Method of producing grain oriented silicon steel sheet having low iron

Abstract

A method of producing a grain oriented silicon steel sheet is adapted to lower the iron loss. A silicon steel slab, containing about 2.0 to 4.0 weight % of Si and an inhibitor-forming amount of S, or Se, or both, is hot rolled. After the hot rolled steel sheet is annealed when necessary, the steel sheet is cold rolled into a cold rolled steel sheet having a final thickness by performing cold rolling either one time or a plurality of times with intermediate annealing therebetween, the cold rolled steel sheet then being subjected to decarburization, coating of the surface of the steel sheet with an annealing separation agent mainly comprising MgO, secondary recrystallization annealing, and purification annealing. In the cold rolling step, an oxide layer exists on the surface of the steel sheet. Specifically, in the cold rolling step, rolling oil is supplied only at the entrance of the rolling mill used, and an oxide layer having a thickness of about 0.05 to 5 .mu.m is generated. Or, an outer oxide layer of an oxide layer structure generated on the surface of the steel sheet after hot rolling or intermediate annealing, is removed, and an inner oxide layer of a thickness of about 0.05 to 5 .mu.m is maintained on the surface, the resultant steel sheet then being subjected to cold rolling.