Special Stainless Steels
| UNS Number | UNS S17400 |
| Industry Name | 17-4PH, Type 630, 17Cr-4Ni-4Cu |
| Product Forms | Bars, Forgings, Plates,Tubes, Wires |
General Characteristics
17-4PH is martensitic precipitation hardening stainless steel. It was originally developed to combine high tensile strength and moderate corrosion resistance after simple aging heat treatment, addressing the gap between low-strength carbon steel and brittle quenched martensitic stainless for structural components.
Traditional martensitic stainless steels required complex quenching and exhibited poor toughness after hardening. It maintains mechanical properties under high static and fatigue loads at temperatures up to around 300°C, making it ideal for valve trim, pump shafts, oilfield tooling and general high-strength fasteners.
Compared to 15-5PH, 17-4PH achieves slightly higher tensile strength but contains more delta ferrite, leading to property anisotropy and lower transverse toughness. Compared to 420 stainless steel, 17-4PH provides better corrosion resistance and higher impact toughness without high quenching brittleness risk.
Chemical compositions of Alloy 17-4PH
C | Cr | Ni | Cu | Nb+Ta | Mn | Si | P | S |
≤0.07 | 15.00–17.50 | 3.00–5.00 | 3.00–5.00 | 0.15–0.45 | ≤1.00 | ≤1.00 | ≤0.040 | ≤0.030 |
Aerospace & Defence||Landing gear components|Aircraft fittings, fasteners
Power Generation||Turbine blades|Boiler hardware|Pump internals
Chemical Processing||Valves|Fittings
Marine||Propeller shafts|Pump components|Seawater service hardware
Technical Standards | Product Form |
ASTM A564 / A564M | Bar, Forging, Forged Billet, Ring, Hollow bar/Tubing |
ASTM A693 | Plate, Sheet, Strip |
AMS 5604 | Bar, Forging |
AMS 5643 | Bar, Forging, Tubing, Wire, Ring |
AMS 5622 | Wire |
EN 10088-3 | Bar, Wire |
Product form | Size range (mm) |
Forged bar | Dia.70-500 |
Rolled bar | Dia.2.0-70 |
Flat bar | T4-50*W60-300 |
Wire | Dia.0.25-18.0 |
Plate | 1-25 * ≤1200 * ≤1200 |
Seamless tube | OD 6.0-200 * 0.6-20 |
Q1: What does PH stand for in 17-4PH?
A1: PH means Precipitation Hardening. It is a martensitic precipitation hardening stainless steel. Strength is developed by aging treatment after solution annealing.
Q2: What are the common heat treatment conditions / H grades for 17-4PH?
A2: ASTM A564 defines multiple H conditions: H900, H1025, H1150, H1150M. Each aging temperature delivers different tensile strength, hardness and toughness. H900 is highest strength, lowest toughness; H1150 is lower strength with better toughness. Raw bar is normally supplied in solution treated (Condition A) for customers to machine then age harden.
Q3: Can 17-4PH raw bar be readily cold headed for fasteners?
A3: In Condition A (solution treated), it has good machinability and limited cold heading capability. Severe cold forming is not recommended. Final aging must be performed after fastener forming.
Q4: Is 17-4PH magnetic?
A4: Yes, it is magnetic, as it is martensitic stainless steel.
Q5: What is the corrosion resistance of 17-4PH?
A5: Better corrosion resistance than 410/420 martensitic stainless steel, but inferior to 316L. Suitable for fresh water, mild chemical environments; not recommended for long-term immersion in concentrated brine or strong acid.
Q6: What NDT options are available for 17-4PH bar stock?
A6: Ultrasonic testing (UT) for internal discontinuities, Magnetic Particle Inspection (MPI) for surface cracks.