GRAIN ORIENTED SILICON STEEL SHEET HAVING LOW IRON LOSS WITHOUT DETERIORATION OF CHARACTERISTIC BY STRESS RELIEF ANNEALING AND ITS PRODUCTION

摘要

PURPOSE:To provide a grain oriented silicon steel sheet having an excellent iron loss characteristic with which a plastic strain area is not observed in the surface layer part of the base iron and which is not deteriorated in characteristic even if the sheet is subjected to stress relief annealing by forming a different thickness region to the forsterite film in the surface layer part of the base iron. CONSTITUTION:A hot rolled steel sheet consisting of a silicic steel contg. about 2.0-4.0% Si is subjected to one pass or two passes of cold rolling including intermediate annealing to a final thickness. A separating agent for annealing consisting essentially of MgO is locally coated (so as to form the uncoated region of the separating agent) on the surface of the steel sheet having the final thickness. The steel sheet treated in such a way is subjected to secondary recrystallization and the high temp. purification annealing (final finish annealing) in succession thereto to form an ordinary forsterite film on the surface coated with the separating agent for annealing. More specifically, a reduced thickness region is formed between said film and the part where said agent is not coated. As a result, the grain oriented silicon steel sheet which is so formed that the actual record in segmentation of the magnetic domain width of the product is assured without deteriorating the characteristic even after stress relief annealing at a high temp. is obtd.