Ultrahigh silicon, grain-oriented electrical steel sheet and process for producing the same

Abstract

An ultrahigh silicon, grain-oriented electrical steel sheet having a magnetic flux density, B.sub.8, of 1.57 or more and a degree of azimuth orientation, R (B.sub.8 /B.sub.s) of 0.87 or more is provided by cold-rolling an ultrahigh silicon steel sheet comprising by weight 0.005 to 0.023% of C, 5 to 7.1% of Si, 0.014% or less of S, 0.013 to 0.055% of acid soluble Al and 0.0095% or less of total N with the balance consisting of Fe and unavoidable impurities at a temperature in the range of from 120.degree. to 380.degree. C. optionally after annealing at a temperature in the range of from 800.degree. to 1100.degree. C., subjecting the cold-rolled sheet to decarburization annealing, coating the annealed sheet with an annealing separator, coiling the coated sheet to prepare a strip coil and subjecting the strip coil to high-temperature finish annealing for secondary recrystallization, the steel sheet being subjected to nitriding during a period from the decarburization annealing to the initiation of secondary recrystallization in the step of high-temperature finish annealing, to increase the nitrogen content.

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