What is 1.4568 stainless steel equivalent to?

1.4568 stainless steel, commonly known as 631 or 17-7PH (UNS S17700), is a semi-austenitic precipitation-hardening stainless steel. It is known for its unique ability to be formed in a soft, ductile condition and then heat-treated to achieve very high strength and hardness, along with good corrosion resistance. This makes it ideal for aerospace springs, high-stress fasteners, and medical instruments.

 

What is 1.4568 stainless steel equivalent to?

1.4568 stainless steel (also known as 17-7PH, AISI 631, or X7CrNiAl17-7) is a semi-austenitic precipitation-hardening alloy renowned for high strength, excellent fatigue resistance, and good corrosion resistance. It is commonly used in aerospace, springs, and medical instruments because it can be formed in a soft state and hardened at low temperatures.

 

This versatile precipitation-hardening grade is standardized under key international systems.

Standard	Equivalent Grade
EN (Europe)	1.4568
ASTM/AISI (USA)	631, 17-7PH, UNS S17700
JIS (Japan)	SUS631

 

Its composition includes aluminum for age-hardening.

Element	C	Si	Mn	Cr	Ni	Al
Content (%)	≤ 0.09	≤ 1.0	≤ 1.0	16.0 - 18.0	6.5 - 7.75	0.75 - 1.50

 

Mechanical properties vary dramatically with heat treatment condition.

Condition	Yield Strength (Rp0.2)	Tensile Strength (Rm)	Elongation (A)	Hardness (HRC)
Condition A (Annealed)	~ 380 MPa	~ 1030 MPa	~ 20%	~ 28 HRC
Condition C (TH1050)	~ 1030 MPa	~ 1240 MPa	~ 7%	~ 40 HRC

 

Key Characteristics and Applications of 1.4568 / 17-7PH

High Strength with Good Ductility: Can achieve tensile strengths over 1200 MPa after precipitation hardening while retaining useful ductility.

Excellent Fatigue and Spring Properties: Widely used for springs, diaphragms, and other components requiring high fatigue resistance and elastic properties.

Good Corrosion Resistance: Comparable to Type 304 stainless steel, making it suitable for applications requiring both strength and moderate corrosion resistance.

 

Primary Applications:

Aerospace: Bellows, springs, fasteners, and structural components.

Medical: Surgical instruments, orthopedic implants, and dental tools.

Chemical Processing: Valve parts and pump components requiring strength and corrosion resistance.

Precision Instruments: Critical components requiring dimensional stability and high strength.

 

What is the typical heat treatment sequence for 17-7PH (1.4568)?
The most common treatment is the TH1050 condition. First, the material is solution treated at 1040°C and cooled rapidly (Condition A). It is then conditioned by heating to 760°C, holding, and cooling to room temperature within 1 hour. Finally, it is age hardened at 565°C for 90 minutes. This sequence transforms the austenitic structure to martensitic and then precipitates hardening phases, achieving high strength. Different conditioning and aging temperatures produce various strength levels.

 

 

Looking for a Reliable Supplier of 1.4568 / 17-7PH Stainless Steel?
GNEE Steel supplies high-performance 17-7PH (1.4568) stainless steel in strip, wire, bar, and sheet forms, available in various heat-treated conditions to meet specific mechanical requirements. We provide full material certification and processing support. If you have any requirements, please feel free to contact us.