| 摘要 |
PURPOSE:To omit hot rolled plate annealing and to stably obtain superior magnetic properties by limiting the amount of solid-solution N in a slab at the completion of slab heating and controlling the average grain size of primary recrystallized grains before the initiation of final finish annealing. CONSTITUTION:A slab of a steel having a composition consisting of, by weight ratio, 0.021-0.075% C, 2.5-4.5% Sr, 0.010-0.060% acid-soluble Al, <=0.0150 N, <=0.014% of (S+0.405Se), 0.05-0.8% Mn, and the balance Fe with inevitable impurities, is heated up to <1280 deg.C and hot-rolled. The amount of solid-solution N in the slab at the completion of slab heating is regulated to <=0.0045wt.%. Final cold rolling is done at 80% draft. Subsequently, decarburizing annealing is done and the average grain size of primary recrystallized grains before the initiation of final finish annealing is regulated to 18-30mum. Then, final finish annealing is performed. In the course between the completion of hot rolling and the initiation of secondary recrystallization at final finish annealing, nitriding treatment is applied to the steel sheet. Further, it is preferable to regulate the cumulative draft of final three passes at hot rolling to >=40%. |
