17-4 PH steel (S17400): properties, composition, equivalents
17-4 PH stainless steel (UNS S17400, Type 630, EN 1.4542): 15–17.5 % Cr, 3–5 % Ni, 3–5 % Cu, Nb. Age-hardened H900 to 1170 MPa yield / 1310 MPa tensile, 40–47 HRC; H1150 for toughness. Heat-treatment conditions, properties, 1.4542/SUS630 equivalents.
What is 17-4 PH?
17-4 PH is the most-used precipitation-hardening stainless steel: a martensitic 17 % Cr / 4 % Ni matrix strengthened by copper precipitates formed during a simple single-step ageing at 480–620 °C. Because the steel is delivered soft-ish (Condition A, ≈ 35 HRC, fully machinable) and hardened afterwards at low temperature with almost no distortion (≈ 0.05 % contraction), it lets shops machine complex parts to size and then age them to 1170 MPa (170 ksi) yield and 44–47 HRC in the H900 condition — or to a tougher 725 MPa / 28 HRC at H1150. UNS S17400, AISI Type 630, EN 1.4542.
Corrosion resistance is close to 304 in most media (better than any conventional martensitic grade), which is why 17-4 is the material of pump shafts and impellers, valve stems and balls, aircraft fittings and landing-gear parts, gears, fasteners, nuclear-reactor components, oil-and-gas downhole tools and, increasingly, additively manufactured parts. The ageing temperature is chosen against the environment: H900 for maximum strength in benign service, H1025–H1150 for toughness and resistance to stress-corrosion and hydrogen embrittlement, H1150M for NACE MR0175 sour service (≤ 33 HRC).
JIS SUS630, GB 05Cr17Ni4Cu4Nb and EN 1.4542 are identical; 15-5 PH is the cleaner, ferrite-free variant preferred for transverse-loaded aerospace forgings.
17-4 PH chemical composition
| Element | Mass % | Note |
|---|---|---|
| C | ≤ 0.07 | |
| Mn | ≤ 1 | |
| P | ≤ 0.04 | |
| S | ≤ 0.03 | |
| Si | ≤ 1 | |
| Cr | 15 – 17.5 | |
| Ni | 3 – 5 | |
| Cu | 3 – 5 | |
| Nb | 0.15 – 0.45 | Nb + Ta |
ASTM A564/A564M-19 (S17400). EN 1.4542 (X5CrNiCuNb16-4): C ≤ 0.07, Cr 15–17, Ni 3–5, Cu 3–5, Nb 5×C–0.45 — identical. 15-5 PH (S15500 / 1.4545) is the remelted, ferrite-free variant with better transverse toughness.
17-4 PH mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| Condition A (solution annealed 1040 °C) — as supplied | ≈ 760 (typ.) (≈ 110.2 (typ.)) | ≈ 1030 (typ.) (≈ 149.4 (typ.)) | 10 | ≤ 363 HB / ≤ 38 HRC |
| H900 (482 °C, 1 h, air) — peak hardness | ≥ 1170 (≥ 169.7) | ≥ 1310 (≥ 190.0) | 10 | ≥ 40 HRC (388 HB); typ. 44–47 HRC |
| H925 (496 °C, 4 h) | ≥ 1070 (≥ 155.2) | ≥ 1170 (≥ 169.7) | 10 | ≥ 38 HRC (375 HB) |
| H1025 (552 °C, 4 h) | ≥ 1000 (≥ 145.0) | ≥ 1070 (≥ 155.2) | 12 | ≥ 35 HRC (331 HB) |
| H1075 (580 °C, 4 h) | ≥ 860 (≥ 124.7) | ≥ 1000 (≥ 145.0) | 13 | ≥ 32 HRC (311 HB) |
| H1100 (593 °C, 4 h) | ≥ 795 (≥ 115.3) | ≥ 965 (≥ 140.0) | 14 | ≥ 31 HRC (302 HB) |
| H1150 (621 °C, 4 h) — max toughness | ≥ 725 (≥ 105.2) | ≥ 930 (≥ 134.9) | 16 | ≥ 28 HRC (277 HB) |
| H1150M (760 °C 2 h + 621 °C 4 h) — NACE | ≥ 520 (≥ 75.4) | ≥ 795 (≥ 115.3) | 18 | ≤ 33 HRC (255–311 HB) |
| H1150D (double 621 °C) | ≥ 725 (≥ 105.2) | ≥ 860 (≥ 124.7) | 16 | ≥ 26 HRC (255 HB) |
ASTM A564 Table 4, bar ≤ 200 mm (8 in). Impact (Charpy, longitudinal, typical): H900 ≈ 20 J, H1025 ≈ 40 J, H1150 ≈ 70 J. Condition A is not a service condition — it must be aged.
Impact toughness
17-4 PH requires a minimum Charpy V-notch energy of 20 J at 20 °C (typical H900; ≈ 70 J at H1150). Toughness rises sharply with ageing temperature; H1150 and H1150M are used where impact or hydrogen-embrittlement resistance matters. Transition temperature is around −20 to 0 °C for H900.
17-4 PH equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| 1.4542 | EN (European) | Identical | X5CrNiCuNb16-4 (EN 10088-3): same analysis; delivery conditions +P800/+P930/+P960/+P1070 correspond to H1150/H1075/H1025/H900. |
| 05Cr17Ni4Cu4Nb | GB/T (China) | Identical | GB/T 20878 05Cr17Ni4Cu4Nb (formerly 0Cr17Ni4Cu4Nb). |
| SUS630 | JIS (Japan) | Identical | JIS G4303 SUS630: C ≤ 0.07, Cr 15.5–17.5, Ni 3–5, Cu 3–5, Nb 0.15–0.45. |
| 15-5 PH | AISI / SAE | Near | S15500 / 1.4545: Cr 14–15.5, Ni 3.5–5.5 — vacuum-remelted, ferrite-free, better transverse ductility and toughness; often substituted in aerospace. |
| 07Kh16N4B / 09Kh16N4B | GOST (Russia/CIS) | Near | GOST martensitic Nb-bearing 16-4 grades without copper; the closest Russian analogues, not true PH steels. |
| 13-8 Mo | AISI / SAE | Functional | S13800: higher strength and toughness, more expensive; for critical aerospace parts. |
| 410 | AISI / SAE | Functional | Conventional martensitic 12 % Cr: cheaper, lower strength (≤ 1200 MPa), poorer corrosion resistance, needs quench hardening. |
| 316 | AISI / SAE | Functional | Austenitic: similar corrosion resistance, one-quarter of the yield strength; 17-4 replaces it where strength matters. |
Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for 17-4 PH →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| Type 630 | AISI / ASTM | The numeric AISI designation for 17-4 PH. |
| 1.4542 / X5CrNiCuNb16-4 | EN 10088-3 | 1.4548 is the same steel for pressure purposes (EN 10088 older number / SEW). |
| 17-4 PH | Armco trade name (1948) | Precipitation Hardening; 15-5 PH, 13-8 Mo and Custom 450 are later relatives. |
| AMS 5643 / 5604 / 5622 | SAE Aerospace | Bar/forgings, sheet, and consumable-remelted bar. |
| CB7Cu-1 | ACI / ASTM A747 | Cast equivalent. |
Product forms and tolerance standards
Product forms: bar, wire and forgings (ASTM A564 / A705, AMS 5643), plate, sheet and strip (A693), seamless tube (A511 limited), castings CB7Cu-1 (A747), investment castings, powder-metallurgy and additive-manufactured parts.
Dimensional tolerances: bar: ASTM A484 / A564; plate/sheet: ASTM A480 / A693; aerospace: AMS 5643 (bar), AMS 5604 (sheet).
Key property values
17-4 PH yield strength by condition
H900 ≥ 1170 MPa (170 ksi); H925 ≥ 1070; H1025 ≥ 1000; H1075 ≥ 860; H1100 ≥ 795; H1150 ≥ 725 MPa (105 ksi); H1150M ≥ 520; Condition A ≈ 760 MPa typical (not for service).
17-4 PH tensile strength
H900 ≥ 1310 MPa (190 ksi); H1025 ≥ 1070; H1150 ≥ 930 MPa (135 ksi); H1150M ≥ 795 MPa.
17-4 PH hardness
Condition A ≤ 38 HRC (typ. 33–36); H900 40–47 HRC (typ. 44); H925 ≥ 38; H1025 ≥ 35; H1075 ≥ 32; H1100 ≥ 31; H1150 ≥ 28; H1150M 255–311 HB (≤ 33 HRC, NACE).
Heat treatment
Solution anneal (Condition A) 1025–1055 °C (1875–1925 °F), air or oil cool to below 32 °C to complete the martensite transformation. Age: H900 = 482 °C (900 °F) 1 h; H925 = 496 °C 4 h; H1025 = 552 °C 4 h; H1075 = 580 °C 4 h; H1100 = 593 °C 4 h; H1150 = 621 °C 4 h; H1150M = 760 °C 2 h + 621 °C 4 h; H1150D = 621 °C 4 h twice. Air cool after ageing. Dimensional change on ageing ≈ −0.04 to −0.06 % (H900) to −0.10 % (H1150).
Corrosion resistance
Comparable to 304 in most atmospheric, fresh-water, mild chemical and food environments (better than 410/420); inferior to 316 in chlorides. Stress-corrosion cracking resistance improves with ageing temperature — avoid H900/H925 in chloride or H₂S service; use ≥ H1025, or H1150M/H1150D for NACE MR0175.
Service temperature
Use up to about 315 °C (600 °F) for long-term strength (over-ageing above that); short excursions to 425 °C. Down to −40 °C for H1025 and softer; H900 is notch-sensitive below ~0 °C.
Physical properties
Density 7.8 g/cm³, E = 196 GPa (H900), expansion 10.8 × 10⁻⁶/K (0–100 °C), conductivity 18 W/m·K, resistivity 0.80 µΩ·m, ferromagnetic.
Weldability
Weldable in Condition A or over-aged (H1150) with matching ER630 / E630 filler or, for less critical joints, ER308L/ER309L. No preheat for thin sections; for > 12 mm preheat 100–150 °C. After welding, re-solution-anneal and age, or at minimum age the assembly (H900–H1150) to harden the weld and HAZ. Welding in the aged condition produces a soft HAZ and possible cracking. Resistance and laser welding are common for thin parts.
Machining, forming and heat treatment
Machine in Condition A (≈ 35 HRC; index ≈ 45 % of B1112) or, better, in H1150 (≈ 28 HRC, more uniform chips) and then re-age to the final condition; finish-machining after H900 requires carbide/CBN at 44 HRC. Threads should be rolled or cut before ageing. Cold forming is limited to gentle bends in Condition A; hot forging 1150–980 °C followed by solution treatment. Surface treatments: passivation (nitric or citric), shot peening for fatigue, PVD coatings after ageing ≤ 480 °C.
Typical applications
- Pump shafts, impellers, wear rings and valve stems, balls and seats
- Aircraft fittings, landing-gear components, actuator parts, fasteners (AMS 5643)
- Gears, shafts, couplings in food, chemical and marine equipment
- Nuclear reactor internals, control-rod components
- Oil and gas: wellhead and downhole tools, subsea parts (H1150M/H1150D per NACE)
- Firearm components, golf-club heads, surgical and dental instruments
- Additive-manufactured (L-PBF) structural parts — the standard PH stainless powder
- Paper-mill and turbine components exposed to moderate corrosion and high stress
Frequently asked questions
What does H900 or H1150 mean for 17-4 PH?
The ageing (precipitation-hardening) temperature in °F: H900 = 900 °F (482 °C) for 1 h → maximum strength, ≈ 44 HRC; H1150 = 1150 °F (621 °C) for 4 h → maximum toughness, ≈ 28–33 HRC. Intermediate conditions (H925, H1025, H1075, H1100) trade strength for toughness; H1150M and H1150D are double treatments for sour service.
Is 17-4 PH magnetic?
Yes — it is martensitic in all conditions and strongly ferromagnetic, unlike austenitic 304/316.
How does 17-4 PH compare with 316 for corrosion?
Roughly equal to 304 and below 316 in chloride environments. 17-4 is chosen when strength (3–5× the yield of 316) is needed with 'good enough' corrosion resistance; in seawater or hot chlorides use 316, duplex or over-aged 17-4 with cathodic protection.
Can 17-4 PH be machined after hardening?
Yes with carbide or CBN tooling at 40–47 HRC, but it is slow. Standard practice is to rough and semi-finish in Condition A or H1150, age, then finish-grind or lightly finish-machine; the 0.05 % shrinkage on ageing is predictable.
What is 17-4 PH equivalent to in EN and JIS?
EN 1.4542 (X5CrNiCuNb16-4) and JIS SUS630 — identical compositions. EN delivery conditions +P1070, +P960, +P930 and +P800 correspond to H900, H1025, H1075 and H1150.
What is the difference between 17-4 PH and 15-5 PH?
15-5 PH (S15500) is a vacuum-remelted, slightly lower-chromium version designed to be free of delta ferrite, giving better transverse toughness and ductility in forgings. Strength levels and heat treatments are the same; 15-5 costs more and is preferred in aerospace.
Related grades
Verified against ASTM A564/A564M-19; ASTM A564/A564M-19 Tables 1 and 4; ASTM A693/A693M (plate); AMS 5643; EN 10088-3:2014 (1.4542 comparison); NACE MR0175/ISO 15156-3 (H1150M/D limits). Last checked: September 2026.