17 7 PH stainless steel vs 316

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.

 

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.

 

17-7 PH stainless steel vs 316

17-7 PH stainless steel is a high-strength, precipitation-hardening alloy ideal for springs and aerospace components requiring fatigue resistance up to 600°F, while 316 stainless steel is an austenitic alloy optimized for superior corrosion resistance, particularly in marine or chloride environments. 17-7 PH offers better strength and hardness; 316 provides superior, reliable corrosion resistance.

 

How does 17-7PH compare to 17-4PH in terms of properties and applications?
Both are precipitation-hardening grades, but 17-7PH is semi-austenitic while 17-4PH is martensitic. 17-7PH generally offers better formability in the annealed condition and can achieve higher strength levels (especially in spring applications) with excellent fatigue resistance. 17-4PH typically has better machinability and is often chosen for complex machined parts. 17-7PH is preferred for thin sections and formed components like springs and bellows.

 

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.