AISI 4145 is a through-hardening, medium-carbon chromium-molybdenum steel recommended for heavy-duty service. It is suitable for a wide variety of engineering uses. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-285. Producer or source: Alloy steel mills and foundries.