SAE 4042 is an alloy steel containing nominally 0.25% molybdenum. It combines moderate strength with good toughness in the quenched-and-tempered condition because it is relatively free from temper embrittlement when tempered in the range 850-1100 F. 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, joining, and surface treatment. Filing Code: SA-293. Producer or source: Alloy steel mills and foundries.