Tempering is a heat treatment process in which quenched metal is reheated to a specific temperature below the lower critical temperature, held for a certain period, and then cooled. The purpose is to eliminate residual stresses generated during quenching, reduce the hardness and strength of the metal, and improve the material's ductility and toughness. This process represents the tempering of 1 kg of steel, yielding 0.997 kg of tempered steel, and should be used in conjunction with production data for 1 kg of steel. The data are sourced from the production processes of bearings, steel shot, cutting blades, rollers, and other mechanical and electrical equipment components.