GB983454A - A method of surface hardening steel rolls and apparatus for carrying out the same - Google Patents

Abstract

In the surface hardening of steel rolls, the depth of hardened zone is increased by using a high electrical power density for heating, which may be either conductive or inductive, while simultaneously cooling the surface. Cooling is then discontinued and the temperature of the treated zone allowed to equalize to a temperature above the critical, aided if necessary by supplementary heating, after which the roll is quenched. The whole surface may be treated at one time, or treatment may be progressive. Pior to hardening the surface region may be preheated to about 750 DEG C. using a low power density and no cooling. As shown in Fig. 1, roll 1 is moved axially through inductive heating coil 3, coolant being supplied between the turns of the coil at 4. Temperature equalization occurs at 6, and the roll then passes through annular quenching spray 7. In the embodiment of Fig. 2, the roll is simultaneously rotated and advanced axially, heating being carried out by inductor loops 9 between which the located coolant sprays 11. Fig. 5 illustrates a modification using conductive heating, the contact rollers or slippers being placed at location 7 or 3 depending on whether or not the hardened zone is to extend to the edge of the cylindrical part of the roll body.