Manufacturing method of high magnetic flux density unidirectional electrical steel sheet with good iron loss characteristics

摘要

PURPOSE:To improve iron loss and to attain superior adhesive strength of film by adding a Ca compound containing Ca in an amount corresponding to S content into a separation agent at annealing at the time of annealing a steel sheet in which S content is controlled. CONSTITUTION:A steel sheet having a composition consisting of, by weight ratio, 1.5 to 4.5% Si, 0.012 to 0.040% acid soluble Al, =0.0095% T(tolal). N, 0.005 to 0.014% S, and the balance Fe with inevitable impurities is cold-rolled once or is subjected to plural cold rollings while interposing process annealing between the cold rolling stages to the final sheet thickness. Subsequently, the above steel sheet is subjected to decarburizing annealing in warm hydrogen. Successively, a separation agent at annealing in which a Ca compound containing equivalent Ca 0.6 to 2.2 times the amount of S contained in the steel sheet is added is applied to the above steel sheet and dried, and the above sheet is then subjected to finish high temp. annealing intended for the secondary recrystallization and purification. By this method, a grain-oriented silicon sheet in which iron loss comparable to that of a material after magnetic domain fractionization treatment is attained and which has high magnetic flux density can be obtained.