GB749609A - Method of inductively hardening the surfaces of rolls - Google Patents

Abstract

A method of inductively hardening the surface of cast or wrought rolls comprises gradually heating the surface of the rolls until the surface temperature is fairly uniform and below the hardening temperature and then raising the surface temperature to the hardening temperature and quenching. The fairly uniform temperature, i.e. above 600 DEG C. and preferably 750 DEG C., may be attained by the use of an inductor surrounding the roll and moved relatively thereto during which time the roll may be rotated, or by an inductor loop running the length of the roll and partly surrounding it, the roll being rotated. The heating may be performed in such a manner as to prevent over-heating of the ends of the rolls and may be step-by-step, preferably three steps. Two such heating treatments may be used, the roll being cooled between each heating. The heating to the hardening temperature may be carried out rapidly and after quenching the roll may be stress relieved or tempered also by induction heating. The frequencies used may vary from mains frequency to 500 or 2000 cycles per second depending on the size of the roll.