AISI 4063 is a low-molybdenum alloy steel, recommended for heavy duty applications requiring strength and toughness with decrease in temper brittleness. This datasheet provides information on composition, hardness, and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, machining, and joining. Filing Code: SA-84. Producer or source: Alloy steel mills and foundries.