AISI No. 618 is a general purpose, high temperature alloy steel that can be hardened to high strength and hardness levels. It maintains good hot hardness. This datasheet provides information on composition, physical properties, hardness, and elasticity as well as fracture toughness. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-172. Producer or source: Alloy steel mills and foundries.