METHOD OF PRODUCING NONORIENTED ELECTRICAL GRADE SHEET WITH HIGH COHESION OF INSULATING COATING LAYER Russian patent published in 1999 - IPC

FIELD: methods of production of nonoriented electrical grade sheet with high cohesion of insulating coating layer. SUBSTANCE: method may be used in manufacture of steel cores for electrical machines such as electric motors, electric generators, small transformers, etc. Method includes production of slab from steel containing the following components, wt.%: C, within 05; Si, within 0.15; Mn, within 1.5; P within, 0.15; S, within, 0.015; Al, within 1.0; one or more elements taken from group (having, %: Bn, 0.03-0.30; Sb, 0.03-0.3; Ni, 0.03-1.0; and Cu, 0.03-0.50), Fe, the balance, and other inevitable impurities. Steel slab is heated and subjected to hot rolling. Hot-rolled steel slab is pickled after annealing or without it. Pickled hot-rolled steel sheet is subjected to cold rolling, low-temperature annealing at temperature of 750-850 C for 0.5-5 min in damp atmosphere with dew point of 25-65 C. Then high-temperature annealing of cold-rolled steel sheet is performed at temperature of 800-1070 C for duration from 10 s to 3 min in dew atmosphere with dew point of 0 C or below. Surface of steel sheet after the treatment is coated with layer of insulating coating and subjected to hardening heat treatment. EFFECT: improved strength of cohesion of insulation coating layer of steel sheets. 6 cl, 6 tbl