17-7PH Stainless Steel Round Bar
Grade: 631/17-7PH/UNS S17700
Size:
Cold drawn: φ4mm-φ60mm
Hot Rolled: φ16mm-φ230mm
Forged: φ230mm-φ1200mm
Surface Finish: Black Annealed, Polished Bright, Centerless Grinding
Diameter Tolerance: H9, H11, h9, h11 etc
- Fast Shipping / Ready Stock
- ISO 9001 Direct Factory
- Custom Cutting & Processing
- 100% MTC & SGS Inspection Supported
631 stainless steel, commonly known as 17-7PH stainless steel, is a precipitation-hardening semi-austenitic stainless steel grade designated as UNS S17700. It was developed to provide a combination of high strength, excellent fatigue resistance, good corrosion resistance, and superior dimensional stability. The alloy contains approximately 17% chromium and 7% nickel, with aluminum additions that enable precipitation hardening after appropriate heat treatment.
17-7PH stainless steel differs from conventional martensitic stainless steels because its high strength is achieved through precipitation hardening rather than high carbon content. The material is initially supplied in an austenitic condition after solution treatment and is transformed into a martensitic structure through conditioning treatment before aging. During aging, aluminum-rich precipitates form within the matrix, significantly increasing strength and hardness while maintaining good corrosion resistance.
631 stainless steel bars offer excellent spring properties, high fatigue strength, and good resistance to distortion during heat treatment. Compared with 17-4PH stainless steel, 17-7PH provides better spring performance and dimensional stability, making it especially suitable for precision components exposed to repeated loading and vibration. The material maintains useful mechanical properties at moderately elevated temperatures.
17-7PH stainless steel bars are widely used in aerospace components, springs, diaphragms, washers, pressure sensors, valve components, chemical equipment, and precision mechanical parts. It is particularly suitable for applications requiring high strength, corrosion resistance, and long-term reliability under cyclic loading conditions.
ASTM / JIS / EN Standards
| Standard System | Standard / Grade | Description |
| ASTM | ASTM A564 / A564M – UNS S17700 | Wrought Precipitation-Hardening Stainless Steel Bars |
| ASTM | ASTM A693 – UNS S17700 | Precipitation-Hardening Stainless Steel Plate, Sheet and Strip |
| ASTM | ASTM A276 / A276M – UNS S17700 | Stainless Steel Bars and Shapes |
| UNS | S17700 | 17-7PH Stainless Steel Grade |
| JIS | JIS G4303 SUS631 | Stainless Steel Bars |
| EN | EN 10088-3 1.4542 (Comparable PH Family) | Precipitation Hardening Stainless Steel |
| DIN | DIN 1.4568 | X7CrNiAl17-7 Stainless Steel |
Stainless Steel Bar Execution Standards
| Item | Specification |
| Product Type | Round Bar, Square Bar, Hexagonal Bar |
| Manufacturing Process | Hot Rolled, Cold Drawn, Peeled, Ground, Polished |
| Heat Treatment | Solution Treatment + Conditioning + Aging |
| Solution Treatment | Approximately 950–970°C followed by rapid cooling |
| Conditioning Treatment | C or R Condition (Martensitic Transformation) |
| Aging Treatment | RH950, TH1050, CH900 Conditions |
| Surface Condition | Bright Surface, Ground Surface, Polished Surface |
| Dimensional Tolerance | According to ASTM A564 / ASTM A276 |
| Inspection | Chemical Analysis, Mechanical Testing, Hardness Testing, Dimensional Inspection |
| Supply Condition | Solution Treated, Cold Worked, Age Hardened |
Chemical Composition (%)
| Element | Composition Requirement |
| Carbon (C) | ≤ 0.09 |
| Silicon (Si) | ≤ 1.00 |
| Manganese (Mn) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.040 |
| Sulfur (S) | ≤ 0.040 |
| Chromium (Cr) | 16.00 – 18.00 |
| Nickel (Ni) | 6.50 – 7.75 |
| Aluminum (Al) | 0.75 – 1.50 |
| Iron (Fe) | Balance |
Mechanical Properties
Typical Aging Conditions
| Property | RH950 Condition | TH1050 Condition |
| Tensile Strength | ≥ 1240 MPa | ≥ 930 MPa |
| Yield Strength (0.2% Offset) | ≥ 1035 MPa | ≥ 725 MPa |
| Elongation | ≥ 5% | ≥ 10% |
| Hardness | Approx. 38–44 HRC | Approx. 28–35 HRC |
| Condition | Age Hardened | Age Hardened |
| Industry | Applications |
| Aerospace Industry | Aircraft structural parts, fasteners, springs |
| Spring Manufacturing | High-performance springs, clips, retaining rings |
| Precision Engineering | Diaphragms, sensors, precision components |
| Chemical Industry | Corrosion-resistant equipment components |
| Valve Industry | Valve springs, pressure control components |
| Automotive Industry | High-strength spring components |
| Mechanical Engineering | Fatigue-resistant mechanical parts |
631 stainless steel, commonly known as 17-7PH stainless steel, is a precipitation-hardening semi-austenitic stainless steel grade designated as UNS S17700. It was developed to provide a combination of high strength, excellent fatigue resistance, good corrosion resistance, and superior dimensional stability. The alloy contains approximately 17% chromium and 7% nickel, with aluminum additions that enable precipitation hardening after appropriate heat treatment.
17-7PH stainless steel differs from conventional martensitic stainless steels because its high strength is achieved through precipitation hardening rather than high carbon content. The material is initially supplied in an austenitic condition after solution treatment and is transformed into a martensitic structure through conditioning treatment before aging. During aging, aluminum-rich precipitates form within the matrix, significantly increasing strength and hardness while maintaining good corrosion resistance.
631 stainless steel bars offer excellent spring properties, high fatigue strength, and good resistance to distortion during heat treatment. Compared with 17-4PH stainless steel, 17-7PH provides better spring performance and dimensional stability, making it especially suitable for precision components exposed to repeated loading and vibration. The material maintains useful mechanical properties at moderately elevated temperatures.
17-7PH stainless steel bars are widely used in aerospace components, springs, diaphragms, washers, pressure sensors, valve components, chemical equipment, and precision mechanical parts. It is particularly suitable for applications requiring high strength, corrosion resistance, and long-term reliability under cyclic loading conditions.
ASTM / JIS / EN Standards
| Standard System | Standard / Grade | Description |
| ASTM | ASTM A564 / A564M – UNS S17700 | Wrought Precipitation-Hardening Stainless Steel Bars |
| ASTM | ASTM A693 – UNS S17700 | Precipitation-Hardening Stainless Steel Plate, Sheet and Strip |
| ASTM | ASTM A276 / A276M – UNS S17700 | Stainless Steel Bars and Shapes |
| UNS | S17700 | 17-7PH Stainless Steel Grade |
| JIS | JIS G4303 SUS631 | Stainless Steel Bars |
| EN | EN 10088-3 1.4542 (Comparable PH Family) | Precipitation Hardening Stainless Steel |
| DIN | DIN 1.4568 | X7CrNiAl17-7 Stainless Steel |
Stainless Steel Bar Execution Standards
| Item | Specification |
| Product Type | Round Bar, Square Bar, Hexagonal Bar |
| Manufacturing Process | Hot Rolled, Cold Drawn, Peeled, Ground, Polished |
| Heat Treatment | Solution Treatment + Conditioning + Aging |
| Solution Treatment | Approximately 950–970°C followed by rapid cooling |
| Conditioning Treatment | C or R Condition (Martensitic Transformation) |
| Aging Treatment | RH950, TH1050, CH900 Conditions |
| Surface Condition | Bright Surface, Ground Surface, Polished Surface |
| Dimensional Tolerance | According to ASTM A564 / ASTM A276 |
| Inspection | Chemical Analysis, Mechanical Testing, Hardness Testing, Dimensional Inspection |
| Supply Condition | Solution Treated, Cold Worked, Age Hardened |
Chemical Composition (%)
| Element | Composition Requirement |
| Carbon (C) | ≤ 0.09 |
| Silicon (Si) | ≤ 1.00 |
| Manganese (Mn) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.040 |
| Sulfur (S) | ≤ 0.040 |
| Chromium (Cr) | 16.00 – 18.00 |
| Nickel (Ni) | 6.50 – 7.75 |
| Aluminum (Al) | 0.75 – 1.50 |
| Iron (Fe) | Balance |
Mechanical Properties
Typical Aging Conditions
| Property | RH950 Condition | TH1050 Condition |
| Tensile Strength | ≥ 1240 MPa | ≥ 930 MPa |
| Yield Strength (0.2% Offset) | ≥ 1035 MPa | ≥ 725 MPa |
| Elongation | ≥ 5% | ≥ 10% |
| Hardness | Approx. 38–44 HRC | Approx. 28–35 HRC |
| Condition | Age Hardened | Age Hardened |
| Industry | Applications |
| Aerospace Industry | Aircraft structural parts, fasteners, springs |
| Spring Manufacturing | High-performance springs, clips, retaining rings |
| Precision Engineering | Diaphragms, sensors, precision components |
| Chemical Industry | Corrosion-resistant equipment components |
| Valve Industry | Valve springs, pressure control components |
| Automotive Industry | High-strength spring components |
| Mechanical Engineering | Fatigue-resistant mechanical parts |
