Product Description
17-7PH (1.4568, 631) is a premium austenitic chromium-nickel-aluminum precipitation hardening stainless steel that combines high strength, excellent fatigue resistance, and good corrosion properties with outstanding formability. With approximately 17% chromium, 7% nickel, and 1% aluminum, this versatile alloy can be easily formed in its soft austenitic condition and subsequently hardened to high strength levels through a simple, low-temperature heat treatment process that minimizes distortion.
The unique composition of 17-7PH allows for a remarkable transformation from soft, easily formable austenite to high-strength martensite through controlled heat treatment sequences. This capability provides manufacturers with significant advantages when producing complex parts that require both formability during processing and high strength in service. The material offers exceptional mechanical properties at temperatures up to 480°C (900°F), making it ideal for applications subjected to elevated temperatures.
As a precipitation hardening stainless steel, 17-7PH provides corrosion resistance comparable to Type 304 stainless steel in most environments and superior to hardenable 400 series stainless steels. This combination of excellent mechanical properties and good corrosion resistance makes 17-7PH an ideal choice for critical applications in aerospace, defense, medical, and other industries requiring high performance under demanding conditions.
FUSHUN METAL supplies 17-7PH stainless steel in various product forms and conditions to meet the diverse requirements of demanding applications. Our high-quality material provides reliable performance in critical components where the combination of formability, strength, and fatigue resistance is paramount.
Applications
17-7PH stainless steel is widely used across multiple industries due to its exceptional combination of formability, high strength, fatigue resistance, and good corrosion properties. The material is particularly valuable in applications requiring both complex forming operations and high mechanical properties in service.
Key applications for 17-7PH stainless steel include:
- Aerospace Industry: Aircraft components, fasteners, landing gear parts, bulkheads, tooling, retaining rings, and structural elements where high strength and fatigue resistance are crucial. The alloy’s ability to maintain properties at elevated temperatures makes it suitable for components operating in the 300-600°F range.
- Spring Applications: Flat springs, precision springs, retaining rings, and other spring components operating at temperatures up to 600°F (315°C). The excellent fatigue properties and high tensile strength make 17-7PH an ideal material for demanding spring applications.
- Medical Devices: Surgical instruments, biopsy needles, clips, clamps, micro springs, armor wire, cutting tools, catheters, and punch tools that require high strength, good corrosion resistance, and excellent fatigue properties. The ability to form the material in its soft condition and subsequently harden it with minimal distortion is particularly valuable for precision medical components.
- Oil and Gas Industry: Valve components, springs, fasteners, and other parts requiring both high strength and good corrosion resistance in petroleum refining equipment.
- Chemical Processing: Spring elements, fasteners, and components requiring resistance to moderately corrosive chemical environments while maintaining high strength.
- Food Processing Equipment: High-strength components that require good corrosion resistance in food handling applications.
- General Metalworking: CNC components, mould and gauge making, and general tooling applications where the combination of high strength, hardness, and good corrosion resistance is valuable.
- Musical Instruments: Hard-drawn and heat-treated 17-7PH wire is used for instrument strings due to its excellent elastic properties.
The versatility of 17-7PH stainless steel makes it an excellent choice for applications where conventional stainless steels lack sufficient strength and where the ability to form complex parts before hardening is required. Its unique combination of properties provides manufacturers with options not available with conventional hardenable or austenitic stainless steels.
Standards
17-7PH stainless steel conforms to numerous international standards and specifications, ensuring consistent quality and performance in demanding applications:
American Standards:
- UNS: S17700
- AISI/SAE: 631
- AMS 5528: Sheet, Strip and Plate
- AMS 5529: Sheet and Strip, Cold Rolled
- AMS 5568: Welded Tubing
- AMS 5644: Bars and Forgings
- AMS 5678: Wire
- AMS 5824: Welding Wire
- ASTM A313: Spring Wire
- ASTM A564/ASME SA564: Bar, Wire, and Shapes
- ASTM A579: Forgings
- ASTM A693/ASME SA693: Plate, Sheet, and Strip
- ASTM A705/ASME SA705: Forgings
- ASTM F899: Standard Specification for Wrought Stainless Steels for Surgical Instruments
European Standards:
- Material Number: 1.4568
- EN Designation: X7CrNiAl17-7
- DIN EN 10088-3: Stainless steels – Part 3: Technical delivery conditions for semi-finished products, bars, rods, wire, sections and bright products of corrosion resisting steels for general purposes
These comprehensive standards ensure that 17-7PH stainless steel from FUSHUN METAL meets the rigorous requirements for use in critical applications across various industries, particularly in aerospace, medical, and spring applications where consistent quality and performance are essential.
Material Designation and Chemical Composition
17-7PH stainless steel is known by various designations in different standards and specification systems:
| Standard System | Designation |
|---|---|
| UNS | S17700 |
| AISI/SAE | 631 |
| EN/DIN | 1.4568 |
| EN Designation | X7CrNiAl17-7 |
The chemical composition of 17-7PH stainless steel is carefully controlled to ensure optimal performance in demanding applications:
| Element | Minimum (%) | Maximum (%) |
|---|---|---|
| Carbon (C) | – | 0.09 |
| Chromium (Cr) | 16.0 | 18.0 |
| Nickel (Ni) | 6.5 | 7.8 |
| Aluminum (Al) | 0.7 | 1.5 |
| Manganese (Mn) | – | 1.0 |
| Silicon (Si) | – | 1.0 |
| Phosphorus (P) | – | 0.04 |
| Sulfur (S) | – | 0.03 |
| Iron (Fe) | Balance | – |
The carefully balanced composition of 17-7PH stainless steel, with its precise levels of chromium, nickel, and aluminum, provides the unique combination of properties that make this alloy valuable for demanding applications requiring both formability and high strength. The aluminum content is particularly crucial for the precipitation hardening response that gives the alloy its high strength after heat treatment.
Physical and Mechanical Properties
17-7PH stainless steel offers an exceptional combination of high strength, good corrosion resistance, and excellent fatigue properties. The mechanical properties can be tailored through various heat treatment conditions to meet specific application requirements.
Physical Properties
| Property | Value |
|---|---|
| Density | 7.8 g/cm³ (0.282 lb/in³) |
| Modulus of Elasticity at 20°C | 200 GPa (29 × 10⁶ psi) |
| Modulus of Rigidity | 75 GPa (11 × 10⁶ psi) |
| Electrical Resistivity at 20°C | 0.8 Ω·mm²/m (80 microhm-cm) |
| Thermal Conductivity at 20°C | 16 W/m·K (9.5 Btu·ft/hr·ft²·°F) |
| Coefficient of Thermal Expansion (20-100°C) | 15.5 × 10⁻⁶ /K (8.5 × 10⁻⁶ /°F) |
| Specific Heat Capacity at 20°C | 500 J/kg·K (0.12 Btu/lb·°F) |
| Magnetic Permeability (Annealed Condition) | 1.4-3.6 (Weakly Ferromagnetic) |
Mechanical Properties
The mechanical properties of 17-7PH stainless steel vary significantly based on the heat treatment condition. Below are typical properties for various common heat treatment conditions:
| Condition | Ultimate Tensile Strength, MPa (ksi) | 0.2% Yield Strength, MPa (ksi) | Elongation in 50mm (2″), % | Hardness |
|---|---|---|---|---|
| Annealed (Condition A) | 900-1100 (130) | 280 min (40) | 35 | B85 |
| TH1050 | 1345 (195) | 1205 (175) | 8 | C42 |
| RH950 | 1550 (225) | 1380 (200) | 7 | C47 |
| Cold Worked (Condition C) | 1620 (235) | 1517 (220) | 6 | C48 |
| CH900 | 1827 (265) | 1793 (260) | 2 | C49 |
Heat Treatment
17-7PH stainless steel achieves its high strength through specific heat treatment processes that transform the austenitic structure to martensite and then precipitate hardening phases. The standard heat treatment procedures include:
- Annealing (Condition A): Material is supplied in the annealed austenitic condition, which provides optimal formability.
- Austenite Conditioning and Transformation: To develop the high strength of the alloy from Condition A, heat treatments are performed to transform the austenite to martensite:
- TH (Transformation Hardening) Process: Heat to 760°C (1400°F), air cool, allowing martensite transformation at around room temperature, followed by precipitation hardening at the desired temperature (e.g., TH1050 uses precipitation hardening at 565°C/1050°F).
- RH (Refrigeration Hardening) Process: Heat to 955°C (1750°F), air cool, refrigerate to -73°C (-100°F) to complete the martensite transformation, then precipitation harden at 510°C (950°F) for Condition RH950.
- Cold Working and Direct Aging: When 17-7PH with an austenitic structure is substantially cold worked (Condition C), the deformation transforms the material to a martensitic structure. This cold-worked condition can be directly precipitation hardened at 482°C (900°F) to achieve Condition CH900, which provides the highest strength levels.
During heat treatment, 17-7PH alloy expands approximately 0.004 in/in from Condition A to the RH or TH Conditions. The aging treatment temperature determines the final mechanical properties, with lower aging temperatures generally producing higher strength levels.
Available Dimensions
FUSHUN METAL supplies 17-7PH stainless steel in a wide range of product forms and dimensions to meet diverse application requirements:
Plate and Sheet
| Product Form | Thickness | Width | Length |
|---|---|---|---|
| Plate | 4.0 mm – 50 mm (0.157″ – 2″) | Up to 2,000 mm (78″) | Up to 6,000 mm (236″) |
| Sheet | 0.5 mm – 4.0 mm (0.020″ – 0.157″) | Up to 1,250 mm (49″) | Up to 4,000 mm (157″) or coil form |
| Strip | 0.1 mm – 3.0 mm (0.004″ – 0.118″) | Up to 600 mm (24″) | Coil form or cut lengths |
Bar and Rod
| Product Form | Diameter/Dimension | Length |
|---|---|---|
| Round Bar | 3 mm – 200 mm (0.118″ – 8″) | Up to 6,000 mm (236″) |
| Flat Bar | Thickness: 3 mm – 50 mm (0.118″ – 2″) Width: 10 mm – 200 mm (0.394″ – 8″) |
Up to 6,000 mm (236″) |
| Wire | 0.1 mm – 12 mm (0.004″ – 0.472″) | Coil form or cut lengths |
Tube and Pipe
| Product Form | Outside Diameter | Wall Thickness | Length |
|---|---|---|---|
| Welded Tubing | 3 mm – 200 mm (0.118″ – 8″) | 0.1 mm – 5 mm (0.004″ – 0.197″) | Up to 6,000 mm (236″) |
| Miniature Tubing | 0.4 mm – 5 mm (0.016″ – 0.197″) | 0.05 mm – 0.5 mm (0.002″ – 0.020″) | Up to 6,000 mm (236″) |
Available Conditions
FUSHUN METAL provides 17-7PH stainless steel in the following conditions to meet diverse application requirements:
- Condition A: Annealed (solution treated)
- Condition C: Cold worked
- Condition CH900: Cold worked and aged at 900°F (482°C)
- Condition RH950: Refrigeration hardened and aged at 950°F (510°C)
- Condition TH1050: Transformation hardened and aged at 1050°F (565°C)
Custom dimensions, conditions, and surface finishes are available to meet your specific requirements. Material can be supplied with precision cut lengths and burr-free ends upon request.
Fabrication Information
17-7PH stainless steel can be fabricated using conventional methods, with specific considerations to ensure optimal performance of the finished components:
Forming
17-7PH stainless steel offers excellent formability in the annealed condition (Condition A):
- In comparison to other austenitic stainless steels like Type 301/1.4310, cold forming of 17-7PH is better due to its composition.
- Complex parts can be formed in the annealed condition before heat treatment to high strength levels.
- The material work hardens rapidly, so intermediate annealing may be required for deep drawing or forming intricate parts.
- The unique transformation characteristics of 17-7PH allow for forming in the soft condition followed by hardening with minimal distortion.
Welding
17-7PH can be welded using conventional inert gas methods, but with specific considerations:
- The precipitation hardening reaction in the alloy depends on the presence of aluminum, a reactive element. For this reason, inert gas methods are used to protect against the loss of aluminum during welding.
- As-welded 17-7PH will be substantially austenitic and will exhibit mechanical properties roughly equivalent to annealed (Condition A) material.
- The ductility of the weld eliminates the need for preheating and postweld annealing procedures required for conventional and age-hardenable martensitic alloys.
- To produce high-strength welds, full post-weld heat treatment (solution annealing plus austenitic conditioning, transformation, and precipitation hardening) is necessary.
- According to the Ergste® 1.4568GA datasheet, the alloy is considered not weldable due to its high aluminum content. While welding is possible with proper techniques, special care must be taken.
Machining
17-7PH stainless steel has specific machining characteristics:
- Machining in the solution annealed condition needs to be conducted with tools made of high-quality tool alloys or tungsten carbide alloys due to the tendency of the material to work harden and its relatively low thermal conductivity.
- The material work hardens rapidly during machining, requiring sharp tools and proper cutting speeds.
- Adequate cooling is essential to prevent excessive work hardening during machining operations.
Heat Treatment Considerations
- During heat treatment, 17-7PH alloy expands approximately 0.004 in/in from Condition A to the RH or TH Conditions.
- The low-temperature aging treatments allow for minimal distortion compared to conventional quench and temper hardening processes.
- For applications requiring precise dimensions, the dimensional changes during heat treatment must be considered in the design.
Corrosion Resistance and Service Limitations
17-7PH stainless steel offers good corrosion resistance properties that make it suitable for a wide range of applications, but it also has some service limitations that should be considered:
Corrosion Resistance
- The corrosion resistance of 17-7PH is comparable to that of Type 304 stainless steel in most media and is generally superior to that of the hardenable 400 series stainless steels.
- Like other stainless steels, 17-7PH in all heat-treated conditions may develop superficial rust in some environments. However, after exposure of one or two years, the amount of rust present is typically little more than that present at six months.
- The alloy provides excellent general corrosion resistance in a variety of environments, including atmospheric exposure, mild chemical environments, and many industrial applications.
Service Limitations
- Temperature Limitations: 17-7PH provides exceptional mechanical properties at temperatures up to 480°C (900°F), but prolonged exposure to temperatures above this may affect the precipitation-hardened structure and reduce mechanical properties.
- Stress Corrosion Cracking: 17-7PH may be subject to stress corrosion cracking when exposed under stress in environments containing hydrogen sulfide. For applications in these environments, careful material selection and proper heat treatment are essential.
- Magnetic Permeability: In the annealed condition, 17-7PH shows low magnetism which increases with cold forming and heat treatment. In the RH and TH conditions, the material is strongly ferromagnetic. This should be considered for applications where magnetic properties are important.
Performance Factors
- Fatigue Properties: 17-7PH offers excellent fatigue properties, which is a significant advantage in applications subjected to cyclic loading.
- Dimensional Stability: The heat treatment of 17-7PH results in minimal distortion, making it suitable for precision components.
- Cold Working Effects: Cold working will achieve higher tensile strengths as well as leaving the material slightly magnetic. The degree of cold work significantly affects the final mechanical properties, especially when combined with heat treatment.
For optimal performance in specific environments, proper material condition selection and heat treatment are essential. FUSHUN METAL’s technical team can provide guidance on the most appropriate condition and heat treatment for your specific application requirements.
Why Choose FUSHUN METAL for 17-7PH Stainless Steel
When selecting a supplier for premium 17-7PH precipitation hardening stainless steel, FUSHUN METAL stands as your preferred partner for several compelling reasons:
Superior Quality Assurance
At FUSHUN METAL, we implement rigorous quality control processes throughout our production chain. Our 17-7PH stainless steel undergoes comprehensive testing including chemical analysis, mechanical testing, microstructure examination, and corrosion testing to ensure full compliance with international standards and specifications. This meticulous attention to quality guarantees that our products consistently deliver the exceptional performance required in the most demanding applications, particularly in aerospace, spring, and medical sectors.
Metallurgical Expertise
Our team of metallurgical specialists possesses extensive experience and knowledge in the production and processing of precipitation hardening stainless steels. This expertise enables us to provide valuable technical support to help you select the optimal material condition and heat treatment for your specific application requirements. We understand the critical factors that influence the performance of 17-7PH stainless steel and can help you optimize your designs to take full advantage of its unique combination of formability and high strength.
Comprehensive Product Range
FUSHUN METAL offers one of the most extensive ranges of 17-7PH stainless steel products available, including sheet, strip, plate, bar, wire, and tubing in various conditions from annealed to fully hardened. This diverse product portfolio allows you to source all your precipitation hardening stainless steel requirements from a single, reliable supplier, streamlining your procurement process and ensuring consistency across your projects.
Custom Processing Capabilities
We understand that different applications require specific material conditions and properties. Whether you need material in the annealed condition for complex forming operations or in various hardened conditions for immediate high-strength applications, we can provide 17-7PH stainless steel that meets your exact requirements. Our capabilities include custom cutting, specialized heat treatments, precision dimensioning, and surface finishing to deliver material optimized for your specific manufacturing process.
Technical Support and Collaborative Development
Our team works closely with customers to provide technical support throughout the material selection, design, and manufacturing processes. We can assist with material specifications, heat treatment recommendations, forming guidance, and problem-solving to ensure successful implementation of 17-7PH stainless steel in your applications. This collaborative approach helps you leverage the full potential of this versatile alloy while minimizing development time and costs.
For your next project requiring the exceptional combination of formability, high strength, and excellent fatigue properties that 17-7PH stainless steel provides, we invite you to contact our technical team to discuss your specific requirements. Our experts are ready to help you select the optimal material condition and provide the premium quality products you need for reliable, long-term performance in even the most demanding applications.
