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
Duplex stainless steel are higher. This can be a great advantage when strength is important. This is the case in bridges, pressure vessels or tie bars. Chemicals composition of grades from EN 10088-1 (2014) Standard are given in the table below: Mechanical properties from European Standard EN 10088-3 (2014) (for product thickness below 160mm): <nowiki>*</nowiki>for thickess ≤ 5 mm The minimum yield stress values are about twice as high as those of austenitic stainless steels. Duplex grades are therefore attractive when mechanical properties at room tempearature are important because they allow thinner sections. Duplex stainless steel Duplex stainless steels is the most recent