Limit
Continuous service in air	Up to 1,150 C
Intermittent or cyclic service	Up to 1,035 C
Scaling temperature	About 1,035 C in cyclic exposure
Sigma phase embrittlement range	600-900 C on long exposure
Cryogenic service	Down to liquid helium temperature, tough at low temperature

The intermittent limit sits below the continuous limit, which looks wrong until you consider the mechanism. Under steady heat the oxide scale grows once and stays put. Under thermal cycling the scale cracks and spalls on every cooldown, exposing fresh metal, so the effective limit drops. Design accordingly: a part that is heated and cooled daily needs to be rated at the cyclic figure, not the continuous one.

Two cautions matter in service. Long exposure between 600 and 900 C precipitates sigma phase, which embrittles the material at room temperature even though it performs normally when hot; parts that will be inspected cold should be designed with that in mind. And 310 has limited resistance to high-sulphur reducing atmospheres, where its high nickel content forms low-melting nickel sulphide; for sulphidising service a lower-nickel heat-resisting grade is the better choice.

How 310S Compares

Grade	Chromium	Nickel	Continuous limit	Notes
304	18-20	8-10.5	About 870 C	Scales and loses strength above that
321	17-19	9-12	About 900 C	Titanium stabilised, good for 500-800 C cycling
309S	22-24	12-15	About 1,000 C	Intermediate, cheaper than 310S
310S	24-26	19-22	About 1,150 C	The standard high-temperature austenitic
330	17-20	34-37	About 1,150 C	Higher nickel, better carburisation resistance

Against 304 the difference in the furnace is not marginal. A 304 component in a 1,000 C environment scales heavily and distorts; a 310S component in the same position gives years of service. The trade-off is cost, since 310S carries roughly twice the nickel of 304, and lower strength at room temperature than a duplex or hardenable grade.

For corrosion rather than heat, 310S is not the answer. Its PREN of about 25 is close to 316L, so in chloride service specify 316L, 2205 duplex or 2507 super duplex, and in acid service specify 904L.

Fabrication and Welding

310S welds readily with TIG, MIG or stick using ER310 or ER310S filler, which matches the parent composition. Use nickel-base filler such as ERNiCrFe-3 where the joint will see thermal cycling, because a matching austenitic weld has the same high expansion coefficient as the parent and accumulates strain.

Three practical points. The coefficient of thermal expansion is around 16 micrometres per metre per kelvin, roughly 40 percent higher than carbon steel, so allow for movement in the design and expect distortion during welding. The grade work hardens quickly, so machining runs at about 40 percent of the rate of 304 and needs sharp, rigid tooling. And hot forming should be done between 1,150 and 900 C followed by solution annealing at 1,040 to 1,100 C to restore ductility. Our heat treatment and welding pages cover both operations.

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Applications

Furnace linings, muffles, retorts and radiant tubes
Kiln components, burner nozzles and grate bars in cement and lime plant
Heat treatment fixtures, baskets and trays
Boiler and superheater components in energy production plants
Flue gas ducting and recuperators
Cryogenic vessels and equipment, where 310S stays tough at very low temperature
Ore processing and sinter plant equipment in machinery manufacturing workshops
Fluidised bed combustors and coal gasifier internals

Equivalent Designations

System	310	310S
UNS	S31000	S31008
AISI / SAE	310	310S
EN / Werkstoff	1.4841	1.4845
EN name	X15CrNiSi25-21	X8CrNi25-21
JIS	SUS310	SUS310S
GB / T	2Cr25Ni20	06Cr25Ni20
ASTM flat products	A240	A240
ASTM pipe	A312	A312
ASTM bar	A276 / A479	A276 / A479

Ordering

Item	Detail
Minimum order	500 kg for stock items, 2-3 tonnes for mill-rolled sizes
Lead time from stock	10-15 days to loading
Lead time mill run	35-50 days
Surface	No.1 pickled on hot rolled, 2B on cold rolled, polished on request
Processing	Cut to size, levelled, hot formed and solution annealed before dispatch
Certification	EN 10204 3.1 with heat number, plus high-temperature test data on request

Because 310S carries roughly 20 percent nickel, its price is strongly exposed to the nickel market. Send the form, size, quantity, service temperature and whether the exposure is continuous or cyclic, and we will confirm the grade before quoting.

The full range is under stainless steel products, with company background on our about us page.

FAQs

What is 310 grade stainless steel?

An austenitic heat-resisting stainless steel with 24 to 26 percent chromium and 19 to 22 percent nickel, designated UNS S31000. The high chromium builds an adherent oxide scale that survives to about 1,150 C in continuous service, and the high nickel keeps the structure austenitic and tough. It is a heat-resisting grade rather than a corrosion-resisting one.

What is 310S stainless steel?

The low-carbon version, UNS S31008, with carbon capped at 0.08 percent instead of 0.25 percent. Everything else in the composition is identical. The lower carbon makes it weldable without significant risk of carbide precipitation, which is why almost all sheet, plate, pipe and coil is supplied as 310S rather than 310.

What is the difference between stainless steel 310 and 310S?

Carbon content only: 0.25 percent maximum in 310 against 0.08 percent maximum in 310S. The higher carbon in 310 gives slightly better creep strength at temperature, which suits heavy machined or cast parts held hot. The lower carbon in 310S gives much better weldability and far less risk of sensitisation, which is why it dominates commercial mill production.

Is 310 stainless steel good?

For high-temperature service it is one of the best standard grades available, rated for continuous use to about 1,150 C where 304 is limited to roughly 870 C. For corrosion service it is unremarkable, with a PREN of about 25, similar to 316L. It is also expensive because of its nickel content, and it should not be used in high-sulphur reducing atmospheres. Judge it strictly on whether the application is thermal.

Is 304 or 310 stainless steel better?

They are not competing for the same job. 304 is the general-purpose grade: cheaper, widely stocked, easier to machine, adequate for most corrosion duty up to about 870 C. 310 or 310S is the high-temperature grade, worth its premium only above roughly 900 C or where thermal cycling would spall the scale on 304. Below 870 C, choosing 310S is paying twice for nickel you do not need.

What is the equivalent of 310 stainless steel?

310 corresponds to UNS S31000, EN and Werkstoff 1.4841 designated X15CrNiSi25-21, JIS SUS310 and GB 2Cr25Ni20. 310S corresponds to UNS S31008, Werkstoff 1.4845 designated X8CrNi25-21, JIS SUS310S and GB 06Cr25Ni20.

Is 310S magnetic?

No. With 19 to 22 percent nickel it is fully and stably austenitic, and it stays essentially non-magnetic even after cold working, more so than 304 which can develop a slight magnetic response when formed.

Can 310S be used in cryogenic service?

Yes. Its austenitic structure has no ductile-to-brittle transition, so it remains tough down to liquid helium temperatures and is used for cryogenic vessels and equipment as well as furnace parts. The same grade covers both extremes of the temperature range.

Why is the intermittent temperature limit lower than the continuous limit?

Under steady heat the protective oxide scale forms once and remains adherent. Under thermal cycling the scale cracks and spalls on each cooldown because the metal and the oxide contract at different rates, exposing fresh metal to oxidise on the next heating. The result is faster metal loss under cycling, so the safe limit falls from about 1,150 C continuous to about 1,035 C cyclic.