The annealing separable medicine and glass coat of the directivity electromagnetic steel sheet and the production mannered null magnesia of the directivity electromagnetic steel sheet where

摘要

PROBLEM TO BE SOLVED: To obtain a grain oriented silicon steel sheet having extremely excellent glass film and magnetic properties by using a separation agent at annealing where the reactivity of film-forming reaction is regulated. ;SOLUTION: A hot rolled plate, containing 0.03-0.100% C and 2.5-4.5% Si, is subjected, after or without annealing, to cold rolling once or twice while process-annealed between two cold rolling stages to final sheet thickness, and the resultant sheet is subjected, in succession, to decarburizing annealing, to application of a separation agent at annealing, to finish annealing, to insulation coating treatment, and then to heat flattening, by which the grain oriented silicon steel sheet is produced. In this case, as the separation agent at annealing to be applied to the steel sheet after decarburizing annealing, the following MgO is used: an MgO in which CAA 70% value, CAA 70% value/CAA 40% value, grain size %20 value, and BET value are regulated to 250-1000 sec, 1.5-6.0, ≤1.2 μm, and (15 to 35) m²/g, respectively, where CAA 70% and CAA 40% mean the activities (sec) of citric acid until respective reaction ratios are reached, the maximum grain size (μm) at the count number 20% point when the grain size distribution measured by the laser diffraction method is integrated from the small- grain side, and the specific surface area (m²/g) of MgO measured by the N adsorption method, respectively. Further, 200-1500 ppm fluorine is incorporated into the above MgO.;COPYRIGHT: (C)1999,JPO