PROCESS FOR PRODUCING UNIDIRECTIONALLY GRAIN ORIENTED ELECTROMAGNETIC STEEL SHEET

摘要

A process for producing a unidirectionally grain oriented electromagnetic steel sheet having a primary recrystallization structure wherein Goss orientation grains and crystal grains of orientation in relationship corresponding to the Goss orientaion are aligned in the rolling direction. In the process, an electromagnetic steel slab containing by mass 0.025 to 0.10% C, 2.5 to 4.5% Si, 0.03 to 0.55% Mn and 0.007 to 0.040% Al is heated up to 1100° to 1450°C or higher, and hot rolled into a hot rolled sheet. The hot rolled sheet is sequentially subjected to annealing, cold rolling multiple times by means of a split housing cluster type reversing hot rolling machine, primary recrystallization annealing and secondary recrystallization annealing, thereby obtaining a unidirectionally grain oriented electromagnetic steel sheet. The process is characterized in that (a) the first cold rolling or first and second cold rollings are carried out with the use of a small-diameter work roll of 55 to less than 105 mm diameter, (b) the second or third to prefinal cold rollings are carried out with the use of a large-diameter work roll of 105 to less than 150 mm diameter, and (c) the final cold rolling is carried out with the use of a small-diameter work roll of diameter smaller than that of the large-diameter work roll.