| 摘要 |
PURPOSE:To manufacture a grain-oriented silicon steel sheet having extremely high magnetic flux density, at the time of manufacturing a silicon steel sheet, by optimizing the annealing conditions of a silicon steel hot rolled sheet and executing nitriding treatment. CONSTITUTION:A silicon steel slab contg., by weight, 0.025 to 0.075% C, 2.5 to 4.5% Si, <0.015% S, 0.015 to 0.040% acid soluble Al, <0.010% N and 0.050 to 0.45% Mn or furthermore contg. specified amounts of Sn and Cr is subjected to hot rolling at <=1200 deg.C, is thereafter subjected to cold rolling for one time or <= two times including process annealing at >=80% final draft and is thereafter subjected to decarburizing annealing, and this steel sheet is subjected to nitriding treatment and is successively subjected to finish annealing. In the above process, the annealing before the final cold rolling is executed by two stage soaking, and in the case the temp. on the high temp. side therein is difined as T deg.C, between Al, (acid soluble Al-27/14XN) ppm and T deg.C, the relationship of 1240-2.1AlR,>1310-1.8AlR is retained. Then, it is soaked at the above temp. for <=180sec, is held to 700 to 950 deg.C for 30 to 300sec and is thereafter cooled to a room temp. at >=10 deg.C/sec cooling rate. |
