17-4 stainless steel 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, 17-4 is magnetic. 17-4 is capable of being hardened up to approximately 44 Rc when heat treated to condition H900. Overaging (aging beyond the peak strength condition) improves resistance to stress corrosion cracking. Uses
Martensitic stainless steel announced two years later in a January 1915 newspaper article in "The New York Times". Brearly applied for a U.S. patent during 1915. This was later marketed under the ""Staybrite"" brand by Firth Vickers in England and was used for the new entrance canopy for the Savoy Hotel in 1929 in London. Martensitic stainless steel Martensitic stainless steel is a specific type of stainless steel alloy. Stainless steels may be classified by their crystalline structure into three main types: "austenitic", "ferritic" and "martensitic". Martensitic stainless steels can be high- or low-carbon steels built around the Type 410 composition of iron,