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Should I choose SS 309S or SS 310S for furnace parts?
Short answer
Choose SS 310S for the hottest zones and severe thermal cycling, because its 25% chromium and 20% nickel resist oxidation up to about 1,100 °C. Choose SS 309S for moderately hot parts up to about 1,000 °C, where its lower nickel saves cost.
SS 310S vs SS 309S at a glance
| Property | SS 310S | SS 309S |
|---|---|---|
| UNS | S31008 | S30908 |
| EN | 1.4845 | 1.4833 |
| Family | Heat-resisting austenitic stainless steel | Heat-resisting austenitic stainless steel |
| C (%) | 0.08 max | 0.08 max |
| Cr (%) | 24.0 – 26.0 | 22.0 – 24.0 |
| Ni (%) | 19.0 – 22.0 | 12.0 – 15.0 |
| Tensile strength | 515 MPa (75 ksi) | 515 MPa (75 ksi) |
| Yield strength | 205 MPa (30 ksi) | 205 MPa (30 ksi) |
| PREN | — | — |
| Density | 7.9 g/cm³ | 7.9 g/cm³ |
| Magnetic | Non-magnetic when annealed. | Non-magnetic when annealed. |
| Typical use | Furnace components, hearths and dampers | Furnace linings, doors and dampers |
Which should you choose?
There's no universal "winner": the right choice depends on service conditions, codes and cost. Share your conditions with us for a recommendation.
Atmosphere changes the answer
Other heat-resisting options
Products in both grades
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Frequently asked questions
What does the S mean in SS 309S and SS 310S?
It denotes a low-carbon version (0.08% max) that is easier to weld. The H versions have higher carbon for creep strength.
Which specification covers SS 310S plate?
ASTM A240, UNS S31008.
What is the main difference between SS 310S and SS 309S?
SS 310S (25Cr-20Ni) resists oxidation to about 1,100 °C, while SS 309S (23Cr-13Ni) reaches about 1,000 °C at lower cost. SS 310S handles thermal cycling and hotter zones better.
When should I choose SS 309S?
Moderately hot furnace parts where cost matters.
When should I choose SS 310S?
Hotter zones and severe cycling.
Can SS 310S replace SS 309S?
Only when the design, code and specification allow it. Strength, corrosion resistance and temperature limits differ, so substitution must be approved by the design authority.