310S Stainless Steel: Top-Tier Material for Extreme High Temperatures

310S is the "top-tier" grade of high chromium-nickel austenitic stainless steel (Cr=24%-26%, Ni=19%-22%), featuring extreme high-temperature oxidation resistance and creep strength. It can be used for long-term service at 1000-1200℃, serving as the "last line of defense" material in ultra-high-temperature industrial environments.

Core Parameters

Chemical Composition (wt%): C≤0.08, Si≤1.50, Mn≤2.00, P≤0.045, S≤0.030, Cr=24.00-26.00, Ni=19.00-22.00, Fe=Balance

Mechanical Properties (Annealed): Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Brinell Hardness ≤217HB

Service Temperature: 1000℃ to 1200℃ (continuous service), up to 1300℃ for short-term service

Equivalent Grades: SUS310S (JIS), EN 1.4845 (EN), UNS S31008 (ASTM)

Performance Advantages: The Cr₂O₃-NiO composite oxide film remains stable even at 1200℃, with an oxidation rate ≤0.1mm/year; the creep rupture time at 1100℃ is 3 times that of 309S; excellent corrosion resistance to high-temperature sulfides and chlorides; good high-temperature toughness, with impact toughness ≥50J at 1000℃.

Typical Applications: Core furnace tubes of industrial furnaces, jet engine exhaust components, linings of the high-temperature section of waste incinerators, high-temperature heat exchangers in nuclear power plants, high-temperature molten salt storage tanks.

Practical Q&A

Q1: Can 310S withstand short-term ultra-high temperature of 1300℃? A1: Yes, but the residence time must be ≤10 hours. At 1300℃, the steel will soften slightly, with strength reduced by 50%, and the oxidation rate will accelerate to 0.5mm/year. Long-term service will lead to material thinning and failure.

Q2: What is the biggest difficulty in welding 310S? A2: The high nickel content increases the viscosity of the weld pool, making incomplete fusion defects prone to occur. It is necessary to use large current (150-200A for TIG welding) and slow welding speed to ensure full penetration; select ER310 welding wire, and perform annealing at 1050-1100℃ after welding to eliminate welding stress.

Q3: What are the advantages of 310S compared with nickel-based alloy Inconel 600? A3: Its cost is only 1/3 of Inconel 600, and its oxidation performance is equivalent below 1200℃; it has better weldability than Inconel 600, without the need for preheating and complex post-treatment. Inconel 600 has better performance above 1200℃ or in strong reducing atmospheres.

Q4: Will 310S suffer from sigma phase embrittlement? A4: Sigma phase will precipitate when staying at 800-1000℃ for a long time (≥100 hours), reducing the impact toughness to ≤10J. It is necessary to strictly control the heating/cooling rate and avoid long-term heat preservation in this temperature range; if sigma phase has precipitated, it can be eliminated by annealing at 1100℃ and rapid cooling.

Q5: Is 310S suitable for high-pressure ultra-high-temperature equipment? A5: Yes, but the pressure must be controlled. The allowable working pressure is ≤10MPa at 1000℃ and ≤2MPa at 1200℃. Thickened pipe walls or composite structures should be adopted in the design, and strict non-destructive testing (such as ultrasonic + radiographic testing) should be carried out to ensure no internal defects.