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The influence of the preparation process of sintered ndfeb magnet coercive force

by:Newland     2020-05-04
1, the influence of melting process in the process of smelting, should as soon as possible to raw material melt, such not only can reduce the Nd, Dy, such as low melting point of rare earth elements volatilize, also can reduce the alpha The emergence of Fe, improve the relative content of alloy main phase, thus can improve the magnetism of permanent magnet in the end. High coercive force of sintered ndfeb magnets generally higher, the content of rare earth in ingot in alpha Fe is less than high remanence magnet ingot casting, but also cannot be ignored. The researchers in order to reduce the alpha Fe, generally used the SC process and sheet ingot casting process, speed up the cooling of the ingot casting, reduced the alpha The emergence of Fe, coercive force have been improved greatly. Han Jin studies have indicated that the content of neodymium for 33. 5 wt % of the production of thin-plate improve ndfeb magnet coercive force of 824 ka m. - 1, with the production of conventional magnet coercive force is only 780 ka m. - 1. 2, the influence of the pulverizing process grain fine uniform is one of the important conditions of desired coercive force, from the point of view of powder metallurgy, to get fine grain, the original powder material particle size must be small. In powder, in order to get uniform, fine, pure alloy powder, avoid the powder into oxygen and water vapor. In the production of sintered ndfeb magnet powder is very thin, very easy to react with the oxygen in the air and neodymium generated neodymium oxide, thus greatly reduce the performance of the magnets. Powder mainly two aspects in the air. On the one hand is the oxidation of powder process, this process is not reversible. Another is the adsorption process, and it is reversible, closely associated with the humidity in the air, relatively speaking, desorption process is much longer than the adsorption process. Powder happened both in the air, the coercive force will be greatly reduced, therefore should take the strict protection measures. 3, the influence of the molding process of sintered ndfeb magnet intrinsic coercive force along with the forming of orientation degree increase. Orientation of magnet and unoriented magnet coercive force difference is very big. However, after orientation forming magnet remanence than no orientation more than half of the high remanence of magnets, magnetic energy product is more high. This is because there is no orientation molding magnets is isotropic, low remanence, square degree of test curve is also low, the serious influence of the magnet magnetic energy product. To weigh the powder molding process, to avoid oxidation of powder, or try to shorten the process time on environment of protective gas. If the relative content of oxygen rise, will bring down the relative content of rare earth, and the relative content of main and rich Nd phase can also be reduced, and rich Nd phase coated main phase dispersion distribution, can greatly improve the coercive force, and thus reduce two phase can lead to low coercive force. 4, sintering, tempering process in the production of sintered ndfeb magnet, the influence of sintering process is critical. To obtain a higher intrinsic coercive force, lower sintering temperature, sintering time. Under the low temperature, long time of sintering process, the grain size of magnets can control below 15 microns, and there will be more fine grained under 10 microns, ensure the coercive force is big enough. At the same time, the homogenization of subsequent tempering process for liquid phase played a very good stable effect. Tempering of magnetic can impact is bigger also.
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