Abstract Armco 420 is an iron-chromium stainless steel with added carbon content (0.3% nominal) for higher hardness. The alloy is ferritic in the annealed condition and martensitic after rapid cooling in air or a liquid medium from above the critical temperature. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-781. Producer or source: Armco International Sales.