Surface anti-oxidation treatment method of NdFeB magnetic powder

A treatment method and pre-oxidation treatment technology, applied in inductor/transformer/magnet manufacturing, metal processing equipment, electrical components, etc., can solve the problems of difficult to control surface modification process, high cost of electroplating, and large environmental pollution, and achieve high efficiency The effect of rapid magnetic powder surface modification treatment, improving oxidation resistance and increasing bulk density

Active Publication Date: 2019-03-12
HAIAN INST OF HIGH TECH RES NANJING UNIV +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the cost of the electroplating method is high and the environmental pollution is large.
Although the anti-oxidation method of the traditional NdFeB permanent magnet superfine magnetic powder surface is better, but the efficiency is low, and it is difficult to control the surface modification process

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] NdFeB permanent magnet 10um ultra-fine powder is spread on the conveyor belt with a thickness of 1mm, and passes through the spray evaporation chamber at 0.5m / min. The oxidation temperature is 60°C and the relative humidity is 80%. The spray evaporation solution is a composite solution. The solution contains Mass concentration 2wt.% dichromate solution and mass concentration 3wt.% phosphoric acid solution; Gained pre-oxidized NdFeB ultra-fine magnetic powder is tiled on the conveyor belt with a thickness of 1mm again and passes through the spray evaporation chamber at 0.5m / min. , the spray-evaporated solution is 1-5wt.% sodium bisulfite solution, and a spray evaporator is added at the outlet of the evaporation chamber to spray and evaporate the sodium hydroxide solution, and the PH=9 and temperature of the moisture are controlled by adjusting the evaporation rate. The temperature is 50°C and the relative humidity is 80%. Finally, the NdFeB ultra-fine magnetic powder is s...

Embodiment 2

[0020] The NdFeB permanent magnet 20-40um fine powder is spread on the conveyor belt with a thickness of 1.5mm, and passes through the spray evaporation chamber at 0.4m / min. The oxidation temperature is 60°C and the relative humidity is 80%. The spray evaporation solution is a composite solution. The solution contains a mass concentration of 1wt.% dichromate solution and an amount concentration of 4wt.% phosphoric acid solution; the resulting pre-oxidized NdFeB ultrafine magnetic powder is spread on the conveyor belt with a thickness of 1mm and passes through the spray evaporation chamber at 0.5m / min , at this time, the solution evaporated by spraying is a certain amount of sodium bisulfite solution, and a spray evaporator is added at the outlet end of the evaporation chamber to spray evaporate the sodium hydroxide solution, and the PH=10 of the moisture is controlled by adjusting the evaporation rate, and the temperature is 60°C, relative humidity 70%; finally, the NdFeB ultra...

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Abstract

The present application discloses a method for anti-oxidation treatment of the surface of NdFeB magnetic powder, including steps: (1) Pre-oxidizing the NdFeB magnetic powder by means of spray evaporation, and the spray evaporation solution has a mass concentration of 1-2wt.% heavy chromium salt solution, a mixed solution of phosphoric acid solution with a mass concentration of 3-5wt.%; (2), the pre-oxidized NdFeB magnetic powder is treated twice by spray evaporation, and the spray evaporation solution is 1-5wt.% bisulfite Sodium solution; (3), adopting spray evaporation method to post-treat NdFeB magnetic powder, the spray evaporation solution is sodium hydroxide solution; (4), drying, and obtaining ultra-fine NdFeB permanent magnets with a dense anti-oxidation film on the surface magnetic powder. The invention uses a spray evaporation device to realize efficient and rapid surface modification treatment of magnetic powder, and the formed composite film is relatively dense and uniform. The burrs and edges and corners of the ultrafine magnetic powder are eliminated through the pre-oxidation process, and the fluidity of the NdFeB ultrafine magnetic powder is increased. and bulk density, which improves the oxidation resistance of NdFeB ultrafine magnetic powder.

Description

technical field [0001] The present application relates to the surface treatment process of magnetic materials, in particular to an anti-oxidation treatment method for the surface of NdFeB magnetic powder. Background technique [0002] The characteristics of NdFeB permanent magnet alloy powder are: good magnetic properties and good mechanical properties, but low Curie temperature Tc, poor temperature stability, and poor chemical oxidation resistance, thus limiting its application range. The premise of the application of iron-boron permanent magnet materials is to first solve the problems of anti-oxidation and anti-corrosion of materials. In particular, the rare earth elements in the NdFeB alloy powder are active in nature, which makes the oxidation resistance of the entire NdFeB magnetic powder very poor, and it is easy to oxidize and rust in a hot and humid environment. In addition, the magnetic properties of NdFeB permanent magnet materials have a great relationship with t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B22F1/00H01F41/00
CPCH01F41/00B22F1/145
Inventor 雷成龙曹江平唐少龙都有为
Owner HAIAN INST OF HIGH TECH RES NANJING UNIV
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