JPH03287740A - Manufacture of raw material for rare earth permanent magnet - Google Patents

Abstract

PURPOSE:To manufacture a raw material for a rare earth permanent magnet excellent in magnetic properties at a low cost by heating and reducing a material constituted of the oxides of rare earth elements and the oxides of specified elements, thereafter washing the material, subjecting it to pulverizing, compacting and sintering and executing its componental regulation. CONSTITUTION:A material constituted of the oxides of rare earth elements R (where R denotes one or more kinds among La, Ce, Pr Nd, Sm or the like) and the oxides of elements M (where M denotes one or more kinds among Co, Fe, Ni, Mo, Cu or the like) is mixed with a reducing agent such as metallic Ca and metallic Mg, and this mixture is heated and reduced to form an RM series alloy. This RM series alloy is thereafter washed to remove CaO, MgO or the like which are reaction by-products. Next, the RM alloy is pulverized and is compacted, and this green compact is sintered in the atmosphere of an inert gas or in vacuum. After that, this sintered body is added to a molten metal constituted of R and/or M blended so as to form an RM series alloy having prescribed components including R and M in the sintered body, which is melted to manufacture an RM series alloy having prescribed components. In this way, the rare earth permanent magnet satisfactorily maintaining the magnetic properties of its own can be obtd. at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is applicable to, for example, Sva-Co or Nd-Fe-
It relates to a method for producing raw materials for rare earth permanent magnets such as B-series, and in particular, it relates to a method for producing raw materials that allows production of rare earth permanent magnets with excellent magnetic properties and is inexpensive. be.

[Conventional technology]

Since the Sm-Co-based rare earth permanent magnets were developed, their magnetic properties have gradually improved with the progress of physical property research, and these, including the Nd-Fe-B-based ones, have been applied in recent years. This has greatly contributed to the miniaturization, weight reduction, and high performance of equipment and devices used in this field, and has also contributed to the development of new fields. When producing the above-mentioned rare earth permanent magnets, powder metallurgy is usually used, and it is first necessary to produce raw material powder.

Taking the case of the most common 5sCo s type rare earth cobalt permanent magnet, first, Sa+38% by weight, Co62
The alloy consisting of % by weight is melted at high frequency in an Ar atmosphere, and the ingot obtained through casting means is coarsely pulverized, and then finely pulverized by a ball mill or the like in a protected atmosphere to produce raw material powder with an average particle size of about 5 μm. An appropriate amount of sintering aid is added to the raw material powder obtained as described above, and compression molding is performed using a mold placed in a magnetic field.
Sinter at temperatures above ℃. By subjecting the sintered body to heat treatment at 900° C. for about 1 hour or less, a rare earth permanent magnet having a high energy product can be obtained.

On the other hand, as another method for producing the raw material powder, there is a method called reduction diffusion method or R/D method. In this method, for example, after mixing SmzOs+ Co, Fe, Cu, Zr and metal Ca in a powder state,
It is heated at 0° C. for several hours to reduce and diffuse Sm2O3. In other words, taking the case of a 2-17 rare earth magnet as an example, SmzO,+Co+Fe+Cu+Zr+Ca=Sm(C
Sm(Co, Fe, Cu+ Zr)x is obtained by the reaction of 0, Fe, Cu, Zr)x+caO.

In addition, as a method of manufacturing raw material powder for rare earth permanent magnets at low cost, a rare earth metal oxide, metal M, and metal Ca are mixed, then heated and reduced to produce RM5 alloy, and this alloy is in a molten state. A proposal has been disclosed in which the above-mentioned reduction diffusion method and dissolution method are used in combination, in which M is added to metal M and then powdered (see Japanese Patent Application Laid-Open No. 60-238403). As a means of adding the above alloy, for example, SmCo5
There is a description that pellets are added to a molten Fe-Cu-Zr alloy.

[Problems to be Solved by the Invention] When producing raw material powder for rare earth permanent magnets as described above by melting and casting means, it is necessary to use a metallic rare earth element as a starting material. Since it is extremely expensive, there is a problem that the raw material powder also has to be expensive. In the case of manufacturing using the raw material powder by the above R/D method, relatively inexpensive rare earth element oxides, fluorides,
Since chloride etc. can be used, there is an advantage that the manufacturing cost of the raw material powder can be reduced.

However, on the other hand, there is a problem that the magnetic properties of the permanent magnet deteriorate. That is, there is a drawback that the reduction-diffusion reaction does not proceed completely and the composition becomes non-uniform. In addition, non-magnetic Ca added as a reduction side mixes into the alloy as an impurity. Furthermore, in 2-17 rare earth magnets, for example, this Ca may react with Cu, which should form an alloy composition, to form a Ca-Cu alloy, causing compositional fluctuations.
The disadvantage is that the behavior of a cannot be completely controlled. Furthermore, 0□ is mixed into the alloy composition. Due to the presence of the above-mentioned factors, there is a problem in that the magnetic properties required for a permanent magnet are degraded.

In addition, in the above proposal using both the reduction diffusion method and the dissolution method, S
When mCo is added as a pellet simply formed from a powder, it is not only easily oxidized by the high-4 molten metal, but also because the pellet is porous and contains 0□. , O6 may also be mixed in.

Therefore, there is a concern that the dissolution yield will be significantly lowered and the magnetic properties will be lowered, and there is a problem that it is difficult to satisfy the requirement of reducing the manufacturing cost of the raw material powder while maintaining the magnetic properties.

The present invention solves the problems existing in the above-mentioned prior art, and produces raw material powder for rare earth permanent magnets that sufficiently retains the magnetic properties inherent to rare earth permanent magnets and can significantly reduce manufacturing costs. The purpose is to provide a method.

[Means for Solving the Problems] In order to achieve the above object, the present inventors have developed a rare earth element R and its oxide or an oxide of the rare earth element R (R is La,
Ce, Pr, Nd, Sm, Gd, Tb,
Dy, H.

one or more of Er) and element M and its oxide or oxide of element M (M is Co, FeNi,
Mo, Cu, Zr, Hf, Nb, Ta,
(Ti, Al, Ga, BSi, C) and metal Ca, CaHz
, after adding and mixing the reducing side such as metal-g, heat and reduce to R.
An M-based alloy is produced, and this RM-based alloy is washed with water to produce Cab, which is a reaction by-product.

After removing MgO, etc., it is pulverized, molded into a molded body, and the molded body is sintered in an inert gas atmosphere, a reducing gas atmosphere, or in a substantial vacuum to form a sintered body. A technical method of manufacturing an RM alloy by adding the sintered body to a molten metal consisting of R and/or M blended to form an RM alloy with a predetermined composition including R and M in this sintered body and melting it. adopted the means. In the present invention described above, metal Ca is added to the material containing the oxide of rare earth element and the oxide of M element.
.

CaFI2. A reducing agent such as metallic Mg is added and mixed, and this is heated and reduced to produce an RM alloy. At this time, since the reduction reaction between the rare earth element oxide and the M element oxide by these reducing agents is accompanied by heat generation, there is an advantage that the formation of the RM alloy by diffusion of the elements after the reduction reaction is promoted.

Next, this RM alloy is washed with water, but in this process, most of the 02 contained in the material is converted to CaO or Mg.
removed in the form of The amount of reducing agent added is 0
It is sufficient to add a sufficient amount (equivalent stoichiometric amount) to reduce the is added in an amount of 1.1 to 2.5 times the stoichiometric amount by weight. 2.5
Addition of more than twice the weight is not preferable because the cost of the reducing agent increases and the amount of reducing agent remaining in the RM alloy after washing with water increases. The thermal reduction treatment is performed in an inert gas atmosphere such as argon gas, a reducing gas atmosphere such as hydrogen gas, or in a substantial vacuum. Although the heating temperature varies slightly depending on the composition of the material, a temperature in the range of 900 to 1200°C is usually selected.

In the present invention, the obtained RM gold alloy is then crushed, molded and sintered, and the sintered body is added to the molten metal to achieve a predetermined R.
M-gold alloy. The compact is sintered in an inert gas atmosphere such as argon gas, a reducing gas atmosphere such as hydrogen gas, or in a substantial vacuum. The sintering temperature varies depending on the composition of the compact, but a temperature in the range of 950 to 1250°C is selected. For melting, for example, a predetermined amount of material is charged into a vacuum induction melting furnace, then the melting furnace is sealed, the inside of the furnace is maintained in a vacuum state, and electricity is applied to melt the material and form molten metal. This is carried out by adding a predetermined amount of the RMM gold sintered body previously prepared in the melting furnace. After the sintered body is dissolved in the molten metal, the molten metal is cast into a mold.

The RM gold alloy ingot having a predetermined composition obtained in this way can be used, for example, as a raw material for sintered permanent magnets by pulverizing it, or for example, by remelting it and rapidly solidifying it in a molten state to produce the same raw material for permanent magnets. It can be used depending on the purpose.

[For production]

With the above configuration, 0□ contained in the material is first reduced by the reducing agent, and most of it is removed in the form of CaO, us41gO, during washing with water. Next, the obtained RM gold alloy undergoes the steps of crushing, molding, and sintering, and is added as a sintered body to a molten metal consisting of R and/or M and melted to obtain a predetermined RM-based alloy molten metal. In this case, residual CaOMgO, etc. contained as impurities floats up as slag, and the RM
Ca, Mg, and 0□ do not enter the molten M alloy. Further, since the surface oxidized layer present on the outer shell of the sintered body also takes on a shell shape and floats together with the slag, undesired intrusion of O2 can be prevented.

(Example)-1 NdzO: + 3500g, DytOx 575g
, Fe powder 5650 g.

FezO=500g powder, FezO7 powder (B=2
0%) and 2357 g of metallic Ca were mixed and subjected to heat reduction treatment at 1100° C. for 2 hours in an argon gas atmosphere. Next, the obtained reaction product was washed with water to remove CaO, which is a reaction by-product, and Nd-Dy-Fe-
B alloy was obtained. Analysis of the composition of the obtained Nd-Dy-Fe-B alloy revealed that the weight percentage was 30.0% Nd, py5
．． o%, B140%, CaO, 12%, o, o, 2%,
The remainder was Fe.

This alloy was made into powder with an average particle size of 10 μm using a jet mill, and this powder was molded at a molding pressure of 1.5 ton/cIIl to form a compact. Further, the molded body was sintered in an argon gas atmosphere at 1120° C. for 3 hours to obtain a sintered body.

On the other hand, Nd metal 196 is used as a raw material in the vacuum induction melting furnace.
0 g, Fe 3786 g, ferroboron (B=20
%) 360 g, ferroniobium (Nb = 80%) 9
A total of 3,800 g of the sintered body was added to the molten metal, and the sintered body was sequentially added thereto, melted, and cast into a mold to obtain an ingot. The composition of the obtained ingot was analyzed and found to be 31.0% Nd by weight.

Dy 1.9%, B1.1%, Nb0.75%, Ca<
0.01%.

Ot<0.01%, the balance being Fe.

This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. The results of measuring the magnetic properties are shown in the table. In addition, as a comparative example, one using a raw material produced by the conventional R/D method is also shown.

As is clear from the table, in the comparative example, Br.

! The IHcO value is low, and the value of (BH)□8 is decreased.

On the other hand, in the example, the Br + IIHcO value is large, and the (BH) and □ values are large, and these values are due to the raw materials prepared by melting Nd metal and Dy metal. It is.

(Example)-2 Dy2036200 g, Fe powder 4000 g,
858 g of Pet's flour.

3570 g of metallic Ca was mixed and subjected to heating reduction treatment at 1050° C. for 3 hours in an argon gas atmosphere. Next, the reaction product obtained was washed with water, and the reaction by-product Ca
O was removed to obtain a Dy-Fe alloy. The obtained Dy-
When the composition of the Fe alloy was analyzed, it was Dy54.0 in weight%.
%, CaO, 09%, ozo, 13%, and the balance was Fe.

This alloy was made into powder with an average particle size of 20 μm using a jet mill, and this powder was molded at a molding pressure of 3.0 tons/− to form a compact. Furthermore, the molded body is heated to 1080°C in a substantial vacuum.
It was sintered under the conditions of x1 hour to obtain a sintered body.

On the other hand, 3010 g of Nd metal was placed as raw material in the vacuum induction furnace.
, Ferroboron (B=20%) 600 g, F
A total of 648 g of the above-mentioned sintered body was sequentially added to the molten metal, melted, and cast into a mold to obtain an ingot. Analysis of the composition of the obtained ingot revealed that Nd was 30.1% by weight.
, Dy3.5%, B1.2%, Ca<0.01%0□<
The balance was 0.01% Fe.

This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. The results of measuring the magnetic properties are shown in the table. In addition, as a comparative example, one using a raw material produced by the conventional R/D method is also shown.

As is clear from the table, in the comparative example, Br.

The value of ml(C is low, and the value of (Bll), . . . is decreasing.

On the other hand, in the example, the Br + JcO value is large, and the (BH) and □ values are large, and these values are due to the raw materials made by melting Nd metal and Dy metal. It is.

(Example)-3 DyzOz 5798 g, Co powder 4700 g
, 211 g of CozO3 powder.

143 g of Fe, 03 powder, and 2663 g of metallic Ca were mixed and subjected to heat reduction treatment at 1100° C. for 5 hours in an argon gas atmosphere. Next, the obtained reaction product was washed with water to remove CaO, which is a reaction by-product, and Dy-Co-
An Fe alloy was obtained. When the composition of the obtained Dy-Co-Fe alloy was analyzed, it was found that oy was 50.5% and Fe was 1.5% by weight.
0%, CaO, 1%, ozo, 12%, and the balance was Co.

This alloy was made into powder with an average particle size of 5 μm using a jet mill,
Add this powder to 1. A molded article was obtained by molding at a molding pressure of Oton/-. Further, the molded body was placed in an argon gas atmosphere for 11 days.
A sintered body was obtained by sintering at 00°C for 2 hours.

Meanwhile, 2980g of Nd metal was placed in the vacuum induction furnace as a raw material.
, Co metal 2g, ferroboron (B=20%) 65
0 g and 5774 g of Fe were charged and melted to form a molten metal, to which a total of 594 g of the sintered body was successively added and melted, and cast into a mold to obtain an ingot.

Analysis of the composition of the obtained ingot revealed that it was N by weight%.
d 29.8%, oy3. o%, Co2.9%.

81.3%, Ca<0.01%, Ot<0.01%, and the balance was Fe.

This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. The results of measuring the magnetic properties are shown in the table. In addition, as a comparative example, one using a raw material produced by the conventional R/D method is also shown.

As is clear from the table, in the comparative example, Br.

The value of s+)[c is low, and the value of (Bl()□8) is low.

On the other hand, in the example, the values of Br, , H, and (Bl().π) are large, and these values are different from those of the raw materials prepared by melting Nd metal and Dy metal. It depends on the time and time.

(Example)-4 SLllgoz 5220g, Co powder 4554g,
600 g of Coxes flour.

Fe powder 450g, Pe203100g, metal Ca
2884g was mixed and heated to 1150℃ in an argon gas atmosphere.
A heating reduction treatment was performed for 4 hours. Next, the obtained reaction product was washed with water to remove CaO, a reaction by-product, to obtain an Ss-Co-Fe alloy. Obtained Ss −
Analysis of the composition of the Co-Fe alloy revealed that Sm in weight%
45.0%, Fe5.2%, Ca0.1%, o, 0.
The balance was Co.

This alloy was made into powder with an average particle size of 4 μm using a jet mill,
This powder was molded at a molding pressure of 2.0 ton/- to form a molded body. Further, the molded body was heated to 1140°C in a hydrogen gas atmosphere.
A sintered body was obtained by sintering at ℃×3 hours.

Meanwhile, 2520g of Ss metal was placed as raw material in the vacuum induction furnace.
, Co metal 7671g, Fe 2B09g, Cu
470 g of Zr and 230 g of Zr were charged, and these were melted to form a molten metal, and the above-mentioned sintered body was added to this to a total of 5,600 g.
g was sequentially added, melted, and cast into a mold to obtain an ingot. Analysis of the composition of the obtained ingot revealed that it contained So+ 25.2%, Fe 15.5%, and Cu 4.7% by weight.
%, Zr2.3%.

Ca<0.01%, 02<0.01%, and the balance was Co.

This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. The results of measuring the magnetic properties are shown in the table. In addition, as a comparative example, one using a raw material produced by the conventional R/D method is also shown.

As is clear from the table, in the comparative example, Br.

The value of 11HC is low, and the values of (BH) and □ are decreased.

On the other hand, in the example, the Br+ 1HeO value is large, and the value of (Bl(),...) is large, and these values are due to the raw material made by melting 100% Sm metal. − is.

(Example)-5 When a SmCo alloy for permanent magnet material was melted by the melting method, the substance that floated to the surface of the molten metal and remained in the crucible after pouring the molten metal was collected and analyzed, and it was found to be 5LII.

It was found that SmzOz+Co, C0103 was the main component.

The recovered residue was coarsely pulverized and the amount of 0□ contained therein was measured, and the weight ratio was 6% (60,000 ppm).

10,000 g of this coarse powder contains granular metal Ca 1954
Add and mix g and heat at 1050°C x 4 in an argon gas atmosphere.
A heating reduction treatment was performed for several hours. Next, the obtained reaction product was washed with water to remove CaO, a reaction by-product, and Sm
-Co alloy was obtained. This S11! Analysis of the composition of the -Co alloy revealed that the weight ratio was S+m 67.8%, Ca
O, 15%.

0□0.2%, the balance being Co. This Sm-Co alloy was pulverized with a jet mill to obtain a powder with an average particle size of 8 μm.

This powder was then subjected to cold isostatic pressing in 3. Oton
Molding was performed at a molding pressure of /cd. Further, the molded body was sintered in an argon gas atmosphere at 1100° C. for 3 hours to obtain a sintered body.

Meanwhile, 4162g of Go was placed in the vacuum induction melting furnace as a raw material.
, Fe 1400g+Cu 500g, Zr
After charging 250g, the melting furnace was sealed and the inside of the furnace was heated to 100g.
-'Torr vacuum state was maintained and electricity was applied to melt these raw materials to form a molten metal. Next, after filling Ar gas and maintaining the inside of the melting furnace at -30 cmHg, a total of 3688 g of the above-mentioned S+m-Co alloy sintered body prepared in the melting furnace was added to the 1174th molten metal. did. After adding the sintered body, the sintered body was further melted by applying electricity, and then the electricity was stopped and the molten alloy was cast into a mold to obtain an ingot. Analysis of the composition of the obtained ingot revealed that the weight ratio was Sa+ 25.0%, Fe13.
9%, Cu4.9%, Zr2.5%, Ca<0.01%
, 0□<0.01%, the balance being Co.

This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. The results of measuring the magnetic properties are shown in the table. In addition, as a comparative example, one using a raw material produced by the conventional R/D method is also shown.

As is clear from the table, in the comparative example, Br.

The value of lHc+ +Hc is low, and the value of (B)I), , x is decreased. On the other hand, in the embodiment, Br+
The JcO value is large, and the values of (BH), . It has been confirmed that the manufacturing cost of the raw material can be reduced by 20 to 30% compared to the case of the above-mentioned melted raw material.

(Example)-6 When so-called scrap such as defective chips or defective dimensions of S-Cott type permanent magnets is melted by the melting method, the substances that float to the surface of the molten metal and remain in the crucible after the molten metal is poured are recovered. When analyzed, Sva.

5ltOz+ Co, CozOa+ Fe+ Pez
O3+ Cut Cub, Zr.

It was found that ZrO□ was the main component. The recovered residue was coarsely pulverized and the amount of 02 contained therein was measured, and the weight ratio was 5% (50,000 ppm). This coarse powder 1
0,000 g and 1,879 g of granular metal Ca were added and mixed, and heat reduction treatment was performed at 1,150° C. for 2 hours in an argon gas atmosphere. Next, the obtained reaction product is washed with water to remove CaO, which is a reaction by-product, to form So+ -C.

-Fe-Cu-Zr alloy was obtained. Obtained Ss −
Analysis of the composition of the Co-Fe-Cu-Zr alloy revealed that the weight percentage was 5rR30.2%, Fe13.4%, Cu
4.8%, Zr2.4%, CaOolO%, 020.
15%, the balance being Co.

This alloy was made into a powder having an average particle size of 5.0 μm in the same manner as in Example 1, and this powder was molded at a molding pressure of 2.0 ton/− to form a compact. Further, the molded body was sintered in an H2 gas atmosphere at 1200° C. for 2 hours to obtain a sintered body.

Meanwhile, Sm metal 2520 is used as raw material in vacuum induction melting.
g, Co 5813 g, Pa 24B2 g,
Example 1: 600 g of Cu and 240 g of Zr were charged.
These were melted in the same manner as above to form a molten metal, and a total of 8345 g of the sintered body was sequentially added to this and melted.
An ingot was obtained by casting into a mold. Analysis of the composition of the obtained ingot revealed that Sm was 25.2% and F was 25.2% by weight.
e17.9%.

Cu5.0%, Zr2.1%, Ca<0.01%, 02
<0.01%, the balance being Co.

This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. The results of measuring the magnetic properties are shown in the table. In addition, as a comparative example, one using a raw material produced by the conventional R/D method is also shown.

As is clear from the table, in the comparative example, Brflo
e, IHC value is low, and (B)I)□, value is decreased. On the other hand, in the example, Br, g)l
The value of c is large, and the value of (B)l)□9 is large, and these values are due to the raw material prepared by melting Sm metal and time.

(Example)-7 Analysis of the substances that floated to the surface of the molten metal and remained in the crucible after pouring the molten metal when melting an alloy for Nd-Fe-B permanent magnet materials by the melting method revealed that NdNd2O3,D
y+ Dyz03+ Fe, FezO3,B, Bz
It was found that Oi was the main component.

This residue was roughly pulverized and the amount of 02 contained therein was measured, and the weight ratio was 7% (70,000 ppa+). After mixing 2192 g of granular metal Ca with 10000 g of this coarse powder, heat reduction treatment was performed at 1100°C for 2 hours in the same manner as in Example 1, and the obtained reaction product was washed with water to form an Nd-Fe-B system. An alloy of Analysis of the composition of the obtained alloy revealed that Nd was 49.8% and Dy was 2.5% by weight.
%, 81.2%, CaO, 08%, O12, 25%, and the balance was Fe. This alloy was made into powder with an average particle size of 15 μm in the same manner as in Example 1, and this powder was
A molded article was obtained by molding at a molding pressure of n/-. Further, the molded body was sintered in a substantial vacuum at 1130° C. for 1 hour to obtain a sintered body.

Meanwhile, Nd metal 1550 is used as raw material in vacuum induction melting.
g, hMetal 145g, Fe 5917g, C
o 300g.

ati 150g, ferroboron 525g (820%)
.

188 g of ferroniobium (Nb 80%) was charged and melted in the same manner as in Example 1 to form a molten metal.To this, a total of 6225 g of the sintered bodies were successively added, melted, and placed in the mold. I got an ingot by casting. Analysis of the composition of the obtained ingot revealed that Nd was 30.9% by weight;
DV2.0%, Co2.0%, At'1.0%B1.2
%, Nb1.0%, Ca<0.01%, 02<0.01
%, the balance being Fe.

This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. The results of measuring the magnetic properties are shown in the table. In addition, as a comparative example, one using a raw material produced by the conventional R/D method is also shown.

As is clear from the table, in the comparative example, Br.

The value of 11HC is low, and the values of (BH), . . . are decreasing.

On the other hand, in the example, the value of Br + Jc is large, and the values of (BH) and □ are large, and these values are due to the raw materials made by melting Nd metal and Dy metal. − is.

(Example) -8 Nd, NdzO*, and DV were analyzed when Nd-Fe-B system was remelted by so-called scraps such as permanent magnets with defective chips and dimensional defects, and by a melting method.

Dy2O3, Pr, Pr6O11, Ce, Ce0z
, B, B2O3, and FeFe20s were found to be the main components. This residue was coarsely pulverized and the amount of 02 contained was measured, and the weight ratio was 6.5% (65,000pp).
m). Add granular metal C to 10,000 g of this coarse powder.
2931 g of a was added and mixed, and heat reduction treatment was performed at 1020° C. for 5 hours in an argon gas atmosphere. Next, the obtained reaction product was washed with water and the reaction by-product CaO
After removal, a Nd-Fe-B alloy was obtained. Analysis of the composition of the obtained alloy revealed that Nd was 22.1% and D was 22.1% by weight.
y1.2%, Pr7.5%Ce3.0%, B1.0%,
CaO, 1%, 020.3%, balance Fe.

This alloy was made into powder with an average particle size of 15 μm in the same manner as in Example 1. A molded article was obtained by molding at a molding pressure of Oton/-. Further, the molded body was placed in a substantial vacuum for 10
A sintered body was obtained by sintering at 70° C. for 3 hours.

Meanwhile, Nd metal 2000 is used as raw material in vacuum induction melting.
g, Dy metal 291g, Pr metal 721g,
Ce metal 428g, B 120g, Fe7390
g and melted them in the same manner as in Example 1 to form a molten metal, and to this, a total of 9050 g of the sintered body was added.
Analysis of the composition of the ingot obtained by adding it sequentially, melting it, and casting it into a mold revealed that Nd1 was added in weight%.
9.9%, Pr6.8%, Ce3.5%, Dy2.0%
, B1.0%Ca<0.01%, (h<0.01%, balance Fe.

This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. The results of measuring the magnetic properties are shown in the table. In addition, as a comparative example, one using a raw material produced by the conventional R/D method is also shown.

As is clear from the table, in the comparative example, Br.

1tlco 1ncO value is low, and (BH) and □ values are decreased. On the other hand, in the embodiment, Br+
The IHcO value is large, and the values of (BH), , are large, and these values are the same for Nd metal, Pr metal, C
These are materials made by melting e-metal and Dy-metal, and time.

〔Effect of the invention〕

Since the present invention has the structure and operation as described above,
The following effects can be achieved.

(1) By reducing the material containing the oxide of the rare earth element R with a reducing agent and adding it to the molten metal in the form of a sintered body to produce the RM alloy, the RM gold alloy can contain all the necessary rare earth elements. Alternatively, a part can be procured from rare earth elements containing oxides, and the manufacturing cost of the RM alloy can be significantly reduced.

(2) Because heat is generated when reducing a material containing an oxide of rare earth element R and an oxide of M element, R due to diffusion
The formation of M-based alloys is promoted.

(3) Even if the reduction and diffusion of the RM alloy obtained by the reduction and diffusion treatment is somewhat insufficient, the composition can be made uniform by the subsequent sintering and melting means.

(4) Metals Ca, CaHl, metal Mg for reduction treatment, and reaction by-products CaO and MgO float as slag during the melting process, so they do not mix into the RM alloy.

(5) Present in the starting material. 2 is also absorbed and removed by the slag in the melting process, thereby preventing it from penetrating into the RM alloy.

(6) From the above, in order to ensure a uniform composition of the RM alloy and prevent the intrusion of impurities made of non-magnetic materials,
The magnetic properties of rare earth permanent magnets can be improved to the same level as those made from 100% molten material.

Claims (1)

[Claims] Rare earth element R and its oxide or oxide of rare earth element R (R is La, Ce, Pr, Nd, Sm, Gd, Td
, Dy, Ho, Er) and
Element M and its oxide or oxide of element M (M is Co
, Fe, Ni, Mo, Cu, Zr, Hf, Nb, Ta,
One or two of Ti, Al, Ga, B, Si, and C
metal Ca, CaH_2, metal M
After adding and mixing a reducing agent such as g, heat reduction is performed to produce an RM-based alloy, this RM-based alloy is washed with water to remove reaction by-products such as CaO, MgO, etc., and then pulverized and molded. The molded body is sintered in an inert gas atmosphere, a reducing gas atmosphere, or a substantial vacuum to form a sintered body, and this sintered body is sintered, including R and M in this sintered body. R and/or M blended to form an RM alloy with predetermined components.
A method for producing a raw material for rare earth permanent magnets, which comprises adding and melting into a molten metal to produce an RM-based alloy.