SUS631 stianless steel Chemical composition, properties

What is sus 631 material?

SUS631 is the Japanese Industrial Standard (JIS) designation for 17-7 PH (precipitation-hardening) stainless steel. It is initially produced as a soft austenitic material and then hardened through low-temperature heat treatment with minimal deformation. This alloy contains approximately 17% chromium, 7% nickel, and aluminum, and is available in various forms such as foil, sheet, bar, and wire. With its excellent properties, it is an ideal material for aerospace components, springs, and medical devices.

 

What is SUS631 equivalent material?

SUS631 is a Japanese (JIS) designation for a precipitation-hardening stainless steel, and its direct equivalents in other standards are 17-7PH (American/ASTM), UNS S17700, and European EN 1.4568, all representing the same high-strength material used for springs, aerospace, and other demanding applications.

 

What is the composition of SS 631?

With approximately 17% chromium, 7% nickel, and 1% aluminum, this versatile alloy can be easily formed in its soft austenitic condition and subsequently hardened to high strength levels through a simple, low-temperature heat treatment process that minimizes distortion.

Grade	The Element Max (%)
	C	Si	Mn	P	S	Cr	Ni
SUS 631	0.09	1.00	1.00	0.040	0.030	16.0-18.0	6.50-7.75
	Mo	N	Cu	Others
				Al: 0.75-1.50

 

JIS G4304 SUS 631 Mechanical Property

Grade		JIS G4304 SUS 631 Mechanical Property
		Yield	Tensile	Elongation	Hardness, max
SUS 631		Min Mpa	Min Mpa	Min %	HBW	HRC	HRB
	S	380 Max	1030 Max	20	192		92
	RH950	1030	1230	4		40 Min
	TH1050	960	1140	3-5 Min		35 Min

 

What is SUS631 stainless steel properties?

SUS631 (also known as 17-7PH) is a precipitation-hardening stainless steel offering a great mix of high strength, hardness, good formability (in annealed state), and corrosion resistance, becoming strongly magnetic and very hard after low-temperature aging treatment, making it ideal for springs, fasteners, and aerospace components needing excellent fatigue strength.

High strength and hardness: After heat treatment, it achieves extremely high mechanical properties, superior to many standard stainless steels.
Corrosion resistance: Comparable to AISI 301, exhibiting good corrosion resistance in various environments.
Formability: Easily formed in the soft austenitic (solution-treated) state.
Magnetic properties: Non-magnetic in the annealed state, but becomes strongly magnetic after precipitation hardening.

 

SUS631 Material Heat Treatment
Solution Treatment (Annealing): Heat to about 1050°C (1925°F) and rapidly cool to achieve a soft, austenitic (soft, formable) state, allowing for deep drawing or complex forming.
Cold Working (C-Treatment): Cold rolling/forming.
Precipitation Hardening (Aging): Heat to specific aging temperatures for final hardening:
H950 (RH950): ~510°C (950°F) for 60 mins, then air cool, for high strength.
H1050 (TH1050): ~565°C (1050°F) for 90 mins, then air cool, for high strength.
CH900: ~475°C (900°F) for 60 mins, then air cool, for maximum strength but reduced ductility.

 

Main Applications:

- Aerospace: Used in aircraft structural components, springs, and fasteners.

- Automotive Industry: Employed in automotive suspension components and engine parts.

- Medical Devices: Utilized in medical instruments, surgical tools, and implants.

- Precision Engineering: Found in precision shafts, gears, and valve components.

- Marine Engineering: Used in marine hardware, shafts, and propeller shafts.

 

GNEE is a trusted supplier of precipitation-hardening stainless steel and specialty alloys in China. We supply 17-4 PH, 15-5 PH, and 17-7 PH alloys in various forms including bars, plates, profiles, and forgings. All products are sourced from certified steel mills and undergo rigorous chemical composition and mechanical property testing to ensure reliable quality.
Whether you are in the aerospace, oil and gas, marine engineering, or defense industry, we ensure that every batch of our products meets international standards and your specific application requirements.
Click here to view our complete range of precipitation-hardening alloys: PH Alloys.