| 摘要 |
PURPOSE:To improve the core loss properties in a steel sheet, to execute finish annealing at a low temp. in a short time and to reduce the production cost by subjecting a silicon steel to decarburizing annealing in an atmosphere in which oxides are not formed and promoting its purification at the time of finish annealing by using alumina. CONSTITUTION:A silicon steel contg., by weight, 0.8 to 4.8% Si, 0.012 to 0.05% acid soluble Al, <=0.01% N, <=0.012% S, and the balance Fe is melted. The steel strip of this steel is rolled by regulating its sheet thickness into a final one, is subjected to decarburizing annealing and nitrogen increasing treatment and is subsequently subjected to finish anealing by using a separation agent for annealing (alumina) between the sheets, and the surface is formed into a mirror face. At this time, the decarburizing annealing is executed in a wet hydrogen atmosphere or the like to prevent the formation of Fe series oxides. Moreover, at the time of laminating the decarburized sheet, alumina is used as a separation agent for annealing to promote the purification of the steel sheets at the time of the finish annealing, and the purification in the finish annealing is executed at a temp. T( deg.C)>=1100, for time (t) (hr) expressed by 62-T/20 to 297-T/4. |
