SUS304H Stainless Steel

SUS304H is a high-carbon austenitic stainless steel (C=0.04-0.10) designed for high-temperature strength. Higher carbon improves creep resistance at 500-800°C, making it suitable for high-heat industrial applications where SUS304's strength is insufficient.

Chemical Composition (wt%): C=0.04-0.10, Si ≤1.00, Mn ≤2.00, P ≤0.045, S ≤0.030, Cr=18.00-20.00, Ni=8.00-10.50, Fe=Balance

Mechanical Properties: Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness (HB) ≤201

Performance Advantages: Excellent high-temperature creep resistance; good oxidation resistance at 800°C; better high-temp strength than SUS304; weldable with proper filler metal.

Equivalent Grades: ASTM A240 304H, EN 1.4307, UNS S30409

Applications: High-temperature pipelines, boiler superheater tubes, furnace parts, heat exchanger tubes in power plants, chemical reactor internals.

FAQ

1. Q: Why is SUS304H suitable for high-temperature applications? A: Its 0.04-0.10% carbon enhances high-temp strength via solid solution strengthening. At 500-800°C, carbon atoms pin grain boundaries, resisting creep (permanent deformation under constant load). SUS304 (lower C) creeps easily at high temps, while SUS304H maintains shape. It also forms a dense Cr-rich oxide layer, resisting oxidation at 800°C, suitable for furnace or boiler parts.

2. Q: How to avoid intergranular corrosion in SUS304H welding? A: Use low-carbon filler metal (ER308H) to match carbon content. Control heat input (100-150A for TIG) to reduce welding zone residence time. Avoid multi-pass welding without cooling. Post-weld annealing at 1050-1100°C and rapid cooling can dissolve chromium carbides, restoring corrosion resistance. For critical parts (boiler tubes), NDT testing ensures no cracks or carbide precipitation.

3. Q: What's the maximum operating temperature of SUS304H? A: It works continuously at up to 870°C. Below 870°C, it retains creep resistance and oxidation resistance. Short-term use can reach 925°C but may reduce service life. Above 870°C, its austenite structure becomes unstable, and strength drops sharply. For temps over 900°C, choose SUS310S (higher Cr/Ni) for better high-temp performance.

4. Q: How does SUS304H compare to SUS304 and SUS316H? A: vs SUS304: SUS304H has higher high-temp strength and creep resistance, but similar room-temp properties. vs SUS316H: SUS316H has Mo (2-3%), better corrosion resistance in high-temp chemicals, but higher cost. SUS304H is cost-effective for high-temp, non-aggressive environments (air, steam), while SUS316H suits high-temp acidic/alkaline conditions.

5. Q: Can SUS304H be used in low-temperature environments? A: It's not recommended. Its higher carbon reduces low-temp toughness. At -40°C or below, it may become brittle, risking fracture under impact. SUS304L (low C) has better low-temp toughness, suitable for cryogenics. SUS304H is designed for high temps; using it in low temps wastes its advantages and poses safety risks, so material selection should match operating conditions.