JPH06290922A - Manufacture of r-fe-b sintered magnet by injection molding method - Google Patents

Abstract

PURPOSE:To enable an R-Fe-B sintered magnet to be prevented from deteriorating in magnetic properties and enhanced in injection molding properties by a method wherein material obtained by adding water to methyl cellulose, agar-agar, or composite of them which makes a sol-gel transformation at a prescribed temperature is used as binder which is added to R-Fe-B alloy powder. CONSTITUTION:Methyl cellulose and/or agar-agar which makes a sol-gel transformation at a prescribed temperature and water are added to R-Fe-B alloy powder (R denotes at least one element out of rare earth elements, including Y), kneaded, and molded into a body of certain shape through an injection molding method. The molded body is dehydrated, debindered in a flow of hydrogen, dehydrogenated, and sintered into an R-Fe-B sintered magnet. By this setup, a sintered magnet which is lessened in residual carbon, excellent in magnetic properties, and three-dimensionally complicated in a shape can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to R-molded by injection molding.
The present invention relates to a method for producing an Fe—B-based sintered anisotropic permanent magnet, wherein finely crystallized R—Fe—B-based alloy fine powder and methyl cellulose and / or agar and water are used as a binder to cause a sol-gel reaction at a predetermined temperature. After injection-molding a kneaded product with and dewatering it, debinding process in dehydrogenated hydrogen, dehydrogenation process, and sintering are performed to suppress the residual carbon amount and oxygen amount in the sintered body. The present invention relates to a method for producing a sintered anisotropic magnet by injection molding, which prevents deterioration of magnetic properties and improves moldability at the time of injection molding to obtain a sintered magnet having a three-dimensionally complicated shape.

[0002]

2. Description of the Related Art Today, compact motors and actuators used for home appliances, computer peripherals, automobiles, etc. are required to be compact and lightweight and have high performance. In order to reduce the weight, reduce the weight, and reduce the wall thickness, products with a three-dimensionally complicated shape are required.

As a method of obtaining a high-performance permanent magnet having a complicated shape, a rare earth bond magnet is prepared by kneading a resin binder or the like using a Sm-Co magnetic material or an R-Fe-B magnetic material and mechanically molding it. Manufacturing method, or R-Fe-B
The alloy powder obtained by crushing the base alloy ingot and the resin binder are kneaded, injection-molded, and then sintered after debinding.
-Fe-B system sintered permanent magnet manufacturing method (JP-A-61-2
20315, JP 64-28302 A, JP 64-28303 A) have been proposed.

[0004]

Generally, an intermetallic compound containing a rare earth element (R) easily reacts with an element such as O, H, C and N, and when kneading the magnetic powder and an organic binder, Alternatively, when the binder is removed, the R component in the magnetic powder reacts with the binder to deteriorate the magnetic properties, and particularly, the moldability at the time of injection molding becomes very poor, which makes it difficult to obtain a complicated shape.

A thermoplastic binder (acrylic type, wax type, polymer such as polyethylene and polystyrene) generally used in the conventional injection molding method is used as R-Fe-
When added and mixed with the B alloy powder, the content of carbon and oxygen generally increases due to the reaction with R. Therefore, injection molding,
After degreasing, considerable carbon and oxygen remain even after sintering,
In particular, in the case of a permanent magnet, the magnetic properties are deteriorated, which hinders the application of complicated shaped products to the magnetic parts by the injection molding method.

Therefore, the inventor used a binder containing methylcellulose and water or methylcellulose, agar and water as the main components instead of the conventional binder composed of paraffin wax or thermoplastic resin, and the sol-gel reaction of the binder. A method for producing an R—Fe—B based sintered magnet in which the reaction between the binder and the R component is suppressed by reducing the residual oxygen and the carbon content by injection molding using the method (Japanese Patent Application No.
No. 191727, Japanese Patent Application No. 4-191728). Although the amount of carbon in the total binder was reduced by such a method, it could not be completely removed by the degreasing treatment that is performed in a vacuum after injection molding, and some carbon remained in the sintered body after sintering. Then, there was a problem of deteriorating the magnetic characteristics. In addition, since most of the binder in the injection molding method is water, the amount of oxygen in the alloy powder increases due to the reaction between R of the R-Fe-B alloy powder and water, and the magnetic properties of the sintered body are increased. There was a problem that deteriorates.

The present invention relates to a method for producing an R-Fe-B system sintered permanent magnet which is formed by injection molding and is sintered, in which a magnet is formed by the reaction between the R component and the binder and the residual carbon and oxygen. It is an object of the present invention to provide a manufacturing method capable of preventing deterioration of characteristics, improving injection moldability, and obtaining an R-Fe-B based sintered magnet having a complicated shape, particularly a small product.

[0008]

The inventors have found that R-Fe-
As a result of various studies aimed at a method capable of suppressing the reaction between the R component in the B-based alloy powder and the binder and reducing the amount of residual carbon and oxygen, the thermoplasticity generally used in the conventional injection molding method was found. Instead of the above binder, methyl cellulose or agar which causes a sol-gel transformation at a predetermined temperature or a mixture of these and water added is used as the binder, or the surface of the R-Fe-B alloy powder is further coated with a resin. Using alloy powder, water and R
Suppresses the reaction with and stabilizes the oxygen content of the alloy powder after kneading and improves the moldability during injection molding, and further gels and hardens it in the mold during injection molding to mold it into the desired shape After the dehydration and drying treatment, the residual oxygen content and the carbon content in the R-Fe-B powder can be greatly reduced by performing the binder removal treatment in flowing hydrogen, and then the dehydrogenation treatment and the sintering. It was found that a three-dimensionally complicated sintered magnet having excellent magnetic properties can be obtained by
Completed this invention.

That is, the present invention provides an R—Fe—B alloy powder (R is at least one rare earth element containing Y).
In addition, methyl cellulose and / or agar which causes a sol-gel reaction as a binder at a predetermined temperature and water are added and kneaded, and then a molded body is formed by injection molding, and the molded body is dehydrated, and then in a stream of hydrogen. This is a method for producing an R—Fe—B based sintered magnet by an injection molding method, characterized by performing a binder removal treatment, and further performing a dehydrogenation treatment and then sintering. Further, the present invention proposes a method for producing an R-Fe-B system sintered magnet by an injection molding method, characterized in that the surface of a raw material fine powder is coated with a resin in the above-mentioned constitution, followed by injection molding. . Further, in the above-mentioned constitution, the composition containing 0.1 to 1.0 wt% of at least one of glycerin, stearic acid, emulsion wax, and water-soluble acrylic resin as a lubricant and 6 to 18 wt% of water in the binder is magnetic. A method for producing an R-Fe-B based sintered magnet by an injection molding method, which is characterized in that it is used as a powder binder, is proposed. Further, according to the present invention, in any of the above configurations, the amount of carbon contained in the sintered body is 70%.
This is a method for producing an R-Fe-B based sintered magnet by injection molding capable of reducing the oxygen content to 0 ppm or less and the oxygen content to 9000 ppm or less.

R-Fe-B type alloy powder In the present invention, the R-Fe-B type alloy powder is
R (where R is at least 1 of rare earth elements including Y)
Seed) 8 atom% to 30 atom%, Fe42 atom% to 90 atom%, B2 atom% to 28 atom% as an average particle size 1
10 to 10 μm is desirable, and fine powder of 1 to 6 μm is more preferable. The rare earth element R (where R is at least one of rare earth elements including Y) is at least one of Nd, Pr, Ho and Tb, or further La, Sm, Ce,
At least 1 of Er, Eu, Pm, Tm, Yb, Y
It preferably contains a seed, and if it is less than 8 atom%, the crystal structure becomes a cubic crystal structure having the same structure as α-iron, so that high magnetic properties, particularly high coercive force cannot be obtained.
The rich non-magnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, R is preferably in the range of 8 atom% to 30 atom%.
When B is less than 2 atomic%, a rhombohedral structure is formed, and a high coercive force (iHc) cannot be obtained. When it exceeds 28 atomic%, the B-rich nonmagnetic phase increases and the residual magnetic flux density (Br) decreases. , I can't get a good permanent magnet. Therefore, B is preferably in the range of 2 atom% to 28 atom%. Fe is
If it is less than 42 atom%, the residual magnetic flux density (Br) is lowered,
If it exceeds 0 atom%, a high coercive force cannot be obtained.
Is preferably 42 atom% to 90 atom%. Further, in the present invention, substituting a part of Fe with Co can improve the temperature characteristics without deteriorating the magnetic characteristics of the obtained magnet, but when the Co substitution amount exceeds 50% of Fe. ,
On the contrary, the magnetic properties are deteriorated, which is not preferable. Further, adding at least one of the following additional elements means that
-It is effective in improving the coercive force and the like of the B-R permanent magnet, improving the manufacturability, and reducing the cost. Ti, N
i, V, Nb, Ta, Cr, Mo, W, Mn, Al, S
b, Ge, Sn, Zr, Bi, Hf, Cu, Si, S,
C, Ca, Mg, P, H, Li, Na, K, Be, S
r, Br, Ag, Zn, N, F, Se, Te, Pb. In the present invention, the average particle size of the R—Fe—B alloy powder is preferably 1 to 10 μm, and the average particle size of the alloy powder is 1 μm.
Since the surface area of the alloy powder is increased in the case of less than, the binder addition amount for forming a kneaded product is a volume ratio with the alloy powder,
It is necessary to increase the ratio to 1: 1.2, which is not preferable because the sintered density of the sintered product after injection molding is reduced to about 95%, and if the average particle size exceeds 10 μm, the particle size is too large and firing is not performed. It is not preferable because the consolidation density is saturated at about 95% and the improvement of the density cannot be expected.

Further, as R-Fe-B type alloy powder, R
(However, R is at least one of rare earth elements including Y)
12 atom% to 25 atom%, B4 atom% to 10 atom%, C
o Main component-based alloy powder having an average particle size of _{1 to 5} μm, which contains 0.1 atom% to 10 atom% and Fe 68 atom% to 80 atom% as main components, and R ₂ Fe _{1 4} B phase as a main phase, and R ₃ In the intermetallic compound phase of Co or Fe and R including the Co phase, R ₂ (Fe
Co) ₁₄ B phase and the like, R (where R is at least one of rare earth elements including Y) 20 atom% to 45 atom%, Co
It is possible to use a raw material prepared by mixing and mixing liquid phase compound powders having an average particle diameter of 8 to 40 μm with 3 atomic% to 20 atomic%, B 12 atomic% or less, and the balance Fe at a predetermined ratio. Using these alloy powders, the average particle size of the two kinds of raw materials is changed, and at the same time, the excess R component is added in advance in anticipation of the generation of oxides of rare earth elements. It is possible to sufficiently develop the liquid phase at the time of binding, and it is possible to prevent the deterioration of the magnetic properties due to the reaction between the R component and the binder. In order to obtain a main component alloy powder in the above compounded alloy powder, if R is less than 12 atomic%, the α-Fe phase crystallized during alloy melting increases, which is not preferable, and if R exceeds 25 atomic%. Residual magnetic flux density (B
Since r) decreases, R is preferably 12 atom% to 25 atom%. Further, B has a high coercive force (i
Hc) cannot be obtained, and the residual magnetic flux density (Br) decreases if it exceeds 10 atom%, so B is preferably 4 atom% to 10 atom%. Co in the main component alloy powder is 0.1 atom%
The above content is effective in reducing the amount of oxygen in the raw material. Further, when Co exceeds 10 atomic%, it is substituted with Fe in the R ₂ Fe ₁₄ B phase to lose the coercive force. Therefore, when Co is contained, 0.1 atomic% to 10 atomic% is preferable. Further, the balance consists of Fe and inevitable impurities,
Is less than 68 atomic%, the rare earth element becomes relatively rich and the R-rich phase increases, and when more than 80 atomic%, the residual F
The range of 68 at% to 80 at% is preferable because the amount of e is too large and the amount of rare earth elements becomes relatively small, and the rare earth elements required for liquid phase sintering are consumed too much due to the oxidation reaction with the binder. . The main component alloy powder contains 4 wt% to 20 wt% of R in order to improve the sinterability and the residual magnetic flux density after sintering together with the R ₂ Fe ₁₄ B phase which is the main phase.
A rich phase can be included. Liquid phase compound powders composed of Co containing R ₃ Co phase or an intermetallic compound phase of Fe and R (provided that part or most of Co can be replaced by Fe) are R ₃ Co phase or R ₃ Co phase. The central phase is RC
o ₅ , R ₂ Co ₇ , RCo ₃ , RCo ₂ , R ₂ Co ₃ , R ₂ Fe
₁₇ , RFe _2, Nd ₂ Co ₁₇ , Nd ₅ Co ₁₉ , Dy ₆ Fe ₂ ,
DyFe, etc., and the intermetallic compound phase and R ₂ (FeC
o) An alloy powder composed of either ₁₄ B, R _1.11 (FeCo) ₄ B ₄ or the like. The composition of the liquid phase compound powder is, as described above, according to the kind and the amount of the rare earth element of the target composition,
The ratio of the rare earth element contained in the intermetallic compound is changed. However, when R is less than 20% by atom, when the magnet is mixed with the main component-based raw material, the amount of R consumed by partial oxidation of the main component-based R is not sufficiently supplemented, and the liquid during sintering is not sufficiently supplemented. Insufficient phase development. Further, if it exceeds 45 atomic%, the oxygen content is increased, which is not preferable. Further, Co is required to be 3 atomic% or more to form the above compound, and 20 atomic%
If it exceeds, the coercive force will decrease, so the content can be 3 to 20 atomic%, and the balance can be replaced by Fe. Furthermore, when B exceeds 12 atomic%, B is contained in addition to the R ₂ (FeCo) ₁₄ B phase.
It is not preferable because the -rich phase, the Fe-B compound and the like are excessively present. Further, Cu, S, Ni is added to the liquid phase compound powder consisting of the main component alloy powder and / or the intermetallic compound phase of Co or Fe and R containing the R ₃ Co phase and the R ₂ (FeCo) ₁₄ B phase. , Ti, Si, V,
Nb, Ta, Cr, Mo, W, Mn, Al, Sb, G
e, Sn, Zr, Hf, Ca, Mg, Sr, Ba, B
By adding and containing at least one of e, it becomes possible to increase the coercive force, corrosion resistance and temperature characteristics of the obtained permanent magnet. In the above compounded alloy powder, if the average particle size of the main component-based alloy powder is less than 1 μm, the surface area of the alloy powder increases, so the amount of binder added to form a kneaded product is 1: 1 by volume ratio with the alloy powder. It is not desirable because the sintered density of the sintered product after injection molding is reduced to about 95%, which is not preferable.
If the average particle size exceeds, the particle size is too large and the sintered density is 95
%, The average particle size is preferably in the range of 1 to 5 μm, since the density is saturated and the improvement in the density cannot be expected. On the other hand, when the average particle size of the liquid-phase compound powder is less than 8 μm, the reaction with the binder is about the same as that of the alloy powder of a single composition (average particle size of 1 to 5 μm), and the effect of addition of the main component system powder Is hardly seen. Further, when the average particle size of the alloy powder exceeds 40 μm, the reaction with the binder is considerably suppressed, but conversely, the sinterability during sintering is deteriorated, the sintered density is reduced, and at the same time the coercive force is reduced. , The average particle size of liquid phase alloy powder is 8 to 4
0 μm is preferable. The main component alloy powder and the liquid phase compound powder are preferably mixed in a ratio of 70 to 97:30 to 3, and alloy powders having a plurality of compositions according to the magnetic properties can be obtained.

As the method for producing the above-mentioned R-Fe-B type alloy powder, a melting / pulverizing method, an ultra-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, the transition metal powder for general injection molding, such as Fe-based alloy powder or Co, can be obtained by adjusting the average particle size to a preferable range.
Compared with the case of base alloy powder etc., the average particle size is a fraction to 1
The amount is about 1/0, and the addition amount of the binder can be significantly reduced as compared with the addition amount of the binder used in injection molding the transition metal powder.

Resin Coating Coating of the above alloy powder with a resin means the reaction of the R element with water after the binder is kneaded, the gelling stage during molding, and the R element with water during the dehydration treatment after injection molding. It is effective for suppressing the reaction and stabilizing and reducing the residual oxygen amount.
The resin used to coat the alloy powder includes polymethylmethacrylate (PMMA) and polymethylacrylate (PM).
It is preferable to use a methacrylic resin such as A) or a thermoplastic resin such as polypropylene, polystyrene, polyvinyl acetate, polyvinyl chloride, polyethylene or polyacrylonitrile alone or in combination. The amount of resin added is preferably 0.30 wt% or less with respect to the alloy powder, which corresponds to a resin coating film thickness of 50 Å to 200 Å. When it exceeds 0.30 wt%, the residual oxygen amount from the coating resin is increased. It is not preferable because it increases. However, the carbon of the coating resin can be almost completely removed by the debindering treatment in the flowing hydrogen described later, so that the residual carbon amount does not increase even if the addition amount of the coating resin is increased. The coating method is a method commonly called a mechanofusion system or a hybridization system or a method using a ball mill, and the particle diameter of the resin powder for coating is 1000Å to 50
A position of 00Å is preferred. The resin-coated alloy powder is relatively stable in terms of the amount of residual oxygen, and therefore has the advantage that it can be recycled during injection molding. Further, the resin-coated alloy powder has an advantage that it can be injection-molded without adding a lubricant during kneading. Furthermore, the raw material powder is
In the case of the liquid phase compound powder consisting of the main component alloy powder, the intermetallic compound phase of Co or Fe and R containing the R ₃ Co phase, and the R ₂ (FeCo) ₁₄ B phase, etc., the main component alloy powder and / Or liquid phase compound powder can be subjected to the above resin coating, and further, after the main phase alloy powder is coated with the liquid phase compound powder by a mechanofusion system, the above resin coating can also be performed. The same effect as the above can be obtained.

Binder Component In the present invention, as the binder for injection molding, methyl cellulose or agar which causes sol-gel transformation at a predetermined temperature, or a mixture thereof, to which water is added, is used. When methyl cellulose is used alone as a binder, the strength at the time of molding is remarkably reduced when the content is less than 0.05 wt%, and when it exceeds 0.50 wt%, the residual carbon content and the oxygen content are increased to increase the coercive force. Decrease and the magnetic characteristics deteriorate, so 0.05 wt% to 0.50 w
A t% content is preferred in these respects. When agar is used alone, if the content is less than 0.2 wt%, the strength during molding remarkably decreases, and if it exceeds 4.0 wt%, the residual carbon amount and oxygen amount increase and the coercive force decreases. Since the magnetic properties deteriorate, the content of 0.2 wt% to 4.0 wt% is preferable in these respects. When methyl cellulose and agar are used in combination, if less than 0.2 wt%, the strength at the time of molding remarkably decreases and the releasability between the molding die and the molded body deteriorates. 0w
If it exceeds t%, the sintered density after sintering is lowered and the residual carbon amount and oxygen amount are increased, so that the characteristics of the obtained magnet are deteriorated, which is not preferable, so 0.2 wt% to 4.0 wt% is preferable.

In the present invention, water is used together with methyl cellulose and / or agar as a binder, but deoxidized pure water is preferably used in order to suppress the reaction with R. When methyl water is used alone, if the water content is less than 6 wt%, the fluidity at the time of molding will be poor, and short shots will easily occur. Since the sintered density after binding is reduced and the amount of residual oxygen is increased and the magnetic properties are deteriorated, 6 to 16 wt% is most preferable. When the content of water when agar is used alone is less than 8% by weight, the fluidity at the time of molding becomes poor and short shots are likely to occur.
If it exceeds 18 wt%, the substantially total amount of binder increases, so that the sintered density after sintering decreases, and at the same time, the amount of residual oxygen increases and magnetic properties deteriorate, so 8 to 18 wt% is most preferable. When methyl cellulose and agar are used in combination, they are appropriately selected from the range of 6 to 18 wt% in consideration of the ratio of methyl cellulose and agar. Agar
As is generally well known, when heated to around 95 ° C in water, it dissolves into a viscous sol-like substance,
When it is cooled to 0 ° C or lower, it becomes an elastic gel-like substance and solidifies. On the other hand, methyl cellulose dissolves in water and then is heated to about 50 ° C to dissolve and solidify into an elastic gel-like substance, and when cooled to about 35 ° C or less, it becomes a viscous sol-like substance, and becomes an agar binder. Causes a sol-gel reaction opposite to temperature. If both properties are used, considering the agar binder as the main component, the viscosity of the sol state can be improved at a temperature of around 80 ° C. by adding a small amount of methylcellulose. Therefore,
Even a small amount of methyl cellulose can be reduced to a fraction of the amount of the usual agar binder (about 3 wt%). Even if it contains a large amount of water like this,
Since viscoelasticity occurs with a small amount of agar binder, the carbon content in the total binder can be significantly reduced as a binder for injection molding. Furthermore, during degreasing, about 100% of the water in the total binder is evaporated and removed up to 100 ° C, so at the temperature at which the R-Fe-B powder becomes active, oxygen due to a large amount of water has already been released. Therefore, there is an advantage that the oxidation of the R-Fe-B alloy powder can be significantly suppressed.

Further, glycerin, wax emulsion,
If the content of lubricants such as stearic acid and water-soluble acrylic resin is less than 0.10 wt% for both methyl cellulose and agar, the density of the molded article tends to become non-uniform, and if methyl cellulose is used alone it exceeds 0.30 wt%. When using agar alone, if the content exceeds 1.0 wt%, the strength of the molded product will decrease, so 0.10w
Most preferred is t% to 1.0 wt%.

Injection molding conditions The injection conditions vary depending on the amount of binder added, but when methyl cellulose is used alone, the mold temperature is 70.
C. to 90.degree. C. is preferable, and if it is less than 70.degree. C., the solidification may be insufficient at the time of taking out after molding and deformation may occur. If it exceeds 90.degree. When agar is used alone, the mold temperature is preferably 10 ° C to 30 ° C, and 1
If the temperature is lower than 0 ° C, the fluidity is deteriorated, and if the temperature is higher than 30 ° C, the solidification may be insufficient at the time of taking out after molding, which may cause deformation. If the injection molding pressure is less than 30 kg / cm ² , welds will be generated and the molding density will be non-uniform, and bending and waviness will occur after sintering, and if methylcellulose is used alone, it will exceed 50 kg / cm ² . When using agar alone, burrs will be generated if the agar exceeds 70 kg / cm ^2, which is not preferable. Therefore, the pressure is 30 to 70 kg / c.
m ² is preferred. Therefore, when methyl cellulose and agar are used in combination, the mold temperature, injection molding pressure and the like may be appropriately selected from the above range in consideration of the ratio of methyl cellulose and agar. If the magnetic field during injection molding in a magnetic field for obtaining a sintered anisotropic magnet is less than 10 kOe, the orientation is insufficient, so injection molding in a magnetic field of 10 kOe or more is preferable.

Debinding Process In the debinding process, which is a feature of the present invention, a dehydration process is first performed, but the treating method is not particularly limited. For example, in the case of the temperature-rise drying method, the temperature-rise temperature fluctuates depending on the selected amount of pure water added, but at least 20 ° C to 100 ° C.
It is preferable to set the rate of temperature rise to 30 ° C. to 30 to 60 ° C./hour, and if the temperature is less than 30 ° C./hour, the treated product may be oxidized. It is not preferable because the processed product will crack and crack. Especially when the processed product is a small item, at least 20 to 100
It is advisable to set the rate of temperature rise to 40 ° C to 60 ° C / hour,
The dehydration process can be further simplified. Further, most of the water evaporates during the temperature increase up to 100 ° C., so that dehydration treatment in a temperature range exceeding 100 ° C. is unnecessary. In addition, dehydration treatment is continuously performed from low temperature to high temperature, and R-Fe-B
In order to suppress the oxidation of the system alloy powder, a dehydration atmosphere of 1 ×
It is preferably performed in a vacuum of 10 ⁻³ Torr or less. Subsequently, the binder removal treatment is performed, the atmosphere is hydrogen flow, and the temperature rising rate is 100 to 200 ° C./hour.
By holding at 300 to 600 ° C. for 1 to 2 hours, almost all the carbon in the methylcellulose, agar binder and coating resin is decarburized, so that there is an advantage that the treatment time can be significantly shortened as compared with the case of a normal organic binder. is there. Since the alloy powder containing the R element easily absorbs hydrogen, a dehydrogenation treatment step is required after the debinding treatment. In this dehydrogenation treatment, the stored hydrogen is almost completely removed by raising the temperature at a rate of 50 to 200 ° C./hour in vacuum and holding it at 500 to 800 ° C. for 1 to 2 hours. It
After the dehydrogenation treatment, it is preferable to subsequently perform heating and heating to perform sintering, and the temperature rising rate after the temperature exceeds 500 ° C. may be arbitrarily selected, and for example, 100 to 300 ° C./hour or the like. A publicly known temperature rising method taken at the time of binding can be adopted.

Sintering of the molded product after the dehydration treatment and heat treatment conditions after the sintering are appropriately selected according to the selected alloy powder composition, but the production of a conventionally known Fe—B—R system sintered permanent magnet. The conditions may be the same. As preferable sintering and heat treatment conditions after sintering, a sintering step of holding at 1000 to 1180 ° C. for 1 to 2 hours and an aging treatment step of holding at 450 to 800 ° C. for 1 to 8 hours are preferable.

In the present invention, the upper limits of the amount of carbon and the amount of oxygen contained in the sintered body are specified.
This is because if it exceeds ppm and the amount of oxygen exceeds 9000 ppm, the magnetic properties are deteriorated, which is not preferable.

[0021]

According to the present invention, as a binder to be added to the R-Fe-B alloy powder, methyl cellulose or agar which causes a sol-gel transformation at a predetermined temperature or a mixture of them and water added thereto is used. The amount of carbon in the binder is greatly reduced, and the moldability during injection molding is improved, and in the subsequent degreasing process, dehydration and drying treatment and debinding treatment in hydrogen stream are performed to leave almost all of the residual carbon. All the carbon can be removed by a reduction reaction, the amount of residual carbon in the R-Fe-B powder can be greatly reduced, and then dehydrogenation treatment and sintering can be performed.
A three-dimensionally complicated shape sintered magnet having excellent magnetic properties can be obtained. Furthermore, by coating the surface of the R-Fe-B based alloy powder with a resin in advance, it is possible to suppress the reaction between water and the R component in the alloy powder and prevent the oxidation of the alloy powder in each step after kneading. , The residual oxygen amount in the obtained sintered body can be reduced, and almost all of the coated resin can be removed by the binder removal treatment in flowing hydrogen, so the residual carbon amount in the sintered body must be increased. There is no.

[0022]

【Example】

Example 1 As R, a button-shaped ingot alloy produced by high-frequency melting of an alloy ingot having Nd of 16.5 at% and B of 5.7 at% and the balance of Fe and unavoidable impurities in Ar gas by high frequency heating was crushed and then jetted. Fine powder having an average particle size of 3 μm obtained by finely pulverizing with a mill and 0.20 wt% of commercially available methyl cellulose powder as a binder were added and kneaded at room temperature, and further, agar dissolved in warm water at 95 ° C. (fresh water) Foodstuff MA-2000) has a real agar weight of 0.70 wt%
So that the water content is 12 wt%, and at the same time adding glycerin to 0.10%.
wt% was added and kneading was performed at room temperature. The injection temperature of this kneaded pellet was set to 80 ° C., the mold temperature was kept at 25 ° C., and the plate was measured in a magnetic field (15 kO 2) on a 20 mm × 20 mm × 3 mm plate.
Molded in e). This molded body is heated in a vacuum from room temperature to 100
The temperature was raised to 50 ° C at a heating rate of 50 ° C / H, and the temperature was maintained for 1 hour to completely dehydrate and dry, and then from room temperature to 50
The temperature is raised to 0 ° C at a heating rate of 150 ° C / H, and at this temperature, 1
The binder was retained for a period of time for debinding. Further, in order to remove the stored hydrogen, room temperature to 500 ° C in vacuum
The temperature was raised at a temperature rising rate of 150 ° C./H, and held for 1 hour to perform complete dehydrogenation treatment, then further heated and held at 1100 ° C. for 1 hour for sintering. After the completion of sintering, Ar gas was introduced and the temperature was cooled to 800 ° C. at a rate of 7 ° C./min.
An aging treatment was carried out by cooling at 0 ° C / hour and holding at 550 ° C for 2 hours. No cracks, cracks, deformations, etc. were found in the obtained sintered body. The Nd-Fe-B sintered anisotropic magnet of the present invention obtained by this step (invention sample No.
Table 1 shows the magnetic properties of 1) and the measurement results of residual oxygen content and residual carbon content.

Example 2 As R, a button-shaped ingot alloy prepared by melting an alloy ingot having Nd of 16.5 at%, B of 6.2 at% and the balance of Fe and inevitable impurities by high frequency heating in Ar gas was roughly crushed. Then, 0.20 wt of hydrophobic polymethylmethacrylate (PMMA) having an average particle size of 0.15 μm is added to a fine powder having an average particle size of 3 μm obtained by pulverizing with a jet mill.
% Of the added alloy powder was placed in a container of a mechanofusion system, the temperature was maintained at 70 ° C., and the container rotation speed was maintained at a maximum of 1800 rpm for 10 minutes for resin coating (film thickness about 100 Å). . Agar (MA-2000 manufactured by Shimizu Foods) as a binder for this coated alloy powder
2.0 wt% of the powder and water were added so that the water content was 12 wt%, and the mixture was kneaded at 70 ° C. for 20 minutes. Further, 0.20 wt% of glycerin was added during the kneading and the mixture was kneaded for 10 minutes. The kneading pellets were set to an injection temperature of 90 ° C. and a mold temperature of 20 ° C. to obtain 20 mm × 20 mm × 3.
A mm plate was molded in a magnetic field (15 kOe). This molded body is heated from room temperature to 100 ° C in vacuum at a heating rate of 50 ° C / H.
The temperature is raised at room temperature, kept at this temperature for 1 hour, and completely dehydrated and dried.
The temperature was raised at ° C / H and the binder was removed by holding at this temperature for 1 hour. Further, in order to remove the stored hydrogen, the temperature rising rate from room temperature to 500 ° C in vacuum is 150 ° C /
The temperature was raised with H, and the mixture was kept for 1 hour to carry out a complete dehydrogenation treatment, then further heated and kept at 1100 ° C. for 1 hour for sintering. After the completion of sintering, Ar gas was introduced to cool to 800 ° C. at a rate of 7 ° C./minute, then cooled at 100 ° C./hour and held at 550 ° C. for 2 hours to perform an aging treatment. No cracks, cracks, deformations, etc. were found in the obtained sintered body.
Table 1 shows the magnetic characteristics of the Nd-Fe-B sintered anisotropic magnet of the present invention (Sample No. 2 of the present invention) obtained by this step, and the measurement results of the residual oxygen content and the residual carbon content.

Example 3 As R, 10.5 atomic% of Nd, 3.1 atomic% of Pr, and B
6.6 at%, Co at 3.0 at%, the balance Fe and an unavoidable impurity R ₂ Fe ₁₄ B phase and R-rich phase alloy melted by high frequency heating in Ar gas After roughly crushing the alloy-made alloy, coarsely crushing it with a jaw crusher to an average particle size of about 15 μm, and then finely crushing it with a jet mill to obtain a main phase raw material powder with an average particle size of 3 μm, Nd of 19.7 atomic% and Pr0 .8 atom%,
A button-shaped ingot alloy made by melting an alloy lump consisting of Dy1.1 atom%, Co15.0 atom%, B4.5 atom%, and the balance Fe by high frequency heating in Ar gas with a jaw crusher, etc. Liquid-phase raw material powder roughly crushed to 14 μm was blended and mixed in a weight ratio of 90:10. The analytical values of this mixed powder are Nd11.4 atomic% and Pr2.82.
Atomic%, Dy 0.11 atomic%, Co 4.2 atomic%, B
6.4 atomic% and the balance being Fe. This mixed powder and 0.20 wt% of commercially available methyl cellulose powder as a binder are added and kneaded at room temperature. At the same time, water is added so that the water content is 10 wt%, and at the same time, 0.10 wt% of glycerin is added and the room temperature is added. Kneaded in. The injection temperature of the kneaded pellets was set to 25 ° C., the mold temperature was kept at 80 ° C., and the kneaded pellets were molded into a plate of 20 mm × 20 mm × 3 mm in a magnetic field (15 kOe). This molded body is heated in a vacuum from room temperature to 100 ° C at a heating rate of 50 ° C / H, held at this temperature for 1 hour and completely dehydrated and dried, and then heated from room temperature to 500 ° C in a hydrogen stream. The temperature was raised at 150 ° C./H and the temperature was maintained for 1 hour for debinding. Furthermore, in order to remove the stored hydrogen, the temperature is raised from room temperature to 500 ° C. at a heating rate of 150 ° C./H in vacuum,
After holding for 1 hour to perform complete dehydrogenation treatment, it was further heated and held at 1100 ° C. for 1 hour for sintering. After the completion of sintering, Ar gas was introduced to cool to 800 ° C. at a rate of 7 ° C./minute, then cooled at 100 ° C./hour and held at 550 ° C. for 2 hours to perform an aging treatment. No cracks, cracks, deformations, etc. were found in the obtained sintered body. The magnet characteristics and residual oxygen content of the Nd-Fe-B sintered anisotropic magnet of the present invention (Sample No. 3 of the present invention) obtained by this step,
Table 1 shows the measurement results of the residual carbon amount.

Comparative Example The raw material powders shown in Examples 1, 2 and 3 were used, except that the debindering treatment in flowing hydrogen gas and the dehydrogenation treatment step were not carried out, and the temperature rising debinding treatment was carried out in a vacuum. The same conditions and steps were carried out to obtain a sintered anisotropic magnet. The obtained Nd-Fe-B sintered anisotropic magnet of Comparative Example (Comparative Example Sample N
o. Table 1 shows the magnet characteristics of 1 to 3) and the measurement results of residual oxygen content and residual carbon content.

As is clear from Table 1, when the methylcellulose and / or agar binder is used, the amount of carbon in the total binder including water is suppressed to a substantially low level due to the high water content. In addition, since the binder is mainly water, the R-Fe-B alloy powder has already been evaporated at a temperature at which it becomes active.
It is considered that since the alloy powder was coated with resin in about 100 liters in Example 2, oxidation was suppressed considerably, and as a result, the residual carbon amount was significantly reduced. Moreover, it is considered that the magnetic properties were significantly improved by debinding the injection-molded body in a stream of hydrogen gas so that the carbon in the methylcellulose and / or agar or the coating resin could be almost completely decarburized. . At this time, it is understood that if the alloy powder not coated with the resin is oxidized by water, the decarburizing effect by hydrogen is significantly reduced.

[0027]

[Table 1]

[0028]

EFFECTS OF THE INVENTION According to the present invention, as a binder to be added to the R-Fe-B alloy powder, methyl cellulose or agar which causes a sol-gel transformation at a predetermined temperature, or a mixture of them and water is added. By significantly reducing the amount of carbon in the total binder and improving the moldability during injection molding, dehydration and drying treatment in the subsequent degreasing process, and debinding treatment in flowing hydrogen, It is possible to remove almost all of the carbon that is used by the reduction reaction, and the debinding process time can be shortened compared to conventional organic binders. The amount of residual carbon in the sintered body can be reduced by dehydrogenation and sintering. Therefore, the injection molding method according to the present invention can produce a three-dimensionally complicated shape sintered magnet having excellent magnetic characteristics. It can be provided. Furthermore, by coating the resin on the surface of the R-Fe-B based alloy powder before kneading with the binder, water and R in the alloy powder are mixed.
The reaction with the components can be suppressed, the oxidation of the alloy powder in each step after kneading can be prevented, the amount of residual oxygen in the obtained sintered body can be reduced, and the coated resin is debindered in flowing hydrogen. Since almost all can be removed by the method described above, it is possible to provide a sintered magnet having a three-dimensionally complicated shape having excellent magnetic characteristics without increasing the amount of residual carbon in the sintered body.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01F 7/02 C 41/02 G 8019-5E

Claims (4)

[Claims] 1. R-Fe-B alloy powder (R is at least one of rare earth elements containing Y) is added with methyl cellulose and / or agar which causes a sol-gel reaction as a binder at a predetermined temperature and water. After kneading, a molded body is formed by injection molding, and the molded body is dehydrated, then debindered in flowing hydrogen, and then dehydrogenated and sintered. Fe-
A method for manufacturing a B-based sintered magnet. 2. After coating the surface of the raw material fine powder with a resin,
The method for producing an R-Fe-B system sintered magnet according to claim 1, wherein the method is injection molding. 3. A binder containing glycerin as a lubricant,
At least one of stearic acid, emulsion wax, and water-soluble acrylic resin is 0.1 to 1.0 wt% and water is 6 to
The method for producing an R-Fe-B system sintered magnet by the injection molding method according to claim 1 or 2, wherein a composition containing 18 wt% is added as a binder for the magnetic powder. 4. The amount of carbon contained in the sintered body is 700 ppm
The method for producing an R-Fe-B system sintered magnet by the injection molding method according to claim 1, claim 2 or claim 3, wherein the oxygen content is 9000 ppm or less.