Method for preparing rare-earth permanent magnets by infiltration process and graphite box utilized in method

Abstract

Disclosed are a method for preparing rare-earth permanent magnets by the infiltration process and a graphite box utilized in the method. The method includes: preparing base materials of R (rare earth)-Fe (ferrum)-B (boron) rear earth magnets by prepared raw materials which are subjected to smelting, hydrogen decrepitation, magnetic field forming, sintering and the like; cutting the base material into slices with the thickness ranging from 2mm to 10mm; placing the slices into a specially-made graphite box and placing heavy rare earth type metal fluoride and a few of metal calcium particles into the bottom of the graphite box; sintering the graphite box in a sintering furnace, inflating air into the sintering furnace to cool the temperature to be lower than 60 DEG C, finally ageing magnets, then inflating Ar gas into the sintering furnace to cool the temperature to be lower than 60 DEG C after ageing, and finally obtaining the rare-earth permanent magnets. Elements including Dy (dysprosium), Tb (terbium), Ho (holmium) and the like are infiltrated into the crystal boundary of the R-Fe-B to prepare high-coercivity rare-earth permanent magnets by means of infiltration process, usage of heavy rare earth metal can be greatly reduced, and production cost of magnets can be effectively reduced. Additionally, the method for preparing rare-earth permanent magnets by the infiltration process is simple in operation and suitable for batch production.

Description

technical field [0001] The invention relates to a method for preparing a rare earth permanent magnet by an infiltration method and a graphite box used in the method, belonging to the technical field of magnetic materials. Background technique [0002] Take Nd 2 Fe 14 R-Fe-B rare earth sintered magnets with B-type compounds as the main phase are widely used in many fields such as electronics, automobiles, computers, energy, machinery, and medical equipment. When sintered magnets are used in various devices such as motors, the magnets are required to have good heat resistance and high coercive force characteristics in order to adapt to the use conditions at high temperatures. At present, the coercive force of the magnet is mainly increased by adding heavy rare earth metals Dy, Tb, Ho or their compounds in the smelting process to replace Nd in the main phase. During the process, the heavy rare earth elements cannot be evenly distributed in the grain boundary phase of the mag...

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Problems solved by technology

However, in the actual sintering process, the diffusion rate of heavy rare earth elements RH increases, and these elements will diffuse to the center of the grain, destroying the ideal structure and causing a decrease in the coercive force of the magnet.

[0003] On the other hand, considering the difficulty in processing micro-miniature magnets, it is difficult to replace Nd with other magnets. 2 Fe 14 R-Fe-B Rare Earth Sintered Magnet with Type B Compound as Main Phase

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