Grain oriented electromagnetic steel sheet and manufacturing thereof

A method of making a grain oriented electromagnetic steel sheet from a silicon steel slab containing from about 0.03 to 0.10 wt % carbon, from about 2.0 to 5.0 wt % silicon, from about 0.04 to 0.15 wt % manganese, from about 0.01 to 0.03 wt % of either or both of sulfur and selenium, from about 0.015 to 0.035 wt % soluble aluminum and from about 0.0050 to 0.010 wt % nitrogen and wherein said slab contains from about 0.001 to 0.07 wt % bismuth comprising:

• heating said slab to a temperature of at least about 1,300° C., hot-rolling the heated steel slab, then achieving a final sheet thickness through a combination of annealing and cold rolling, decarburization-annealing the sheet of the final thickness, and conducting final finishing annealing to the decarburization-annealed sheet;
• controlling the average cooling rate to about 30 to about 1200° C./sec for a period of five seconds measured from immediately after the end of hot rolling;
• and soaking during at least a portion of the decarburization annealing while establishing a PH2O/PH2 ratio in the atmosphere to about 0.45 to about 0.70.