631 Stainless Steel
Alias: 0Cr17Ni7Al
Gloss: Bright and transparent
Transparency: Opaque
Hardness: Solid solution, ≤229HB; Age hardening at 565°C, ≥363HB; Age hardening at 510°C, ≥388HB
Application: Widely used in hardware kitchenware, shipbuilding, petrochemical, machinery, food, electricity, energy, etc.
Standard: GB/T 1220-1992
Chinese Number: 07Cr17Ni7Al
Hardness: Half-austenitic 613
Chemical Formula: 0Cr17Ni7Al
Specification: Forgings, bars, plates, strips, etc.
Origin: Japan Metallurgy/SMC/VDM/ATI
Basic Information
Standard: GB/T 1220-2007
631, equivalent to China's 0Cr17Ni7Al, is a semi-austenitic precipitation-hardening stainless steel. It is an austenitic unstable stainless steel, which is in an austenitic structure at room temperature. After cold working, cold treatment, or heating to around 750 degrees for adjustment, the austenite can transform into martensite. Further aging treatment allows for the precipitation of a second phase on the martensite matrix, thereby strengthening the steel. The role of aluminum is to form precipitation-hardening phases like (Ni3Al) with other elements. During the aging process, cooling must not be rapid, as it is difficult to achieve the desired strengthening effect otherwise.
Chemical Composition
Carbon (C): ≤0.09 Silicon (Si): ≤1.00
Manganese (Mn): ≤1.00
Sulfur (S): ≤0.030
Phosphorus P: ≤0.035
Chromium (Cr): 16.00～18.00
Nickel (Ni): 6.50～7.75
Copper Cu: ≤0.50
Aluminum: 0.75～1.50
Mechanical properties
Tensile Strength σb (MPa): Solution treated, ≤1030; Age hardened at 565°C, ≥1140; Age hardened at 510°C, ≥1230
Condition yield strength σ0.2 (MPa): Solution treated, ≤380; Age-hardened at 565°C, ≥960; Age-hardened at 510°C, ≥1030
δ5 elongation (%): Solution treated, ≥20; Age hardened at 565°C, ≥5; Age hardened at 510°C, ≥4
Section shrinkage rate ψ (%): Age-hardened at 565℃, ≥25; age-hardened at 510℃, ≥10
Hardness: Solution treated, ≤229HB; Age-hardened at 565°C, ≥363HB; Age-hardened at 510°C, ≥388HB
Heat Treatment Editing
Solution treated, quenched at 1000-1100°C.
2) Ageing at 565°C, followed by solution heat treatment at 760±15°C for 90 minutes, then cool to below 15°C within 1 hour and hold for 30 minutes, further heat to 565±10°C for 90 minutes, air cool.
3) 510°C aging, after solution heat treatment, hold at 955±10°C for 10 minutes, air cool to room temperature, and cool to -73±6°C within 24 hours, hold for 8 hours, then reheat to 510±10°C and maintain for 60 minutes, air cool.
