Grain oriented electrical steel sheet having high magnetic flux density and ultra low iron loss and process for production the same

A process for producing a grain oriented electrical steel sheet having a high magnetic flux density and an excellent iron loss property, said process comprising the steps of:

• heating a slab comprising, in terms of % by weight, 0.021 to 0.075% of C, 2.5 to 4.5% of Si, 0.010 to 0.040% of acid soluble Al, 0.0030 to 0.0130% of N, 0.0140% or less of S, 0.05 to 0.45% of Mn, and 0.03% or more of P with the balance consisting of Fe and unavoidable impurities at a temperature below 1,280.degree. C., hot-rolling the heated slab and optionally subjecting the hot-rolled sheet to annealing, subjecting the steel sheet to once or twice or more cold rolling with annealing between the cold rollings being effected to provide a steel sheet having a final thickness, subjecting the cold-rolled sheet to decarburization annealing, nitriding the steel sheet after decarburization annealing, coating the nitrided steel sheet with an annealing separator, subjecting the coated steel sheet to final box annealing in an atmosphere containing 30% or more nitrogen during temperature raising portion of the final annealing, and coating the annealed steel sheet with an insulating film, wherein said annealing separator comprises MgO and at least a Cl compound in an amount of 1 part by weight or more in terms of Cl based on 100 parts by weight of MgO.