METHOD OF THERMAL HARDENING OF TUBE-MOLDING ROLL Russian patent published in 2002 - IPC

FIELD: thermal hardening of cast tube-molding rolls and profile bending rolls (rollers) made from hypereutectoid chromium steel. SUBSTANCE: proposed method includes heating to normalizing temperature, holding at heat, cooling and tempering. Roll is heated to temperature of 900 to 980 C and is kept at this temperature for 1.5 to 6.5 h, after which it is cooled at rate of 10 to 40 C/min; tempering is effected by heating to temperature of 180 to 400 C and holding at this temperature for 2 to 7 h. Provision is also made for performing cooling by jets of air or air- and-water mixture fed to axial passage of roll; said jets may be fed to axial passage from both sides of roll towards each other. According to another version, cooling the roll is effected to temperature of 100 to 200 C by jets of air or air-and-water mixture. EFFECT: enhanced resistance of roll and improved quality of tubes. 4 cl, 1 tbl, 3 ex