Orange 4cr13

420 stainless steel is a martensitic higher carbon version of types 410 and 416 stainless that can be hardened by heat treatment. It contains a minimum of 12 percent chromium, sufficient to give 420 corrosion resistance properties. It has good ductility in the annealed condition but is capable of being hardened up to 50 RHC. Its best corrosion resistance is achieved when 420 is hardened and surface ground or polished. In the hardened condition, 420 has good corrosion resistance to the atmosphere, foods, fresh water, mild alkalies and acids, steam, sterilizing solutions, crude oil, gasoline, and other similar corrosive media. The higher carbon content employed in 420 gives higher strength and hardness over stainless grades 410 and 416. In the annealed condition, 420 is relatively easy to machine, but if hardened to above 30 HRC, machining becomes more difficult. Fabrication must be by methods allowing for poor weldability and usually allow for a final harden and temper heat treatment. 420 is not recommended for use in temperatures above the relevant tempering temperature, because of reduction in mechanical properties. The scaling temperature is approximately 650F.