JP2954816B2 - Method for producing sintered R-Fe-B magnet by injection molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a method for producing an Fe-B based sintered anisotropic permanent magnet, in which a resin is coated on the surface of finely crystallized R-Fe-B based alloy fine powder, and then a sol-gel reaction is caused at a predetermined temperature. By injection molding without kneaded material of methyl cellulose and / or agar and water as a binder, and by sintering after debinding, the residual carbon and oxygen in the sintered body are suppressed, and deterioration of magnetic properties is prevented, The present invention relates to a method for producing an R—Fe—B based sintered magnet by an injection molding method that improves moldability during injection molding and provides a sintered magnet having a three-dimensionally complicated shape.

[0002]

2. Description of the Related Art Today, small motors and actuators used for home appliances, computer peripherals, automobiles, and other applications are required to be compact, lightweight, and high-performance. There is a demand for a three-dimensionally complex shaped product, such as providing irregularities at predetermined positions on the surface of the magnet material and providing through holes in addition to the reduction in weight, weight, and thickness. As a high performance permanent magnet, an R-Fe-B sintered permanent magnet has been proposed (US Pat. No. 4,770,223, JP-A-59-46008, and JP-B-61-34242). B-based bonded magnets have also been proposed (US Pat. No. 4,902,361).

[0003] The above R-Fe-B sintered permanent magnet and R-
Since both Fe-B based bonded magnets usually include press forming in a magnetic field during the manufacturing process, only molded products having a simple shape were obtained. However, in order to respond to recent demands for various shapes, it has been studied to adopt an injection molding method which has been conventionally adopted in many technical fields for the method of manufacturing the R-Fe-B based sintered permanent magnet. Have been. For example,
An R-Fe-B alloy powder obtained by pulverizing an ingot of an R-Fe-B alloy and a binder containing a thermoplastic resin such as polyethylene or polystyrene are kneaded, injection-molded, and sintered after debinding. For producing sintered sintered permanent magnets (JP-A-61-220315, JP-A-64-28302)
JP-A-64-28303). Also, there has been proposed a method of manufacturing an R-Fe-B sintered permanent magnet employing an injection molding method using a paraffin wax as a binder (Japanese Patent Application Laid-Open No. 64-28302).

[0004]

However, in general, intermetallic compounds containing a rare earth element (R) are O, H, C, N
When a binder such as a thermoplastic resin or a paraffin wax used in the above-mentioned injection molding method is added to and mixed with the R-Fe-B alloy powder, the carbon in the binder is generally used. Since the content of oxygen and oxygen increases by the reaction with R, considerable carbon and oxygen remain even after injection molding, debinding, and after sintering. This hinders the application of complex shaped articles to magnet parts by molding methods. In addition, the binder used in the conventional injection molding method,
After being mixed with the alloy powder, the binder was melted by heating to the melting point of the binder in the injection molding machine, that is, about 100 ° C. to 200 ° C., but the Curie temperature (Tc) of the R—Fe—B permanent magnet is 300 Since the temperature is in the range of about ° C to about 350 ° C, there is a problem in that if the material is heated to a temperature close to the Curie temperature when it is oriented in a magnetic field, the orientation becomes difficult and a large magnetizing current is required for the orientation.

[0005] Therefore, when a binder having a low melting temperature is examined, 1.5 to 3.5 wt% of methylcellulose with respect to a target alloy powder has been conventionally used as a binder for compression molding of a Co-based superalloy powder. Further, a composition in which glycerin and boric acid, which are predetermined amounts of additives, are mixed has been proposed (US Pat. No. 4,113,480).
_As a binder for injection molding of ₂ O ₃ —ZrO ₂ or alumina powder, 10-50
A mixture in which deionized water and glycol are further added to wt% agarose or agar is proposed (US Pat. No. 4,734,23).
7) Further, as a binder for injection molding of alloy powder for tools, a special composition, 0.5 to 2.5 wt% of methyl cellulose with respect to the target alloy powder, water, a plasticizer such as glycerin, and a wax emulsion (Japanese Patent Laid-Open No. Sho 62-37302) has been proposed.

However, the above-mentioned binder mainly composed of methylcellulose or agar is used in a relatively large amount as described above with respect to the target alloy powder in order to secure a predetermined fluidity and strength of the compact. In addition, since it is essential to add various binder additives, for example, a plasticizer such as glycerin in the same amount as methylcellulose, after injection molding, degreasing, and even after sintering, considerable carbon and oxygen remain. Residues, particularly R-
In the case of the Fe-B based sintered permanent magnet, the magnetic properties are degraded, which hinders the application of the injection molding method to a magnet part having a complicated shape.

The present invention relates to a method for producing an R—Fe—B sintered permanent magnet formed by injection molding and sintering the same. And prevents deterioration of magnetic properties due to oxygen, does not require a large magnetizing current at the time of injection molding in a magnetic field, improves injection moldability, and improves the R-F of complex shapes, especially small products.
R by injection molding to obtain an eB sintered anisotropic magnet
-It is an object of the present invention to provide a method for producing an Fe-B based sintered magnet.

[0008]

Means for Solving the Problems The inventors can reduce the temperature of the mold during injection molding to 100 ° C. or less, suppress the reaction between the R component in the R—Fe—B-based alloy powder and the binder, and maintain the residual temperature. Agar and / or methylcellulose were selected as binders capable of reducing the amount of carbon and oxygen to be produced. Further R
As a result of examining the application to Fe-B-based alloy powder, it was found that if the R-Fe-B-based alloy powder has a predetermined average particle size, the amount of methylcellulose should be 0.5 for a large amount of water.
It was found that sufficient fluidity and strength of the molded body could be obtained even when the content was not more than wt%, and 4.0 was also used for agar.
It has been found that a similar effect can be obtained even with a small amount of not more than wt%. Not only the methylcellulose and agar below the predetermined amount but also the lubricant used as required may be used.
It was found that a very small amount of 30 wt% or less was sufficient, and it was further found that the same action and effect could be obtained even when agar and methyl cellulose were used in combination as a binder. That is, the inventors have conducted various studies for the purpose of a method capable of suppressing the reaction between the R component in the R-Fe-B-based alloy powder and the binder and reducing the amounts of carbon and oxygen remaining in the compact, Instead of the thermoplastic binder generally used in the conventional injection molding method, methylcellulose or agar, or a composite thereof, which undergoes sol-gel transformation at a predetermined temperature, is used as a binder in an R-Fe-B alloy powder. By using things and water, and even a small amount of lubricant, despite the fact that most of the binder is moisture,
Since sufficient viscoelasticity can be obtained, the amount of carbon in the total binder can be significantly reduced, and the moldability during injection molding is improved, and at the time of injection molding, gelation is performed in a mold at 100 ° C. or lower to cure. That it can be formed into a predetermined shape, that dehydration treatment and subsequent debinding treatment can remove almost all oxygen and carbon remaining in the molded body, and that sintering obtained after subsequent sintering It has been found that the amount of residual oxygen and carbon in the body can be significantly reduced, and a three-dimensionally complex sintered magnet having excellent magnetic properties can be obtained.

Further, the inventors consider that a large amount of water is contained in the binder, coat the surface of the R-Fe-B-based alloy powder with a resin, and then mix the above-mentioned binder to obtain water. And the reaction with the R component in the alloy powder can be suppressed, oxidation of the alloy powder in each step after kneading can be prevented, and the amount of residual oxygen in the obtained sintered body can be reduced.
Since the moldability during injection molding is further improved, a sintered magnet having a three-dimensionally complicated shape can be obtained, and almost all of the resin coated by the binder removal treatment can be removed. It was found that the amount was not increased. Furthermore, the present inventors have conducted various studies for the purpose of suppressing the reaction between the R component in the R-Fe-B-based magnetic powder and the binder and reducing the amount of residual carbon and oxygen. in the place of R-Fe-B alloy raw material powder of the required single composition that is generally used, R ₂ Fe ₁₄
A main phase alloy powder having an average particle diameter of 1 to 5 μm having a B phase as a main phase, and a part of R ₂ (FeCo) ₁₄ B phase or the like as an intermetallic compound phase of Co or Fe and R including an R ₃ Co phase. Containing a large amount of rare earth metal, and having an average particle diameter of 8 to larger than the main phase alloy so as to minimize the reaction with the organic binder.
A raw material obtained by mixing two types of raw materials of a liquid phase compound powder of 40 μm in a predetermined ratio is mixed, and a binder is added, kneaded,
By injection molding, debinding, and sintering, R-F
It has been found that the amount of residual oxygen and the amount of carbon in the e-B sintered body can be significantly reduced, the formability during injection molding can be improved, and a sintered magnet having a three-dimensionally complicated shape can be obtained. Further, the inventors further studied various methods for suppressing the reaction between the R component of the magnetic powder particles and the binder as much as possible and obtaining stable magnetic properties. As a result, particularly from the main phase alloy powder and the liquid phase compound powder, When an R-Fe-B-based alloy powder is used, a predetermined amount of a fine powder of a transition metal powder is further mixed with the alloy powder, and the surface of the magnetic powder particles is reduced by mechanofusion treatment in an inert atmosphere. After coating with transition metal powder,
The surface is diffused by heat treatment to make the coating dense and uniform, so that the coating completely separates the R component of the magnetic powder particles from the binder, and the process of kneading the binder, injection molding, debinding, and sintering is performed. Have found that the reaction between the R component of the magnetic powder particles and the binder can be prevented, and have completed the present invention.

That is, the present invention relates to a method for producing a compound comprising R (where R is at least one kind of rare earth element containing Y) of 11 atomic% to 1 atomic%.
A main phase-based alloy powder having an average particle diameter of 1 to 5 μm having a main phase of R ₂ Fe ₁₄ B phase composed of 3 atomic%, B 4 atomic% to 12 atomic%, balance Fe and unavoidable impurities, and R ₃ Co phase Including C
o or a part of R ₂ (FeC
o) 13 atomic% to 45 atomic% containing ₁₄ B phase or the like, and R (where R is at least one of rare earth elements including Y);
Mixing and mixing two kinds of raw material powders of 2 atomic% or less, the balance Co (however, part or most of Co can be replaced by Fe), and liquid phase compound powder having an average particle size of 8 to 40 μm consisting of unavoidable impurities A method for producing an R-Fe-B sintered magnet by an injection molding method, which comprises adding a binder, kneading, and then performing injection molding using the obtained raw material powder.

[0011] Further, according to the present invention, in the above structure,
The present invention proposes a method for producing a sintered anisotropic magnet by injection molding, wherein a surface of a main phase alloy powder and / or a liquid phase compound powder is coated with a resin or a transition metal. Further, the present invention, in the above configuration, the raw material powder blended with the main phase alloy powder and the liquid phase compound powder,
Methylcellulose and / or agar and water are added as an organic binder that causes a sol-gel reaction at a predetermined temperature, and a molded body is formed by injection molding in a magnetic field, and the molded body is sintered after debinding and contains a sintered body. 130 carbon
0 ppm or less, and the oxygen content is 10000 ppm or less, and preferably the carbon content of the sintered body is 10 ppm or less.
00 ppm or less, oxygen content of 9000 ppm or less, most preferably 800 ppm or less of carbon content contained in the sintered body,
This is a method for producing an R-Fe-B-based sintered magnet by injection molding, characterized in that the oxygen content is 8000 ppm or less.

According to the present invention, as an R-Fe-B alloy powder, R (where R is at least one of rare earth elements including Y) 11 at% to 13 at%, B 4 at% to 12 at%, the balance R ₂ Fe ₁₄ B composed of Fe and unavoidable impurities
Main phase alloy powder having an average particle diameter of 1 to 5 μm having a main phase as a main phase, and an intermetallic compound phase of Co or Fe and R including an R ₃ Co phase partially including an R ₂ (FeCo) ₁₄ B phase and the like , R (where R is at least one of the rare earth elements including Y) 13 atomic% to 45 atomic%, B 12 atomic% or less, the balance Co (however, part or most of Co can be replaced by Fe) and inevitable Liquid phase compound powder having an average particle size of 8 to 40 μm, which is composed of chemical impurities, is mixed and mixed at a predetermined ratio, and an alloy powder having an average particle size after mixing in the range of about 20 μm or less is used. By using these alloy powders and changing the average particle size of the two types of raw materials, and by adding an excess R component in advance in consideration of the generation of rare earth element oxides,
The addition of an excessive amount of the liquid phase compound powder makes it possible to sufficiently develop a liquid phase at the time of sintering, and it is possible to prevent deterioration of magnetic properties due to the reaction between the R component and the binder.

In the above compounded alloy powder, in order to obtain a main phase alloy powder, when R is less than 11 at%, the α-Fe phase crystallized during alloy melting increases, and when R exceeds 13 at%,
Since the R-rich phase increases and it is difficult to uniformly disperse the main phase and the R-rich phase, R is set in the range of 11 atomic% to 13 atomic%. If B is less than 4 atomic%, a high coercive force (iHc) cannot be obtained, and if it exceeds 12 atomic%, the residual magnetic flux density (Br) decreases, so that an excellent permanent magnet cannot be obtained. B is in the range of 4 to 12 atomic%. Further, the balance consists of Fe and inevitable impurities,
Fe is preferably in a range of 75 atomic% to 85 atomic%.
When the content is less than 75 at%, the rare earth element becomes relatively rich and the R-rich phase increases, and when it exceeds 85 at%, the rare earth element becomes relatively small, the residual Fe portion increases, and the alloy powder becomes non-uniform. . Co in the main phase alloy powder is R ₂ F
Co is preferably at most 10 atomic% in order to reduce the coercive force by being replaced by Fe in the e ₁₄ B main phase. However, when a part of Fe is substituted by the above-mentioned Co, the content of Fe is 62 atomic% or more.
The range is 85 atomic%. It is desirable that the main phase-based alloy powder has no R-rich phase at all from the viewpoint of reduction of oxygen content and uniformity of the structure.
The reduction in the oxygen content is not significantly impaired.

A liquid phase compound powder composed of an intermetallic compound phase of Co or Fe and R containing an R ₃ Co phase (a part or most of Co can be replaced by Fe) is R ₃ Co.
Phase or a phase in which Co of the R ₃ Co phase is partially substituted with Fe, and the central phase is RCo ₅ , R ₂ Co ₇ , RCo ₃ ,
RCo ₂ , R ₂ Co ₃ , R ₂ Fe ₁₇ , RFe _2, Nd ₂ C
o ₁₇ , Nd ₅ Co ₁₉ , Dy ₆ Fe ₂ , DyFe, etc., and the intermetallic compound phase and R ₂ (FeCo) ₁₄ B, R _1.11 (F
eCo) ₄ B ₄ or any other alloy powder. As described above, the composition of the liquid phase compound powder changes the ratio of the rare earth element contained in the intermetallic compound according to the type and amount of the rare earth element of the target composition. However, when R is less than 13 atomic%, the liquid phase is not sufficiently developed during sintering when a magnet is produced by blending with the main phase raw material, and when it exceeds 45 atomic%, the oxygen content increases. Is not preferred. Also, Co
Is 1 atomic% or more and preferably 3 to 20 atomic% in the liquid phase compound powder, and the remainder can be replaced by Fe. Further, when B exceeds 12 atomic%, R ₂ (FeC
o) In addition to the ₁₄ B phase, a B-rich phase, an Fe-B compound and the like are present in excess, which is not preferable. further,
Intermetallic compound phase of Co or Fe and R containing main phase alloy powder and / or R ₃ Co phase and R ₂ (FeCo) ₁₄
Cu, S, Ni,
Ti, Si, V, Nb, Ta, Cr, Mo, W, Mn,
Al, Sb, Ge, Sn, Zr, Hf, Ca, Mg, S
By adding and including at least one of r, Ba, and Be, it is possible to increase the coercive force, increase the corrosion resistance, and improve the temperature characteristics of the obtained permanent magnet. Usually, the total amount of these additive elements is desirably 10 at% or less, and the total amount is desirably appropriately selected such as 5 at% or less, 3 at% or less according to the additive elements.

In the above-mentioned compounded alloy powder, if the average particle size of the main phase alloy powder is less than 1 μm, the surface area of the alloy powder is increased. : It is necessary to increase the sintering density to 1.2, which is not preferable because the sintering density of the sintered product after injection molding is reduced to about 95%, and the average particle size exceeding 5 μm is too large for sintering. Saturates at about 95% density,
Since no improvement in the density can be expected, the average particle size is preferably in the range of 1 to 5 μm.

On the other hand, the average particle size of the liquid phase compound powder is 8
If it is less than μm, the reaction with the binder is almost the same as that of the alloy powder having a single composition (average particle size of 1 to 10 μm), and the effect of addition to the main component-based powder is hardly observed. When the average particle size of the liquid phase compound powder exceeds 40 μm, the reaction with the binder is considerably suppressed, but on the contrary, the sinterability during sintering deteriorates, the sintering density decreases, and simultaneously the coercive force decreases. Therefore, the average particle size of the liquid phase alloy powder is preferably 8 to 40 μm. Further, the main phase-based alloy powder and the liquid phase-based compound powder can be blended in a ratio of 70 to 99:30 to 1, preferably 70 to 97:30 to 3, and more than one composition depending on the magnetic properties. Can be obtained. By blending in such a ratio, the average particle size is 1 to 5
The average particle size of the mixed powder composed of the main component-based alloy powder of μm and the liquid phase alloy powder having the average particle size of 8 to 40 μm is 20 μm, which is the same as that of the alloy powder of the single composition.
m or less, preferably about 10 μm or less.

The method for producing the above-mentioned R-Fe-B alloy powder includes a melting / pulverizing method, a super-quenching method, a direct reduction diffusion method,
A known method such as a hydrogen-containing disintegration method or an atomizing method can be appropriately selected to obtain an alloy powder having a required average particle size. Regardless of which R-Fe-B-based alloy powder is used, by setting the average particle size to a preferable range, a transition metal powder for general injection molding, such as an Fe-based alloy powder or a Co-based alloy powder, may be used. Than average particle size from a fraction to 10
That is, the amount of the binder can be significantly reduced as compared with the amount of the binder used when injection-molding the transition metal powder.

Resin Coating In the present invention, coating the above-mentioned alloy powder, that is, the main phase alloy powder and / or the liquid phase compound powder, with a resin is performed by the reaction of the R element with water after kneading the binder, and the molding at the time of molding. This is effective for suppressing the reaction of the R element with water during the gelation step and the dehydration treatment after injection molding, and stabilizing and reducing the amount of residual oxygen. Polymethyl methacrylate (PMM) is used as the resin for coating the R-Fe-B alloy powder.
A), methacrylic resins such as polymethyl acrylate (PMA), and thermoplastic resins such as polypropylene, polystyrene, polyvinyl acetate, polyvinyl chloride, polyethylene, and polyacrylonitrile, alone or in combination, are preferably used. The amount of the resin added is preferably 0.30% by weight or less based on the alloy powder. This corresponds to a resin coating thickness of 50 ° to 200 °, and if it exceeds 0.30% by weight, the amount of residual oxygen from the coating resin is reduced. It is not preferable to increase. The coating method is a method commonly called a mechanofusion system or a hybridization system, or a method using a ball mill. The particle size of the resin powder for coating is preferably about 1,000 to 5,000. Since the alloy powder coated with the resin is relatively stable in the amount of residual oxygen, there is an advantage that the alloy powder can be recycled at the time of injection molding. The resin-coated alloy powder also has an advantage that injection molding can be performed without adding a lubricant during kneading.

In order to minimize the reaction between the R component of the magnetic powder particles and the binder, when the R-Fe-B-based alloy powder composed of the main phase-based alloy powder and the liquid phase-based compound powder is used, A predetermined amount of transition metal powder is further mixed with the alloy powder, and the surface of the magnetic powder particles is coated with the fine transition metal powder by mechanofusion treatment in an inert atmosphere, and then the surface is diffused by heat treatment. The coating is made dense and uniform, and the R
Raw material powder in which the components and the binder are completely separated can be used. The transition metal for the coating is a transition metal excluding rare earth elements, and among them, Fe, Ni, C
u and the like are preferable, and particularly, the Fe element most contained in the R-Fe-B-based magnetic powder has no restriction on the addition amount if the components of the magnetic powder are adjusted in advance, and also has an excellent spreadability. It is most preferable because it is easy to form a relatively uniform coating around the magnetic powder particles during the mechanofusion treatment due to the richness and it is relatively easy to obtain. Even if the transition metal powder reacts with the binder to form compounds such as carbides and oxides, it is easily deoxygenated and decarbonized at a relatively low temperature in a vacuum or by a temporary hydrogen flow. -Fe
-It is convenient for coating of alloy powder for sintered magnets by injection molding of B type. Further, if the average particle size of the transition metal powder for adhesion or coating is less than 0.02 μm, the transition metal powder itself is very activated and becomes an oxide, and the spreadability peculiar to the metal is poor. The thickness is preferably 0.02 μm to 1 μm because the transition metal fine powder is insufficiently adhered to the magnetic powder particles at the time of coating treatment by fusion, and defects are easily generated in the coating film. By applying the resin coating described above to the surface of the magnetic powder particles having the coating of the transition metal, the reaction between the R component in the magnetic powder particles and the binder or water can be further reduced, It is possible to obtain an R-Fe-B based sintered magnet having excellent magnetic properties.

Binder Component In the present invention, a binder obtained by adding water to methylcellulose or agar or a composite thereof, which undergoes sol-gel transformation at a predetermined temperature, is used as a binder for injection molding. When methylcellulose is used alone as a binder, the content at the time of less than 0.05% by weight significantly decreases the strength at the time of molding, and when it exceeds 0.50% by weight, the residual carbon content and the oxygen content increase to increase the coercive force. And the magnetic characteristics deteriorate, so that 0.05 wt% to 0.50 w
A content of t% is preferred in these respects. 0.1w
t% to 0.45 wt% is desirable, and 0.15 wt% to
0.4 wt% is most desirable. If the content of agar alone is less than 0.2 wt%, the strength at the time of molding is significantly reduced, and if it exceeds 4.0 wt%, the residual carbon content and the oxygen content are increased and the coercive force is reduced, Since magnetic properties deteriorate, a content of 0.2 wt% to 4.0 wt% is preferable in these respects. Furthermore, 0.5 wt% to 3.5 wt% is desirable, and 0.5 wt% to 2.5 wt% is most desirable. When methyl cellulose and agar are used in combination, if the content is less than 0.2 wt%, the strength at the time of molding is remarkably reduced, and the releasability between the molding die and the molded body is deteriorated. If it exceeds 0 wt%, the sintered density after sintering will decrease and the residual carbon content and oxygen content will increase, resulting in deterioration of the properties of the magnet, which is undesirable. Therefore, 0.2 wt% to 4.0 wt% is preferable. However,
It is not desirable that the content of methylcellulose exceeds the range in the case where the above-mentioned methylcellulose is contained alone, and the total content is 3.5 wt% or less.
5 wt% or less is desirable.

The present invention is characterized in that water is used together with methylcellulose and / or agar as a binder. In order to suppress the reaction with R, it is desirable to use deoxygenated pure water. When methylcellulose alone is used, if the water content is less than 6 wt%, the fluidity at the time of molding deteriorates, and short shots are liable to occur. Since the residual oxygen amount increases at the same time as the sintered density after sintering decreases, and the magnetic characteristics deteriorate, the content of 6 to 16 wt% is most preferable. If the content of water in the case of using agar alone is less than 8 wt%, the fluidity during molding is deteriorated, and short shots are liable to occur,
If it exceeds 18 wt%, the total amount of the binder increases, so that the sintered density decreases after sintering, the residual oxygen amount increases, and the magnetic properties deteriorate, so that 8 to 18 wt% is most preferable. When methyl cellulose and agar are used in combination, the ratio is appropriately selected from the range of 6 to 18 wt% in consideration of the ratio of methyl cellulose and agar.

It is also effective to add at least one kind of lubricant such as glycerin, wax emulsion, stearic acid, or water-soluble acrylic resin to the above-mentioned binder. If both are less than 0.10 wt%, the density of the molded body tends to be non-uniform. Particularly, when methyl cellulose alone is used, if it exceeds 0.30 wt%, the strength of the molded body is reduced. .30
wt% is most preferred, and when agar is used alone, if it exceeds 1.0 wt%, the strength of the molded body is similarly reduced. Therefore, 0.10 wt% to 1.0 wt% is most preferred. When methylcellulose and agar are used in combination as the binder, the ratio is appropriately selected from the range of 0.1 wt% to 1.0 wt% in consideration of the ratio of methylcellulose and agar.

Injection molding conditions Injection conditions vary according to the amount of binder added.
C. to 90.degree. C. is preferable. If the temperature is lower than 70.degree. C., solidification may be insufficient at the time of removal after molding, which may cause deformation. If it exceeds 90.degree. When agar is used alone, the mold temperature is preferably from 10 ° C. to 30 ° C.
If the temperature is lower than 0 ° C., the fluidity is deteriorated. If the temperature is higher than 30 ° C., the solidification is insufficient at the time of removal after molding, which may cause deformation. The injection temperature is preferably from 0 to 40 ° C when methylcellulose is used alone. If the temperature is lower than 0 ° C, the kneaded material freezes and the fluidity decreases. If the temperature exceeds 40 ° C, the fluidity becomes insufficient and short-circuiting occurs. This is not preferable because shots are likely to occur. When agar is used alone, the injection temperature is preferably from 75 to 95 ° C. If the temperature is lower than 75 ° C, the fluidity is insufficient and short shots are likely to occur. The evaporation of water causes bubbles to occur, causing voids in the sintered body after sintering. In addition, due to the evaporation of water, the fluidity of the kneaded material is reduced, and the kneaded material is clogged in the molding machine. It is not preferable because there is a possibility. The injection molding pressure is 30 kg /
If it is less than ² cm ² , welding occurs and the molding density becomes non-uniform, bending or swelling occurs after sintering. Also, if methyl cellulose is used alone, if it exceeds 50 kg / cm ² , burring will occur, which is not preferable. For 30-50k
g / cm ² is preferred, also, since the burrs as well as the case of using agar alone exceeds 70 kg / cm ² is not preferable occurs, the pressure is preferably 30~70kg / cm ^2. Therefore, when using a combination of methylcellulose and agar, considering the ratio of methylcellulose and agar,
The mold temperature, injection temperature, injection molding pressure and the like may be appropriately selected from the above ranges. If the magnetic field at the time of injection molding in a magnetic field for obtaining a sintered anisotropic magnet is less than 10 kOe, orientation is insufficient, so that injection molding in a magnetic field of 10 kOe or more is preferable.

Debinding Treatment A dehydration treatment is performed as a pre-step of the debinding treatment, but the treatment method is not particularly limited together with the debinding treatment. For example, when the dehydration treatment is performed by a heating and drying method, the heating temperature varies depending on the amount of pure water selected, but at least the heating rate from 20 ° C to 100 ° C is 30 to 60 ° C / hr.
If the temperature is lower than 30 ° C./hr, the processed product may be oxidized. If the temperature is higher than 60 ° C./hr, the processed product may be cracked or cracked due to rapid vaporization and evaporation of water. In particular, if the processed product is small, at least 2
The rate of temperature rise from 0 ° C to 100 ° C is preferably 45 to 55 ° C / hr, and the dehydration treatment can be further simplified. Also, 10
Since most of the water evaporates during the temperature rise to 0 ° C., dehydration treatment in a temperature range exceeding 100 ° C. is unnecessary. Subsequently, the binder is removed, but the heating rate is
Since the binder can be removed at a temperature of 100 to 200 ° C./hr, there is an advantage that the processing time can be significantly shortened as compared with the case of a normal organic binder. Further, in order to perform the dehydration treatment continuously from a low temperature to a high temperature and to suppress the oxidation of the R-Fe-B-based alloy powder, the dehydration atmosphere is set to 1 × 10 ⁻³ Torr.
It is preferable to carry out in the following vacuum. After the dehydration treatment, it is preferable to perform sintering by heating and heating continuously, and the heating rate after exceeding 500 ° C. may be arbitrarily selected. For example, the sintering may be performed at 100 to 300 ° C./hr. A well-known method of raising the temperature which is taken at the time of knotting can be adopted.

The sintering of the molded article after the binder removal treatment and the heat treatment conditions after the sintering are appropriately selected according to the selected alloy powder composition. It may be the same as the manufacturing conditions. Preferred sintering and heat treatment conditions after sintering are as follows:
A sintering step of holding for 2 hours and an aging step of holding at 450 to 800 ° C. for 1 to 8 hours are preferable.

In the present invention, the upper limit of the amount of carbon and oxygen contained in the sintered body is 1300 ppm or less for carbon, 10000 ppm or less for oxygen, and 1000 pp for carbon.
m, an oxygen content of 9000 ppm or less, particularly under optimum conditions, a carbon content of 800 ppm or less and an oxygen content of 80 ppm or less.
The content can be reduced to 00 ppm or less, and a sintered magnet having excellent magnetic properties can be obtained. Therefore, depending on each condition, at the maximum energy product, 4MGOe or more, 10MG
Oe or more and 15 MGOe or more are obtained, and under particularly preferable conditions, 20 MGOe or more is obtained.

[0027]

As is generally well known, agar, which is a feature of the present invention, dissolves into a viscous sol-like substance when heated to about 95 ° C. in water, and becomes elastic when cooled to about 40 ° C. or less. It becomes a viscous gel-like substance and solidifies. on the other hand,
Methylcellulose, when dissolved in water, is heated to about 50 ° C. to dissolve into a viscous sol-like substance, and further heated to 70 ° C. or higher to become an elastic gel-like substance,
Once gelled, the gel state is maintained regardless of the temperature change, and the sol
Causes a gel reaction. Utilizing both properties, when the agar binder is considered as a main component, the viscosity in the sol state can be improved at a temperature of about 80 ° C. by adding a small amount of methylcellulose. Therefore, the slight addition of methylcellulose makes it possible to reduce the addition amount of the usual agar binder (about 3 wt%) to a fraction.
In spite of such a large amount of water, viscoelasticity is generated with a small amount of agar binder, so that the carbon content in the total binder as a binder for injection molding can be significantly reduced. Also, 100 ° C at the time of degreasing
By the time, about 99% of the water in the total binder is removed by evaporation. At a temperature at which the R-Fe-B powder becomes active, since oxygen due to a large amount of water has already been released, R- There is an advantage that oxidation of the Fe-B alloy powder can be largely suppressed. Furthermore, the mold temperature during injection molding is set to 100 ° C.
It does not require a large magnetizing current at the time of injection molding in a magnetic field, improves injection moldability, and obtains an R-Fe-B sintered anisotropic magnet of a complicated shape, especially a small product. .
By changing the average particle size of the two types of raw materials, the main phase alloy powder and the liquid phase compound powder, and simultaneously adding an excess R component in anticipation of the generation of oxides of rare earth elements, the excess liquid phase By adding the compound powder, it is possible to sufficiently develop a liquid phase at the time of sintering, and it is possible to prevent the magnetic properties from deteriorating due to the reaction between the R component and the binder.

[0028]

【Example】

Example 1 11.5 atomic% of Nd and 0.2 atomic% of Pr as R, B
A button-shaped ingot alloy produced by subjecting an alloy lump composed of 7.0 atomic% and the remainder to Fe and unavoidable impurities by high-frequency heating and melting in Ar gas is roughly pulverized and then reduced to an average particle size of about 15 μm by a jaw crusher or the like. The main phase raw material powder having an average particle size of 3 μm obtained by coarsely pulverizing and then finely pulverizing by jet mill pulverization, 19.7 atomic% of Nd and 0.8 atomic% of Pr, D
y1.1 at%, Co 15.0 at%, B 4.5 at%, the balance is a button-shaped smelting alloy produced by high-frequency heating and melting an alloy lump made of Fe in Ar gas using a jaw crusher or the like. The liquid phase raw material powder roughly crushed to about 14 μm was mixed and mixed at a weight ratio of 76:24. The analysis value of this mixed powder was Nd 13.4 atomic% and Pr 0.3
4 atomic%, Dy 0.26 atomic%, Co 3.6 atomic%, B
6.4 atomic%, with the balance being Fe. Using the above mixed powder, binders, water and additives of the types and amounts shown in Table 1 were added and kneaded at room temperature, and the obtained kneaded pellets were set and maintained at the injection temperature and mold temperature shown in Table 1. To a 20 mm x 20 mm x 3 mm plate in a magnetic field (15 kO
Injection molding was performed in e). Glycerin was used as an additive. The obtained molded body is heated in a vacuum from room temperature to 100 ° C.
The temperature was raised at a heating rate of 50 ° C./H until the temperature was maintained at this temperature for 1 hour to completely dehydrate.
The temperature was raised with H to remove the binder. Further heating 110
It was kept at 0 ° C. for 1 hour and sintered. After the completion of sintering, Ar gas was introduced to cool to 800 ° C. at a rate of 7 ° C./min, and then aging treatment was performed at 100 ° C./hour to hold at 550 ° C. for 2 hours. No cracks, cracks, deformation, etc. were observed in the obtained sintered body. Table 2 shows the characteristics of the Nd—Fe—B sintered alloy obtained by this step.

Comparative Example After ingots of the respective elements were weighed so that the components of the final sintered body were the same as those of the above-mentioned example, and then melted by high-frequency heating in Ar gas, a button-shaped ingot alloy was roughly pulverized. The raw material powder having an average particle size of 3 μm was obtained by coarsely pulverizing to an average particle size of about 15 μm with a jaw crusher and the like, and then finely pulverizing by jet mill pulverization. The obtained raw material powder is Nd1
3.3 at%, Pr 0.31 at%, Dy 0.28 at%, Co 3.4 at%, B 6.5 at%, and the balance Fe. This raw material powder and an acrylic binder as a binder were blended at a volume ratio of 1: 1 to obtain a mixture.
After heating and kneading at 0 ° C. for 10 minutes to form a kneaded product for injection molding, injection molding was performed in a mold heated to 45 ° C. in a magnetic field strength of 15 kOe, and a length of 10 mm × width of 10 mm × height of 5 mm
Was obtained. 3 × 10 ^-4 injection molding
After debinding treatment in which the temperature was raised to 350 ° C. at a rate of 6 ° C./hour in a vacuum of Torr, sintering and heat treatment were performed under the same conditions as in Example 1 to obtain a sintered anisotropic magnet. (Comparative Example 1) Further, the sample No. 1, No. 2, No. Sample No. 3 of the example was produced under the same conditions as in the example except that the alloy powder composed of the mixed powder of Example 3 was replaced with the alloy powder composed of the single composition. Comparative Example 2, Sample No. 1 corresponding to Comparative Example 3, Sample No. 2 corresponding to Comparative Example 4 corresponding to No. 3 was obtained. Table 2 shows the measurement results of the magnet characteristics, the residual oxygen amount, and the residual carbon amount of the obtained comparative example magnets 1 to 4 together with the examples.

As is apparent from Table 2, the amount of residual oxygen and the amount of residual carbon are significantly reduced in the example, and the magnetic characteristics are remarkably reduced, as compared with the comparative example 1 using the conventional acrylic binder. It turns out that it is excellent. Further, compared with the case of using the R-Fe-B-based magnetic powder having a single composition of the comparative example, the main component-based powder having an average particle diameter of 3 μm and the liquid phase-based powder having an average particle diameter of 15 μm according to the present invention were used. It can be seen that the magnetic characteristics are considerably better when the mixed powder is used, while the residual oxygen content and the residual carbon content are almost the same. This is presumably because liquid-phase sintering has progressed favorably because the liquid-phase raw material powder has been added in advance so as to compensate for the consumption of the rare earth element. The large particle size of the liquid phase compound powder having a large amount of R significantly suppressed the oxidation reaction between R and water. Most of the binder was water. At a temperature at which the alloy powder becomes active, the fact that water has already evaporated and disappears is also considered to be a factor in improving magnetic properties.

[0031]

[Table 1]

[0032]

[Table 2]

Example 2 300 g of the mixed powder obtained in Example 1 was added to polymethyl methacrylate (PMMA) having a hydrophobic average particle size of 0.15 μm.
Was added into a container of a mechanofusion system, the temperature was maintained at 70 ° C., and the rotation speed of the container was maintained at a maximum of 1,800 rpm for 10 minutes to perform resin coating (film thickness: about 100 °). Using alloy powder of fine powder,
Binders, water and additives of the types and amounts shown in Table 3 were added and kneaded at room temperature. The obtained kneaded pellets were set at the injection temperature and mold temperature shown in Table 3 and maintained at 20 mm × 20.
The plate was injection molded in a magnetic field (15 kOe) on a 3 mm × 3 mm plate. Glycerin was used as an additive. The obtained molded body is heated in a vacuum from room temperature to 100 ° C. at a heating rate of 50 ° C.
After the temperature was raised at a rate of 100 ° C./H, the temperature was maintained for 1 hour to completely dehydrate, and then the temperature was raised to 500 ° C. at a rate of 100 ° C./H to remove the binder. It was further heated and held at 1100 ° C. for 1 hour for sintering. After sintering is completed, Ar gas is introduced and 7 ° C /
It was cooled to 800 ° C. at a rate of 1 minute, then cooled at 100 ° C./hour and subjected to an aging treatment at 550 ° C. for 2 hours. No cracks, cracks, deformation, etc. were observed in the obtained sintered body. Nd-Fe-B obtained by this process
Table 4 shows the properties of the sintered alloy. Although the magnet according to the present embodiment in which the surface of the mixed powder is coated with the resin and the magnet according to the embodiment 1 in which the surface is not coated with the resin have substantially the same magnet characteristics, residual oxygen amount, and residual carbon amount, Since the surface of the magnet according to the embodiment is coated with a resin, it is very stable against oxygen in the state of a molded body and a kneaded material before sintering, and even after leaving them for several hours, the oxygen content thereof is reduced. The amount hardly increased. On the other hand, when the magnet without resin coating according to Example 1 was left for several hours in the state of the molded body and the kneaded material, the oxygen content thereof increased sharply, and the magnet properties after sintering were significantly reduced.

[0034]

[Table 3]

[0035]

[Table 4]

Example 3 A mixed powder obtained by adding 7.0 wt% of a fine iron powder having an average particle size of 0.02 μm to the mixed powder obtained in Example 1 and mixing the resultant was mixed with a mechanofusion device (AM-20F manufactured by Hosokawa Micron Corporation).
V), the vessel was charged with argon gas, and the Fe powder was coated by maintaining the arm head temperature at 50 ° C. or less during operation for 3 hours at 700 rpm while performing water cooling control. An alloy powder was prepared. The mixed powder, the binder, water, and additives of the types and amounts shown in Table 5 were added and kneaded at room temperature. The obtained kneaded pellets were set and maintained at the injection temperature and mold temperature shown in Table 5. 20mm ×
Injection molding was performed on a 20 mm × 3 mm plate in a magnetic field (15 kOe). Glycerin was used as an additive. The obtained molded body is heated in a vacuum from room temperature to 100 ° C. at a heating rate of 50 ° C./H, kept at this temperature for 1 hour and completely dehydrated, and then heated to 500 ° C. at a heating rate of 100 ° C./H. The temperature was raised to remove the binder. It was further heated and held at 1100 ° C. for 1 hour for sintering. After sintering is completed, Ar gas is
Cooled to 800 ° C. at a rate of 100 ° C./min.
An aging treatment of cooling at 550 ° C. for 2 hours was performed. No cracks, cracks, deformation, etc. were observed in the obtained sintered body. The Nd-Fe- obtained by this process
Table 6 shows the properties of the sintered B alloy. The magnet according to the present embodiment in which the surface of the mixed powder is coated with the iron powder and the magnet according to the embodiment 1 in which the surface is not coated with the iron powder have the following characteristics:
Although the residual carbon content is almost the same, the magnet according to the present embodiment is very stable against oxygen in the state of the molded body and the kneaded material before sintering because the surface is coated with iron powder. Even after leaving them for several hours, their oxygen content hardly increased. On the other hand, when the magnet not coated with iron powder according to Example 1 was left in the state of a compact and a kneaded material for several hours, the oxygen content increased sharply, and the magnet properties after sintering were significantly reduced. .

[0037]

[Table 5]

[0038]

[Table 6]

[0039]

According to the present invention, a main component-based alloy powder having a main phase of R ₂ Fe ₁₄ B and having an average particle size of 1 to 5 μm, and R ₃ C
The intermetallic compound phase of Co or Fe and R including the o phase partially includes the R ₂ (FeCo) ₁₄ B phase and the like, and has an average particle size larger than that of the main component alloy so as to minimize the reaction with the organic binder. After mixing two kinds of raw materials of a liquid phase compound powder having a large rare earth metal content with an average particle diameter of 8 to 40 μm at a predetermined ratio, methyl cellulose and / or a binder and pure water are added and kneaded, and the mixture is formed into a desired shape. By injection molding, the moldability during injection molding is improved, and a sintered magnet having a three-dimensionally complicated shape can be obtained, and the obtained molded body is dehydrated and debindered at a specific heating rate. By processing, the binder removal time is reduced to several hours,
By adding an excess amount of the R component in advance in anticipation of the generation of the oxide of the rare earth element, the reaction with the rare earth element (R) during the treatment is remarkably suppressed, and in particular, the residual oxygen amount is reduced, and the magnetic properties are deteriorated. And a sintered anisotropic magnet having a complicated shape and excellent magnetic properties can be obtained. In addition, it is possible to obtain a sintered anisotropic magnet having a complicated shape and excellent magnetic properties without requiring a large magnetizing current at the time of injection molding in a magnetic field because the mold temperature during injection molding can be kept at 100 ° C. or less. Can be. Furthermore, by coating the surface of the powder with a resin or a transition metal, an increase in the amount of oxygen during the step before sintering can be suppressed.

Claims (4)

(57) [Claims] 1. R (where R is at least one of rare earth elements including Y) 11 to 13 at%, B 4 at%
Up to 12 atomic%, the balance being Fe and unavoidable impurities
A main phase alloy powder having an average particle diameter of 1 to 5 μm having a main phase of ₂ Fe ₁₄ B phase, and a part of R ₂ (FeCo) _{14 in} an intermetallic compound phase of Co or Fe and R including an R ₃ Co phase Including phase B,
R (where R is at least one of the rare earth elements including Y
Seed) 13 atomic% to 45 atomic%, B 12 atomic% or less, average particle size of 8 to 40 μm consisting of Co (but Co can be partially or largely replaced by Fe) and unavoidable impurities
R-Fe-B by an injection molding method, wherein a raw material powder obtained by mixing and mixing two types of raw material powders of a liquid phase compound powder of m is added, kneaded, and then injection-molded.
Method for manufacturing sintered magnets. 2. The resin according to claim 1, wherein the surface of the main phase alloy powder and / or the liquid phase compound powder is coated with a resin.
A method for producing a sintered anisotropic magnet by the injection molding method described in 1 above. 3. The method for producing a sintered anisotropic magnet by injection molding according to claim 1, wherein the surface of the main phase alloy powder and / or the liquid phase compound powder is coated with a transition metal. . 4. An injection molding in a magnetic field by adding methylcellulose and / or agar and water as an organic binder causing a sol-gel reaction at a predetermined temperature to a raw material powder in which a main phase alloy powder and a liquid phase compound powder are blended, and injection molding in a magnetic field. The sintered body is sintered after removing the binder to reduce the carbon content of the sintered body to 1300 ppm or less and the oxygen content of 10,000.
4. The R-Fe- by injection molding method according to claim 1, wherein the R-Fe-
A method for producing a B-based sintered magnet.