Nippon Steel Corporation

Tadao Nozawa

Tadashi Nakayama

Yoshiyuki Ushigami

Norito Abe

Masaki Tanaka

Yozo Suga

Toshiya Wada

Fumio Matsumoto

Toshihiko Takata

Satohiro Hayami

Takaaki Yamamoto

Masao Yabumoto

Osamu Honjo

Yakichiro Kawamo

Sadami Kousaka

A very thin electrical steel strip having a thickness not exceeding 150 microns, an average grain diameter not exceeding 1.0 mm, a high degree of {110} &lt;001&gt; grain orientation, a high normalized magnetic flux density as expressed by a B.sub.8 /B.sub.s value which is greater than 0.9, and a low core loss not exceeding 50% of the core loss of any conventional product. It is produced from a starting material consisting of a grain-oriented electrical steel strip containing not more than 8% silicon, the balance thereof substantially being iron, and having a high degree of {110} &lt;001&gt; grain orientation, a normalized magnetic flux density as expressed by a B.sub.8 /B.sub.s value which is greater than 0.9, an average grain diameter of at least 20 mm in the rolling direction and an average grain diameter of at least 40 mm in the direction perpendicular to the rolling direction. The material is cold rolled with a reduction of 60 to 80% to a final thickness not exceeding 150 microns, and the cold rolled material is annealed for primary recrystallization. The use of a starting material further containing 0.005 to 0.30% of one or both of tin and antimony yields a product of still improved properties.

Very thin electrical steel strip having low core loss and high magnetic

The present invention provides a wound core having a low core loss and not susceptible to a disappearance of the core loss lowering effect due to a magnetic domain refining even when stress-relief annealing is conducted after fabrication of a steel strip into a wound core, through a process which comprises, fabricating a very thin silicon steel strip comprising by 6.5% weight or less of silicon with the balance consisting essentially of iron and having a sheet thickness of 100 .mu.m or less and a magnetic flux density (B.sub.8 value) of 1.80T or more into a wound core, subjecting the wound core to stress-relief annealing, unwinding the very thin silicon steel strip from the core, introducing into the very thin silicon steel strip a linear or dotted local strain in a direction at an angle of 45.degree. to 90.degree. to the rolling direction of the thin strip, and rewinding the thin strip onto the core.

Process for preparing wound core having low core loss

In conventional processes for producing a grain-oriented electromagnetic steel strip or sheet, the carbon and silicon content of the starting material is such that .alpha.-.gamma. transformation takes place, said transformation formerly being belived to play an important role in, for example, the formation of AlN. Recently, attempts have been made to reduce the carbon content so as to simplify decarburization-annealing, but these attempts have not been successful. In the present invention, (1) an extremely low carbon content (C.ltoreq.0.02%) and an extremely low sulfur content (S.ltoreq.0.015%), as well as a low heating temperature of the starting material, and (2) a temperature gradient of at least 2.degree. C. per centimeter, which is generated parallel to the sheet surface and under which the growth of secondary recrystallized grains is completed, are combined. As a result of such combination, the following advantages are attained: (1) secondary recrystallization is attained without .alpha.-.gamma. transformation taking place; (2) a high magnetic flux density is attained; (3) a continuous-casting machine can be directly combined with a continuous hot-rolling mill; (4) decarburization-annealing can be simplified; and (5) no molten slag is formed during heating of a steel slab.

Process for producing a grain-oriented electromagnetic steel sheet or

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

A method for producing a grain-oriented electrical steel sheet showing super low watt loss, comprising making a silicon steel ingot containing 2.5 to 4.0% of Si, subjecting the ingot treatments including hot rolling, annealing and at least one cold rolling to obtain a final size, subjecting the steel to decarburization annealing and a finishing annealing which completes secondary recrystallization, subjecting the steel to remove surface product and then subjecting the steel to chemical polishing or electrolytic polishing to polish the steel surface to mirror condition.

Method for producing a super low watt loss grain oriented electrical

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Kitakyushu, Japan

Tadao Nozawa