17-4 stainless steel for 17-4 include components which require high hardness and/or corrosion resistance at temperatures of up to . Specific applications for 17-4 include the petroleum and chemical industries, as well as use in aircraft parts. 17-4 stainless steel SAE type 630 stainless steel (more commonly known as 17-4; also known as UNS 17400) is a grade of martensitic precipitation-hardened stainless steel. It contains approximately 15–17.5% (17) chromium and 3–5% (4) nickel, as well as 3–5% copper. 17-4 can be heat treated to high levels of strength and hardness, and features corrosion resistance and machinability comparable to austenitic 304 stainless. Being martensitic,
Stainless steel grades typically EN1.4913 or 1.4923 are used in parts of turbochargers, other heat resisting grades for EGR (Exhaust gas recirculation) and for inlet and exhaust valves. In addition, common rail injection systems and particularly the injectors rely on stainless steels. Stainless steel has proved to be the best choice for miscellaneous applications, such as stiffeners for windshiel wiper blades, balls for seat belt operation device in case of accident, springs, fasteners, etc. The aft body panel of the Porsche Cayman model (2-door coupe hatchback) is made of stainless steel. It was discovered during early body prototyping that conventional steel could