JPS62132302A - Rare earth element-iron-boron alloy powder and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain preferable magnetic properties of rare earth element-iron-boron alloy powder without necessity of heat treatment by composing alloy powder of a main phase disposed at its center, a coercive force generating phase covered around the main phase, and outermost side rare earth rich element phase covered around the coercive force generating phase. CONSTITUTION:A mean composition contains 8-25atom% of a rare earth element, 3-15atom% of boron, residal iron (part of Fe may be substituted for one or more of Co, Ni, Al, Mn) and inevitable impurities. Each particle contains a central main phase of a tetragonal crystal, a coercive force generating phase of body-centered cubic crystal covered on the main phase and laminated on the main phase, and rare earth rich element phase made of solid solution including 80-95atom% of the rare earth element. Mean particle size is 2-50mum. Since the obtained R-Fe-B alloy powder has a structure capable of having high performance as a magnet in the individual particles, the powder is proper for manufacturing a permanent magnet. Since a heat treatment for improving the magnetic properties is not necessary, the powder is advantageous in manufacturing a resin magnet and is particularly excellent as alloy powder for the resin magnet.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to rare earth-iron-boron alloy powder.

In particular, the present invention relates to an alloy powder suitable for use in resin magnets.

[Conventional technology]

Rare earth (R)-iron (Fe)-boron (B) magnets are made from cobalt (Go), which is used in alnico magnets and rare earth-cobalt magnets, whose raw material supply is unstable, and which is particularly rare and expensive among rare earths. It is known as a high-performance magnet that does not require the use of samarium (Sm). This R-Fe-
The R-Fe-B alloy powder used for manufacturing B-based magnets is manufactured by a melting method or a reduction diffusion method.

The melting method involves melting and casting pure iron, Fe-8 alloy, and rare earth metals as starting materials, and then coarsely and finely pulverizing the resulting ingot.The reduction diffusion method involves oxidizing rare earth elements. Mix metal powder, iron powder, Fe-B powder, and metal Ca or Ca)I□ and heat to 900~
R-Fe-B alloy powder is obtained by heating to 120°C and wet-processing the resulting mixture containing CaO and residual Ca.

[Problem that the invention seeks to solve]

However, the alloy powder obtained by the above manufacturing method has poor magnetic properties as it is, and heat treatment is required to improve them. Therefore, it is suitable as a raw material for manufacturing sintered magnets that involve firing, but alloy powder is combined with epoxy resin, etc.
In the case of resin magnets manufactured by molding, the required heat treatment cannot be performed, so the magnetic properties of the resulting resin magnets are significantly inferior to those of sintered magnets.

The purpose of the present invention is to solve this problem and to produce R-Fe-[1 series magnets that have excellent magnetic properties and have good magnetic properties even when used as raw materials for resin magnets. An object of the present invention is to provide a B-based alloy powder and a method for producing the same.

Means for Solving Problem C] That is, the present invention solves the problems of the above-mentioned prior art.
5 at.% and the balance is iron (part of Fe is Co, Ni).

(may be substituted with one or more of Al and Mn)
and unavoidable impurities.

Each particle has a tetragonal central main phase, a body-centered cubic coercive force-generating phase that covers the main phase and is aligned with the main phase, and a rare earth element 80 that covers the coercive force-generating phase. The present invention provides a rare earth-iron-boron alloy powder composed of a rich rare earth phase consisting of a solid solution containing ~95 at%, and having an average particle size of 2 to 50 μm.

In the present invention, the rare earth element (R) includes lanthanum (L
a), cerium (Ce), praseodymium (Pr) + neodymium (Nd), samarium (Sm), europium (
Eu), gadolinium (Gd), televisionram (Tb),
Dysprosium (Dy), holmium ()Io), erbium (Er), thulium (Tm), ytterbium (
Yb), lutetium (Lu), promethium (Pm),
and yttrium (Y).

Among these rare earth elements, light rare earth elements such as Nd and Pr are preferred, and other rare earth elements are preferably used together with the light rare earth elements.

The alloy powder of the present invention has a rare earth element content of 8 to 25 at%, preferably 12 to 20 at%, in the average composition. If it is less than 8 at%, the rare earth phase becomes too thin and high coercive force cannot be obtained, and if it exceeds 25 at%, the rich rare earth phase becomes too thick and the residual magnetic flux density (Br) decreases, resulting in a high performance magnet. I can't.

Boron ([3) is 3 to 15 atomic% in the average composition
, preferably 5 to 10 atom %. If it is less than 3 at%, a phase that generates coercive force (iHc) is formed and creeps, so high coercive force cannot be obtained, and if it exceeds 15 at%, the coercive force generating phase becomes too thick and the residual magnetic flux density (Br) decreases. Therefore, the performance of the resulting magnet deteriorates.

The alloy powder of the present invention has a main phase located in the center, a coercive force generating phase surrounding and coating the main phase, an outermost rich rare earth phase surrounding and coating the coercive force generating phase, and a coercive force generating phase surrounding and coating the main phase. ).

The main phase in the center generally has R8~178~25 atoms~15
A tetragonal intermetallic compound consisting of 3 to 15 atoms of iron and inevitable impurities is also formed.

The coercive force generating phase consists of a body-centered cubic intermetallic compound,
It is important that it is formed in contact with the main phase in a well-aligned state.

In this specification, two adjacent phases are not "aligned" means that the coercive force generating phase is in the main phase at the center with a width of 10 to 3
0 people had protrusion-like bites with a length of about 100 Å or more. This means that in the case of the R-Fe-8 alloy powder produced by the conventional reduction-diffusion method described above, both phases are not aligned because it has such protruding bites. On the other hand, "aligned layering" refers to a state in which such protruding biting has disappeared between the main phase and the coercive force generating phase.

Whether or not two adjacent phases in the alloy powder particles are aligned with each other can be measured and confirmed using, for example, a transmission electron microscope.

The coercive force generation phase is important in achieving high coercive force, and its thickness is within the range of minimum 30 and maximum 4000.
It is preferable that the average number of people is 50 to 1000 people, and more preferably within the range of a minimum of 50 and a maximum of 1000 people, with an average of 1
00 to 500 people is more preferable. If this coercive force generating phase is too thin, no improvement in coercive force (jHc) can be expected;
If it is too thick, the residual magnetic flux density (Br) tends to decrease, which is not preferable.

The rich rare earth phase is a phase mainly composed of rare earth elements and Fe, and although some B may be present, it is a solid solution phase in which rare earth elements account for 80 to 95 at %. The thickness of this rich rare earth phase ranges from a minimum of 50 people to a maximum of 10,000 people, with an average thickness of 100 people.
~5,000 people, preferably at least 5
0 people, maximum 10000 people, average 1000-5
It is preferable to be an ooo person. If this rich rare earth phase is too thin, the particles are likely to be oxidized and reversed magnetic domains are likely to occur within the particles, while if it is too thick, the amount of the main phase will be relatively reduced and the residual magnetic flux density will be lowered.

The average particle size of the R-Fe-8 alloy powder of the present invention is 2 to 50
μm, preferably 5 to 35 μm. If the average particle size is less than 2 μm, it is likely to be oxidized during various steps such as molding and heat treatment during the production of resin magnets, and the density of the resulting molded product will be low, resulting in a decrease in the residual magnetic flux density (B
r) decreases. Moreover, if it exceeds 50 μm, high coercive force cannot be obtained.

Each of the phases described above may contain impurities that are inevitably mixed in during production.

Next, a method for manufacturing the R-Fe-8 alloy powder of the present invention will be explained.

The first production method includes rare earth oxide powder or the rare earth oxide powder and rare earth metal powder, iron-containing powder, boron-containing powder, and at least one selected from alkali metals, alkaline earth metals, and hydrides thereof. , the proportion of rare earth elements, boron and iron is 8 to 25 at% of rare earth elements.
, 3 to 15 at% boron, and the balance iron, and the mixture is heated in an inert gas atmosphere or reducing atmosphere at 900 to 1200 °C, and then at 350 to 900 °C. The method consists of heating and wet processing of the resulting product mixture.

The rare earth oxides used in this production method are the aforementioned rare earth element oxides, and can be used alone or in combination of two or more. Preferably, light rare earth elements such as Nd and Pr are used as the main material.

Furthermore, as the rare earth feed material, rare earth metal powder can also be used in combination with rare earth oxide powder.

The average particle size of these rare earth oxide powders and rare earth metal powders is preferably 1 to 100 μm.

Examples of the iron-containing powder used in the above manufacturing method include iron powder, ferroboron, etc., and the particle size is 1 to 1.
00 μm is preferred.

Further, as the boron-containing powder, for example, ferroboron powder can be mentioned, and the particle size of these powders is 1 to 100μ.
m is preferred.

The alkali metals, alkaline earth metals, and their hydrides used in the above manufacturing method act as reducing agents, and specific examples include lithium, sodium, potassium,
Examples include magnesium and its hydrides, but calcium is preferred from the viewpoint of handling stability and cost. These metals or metal hydrides may be used in granular or powdered form, but from the viewpoint of cost, granular metallic calcium having a particle size of 4 mesh or less is preferred.

The amount of these reducing agents used is preferably 1.1 to 3.0 times the reaction equivalent (the stoichiometry required to reduce the rare earth oxide, 1).

According to the above manufacturing method, first, a mixture of the rare earth oxide powder and the like described above is subjected to a first heat treatment in an inert gas atmosphere. Examples of the inert gas atmosphere used include argon, nitrogen, and the like.

Further, the heating temperature at this time is preferably in the range of 900 to 1200°C, particularly 950 to 1100°C, and the heating time is not particularly limited, and heating may be performed for a time necessary to obtain a uniform alloy powder. Usually, it takes about 1 to 5 hours.

The mixture produced after the first heat treatment is subjected to the second heat treatment, but after the first heat treatment, it may be directly brought to the second treatment temperature, or it may be heated to room temperature once. After cooling, the temperature may be raised again to provide a second heat treatment. These operations are.

It is carried out in an inert gas atmosphere.

The second heat treatment 11 was also performed in an inert gas atmosphere, and the gas used was as exemplified above. The heating temperature at this time is 350°C or higher and 900°C.
℃, preferably 500 to 850℃. The heating time is sufficient for the main phase of the particles and the coercive force generating phase to be in an ordered state, and is usually about 0.1 to 4 hours. Note that this second heat treatment can also be performed in two or more stages.

The product thus obtained is a mixture containing the desired alloy powder, by-products such as oxides of alkali metals or alkaline earth metals, and residual reducing agents, and is subjected to wet processing to remove unnecessary substances. . Wet treatment is generally carried out by treatment with water and treatment with an aqueous acid solution. First, by putting the product mixture into water, CaO and Ca
is separated as Ca (OH) 2 and then treated with an aqueous solution of a weak acid such as acetic acid, formic acid, butyric acid, etc. to remove the oxide film on the particle surface.

The obtained alloy powder is washed with an organic solvent such as ethanol or acetone and dried.

Another method for producing the R-Fe-8 alloy powder of the present invention is to use 8 to 25 atomic % of rare earth elements and B3 to 15 atomic percent as one of the raw material powders.
Alloy powder consisting of a single phase structure of 3 to 15 atoms of iron and inevitable impurities (hereinafter referred to as rR-Fe-8 single phase powder)
is used.

This manufacturing method includes this R-Fe-8 single-phase powder, rare earth oxide powder or the rare earth oxide powder and rare earth metal powder, and at least one selected from alkali metals, alkaline earth metals, and hydrides thereof. , the proportion of rare earth elements, boron and iron is 8 to 25 at% of rare earth elements,
A mixed powder obtained by mixing 3 to 15 atomic % of boron and the balance iron is subjected to two heat treatments and a wet treatment in the same manner as in the first manufacturing method.

The R-Fe-8 single-phase powder used in this manufacturing method is produced by, for example, melting and casting rare earth metals, pure boron or ferroboron, and pure iron to create an ingot so as to have the desired composition. It can be obtained by grinding. The particle size of this R-Fe-8 single phase powder is 2 to 50 μm,
Particularly preferred is 5 to 35 μm.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example I 78 g of Nd, O, powder, 68 g of iron powder, 4.4 g of 830 wt% ferroboron powder, and 4.5 g of metallic Ca
were mixed.

This mixed powder was heated to 1020°C in an Ar gas atmosphere.
After raising the temperature to 30 minutes and keeping it at that temperature for 30 minutes, cool it to room temperature,
The temperature was raised again, held at 650°C for 30 minutes, and then cooled to room temperature. The obtained product was poured into 202 water to react CaO with water to form Ca (OH), and then treated with dilute acetic acid. The obtained slurry powder was washed with ethanol and dried in a vacuum dryer at room temperature under vacuum for 24 hours. The average composition of the obtained alloy powder was 14.5 atomic% Nd, Fe
They were 76.3 at% and 88.2 at%. When the particles of this alloy powder were examined using a transmission electron microscope, the average particle size was 5.
．． The average thickness of the coercive force generating phase was about 300 mm, and the average thickness of the rich rare earth phase was about 4000 mm.

It was confirmed that the coercive force generation phase and the central phase were well-aligned.

This alloy powder was mixed with epoxy resin, oriented in a magnetic field of 15 Oe, and molded at a pressure of 3t/Cm'', and then A
A heat treatment was performed at 120° C. in r gas to harden the resin and create a magnet. The magnetic properties of the magnet are Br8. OKG
, iHc 2.5 to Oe, (BH)max 5.3
It was MGOe.

Comparative Example 1 An alloy powder was produced in the same manner as in Example 1, except that the second heat treatment at 650° C. was not performed. The obtained alloy powder had the same composition as that produced in Example 1, an average particle size of 10 μm, and a thickness of the coercive force-generating phase of about 1 μm.
0OA, the thickness of the rich rare earth phase was about 5000 people. Observation using an electron microscope revealed that the coercive force-generating phase was embedded in the main phase at the center in the form of many protrusions, and both phases were not aligned.

When a magnet was manufactured in the same manner as in Example 1, Br6.
OKG, iHc O, 5KOe, (BH)max
It was O,3MGOe.

Example 2 Part of Nd, O, and PrgOllt as rare earth components
CezO3 or La20. Instead, iron powder and ferroboron were mixed to obtain an alloy powder having the composition shown in Table 1. The mixed powder was treated in the same manner as in Example 1 to obtain alloy powders of Samples 1 to 3. The average particle size, coercive force generating phase thickness, and rich rare earth phase thickness of the obtained alloy powder are shown in Table 1.
Shown below.

Then, in this way I! Example 1: Crushed alloy powder
A magnet was manufactured using epoxy resin in the same manner as above. Table 1 also shows the performance of the obtained magnet.

Example 3 Each metal was weighed so that Nd was 14 at %, Fe was 78 at %, and B was 88 atoms, and an alloy ingot produced by vacuum melting and casting was wet-pulverized using a ball mill for 10 hours. After vacuum drying the obtained fine powder, Nd, O, powder 4
0 g, and mixed with 3.0 g of metallic Ca.

The obtained mixed powder was subjected to two-stage heat treatment and wet treatment in the same manner as in Example 1 to produce an alloy powder.

The average composition of the obtained alloy powder was 15 at% Nd, F
e 77 at%, B88 atoms. In addition, the average particle size is 5.3 μm, and the thickness of the coercive force generation phase is approximately 300 μm on average.
The thickness of the rich rare earth facies was on average 2000 people. Using an electron microscope, it was confirmed that the main phase in the center and the coercive force generating phase were well-aligned.

A magnet was manufactured from the alloy powder thus obtained using an epoxy resin in the same manner as in Example 1. The magnetic properties of the obtained magnet were Br 7.5KG, 1llc 3.0 and Oe.
.

(B)I)max was 5.2MGOe.

Comparative Example 2 An alloy powder was produced in the same manner as in Example 3, except that the second heat treatment at 650°C was not performed.

In the obtained alloy powder, the coercive force generating phase and the rare earth phase did not completely cover the main phase. When a magnet was manufactured using this alloy powder in the same manner as in Example 1, the magnetic properties were , Br 5.5KG.

111c O,5 to Oe, (Bll)max 0.3
It was 8GOe.

〔Effect of the invention〕

The R-Fe-B alloy powder of the present invention has a structure in which each particle thereof can have high performance as a magnet, so it is suitable for manufacturing permanent magnets, and especially because of its magnetic properties. Since it does not require heat treatment, it is advantageous in producing resin magnets, and is particularly excellent as an alloy powder for resin magnets.

Claims (1)

[Claims] 1) The average composition is 8 to 25 atomic % of rare earth elements and 3 atomic % of boron.
~15 atomic % and the balance is iron and unavoidable impurities, and each particle has a tetragonal central main phase and a body-centered cubic coercive force-generating phase that covers the main phase and is aligned with the main phase. and a rich rare earth phase consisting of a solid solution containing 80 to 95 atom % of rare earth elements, which coats the coercive force generating phase, and has an average particle size of 2 to 50 μm. 2) A rare earth oxide powder or the rare earth oxide powder and rare earth metal powder, an iron-containing powder, a boron-containing powder, and at least one selected from alkali metals, alkaline earth metals, and hydrides thereof, and a rare earth element. , the proportion of boron and iron is rare earth elements 8 to 25 at%, boron 3
~15 at%, and the balance is iron, and the mixture is first heated at 900 to 1200°C in an inert gas atmosphere or reducing atmosphere, and then heated at 350 or more and less than 900°C. A method for producing a rare earth-iron-boron alloy powder, which comprises wet-processing the resulting mixture. 3) Rare earth elements 8-17 at%, boron 3-15 at%
and an alloy powder consisting of a single-phase structure with the balance iron and unavoidable impurities, a rare earth oxide powder or the rare earth oxide powder and rare earth metal powder, and at least one selected from alkali metals, alkaline earth metals, and hydrides thereof. and,
The proportion of rare earth elements, boron and iron is rare earth elements 8 to 2
5 at% of boron, 3 to 15 at% of boron, and the balance is iron, and the mixture is first heated at 900 to 1200°C in an inert gas atmosphere or reducing atmosphere, and then heated at 350 to 900°C. A method for producing a rare earth-iron-boron alloy powder, which comprises heating the resulting mixture in a wet process.