| 摘要 |
PROBLEM TO BE SOLVED: To stably obtain excellent magnetic properties without generating deterioration in magnetic properties after stress relieving annealing by subjecting a steel slab having a specified compsn. to finish hot rolling and thereafter executing annealing treatment under specified conditions till the start of final cold rolling. SOLUTION: A steel slab has a compsn. contg. C, Si, Mn, Al and rare earth metals, and the following impurity elements are suppressed to the allowable ranges: Ti: 0.0015 to 0.0070 wt.%, S: <=50 ppm, O: <=40 ppm and N: <=60 ppm. This slab is subjected to hot rolling, is then subjected to cold rolling and is subjected to finish annealing to form into a product. At this time, it is important that annealing in which it is heated in the temp. range of 700 to 900 deg.C for 30 min to 10 hr at least for one time between after finish hot rolling and before final cold rolling and is subsequently cooled at a cooling rate of <=50 deg.C/min at least to 500 deg.C is executed. In this way, the steel structure in which the grain size before the stress relieving annealing is <=35 μm, and the grain size after the stress relieving annealing at 750 deg.C for 2 hr is >=65 μm is formed. |
