Alloy Steel 4520 (Nonstandard, formerly AISI-SAE 4520) is a 0.50% molybdenum steel well suited for use in carburized and non-carburized applications. It has a yield strength of around 50,000 psi in the normalized condition and from 50,000 to 65,000 psi in the quenched and lightly tempered condition (depending on section thickness and tempering temperature). Its uses include railway cars, bridge construction and carburized parts such as gears. 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-357. Producer or source: Alloy steel mills and foundries.