SK300 series, the materials are the special alloy steel for making screw which are imported from Japan and Germany.Trough 1080℃ vacuum quenching and three times of 570℃ tempering, four hours one time. The hardness will be HRC50-52, good function of toughness, softening resistance in high temperature, common function of anti-wear and corrosion. Alloy compsition: C:0.42, Cr:5.5,Mo:1.5,Si:1.2, W:1.0, V:1.2, Co:1.4

Universal screw standard material, good toughness and softening resistance in high temperature make them fit for the application below 30% GF