AISI 631 / EN X7CrNiAl17-7 1.4568 / JIS SUS631 Stainless Steel

631 stainless steel is a type of precipitation-hardening (PH) stainless steel, known for its high strength, excellent corrosion resistance, and good mechanical properties. Due to its ability to be hardened through heat treatment, along with its durability and resistance to oxidation, it is widely used in aerospace, chemical processing, and high-performance engineering applications. You could find the equivalent from different steel standard, such as: X7CrNiAl17-7/1.4568 from Europe standard EN 10088-3, 07Cr17Ni7Al/0Cr17Ni7Al from China standard GB/T 1220, SUS631 from Japan standard JIS G4303, 09X17H7Ю from Russia standard GOST 5632-72.

1: Steel equivalent

2: Chemical composition

3: Mechanical properties

Mechanical properties for 07Cr17Ni7Al/0Cr17Ni7Al from standard GB/T1220 and SUS631 from JIS G4303.

Mechanical properties for X7CrNiAl17-7/1.4568 from standard EN10088-3.

AT=Solution annealed

4: Supply size & Tolerance & Stock size

Qilu steel stock hot rolled bar and forged bars more than ten thousands tons every month, below our our stock size.

1): Stock diameter for hot rolled bar

2) : Stock diameter for hot forged bar

Since the stocks change everyday, if you want to know our stock available information, please contact our salesman.

5: Ultrasonic Test

EN10228-3 class III or Sep 1921-84 D/D

6：Steel making & Forging processing

1): Steel making process:

  EF+LF+VD

  EAF+LF+VD

  EF+LF+VD+ESR

  EAF+LF+VD+ESR

2): Forging processing:

Hot forging temperature: 900-1150℃

Cooling in the air

7: Heat treatment  

Solution Annealing

1) Heat 631 steel to 1000-1100℃ in the furnace

Quick cool in the air/water

2) Precipitation hardening to 510℃

After solution treatment, heat to 955°C ± 10°C, hold for 10 minutes, then air cool to room temperature. Within 24 hours after solution treatment, cool to -73°C ± 6°C, maintain for 8 hours. Reheat to 510°C ± 10°C, hold for 1 hour, then cooling in the air.

3) Precipitation hardening to 565℃

After solution treatment, heat to 760°C ± 15°C, hold for 90 minutes. Cool to below 15°C within 1 hour, then maintain for 30 minutes.  Reheat to 565°C ± 10°C, hold for 90 minutes, then cooling in the air.

8：Application

631 stainless steel is a precipitation hardening stainless steel, with high strength, excellent corrosion resistance, good mechanical properties and heat treatment strengthening ability. Its main application areas include:

1): Aerospace: aircraft parts, engine parts, missile and spacecraft structural parts, etc.

2): chemical and petroleum industries: corrosion-resistant valves, pump bodies and pipelines, high-stress parts in chemical equipment, salt spray corrosion-resistant parts in marine environments.

3): medical and precision instruments: surgical instruments, dental equipment, precision instrument springs and sensor components.

4): automotive and high-end manufacturing: high-performance automotive springs (such as suspension systems, clutch springs), high-strength fasteners (such as bolts, pins) and precision mechanical parts.

5): electronics and energy industry: semiconductor manufacturing equipment parts, nuclear power plant corrosion-resistant structural components.

6): military and shipbuilding industry: seawater corrosion-resistant parts for ships and high-strength structural parts for weapons.