17-4 PH
Also known as UNS S17400, EN 1.4542
17-4 PH is a martensitic precipitation-hardening stainless steel offering high strength with corrosion resistance similar to 304.
17-4 PH (UNS S17400) is a martensitic precipitation hardening stainless steel. Its main alloying elements are chromium (17%) and nickel (4%), with significant copper additions (typically 4%) that form highly dispersed precipitate particles on aging - the mechanism that delivers high strength.
Eight heat-treatment conditions provide a wide range of strength and toughness combinations. In Condition A (solution annealed) the grade is in its most machinable state; subsequent aging at temperatures from 482°C (H900) to 760°C (H1150D) develops the required mechanical properties. Higher aging temperatures produce lower strength but improved toughness and corrosion resistance.
Martensitic stainless steels retain their strength and toughness at temperatures up to 316°C (600°F), supporting use in oil and gas and chemical processing applications.
We stock bar in the UK and USA. Plate, tube and fittings are available on enquiry; forgings and castings to order.
- Higher strength than most other stainless steels through precipitation hardening
- Corrosion resistance comparable to Alloy 304
- Good resistance to wear
- Retains strength and toughness at temperatures up to 316°C (600°F)
- Annealed condition (Condition A) allows easy machining before final age hardening
- Eight defined conditions allow properties to be tailored precisely to the application
| Element | Min | Max |
|---|---|---|
| Iron (Fe) | Bal | |
| Chromium (Cr) | 15.00 | 17.50 |
| Nickel (Ni) | 3.00 | 5.00 |
| Copper (Cu) | 3.00 | 5.00 |
| Niobium+Tantalum (Nb+Ta) | 0.15 | 0.45 |
| Manganese (Mn) | - | 1.00 |
| Carbon (C) | - | 0.07 |
| Silicon (Si) | - | 0.01 |
| Phosphorus (P) | - | 0.04 |
| Sulphur (S) | - | 0.01 |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 55 ksi | 380 N/mm² |
| Tensile strength | 175 ksi | 1200 N/mm² |
| Elongation (5.65√S0 & 4D) | 35% | |
| Reduction of area | 55% | |
| Hardness (Brinell) | 363 max | |
| Impact strength (room temp) | 40 ft.lb | 54 J |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 170 ksi | 1170 N/mm² |
| Tensile strength (min) | 190 ksi | 1310 N/mm² |
| Elongation (5.65√S0 & 4D) | 10% | |
| Reduction of area | 40% | |
| Hardness (Brinell) | 388 min |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 155 ksi | 1070 N/mm² |
| Tensile strength (min) | 170 ksi | 1170 N/mm² |
| Elongation (5.65√S0 & 4D) | 10% | |
| Reduction of area | 44% | |
| Hardness (Brinell) | 375 min | |
| Impact strength (room temp) | 5 ft.lb | 7 J |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 145 ksi | 1000 N/mm² |
| Tensile strength (min) | 155 ksi | 1070 N/mm² |
| Elongation (5.65√S0 & 4D) | 12% | |
| Reduction of area | 45% | |
| Hardness (Brinell) | 331 min | |
| Impact strength (room temp) | 15 ft.lb | 20 J |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 125 ksi | 860 N/mm² |
| Tensile strength (min) | 145 ksi | 1000 N/mm² |
| Elongation (5.65√S0 & 4D) | 13% | |
| Reduction of area | 45% | |
| Hardness (Brinell) | 311 min | |
| Impact strength (room temp) | 20 ft.lb | 27 J |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 115 ksi | 795 N/mm² |
| Tensile strength (min) | 140 ksi | 965 N/mm² |
| Elongation (5.65√S0 & 4D) | 14% | |
| Reduction of area | 45% | |
| Hardness (Brinell) | 302 min | |
| Impact strength (room temp) | 25 ft.lb | 34 J |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 105.1 ksi | 725 N/mm² |
| Tensile strength (min) | 134.8 ksi | 930 N/mm² |
| Elongation (5.65√S0 & 4D) | 16% | |
| Reduction of area | 50% | |
| Hardness (Brinell) | 277 min | |
| Impact strength (room temp) | 30 ft.lb | 41 J |
| Property | Imperial | Metric |
|---|---|---|
| 0.2% Proof stress (min) | 105.1 ksi | 725 N/mm² |
| Tensile strength (min) | 124.7 ksi | 860 N/mm² |
| Elongation (5.65√S0 & 4D) | 16% | |
| Reduction of area | 50% | |
| Hardness (Brinell) | 255 min | |
| Impact strength (room temp) | 55 ft.lb | 75 J |
| Property | Value |
|---|---|
| Density (kg/m³) | 7750 |
| Magnetic permeability (20°C) | < 1.1 |
| Young's modulus (kN/mm²) | 200 |
| Specific electrical resistance, 20°C (µΩ.m) | 0.8 |
| Mean coefficient of thermal expansion, 0-100°C (µ/m/°C) | 10.8 |
| Specific heat, 20°C (J/kg.K) | 460 |
| Thermal conductivity, 100°C (W/m.K) | 18.4 |
| Thermal conductivity, 500°C (W/m.K) | 22.7 |
Equivalents & cross-references
Standard designations
- UNS
- S17400Unified Numbering System
- EN
- 1.4542European material number; X5CrNiCuNb16-4 X5CrNiCuNb16-4European chemical composition designation
- AISI
- 630AISI designation - confirmed in Langley datasheet
- ASTM
- A564 Type 630Hot-rolled and cold-finished bar
- ASME
- SA-564 Type 630Pressure vessel code
- AMS
- 5643Bar, wire, forgings and rings
- NACE
- MR0175 / ISO 15156-3Sour service
17-4 PH is also designated UNS S17400, EN 1.4542, EN X5CrNiCuNb16-4, AISI 630, ASTM A564 Type 630, ASME SA-564 Type 630, AMS 5643 and NACE MR0175 / ISO 15156-3.
Common questions
What is the UNS number for 17-4 PH?
17-4 PH is a high strength martensitic stainless steel covered by UNS S17400, EN 1.4542 (X5CrNiCuNb16-4), AMS5643, ASTM A564 Type 630 Condition A, AISI 630 and ASME SA-564 Type 630, and listed in NACE MR0175/ISO 15156-3 2015. Its main alloying elements are chromium (17%) and nickel (4%), with significant copper additions (typically 4%) that enable precipitation strengthening through ageing heat treatment. Langley Alloys stocks it as bar; plate, tube and fittings are available on enquiry, and forgings and castings are to order.
What is 17-4 PH used for?
17-4 PH is used for aerospace components including landing gear and turbine blades; chemical processing pump shafts and valve components; food processing mixers and agitators; oil and gas components; surgical instruments; marine propeller shafts and fasteners; and pulp and paper industry components.
How is 17-4 PH heat treated to different strengths?
17-4 PH can be supplied in the annealed Condition A, which is more readily machined and fabricated, then subjected to precipitation ageing to develop the required strength and hardness. Ageing conditions range from H900 (482°C for 1 hour), giving a 0.2% proof stress of 1170 N/mm² (170 ksi), through to H1150 and the double-aged H1150D (725 N/mm², 105 ksi). Higher ageing temperatures generally give lower strength but improved toughness and corrosion resistance.
What corrosion resistance and temperature limit does 17-4 PH offer?
17-4 PH offers corrosion resistance comparable to Alloy 304, acceptable for many corrosive environments. Its high strength and toughness are retained at temperatures up to 316°C (600°F), supporting its use in oil and gas and chemical processing industries. It also has good resistance to wear.
What is AISI 630 stainless steel?
AISI 630 is the AISI designation for 17-4 PH (UNS S17400), a precipitation-hardening martensitic stainless steel. It is also designated EN 1.4542 (X5CrNiCuNb16-4), AMS 5643, and ASTM A564 Type 630. Langley Alloys stocks this grade to these specifications.
What is EN 1.4542 stainless steel?
EN 1.4542 (X5CrNiCuNb16-4) is the European designation for UNS S17400 (17-4 PH), a precipitation-hardening martensitic stainless steel stocked by Langley Alloys to ASTM A564 Type 630, AMS 5643, and NACE MR0175/ISO 15156-3.
What is the density of 17-4 PH?
17-4 PH has a density of approximately 7.80 g/cm³ (7800 kg/m³).
Is 17-4 PH magnetic?
Yes. 17-4 PH is a martensitic precipitation-hardening stainless steel and is magnetic.
Datasheets
17-4 PH bars are supplied peeled and polished to a surface finish of 125 CLA or better; each bar is ultrasonically tested and visually inspected.
Processing capability
Cutting
Automated band sawing to 650mm (25") section. CNC sawing at all sites.
Cutting servicesMachining
Water jet cutting, turning, boring and grinding available to support your supply chain.
Machining servicesInspection & testing
Each bar ultrasonically tested and visually inspected. Additional documentation and certification available.
Inspection & testing
Tools for this grade
Pitting & crevice resistance
Pitting & Crevice Resistance
Rank alloys by PREN and get an indicative pitting temperature for a chloride service. Pick a grade and a service temperature to see whether it has margin against pitting, or compare the range in the table below. A first-pass screen for chloride and seawater service.
| Grade | UNS | PREN | Indicative CPT | Relative pitting resistance |
|---|
Indicative screen, not a certified result. PREN ranks pitting resistance; the pitting temperature here is estimated from PREN (CPT ≈ 2.5 × PREN - 50), consistent with Langley's "PREN >40, CPT exceeding 50°C" for super duplex. Real critical pitting/crevice temperature depends on test method, product form, surface finish and service chemistry. Crevice corrosion starts well below the pitting temperature - allow a margin at gaskets, deposits and flange faces. Use certified data for design.
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