Patent ID: 7198682

Claim:
A process for the production of grain oriented electrical steel by direct casting in the form of a strip 1.5–5 mm thick a molten steel comprising 2.5–3.5 wt % Si, up to 1000 ppm C, and elements apt to obtain a fine precipitation of second phases of sulphides/selenides and/or nitrides as grain growth inhibitors, the remaining being iron and other elements not essential for the final quality of the product, said steel being subjected to the following process steps in sequence: direct casting in the form of a strip, so that the total oxygen content of the cast steel, once removed the surface scale, is less than 30 ppm; continuous hot rolling of the strip outcoming from the casting machine while it cools down, at a rolling starting temperature comprised between 1000 and 1250° C., with a reduction ratio of between 15 and 50%; coiling the hot rolled strip at a temperature less than a given T max temperature, function of the chosen inhibitors; possible annealing of the hot rolled strip, cold rolling of said strip, possibly in double stage with an intermediate annealing, with a reduction ratio in the last stage of between 50 and 93%, decarburisation annealing, possibly nitriding, coating the decarburised strip with an MgO based annealing separator, and annealing for secondary recrystallisation; coating with an insulating and possibly tensioning coating.