JP2001335815A - Recovery method for rare earth magnet alloy waste powder - Google Patents

Abstract

(57) [Problem] To provide an economically advantageous recovery method for effectively using rare earth magnet alloy waste powder containing much oxygen. SOLUTION: A hydroxide and / or an oxide in a rare earth magnet alloy waste powder is reduced by metallic calcium, and the reduced powder is heated and melted with a CaF ₂ -based flux to separate the alloy and the flux. A method for recovering rare earth magnet alloy waste powder, comprising recovering an alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for recovering an alloy from a rare earth magnet alloy waste powder.

[0002]

2. Description of the Related Art In recent years,
The production of magnets containing rare earth metals has increased, and accordingly, the amount of defective powder generated in the magnet forming process and the amount of cutting powder and cutting powder generated in the processing process have increased. These powders generated in the magnet manufacturing process usually have a particle size of several tens of microns or less and are easily oxidized, and contain several thousand ppm to several percent of oxygen, and cannot be used as raw materials for magnets as they are.

Conventionally, alloy powders and alloy chips containing rare earths having a large amount of oxygen are dissolved in an acid such as hydrochloric acid, and a precipitant such as oxalic acid is added thereto to precipitate rare earth oxalate and the like. Recovery as a rare earth oxide through drying and firing steps has been performed (Japanese Patent Publication No. 5-14777).

However, such a wet process requires a large amount of acid and a precipitant, requires a long process,
It is necessary to treat Fe of low value, it is necessary to bake it into an oxide, and what is obtained is an oxide. There were problems such as the need to use metal.

[0005] Further, attempts have been made to recover the alloy by heating and melting magnet scrap and sludge (USP
5,087,291, U.S. Pat. No. 5,174,811), and a powder containing a large amount of oxygen is difficult to dissolve by heating, and has a problem that a large amount of slag having a high melting point is generated and the yield is poor.

Further, a method has been proposed in which a valuable composition is obtained by pulverizing a rare earth element-containing substance, washing with acid, reducing Ca, and wet-cleaning the generated CaO and residual Ca to obtain a valuable composition (JP-A-11-319752). In this method, it takes time and labor for wet treatment such as washing with water and acid, and there is a problem that the amount of oxygen in the obtained alloy powder is not yet sufficiently low. A method for collecting powder has been desired.

SUMMARY OF THE INVENTION The present invention meets the above-mentioned demand, and can easily, reliably and inexpensively recover an alloy having a low oxygen content from a rare earth magnet alloy waste powder, and recycle the alloy, thereby effectively utilizing resources. In view of the above, it is an object of the present invention to provide a method for recovering rare earth magnet alloy waste powder which is preferable from the viewpoint of

[0008]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to achieve the above object, and as a result, reduced metallic alloy waste powder containing a large amount of oxygen by adding metallic calcium to the waste powder. To CaO, then add CaF
By adding and heating and melting the system ₂ flux, Ca
O is dissolved in CaF ₂ and separated from the alloy,
The inventors have found that an alloy ingot with reduced oxygen can be recovered by this, and have accomplished the present invention.

Therefore, the present invention reduces the hydroxide and / or oxide in the rare earth magnet alloy waste powder with metallic calcium, and then heat-melts the reduced powder with a CaF ₂ -based flux to separate the alloy and the flux. The present invention provides a method for recovering rare earth magnet alloy waste powder, wherein the alloy is recovered by separation.

As described above, with the increase in the production of rare earth magnets containing rare earth metals, the amount of waste powder such as powdery cutting debris and grinding debris generated during processing and defective powder during molding increases. However, shavings generated particularly when the magnet is machined by grinding or cutting are usually fine powders of several tens μm or less, and are wetted by the grinding fluid. This is dried to produce a large amount of oxygen even as a magnet alloy powder, and cannot be used as a raw material powder for magnets as it is. According to the present invention, for example, an Nd-Fe-B-based and Sm-Co-based rare earth magnet alloy waste powder having an oxygen content of several thousand ppm to several percent (0.2 to 5 wt%) can be inexpensively used as a raw material alloy for magnets. Can be collected.

Hereinafter, the present invention will be described in more detail.
In the method for recovering rare earth magnet alloy waste powder of the present invention, first, metal calcium (Ca) is added to the rare earth magnet alloy waste powder, and hydroxides and / or oxides in the alloy waste powder are reduced by metal Ca.

In this case, the type of the rare earth magnet alloy is not particularly limited, but Nd-Fe-B-based and Sm-Co-based rare-earth magnet alloys are preferably used. Here, Nd-Fe-B
The system has a basic composition of Nd ₂ Fe ₁₄ B, and Sm-Co
The system may be any one having a basic composition of SmCo ₅ or Sm ₂ Co ₁₇ , and may be one substituted with a rare earth element, transition metal or the like other than the basic composition.

As the rare earth magnet alloy waste powder, defective powder in a magnet forming step, cutting powder or cutting powder in a processing step, and the like can be used.
Those containing as much as ５5% by weight can also be used effectively. The particle size of the waste powder is not particularly limited, but those having an average particle size of about 0.5 to 100 μm can be suitably used.

In the present invention, first, metallic Ca is preferably added to and mixed with the dried waste powder, and the mixture is heated to convert the oxygen content in the powder into CaO. The usual method and apparatus are used for drying the waste powder. However, since the activity of the powder is high and it is easily oxidized, the powder is dried in a vacuum or a non-oxidizing atmosphere.
Heating and dehydration at 50 ° C. or lower (preferably 50 to 110 ° C.) is preferred, and drying under reduced pressure is preferred.

Granular or shaved small lumps are economically preferable as the metal Ca. The amount of the metal Ca varies depending on the amount of oxygen contained in the powder.
1.3 times, preferably 1.05 to 1.3 times is appropriate. If it is less than this, the reduction is insufficient and rare earth oxide remains. At most, the effect of reduction does not change much, and excess Ca
Remains. Further, the reduction temperature is 800 to 1,200 ° C, preferably 900 to 1,100 ° C. If the temperature is low, the reduction reaction does not proceed, and if the temperature is too high, the effect does not change. The atmosphere is desirably an inert atmosphere such as Ar or N ₂ to prevent oxidation.

In the present invention, the reduced alloy powder is then heated and melted with a CaF ₂ -based flux. Ca
As the F ₂ -based flux, CaF ₂ alone or CaF ₂ as a main component, and an alkali metal halide (LiF,
NaF, KF, LiCl, NaCl, KCl, etc.), alkaline earth metal halides (MgF ₂ , BaF ₂ , Mg
Cl ₂ , CaCl ₂ , BaCl ₂ , etc.) and one or more rare earth metal halides (NdF ₃ , NdCl _3, etc.)
Mixed halide is used F ₂ to comprise 0-50 wt%.

In this case, the amount of the CaF ₂ -based flux used is 1 to 100 parts by weight based on 100 parts by weight of the reduced alloy powder.
The amount is preferably 5 parts by weight, more preferably 5 to 50 parts by weight.

For the heat melting, a known apparatus such as a plasma melting furnace, an electroslag melting furnace, an arc melting furnace, a high-frequency induction melting furnace, etc., which can be heated to a temperature equal to or higher than the melting point of the alloy and flux in a non-oxidizing atmosphere can be used. . Electroslag melting furnace capable of continuously manufacturing an ingot by gradually lowering or raising the solidified portion while maintaining the molten pool while heating and melting the alloy powder, in particular,
An arc melting furnace, a plasma melting furnace, or the like is preferable because high-temperature heating can be easily performed. The alloy and the CaF ₂ -based flux are separated by a specific gravity difference in the molten pool.

In a high-frequency induction heating melting furnace, alloy powder is heated and melted together with a CaF ₂ -based flux in a crucible. Similarly, a CaF ₂ -based flux in which CaO is dissolved is mixed with a low-viscosity liquid at the top of the alloy. And then cast into a suitable mold to obtain the separated alloy and C
it is possible to recover the aF _2-based flux.

The material of the crucible is made of heat-resistant and corrosion-resistant ceramics or metals having little reaction with alloys and fluorides, for example, BN,
W, Ta, Mo, etc. are used. When using a metal crucible, 1 to 100 parts by weight, preferably 20 to 50 parts by weight, of the rare earth metal and the above mixed halide is added to 100 parts by weight of the alloy powder to lower the melting point of the alloy or the flux. It is desirable to reduce the reaction between the crucible and the alloy. In this case, it is preferable to dissolve at a temperature of not less than the melting point of the alloy or the flux and not more than 1,400 ° C. for 3 to 30 minutes as the heating temperature.

Further, Ca reduction and heat dissolution can be continuously performed by the same apparatus. In this case, the dried waste powder, metal Ca, CaF ₂ -based flux, and if necessary, the same rare earth metal (for example, , Nd, Sm) are mixed in an amount of 0 to 50 parts by weight with respect to 100 parts by weight of the dried waste powder, and the mixture is heated to cause a reduction reaction. Subsequently, the temperature is further increased to dissolve the alloy and the flux. Separation,
It can also be collected.

In this case, impurities such as carbon are extracted into the molten flux, and impurities in the alloy are reduced.

The waste powder is reduced by Ca as described above,
Rare earth hydroxides and oxides are converted into CaO, and CaO is heated and dissolved with a CaF ₂ -based flux, so that CaO becomes CaF _2.
Dissolution in the system flux reduces the viscosity, and the separation of the alloy and the flux is easily achieved due to the difference in specific gravity.

A magnet alloy having a predetermined composition can be produced by a known method in which a rare earth metal or another magnet component metal is added to the recovered alloy, if necessary, and then heated and melted.

[0025]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 NdＮ30 wt%, Dy ≒ 3
Nd-based rare earth magnets containing wt%, B ≒ 1wt%, residual Fe, Co, etc., are ground and ground (water content ≒ 40%) by suction filtration and dewatered, and then dried under reduced pressure at 50 ° C. in a vacuum dryer. Into a powder. The oxygen content of this powder was 4.0 wt%. 110 g of metal Ca per 1 kg of this dry powder
(10% excess of the theoretical amount required to reduce the hydroxide)
Mix, put in a stainless steel container, 1,000 ° C in Ar
For 3 hours. As a result of examining the product by X-ray diffraction, C
The generation of aO was confirmed. 1kg of this Ca reduced powder
280 g of CaF ₂ per unit, and heated and melted at about 1,600 ° C. while being put into a plasma melting furnace, to obtain a diameter of 50 mm.
A rod-like alloy ingot of φ × length ≒ 120 mmL was obtained.
The oxygen content in the alloy has dropped to 250 ppm and CaF
_{The 2-} CaO flux was separated from the alloy at the top of the ingot.

[Example 2] Sm containing about 25 wt% of Sm
The grinding dust of the Co-based rare earth magnet was dried in the same manner as in Example 1 to obtain a powder having an oxygen content of 2.7% by weight. This dry powder 1
81 g of metallic Ca per kg (20% excess of theoretical amount) was mixed, placed in a stainless steel container, and heated at 950 ° C. for 3 hours in Ar to obtain a reduced powder. This Ca reduced powder 1
95 g of CaF ₂ was mixed per kg, and an alloy ingot was obtained in the same manner as in Example 1. The amount of oxygen in the alloy is 160p
pm.

Example 3 1 kg of the Ca-reduced powder of Example 1 was placed in a Ta crucible, and 300 g of Nd metal was added.
280 g of aF ₂ and 70 g of LiF were added and heated and melted at 1,350 ° C. in a high frequency induction melting furnace. After dissolution, the mixture was held for 5 minutes and cast into a mold. After cooling, the casting was taken out, and the CaF ₂ —LiF—CaO flux was separated from the alloy at the top of the alloy, and the alloy and the flux could be easily separated and recovered. The oxygen content in the alloy was 220 ppm.

[Comparative Example 1] The Ca-reduced powder of Example 1 was heated and melted at about 1,600 ° C. without being mixed with CaF ₂ and directly charged into a plasma melting furnace. The obtained alloy ingot was difficult to separate from CaO, and it was found that CaO was dispersed in the ingot. Also,
The amount of oxygen in the alloy was 1,200 ppm.

[0030]

According to the present invention, a rare-earth magnet alloy waste powder which has a large amount of oxygen which has been conventionally recovered only by a wet treatment and is unsuitable as a magnet raw material can be reused by a simple process with a reduced oxygen-containing raw material. Can be collected in alloy ingots,
Its industrial value is very large.

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Claims (1)

[Claims] 1. A method of reducing hydroxide and / or oxide in a rare earth magnet alloy waste powder with calcium metal, and then heating and melting the reduced powder with a CaF ₂ -based flux to separate the alloy and the flux. And recovering the rare earth magnet alloy waste powder.