Effect of the Chemical Composition and Structure of EP682-Sh and R6M5 High-Speed Steels on Their Hardness and Impact Toughness

The hardness and impact toughness of high-speed steels EP682-Sh (R12FZK10M3-Sh) and R6M5 are studied, and methods for increasing their hardness are proposed. The optimum ratio of the carbon to vanadium content (C/V = 0.42) is determined; at this ratio, the hardness of the EP682-Sh steel of the modified composition after tempering at 520°C for 1 h performed six times is 71–72 HRC. After radial-shear rolling, high-speed steel is shown to be a precipitation-hardened composite material with uniformly distributed carbide particles, which increases the impact toughness and decreases the risk of cracking in rolling.