High energy product can promote the
permanent magnet motor, miniaturized information fields and efficient, technological and industrial development of high energy permanent magnet increasing demand. At present, Nd-Dy-Fe-B permanent magnets are widely used in 150 DEG C temperature. However, when the temperature increases to 200 C. To maintain the performance of permanent magnet, we must greatly enhance the usage of the precious rare earth ang Dy, causing the increase of manufacturing cost. Therefore, the development of excellent temperature stability, high energy and zero product of heavy rare earth permanent magnet has become an important research topic.
Sm2Co17 based permanent magnet with high magnetic energy unique and excellent magnetic stability and excellent oxidation resistance and corrosion resistance, has attracted wide attention. High energy product SmCo maximum magnetic energy can reach 35MGOe and the maximum temperature can reach 500 DEG C and above.Sm2Co17 base sintered permanent magnet, its microstructure a cellular structure, the cell with the long axis along the easy axis of the rhomboid, for the three party crystal system Fe rich Sm2 (Co, Fe) 17 main phase, size between 50 to 200 nm, the cell wall is thin six hexagonal Cu rich Sm (Co, C U) 5 phases with thicknesses of 5 to 20 nm
Permanent magnetic material of the maximum magnetic energy product strength and its theoretical value of saturation magnetization is proportional to the square. To improve the primary condition of permanent magnet magnetic energy product is improving magnetic saturation magnetization. Only high saturation magnetization, can obtain high remanence, resulting in high energy product. And the magnetic energy product is structure sensitive so in the saturation magnetization increase at the same time, need the cellular structure of the magnet optimization.
Through the optimization of composition, with the corresponding heat treatment process to adjust the microstructure of the magnet, the saturation magnetization and magnetic energy product of SmCo magnets can be effectively improve. In the rhombohedral cell structure of the main magnet phase, Fe is the most important factor. Sm2Co17 the most important factor is about 12kGs, with the addition of Fe. Js gradually increased; when Fe increased to Sm2 (Co0.7, Fe0.3) 17 when the ratio of Js to 16.3kGs.. However, when the content of Fe in the magnet is more than 25%, cellular structure will appear abnormal increase of size will exceed 150nm. feet The oversized cell structure is unfavorable to the uniformity of the cellular structure and leads to a sharp deterioration of the coercivity and the squareness of the demagnetization curve.
Recent studies show that through the heat treatment process optimization and additional magnetic heat treatment process can optimize the magnetic performance of permanent magnet. The magnet temperature of solution phase composition can optimize the quenched alloy appropriately, so as to improve the Br of the magnet and the intrinsic coercivity Hcj, optimal solution temperature of 1423K for preparing magnetic magnet for Br=12.22kGs, Hcj=12.7kOe. then the Zr content in the fine magnet magnet Hcj to 18.6kOe. on the other hand, the introduction of pre aging process to uniform distribution of Cu elements in quenched alloy, can refine the cell size from In order to improve the squareness of the magnet, the maximum magnetic energy product of the magnet is increased from 31.5MGOe to 33.4MGOe.. It is reported that the multi stage solid solution process can increase the squareness of the magnet and maximize the magnetic energy product of the magnet to 35.4MGOe.
Iron and Steel Research Institute in China now has production capacity of high performance sintered magnet that has good performance consistency performance of the permanent magnet, the maximum energy product is more than 30MGOe. They developed milling grinding technology using high speed air flow (air is recycled in the pipe, oxygen content control), the results is better than that reported abroad by wet milling technology of the milling process.
