Production method of grain oriented electrical steel sheet having excellent magnetic characteristics

A production method of a grain oriented electrical steel sheet having excellent magnetic properties, involving the steps of heating a slab containing not greater than 0.075% of C, 2.2 to 4.5% of Si, 0.010 to 0.060% of acid-soluble Al, not greater than 0.0130% of N, not greater than 0.014% of (S+0.405 Se), 0.05 to 0.8% of Mn in terms of weight percent and the balance consisting of Fe and unavoidable impurities, at a temperature less than 1,280.degree. C., hot rolling the slab to provide a hot rolled sheet, subsequently effecting final cold rolling, at a high reduction at a reduction ratio of at least 80%, without annealing the hot rolled sheet, then effecting decarbonization annealing and applying final finish annealing to obtain a grain oriented electrical steel sheet, said method characterized in that total N in weight percent and N as AlN satisfy relationships

• N-N as AlN.ltoreq.0.0030%
• and
• (N as AlN)/N.ltoreq.0.55,
• the mean grain size of the primary recrystallization grains at the stage from completion of decarbonization annealing to the start of final finish annealing is 18 to 35 .mu.m, and nitriding treatment is carried out after completion of hot rolling until the start of secondary recrystallization of final finish annealing so as to let the steel sheet absorb nitrogen in an amount of at least 0.0010 wt %.