PRODUCTION OF UNIDIRECTIONALLY ORIENTED SILICON STEEL PLATE HAVING HOMOGENEOUS FORSTERITE INSULATING FILM

摘要

PURPOSE:To form a homogeneous forsterite film having excellent appearance by producing a unidirectionally oriented silicon steel plate by cold rolling then subjecting the steel sheet to decarburization annealing under specific atmosphere oxidizability and temp. conditions thereby adjusting the rate between the fayalite and silica in the subscale on the surface of the steel plate. CONSTITUTION:A raw material for a unidirectionally oriented silicon steel plate contg. 0.01-0.06% C and 2.0-4.0% Si, contg. at least one of 0.008-0.1% S and 0.003-0.1% Se as an inhibitor and contg. further 0.003-0.1% Mo is finished to a final sheet thickness by one hot rolling and >=1 time of cold rolling including intermediate annealing. The plate is subjected to primary recrystallization/decarburization annealing under the conditions of 820-860 deg.C atmosphere temp. and 0.30-0.50 atmosphere oxidizability expressed by the partial pressure ratio PH2O/PH2 between H2O and H2. The ratio (Fe2SiO4)/SiO2 between fayalite and silica in the subscale on the surface of the steel plate is adjusted to 0.05- 0.45 and the plate is subjected to final finish annealing. The grain-oriented silicon steel plate having the homogeneous foresterite insulating film of good appearance and an excellent magnetic characteristic is thus produced.