PRODUCTION OF GRAIN ORIENTED MAGNETIC STEEL THICK SHEET EXCELLENT IN MAGNETIC PROPERTY AND FILM CHARACTERISTIC

摘要

PURPOSE: To stably produce a grain oriented magnetic steel thick sheet having superior magnetic properties and film characteristics by subjecting a slab of specific composition to hot rolling, annealing, and cold rolling and further subjecting the resulting sheet to decarburizing annealing and final finish annealing. ;CONSTITUTION: A steel slab, containing, by weight, 0.021-0.075% C, 2.5-4.5% Si, 0.01-0.06% acid soluble Al, 0.0010-0.0130% N, 0.014% S+0.405Se, and 0.05-0.8% Mn, is heated to 1280°C and hot-rolled into a plate of 2.8-5.0mm thickness. This hot rolled plate is annealed and cold-rolled at 80% draft. The resulting cold rolled sheet is further subjected to decarburizing annealing consisting of holding at 830°C for 400sec and then to heat treatment in a gaseous NH₃ containing atmosphere at 750°C for 30sec to undergo nitriding. Finally, a separation agent at annealing, composed essentially of MgO, is applied and finish annealing is done at 1200°C and then an insulating film agent is applied, by which a finished goods of 0.36-1.00mm thickness can be produced. At this time, the relation in inequality is satisfied among the Al% and N% in the slab and the thickness (t)mm of the cold rolled sheet, by which the grain oriented magnetic steel sheet excellent in magnetic properties can be produced.;COPYRIGHT: (C)1995,JPO