| 摘要 |
PURPOSE:To obtain good magnetic properties even if hot rolled sheet annealing is obviated by controlling the heating temp. in a hot rolled steel sheet in which C, Si, Al, N or the like are specified based on the contents of acid soluble Al and N, controlling the cumulative draft in rough hot rolling, the grain size of primarily recrystallized grains or the like and executing nitriding treatment. CONSTITUTION:A steel having a compsn. contg., by weight, <=0.075% C, 2.2 to 4.5% Si, 0.01 to 0.06% acid soluble Al, <=0.013% N, S+0.405Se; <=0.014% or the like is melted. This slab is heated to <1280 deg.C, is subjected to final forced draft cold rolling at >=80% draft and 15 annealed. At thus time, the slaf heating temp. ST( deg.C) is controlled to <=950+9500X {Al(%)-(27/14)XN(%)}, the cumulative draft in rough hot hot rolling and finish hot rolling is regulated to >=1sec, and the finish hot rolling starting temp. is regulated to 800 to 1100 deg.C. Then, the grain size of primarily recrystallized grains is regulated to 18 to 35mum, and nitriding treatment is executed till the start of secondary recrystallization in final finish annealing after the hot rolling to allow >=0.001% N to absorb into the steel sheet. |
