| 摘要 |
PROBLEM TO BE SOLVED: To obtain an ultralow core loss grain-oriented steel sheet improved in core loss, an occupying volume rate and adhesion at a low cost by forming two or more layers of ceramic tension coating composed of nitride and/or carbide on the surface of a steel sheet after bright annealing. SOLUTION: This ultralow core loss silicon steel sheet is the one in which, on a thin TiN formed on the surface, two layers of thin nitride series ceramic coating on which Si3 N4 extremely small in a thermal expansion coefficient and having insulating properties is formed are applied. At the time of producing this, in the case of final finish annealing, as separation agent for annealing, forsterite generating suppression type one contg. inert MgO, Al2 O3 or the like is used. After the final finish annealing, bright annealing is executed at 900 to 1300 deg.C to clean the surface of the steel sheet. After that, on the surface of the steel sheet, two or more layers of ceramic tension coating composed of nitride and/or carbide are formed. In this way, the advantageous improvement of its core loss characteristics can be attained. |
