Description
Stainless steel 15 – 5 PH, also known as XM-12 or UNS S15500, is a modification of 17-4 PH developed in the 1960s. It has a more refined microstructure obtained through the remelting process. This refined structure improves toughness of the material. UNS S15500 also has low temperature hardening, good fabrication properties and excellent corrosion resistance, which makes it suitable for many industries. It can be machined in the solution-annealed state or in final heat treat condition. The strength and ductility of UNS S15500 can be enhanced through heating the material at different temperatures.
UNS S15500 is a martensitic precipitation hardening type stainless steel. Martensitic stainless steels were designed to be corrosion resistant and hardened through heat treatment.
Chemical Composition
The chemical composition of Grade 15-5 PH stainless steel is outlined in the following table.
| Element | Content (%) |
|---|---|
| Iron, Fe | 75 |
| Chromium, Cr | 14.48 |
| Nickel, Ni | 4.5 |
| Copper, Cu | 3.5 |
| Manganese, Mn | ≤1 |
| Silicon, Si | ≤1 |
| Nb + Ta | 0.3 |
| Carbon, C | ≤0.07 |
| Phosphorous, P | ≤0.04 |
| Sulfur, S | ≤0.03 |
Mechanical properties
The mechanical properties of Grade 15-5 PH stainless steel are displayed in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Tensile Strength | 1380 MPa | 200000 psi |
| Yield Strength | 1275 MPa | 184900 psi |
| Modulus of Elasticity | 200 GPa | 29000 ksi |
| Elongation at Break | 10% | 10% |
| Hardness, Brinell | 420 | 420 |
| Hardness, Knoop | 451 | 451 |
| Hardness, Rockwell B | 104 | 104 |
| Hardness, Rockewell C | 44.2 | 44.2 |
| Hardness, Vickers | 445 | 445 |
| Charpy Impact | 10 J | 7.38 ft.lb |
Manufacturing process
UNS S15500 can be machined under any of the attainable conditions. Firstly, the alloy is mildly formed in the overaged condition. It is then welded using welding techniques such as shielded fusion or resistance methods. The material is heat treated at 1038°C (1900°F) for 1/2 h, and then air cooled. This process is followed by hot-working the material and annealing at 1038°C (1900°F) for 1 h. Finally, the alloy can be cold-worked to improve its yield strength.
Applications
The following are some of the major applications of Grade 15-5 PH stainless steel:
- Marine gas turbine compressor sections
- Hallow shafts
- Paper mill equipment
- Engine parts
- Aircraft components
- Gears
- Fittings and fasteners
- Nuclear reactor components
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