17-4 PH Stainless Steel (UNS S17400)
Precipitation hardening (martensitic) · ASTM A564/A564M · Density 7.75 g/cm³
17-4 PH (UNS S17400, AISI 630) is the most widely used precipitation-hardening stainless steel. A single low-temperature ageing treatment takes it to 1310 MPa tensile strength in condition H900 — quenched-alloy-steel strength with far better corrosion resistance — while over-aged conditions such as H1150 trade strength for toughness and stress-corrosion resistance.
Chemical Composition (wt%)
| C | Mn | Si | Cr | Ni | Cu | Nb | P | S |
|---|---|---|---|---|---|---|---|---|
| ≤0.07 | ≤1.00 | ≤1.00 | 15.0–17.5 | 3.0–5.0 | 3.0–5.0 | 0.15–0.45 | ≤0.040 | ≤0.030 |
Single values are maximums unless a range is shown. Balance: Fe. Per ASTM A564/A564M.
Mechanical Properties
| Tensile strength (H900) | ≥1310 MPa (190 ksi) |
|---|---|
| Yield strength (H900) | ≥1170 MPa (170 ksi) |
| Elongation (H900) | ≥10% |
| Tensile strength (H1150) | ≥930 MPa (135 ksi) |
| Hardness (Condition A) | ≤363 HBW |
Room-temperature bar values are identified by H900 or H1150 ageing condition in the property labels; section size and the current ASTM A564/A564M requirements must be confirmed.
Physical Properties & Structure
| Density | 7.75 g/cm³ |
|---|---|
| Magnetic response | Magnetic because the matrix is martensitic after the specified heat-treatment route. |
| Microstructure | Precipitation hardening (martensitic) |
Corrosion Resistance & Limits
- Corrosion resistance can approach 304 in atmospheric and fresh-water service in suitable conditions but does not make this grade a substitute for 316 in chloride exposure.
- Ageing condition, stress, surface finish, crevices and chloride level must be reviewed together, especially for highly stressed or peak-aged components.
Fabrication & Heat Treatment
| Welding | Weld in the solution-treated condition where practical, then apply the specified post-weld solution and ageing route when joint properties require it. |
|---|---|
| Forming | Form in solution-treated condition and account for high strength, springback and dimensional change during subsequent ageing. |
| Machining | Machine in solution-treated or over-aged condition according to the dimensional and strength plan; final ageing can change size and hardness. |
| Heat treatment | Condition A solution treatment followed by the ordered H ageing condition controls the strength-toughness balance. The exact condition is a mandatory purchase-order field. |
Equivalent Grades
The closest international equivalents of 17-4 PH Stainless Steel are 1.4542 (X5CrNiCuNb16-4) in the EN system, SUS630 in the JIS system, 05Cr17Ni4Cu4Nb in the GB system.
These are common corresponding designations, not unconditional substitutes. Verify chemistry, mechanical properties, product standard, delivery condition, dimensions and project approval before changing designation.
| System | Designation |
|---|---|
| UNS | S17400 |
| EN | 1.4542 (X5CrNiCuNb16-4) |
| JIS | SUS630 |
| GB | 05Cr17Ni4Cu4Nb |
Reference Product Forms & Dimensional Ranges
Common reference product forms for 17-4 ph stainless steel: Bar, Sheet / Plate.
| Conditions | A (solution annealed); H900 / H1025 / H1150 ageing on request |
|---|---|
| Bar diameter | 6–300 mm |
| Plate thickness | 8–100 mm |
Common surface and delivery options: No.1, 2B, BA or mechanically polished finish when supported by the product route; Hot rolled, peeled, bright drawn, ground or polished bar condition according to tolerance.
These published ranges are engineering references, not a live-stock or production-capability promise. Confirm the required product form, dimensions, condition, finish and supply route in the quotation.
Typical Applications
- Pump and compressor shafts
- Valve stems and internals
- Aerospace and defense fittings
- Mold cavities and tooling
- High-strength marine hardware
Frequently Asked Questions
What do the H900 and H1150 conditions mean?
The number is the ageing temperature in degrees Fahrenheit. H900 (482 °C for 1 h) gives maximum hardness and strength; H1025 and H1150 age hotter and longer, sacrificing strength for markedly better toughness, ductility and chloride stress-corrosion resistance. Machining is usually done in condition A or H1150.
Is 17-4 PH weldable?
Yes — far better than conventional martensitic grades. Standard practice is to weld in condition A with matching filler, then solution treat and age the whole part, which restores near-full joint strength. No preheat is normally required on thin sections.
How does 17-4 PH corrosion resistance compare with 304?
In most atmospheric, fresh-water and mildly chemical environments it approaches 304, and it far exceeds hardenable grades like 410 or 440C. It is not a substitute for 316 in chloride service, and peak-aged H900 material is the most susceptible condition to stress corrosion — use H1025/H1150 where that risk exists.
17-4 PH Compared With Other Grades
Organizational author: Tsingshan (Shandong) Iron & Steel Co., Ltd..Review method, status and limitations.
Other stainless steel grades:
304304L316316L201321310S4104302205202301309S316Ti347904L409L4204394414442507303317L254 SMO440C2304
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