Hangbo Alloy Group supplies a variety of 631 stainless steel (also known as 17-7PH) products, including round bars, plates, strips, seamless tubes, forgings, and wires. Below is a comprehensive description of 631 stainless steel.
1.Introduction to 631/17-7PH
Description: 631 (UNS S17700) is a precipitation-hardening martensitic stainless steel, mainly composed of chromium, nickel, and aluminum. It is renowned for ultra-high strength (achieved via precipitation hardening heat treatment), excellent low-temperature toughness, and good corrosion resistance. It maintains stable mechanical properties in a wide temperature range (from -200°C to 315°C) and offers diverse performance options via different heat treatment states (e.g., RH950, TH1050). Its balance of high tensile strength (1100-1400 MPa after aging) and good formability makes it ideal for applications requiring high strength, corrosion resistance, and fatigue resistance.
International Equivalents:
USA: UNS S17700, ASTM 631 (17-7PH)
CHINA: 07Cr17Ni7Al (per GB/T 20878 standard)
Europe: EN 1.4568, DIN X7CrNiAl17-7
2.Standards for 631/17-7PH
Plates: ASTM A693/A693M, GB/T 4237, EN 10088-2
Round Bars: ASTM A564/A564M, GB/T 1220, EN 10088-3
Seamless Tubes: ASTM A789/A789M, GB/T 14976, EN 10216-5
Forgings: ASTM A705/A705M, GB/T 1221, EN 10222-5
3.Chemical Composition of 631/17-7PH
| Element | Content (%) |
|---|---|
| Carbon (C) | ≤ 0.09 |
| Chromium (Cr) | 15.0-17.5 |
| Nickel (Ni) | 3.0-5.0 |
| Silicon (Si) | ≤ 1.00 |
| Manganese (Mn) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.04 |
| Sulfur (S) | ≤ 0.03 |
| Iron (Fe) | Balance |
| Aluminum(Al) | 0.75-1.50 |
4.Physical Properties of 631/17-7PH
| Property | Value | |
|---|---|---|
| Density | 7.67 g/cm³ | |
| Melting Range | 1415-1450 °C | |
5.Material Characteristics of 631/17-7PH
Ultra-High Mechanical Strength: After precipitation hardening (aging treatment), it exhibits ultra-high tensile strength (1100-1400 MPa) and yield strength (950-1200 MPa), exceeding most austenitic stainless steels and even some 630 stainless steel grades.
Excellent Low-Temperature Toughness: Maintains good toughness at temperatures as low as -200°C, avoiding brittle fracture in low-temperature environments (a key advantage over conventional martensitic stainless steels).
Good Corrosion Resistance: Resists atmospheric corrosion, fresh water, and weak corrosive media (e.g., dilute acids, alkalis); performance is comparable to 304 stainless steel in mild environments, suitable for non-severe corrosion scenarios.
Diversified Heat Treatment States: Different aging temperatures produce distinct performance states (e.g., RH950 for high strength, TH1050 for better ductility), adapting to diverse application requirements.
Controllable Formability: In the solution-annealed (soft) state, it has good cold working performance (e.g., bending, stamping, coiling); after aging, hardness increases significantly, limiting secondary processing—ideal for pre-forming then strengthening.
6.Applications of 631/17-7PH
Aerospace & Aviation: Widely used in aircraft structural components (e.g., fasteners, brackets), engine springs, and missile guidance system parts; high strength and low-temperature toughness meet extreme aerospace environment requirements.
Spring & Elastic Components: Applied to high-performance springs (e.g., aircraft landing gear springs, chemical equipment pressure springs) and elastic fasteners; excellent fatigue resistance and strength ensure long service life.
Chemical & Petrochemical Industry: Used in high-pressure valves, pump shafts, and pipeline connectors; resists corrosion from oilfield/media and maintains strength under high pressure and cyclic loads.
Medical Equipment: Employed in high-strength medical springs (e.g., surgical instrument springs, implantable elastic components) and low-temperature storage equipment parts; biocompatibility and corrosion resistance meet medical standards.
Precision Machinery: Used in precision mold cores, high-strength gears, and instrument structural parts; high dimensional stability and strength ensure precision operation of mechanical systems.
