| 摘要 |
PROBLEM TO BE SOLVED: To stably produce a grain-oriented silicon steel sheet excellent in magnetic properties and small in core loss by subjecting a cold rolled sheet of high silicon steel to surface treatment under specified conditions and thereafter executing decarburizing annealing and final finish annealing. SOLUTION: A high silicon steel slab is subjected to hot rolling and cold rolling to form into a thin sheet, which is thereafter subjected to process annealing in a wet nitrogen atmosphere and is cooled to an ordinary temp. by water cooling or air cooling. Next, scales on the surface of the steel sheet are lightly removed, thereafter, it is subjected to cold rolling to regulate its sheet thickness to a final one, and the amt. of oxides on the surface is regulated to 0.05 to 0.35g/m<2> by the oxygen coating weight. Furthermore, the steel sheet is subjected to electrolytic degreasing cleaning to regulate the amt. of electrodepositions on the surface to 0.1mg/m<2> . After that, it is subjected to decarburizing annealing composed of the early period in which the ratio of partial pressure of steam to the partial pressure of hydrogen in the atmosphere is regulated to 0.30 to 0.65 and the latter period in which decomposing reforming high densitifying treatment for oxides on the surface of the steel sheet is executed in the atmosphere in which the temp. is regulated to 850 to 950 deg.C and the partial pressure of steam is regulated to 0.65 to 3.0%, is successively coated with a separation agent for annealing essentially consisting of MgO and is subjected to final finish annealing. Thereby, the grain-oriented silicon steel sheet having high magnetic flux density and low core loss characteristics can be produced. |
