| 摘要 |
PROBLEM TO BE SOLVED: To increase a saturation magnetic flux density and to reduce high-frequency iron loss by imparting an Si concn. gradient to a steel sheet in its steel sheet direction, making the Si concn. of the surface layer thereof higher than the Si concn. in the central part and setting the average Si concn. of the overall thickness of the steel sheet to a specific value or below. SOLUTION: The average Si concn. of the overall thickness of the steel sheet is specified to <=3.5 wt.%. The Si concn. of the surface layer of the steel sheet is preferably >=4 wt.%, more particularly 6.5 wt.%. Further, the depth ratio of the portion of >=4 wt.% in the Si concn. of the surface layer is preferably >=10%. The method of forming the high Si concn. portion of the surface layer of the steel sheet may be CVD, PVD and any of other methods. The effect of obtaining the low high-frequency iron loss while maintaining the high saturation magnetic flux density does not depend on the thickness of the steel sheet but is particularly effective to the steel sheet having a thickness of >=0.2 mm. While the thickness distribution of Si is preferably symmetrical with a vertical plane in terms of a steel sheet shape, the effect may be obtd. even if the distribution is asymmetrical. The silicon steel sheet adequate for iron cores of transformers, reactors, motors, etc., is obtd. |
