異方性MK磁石の研究(I)

Abstract

The MK permanent magnet Fe-Ni-Al ternary aloy was invented by Tokushichi Mishima (one of authors) in 1930. Since then the magnetic properties of this alloy underwent no mprovement to a remarkable degree for sometime. During the 2nd World War, it was disgovered that MK magnet containing the certain restricted range of comnosition could attain to excellent magnetic properties by the heat-treatment in magnetic field.In our country, the investigation of the magnetic treatment of MK magnet was kept on for a long time in Mishima's laboratory in University of Tokyo. In this report, the results of such investigation on the effects of chemical composition and additional elements on the magnetic properties of this anisotropic Mk magnet alloy will be described. The experimental results on the heat-treatment and industrial aspects mav be reported later. Briefly this report may be summarized as follows:According to the increase of Ni content up to 17%, the coercive force is improved, but the residual induction be omes inferior. Increase of Co content up to 28% is preferable for the residual induction, but its content is relative to Ni content and it is desirable to restrict the total content of Ni and Co to 38 or 39%. The magnetic properties is sensitive to Al content. The optimum composition is 7.8-8.4% and unfavourable effects become marked when Al contents reach to less than 7%. The optimum chemical composition of Al needs to be changed according to the additional Si and Ti contents. C content has to be kept under 0.05%, because it is apt to cause a remarkable deterioration of the magnetic properties. Addition of Ti is effective in overcoming its undesirable effects. As Si, Mn and P ill-effect on the magnetic properties, it is advisable that Si, Mn and P contents should be kept respectively lower than 0.2%, 0.3% and 0.02%. Addition of Cb and Zr is favourable to the magnetic properties, especially Cb is effective to improve the coercive force. The effects of other additional elements: B, Cr, W, Mo, V, Be and Sn, is unpreferable to the magnetic properties.