Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1986-09-09
1987-12-15
Sheehan, John P.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
427127, H01F 104
Patent
active
047131233
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
Lately, remarkable developments and efforts for satisfying the improvement of electrical and magnetic properties in grain oriented silicon steels, particularly ultimate demand on reduction of iron loss are gradually producing good results. However, when practically using such grain oriented silicon steel sheets, it is a serious problem that the degradation of the above properties is unavoidably caused when the steel sheet is subjected to a so-called strain relief annealing after its working and assembling and the use application is restricted undesirably. Therefore, this invention develops a new measure for advantageously satisfying the above demands irrespectively of a high temperature heat treatment such as strain relief annealing, and more particularly it relates to a method of producing grain oriented silicon steel sheets which can advantageously attain the improvement of compressive stress dependence of magnetostriction and lamination factor in the grain oriented silicon steel sheet.
BACKGROUND ART
As is well-known, the grain oriented silicon steel sheet, wherein secondary recrystallized grains are highly aligned in (110)[001] orientation, namely Goss orientation, is mainly used as a core for transformer and other electrical machinery and equipment. In this case, it is required that the magnetic flux density (represented by B.sub.10 value) is high, the iron loss (represented by W.sub.17/50 value) is low and, in addition to these properties, the magnetostriction property and lamination factor are excellent.
Since these grain oriented silicon steel sheets are usually manufactured through many complicated steps, a great of inventions and improvements are applied to the above steps, whereby low iron loss grain oriented silicon steel sheets having B.sub.10 of not less than 1.90 T and W.sub.17/50 of not more than 1.05 W/kg when the product thickness is 0.30 mm, or B.sub.10 of not less than 1.89 T and W.sub.17/50 of not more than 0.90 W/kg when the product thickness is 0.23 mm are manufactured up to the present.
Lately, supreme demands on the reduction of power loss become considerable in view of energy-saving. Particularly, a system of "Loss Evaluation" wherein the reduction percentage of iron loss is converted into a money to load on the cost of the transformer in the manufacture of low loss transformer is widely spread in Europe and America.
Under the above circumstances, there has recently been proposed a method wherein local microstrain is introduced into the surface of the grain oriented silicon steel sheet by irradiating a laser beam onto the steel sheet surface in a direction substantially perpendicular to the rolling direction after the finish annealing to thereby conduct refinement of magnetic domains and hence reduce the iron loss (Japanese Patent Application Publication Nos. 57-2252, 57-53419, 58-5968, 58-26405, 58-26406, 58-26407 and 58-36051).
Such a magnetic domain refinement is effective for the grain oriented silicon steel sheet not subjected to the strain relief annealing in the manufacture of stacked lamination-core type transformers. However, in case of wound-core type transformers, the strain relief annealing is necessarily performed after the magnetic domain refinement, so that the local microstrain produced by laser irradiation on purpose is released by the annealing treatment to make the width of magnetic domains wide and consequently the laser irradiating effect is lost.
On the other hand, Japanese Patent Application Publication No. 52-24499 discloses a method of producing an extra-low iron loss grain oriented silicon steel sheet wherein the surface of the grain oriented silicon steel sheet is subjected to a mirror finishing after the final annealing or a metal thin plating is applied to the mirror finished surface or further an insulation coating is baked thereon.
However, the mirror finishing for improving the iron loss does not sufficiently contribute to the reduction of iron loss in comparison with remarkable cost-up of the manufacturing step. Particularly, th
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patent: 3562011 (1971-02-01), Hirst et al.
patent: 3941623 (1976-03-01), Takashina et al.
patent: 4632708 (1986-12-01), Konno et al.
Funahashi Toshihiko
Inokuti Yukio
Ito Yoh
Kawasaki Steel Corporation
Miller Austin R.
Sheehan John P.
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