PH stainless steel 630丨17-4PH
PH stainless steel 17-4PH, also known as UNS S17400, AISI Type 630, or EN 1.4542, is a martensitic precipitation-hardening stainless steel combining high strength, high hardness, good toughness, and good corrosion resistance. J&A Alloy supplies 17-4PH stainless steel in bar, plate, sheet, forgings, wire, rings, billets, and custom machined components for aerospace, valves, pump shafts, fasteners, oil and gas equipment, chemical processing, and precision engineering applications.
PH stainless steel 17-4PH丨UNS S17400丨 AISI 630丨EN 1.4542
PH stainless steel 17-4PH is one of the most widely used precipitation-hardening stainless steels. It is a chromium-nickel-copper martensitic stainless steel strengthened by precipitation hardening. The alloy is commonly identified as 17-4PH, 17-4 PH, AISI Type 630, UNS S17400, EN1.4542, and X5CrNiCuNb16-4.
The name 17-4PH refers to the alloy’s approximate composition of 17% chromium and 4% nickel, with copper and niobium additions that enable hardening by a simple aging heat treatment. After solution treatment and aging, 17-4PH develops high tensile strength, high yield strength, good hardness, and useful toughness.
Compared with standard austenitic stainless steels such as 304 and 316L, 17-4PH provides much higher strength and hardness. Compared with semi-austenitic PH grades such as 17-7PH and 15-7Mo, 17-4PH is more commonly used for bars, forgings, shafts, valve components, pump parts, and machined engineering components. It is widely selected when engineers need a balance of strength, corrosion resistance, machinability, and dimensional stability.
17-4PH At a Glance
| Key Attribute | Value |
|---|---|
| Material | PH Stainless Steel 17-4PH |
| UNS Number | S17400 |
| AISI Type | Type 630 |
| EN / W.Nr. | 1.4542 / X5CrNiCuNb16-4 |
| Material Type | Martensitic Precipitation-Hardening Stainless Steel |
| Density | Approx. 7.75 g/cm³ |
| PREN | Approx. 16–17 |
| Main Advantage | High Strength, High Hardness, Good Corrosion Resistance and Good Machinability |
| Typical Service Temperature | Up to approx. 315°C / 600°F for many applications; selected conditions may be used up to approx. 427°C / 800°F with engineering evaluation |
| Main Industries | Aerospace, Valves, Oil & Gas, Chemical Processing, Marine Equipment, Power Generation, General Engineering |
| Comparable Grades | 15-5PH, 17-7PH, 13-8Mo, 304, 316L, 410 |
Features of 17-4PH
- High tensile strength and yield strength after precipitation hardening.
- Good corrosion resistance in atmospheric, fresh water, and mild chemical environments.
- Excellent combination of strength, hardness, and toughness for engineering components.
- Single-step low-temperature aging treatment helps reduce scaling and distortion.
- Good machinability in both solution-treated and aged conditions.
- Suitable for bars, forgings, shafts, valve parts, pump parts, and precision machined components.
- Available in multiple heat-treated conditions such as H900, H1025, H1075, H1100 and H1150.
- Better strength than 304 and 316L stainless steels where high-load performance is required.
- Useful mechanical performance at moderately elevated temperatures.
- Widely used in aerospace, oil and gas, chemical processing, marine equipment, and power generation.
Chemical Composition of 17-4PH
| Element | Content (%) |
|---|---|
| Carbon (C) | ≤ 0.07 |
| Manganese (Mn) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.040 |
| Sulfur (S) | ≤ 0.030 |
| Silicon (Si) | ≤ 1.00 |
| Chromium (Cr) | 15.00–17.50 |
| Nickel (Ni) | 3.00–5.00 |
| Copper (Cu) | 3.00–5.00 |
| Niobium / Columbium + Tantalum | 0.15–0.45 |
| Iron (Fe) | Balance |
Physical Properties of 17-4PH
| Property | Typical Value |
|---|---|
| Density | Approx. 7.75 g/cm³ / 0.280 lb/in³ |
| Melting Range | Approx. 1404–1440°C / 2560–2625°F |
| Electrical Resistivity | Approx. 0.80 μΩ·m / 80 μΩ·cm |
| Thermal Conductivity | Approx. 17.9–18.4 W/m·K at room to moderate temperature |
| Specific Heat Capacity | Approx. 460 J/kg·K / 0.11 BTU/lb·°F |
| Modulus of Elasticity | Approx. 196–200 GPa / 28.5–29.0 × 10⁶ psi |
Mechanical Properties of 17-4PH
The mechanical properties of PH stainless steel 17-4PH depend on heat treatment condition, product form, section size and specification. H900 provides the highest strength and hardness, while H1025, H1075, H1100 and H1150 provide progressively improved toughness and ductility with lower strength.
| Condition | Tensile Strength | Yield Strength | Elongation | Hardness |
|---|---|---|---|---|
| Condition A / Solution Annealed | Approx. 1100 MPa / 160 ksi | Approx. 1000 MPa / 145 ksi | Approx. 5–10% | Approx. HRC 32–36 |
| H900 Condition | Approx. 1310 MPa / 190 ksi | Approx. 1170 MPa / 170 ksi | Approx. 8–10% | Approx. HRC 40–44 |
| H1025 Condition | Approx. 1070 MPa / 155 ksi | Approx. 1000 MPa / 145 ksi | Approx. 8–12% | Approx. HRC 35–38 |
| H1075 Condition | Approx. 1000 MPa / 145 ksi | Approx. 862 MPa / 125 ksi | Approx. 9–13% | Approx. HRC 31–36 |
| H1100 Condition | Approx. 965 MPa / 140 ksi | Approx. 793 MPa / 115 ksi | Approx. 10–14% | Approx. HRC 28–34 |
| H1150 Condition | Approx. 930 MPa / 135 ksi | Approx. 724 MPa / 105 ksi | Approx. 12–16% | Approx. HRC 26–32 |
Corrosion Resistance
PH stainless steel 17-4PH provides good general corrosion resistance in many atmospheric, fresh water, food processing, chemical processing, and mildly corrosive industrial environments. Its corrosion resistance is generally superior to hardenable chromium stainless steels such as 410 and 420, and it is often considered comparable to 304 stainless steel in many mild environments when properly heat treated and passivated.
For pitting and crevice corrosion, 17-4PH performs adequately in clean, mildly corrosive environments, but it should not be treated as a high-molybdenum stainless steel. Because it does not contain molybdenum, it has limited resistance to severe chloride attack compared with 316L, 904L, 254SMO, duplex stainless steels, and nickel alloys. Stagnant chloride solutions, salt deposits, tight crevices, and marine immersion conditions can increase the risk of localized corrosion.
Stress corrosion cracking resistance depends on heat treatment condition, stress level, temperature, and environment. Higher aging temperatures such as H1025, H1075, H1100, and H1150 are often preferred when toughness and stress corrosion cracking resistance are more important than maximum strength. H900 provides the highest strength but may be less suitable for highly stressed chloride environments without engineering evaluation.
In acid environments, 17-4PH is suitable only for selected mild chemical media. It is not recommended for hydrochloric acid, hot reducing acids, severe sulfuric acid service or aggressive chloride-acid combinations. For strong acid or severe chemical environments, J&A Alloy can help evaluate alternatives such as 904L, Alloy 20, 254SMO, duplex stainless steel, Hastelloy C-276 or Hastelloy C-22.
High Temperature Performance
PH stainless steel 17-4PH retains useful strength at moderately elevated temperatures and is commonly used in aerospace, valves, pumps, mechanical components, and process equipment where high strength and dimensional stability are required. Many applications use 17-4PH up to approximately 315°C / 600°F, while selected service conditions may allow use up to about 427°C / 800°F depending on aging condition, load, and exposure time.
At elevated temperatures, long-term exposure may cause over-aging, toughness reduction, or changes in mechanical properties. Components that operate near the aging temperature range should be reviewed carefully to ensure that strength, hardness, and dimensional stability remain acceptable during service.
17-4PH is not a dedicated high-temperature alloy. It should not be used as a substitute for nickel alloys where long-term creep strength, oxidation resistance or thermal fatigue resistance is critical. For continuous high-temperature service above its practical range, materials such as Inconel 625, Inconel 718, Inconel X-750, A-286 or high-temperature nickel alloys may be more suitable.
Available Forms
- Round bar
- Flat bar
- Square bar
- Hex bar
- Plate
- Sheet
- Strip
- Rod
- Wire
- Forgings
- Forged rings
- Billets
- Blocks
- Discs
- Shaft blanks
- Flanges
- Machined parts
- Custom heat-treated components
Applications of 17-4PH
Aerospace
- Aircraft structural fittings
- Actuator components
- Fasteners and pins
- Landing gear-related components
- High-strength machined parts
Valve & Fluid Control
- Valve stems
- Valve bodies
- Valve seats
- High-strength fittings
- Control valve components
Oil & Gas
- Pump shafts
- Couplings
- Mechanical seals
- Pressure components
- Downhole and surface equipment parts
Chemical Processing
- Pump components
- Process equipment parts
- Fasteners
- High-strength connectors
- Corrosion-resistant mechanical assemblies
Marine Engineering
- Marine hardware in mild environments
- Shafts and couplings
- Fastening systems
- Deck equipment components
- Pump and valve parts
Power Generation
- Turbine auxiliary components
- High-strength fasteners
- Shafts and couplings
- Precision mechanical parts
- Heat-treated equipment components
Food & General Industrial Equipment
- Food processing machinery parts
- Paper mill equipment
- Wear-resistant components
- Machine tool parts
- High-strength industrial fasteners
17-4PH vs 15-5PH vs 17-7PH vs 316L
| Grade | Main Advantage | Strength | Corrosion Resistance | Typical Application |
|---|---|---|---|---|
| 17-4PH / UNS S17400 | High strength, good hardness, good corrosion resistance and wide availability | High | Good in mild environments | Shafts, valves, pump parts, aerospace fittings, fasteners and machined components |
| 15-5PH / UNS S15500 | Improved transverse toughness and ductility compared with 17-4PH | High | Good | Aerospace parts, shafts, gears, valve parts and precision forgings |
| 17-7PH / UNS S17700 | Excellent fatigue resistance and formability for thin sheet and strip | Very High in spring conditions | Good in mild environments | Springs, washers, diaphragms, bellows, clips and aerospace strip parts |
| 316L Stainless Steel | Better chloride corrosion resistance and excellent weldability | Moderate | Better than 17-4PH in many chloride environments | Marine equipment, chemical piping, tanks, sanitary equipment and welded fabrication |
17-4PH vs 410 Stainless Steel
| Item | 17-4PH Stainless Steel | 410 Stainless Steel |
|---|---|---|
| Material Type | Martensitic precipitation-hardening stainless steel | Martensitic stainless steel |
| Strengthening Method | Solution treatment plus precipitation aging | Quenching and tempering |
| Strength | High | Medium to high |
| Corrosion Resistance | Generally better | Moderate |
| Dimensional Stability | Good during low-temperature aging | More dependent on quenching and tempering process |
| Typical Use | High-strength shafts, valves, pump parts and aerospace components | General hardenable stainless parts, blades, fasteners and wear components |
Welding & Fabrication
PH stainless steel 17-4PH can be welded using common welding processes such as GTAW, GMAW and SMAW. GTAW is often selected for precision welds and controlled heat input. GMAW may be used for production welding when shielding gas, filler material and heat input are properly controlled. SMAW can be used for selected repair, structural and thicker-section applications.
For best results, 17-4PH is commonly welded in the solution-treated condition, followed by the appropriate aging treatment to achieve final mechanical properties. Welding after final aging may soften the heat-affected zone or produce non-uniform hardness and strength. For critical parts, welding procedure qualification and post-weld mechanical testing may be required.
Post-weld heat treatment is generally recommended when the welded component must meet specified strength, hardness, toughness or corrosion-resistance requirements. The selected condition, such as H900, H1025, H1075 or H1150, should match the engineering requirement for strength and toughness.
17-4PH has good machinability compared with many high-strength stainless steels. It can be machined in Condition A or aged conditions, but cutting parameters should be adjusted according to hardness. Sharp tools, rigid setups, adequate coolant and controlled feeds are recommended. For corrosion-sensitive parts, pickling, cleaning and passivation after machining or welding are recommended.
Standards & Equivalent Grades
| Category | Designation / Standard |
|---|---|
| UNS | S17400 |
| AISI | Type 630 |
| Common Names | 17-4PH, 17-4 PH, Alloy 630, Type 630 |
| EN / W.Nr. | 1.4542 / X5CrNiCuNb16-4 |
| ASTM | ASTM A564 Grade 630, ASTM A693 Grade 630, ASTM A705 Grade 630, ASTM A484 |
| AMS | AMS 5604, AMS 5622, AMS 5643, AMS 5825 |
| ASME | ASME SA564, ASME SA693, project-specific ASME requirements may apply |
| ISO | Equivalent ISO references may apply depending on product form and customer specification |
| JIS | SUS630 |
| NACE | May require project-specific review for sour or chloride service; not automatically suitable for all NACE applications |
| Material Family | Martensitic Precipitation-Hardening Stainless Steel |
Frequently Asked Questions
What is PH stainless steel 17-4PH?
PH stainless steel 17-4PH is a martensitic precipitation-hardening stainless steel that provides high strength, high hardness, good toughness and good corrosion resistance after solution treatment and aging.
What is the UNS designation for 17-4PH stainless steel?
The UNS designation for 17-4PH stainless steel is UNS S17400.
Is 17-4PH the same as AISI Type 630?
Yes. 17-4PH stainless steel is commonly designated as AISI Type 630. It is also known as UNS S17400, EN 1.4542 and X5CrNiCuNb16-4.
What is 17-4PH stainless steel used for?
17-4PH stainless steel is used for aerospace components, valve parts, pump shafts, mechanical seals, fasteners, gears, couplings, oil and gas components, chemical processing equipment and precision machined parts.
What is the main advantage of 17-4PH stainless steel?
The main advantage of 17-4PH stainless steel is its combination of high strength, good corrosion resistance, useful toughness and relatively simple low-temperature aging heat treatment.
Can 17-4PH stainless steel be welded?
Yes. 17-4PH stainless steel can be welded using GTAW, GMAW and SMAW processes. For critical components, post-weld heat treatment is recommended to achieve the required strength and hardness.
Does 17-4PH need post-weld heat treatment?
Post-weld heat treatment is recommended when the welded part must meet specified mechanical properties, corrosion resistance or hardness requirements. The exact aging condition should match the application.
Is 17-4PH stainless steel magnetic?
Yes. 17-4PH stainless steel is magnetic because it has a martensitic microstructure after heat treatment.
What temperature can 17-4PH stainless steel withstand?
17-4PH is commonly used up to approximately 315°C / 600°F in many applications. Selected heat-treated conditions may be used up to about 427°C / 800°F with engineering evaluation.
Is 17-4PH stainless steel corrosion resistant?
17-4PH provides good corrosion resistance in atmospheric, fresh water and mild chemical environments. It is not recommended for severe chloride, seawater immersion or strong acid service without engineering review.
What is the difference between 17-4PH and 15-5PH?
17-4PH and 15-5PH are both martensitic precipitation-hardening stainless steels. 15-5PH generally offers better transverse toughness and ductility, while 17-4PH is more widely available and commonly used for general high-strength machined components.
What is the difference between 17-4PH and 316L?
17-4PH offers much higher strength and hardness after aging, while 316L provides better weldability and better corrosion resistance in many chloride-containing environments. 17-4PH is selected for strength, while 316L is selected for corrosion-resistant fabrication.
What heat treatment conditions are available for 17-4PH?
Common heat treatment conditions include Condition A, H900, H925, H1025, H1075, H1100 and H1150. H900 provides the highest strength, while H1150 provides better ductility and toughness.
What forms of 17-4PH stainless steel are available?
17-4PH stainless steel is available in round bar, flat bar, square bar, hex bar, plate, sheet, strip, wire, forgings, rings, billets, blocks, discs and custom machined parts.
Why Choose J&A Alloy
Global Material Solutions
J&A Alloy supplies stainless steels, precipitation-hardening stainless steels, duplex stainless steels, super austenitic stainless steels, nickel alloys, titanium alloys and high-performance corrosion-resistant alloys for demanding industrial applications. For PH stainless steel 17-4PH, we support bar, plate, sheet, forgings, wire, rings, billets and custom processed components according to project requirements.
Strict Quality Assurance
J&A Alloy provides strict quality control for chemical composition, mechanical properties, dimensional tolerance and surface condition. Available inspection and documentation services include PMI, chemical analysis, mechanical testing, hardness testing, ultrasonic testing, dimensional inspection and EN 10204 3.1 / 3.2 certification when required.
International Standards
Materials can be supplied according to ASTM, ASME, EN, ISO, AMS and customer-specific specifications. For PH stainless steel 17-4PH, we support common standards such as ASTM A564 Grade 630, ASTM A693 Grade 630, ASTM A705 Grade 630, AMS 5604, AMS 5622 and AMS 5643 depending on product form and technical requirements.
Value-added Services
J&A Alloy offers cutting, CNC machining, heat treatment coordination, grinding, polishing, custom fabrication and export packaging. We help customers reduce processing time, control material waste and receive ready-to-use or semi-finished materials for manufacturing.
Worldwide Supply
J&A Alloy serves customers in aerospace, chemical processing, oil and gas, marine engineering, power generation, precision manufacturing and industrial equipment markets. With experience in international logistics and export documentation, we support global buyers with reliable material supply and responsive technical communication.
