SUS631
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SUS631 is a martensitic precipitation-hardening stainless steel in the Japanese JIS standard, corresponding to 17-7PH in the American standard. It features high strength, good corrosion resistance, and excellent formability, and is widely used in aerospace, precision instruments, chemical engineering, and other fields.
Product name：
Straight seam submerged arc welding
Material：
Q355B
Warehouse：
Tianjin
Surface treatment：
Hot rolling
Category：
Keyword：
SUS631
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Details description
Chemical Composition
Main Element Content (Mass Fraction, %):
Carbon (C) ≤0.09
Chromium (Cr) 16.00 - 18.00
Nickel (Ni) 6.50 - 7.75
Aluminum (Al) 0.75 - 1.50
Manganese (Mn) ≤1.00
Silicon (Si) ≤1.00
Phosphorus (P) ≤0.040
Sulfur (S) ≤0.030
Iron (Fe) Balance
Its core alloy design uses chromium to ensure corrosion resistance, nickel to stabilize austenite, and aluminum as a precipitation hardening element, forming a strengthening phase after aging treatment.
Physical Properties
Density: 7.80 g/cm³
Melting Point: 1410 - 1450℃
Thermal Conductivity: 15.1 W/(m・K) (Room Temperature)
Specific Heat Capacity: 460 J/(kg・K) (Room Temperature)
Coefficient of Thermal Expansion: 11.0 × 10⁻⁶ /℃ (20 - 100℃)
Elastic Modulus: 200 GPa (Room Temperature)
Magnetic Properties: The solid solution is austenitic and weakly magnetic; after aging treatment, it transforms into martensite, and the magnetism increases.
Mechanical Properties
Properties can be adjusted through different heat treatment processes. Typical room temperature mechanical properties are as follows (using the commonly used aging state as an example):
H900 State (Solution + 480℃ Aging):
Tensile Strength: ≥1450 MPa
Yield Strength: ≥1310 MPa
Elongation: ≥6%
Hardness: ≥45 HRC
H1150 State (Solution + 620℃ Aging):
Tensile Strength: ≥1030 MPa
Yield Strength: ≥860 MPa
Elongation: ≥15%
Hardness: ≥30 HRC
Excellent low-temperature toughness and stable strength at high temperatures (≤315℃).
Corrosion Resistance
Corrosion resistance is superior to ordinary martensitic stainless steel (such as 410) and is close to that of 304 austenitic stainless steel.
It has good resistance to atmosphere, fresh water, seawater, steam, and mildly oxidizing media (such as nitric acid).
It has strong resistance to pitting and crevice corrosion, but should be used cautiously in high concentrations of chloride ions or reducing acids.
After appropriate heat treatment, the susceptibility to stress corrosion cracking can be reduced.
Processing and Heat Treatment Properties
1. Machinability
2. Cold Working: Good plasticity in the solution-treated (softened) state, allowing for stamping, bending, cold rolling, etc.; after aging hardening, the hardness increases, and the processing difficulty increases.
Hot Working: Suitable temperature is 980 - 1150℃. After hot working, rapid cooling (such as water quenching) is required to avoid embrittlement.
Cutting Performance: Moderate cutting performance in the solution-treated state; in the aged state, due to increased hardness, hard alloy tools are required.
3. Heat Treatment Process
4. Solution Treatment: Heating at 1000 - 1050℃, holding, and water quenching to obtain a supersaturated solid solution (austenitic structure, hardness approximately 28 HRC).
Aging Treatment: The temperature is selected according to the performance requirements. Common processes include:
H900: 480℃ for 1 hour, air cooling (high strength, low toughness).
H1050: 565℃ for 1 hour, air cooling (balanced strength and toughness).
H1150: 620℃ for 1 hour, air cooling (high toughness, moderate strength).
During the aging process, precipitation hardening is achieved by the formation of intermetallic compounds (such as Ni₃Al) from aluminum and nickel.
5. Weldability
6. Gas tungsten arc welding (TIG) and arc welding can be used. Solution treatment is required before welding to reduce the risk of cracking. Aging treatment is recommended after welding to restore mechanical properties; avoid prolonged stays in the 595 - 705℃ range to prevent intergranular corrosion.
Application Fields
Aerospace: Aircraft skins, landing gear components, engine parts, missile structural components, etc.
Precision Instruments: Springs, bellows, sensor components, lens mounts, etc.
Chemical Industry: Valves, pump bodies, heat exchanger components, corrosion-resistant fasteners.
Others: Medical devices (such as surgical forceps), marine engineering, food processing equipment, etc.
Delivery Condition
Plates/Strips: Solution treated, pickled, cold-rolled or hot-rolled, and the surface can be polished.
Bars/Wires: Solution-treated, aged, or cold-drawn, with black skin, polished, or turned surfaces.
The core advantage of SUS631 is its flexibility in adjusting strength and toughness through heat treatment, while also possessing high corrosion resistance. It is especially suitable for high-end fields with stringent material performance requirements.
Qualification certification
Corporate video
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Application fields
Petrochemicals
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Aerospace
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Energy equipment
Energy equipment
Oil/gas/water pipelines
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Building construction
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Dredging & piling works
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FAQ
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