355 is a chromium-nickel-molybdenum stainless steel which can be hardened by martensitic transformation and/or precipitation hardening. It offers high strength at moderately elevated temperatures and good resistance to atmospheric corrosion and a number of other mild chemical environments. Depending upon the heat treatment, 355 alloy may have an austenitic structure and formability similar to other austenitic stainless steels or a martensitic structure and high strength comparable to other martensitic stainless steels. High strengths may also be attained by cold working, and are maintained (whether produced by heat treatment or by cold work) at temperatures up to 1000°F (538°C). Corrosion resistance of the alloy is superior to that of other quench-hardenable martensitic stainless steels and approaches that of the chromium-nickel austenitic stainless steels.