METHOD OF HEAT TREATMENT OF MEDIUM-CARBON STEEL Russian patent published in 2002 - IPC

FIELD: metallurgy and mechanical engineering; heat treatment of parts made from medium-carbon steels for work at low temperatures. SUBSTANCE: proposed method includes normalizing and tempering of part at 655 to 750 C for 120 to 300 min, cooling in air and repeated normalizing at 10 to 50-min holding. Tempering (process annealing) at temperature of 655 to 750 C performed for 120 to 300 min ensures forming of fine-grained perlitic-ferritic microstructure. Rise of tempering temperature and conducting repeated normalizing cause activation of additional centers for forming fine austenite grains in heating of parts during repeated normalizing. EFFECT: increased indices of impact strength and stability at low temperatures; improved strength characteristics of steel. 1 tbl, 6 ex