Low iron loss grain-oriented silicon steel sheet whose properties do not deteriorate due to stress relief annealing

摘要

PURPOSE:To prevent characteristics from being deteriorated due to stress relieve annealing, by making a foreign matter, whose composition is different from that of a base iron part, locally exist on a base iron surface layer part of a grain oriented silicon steel plate which is coated with a forsterite film. CONSTITUTION:A foreign matter, whose composition is different from that of a base iron part, is made to exist on a base iron surface layer part of a directive silicon steel plate which is coated with a forsterite film and has no plastic strain region on the base surface layer part. Further, the forsterite film is coated with an insulating film which is of tension application type and is 9.8X10-61/ deg.C or less in its coefficient of thermal expansion. Now that surface tension is applied depending on a difference between the coefficient of thermal expansion of the steel plate and that of the coating film, there must be a degree of the difference between said coefficients in order to determine a species of coating processes. In this respect, however, if the coefficient of thermal expansion is 9.8X10-61/ deg.C or less in the coating, a satisfactory valve of low iron loss can be obtained from an synergistic effect which consists of an effect of forming a region, where the foreign matter exists on the base iron surface layer part, and an effect of surface tension application by the coating film.