Development of Anisotropic Misch-Metal-Fe-B Melt-Spun Magnets and its Application to Plastic Magnets

人们认识到，开发杂金属在电气材料中的应用领域对有效利用自然资源具有重要意义。研制了能积大于8MGOe的MM-Fe-B各向同性熔体自旋磁体。它的性价比（以每能量产品的成本来衡量）与Ba铁氧体磁铁相当。在本研究项目中，致力于开发高性价比永磁体的c轴定向技术。(1)在熔体淬火工艺的各种参数中，熔体喷射到转轮上时的温度是影响R2Fe14B四方化合物c轴取向的最重要因素。当温度保持在高于熔点200℃时，自由表面和车轮表面的c轴取向在3℃范围内基本保持完美。(2)取向层厚度自由面为15 μ m，车轮面为5 μ m。中间层具有少取向结构。(3) Ta、Zr等第四元素的加入改善了c轴取向。前者和前者分别对自由面和轮面取向有效。(4)伴随c轴取向，晶粒尺寸趋于粗化。为了获得高矫顽力，必须控制晶界处的材料析出。

It has been recognized that development of application field of misch metal (MM) to electrical materials is of great importance with respect to effective consumption of natural resources. We developed the MM-Fe-B isotropic melt-spun magnets with the energy product more than 8MGOe. Its cost-performance (measured with cost per energy product) is comparable to that of Ba ferrite magnets. In this research program, effort was made to develop the c-axis orientation technique for higher cost-performance permanent magnets.(1) Among various parameters of melt-quenching technique, the temperature of the melt when ejected onto the rotating wheel is the most important one affecting the c-axis orientation of the R2Fe14B tetragonal compounds. When the temperature is kept 200 degree higher than the melting point, mostly perfect c-axis orientation within 3 degree dispersion was available on both the free and wheel surfaces.(2) The thickness of orientated layer is 15 mu m on the free surface and 5 mu m on the wheel surface. The intermediate layer has the less oriented structure.(3) Addition of fourth elements such as Ta and Zr improve the c-axis orientation. The former and former elements are effective on the orientation at free and wheel surfaces, respectively.(4) Accompanied by the c-axis orientation, grain size tends to be coarse. To obtain the high coercivity, control of the materials precipitaing at the grain boundary seems necessary.