Process for producing a grain-oriented electrical steel sheet by means

Abstract

The present invention concerns a process for producing a grain-oriented electrical steel sheet by means of a rapid quench-solidification process, for example, a continuous casting by a twin roll strip caster. The feature of the present invention resides in quenching to solidify molten steels into a thin cast sheet of 0.7 to 3.0 mm thickness, at a cooling rate of greater than 50.degree. C./sec. in the central portion along the direction of thickness of the thin cast sheet, cooling the sheet at a cooling rate of greater than 10.degree. C./sec. in a temperature range between 1300.degree. to 900.degree. C. and then applying cold rolling for once or twice or more annealing the thin cast steel for a period between 30 seconds and 30 minutes in a temperature range between 950.degree. and 1,200.degree. C. and subsequently including intermediate annealing under a final cold rolling reduction rate of not less than 80%. In the present invention, precipitates that function as an inhibitor can finely be dispersed by adding 0.02 to 0.2% of Nb into the molten steel ingredients thereby to stably produce a grain-oriented electrical steel sheet of high magnetic flux density by means of a rapid quench-solidification process. Further, since a thin cast sheet of desired thickness within a range from 0.7 to 3.0 mm can be produced by the rapid quench-solidification process, the thin cast sheet can be cold rolled to a final thickness of less than 150 .mu.m by applying a cold rolling at a reduction rate optimum to magnetic properties, and an extremely thin grain-oriented electrical steel sheet of less than 150 .mu.m (0.15 mm) thickness can be produced in a simple production process and at a reduced cost, which so far has been remarkably difficult and expensive to produce.