Lescalloy 17-4 Vac-Arc is special melt version of a well-known precipitation-hardening martensitic stainless steel. 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, machining, and joining. Filing Code: SS-1040. Producer or source: Latrobe Specialty Steel Company.