S31008 Stainless Steel

S31008 is a premium high-temperature austenitic stainless steel (UNS S31008), corresponding to SUS310S. With 24-26% Cr and 19-22% Ni, it's the top choice for ultra-high-temperature service (1000-1200°C), offering exceptional oxidation and creep resistance in harsh industrial environments.

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%, Hardness (HB) ≤217

Performance Advantages: Excellent oxidation resistance up to 1200°C; superior creep resistance at 800-1100°C; high thermal shock resistance; resists high-temp corrosive gases.

Equivalent Grades: ASTM A240 310S, EN 1.4845, SUS310S

Applications: Industrial furnace cores, jet engine exhaust components, incinerator linings, nuclear power high-temp heat exchangers, high-temperature gas turbine parts.

FAQ

1. Q: What makes S31008 resistant to 1200°C? A: Its high Cr/Ni content forms a dense Cr₂O₃-NiO composite oxide layer at 1200°C, blocking oxygen penetration. High Ni stabilizes the austenitic structure, preventing brittle sigma phase formation. The alloy's grain boundaries resist creep (permanent deformation) under 1100°C load-at 1100°C and 50MPa, its creep rupture time exceeds 10,000 hours, far longer than S30908.

2. Q: Can S31008 handle waste incinerator environments? A: Yes, it's ideal. Incinerators operate at 1000-1100°C with flue gas containing acid (HCl, SO₂) and particulate matter. S31008's oxide layer resists acid corrosion, and its high-temp strength withstands ash erosion. It outperforms S30908 here, lasting 8-10 years vs 3-5 years, justifying its higher cost for incinerator linings.

3. Q: What welding issues should be noted for S31008? A: High Ni increases weld pool viscosity-use higher heat input (150-200A for TIG) and slower travel speed. Use ER310 filler to match Cr/Ni; ER309 filler reduces high-temp performance. Preheat 150-200°C for plates ≥20mm to prevent cold cracking. Post-weld anneal at 1050-1100°C to relieve stress, critical for furnace cores under thermal cycles.

4. Q: How to distinguish S31008 from S30908? A: Chemical analysis is reliable-S31008 has Ni≥19% and Cr≥24%, S30908 has Ni≤15% and Cr≤24%. For on-site checks, use a high-temp test: heat samples to 1150°C for 1 hour-S31008 has minimal scaling, S30908 shows noticeable oxidation. Always verify material certificates for critical applications.

5. Q: Is S31008 cost-effective vs nickel-based alloys? A: Yes, for 1000-1200°C service. Inconel 600 (Ni≥72%) costs 3x more than S31008 but offers similar performance in oxidizing environments. S31008 is the most cost-effective choice for industrial ultra-high-temp equipment. Only use Inconel for reducing atmospheres or temps above 1200°C where S31008's oxidation resistance declines.