Nippon Steel Corporation

Fumio Matsumoto

Tadashi Nakayama

Kunihide Takashima

Yozo Suga

Hiromi Matsumoto

Tsutomu Haratani

Satohiro Hayami

Katuro Kuroki

Munetsugu Matsuo

Toshio Kikuma

Jirou Harase

Tadao Nozawa

Toshihiko Takata

Hiromichi Yasumoto

Takaaki Yamamoto

Kiyoshi Ueno

Hisanobu Nakayama

Yasuhiro Shinkai

Kensuke Mori

Shouzou Oota

Kuniyasu Honda

The present invention relates to a method for producing a grain-oriented electrical steel sheet. A feature of the present invention is to set S.ltoreq.0.007%, Mn=0.08.about.0.45%, P=0.015.about.0.45% in a slab. The present inventive idea does away with the conventional concept of using MnS as an inhibitor. The present invention present incomplete secondary recrystallization by the S content, which is decreased to a level as low as possible. In addition, a product having a high magnetic flux density can be successfully produced by adding appropriate amounts of Mn and P. Due to these advantages a high Si content of a slab, which leads to a watt loss reduction, can also be employed in the present invention. Furthermore, the watt loss of a product produced by a low-temperature slob-heating is considerably lower than a product produced by a high-temperature slab-heating.

Method for producing a grain-oriented electrical steel sheet having a

Conventionally, the silicon content of a grain-oriented electrical steel is approximately 3% at the maximum, since cold-rolling is difficult if the silicon content is high. Although conventional warm-rolling can occasionally mitigate the poor workability of a silicon steel having a high silicon content, it is impossible to control the texture of a cold-rolled strip and to completely prevent brittleness. The present invention provides a novel rolling method in which, due to the heating of a steel strip prior to the carrying out of cold-rolling, a desirable texture can be formed and rupture of the cold-rolled strip can be prevented. The strip is heated to within a temperature range, in which both the minimum temperature which is at least 200.degree. C. and at least equal to T.sub.L (.degree.C.)=(x-3.0).sup.2 .times.100, x being the silicon content in weight percent, and the maximum temperature which temperature range being is not more than 400.degree. C. and not more than T.sub.H (.degree.C.)=-200.times.log (1/y), y being the strain rate (second.sup.-1) during the cold rolling are determined so as to satisfy the temperature of the first cold rolling pass.

Process for producing a grain-oriented electrical steel sheet

The present invention relates to a process for producing a grain-oriented silicon steel sheet or strip, wherein the crystals of the steel sheet or strip have an orientation of {110}&lt;001&gt; and, further, the steel is easily magnetized in the rolling direction. Since the slab-heating temperature for a grain-oriented silicon steel is considerably higher than that for low carbon steel grades, coarsening of the crystal grains is likely to occur during heating, and the coarse crystal grains are elongated during hot-rolling in the rolling direction and remain in the hot-rolled steel sheet as portions of the grain-oriented silicon steel strip or sheet, where secondary recrystallization becomes incomplete, or as so-called streaks. It is an object of the present invention to provide a novel hot-rolling technique capable of preventing the generation of streaks and capable of enhancing the magnetic flux density of the final product in terms of the B.sub.8 value even in a case where the tendency of streaks to form is small. The present invention is characterized in that during hot-rolling a silicon steel slap is subjected to at least one pass in which the axial lines of the top working roll and the bottom working roll are non parallel, and as a result of these working rolls being non parallel, the grain-oriented electromagnetic steel sheet or strip has no streaks and has a high magnetic flux density.

Process for producing a grain-oriented silicon steel sheet or strip

In the secondary recrystallization of a grain-oriented silicon steel sheet, a specific temperature gradient is generated, thereby developing the secondary recrystallized grains having a good (110) [001] orientation and increasing the magnetic flux density higher than that previousy obtained. The temperature gradient is established at the boundary region between the primary and secondary recrystallized regions, with the result that highly oriented (110) [001] secondary recrystallization nuclei preferentially are caused to develop.

Process for producing grain-oriented electromagnetic steel sheet

In a process for the production of a grain-oriented electromagnetic steel strip, a slab is heated, hot-rolled, cold-rolled, and subjected to a decarburization annealing and secondary recrystallization annealing steps. Grain coarsening is likely to occur during the high temperature heating and remain in the final product as streaks. The secondary recrystallization is, therefore, incomplete due to the streaks. In order to remove this disadvantage, the work piece is subjected to at least two rolling passes, wherein the high circumferential speed roll of one pair of the rolls and the low circumferential speed roll of another pair of the rolls are arranged on the same side of the work piece.

Process for producing grain-oriented electromagnetic steel strip

In a process for the production of a grain-oriented silicon steel strip, a slab is heated, hot-rolled, cold-rolled, and subjected to a decarburization annealing and secondary recrystallization annealing steps. Grain coarsening is likely to occur during the high temperature heating and remain in the final product as streaks. The secondary recrystallization is, therefore, incomplete due to the streaks. In the hot rolling, an asymmetric flow, is applied to the steel, so as to eliminate the streaks and, hence, to obtain excellent magnetic properties.

Process for producing grain-oriented silicon steel strip

Process for producing a grain-oriented silicon steel sheet from silicon steel slabs, particularly from continuously cast steel slabs, comprising at least one recrystallization rolling at high reduction rate in a temperature range from 1190.degree. C. to 960.degree. C. in the hot rolling step. The process of the present invention is very effective in preventing the streaks of smaller, poorly oriented grains very often seen in the final product produced from silicon steel slabs.

Process for producing a grain-oriented silicon steel sheet

A method for producing high magnetic flux density grain oriented electrical steel sheets or strips having a B.sub.8 characteristic in the rolling direction of not less than 1.9 Wb/m.sup.2 by hot rolling, continuous annealing for precipitation of the AlN, cold rolling into the final thickness, decarburization annealing, and finishing annealing. The cold rolling includes a final rolling at a strong reduction between 81 and 95%.

Method for producing high magnetic flux density grain-oriented

A cold rolling method for producing a high magnetic flux density grain oriented electrical steel sheet or strip having remarkably excellent B.sub.8 characteristics, comprising subjecting a hot rolled steel sheet or strip a combination of heavy cold rolling with annealing during which the steel sheet or strip is held at a temperature between 100.degree. and 350.degree.C at an interim sheet thickness stage during the heavy cold rolling.

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Kitakyushu, Japan

Fumio Matsumoto