17-4PH stainless steel – UNS S17400 (ASTM A564 Type 630)
Martensitic precipitation-hardening stainless steel (Cr-Ni-Cu-Nb)
The most used PH stainless: a low-carbon martensitic matrix hardened by copper precipitation, with strengths of 930 to 1,310 MPa depending on the aging. Corrosion resistance comparable to 304 and superior to the martensitic 410/420/431.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | S17400 |
| W.Nr./EN | 1.4542 (X5CrNiCuNb16-4) |
| DIN | X5CrNiCuNb16-4 |
| JIS | SUS630 |
| Trade names | 17-4PH (AK Steel/Cleveland-Cliffs trademark), Type 630 |
| Others | 1.4548 (X5CrNiCuNb17-4-4, variant); GB 05Cr17Ni4Cu4Nb |
Standards by product form
| Form | Standard |
|---|---|
| Bar | ASTM A564 Type 630; AMS 5643; AMS 5622 (VAR) |
| Forging | ASTM A705 Type 630; AMS 5643 |
| Plate | ASTM A693 Type 630; AMS 5604 |
| Casting | ASTM A747 CB7Cu-1 |
| H2S service | NACE MR0175/ISO 15156 (H1150D, ≤ 33 HRC) |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7222.30.00 | 7222.30 | 7222.30.0024 | 7222 30 51 |
| Hot-rolled bar | 7222.11.00 | 7222.11 | 7222.11.0059 | 7222 11 11 |
| Plate (> 10 mm, width ≥ 600 mm) | 7219.21.00 | 7219.21 | 7219.21.0020 | 7219 21 10 |
| Flange and fitting | 7307.21.00 | 7307.21 | 7307.21.5000 | 7307 21 00 |
Tariff class: stainless steel (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
ASTM A564 Type 630
| Element | Range (%) |
|---|---|
| C | ≤ 0.07 |
| Mn | ≤ 1.00 |
| Si | ≤ 1.00 |
| P | ≤ 0.040 |
| S | ≤ 0.030 |
| Cr | 15.0 – 17.5 |
| Ni | 3.0 – 5.0 |
| Cu | 3.0 – 5.0 |
| Nb + Ta | 0.15 – 0.45 |
| Fe | balance |
Mechanical properties
Aged – ASTM A564 minimums (bar); see the aging table
| Property | Value |
|---|---|
| H900 – Rp0.2 / Rm | ≥ 1,170 / ≥ 1,310 MPa; A ≥ 10%; ≥ 40 HRC |
| H1025 – Rp0.2 / Rm | ≥ 1,000 / ≥ 1,070 MPa; A ≥ 12%; ≥ 35 HRC |
| H1075 – Rp0.2 / Rm | ≥ 860 / ≥ 1,000 MPa; A ≥ 13%; ≥ 32 HRC |
| H1150 – Rp0.2 / Rm | ≥ 725 / ≥ 930 MPa; A ≥ 16%; ≥ 28 HRC |
| H1150M – Rp0.2 / Rm | ≥ 515 / ≥ 795 MPa; A ≥ 18% |
| Condition A (solution annealed) | ≤ 38 HRC / 363 HB |
Typical physical properties
| Property | Value |
|---|---|
| Density | 7.78 g/cm³ (A) / 7.80 g/cm³ (H900) |
| Melting range | 1,404 – 1,440 °C |
| Modulus of elasticity | 196 GPa |
| Thermal conductivity (100 °C) | 17.9 W/m·K (H900) |
| Thermal expansion (20–100 °C) | 10.8 µm/m·K (H900) |
| Electrical resistivity | 98 µΩ·cm (A) / 77 µΩ·cm (H900) |
Aging conditions
| Condition | Aging | Min. Rp0.2 | Min. Rm | Min. A | Min. hardness |
|---|---|---|---|---|---|
| A (solution annealed) | 1,040 ± 15 °C, cool < 30 °C | – | – | – | ≤ 363 HB / 38 HRC max. |
| H900 | 482 °C / 1 h / air | 1,170 MPa | 1,310 MPa | 10% | 388 HB / 40 HRC |
| H925 | 496 °C / 4 h / air | 1,070 MPa | 1,170 MPa | 10% | 375 HB / 38 HRC |
| H1025 | 552 °C / 4 h / air | 1,000 MPa | 1,070 MPa | 12% | 331 HB / 35 HRC |
| H1075 | 579 °C / 4 h / air | 860 MPa | 1,000 MPa | 13% | 311 HB / 32 HRC |
| H1100 | 593 °C / 4 h / air | 795 MPa | 965 MPa | 14% | 302 HB / 31 HRC |
| H1150 | 621 °C / 4 h / air | 725 MPa | 930 MPa | 16% | 277 HB / 28 HRC |
| H1150M | 760 °C / 2 h / air + 621 °C / 4 h / air | 515 MPa | 795 MPa | 18% | ≈ 255 HB (typical) |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Up to ≈ 315 °C; above that, prolonged exposure embrittles (loss of toughness). Low temperatures: prefer H1100/H1150. |
| Heat treatment | Solution annealing (condition A) at 1,040 ± 15 °C, air or oil cooling to < 30 °C; machine in A and age afterwards. Aging (ASTM A564, bar minimums): H900 482 °C/1 h → Rp0.2 1,170 / Rm 1,310 MPa, 40 HRC; H925 496 °C/4 h → 1,070/1,170 MPa, 38 HRC; H1025 552 °C/4 h → 1,000/1,070 MPa, 35 HRC; H1075 579 °C/4 h → 860/1,000 MPa, 32 HRC; H1100 593 °C/4 h → 795/965 MPa, 31 HRC; H1150 621 °C/4 h → 725/930 MPa, 28 HRC; H1150M 760 °C/2 h + 621 °C/4 h → 515/795 MPa (≈ 255 HB). H1150D (621 °C/4 h twice, ≤ 33 HRC) is the condition accepted by NACE MR0175/ISO 15156 for H2S service. |
| Welding | Good by TIG, MIG, covered electrode and resistance; no preheat. Weld in condition A or H1150 and re-age (H1150 must be re-solution annealed). Consumable AWS ER630 / E630 for strength; ER308L/ER309L when the joint does not need the strength of the base metal. Oxyacetylene not recommended. |
| Machining | Good in condition A (≈ 45–50% of B1112) and better in H1150; contraction during aging of ≈ 0.05% (H900) to 0.10% (H1150). |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
Typical applications
- Pump and propeller shafts
- Valve stems and internals
- Aircraft hardware and fittings
- Studs, bolts and couplings
- Turbine blades and components
- Plastic molds and dies
- Pulp and paper and food equipment
- Subsea valves, fittings and structures
- Oil and gas drilling equipment
- Hydrojetting: high-pressure pumps and components (high strength allows thinner walls, with corrosion resistance)
- Load cells and scale cells: high-strength, corrosion-resistant spring element with low hysteresis and creep*
Alternatives: 15-5PH when transverse toughness or large sections are required; 13-8Mo for maximum toughness; 431 for lower cost at 800–950 MPa; Nitronic 50 or duplex when chlorides/SCC are present; Inconel 718, 625 or 725 for severe sour media.
17-4PH stainless steel: complete guide
What 17-4PH stainless steel is
17-4PH belongs to the family of special stainless steels, in the precipitation-hardening group. In the solution-annealed condition it is a relatively soft low-carbon martensite; aging between 480 and 620 °C precipitates finely dispersed copper and raises the strength without subsequent quenching, with minimal distortion. The name indicates the nominal composition, 17% chromium and 4% nickel, and PH stands for precipitation hardening.
Mechanical properties by condition
The condition determines everything. In H900 the minimum yield strength is 1,170 MPa and the tensile strength 1,310 MPa, with 10% elongation and 388 HBW. In H1025, the usual choice for shafts and stems, the minimums are 1,000 and 1,070 MPa with 12% and 331 HBW. In H1150 they are 725 and 930 MPa with 16% and 277 HBW; the double-aged version, H1150D, is the one required by NACE MR0175 for H2S, with hardness up to 33 HRC.
Heat treatment
Solution annealing at 1,040 °C, with cooling to below 30 °C, gives condition A. Aging ranges from 482 °C (H900) to 621 °C (H1150), for 1 to 4 hours, and H1150M adds a step at 760 °C. A part in H1075 can be re-aged at a higher temperature; to return to a harder condition it must be solution annealed again. Dustre performs these cycles in its own furnaces as part of its heat treatment service.
Corrosion and limits of use
In atmosphere, fresh water, mild marine environments and many chemical media the resistance is similar to 304 and superior to all conventional martensitic grades; the PREN is 15 to 17, so concentrated chlorides and stagnant seawater cause pitting. In the harder conditions there is a risk of stress corrosion cracking and hydrogen embrittlement, which leads to preferring H1025 or above and, in H2S, H1150D. Under load, use goes up to about 315 °C.
15-5PH or 17-4PH
The ASTM standards give the two alloys the same mechanical requirements.
Applications
Pump and propeller shafts, valve stems and seats, aircraft fittings and fasteners, hydraulic fittings, bolts, bushings and wear rings, oil and gas components, paper, pulp and food equipment, and marine parts. For bar in commercial sizes, see the 17-4PH round bar.
Supply forms and Dustre services
Round bars and blocks forged in open die, cut to size on a band saw, with rough or finish machining, heat treatment (quenching and tempering, annealing, solution annealing and aging) in our own furnaces and hardness, tensile and impact testing. All material is supplied with a 3.1 inspection certificate and heat traceability.
Frequently asked questions
What is the chemical composition of 17-4PH stainless steel?
Per ASTM A564 Type 630: C ≤ 0.07; Mn ≤ 1.00; Si ≤ 1.00; P ≤ 0.040; S ≤ 0.030; Cr 15.0 – 17.5.
Which standards cover 17-4PH stainless steel?
Bar: ASTM A564 Type 630; AMS 5643; AMS 5622 (VAR). Forging: ASTM A705 Type 630; AMS 5643. Plate: ASTM A693 Type 630; AMS 5604. Casting: ASTM A747 CB7Cu-1. H2S service: NACE MR0175/ISO 15156 (H1150D, ≤ 33 HRC).
Up to what temperature can 17-4PH stainless steel be used?
Up to ≈ 315 °C; above that, prolonged exposure embrittles (loss of toughness). Low temperatures: prefer H1100/H1150.
Which materials can replace 17-4PH stainless steel?
15-5PH when transverse toughness or large sections are required; 13-8Mo for maximum toughness; 431 for lower cost at 800–950 MPa; Nitronic 50 or duplex when chlorides/SCC are present; Inconel 718, 625 or 725 for severe sour media.
What is 17-4PH steel?
It is a martensitic precipitation-hardening stainless steel, with about 17% chromium, 4% nickel and 3 to 5% copper. After solution annealing, it is aged at a temperature between H900 and H1150 to reach the desired strength, with little distortion.
Is 17-4PH magnetic?
Yes. The matrix is martensitic, so 17-4PH is magnetic in all conditions, unlike 304 and 316.
Does 17-4PH rust?
It resists corrosion much like 304 in atmosphere and fresh water, but may suffer pitting in stagnant seawater and stress corrosion cracking in the harder conditions (H900). For chlorides and H₂S, use H1150 or H1150D, or a duplex.
What is the difference between H900 and H1150?
It is the aging temperature in °F. H900 gives the highest strength and the lowest toughness; H1150 trades strength for toughness and for stress corrosion resistance.
Is 17-4PH suitable for high pressure?
Yes. Aged, it has a minimum yield strength of 725 MPa (H1150) to 1,170 MPa (H900), which allows thinner walls in waterjet pumps, valves and subsea fittings. In seawater and H₂S, prefer H1150 or H1150D and consider the risk of pitting in stagnant water.
Is 17-4PH used for load cells?
Yes. Aged 17-4PH is used for the spring element of load cells and scale cells: its high strength lets it work in the elastic range with enough strain for the strain gauges, it resists corrosion without coating and it has low hysteresis and creep*. Load cell makers list 17-4PH and 15-5PH as element materials.
