Method for producing silicon-chromium grain orieted electrical steel

A method for producing a grain oriented electrical steel having superior magnetic properties, comprising the steps of:

• providing a hot processed strip having a thickness of 1.5-4.0 mm, an austenite volume fraction and an isomorphic layer on each surface of the strip,
• the strip consisting essentially of 2.5-4.5% silicon, 0.1-1.2% chromium, no greater than 0.030% carbon, less than 0.005% aluminum, up to 0.1% sulfur, up to 0.14% selenium, 0.01-1% manganese and balance being essentially iron and residual elements,
• the strip having a volume resistivity of at least 45 .mu..OMEGA.-cm and each isomorphic layer having a thickness of 10-40% of the total thickness of the hot processed strip, annealing the strip at a temperature of at least 800.degree. C.,
• the annealed strip having at least 0.010% carbon so that the austenite volume fraction is 2.5-10.0%,
• cold rolling the strip to an intermediate thickness,
• annealing the cold reduced strip wherein a microstructure of the strip consists of fine iron carbide precipitates in a ferrite matrix having less than 1 vol. % of martensite and/or retained austenite,
• cold rolling the annealed strip to a final thickness,
• decarburize annealing the cold reduced strip to sufficiently to prevent magnetic aging,
• coating at least one surface of the annealed strip with an annealing separator, and final annealing the coated strip to effect secondary grain growth and thereby provide a permeability measured at 796 A/m of at least 1780.

A method for producing a grain oriented electrical steel having superior magnetic properties, comprising the steps of:

• providing a strip having a hot processed thickness of 1.7-3.0 mm, an austenite volume fraction and an isomorphic layer on each surface of the strip, the strip consisting essentially of 2,9-3.8% silicon, 0.2-0.7% chromium, no greater than 0.030% carbon, less than 0.005% aluminum, 0.020-0.030% sulfur, 0.015-0.05% selenium, 0.05-0.07% manganese and balance being essentially iron and residual elements,
• annealing the hot processed strip at a temperature of 1000-1125.degree. C. for a time up to 10 minutes,
• the annealed strip having a volume resistivity of at least 50 .mu..OMEGA.-cm, at least 0.010% carbon so that the austenite volume fraction is 4.0-10.0% and the isomorphic layer on each surface having a thickness of 0.17-1.20 mm,
• cold rolling the strip to an intermediate thickness,
• annealing the cold reduced strip at a temperature of at least 800.degree. C. for at least 5 seconds and slowly cooling the strip at a rate of no greater than 10.degree. C. per second to 650.degree. C. and thereafter rapidly cooling at a rate of at least 23.degree. C. per second to about 315.degree. C. whereby a microstructure of the strip consists of fine iron carbide precipitates in a ferrite matrix having less than 1 vol. % of martensite and/or retained austenite,
• cold rolling the annealed strip to a final thickness,
• decarburize annealing the cold reduced strip to less than 0.003% carbon,
• coating at least one surface of the annealed strip with an annealing separator,
• and final annealing the coated strip at a temperature of at least 1100.degree. C. for at least 5 hours to effect secondary grain growth and thereby provide a permeability measured at 796 A/m of at least 1780.