Precipitation-Hardening Martensitic Stainless with Tunable High Strength
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UNS NUMBER
S17400
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ALLOY FAMILY
Martensitic (PH)
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STRUCTURE
Martensitic (Precipitation-Hardened)
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UTS (MIN)
≥1310 MPa
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MAX TEMP
~300°C
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DENSITY
7.80 g/cm³
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Stainless Steel 17-4PH (UNS S17400) is a precipitation-hardening martensitic stainless that reaches yield strengths near 1170 MPa through a simple low-temperature copper aging step. It combines roughly 304-level corrosion resistance with the strength of a much more expensive alloy, making it the workhorse for pump shafts, valve stems, and aerospace hardware. ASTM designation is Type 630; EN 1.4542.
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Cr
15–17.5%
Passive film; corrosion base
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Ni
3–5%
Martensite + toughness
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Cu
3–5%
Precipitation hardening
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Nb
0.15–0.45%
Refines grains; stabilizes
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UTS
≥1310 MPa
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YS 0.2%
≥1170 MPa
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Elong.
≥10% (H900)
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Service
up to ~300°C
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What is Stainless Steel 17-4PH?
17-4PH (also called Alloy 630) gets its name from its 17% chromium and 4% nickel, plus roughly 4% copper that drives precipitation hardening. After a solution anneal (Condition A), a single low-temperature aging treatment (e.g. H900 at 482°C) precipitates copper-rich phases in the martensitic matrix, pushing yield strength to about 1170 MPa — far above any austenitic grade.
The defining point is that the heat-treatment condition is part of the specification: you must state H900, H1025, H1150, etc. Higher aging temperature trades strength for toughness and stress-corrosion resistance. 17-4PH is magnetic in all conditions and not meant for high-temperature service (its useful range ends around 300°C). For chloride service, age at H1025 or above for best SCC resistance.
Chemical Composition (Weight %)
| Element |
Min (%) |
Max (%) |
Role in Alloy |
| Chromium (Cr) |
15.0 |
17.5 |
Passive film; corrosion base |
| Nickel (Ni) |
3.0 |
5.0 |
Martensite formation; toughness |
| Copper (Cu) |
3.0 |
5.0 |
Precipitation-hardening element |
| Niobium + Tantalum (Nb+Ta) |
0.15 |
0.45 |
Grain refinement; stabilization |
| Carbon (C) |
— |
0.07 |
Kept low for weldability |
| Manganese (Mn) |
— |
1.00 |
Deoxidizer |
| Silicon (Si) |
— |
1.00 |
Deoxidizer |
| Phosphorus (P) |
— |
0.040 |
Impurity |
| Sulfur (S) |
— |
0.030 |
Impurity |
| Iron (Fe) |
Balance |
— |
Matrix former |
★ Copper 3–5% is the precipitation-hardening driver; niobium refines the structure. EN 1.4542 / GB 05Cr17Ni4Cu4Nb are the common equivalents. Always specify the aging condition.
Mechanical Properties
17-4PH properties are set by the aging condition. Values below are per ASTM A564 / AMS 5643.
| Condition / Form |
UTS (MPa) |
YS 0.2% (MPa) |
Elong. % (min) |
Hardness (max) |
| Condition A (solution annealed) |
~1000 |
~800 |
~10 |
≤38 HRC |
| H900 (peak aged) |
≥1310 |
≥1170 |
≥10 |
40–48 HRC |
| H1025 (balanced) |
≥1070 |
≥1000 |
≥12 |
35–40 HRC |
| H1150 (max toughness) |
≥930 |
≥795 |
≥16 |
30–35 HRC |
Elastic Modulus ~197 GPa. Aging above H900 lowers strength but raises toughness and chloride SCC resistance. H1150 is common for marine/subsea hardware.
Physical Properties
| Property |
Value |
Note |
| Density |
7.80 g/cm³ |
Lower than austenitics |
| Melting Range |
1404–1440°C |
Solidus ~1404°C |
| Thermal Conductivity (149°C) |
17.9 W/m·K |
At aging temp |
| Thermal Expansion (21–100°C) |
10.8 ×10⁻⁶ /K |
Lower than austenitic |
| Specific Heat |
460 J/kg·K |
At 21°C |
| Electrical Resistivity |
0.80 µΩ·m |
At 21°C |
| Magnetic Property |
Magnetic |
In all conditions |
| PREN (Pitting Resistance) |
~17 |
No Mo; modest |
Corrosion Resistance
General Corrosion
Corrosion resistance is comparable to 304 in oxidizing atmospheres, fresh water, and dilute acids. It is better than traditional martensitic grades (e.g. 410, 431) but below 316.
Pitting & Stress Corrosion
PREN ~17 (no molybdenum) means limited pitting resistance in chlorides. For chloride service, age at H1025 or higher; H1150 gives the best SCC resistance for marine and subsea use.
Strength vs Corrosion Trade-off
Peak strength (H900) maximizes hardness but reduces toughness and SCC resistance. Specify the condition to match the service: H900 for strength, H1150 for toughness/marine.
Not a High-Temperature Grade
Useful temperature range ends around 300°C. Prolonged high-temperature exposure overages the material and reduces properties. It is a strength grade, not a heat-resistant grade.
Stainless Steel 17-4PH vs Similar Grades — Selection Guide
| If you need... |
Choose... |
Why |
| High-strength shaft / fastener |
17-4PH H900 |
Yield ~1170 MPa |
| Marine / subsea, chloride SCC |
17-4PH H1150 |
Best SCC resistance |
| Pump shaft, balanced |
17-4PH H1025 |
Strength + toughness |
| Need corrosion > strength |
316 / 904L |
Higher PREN |
| Aerospace actuator |
17-4PH (AMS 5643) |
Spec-controlled |
Applicable Standards
| Standard |
Product Form |
| ASTM A564 (Type 630) |
Bar, rod, shapes |
| ASTM A693 |
Plate, sheet, strip |
| ASTM A705 |
Forgings (flanges) |
| AMS 5643 |
Aerospace bar/wire |
| ASTM A276 / A479 |
Bar, rod |
| EN 1.4542 / GB 05Cr17Ni4Cu4Nb |
European / Chinese equiv. |
HT PIPE Supply — Stainless Steel 17-4PH Product Forms
| Product Form |
Specifications |
HT PIPE Supply |
| Bar / Rod |
ASTM A564 Type 630 |
✅ Available |
| Plate / Sheet |
ASTM A693 |
✅ Available |
| Forged Flanges |
ASTM A705, ASME B16.5 |
✅ In stock |
| Forgings / Custom |
ASTM A705 |
✅ Available |
| Aging (H900–H1150) |
Heat-treat service |
✅ On request |
| Fasteners / Custom |
Made to drawing |
✅ On request |
HT PIPE supplies 17-4PH in Condition A ready for your aging, and offers heat-treatment to H900–H1150 with full MTRs and EN 10204 certification.
Project Experience — Stainless Steel 17-4PH
HT PIPE supplies 17-4PH for high-strength pump shafts, valve stems, fasteners, and aerospace hardware.
| Project |
Product |
Specification |
| Subsea Valve Stems (Offshore) |
17-4PH H1150 Bar |
A564, aged |
| Centrifugal Pump Shafts (Asia) |
17-4PH H1025 Forgings |
A705, aged |
| Aerospace Actuator Parts (Europe) |
17-4PH H900 Bar |
AMS 5643 |
We provide condition-specific heat treatment and PMI; always state the required aging condition when ordering.
| FREQUENTLY ASKED QUESTIONS |
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FAQ — Stainless Steel 17-4PH
| What is the most important thing when ordering 17-4PH? |
| Specify the heat-treatment condition (H900, H1025, H1150, etc.). The properties are entirely set by aging; ordering just "17-4PH" is incomplete and may yield the wrong strength. |
| What is the difference between H900 and H1150? |
| H900 (482°C) gives peak strength (~1170 MPa yield, 40–48 HRC) with lower toughness. H1150 (621°C) gives the best toughness and chloride SCC resistance (~795 MPa yield) for marine/subsea use. |
| Is 17-4PH corrosion resistant? |
| Comparable to 304 in oxidizing environments and far better than 410/431 martensitics, but PREN ~17 means limited pitting resistance in chlorides. Age at H1025+ for best chloride service. |
| Is 17-4PH magnetic? |
| Yes, in all conditions. After aging it becomes strongly magnetic, unlike the austenitic grades. |
| Can 17-4PH be used at high temperature? |
| No. Its useful range ends around 300°C; prolonged high-temperature exposure overages the material. It is a high-strength grade, not a heat-resistant grade. |
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Need Stainless Steel 17-4PH for High-Strength Parts?
HT PIPE supplies 17-4PH (UNS S17400 / Type 630) in Condition A with heat-treatment to H900–H1150, plus flanges, forgings, and bar with full MTRs. Contact our technical team — and specify your aging condition.
Request a Quote |
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