Low-Carbon 25Cr-20Ni Heat-Resistant Austenitic Stainless Steel
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UNS NUMBER
S31008
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ALLOY FAMILY
Austenitic (Heat-Resistant)
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STRUCTURE
100% Austenite
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UTS (MIN)
≥515 MPa
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MAX TEMP
~1150°C
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DENSITY
7.98 g/cm³
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Stainless Steel 310S (UNS S31008) is the low-carbon version of 310, with chromium 24–26% and nickel 19–22% for oxidation resistance to about 1150°C. The carbon cap of 0.08% makes it the preferred grade for welded furnace parts, radiant tubes, and heat-treatment equipment.
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Cr
24–26%
Oxidation resistance to 1150°C
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Ni
19–22%
Austenite + sulfidation resistance
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Mo
— (none)
Not added
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C
≤0.08%
Low carbon, weld-friendly
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UTS
≥515 MPa
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YS 0.2%
≥205 MPa
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Elong.
≥40%
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Service
up to 1150°C
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What is Stainless Steel 310S?
310S keeps the 25Cr-20Ni heat-resistant recipe but limits carbon to 0.08% maximum. That removes the sensitisation and embrittlement tendency of full-carbon 310, so welded fabrications stay sound without post-weld heat treatment. It is the most widely specified version of the 310 family for furnace and petrochemical hardware.
Like 310, it has no molybdenum, so its pitting resistance in liquid chlorides is modest (PREN ~25). Its value is dry high-temperature service: radiant tubes, retorts, kiln components, and thermowells. For cyclic thermal shock from repeated liquid quenching, even 310S is a poor choice — it is best in steady high-temperature duty. Where 316 runs hot (above ~650°C) the sigma-phase risk makes 310S the safer substitute.
Chemical Composition (Weight %)
| Element |
Min (%) |
Max (%) |
Role in Alloy |
| Chromium (Cr) |
24.0 |
26.0 |
Oxidation resistance to 1150°C |
| Nickel (Ni) |
19.0 |
22.0 |
Austenite; sulfidation resistance |
| Carbon (C) |
— |
0.08 |
Low carbon, weld-friendly |
| Manganese (Mn) |
— |
2.00 |
Deoxidizer |
| Silicon (Si) |
— |
1.50 |
Oxidation/surface stability |
| Phosphorus (P) |
— |
0.045 |
Impurity |
| Sulfur (S) |
— |
0.030 |
Impurity |
| Molybdenum (Mo) |
— |
0.75 |
Minor, not a design element |
| Iron (Fe) |
Balance |
— |
Matrix former |
★ Carbon ≤ 0.08% distinguishes 310S from 310 (C up to 0.25%). The low carbon avoids carbide sensitization in welded fabrications and is the reason 310S is preferred for furnace hardware.
Mechanical Properties
Values are for the annealed condition per ASTM A240, A182 (F310S), and A312 (TP310S).
| Condition / Form |
UTS (MPa) |
YS 0.2% (MPa) |
Elong. % (min) |
Hardness (max) |
| Minimum (ASTM A240 / A182 F310S) |
≥515 |
≥205 |
40 |
225 HBW (95 HRB) |
| Typical annealed |
520–600 |
205–290 |
40–50 |
170–200 HBW |
Modulus of Elasticity 200 GPa. Design in the creep range uses ASME high-temperature allowable stresses. Not hardenable by heat treatment.
Physical Properties
| Property |
Value |
Note |
| Density |
7.98 g/cm³ |
Slightly above 304 |
| Melting Range |
1400–1450°C |
Solidus ~1400°C |
| Thermal Conductivity (100°C) |
14.2 W/m·K |
Lower than carbon steel |
| Thermal Expansion (20–100°C) |
15.9 ×10⁻⁶ /K |
Lower than 304 |
| Specific Heat |
500 J/kg·K |
At 21°C |
| Electrical Resistivity |
0.78 µΩ·m |
At 21°C |
| Magnetic Property |
Non-magnetic |
Annealed |
| PREN (Pitting Resistance) |
~25 |
Cr 25, no Mo |
Corrosion Resistance
High-Temperature Oxidation
The 25% chromium resists scaling in air to about 1150°C continuous, 1035°C intermittent. This is the main reason to pick 310S over 304/316 in furnaces.
Sulfidation & Carburization
High nickel gives good resistance to sulfur-bearing gases in oxidizing atmospheres and moderate resistance to carburizing environments. Worse carburizing atmospheres need a higher-nickel alloy.
Pitting & Aqueous Corrosion
No molybdenum (PREN ~25) means poor pitting/crevice resistance in chlorides. 310S is a dry-heat grade, not a seawater or process-liquid grade.
Comparison to 316 at Temperature
Above about 650°C, 316 is prone to brittle sigma-phase formation. In that temperature band 310S is the more reliable high-temperature substitute despite its lower room-temperature strength.
Stainless Steel 310S vs Similar Grades — Selection Guide
| If you need... |
Choose... |
Why |
| Welded furnace / radiant tube to 1150°C |
310S |
Low carbon, oxidation resistant |
| Strongest carburizing / >1150°C |
Nickel alloy (800H/601) |
Higher temperature capability |
| Steady 650–900°C, replacing 316 |
310S |
Avoids 316 sigma phase |
| Chloride liquid service |
316L / 904L |
Need molybdenum |
| Cheaper lean heat part to ~900°C |
253MA |
Less nickel, good creep |
Applicable Standards
| Standard |
Product Form |
| ASTM A240 |
Plate, sheet, strip |
| ASTM A182 F310S |
Forged flanges & fittings |
| ASTM A312 TP310S |
Seamless & welded pipe |
| ASTM A403 WP310S |
Butt-weld fittings |
| ASTM A276 / A479 |
Bar, rod, forging stock |
| EN 1.4845 |
European equiv. |
HT PIPE Supply — Stainless Steel 310S Product Forms
HT PIPE supplies 310S in pipe, flanges, fittings, plate, and bar for furnace and heat-treatment service, with MTRs and high-temperature data.
Project Experience — Stainless Steel 310S
HT PIPE supplies 310S for welded furnace, radiant-tube, and petrochemical high-temperature components.
| Project |
Product |
Specification |
| Heat-Treatment Furnace Radiant Tubes (China) |
310S Pipe + Fittings |
A312, A403 |
| Kiln & Burner Hardware (Europe) |
310S Flanges + Plate |
A182 F310S, A240 |
| Refinery Thermowells (Middle East) |
310S Bar + Forgings |
A276, A182 |
We advise 310 vs 310S and provide high-temperature allowable-stress data.
| FREQUENTLY ASKED QUESTIONS |
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FAQ — Stainless Steel 310S
| What is the difference between 310S and 310? |
| 310S limits carbon to 0.08% versus up to 0.25% for 310. 310S is the welded-fabrication grade because it avoids sensitization; 310 is stronger and more carburization-tolerant but embrittles more easily. |
| What temperature can 310S withstand? |
| About 1150°C continuous in air, 1035°C intermittent. It is the highest oxidation-resistant of the common austenitic stainless grades before nickel alloys. |
| Can 310S replace 316 at high temperature? |
| Yes, in the 650–900°C band where 316 risks sigma-phase embrittlement, 310S is the more reliable choice even though its room-temperature strength is similar. |
| Is 310S resistant to seawater? |
| No. It has no molybdenum (PREN ~25) and pits in chlorides. It is a dry high-temperature grade. |
| What filler is used for 310S? |
| ER310 or ER309 (over-alloyed) for matching/over-matching deposits. Plain 308/316 fillers lack the chromium-nickel level and should be avoided. |
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Need Stainless Steel 310S for High-Temperature Service?
HT PIPE supplies 310S (UNS S31008) pipe, flanges, fittings, plate, and bar for furnace and heat-treatment applications to 1150°C. Contact our technical team for grade and welding advice.
Request a Quote |
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