Grain-oriented electrical steel sheet having excellent magnetic characteristics, its mfg. method and its mfg. device

Abstract

This invention provides a grain-oriented electric steel sheet whose 180 DEG magnetic wall interval is reduced by the irradiation of a pulse laser beam to improve its magnetic characteristics. A grain-oriented electric steel sheet which is characterized in that the width in the rolling direction of a periodical enclosure domain is not larger than 150 mu m, its depth in the plate thickness direction is not less than 30 mu m, the product of the length in the width direction and the length in the depth direction is not less than 4500 mu m<2> and, in addition, its magnetostriction ( lambda 19 p-p compression) is not larger than 0.9 x 10<-6> when the plate thickness is 0.23 mm and not larger than 1.3 x 10<-6> when the plate thickness is 0.27 mm. A pulse oscillation Q switch CO2 laser beam whose beam shape is elliptical with a long axis in the direction of the sheet width is irradiated to the surface of the grain-oriented electric steel sheet. At that time, the irradiation power density of the single laser pulse is so predetermined as to be lower than the film damaging threshold of the steel sheet surface in order to suppress the formation of a laser irradiation mark. Further, the long axis length of the elliptical beam is so predetermined as to be larger than a pulse beam irradiation interval in the sheet width direction in order to superpose the pulse beams upon each other to provide a sufficient integrated irradiation energy. Moreover, lenses, mirrors, etc by which a laser beam is condensed are provided in the sheet width direction and in the rolling direction independently, distances between the respective beam condensing components and the irradiated steel sheet surface are independently adjusted, and the sheet width direction diameter and the rolling direction diameter of the irradiated laser beam can be arbitrarily adjusted.

Description

technical field [0001] The invention relates to a grain-oriented electrical steel thin plate with improved magnetic properties through laser beam irradiation, in particular to a grain-oriented electrical steel thin plate with high magnetic properties without irradiation damage on the surface of the steel plate and its production process and equipment. Background technique [0002] In the traditional process of producing grain-oriented electrical steel sheets, many methods have been proposed to perform dynamic deformation on the surface of the steel sheet to generate periodic closed magnetic domains for the fragmentation of 180° magnetic domains to reduce iron loss. In these processes, such as disclosed in Japanese Patent Publication No. 55-18566, a focused pulsed YAG laser beam is irradiated on the surface of the steel plate to cause deformation through the evaporation resistance of the film on the surface of the steel plate. These processes have greatly reduced iron loss and...

AI Technical Summary

Problems solved by technology

So the prior art is limited in reducing the laser beam damage due to small fluctuations in the resistance of the steel plate to the laser, which leads to practical problems in the production steps of the continuous processing of different steel plates

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