FORMATION OF GOOD-QUALITY PRIMARY INSULATING FILM ON GRAIN-ORIENTED SILICON STEEL SHEET

• Main Authors: MUNETA KOUJI, KITAHARA SHUJI, ISHII SHINYA
• Format: Patent
• Language: English
• Published: 25.09.1990
• Subjects: BASIC ELECTRIC ELEMENTS; CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; ELECTRICITY; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; INDUCTANCES; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; MAGNETS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; TRANSFORMERS

PURPOSE:To improve the external appearance and adhesive strength of an insulating film by carrying out the annealing of a hot rolled silicon steel plate at a specific temp. or above in a combustion-gas atmosphere in which air ratio is regulated to a specific value and also specifying a partial pressure ratio between PH2O and PH2 in the atmosphere at the time of decarburizing annealing. CONSTITUTION:The hot rolled plate annealing of a silicon steel which has a composition consisting of, by weight ratio, 2.5-4.5% Si, 0.02-0.12% C, 0.02-0.2% Mn, 0.015-0.04% acid soluble Al, 0.0040-0.01% N, 0.01-0.04% S, and the balance essentially Fe and further containing <=0.04% of one or >=2 elements among Sn, Cu, and Sb is carried out in a temp. region of >=500 deg.C in a combustion-gas atmosphere in which area ratio is controlled to 1.0-1.5. Further, the partial pressure ratio between PH2O and PH2 in the atmosphere at the time of decarburizing annealing is regulated to 0.30-0.45, by which a grain-oriented silicon sheet with high magnetic flux density is produced. By this method, the external appearance and adhesive strength of an insulating film can be improved while obviating the necessity of treatment prior to decarburizing annealing.