JPH05263110A - Production of alloy powder containing rare-earth metal by diffusion method - Google Patents

Abstract

PURPOSE:To obtain a magnetic alloy powder contg. a rare-earth metal and excellent in magnetic characteristics by the diffusion method. CONSTITUTION:A mixture of rare-earth metal and boron, a rare-earth metal- boron alloy or their mixture are brought into contact with the surface of the extra-fine wire or extra-thin sheet consisting essentially of iron or iron and boron and having <=5mum average crystalline grain size, the wire or sheet is heated at 600-1100 deg.C, and the formed alloy is crushed to obtain an alloy powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for producing an alloy powder containing a rare earth metal by using a diffusion method.

[0002]

2. Description of the Related Art Due to their excellent magnetic properties, alloy magnets containing rare earth metals have been used in a wide range of fields from home appliances to communications, audio equipment, medical equipment, and general industrial equipment.

A method for producing such alloy powder containing a rare earth metal by a reduction diffusion method is known.

That is, in this method, first, a mixture of a metal Ca powder, a rare earth oxide powder, and a metal raw material powder is heated in an inert gas or a vacuum atmosphere to convert the rare earth oxide into a rare earth metal. Simultaneously with the reduction, the generated rare earth metal is diffused into other metal particles forming a part of the alloy component to obtain an alloy powder having a desired composition.

In this case, unnecessary substances such as oxides of the residual metal contained in the reaction product obtained by heating the mixture or by-produced by the reaction with the residual metal Ca are generated by the reaction. When the product is cooled, the product is put into water, and if necessary, the product is removed from the reaction product by carrying out a wet treatment in which the product is washed with an acid.

According to this method, a relatively inexpensive oxide can be used as a rare earth metal raw material, a melting and casting process is not necessary, and a lumpy reaction product is highly disintegratable, so that an alloy powder having a required particle size can be easily obtained. It is considered to be an excellent method from various aspects such as that it can be obtained.

[0007]

Although it is a reduction diffusion method which is considered to be an excellent method from various aspects as described above, it is a raw material which is not in the form of powder as an iron raw material, for example, a foil-shaped body, a needle. When using a raw material such as a sheet, a sheet, or a plate,
Since the degree of contact between these iron raw materials and other raw material powders deteriorates, diffusion of alloying elements deteriorates, and as a result, it is difficult to obtain an alloy having a desired composition. As the alloy particles were generated, the growth of the crystal grains of the obtained alloy was rarely directed in a fixed direction, and it was difficult to enhance the magnetic orientation of the magnet used as a product.

Further, the alloy powder based on the conventional reduction-diffusion method can only obtain a product having an average grain size of 10 μm or more, and it is difficult to use it as a raw material powder for a resin-bonded magnet, which is expected to have high performance. It was

In view of the above circumstances, the present invention provides a method of controlling the crystal grain size of an iron raw material in the use of the diffusion method.
The growth of crystal grains of the obtained alloy is directed in a fixed direction, and the magnetic properties of the product are improved.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have found that on the surface of an ultrafine wire or an ultrathin plate containing iron or iron and boron as main components and having an average grain size of 5 μm or less, A mixture of a rare earth metal and boron, a rare earth-boron alloy, or a mixture thereof is heated in a state of being in contact with the mixture at a temperature of 600 ° C to 1100 ° C, and the resulting alloy is pulverized into powder. The present invention relates to a method for producing an alloy powder containing a rare earth metal using a diffusion method.

[0011]

In the present invention, either a mixture of a rare earth metal and boron, or a rare earth-boron alloy or a mixture thereof is formed on the surface of an ultrafine wire or an ultrathin plate containing iron or iron and boron as main components and having an average grain size of 5 μm or less. While keeping the mixture in contact with, heating at a temperature of 600 ℃ ~ 1100 ℃,
The generated alloy was pulverized into powder because the ultrafine wire or ultrathin plate having an average crystal grain size of 5 μm or less was used as a raw material, the growth of crystals constituting the heat-treated body was suppressed, and diffusion was performed. It is possible to make the crystal grain size of the generated alloy powder fine, and it also has the function of promoting the diffusion reaction, and is composed of ultrafine crystal grains suitable for use as raw material powder for resin-bonded magnets. This is to make the raw material powder easily available.

The average grain size is set to 5 μm or less because the coercive force of the resin-bonded rare earth alloy magnet is improved when an ultrafine wire or an ultrathin plate having an average grain size of more than 5 μm is used as a raw material. This is because it will not be possible.

Further, the heat treatment temperature for diffusing the rare earth metal or boron is defined as 600 ° C. to 1100 ° C. The reason is that the diffusion reaction of the rare earth metal or boron is extremely advanced when the temperature is lower than 600 ° C. Difficult to do, on the contrary, 110
If processed above 0 ° C, the alloy will melt,
This is because it becomes impossible to obtain an alloy having a desired shape.

[0014]

【Example】

Example 1 It was produced by an electrolytic deposition method using an electrolytic solution containing iron and boron ions, and had a composition of 98.
0 wt%, B is 2.0 wt%, average thickness is 24 μm, average grain size is 0.6 μm, F
67 g of e-B alloy flakes and 33 g of metallic neodymium flakes having a purity of 99.9% by weight and an average thickness of 12 μm were alternately laminated and pressed, and then the pressed body was made of alumina. The resulting reaction product was a flaky alloy powder, and the composition of the reaction product was obtained by transferring the reaction product to a container made of aluminum and holding it at 1000 ° C. for 4 hours in a high vacuum atmosphere of 1 × 10 ⁻⁵ Torr. Nd is 33.1% by weight and Fe is 65.4.
% By weight, B was 1.3% by weight and O was 0.2% by weight.

When the cross section of the alloy piece obtained as described above is observed with a microscope, the crystal grain size is 1.5 μm.
Met.

Next, 1.5 g of the epoxy resin was added to 100 g of the alloy powder obtained by crushing the alloy pieces to a particle size of 35 mesh (JIS) or less using a disc mill.
0.5g of hardener is mixed and 4.2 for this mixture
After applying pressure of t / cm ² for compression molding, 120 ° C for 1
After heat treatment over time, the heat-molded product is cooled to obtain a cured product having a diameter of 10 mm and a height of 7.5 mm, and the coercive force of this cured product is measured using a Cioffi type self-focusing meter. When measured, it showed a value of 5 KOe.

Example 2 When the same treatment as in Example 1 was carried out except that the treatment temperature at the time of heating the molded body was 900 ° C., the obtained magnet had a coercive force of 5.1 KOe and a crystal grain size thereof. Was 1.4.

The composition of the obtained alloy powder has Nd of 3
3.2 wt%, Fe 65.3 wt%, B
Was 1.3% by weight and O was 0.2% by weight.

Example 3 When the same treatment as in Example 1 was carried out except that the treatment temperature at the time of heating the molded body was 700 ° C., the obtained magnet had a coercive force of 3.8 KOe and a crystal grain size thereof. Was 1.2.

The composition of the obtained alloy powder has Nd of 3
2.4 wt%, Fe 66.0 wt%, B
Was 1.3% by weight and O was 0.3% by weight.

Example 4 Produced by the electrolytic deposition method, the purity was 99.9% by weight, the average thickness was 23 μm, and the average crystal grain size was 0.8.
66 g of iron foil with a Nd of 96.
2% by weight, B is 3.8% by weight, and 34 g of Nd-B alloy foil having an average thickness of 15 μm are alternately laminated and pressure-molded at a pressure of 4.2 t / cm ^2. The molded product was transferred to an alumina container and subjected to heat treatment at 1000 ° C. for 4 hours under a high vacuum of 1 × 10 ⁻⁵ Torr, and the reaction product was flaky alloy powder, Its composition is Nd
Is 33.4% by weight, Fe is 65.1% by weight, B is 1.2% by weight, O is 0.3% by weight, and the average grain size is 1.6 μm. It was

The alloy powder thus obtained was crushed to a size of 35 mesh (JIS) or less using a disc mill,
50 g of crushed alloy powder, 1 g of epoxy resin and 0.2 g of curing agent are mixed, the mixture is compression molded at a pressure of 7 t / cm ² , and further heated at 120 ° C. for 1 hour to have a diameter of 10 mm. As a heat-molded body having a height of 7.5 mm, the coercive force of this heat-molded body was measured using a Cioffi type self-recording magnetometer, and a value of 5 KOe was shown.

Example 5 The coercive force of the obtained magnet was 4.8 KOe when the same treatment as in Example 4 was carried out except that the treatment temperature at the time of heating the molded body was 900 ° C.

The composition of the obtained alloy powder has Nd of 3
3.0 wt%, Fe 65.5 wt%, B
Was 1.3% by weight and O was 0.2% by weight, and it was confirmed that the crystals constituting this alloy powder had an average grain size of 1.6 μm.

Example 6 The coercive force of the obtained magnet was 3.6 KOe when treated in the same manner as in Example 4 except that the treatment temperature at the time of heating the molded body was 700 ° C.

The composition of the obtained alloy powder has Nd of 3
2.9% by weight, Fe 65.4% by weight, B
Was 1.3% by weight and O was 0.4% by weight, and it was confirmed that the crystals constituting this alloy powder had an average grain size of 1.3 μm.

Comparative Example 1 When the same treatment as in Example 1 was carried out except that the average grain size of the Fe-B alloy foil was 7.5 μm, the coercive force of the obtained magnet was only 1.8 KOe. Although there was not,
The composition of the obtained raw material powder was such that Nd was 33.0% by weight, Fe was 65.5% by weight, B was 1.3% by weight, and O was 0.2% by weight. It was found that the crystals constituting this alloy powder had an average grain size of 8.1 μm.

Comparative Example 2 When the same treatment as in Example 4 was carried out except that the average grain size of the Fe foil was 6.5 μm, the coercive force of the obtained magnet was only 2.0 KOe. The composition of the obtained alloy powder was such that Nd was 32.8% by weight, Fe was 65.7% by weight, B was 1.2% by weight, and O was 0.3% by weight. It was confirmed that the crystals constituting this alloy powder had an average grain size of 7.3 μm.

The above results are shown in Table 1.

[0030]

[Table 1]

The crystal grain size was measured using an image analysis analyzer (type CIS-1) manufactured by GALAI.

As described above, according to the present invention, all of the crystals constituting the alloy powder in the production of the magnet alloy have the average grain size of 5.0 μm or less necessary for improving the performance of the resin magnet. This has been confirmed, and it has become possible to significantly improve the coercive force of the resin magnet manufactured using this raw material powder.

[0033]

According to the present invention, it is recognized that all of the crystals constituting the raw material powder at the time of producing a magnet alloy have a fine average grain size of 5.0 μm or less. When it was manufactured, it was possible to significantly improve the degree of orientation of the magnetic properties, so it became possible to supply highly accurate materials economically and in a stable state. There was a great contribution to the industry that was hoped for.

Claims (1)

[Claims] 1. A surface of an ultrafine wire or an ultrathin plate containing iron or iron and boron as main components and having an average crystal grain size of 5 μm or less,
A mixture of a rare earth metal and boron, a rare earth-boron alloy, or a mixture thereof is left in contact with the mixture, 6
A method for producing an alloy powder containing a rare earth metal using a diffusion method, which comprises: heating at a temperature of 00 ° C to 1100 ° C; and pulverizing the produced alloy into a powder.