PRODUCTION OF ULTRA-LOW IRON LOSS GRAIN ORIENTED SILICON STEEL SHEET FREE FROM DETERIORATION IN CHARACTERISTIC EVEN AFTER STRESS RELIEF ANNEALING

摘要

PURPOSE:To improve the adhesiveness and durability of a tensile coating layer and to obtain the titled steel sheet in a method for improving the iron loss of a grain oriented silicon steel sheet by finishing the same to a specular surface by forming the tensile film consisting of a specific material and having a specific thickness by a CVD method to the specular surface having the specified roughness. CONSTITUTION:A hot rolled sheet of a silicon steel slab is subjected to one pass or two passes of cold rolling including intermediate annealing to a final sheet thickness. The sheet is then subjected to decarburization and primary recrystallization annealing and after a separating agent for annealing essentially consisting of MgO is coated on the surface of the steel sheet, the steel sheet is subjected to final finish annealing. The steel sheet is thereafter pickled to remove the forsterite type underlying film on the surface and the surface is chemically polished and is thereby finished to the specular surface having =0.4mu center line average height. The tensile film essentially consisting of =1 kinds among the nitrides and/or carbides of Ti, Nb, Si, V, Cr, Al, Mn, B, Ni, Co, Mo, W, Zr, Hf and Ta are formed by a CVD method to 0.005-5mu thickness on such surface.