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Precipitation hardening stainless steels are designed to be formable in the solution annealed condition and can subsequently be hardened by heat treating to strength levels several times that of Type 304. Corrosion resistance is usually better than that of straight chromium ferritics.
Precipitation hardening stainless steels develop very high strength through a low-temperature heat treatment that does not significantly distort precision parts. These are chromium and nickel containing steels that can develop very high tensile strengths. The most common grade in this group is 17-4 PH, also known as Grade 630, with the composition of 17% chromium, 4% nickel, 4% copper and 0.3% niobium. The great advantage of these steels is that they can be supplied in the "solution treated" condition. In this condition the steel is just machineable. Following machining, forming etc. the steel can be hardened by a single, fairly low temperature "ageing" heat treatment which causes no distortion of the component.
These alloys are used where high strength, moderate corrosion resistance, and good fabricability are required. Typical applications include shafting, high-pressure pumps, aircraft components, high-temper springs, and fasteners. |