17-7PH (UNS S17700/SUS631) Precipitation-Hardening Stainless Steel Bar Stock Technical Manual
High-Strength Corrosion-Resistant Solution for Aerospace, Medical Devices, and Beyond
- Ultra-High Strength:Tensile strength up to 1,230–1,650 MPa (after aging), hardness ≥ 38 HRC.
- Superior Corrosion Resistance:16–18% Cr content forms a passive oxide layer, resisting atmospheric/weak acid corrosion.
- Thermal Stability:Maintains performance from -196°C to 316°C with low high-temperature deformation.
- Process Advantages:Austenitic structure in solution-annealed state enables easy cold working; significant strengthening post-aging.
Chemical Composition (wt%)
Element | C | Si | Mn | P | S | Cr | Ni | Al |
Content | ≤0.09 | ≤1.0 | ≤1.0 | ≤0.04 | ≤0.03 | 16–18 | 6.5–7.75 | 0.75–1.5 |
Condition | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Hardness (HRC) |
565°C Aging | ≥1,140 | ≥960 | ≥5 | ≥36 |
510°C Aging | ≥1,230 | ≥1,030 | ≥4 | ≥38 |
1. Performance Characteristics
High Strength and Toughness: Through precipitation hardening (e.g., aging at 565°C or 510°C), tensile strength can reach 1140-1230 MPa and hardness exceeding HRC 45, while maintaining excellent toughness.
Corrosion Resistance: Containing 17% chromium and 7% nickel, it offers superior corrosion resistance to ordinary martensitic stainless steel and is suitable for environments containing chloride, but may rust with long-term exposure to marine atmospheres.
Heat Treatment Characteristics: Solution treatment (rapid cooling at 1040-1100°C) allows for easy machining, while aging significantly increases strength with minimal deformation, making it suitable for precision parts manufacturing.
Temperature Adaptability: Stable performance within the temperature range of -60°C to 350°C, but can become brittle at low temperatures (below -100°C).
2. Chemical Composition and Standards
Main Components: Chromium (17%), Nickel (7%), Aluminum (0.75%-1.5%), supplemented by carbon, manganese, silicon, and other elements.
Grade and Standard: US UNS S17700, Domestic Grade OCr17Ni7A. Production complies with ASTM A313 and other specifications.
3. Main Applications
Aerospace: Aircraft landing gear components, fasteners, and hydraulic system components subject to high stress and corrosive environments.
Chemical Equipment: Pipeline and vessel linings operating below 350°C, resistant to acid and alkaline corrosion.
Medical Devices: Surgical instruments and implant stents, requiring both biocompatibility and easy sterilization.
Elastic Components: High-precision springs and washers for automotive transmission systems and electronic equipment.
Military Equipment: Lightweight armor and missile casings requiring high strength and weather resistance.
Surface Treatment
- Mechanical Polishing:Surface roughness Ra ≤ 0.8 μm (ideal for medical devices).
- Pickling & Passivation:Treated with HNO₃ + HF solution to enhance corrosion resistance.
- Abrasive Blasting:Sa 2.5 grade for improved coating adhesion.
Why Choose Us ?
- Quality Assurance:Compliant with ASTM A693/AMS 5643, full-process spectrometric testing.
- Customization:Bar diameters Φ5–300 mm; all heat treatment types (TH/RH/CH) supported.
- Stock Availability:500+ tons ready for 72-hour express delivery.
Applications & Industries
Aerospace:
High-power density actuators.
Electronics:
Precision sensors & MEMS components.
Energy:
Magnetic coupling devices for turbines.
Frequently Asked Questions
Q1: How does 17-7PH compare to 304 stainless steel?
Strength: 17-7PH is 3–4× stronger (1950 MPa vs. 515 MPa)
Corrosion: 304 outperforms in acidic/alkaline environments
Cost: 17-7PH is more expensive due to alloy complexity
Q2: What heat treatment yields the highest hardness?
RH510 (510°C aging) achieves 40–50 HRC
Q3: Is 17-7PH weldable?
Yes, but requires post-weld heat treatment to restore properties.
Q4: What are the temperature limits?
Long-term use: ≤480°C (short-term up to 600°C).
Q5: Can it replace titanium alloys in aerospace?
For high-strength, low-weight parts, but corrosion resistance is lower.
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