| 摘要 |
PROBLEM TO BE SOLVED: To produce a grain-oriented silicon steel sheet excellent in magnetic properties by subjecting a high silicon steel slab to hot rolling under specified temp. conditions to form into a sheet material and next subjecting the same to cold rolling, decarburizing annealing and final finish annealing without executing hot rolled sheet annealing. SOLUTION: A high silicon steel slab contg., by weight, 0.025 to 0.075% C, 2.5 to 4.5% Si, 0.01 to 0.060% acid soluble Al and 0.0010 to 0.0130% N or furthermore contg. 0.005 to 0.020% (S+0.405 Se) and 0.05 to 0.8% Mn is heated at <1,280 deg.C and is subjected to hot rolling to form into a hot rolled sheet. Without executing hot rolled sheet annealing, the above hot rolled sheet is subjected to cold rolling at 80% draft to form into a thin sheet, which is thereafter subjected to decarburizing annealing and final finish annealing. In this case, the hot rolling finishing temp. in the hot rolling stage is regulated to 750 to 1,100 deg.C, which is coiled round a coil, is held for 1sec to 60min at 700 to 1,050 deg.C, is thereafter recoiled at 750 to 950 deg.C, is cooled, is again coiled round a coil at 500 deg.C to regulate the average grain size of primarily recrystallized grains to 18 to 35μm and is subjected to nitriding treatment in such a manner that the amt. of nitrogen to be increased is regulated to >=0.0010%. |
