Preparation method of low-boron low-heavy-rare-earth high-coercivity sintered neodymium-iron-boron permanent magnet

Abstract

The invention provides a preparation method of a low-boron low-heavy-rare-earth high-coercivity sintered neodymium-iron-boron permanent magnet, which comprises the following steps: (1) preparing a main-phase alloy (Nd, R) a- (Fe, M) b-Bc, wherein c is less than 0.9%, a quick-setting sheet is made by adopting a quick-setting sheet process, and then is ground and crushed into powder of 1.5-3.5 mu m;(2) preparing an additive phase [Nd, R, RH2 (CO3) 3] d -(Fe, M) e, wherein preparing the additive phase [Nd, R, RH2 (CO3) 3] d -(Fe, M) e into a quick-setting sheet by adopting a quick-setting sheetprocess, and then grinding and crushing the quick-setting sheet into powder of 0.06-0.3 mu m; (3) adding the additive phase powder into the main phase alloy powder according to the adding proportion of 0.1-2.0% of the total powder, and uniformly mixing under the protection of argon; (4) conducting orientation and compression molding in a magnetic field, and then conducting isostatic cool pressing;(5) performing high-vacuum low-temperature orientation presintering to obtain a green body; (6) soaking the green body into slurry prepared from heavy rare earth carbonate nano powder; and (7) pressurizing and sintering at low temperature. The magnet prepared by the method is low in boron and heavy rare earth content, and has high coercive force HcJ/HcB on the premise of ensuring that magnetic properties such as residual magnetism Br and maximum magnetic energy product (BH) max of the magnet are not reduced.

Description

technical field [0001] The invention discloses a method for preparing a low-boron, low-heavy rare earth and high coercive force sintered NdFeB permanent magnet, which belongs to the technical field of rare earth permanent magnet materials. Background technique [0002] Sintered NdFeB permanent magnet material is a kind of permanent magnet material with excellent comprehensive magnetic properties, which has been widely used in the fields of electronics, electric machinery, medical equipment, packaging, hardware machinery, computers, new energy and aerospace. The normal operating temperature of sintered NdFeB magnets is ±40-80°C, and the temperature, time, electromagnetic field, machinery (vibration and shock), radiation, and chemical effects in the workplace will affect its performance, especially in aerospace, marine, etc. Used in harsh environments such as engineering, chemical engineering, and new energy vehicle drive motors, its performance attenuation is very serious and...

AI Technical Summary

Problems solved by technology

However, adding heavy rare earth elements such as terbium and dysprosium to replace light rare earth elements such as neodymium, firstly, the price of heavy rare earth elements such as terbium and dysprosium is very expensive, and the increase of the content of terbium and dysprosium will inevitably greatly increase the production cost. With the increase of terbium and dysprosium content, the remanence B of the magnet r and maximum energy product (BH) max And so on, the magnetic properties are reduced more, which limits the method. Moreover, from the perspective of rare earth resources, the addition of rarer heavy rare earth elements such as terbium and dysprosium will inevitably aggravate the imbalance in the utilization of rare earth elements.

Refining the grains of the sintered blank has very strict requirements on the control of process parameters such as oxygen control, sintering temperature, and sintering time in the entire production. The requirements for equipment are very high, which is difficult to achieve in actual production; The optimization of grain boundary structure with heavy rare earth elements is a very popular research direction in recent years. Heavy rare earth fluorides such as terbium and dysprosium have been used in many magnet manufacturers. However, the intellectual property rights of this technology are controlled by foreign companies such as Japan. Production according to this process needs to pay high patent fees. In addition, in the infiltration process of this technology, the diffusion depth of infiltration is relatively shallow, and the effect on larger magnets is not obvious, which still limits its use.

Domestically, technologies such as magnetron sputtering have been developed to replace heavy rare earth fluorides such as terbium and dysprosium at grain boundaries, and their various technical indicators are superior to the latter, but due to extremely high requirements for equipment and process control, especially the cost Too high, it is still difficult to promote on a large scale

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