Method for improving oxidation resistance through normal-temperature blackening of rare earth permanent magnet powder

Abstract

The invention provides a method for improving oxidation resistance through normal-temperature blackening of rare earth permanent magnet powder. The method comprises the following steps: the rare earthpermanent magnet powder is dipped in normal-temperature blackening water treatment liquid, prepared by stated steps and containing divalent copper ions, a complexing agent and an oxidizing agent, forreplacement-oxidation reaction under normal temperature; different reaction times are controlled; and after the reaction is finished, magnetic powder is magnetically separated from reaction liquid bya permanent magnet for such steps as solid-liquid separation, distilled water washing, anhydrous ethanol extraction and 50-DEG C low-temperature drying to obtain the magnetic powder coated with a thin and compact oxide film on the surface. The method has the characteristics of simple process operation, low energy consumption, high film forming efficiency, environmental protection and the like; and the treated rare earth permanent magnet powder is more excellent in high-temperature oxidation resistance.

Description

technical field [0001] The invention relates to a method for coating the surface of a rare earth permanent magnet powder with an anti-oxidation layer by utilizing the technology of chemical blackening treatment, which belongs to the technology of powder surface treatment. Background technique [0002] Compared with ferrite, rare earth permanent magnet powders such as NdFeB, SmFeN, SmCo, etc. have a higher maximum magnetic energy product and are widely used. With the development of miniaturization and high power of household appliances, the composite rare earth permanent magnet material obtained by injection molding and extrusion processing of rare earth permanent magnet powder and polymer material has the advantages of simple production process, high product size accuracy, The advantages of good consistency are widely used in micro-motors. When injection molding is extruded, high temperature treatment is required, especially when polyphenylene sulfide is used as a polymer b...

AI Technical Summary

Problems solved by technology

However, the traditional bluing process uses sodium hydroxide as the reaction medium, and the reaction temperature is high, reaching 110-130°C. At the same time, the concentration of sodium hydroxide is high, reaching 200g / L, so a large amount of alkali mist is generated, which pollutes the environment; the generated oxidation The thickness of the film is not easy to control; since the main component of the formed oxide film is soft magnetic Fe3O4, if the rare earth permanent magnet powder adopts the traditional bluing process, the performance of the rare earth permanent magnet powder will be reduced and its magnetic properties will be affected; and in order to overcome the high temperature The problem of blackening, the normal temperature blackening technology with selenous acid as the main component has been proposed, but selenate is highly toxic and not environmentally friendly

Therefore, aiming at the problems that the silane film surface coating process of rare earth permanent magnet powder is not resistant to high temperature, and the bluing treatment process is not environmentally friendly and high energy consumption, we have invented a new normal temperature through many experiments and theoretical combinations. Blackening process, this method forms a dense copper oxide film on the surface of rare earth magnetic powder through replacement-oxidation reaction. A thin and dense oxide film, thereby improving the high-temperature oxidation resistance of magnetic powder, while not polluting the environment, has achieved good results