JPH03277733A - Manufacture of raw material for rare earth permanent magnet - Google Patents

Abstract

PURPOSE:To manufacture the raw material for a rare earth permanent magnet contg. Dy and excellent in magnetic properties at low cost by manufacturing a Dy-Fe alloy by the use of Dy2O3, Fe and metallic Ca as a raw material, pulverizing this alloy, thereafter compacting and sintering it, successively adding the alloy to a molten metal contg. rare earth elements and other specified elements, melting it and executing solidification. CONSTITUTION:The powder of Dy2O3 and Fe is mixed with metallic Ca as a reducing agent, and this mixture is heated in an Ar atmosphere to reduce Dy2O3 by Ca and to manufacture a Dy-Fe series alloy. This alloy is finely pulverized and is thereafter compacted, and the obtd. green compact is sintered in the atmosphere of an inert gas or a reducing gas or in vacuum. On the other hand, the molten metal of an alloy in which one or more kinds among Sc, Y and lanthanoide series elements and other specified elements are melted by an other apparatus is mixed with the above sintered body, and the mixture is heated and melted. The raw material for a rare earth permanent magnet contg. no CaO as a reducing product and excellent in magnetic properties such as coercive force, residual magnetic flux density and maximum energy product can be manufactured at a low cost.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a raw material for a rare earth permanent magnet containing, for example, Dy as a rare earth element.
In particular, the present invention relates to a raw material manufacturing method that allows production of rare earth permanent magnets with excellent magnetic properties and is inexpensive.

[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. In order to manufacture the above-mentioned rare earth permanent magnet, powder metallurgy is usually used, and it is first necessary to manufacture raw material powder. Of these, Nd- contains Dy, which has attracted particular attention in recent years.
Taking the case of Fe-B system as an example, first of all Nd29 in weight%
%, Dy 3.6%, 81%, Nb 11%, balance Fe is radio-frequency melted in an Ar atmosphere, coarsely pulverized, and further finely pulverized with a ball mill etc. in a protected atmosphere to obtain a raw material powder with an average particle size of about 4 μm. Create. An appropriate amount of sintering aid is added to the raw material powder obtained as described above, compression molded using a mold placed in a magnetic field, and this molded body is sintered at 1000"C or higher. By performing heat treatment at 900° C. for about 1 hour, a rare earth permanent magnet having a high energy product can be obtained.

[Problem to be solved by the invention]

When producing raw materials for rare earth permanent magnets as described above by melting and casting means, it is necessary to use Dy metal or Dy-Fe alloy as the starting material.
Since Dy metal and Dy-Fe alloy are extremely expensive, there is a problem in that the raw materials must also be expensive.

Demands from the field of application of rare earth permanent magnets are becoming increasingly strict, including miniaturization, weight reduction, high performance, and cost reduction.

On the other hand, as a method for producing the above raw materials, reduction diffusion method or R/
There is a method called D method. In this method, for example, D V 20s+pe+ ferroboron and metal Ca
After mixing in a pulverized state, the mixture is heated at 950 to 1200°C for several hours to reduce and diffuse Dy, O, and the like. That is, CaO is removed from the mixture produced by the reaction Dy, Os+14Fe+B+3Ca→Dy, Fe, 4+B+3Ca○, and then dried to obtain a Dy-Fe alloy.

In this method, relatively inexpensive yxOs can be used in place of the expensive y-Fe alloy, so there is an advantage that the manufacturing cost of raw materials can be reduced.

However, when the permanent magnet is produced using raw materials produced by the R/D method, there is a problem in that the magnetic properties of the permanent magnet deteriorate. That is, first of all, there is a drawback that the reduction-diffusion reaction does not proceed completely and, for example, the Fe core constituting the alloy remains, resulting in a uniform composition. Furthermore, non-magnetic Ca added as a reducing agent mixes into the alloy as an impurity. Furthermore, 02 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.

As a method for manufacturing the raw material for rare earth permanent magnets at low cost, a rare earth metal oxide, metal M, and metal Ca are mixed, and then heated and reduced to produce an RM5 alloy. A proposal has been disclosed in which the powder is powdered after being added thereto (see Japanese Patent Application Laid-Open No. 60-238403).

As a method for adding the above-mentioned alloy, for example, there is a description that RM5 alloy is added to the molten metal in the form of pellets.

It is conceivable to apply this method to Dy-Fe alloys, but if RM5 alloy or Dy-Fe alloy is added as a pellet simply formed from a powder state, this pellet is a porous body. Since it contains O2 and O2, it is not only easily oxidized by high-temperature molten metal, but also causes O2 to be mixed in. Therefore, there is a concern that the melting yield will decrease significantly and the magnetic properties will deteriorate.
Another problem is that it is difficult to satisfy the requirement of reducing the manufacturing cost of raw materials while maintaining magnetic properties.

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

[Means to solve the problem]

In order to achieve the above object, in the present invention, Dy2
0. After mixing , Fe, and gold@iCa, a Dy-Fe alloy is produced by heating reduction, and this product is crushed to produce a molded body, which is heated in an inert gas atmosphere and a reducing gas. A sintered body is obtained by sintering in an atmosphere or in a substantial vacuum, and this sintered body is made of RM containing a predetermined component including Dy and Fe (where R is Sc, YO, La, Ce, P
r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, H.

, Er, Pm, Tb, one or more of Lu, M is Go, Fe, Ni, Mo, Cu, Zr, Tl,
Hf, Nb, Ta, V, W, Al, C,
Ge, Ir, Mg, M, Ge, Se, S
i, Te.

Adopts technical means of manufacturing RMM alloy by adding it to a molten metal consisting of R and/or M blended to form an alloy of one or more of Z, Ge, and B) and melting it. did.

In the present invention, Dy- obtained by thermal reduction treatment
If the Fe alloy is melted as it is, the RM gold alloy melting yield will be significantly lowered and the manufacturing cost of the raw material will be increased, which is disadvantageous.

Therefore, it is necessary to crush, mold, and further form a sintered body before melting it.

[For production]

With the above configuration, a sintered body made of a Dy-Fe alloy is added to a molten metal made of R and/or M and melted, thereby obtaining a predetermined RM-based alloy molten metal.

In this case, CaO contained as an impurity floats up as slag, preventing (:a, O, from penetrating into the molten RM base metal. Also, the surface oxidation layer present on the outer shell of the sintered body also Since it takes on a shell-like appearance and floats up with the slag, undesirable zero
2 can be prevented from entering.

[Example-1] Dy, 0. 5738g Fe 5000g Metallic Ca 185c1g After mixing the above starting materials, a heating reduction treatment was performed at 1200° C. for 2 hours in an Ar gas atmosphere in a stainless steel retort. Next, the obtained reaction product was washed with water to remove CaO, a reaction by-product, to obtain a Dy-Fe alloy. Analysis of the composition of the obtained Dy-Fe alloy revealed that the weight percentage was DV49.8%, Ca0O,1%, 0.0.
2%.

The remainder was Fe. The Dy-Fe alloy was pulverized with a jet mill to obtain a powder with an average particle size of 10 μm. The second powder was molded using a cold isostatic press at a molding pressure of 2.5 t/cm2. Furthermore, the molded body was heated to 105% in an argon gas atmosphere.
It was sintered at 0° C. for 2 hours to obtain a sintered body. Meanwhile, Nd metal 294C)g as raw material in the vacuum induction melting furnace,
Fe5699g, ferroboron 500g (B 20
．． 0%).

Charge 138g of ferroniobium (Nb80.0%),
Next, the melting furnace was sealed, the inside of the furnace was kept in a vacuum state of 1 O-ITorr, and electricity was applied to melt these raw materials to form a molten metal. Next, the inside of the melting furnace was filled with Ar gas.
After maintaining the state at 0 cmHg, the Dy-Fe base metal sintered body prepared in advance in the melting furnace was heated to a total of 72 mmHg.
3g was added sequentially to the molten metal. 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. When the composition of the obtained shot was analyzed, it was found that Nd was 29.4% by weight.
%, Dy3.6%, 81%, Nb11%, Ca<0.
0.01%, O<0.01%, and the balance was Fe. This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. Displays the results of measuring magnetic properties. 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 Br BHc IHc (BH) max table, in the comparative example, the values of Br and BHc are low, although they show slightly larger values in IHC, and (B
H) The value of max is decreasing. On the other hand, in the example, the values of Br and BHc are large, and (BH)
The value of max is large, and these values are indistinguishable from those due to the raw material produced by melting Dy metal. It has been confirmed that the manufacturing cost of the raw material can be reduced by 2 to 0% compared to the case of the above-mentioned melted raw material.

[Example-2] Dyxo, 6886g Fe 4000g Metal Ca 2220g After mixing the above starting materials, 11
A heating reduction treatment was performed at 50°C for 2 hours, and the resulting reaction product was washed with water to obtain a Dy-Fe alloy. The obtained Dy-
When the composition of the Fe alloy was analyzed, it was Dy59.8 in weight%.
%, Cab, 0.8%, 0.0.25%, balance Fe. This Dy-Fe alloy was made into powder with an average particle size of 5 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 cm2. Further, the molded body was sintered in a substantial vacuum at 1100° C. for 1 hour to obtain a sintered body.

On the other hand, Nd metal 3 was placed as a raw material in the vacuum induction melting furnace.
110g, Fe5556g, Go300g, A180g
, 525 g of ferroboron (20% B) and 94 g of ferroniobium (80% Nb) were charged and melted in the same manner as in Example 1 to form a molten metal, to which a total of 335 g of the above sintered body was sequentially added. The mixture was melted and cast into a mold to obtain an ingot. When the composition of the obtained ingot was analyzed, the weight percentage was 31.1% Nd and 2.0% D5y.
.

Ga4.0%, AIo, 8%, B1.05%, Nbo,
75%, Ca<0.01%, 02<0.01%, balance Fe. This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. Displays the results of measuring magnetic properties. 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, BHc
The value of is low, and the value of (BH)max is decreasing. On the other hand, in the example, the values of Br and BHC are large, and the value of (BH)max is large, and these values are different from those from the raw material made by melting Dy metal and from the road. be.

[Example-3] D'lx0. 3443g Fe 7000g Metal Cal 199g After mixing the above starting materials, 11
A heating reduction treatment was performed at 50° C. for 2 hours, and the resulting reaction product was washed with water to obtain a Dy-Fe alloy. The obtained Dy-
When the composition of the Fe alloy was analyzed, it was Dy29.7 in weight%.
%, Cab, 0.6%, O, 0.18%, and the balance was Fe. In addition, the same y-Fe alloy was made into powder with an average particle size of 20 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/cm2. Further, the molded body was sintered in an argon gas atmosphere at 1100°C for 1 hour to obtain a sintered body.

On the other hand, NdPr-F was placed as a raw material in a vacuum induction melting furnace.
e metal (71.4% Nd, 238% Pr, balance Fe)
, Fe5185g, Ferrophoron 600g (B20
%) and 65 g of ferroniobium (Nb 80%) were charged and melted in the same manner as in Example 1 to form a molten metal.To this, a total of looog of the above-mentioned sintered bodies were sequentially added and melted. , and cast into a mold to obtain an ingot. Analysis of the composition of the obtained ingot revealed that it was Nd22.
5%, Dy3.0%, B1.2%, Nb0.52%,
Ca<0.01%, 02<0.01%, and the balance was Fe. This alloy was coarsely pulverized, finely pulverized, molded, sintered, and heat treated to form a permanent magnet. Displays the results of measuring magnetic properties. 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, BHc
The value of (BH)Illax is low, and the value of (BH)Illax is decreasing. On the other hand, in the example, the values of Br and BHC are large, and the value of (BH)max is large, and these values are different from those from the raw material made by melting Dy metal and from the road. be.

[Example-4] Dy, 0. 2295g Fe 8000g Metal Ca 888g After mixing the above starting materials, 11
A heating reduction treatment was performed at 70°C for 2 hours, and the resulting reaction product was washed with water to obtain a Dy-Fe alloy. The obtained Dy-
When the composition of the Fe alloy was analyzed, it was Dy19.8 in weight%.
%, Cab, 0.5%, O, 0.15%, and the balance was Fe. This DyFe alloy was made into powder with an average particle size of 4 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 /cm2. Further, the molded body was sintered in a hydrogen atmosphere at 1000°C for 1 hour to obtain a sintered body.

On the other hand, NdPr-C was used as a raw material in a vacuum induction melting furnace.
e-Fe metal (Nd62.7%, Pr21.8%, C
e10.5%, balance Fe) 3263g, Fe5212g
, 525 g of ferroboron (B20%) was charged, and these were melted in the same manner as in Example 1 to form a molten metal, and a total of looog of the sintered bodies were sequentially added to this and melted,
An ingot was obtained by casting into a mold. The composition of the obtained ingot was analyzed and found to be Nd2O in weight percent.

5%, Pr7.1%, Ce3.4%, Dy2.0%,
Bl, 05%, balance Fe. Coarsely crush this alloy,
It was pulverized, molded, sintered, and heat treated to form a permanent magnet.

Displays the results of measuring magnetic properties. 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, BHc
The O value is low and the (BH)max value is decreasing. On the other hand, in the example, the values of Br and BHC are large, and the value of (BH)max is also large, and these values are different from those from the raw material made by melting Dy metal. be.

In this example, an example in which the rare earth element is DV has been described, but other rare earth elements other than Dy (see R above)
However, the effect is the same. Similarly, the present invention can be similarly applied even when part of Fe is replaced with the other metal M. Note that the shape of the sintered body added to the molten metal is not particularly limited. Of course, the forming means other than cold isostatic pressing can also be applied. Further, as the powdering means, atomizing means from a molten state may be used.

〔Effect of the invention〕

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

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

(2) Metallic Ca for reduction treatment or reaction by-product C
Since it floats as aO slag, there is no chance of contamination with RM-based alloys.

(3) 02 present in the starting material is also absorbed and removed by the slag during the melting process, thereby preventing it from entering the RM alloy.

(4) 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 molten materials.

(5) By pulverizing and molding the alloy obtained by reduction diffusion treatment and making it into a sintered body, there is less loss in the melting process and the melting yield can be greatly improved, reducing the manufacturing cost of raw materials. A significant reduction is possible.

Claims (1)

[Claims] After mixing Dy_2O_3, Fe, and metal Ca, a Dy-Fe alloy is produced by heating reduction, and this product is crushed and formed into a compact, which is placed in an inert gas atmosphere, a reducing gas atmosphere, or The sintered body is sintered in a substantial vacuum to form a sintered body, and the sintered body is made up of predetermined components of R-M including Dy and Fe (where R is Sc, Y, La, Ce
, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy,
One or more of Ho, Er, Pm, Tb, Lu, M is Co, Fe, Ni, Mo, Cu, Zr, Tl
, Hf, Nb, Ta, V, W, Al, C, Ge, Ir,
One or more of Mg, Mn, Se, Si, Te, Z, Ge, B) system alloy is added and melted into a molten metal consisting of R and/or M, and RM
A method for producing rare earth permanent magnet raw materials, the method comprising producing a rare earth permanent magnet raw material.