PRODUCTION OF DIRECTIONAL SILICON STEEL PLATE

摘要

PURPOSE:To produce a titled steel plate having forsterite ceramics insulating films free from defects in the stage of degreasing a cold rolled steel plate of final thickness electrolytically in an alkali degreasing bath by maintaining the concn. of Fe ions the bath at values lower than prescribed concn. CONSTITUTION:After a blank slab is hot-rolled, the slab is subjected to >=1 time of cold rolling including intermediate annealing whereby the cold-rolled plate of final thickness is obtained. The cold-rolled plate is electrolytically degreased in an alkali degreasing bath wherein Fe ions are maintained at <=500mg/l total content of iron. The degreased plate is supplied to a decarburization treatment to form oxide layers consisting essentially of SiO2 on the surfaces of the cold- rolled plate. After an annealing separating agent consisting essentially of MgO is coated on the surface of such steel plate, the steel plate is coiled to a steel plate coil. The coil is subjected to annealing in gaseous hydrogen flow of a high temp. to form films of foresterite ceramics (2MgO.SiO2) uniformly on the surfaces thereof. Thus the directional silicon steel plate is produced.