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 about 0.4%) are mostly used for cutting tools: Cutlery, Razor blade steel, Blender blades, etc. Replacing some of the Carbon in martensitic stainless steels by Nitrogen is a fairly recent development. The limited solubility of Nitrogen has been increased by the PESR process (Pressure Electroslag Refining) in which melting is carried out under a high nitrogen pressure. Up to 0.4% N contents have been achieved leading to higher hardness/strength and higher corrosion resistance. As the PESR is expensive, lower but significant N contents have been achieved using the standard AOD process. They are magnetic. They are not as corrosion resistant