Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1986-09-05
1988-09-13
Sheehan, John P.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148112, 148120, 148121, H01F 102
Patent
active
047707208
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for producing a grain-oriented electrical steel sheet having a low watt-loss, wherein the magnetic characteristics are not impaired even by stress-relief annealing.
BACKGROUND ART
In recent years, from a viewpoint of saving energy, it has been desired to reduce watt-loss in electrical steel sheets. As a method for reducing the watt-loss, a subdivision of magnetic domains by laser irradiation has already been disclosed in Japanese examined Patent Publication (Kokoku) No. 58-26405. The reduction of watt-loss by this method is due to strains introduced by laser irradiation. Therefore, the method can be applied to a laminated-core type transformer wherein no stress-relief annealing is necessary, but cannot be applied to a wound-core type transformer wherein stress-relief annealing is necessary. Also, Japanese Unexamined Patent Publication (Kokai) No. 59-100222 discloses a method wherein a steel sheet subjected to secondary recrystallization annealing is locally heat-treated and annealed at a temperature of 800.degree. C. or higher, whereby grain boundaries are artificially introduced. In this method, the reduction of watt-loss value is achieved by the subdivision of magnetic domains by the artificial grain boundaries introduced into the steel sheet. The watt-loss reduction effect does not disappear even upon stress-relief annealing, because the steel sheet is annealed at a temperature of 800.degree. C. or higher. However, the disclosed examples indicate it is difficult to obtain a watt-loss comparable with that in the above-mentioned method for reducing the watt-loss value by laser irradiation.
DISCLOSURE OF THE INVENTION
The present invention provides a grain-oriented electrical steel sheet having a low watt-loss wherein the magnetic characteristics are not impaired even upon stress-relief annealing, through simultaneously resolving the difficulties arising because, when stress-relief annealed, the reduction of watt-loss cannot be achieved because the introduced strains disappear and because, even though the watt-loss reduction effect does not disappear upon stress-relief annealing, a watt-loss value comparable with that of the laser irradiation method cannot be obtained.
In the present invention, in order to solve the above-mentioned difficulties, a steel sheet subjected to final-texture annealing or insulation coating application is given a work strain in the form of a dotted or broken line with a gear type roll, for example, at a mean load of 90 to 220 kg/mm.sup.2, and then annealed at a temperature of 750.degree. C. or higher so that fine recrystallized grains are formed within the crystal grains to cause a subdivision of the magnetic domains. Thus, the present invention provides a grain-oriented electrical steel sheet having an excellent watt-loss value comparable with or lower than that of the laser irradiation method even when subjected to stress-relief annealing.
The present invention will be described in detail below.
A slab containing Si up to 4% is heated and hot-rolled to an intermediate thickness. The hot-rolled steel sheet is subjected to pickling, heat-treated in accordance with a need therefor at this stage, and then cold-rolled twice with an intermediate annealing or once to a final sheet thickness. The cold-rolled steel sheet is subjected to a usual process whereby the grain-oriented electrical steel sheet is produced, which consists of the steps of decarburization annealing, annealing-separator application, and secondary recrystallization annealing. The steel sheet may be then applied with a coating liquid for forming a phosphoric-acid tension-imparting coating or other insulation coatings, and baked. The thus obtained steel sheet is given a working at a load of 90 to 220 kg/mm.sup.2 in terms of the mean load at the stress-applied sites (the quotient of the applied stress divided by the stress-imparted area on the steel sheet viewed normally to the sheet surface--the stress-imparted area on the sheet surface after stress impar
REFERENCES:
patent: 3647575 (1972-03-01), Fiedler et al.
patent: 3990923 (1976-11-01), Takashina et al.
patent: 4203784 (1980-05-01), Kuroki et al.
patent: 4318758 (1982-03-01), Kuroki et al.
patent: 4533409 (1985-08-01), Benford
patent: 4548656 (1985-10-01), Kimoto et al.
patent: 4554029 (1985-11-01), Schoen et al.
Eto Katsuo
Kobayashi Hisashi
Nishimura Takeo
Sasaki Eiji
Nippon Steel Corporation
Sheehan John P.
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