Special Stainless Steels
| UNS Number | UNS S15500 |
| Industry Name | 15-5PH |
| Product Forms | Bars, Forgings, Plates,Tubes, Wires |
General Characteristics
15-5PH is improved martensitic precipitation hardening stainless steel. It was originally developed to eliminate residual delta ferrite found in 17-4PH, removing mechanical property anisotropy for critical loaded components where transverse toughness is essential.
17-4PH often suffered inconsistent ductility through thickness for high-reliability service. 15-5PH delivers uniform high strength and excellent transverse fracture toughness under heavy impact and cyclic fatigue loads, making it ideal for high-pressure valve internals, aerospace fittings, pump shafts and downhole oilfield components.
Compared to 17-4PH, 15-5PH trades minor tensile strength for greatly improved homogeneity and transverse toughness. Compared to 13-8PH, 15-5PH is more economical and easier to produce, while 13-8PH provides ultra-high toughness for top-level aerospace critical parts.
Chemical compositions of Alloy 15-5PH
C | Cr | Ni | Cu | Nb+Ta | Mn | Si | P | S |
≤0.07 | 14.00–15.50 | 3.50–5.50 | 2.50–4.50 | 0.15–0.45 | ≤1.00 | ≤1.00 | ≤0.040 | ≤0.030 |
Aerospace||Structural fittings|Actuator parts|Landing gear components
Power Generation||Steam turbine blades|Pump and valve internals
Petrochemical||Pressure boundary fasteners|Compressor components
Marine||High strength pump and valve parts
Technical Standards | Product Form |
ASTM A564 / A564M | Bar, Forging, Forged Billet, Ring, Hollow bar/Tubing |
ASTM A693 | Plate, Sheet, Strip |
AMS 5862 | Bar, Forging |
AMS 5861 | Plate, Sheet, Strip, Tubing |
EN 10088-3 | Bar, Wire, Hollow bar |
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 |
Forged ring | OD 30-350* ID 30-350 |
Plate | 1-25 * ≤1200 * ≤1200 |
Seamless tube | OD 6.0-200 * 0.6-20 |
Q1: What is the difference between 15-5PH and 17-4PH?
A1: Both are martensitic precipitation hardening grades. 15-5PH has lower chromium and refined microstructure with reduced delta ferrite. It delivers better transverse toughness and superior fracture toughness compared with 17-4PH, especially in large section sizes.
Q2: What heat treatment conditions are available for 15-5PH?
A2: Same H designation system as 17-4PH: H900, H1025, H1150. Raw material is usually supplied in Condition A (solution treated). Customers machine/forge parts then perform age hardening to the required H condition.
Q3: Is 15-5PH suitable for critical fastener applications?
A3: Yes. It is widely selected for high-strength critical fasteners where transverse toughness is required. Melting can be upgraded to VAR for premium aerospace or oil & gas projects.
Q4: Is 15-5PH magnetic?
A4: Yes, it is magnetic (martensitic precipitation hardening stainless steel).
Q5: How does corrosion resistance compare to 17-4PH?
A5: Corrosion performance is similar to 17-4PH. It is suitable for mild corrosive environments but not for heavy chloride or strong acid service.
Q6: What melting routes can you supply for 15-5PH bar?
A6: Standard air melt, premium Vacuum Arc Remelted (VAR) grade for high integrity applications to reduce non-metallic inclusions.