PRODUCTION OF NONNDIRECTIONAL SILICON STEEL SHEET HAVING LESS AGING DETERIORATION AND GOOD SURFACE PROPERTY

摘要

PURPOSE:To enable steel sheet having less aging deterioration and good surface property to be stably produced without carrying out decarburization treatment by a method wherein carbon content is lowered to below a specified amount of carbon in the production of non-directional silicon steel sheet having high Si-content. CONSTITUTION:In the production of from high grade to intermediate grade non-directionality silicon steel sheet containing from 1.5-3.5% of Si, residual carbon content in the steel sheet is lowered to below 0.0030-0.0025% and Al content is made to =0.15% or below 0.005% to avoid the formation of fine AlN which prevents crystal growth at the time of final annealing. When B is added to the steel, the amount of Al may be below 0.10% which is required for deoxidation, because AlN formation is controlled by B. B is added to the steel in such a proportion as to give a ratio of B/N of from 0.5-2.5. After the slab of the silicon steel having high Si-content and the above composition is hot-rolled, cold rolling is carried out once, or cold rolling including intermediate annealing without carrying out decarburization is carried out twice or more to produce steel sheet having final thickness. Then final annealing, which is not accompanied by decarburization, is carried out to produce non-directional silicon steel sheet having less aging deterioration and good surface property.