Nippon Steel Corporation

Koichi Fujiwara

Kazutaka Higashine

Yoneo Yamada

Tomohiko Sakai

In the production of a grain-oriented electromagnetic steel strip or sheet having a low watt loss, a silicon steel slab containing not more than 0.085% by weight of carbon, from 2.0% to 4.0% by weight of silicon, from 0.030% to 0.090% by weight of manganese, and from 0.010% to 0.060% by weight of sulfur is conventionally hot-rolled, cold-rolled, and final-annealed. However, this production process involves some problems in regard to the uniformity of the magnetic properties along the full length of the coiled strip. According to the present invention, a silicon steel slab additionally contains from 0.02% to 0.2% by weight of copper, the exit temperature during the finishing-hot-rolling step is controlled in such a manner that the temperature of the top portion of the hot-rolled strip is in the range of from 900.degree. C. to 1050.degree. C. and the temperature of the middle and bottom portions thereof is in the range of from 950.degree. C. and 1150.degree. C., and final cold-rolling is carried out at a reduction ratio of from 50% to 80%, with the result that the final product has good and very uniform magnetic properties over the full length thereof.

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Himeji, Japan

Koichi Fujiwara