SUS631 material Chemical composition, properties
Aug 15, 2025
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What is SUS631 material?
SUS631 (UNS S17700) is a precipitation-hardening stainless steel that can reach a hardness of HRC 40–48 after aging treatment. Its corrosion resistance surpasses that of ordinary martensitic stainless steels and approaches that of 304 stainless steel, passing the ASTM A262-E intergranular corrosion test. It also offers excellent precision formability, allowing cold working in the solution-treated condition (Condition A) and maintaining dimensional stability after aging (Condition H900). SUS631 is widely used in aerospace fasteners, precision springs, surgical instruments, and marine sensor components.
What is the equivalent of SUS631?
SUS631 is the Japanese Industrial Standard (JIS) designation for this precipitation-hardening stainless steel, also known as 17-7 PH (UNS S17700). It is equivalent to AISI 631 and EN 1.4568 (X7CrNiAl17-7).
What is the composition of AISI 631?
This versatile alloy contains approximately 17% chromium, 7% nickel, and 1% aluminum. It is easily formable in the soft austenitic condition and can then be hardened to a high-strength level through a simple low-temperature heat treatment, minimizing deformation.
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JIS G4304 SUS 631 Chemical Composition |
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Grade |
The Element Max (%) |
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C |
Si |
Mn |
P |
S |
Cr |
Ni |
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SUS 631 |
0.09 |
1.00 |
1.00 |
0.040 |
0.030 |
16.0-18.0 |
6.50-7.75 |
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Mo |
N |
Cu |
Others |
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Al: 0.75-1.50 |
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JIS G4304 SUS 631 plate Mechanical Property
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Grade |
JIS G4304 SUS 631 Mechanical Property |
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Yield |
Tensile |
Elongation |
Hardness, max |
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SUS 631 |
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Min Mpa |
Min Mpa |
Min % |
HBW |
HRC |
HRB |
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S |
380 Max |
1030 Max |
20 |
192 |
|
92 |
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RH950 |
1030 |
1230 |
4 |
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40 Min |
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TH1050 |
960 |
1140 |
3-5 Min |
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35 Min |
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SUS631 Stainless Steel – Available Product Forms
| Product Form | Typical Dimensions / Sizes | Surface Finish |
|---|---|---|
| Sheet / Plate | Thickness: 0.5 – 12 mm Width: 500 – 1500 mm |
2B / BA / Polished / Mirror |
| Coil / Strip | Thickness: 0.3 – 6 mm Width: 10 – 1500 mm |
2B / BA / Polished |
| Bar / Rod | Diameter: 3 – 50 mm | Polished / Ground |
| Wire | Diameter: 0.1 – 10 mm | Polished / Annealed |
| Tube / Pipe | OD: 6 – 50 mm Wall thickness: 0.5 – 3 mm |
Polished / BA |
| Forging / Custom Shapes | As per drawing | Machined / Polished |
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