We present the results of the study of a nature of damages of three-cone rock bits that have premature lost their workability. Physical-mechanical and metallographic indices of melting steel of cone bit with brittle fracture are established. The distribution of carbon concentration and hardness in hardened carburized layers of cone bit is studied. Metallographic analysis of the most common steels used in the worldwide practice of cone bits manufacturing is performed to find ways to prevent premature loss of cone bits' workability. The chemical composition and physical-mechanical and technological parameters are established, on the basis of which the conceptual requirements for the choice of steel and the quality of the technology of cone bits' strengthening are formulated for domestic production.