Non-oriented electrical steel sheet and method of manufacturing the same excellent magnetic properties after stress relief annealing

摘要

PROBLEM TO BE SOLVED: To stably obtain excellent magnetic properties in which the dispersion of characteristics does not occur after stress relieving annealing even in the case harmful Ti intrudes into a steel by allowing Ti as impurities to intrude in a specified range into a steel having a specified compsn. large in the content of Al, suppressing the intrusion of S, O and N to specified value or below and specifying the grain sizes before and after stress relieving annealing under specified conditions. ;SOLUTION: A steel slab having a compsn. contg., by weight, ≤0.005% C, 0.1 to 3.5% Si, 0.1 to 1.5% Mn and 0.6 to 2.0% Al, in which the intrusion of 0.0015 to 0.0050% Ti is allowed, the content of S is suppressed to ≤40 ppm, O to ≤30 ppm and N to ≤50 ppm, and the balance Fe is subjected to hot rolling and is thereafter subjected to finish annealing. At this time, in the meantime before final cold rolling and after the finish hot rolling, annealing treatment in which it is heated at 700 to 900°C for 30 min to 10 hr and is cooled at a cooling rate at least to 500°C by 50°C/min is executed for one or more times to form its structure into the one in which the grain size before stress relieving annealing is regulated to ≤35 μm and the grain size after stress relieving annealing at 750°C for 2 hr is regulated to ≥65 μ.;COPYRIGHT: (C)1999,JPO