PRODUCTION OF GRAIN ORIENTED SILICON STEEL SHEET HAVING EXTREMELY LOW IRON LOSS AND EXTREMELY HIGH MAGNETIC FLUX DENSITY

摘要

PURPOSE: To stably obtain a grain oriented silicon steel sheet having extremely high magnetic flux density by using a steel slab having a Bi-added specific composition as a starting material and specifying the flow rate of atmospheric gas at finish annealing. ;CONSTITUTION: A slab, having a composition consisting of, by weight, 0.03-0.15% C, 2.5-4.0% Si, 0.02-0.30% Mn, 0.005-0.040% S and/or Se, 0.015-0.040% acid soluble Al, 0.0030-0.0150% N, 0.0005-0.05% Bi, and the balance Fe, is heated and hot-rolled. The resulting hot rolled plate is finished to product sheet thickness by being subjected to hot rolled plate annealing and to finish cold rolling, or by being cold-rolled plural times while process-annealed between cold rolling stages, or by being subjected to hot rolled plate annealing and then cold-rolled plural times while process-annealed between cold rolling stages. Then, decarburizing annealing is performed. After the application of a separation agent at annealing, finish annealing is done. In this manufacturing method, the flow rate of atmospheric gas at finish annealing is regulated to a value in the range satisfying (flow rate of atmospheric gas)/(furnace volume) ≥0.5Nm³/(h.m³). By this method, the grain oriented silicon steel sheet with extremely high magnetic flux density, having ≥1.92T magnetic flux density B₈, can be stably obtained.;COPYRIGHT: (C)1997,JPO