JPH07283016A - Magnet and production thereof - Google Patents

Abstract

PURPOSE:To provide an R-T-B based anisotropic magnet having high coercive force, remanent magnetic flux density and dimensional accuracy along with an R-T-B based anisotropic magnet excellent significantly in corrosion resistance. CONSTITUTION:A molding alloy comprising R (rare earth element), T (Fe, or at least one kind of Co, Ni or Cu and Fe) and B and containing a phase composed substantially of R2T14 is fused into an alloy rich in R and a molten allay is poured into a molted item of molding alloy powder thus producing a magnet. Corrosion resistance is enhanced significantly by a magnet containing a granular main phase composed substantially of R2T14B phase and a subphase surrounding the main phase wherein the subphase contains an R3Co phase and/or an RCu phase with the ratio of the subphase being set in the range of 20-40vol.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth magnet having good dimensional accuracy and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a rare earth magnet having high performance, an Sm-Co type magnet manufactured by powder metallurgy has an energy product of 32M.
GOe's are in mass production. In recent years, Nd ₂ Fe
₁₄ RTB magnets such as B magnets (T is Fe or Fe
And Co) were developed, and a sintered magnet is disclosed in JP-A-59-46008. R-T-B magnets are cheaper in raw material than Sm-Co magnets. RT
-For the production of B-based sintered magnets, the conventional Sm-Co-based powder metallurgy process (melting → master alloy casting → ingot coarse crushing →
Fine crushing → molding → sintering → magnet) can be applied.

In the R-T-B system magnet, in addition to the sintered magnet,
Bonded magnets in which magnet powder is bonded with a resin binder or a metal binder are also in practical use. Since the dimensions of the bonded magnet are almost maintained during molding, the dimensional accuracy is high and no shape processing is required after manufacturing. However, since the industrialized RTB-based bonded magnet uses polycrystalline particles that have been rapidly solidified by a single roll method or the like as disclosed in Japanese Patent Publication No. 1-54457, it isotropic. It becomes a magnet (maximum energy product 5-10 MGOe).
As magnetic powders for anisotropic bonded magnets, as shown in Japanese Patent Publication No. 4-20242, a rapidly solidified powder is uniaxially compressed by hot pressing to densify it, and then uniaxially plastically worked at high temperature. It has been proposed that the resulting anisotropic green compact is pulverized by applying (die up set) to make it anisotropic. However, this anisotropy process is time-consuming and significantly increases the production cost. Also,
High temperature demagnetization occurs during hot pressing and die up setting. It is possible to use pulverized powder of anisotropic sintered magnet for the bonded magnet, but when the sintered body is pulverized, the coercive force and the squareness ratio are extremely deteriorated, so that the characteristics as a magnet cannot be obtained. In addition to this, crushed powder of a magnet body produced by a casting / hot rolling process has been proposed as a raw material for anisotropic bonded magnets, but as with the case of crushing a sintered body, deterioration of coercive force due to crushing occurs. Because it is large, it is not a practical material.

As described above, it is extremely difficult for a bonded magnet to anisotropy while maintaining a high coercive force. Moreover, it is difficult to obtain a high residual magnetic flux density because the ratio of the magnet powder to the entire magnet is limited.

On the other hand, in the RTB sintered magnet,
Since powder consisting of substantially single crystal particles is molded in a magnetic field, an anisotropic magnet can be easily obtained, and since no binder is used, high characteristics can be obtained. However, in the sintering method, the molded body significantly shrinks during the sintering reaction, and the shrinkage is non-uniform, so that it is difficult to maintain the dimensional accuracy of the molded body. This shrinkage varies depending on the degree of orientation of particles in the molded body, variations in density, and the like. In an anisotropic sintered magnet, the contraction rate differs between the direction of the easy axis of magnetization and the direction orthogonal thereto. For example, when the density of the molded body is 4.3 g / cm ³ , the density after sintering is 7.55 g / cm ^3.
The contraction rate reaches about 22% in the direction of the easy axis of magnetization and about 15% in the direction perpendicular to it, reaching ³⁰ cm3 as a whole.
It shrinks about 40% by volume.

Generally, if the pressure at the time of molding the magnet powder is increased, the density of the molded body is increased, and the shrinkage rate at the time of sintering is reduced accordingly, but the dimensional accuracy generally required. The shrinkage rate and the amount of deformation do not decrease so as to satisfy the above condition. This tendency is particularly remarkable in radial anisotropic ring magnets and polar anisotropic ring magnets.In these conventional anisotropic ring magnets, the inner peripheral surface, the outer peripheral surface and the upper surface are irrespective of the molding pressure. Since it is necessary to grind the lower surface, the productivity is reduced and the magnet material is lost due to the grinding, resulting in an increase in cost.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an R-T-B type anisotropic magnet having a high coercive force and a residual magnetic flux density and good dimensional accuracy, and another object. Is to provide an R-T-B type anisotropic magnet having extremely good corrosion resistance.

[0008]

These objects are achieved by the present invention described in (1) to (21) below. (1) contains R (R is at least one rare earth element including Y), T (T is Fe, or at least one of Co, Ni and Cu and Fe) and B a molded body alloy containing substantially phase consisting R ₂ T ₁₄ B, wherein the R, than R ₂ T ₁₄ B using the R-rich infiltration alloy, the molten infiltrant alloy, A method for producing a magnet, comprising infiltrating a powder of an alloy for a molded body into a molded body to obtain a magnet. (2) The method for producing a magnet according to the above (1), wherein the melting point of the alloy for infiltration is 1000 ° C. or less. (3) The method for producing a magnet according to the above (1) or (2), wherein the melting point of the alloy for infiltration is lower than the heat shrinkage start temperature of the compact. (4) The method for producing a magnet according to any one of the above (1) to (3), wherein the infiltrating alloy is heated by raising the temperature of the compact and the infiltrating alloy in contact with each other. (5) The method for producing a magnet according to any one of (1) to (4) above, wherein the density of the molded body is 4.0 g / cm ³ or more. (6) The method for producing a magnet according to any one of the above (1) to (5), which produces a magnet having a relative density of 95% or more. (7) The alloy for a molded body according to any one of the above (1) to (6), wherein the alloy contains 26 to 38% by weight of R, 0.9 to 3% by weight of B, and the balance is substantially T. Production method. (8) The method for producing a magnet according to any one of the above (1) to (7), wherein Nd + Pr accounts for 50% by weight or more of R of the alloy for molded body. (9) The method for producing a magnet according to any one of (1) to (8) above, wherein Fe + Co accounts for 50% by weight or more of T. (10) The powder of the alloy for compacts has an average particle size of 0.1 to 5
The method for producing a magnet according to any one of (1) to (9), wherein the magnet has a diameter of 0 μm. (11) The method for producing a magnet according to any one of (1) to (10) above, wherein the infiltration alloy contains 40 to 99% by weight of R. (12) The balance of the alloy for infiltration is substantially M (M is Fe,
The method for producing a magnet according to (11) above, which is at least one of Co, Ni, Cu, Al, Sn, Ga, and Ag). (13) At least one of B, Si and C is contained in place of a part of M, and the total content of these is 3 of the infiltration alloy.
The method for producing a magnet according to the above (12), which is not more than wt%. (14) The method for producing a magnet according to any one of (1) to (13) above, wherein the molded body is molded in a magnetic field. (15) The method for producing a magnet according to any one of (1) to (14), wherein the formed body after infiltration is heat-treated at a temperature higher than the melting point of the alloy for infiltration. (16) The method for producing a magnet according to (15), wherein the holding temperature during the heat treatment is 800 ° C. or higher. (17) Substantially R ₂ T ₁₄ B phase (R is at least one rare earth element including Y, and T is Fe or C
o, at least one of Ni and Cu, and Fe), and a sub-phase that is R richer than R ₂ T ₁₄ B and surrounds the main phase. R
< ₃ > A magnet containing a Co phase and / or an RCu phase, wherein the proportion of the subphase in the magnet is 20 to 40% by volume. (18) At least a part of Co in the R ₃ Co phase and RC
The magnet according to (17) above, wherein at least part of Cu in the u phase is replaced with Fe. (19) At least a part of Co in the R ₃ Co phase is replaced by Cu, and at least a part of Cu in the RCu phase is Co.
The magnet of (17) or (18) above, which is replaced by. (20) The sub-phase is an R ₃ (Co _1-wx Fe _w Cu _x ) phase (0.01 ≦ w ≦ 0.3, 0.01 ≦ x ≦ 0.3) and R (Cu _1-yz Co _y Fe _z ) phase (0.01 ≦ y ≦
0.3, 0.01 ≦ z ≦ 0.3), the content of these phases in the magnet is 1 to 30% by volume, respectively, and the total content of these phases in the magnet is 20 to 4
The magnet according to (17) above, which is 0% by volume. (21) 30 to 60% by weight of R and 0.3 to 6% by weight of B
Including the magnets of (17) to (20) above.

[0009]

Actions and Effects It has been reported in various papers that the coercive force of the Nd ₂ Fe ₁₄ B system sintered magnet depends on the existence of the Nd-rich phase in the grain boundaries. Therefore, the crystal grains composed of the Nd ₂ Fe ₁₄ B phase are
It is important to sinter so that the d-rich phase is uniformly covered, that is, to uniformly disperse the Nd-rich phase in the sintered magnet.

In the present invention, the R-rich infiltrating alloy is infiltrated into the powder compact having a phase substantially consisting of R ₂ T ₁₄ B. The infiltration in this case means that the molten alloy is impregnated into the compact. Since the liquid phase infiltration alloy has extremely good wettability with respect to the powder of the alloy for compacts, it fills the voids between the particles in the compact in a short time. Therefore, the R-rich phase, which is important for generating the coercive force, is not unevenly distributed in the magnet, and a high coercive force can be obtained. Moreover, the density of magnets produced by infiltration is almost equal to the density of magnets that are completely sintered. In other words, it is possible to obtain a magnet having almost no open holes leading to the outside of the magnet. Therefore, similar to the sintered magnet, a sufficient rust preventive effect can be obtained by Ni plating or resin coating.

Since the dimension of the molded body hardly changes before and after the infiltration, it is not necessary to perform grinding for adjusting the dimension after the infiltration. Further, even when a molded product molded in a magnetic field is used, a difference in shrinkage ratio due to anisotropy is hardly generated, so that cracks and breaks of the magnet can be prevented.

The magnet produced according to the present invention has a relatively high ratio of the R-rich grain boundary phase (sub-phase), so that the conventional R-
Although the magnetic properties are lower than those of the TB high-density sintered magnet,
Sm-Co based bonded magnet {(BH) max = approx. 15MG
It is higher than Oe}. Moreover, the R-T-B system magnet is S
The raw material is less expensive than the m-Co magnet. Therefore,
The magnet manufactured according to the present invention is suitable as a substitute for the Sm-Co based bonded magnet that has been used in applications that conventionally require high dimensional accuracy.

[0013] magnet of the present invention includes a main phase of particulate consisting R ₂ T ₁₄ B phase, an R-rich than R ₂ T ₁₄ B, and a sub-phase surrounding the main phase. During this subphase, R ₃ Co
Phases and / or RCu phases are included. These phases improve the corrosion resistance of the magnet. The magnet of the present invention has a high proportion of the sub-phase, and since most of the sub-phase can be constituted by these phases, the corrosion resistance becomes extremely good. Such a magnet can be easily manufactured by appropriately selecting the composition of the infiltration alloy in the manufacturing method of the present invention described above.

By the way, in Japanese Patent Laid-Open No. 3-80508, in a method of manufacturing an RFeB magnet by powder metallurgy, 400-900 ° C. after press molding of magnet powder.
It is made into a porous sintered body in the temperature range of
_{d x Fe 1-x (x} = 0.65~0.85) a method of immersing a predetermined time is disclosed. This method aims at suppressing the deformation after sintering due to the anisotropy of thermal contraction due to the magnetic field orientation. However, when the molded body is heat-treated at 400 to 900 ° C. as in the method described in the publication, the magnetic characteristics deteriorate, and the magnetic characteristics equivalent to those of the magnet according to the present invention cannot be obtained. Moreover, when the heat treatment is performed at 800 ° C. or higher as in the example of the publication, the sintering proceeds and the shrinkage ratio cannot be reduced as in the present invention.

In addition, low melting point metals (Al, In, Bi,
In a metal-bonded magnet using a binder such as Sn, Zn, Pb or the like or an alloy containing them, the particles having a coercive force usable as a magnet are simply bonded with a low melting point metal. . Since the pulverized powder of Nd ₂ Fe ₁₄ B-based casting alloy exhibits a coercive force of about 1 kOe or less, it cannot be magnetized by the same method as the conventional metal bonded magnet.

[0016]

Specific Structure The specific structure of the present invention will be described in detail below.

In the present invention, a magnet is manufactured by using a molded body alloy and an infiltration alloy, and infiltrating the molten infiltration alloy into a molded body of powder of the molded body alloy.

<Alloy for molded body> Alloy for molded body is R (R
Is at least one rare earth element including Y), T
(T is Fe or at least one of Co, Ni and Cu and Fe) and B, and comprises a phase consisting essentially of R ₂ T ₁₄ B. The specific composition of the alloy for molded body may be appropriately determined in consideration of the composition of the alloy for infiltration according to the target magnet characteristics, but preferably,
It is assumed that R is 26 to 38% by weight, B is 0.9 to 3% by weight, and the balance is substantially T. More preferably, R is 27 to 33% by weight and B is 1.0 to 1. 5% by weight is included, and the balance is substantially T.

R is Y, lanthanide and actinide, but is preferably Nd to obtain a high residual magnetic flux density.
And / or Pr is used. In addition to these, Tb, D
y, La, Ce, Gd, Er, Ho, Eu, Pm, T
You may use 1 or more types, such as m, Yb, and Y. Nd + Pr
Preferably accounts for 50% by weight or more, and particularly 80% by weight or more of R of the alloy for molded bodies. A mixture of misch metal or the like can be used as the raw material of the rare earth element. If the R content in the molded alloy is too low, a phase rich in iron precipitates and high coercive force cannot be obtained, and if the R content is too high, high residual magnetic flux density cannot be obtained.

In the R ₂ T ₁₄ B system sintered magnet, the R-rich phase becomes a liquid phase and flows, and the sintering reaction proceeds. Therefore, the raw material powder is generally made R-rich rather than R ₂ T ₁₄ B. . In the present invention, since the R-rich infiltration alloy is infiltrated into the compact of the compacted alloy powder, the R-rich phase for generating coercive force is formed around the particles in the compact.
It is not necessary that the composition of the molded alloy be R-rich than R ₂ T ₁₄ B. On the contrary, if the R ratio of the alloy for a molded body is too high, the heat shrinkage start temperature of the molded body becomes low, and the shrinkage slightly increases during the infiltration.

If the B content in the alloy for compacts is too low, a high coercive force cannot be obtained, and if the B content is too high, a high residual magnetic flux density cannot be obtained.

In the alloy for compacts, Fe + Co has a T content of 50.
It is preferable that it accounts for at least 90% by weight, especially 90% by weight. If the ratio of Fe + Co in T is too small, the saturation magnetization becomes small when magnetized, and a high residual magnetic flux density cannot be obtained.

In addition, in the alloy for compacts, Fe / (Fe +
Co) is preferably 70% by weight or more. If the amount of Fe is small, a high residual magnetic flux density cannot be obtained when magnetized.

In addition to the above elements, for improving coercive force and corrosion resistance, Al, C, Si, Cr, Mn, Mg, N
Elements such as b, Sn, W, V, Zr, Ti and Mo may be added, but if the addition amount exceeds 6% by weight, the reduction of the residual magnetic flux density becomes a problem.

In addition to these elements, the magnet may contain unavoidable impurities such as oxygen and trace additives.

In the present invention, since the alloy powder for compacts is compacted while being oriented in a magnetic field, it is preferable that the grain size is such that it becomes single crystal grains when pulverized, but it is polycrystalline grains. However, since it is sufficient that the crystal grains are oriented within the grains, the average crystal grain size can be selected from a wide range of, for example, about 3 to 600 μm.

The average particle size of the powder of the alloy for compacts is preferably 0.1 to 50 μm, more preferably 1 to 10 μm.
Is. If the average particle size is too small, it is difficult to increase the density of the molded body and it is difficult to obtain a high residual magnetic flux density.
Since the amount of oxygen in the powder is large, it becomes difficult to obtain a high coercive force depending on the balance with the amount of the infiltration alloy used. On the other hand, if the average particle diameter is too large, the proportion of polycrystalline particles increases and it becomes difficult to obtain a high residual magnetic flux density.

The method for producing the powder of the alloy for compacts is not particularly limited, and any method such as a method of pulverizing a cast alloy by hydrogen absorption pulverization or a reduction diffusion method may be used. It is also possible to use powder that has been pulverized by the above method, or grinding scraps of a sintered magnet. By crushing or grinding a sintered magnet anisotropy by magnetic field orientation, it is possible to obtain polycrystalline particles consisting of oriented small crystal grains, so that a magnet with high residual magnetic flux density and high coercive force can be obtained. . Further, since the grinding dust has a large oxygen content, the heat shrinkage start temperature of the formed compact becomes high. Therefore, even when an infiltration alloy having a high melting point is used, the shrinkage ratio can be reduced, and the degree of freedom in material selection is increased.

<Infiltration Alloy> The infiltration alloy contains R,
It is an alloy richer in R than R ₂ T ₁₄ B.

During infiltration, it is preferable that the temperature of the compact is about the same as that of the alloy for infiltration, so the compact is also heated. Therefore, the melting point of the infiltration alloy may be such that the shrinkage rate of the molded body falls within a desired range when the temperature rises to the melting point. Specifically, it may be experimentally determined, but when the above-mentioned alloy for molded body is used, the temperature is preferably 1000 ° C. or lower, more preferably 700 ° C. or lower.

When it is desired to reduce the shrinkage rate of the molded body significantly, an infiltration alloy having a melting point lower than the heat shrinkage start temperature of the molded body is used. The thermal contraction start temperature of the molded body of the powder for a molded body is a temperature at which the molded body physically starts shrinking due to the appearance of a liquid phase, and the thermomechanical analyzer (Ther
momechanical Analyzer). In the above-mentioned powder compact of the alloy for compacts, the heat shrinkage start temperature varies depending on the composition, temperature rising rate, etc.
The temperature is about 0 to 1050 ° C, and for example, when the temperature is increased at a constant rate of 5 to 10 ° C / min, the heat shrinkage start temperature can be set to 800 ° C or more if the R content is set to 29% by weight or less.

The melting point of the infiltration alloy is preferably 300 ° C.
As described above, more preferably at 400 ° C. or higher. If the melting point is too low, the amount of residual carbon in the magnet will increase and the coercive force will decrease due to the relationship with the decomposition temperature of organic substances such as wax used as a lubricant or binder during molding. In addition, infiltration begins before the adsorbed water of the alloy powder for compacts is completely removed, which also leads to a decrease in coercive force.

R ₂ T ₁₄ B (when R = Nd and T = Fe, 26.7 wt% Nd-72.3 wt% Fe-1.
When an alloy for a molded body having a composition substantially equal to 0 wt% B) is used, the heat shrinkage initiation temperature is not substantially observed,
Measurement may be difficult.

The composition of the infiltration alloy may be determined so that the required melting point can be obtained, and is not particularly limited.
In addition to R, M (M is Fe, Co, Ni, Cu, Al,
Sn, Ga and / or Ag). As R, at least one of Nd, Pr, Dy and Ce, particularly at least one of Nd, Pr and Dy is preferable. As M, Fe, Co, C
More preferred is at least one of u and Al, particularly at least one of Fe, Co and Cu.

The R content of the infiltration alloy is preferably 40
˜99% by weight, more preferably 60 to 90% by weight. If R is too small, it becomes difficult to lower the melting point, and the effect of improving the coercive force of the magnet becomes insufficient. If the amount of R is too large, or if R alone, the melting point will be high. The balance is preferably substantially M as described above. However, instead of a part of M, B, S
At least one of i, C and other elements may be added. However, the total content of these elements is preferably 3% by weight or less of the infiltration alloy. In addition to these, unavoidable impurities such as oxygen and trace addition elements may be contained.

The infiltration alloy may be in a bulk form or in a powder form. However, since the infiltration alloy has a large R content and is easily oxidized, a bulk form or a coarse powder is preferably used. To use.

The method for producing the alloy for infiltration is not particularly limited,
Any of a casting method and a liquid quenching method may be used.

<Molding> The powder of the alloy for a molded body is usually compression-molded in the same manner as the magnet powder molding at the time of producing a sintered magnet, but in the present invention, injection molding or extrusion molding may be performed. . In order to manufacture an anisotropic magnet, it is formed in a magnetic field to orient the powder of the alloy for compacts.

The density of the molded product is not particularly limited, but the higher the density of the molded product is, the higher the residual magnetic flux density is. Therefore, the density of the molded product is preferably 4.0 g / cm ³ or more, more preferably 4.5 g. / cm ³ or more.

After infiltration, regardless of the density of the compact,
Usually, the relative density is 95% or more. The relative density in this case is the ratio of the density of the actually manufactured magnet to the density of the magnet when it is assumed that all the pores in the molded body are filled with the infiltration alloy.

The molding pressure at the time of compression molding is not particularly limited and may be appropriately determined so that a molded product having a desired density can be obtained.

When injection molding or extrusion molding is carried out, it is preferable to add a binder to the powder for molding in order to improve the shape retention. The binder may be any of those normally used for powder magnets, powder cores, etc. For example, wax or the like can be preferably used.

The magnetic field strength during molding is usually 10 kOe or more, preferably 15 kOe or more. The magnetic field applied during molding may be a DC magnetic field or a pulsed magnetic field, or may be a combination of these. The present invention can be applied to a so-called transverse magnetic field forming method in which a pressure applying direction and a magnetic field applying direction are substantially orthogonal to each other, and a so-called longitudinal magnetic field forming method in which a pressure applying direction and a magnetic field applying direction are substantially coincident with each other.

The molding is usually carried out at 50 ° C. or lower in order to avoid oxidation of the powder.

<Infiltration> Infiltration is carried out by heating the alloy for infiltration to its melting point or higher.

The heating means for the infiltration alloy is not particularly limited,
Either an electric furnace or a high-frequency heating furnace may be used, but it is preferable to use a means capable of simultaneously heating the molded body, for example, an electric furnace. By heating the compact to a temperature equivalent to that of the alloy for infiltration, it is possible to uniformly infiltrate the compact.

The specific infiltration method is not particularly limited. For example, any of a method of immersing the molded body in the melt of the alloy for infiltration, a method of pouring the melt into the molded body, a method of immersing a part of the molded body in the melt and sucking it into the molded body, etc. Good. However, it is preferable to use a method of melting the infiltration alloy in a state where the compact and the infiltration alloy are in contact with each other. Specifically, it is preferable to place an infiltration alloy on the compact and melt it. You may use the method of immersing the molded body in the melt of the infiltration alloy, but in this case, since the infiltration alloy is solidified on the entire surface of the molded body after pulling up from the melt, It is necessary to provide a step of removing by grinding.
On the other hand, if a required amount of the infiltration alloy is placed on the compact and melted, almost no infiltration alloy remains on the surface of the compact after the infiltration, or there is a slight amount of the infiltration alloy on the upper surface of the compact. Since it only remains, the process can be simplified. Moreover, in this method, since the infiltration alloy does not come into contact with anything other than the compact during melting, it is possible to prevent impurities from entering.

When the method of placing the infiltration alloy on the compact is used, at least the amount of the infiltration alloy required to fill the voids in the compact may be used, but it is practically slightly excessive. Is used. The porosity of the molded body can be calculated from the composition of the alloy for molded bodies and the molded body density.

The form of placing the infiltration alloy on the molded body is not particularly limited, and for example, a coarse powder or a crushed piece of an ingot may be weighed in a predetermined amount and placed, but preferably the infiltration alloy is used. Coarse powder of the alloy is molded and placed. By using the infiltrating alloy as a molded body, the usage amount can be controlled accurately and easily. In this case, it is preferable that the infiltrated alloy compact has a lower surface having substantially the same shape and substantially the same size as the upper surface of the compacted alloy powder compact. For example, when producing a ring-shaped magnet, the infiltrated alloy compact is also ring-shaped. Thereby, the infiltration into the molded body can be performed more uniformly. The powder of the alloy for compact and the coarse powder of the alloy for infiltration may be integrally molded in the same manner as the two-color compaction.

Since the liquid phase infiltrating alloy has extremely good wettability with respect to the alloy powder for compacts, it quickly permeates into the compact after melting. Therefore, if only infiltration, it is not necessary to maintain the temperature after heating to above the melting point, but in order to increase the coercive force and the residual magnetic flux density, continue to raise the temperature after infiltration and It is preferable to carry out a heat treatment in which the temperature is maintained above the melting point of the alloy. The holding temperature in this heat treatment varies depending on the melting point of the infiltration alloy, but is preferably 800 ° C. or higher, more preferably 90 ° C. or higher.
It is 0 ° C or higher. However, the main phase of the magnet is R ₂ T ₁₄ B
In order to suppress the grain growth of the phase, the holding temperature is 1100.
It is preferable that the temperature is not higher than ° C. In this heat treatment, the time for maintaining the temperature is preferably 0.5 to 8 hours. If this time is too short, the effect of the heat treatment becomes insufficient, and if it is too long, the crystal grain growth of the R ₂ T ₁₄ B phase becomes remarkable. Even if such heat treatment is performed, the molded body after infiltration hardly shrinks.

The heat treatment may be performed after the temperature is once lowered after the infiltration.

An aging treatment may be performed after the infiltration or after the above heat treatment. The aging treatment is a heat treatment having a lower holding temperature than the above heat treatment, and the aging treatment can improve the coercive force. The holding temperature during the aging treatment is preferably 400 to 800 ° C, more preferably 500 to 700 ° C.
Is. The temperature holding time is preferably 0.5 to 4
It's time. The aging treatment is performed after the heat treatment and after cooling, but the effect equivalent to the aging treatment can be obtained by gradually cooling in the temperature decreasing process of the heat treatment.

The infiltration and the subsequent heat treatment are preferably performed in a vacuum or in an inert gas atmosphere such as Ar gas in order to prevent the infiltration alloy and the compact from being oxidized.

<Magnet> The magnet manufactured in this manner has a main phase substantially composed of R ₂ T ₁₄ B and a sub-phase surrounding the main phase. The sub-phase is an R-rich phase having a higher R ratio than R ₂ T ₁₄ B. The ratio of the sub-phase in the magnet varies depending on the density of the compact, but is usually 20 to 40% by volume. When an infiltration alloy containing Co and / or Cu is used, the subphase contains an R ₃ Co phase and / or an RCu phase, and depending on the composition of the infiltration alloy, the subphase is substantially It consists of only the phase.

When the infiltration alloy contains Fe, at least a part of Co in the R ₃ Co phase and at least a part of Cu in the RCu phase are replaced with Fe, and Even if the alloy did not contain Fe,
Due to diffusion from the main phase, such substitution with Fe is usually observed.

When the infiltration alloy contains Co and Cu, the R ₃ Co phase and the RCu phase are contained, and at least a part of Co in the R ₃ Co phase is replaced with Cu. , At least a part of Cu in the RCu phase is C
replaced by o.

The R ₃ Co phase and the RCu phase show the effect of improving the corrosion resistance of the magnet, and the effect of the RCu phase is higher.
Then, as the R ₃ Co phase, R ₃ (Co _1-wx Fe _w Cu
_x ) phase (0.01≤w≤0.3, 0.01≤x≤0.
3) and R (Cu _1-yz Co _y as RCu phase)
Fe _z ) phase (0.01 ≦ y ≦ 0.3, 0.01 ≦ z ≦
When 0.3) is included, the effect of improving the corrosion resistance is significantly enhanced. The content of each of these phases in the magnet is preferably 1 to 30% by volume. The total content of these phases in the magnet is 20-40% by volume.
Is preferred. That is, it is preferable that the sub-phase is substantially composed of only these phases. Even in such a case, the sub-phase includes other phases such as the R oxide phase, but the ratio of these other phases in the magnet is about 5% by volume or less. The diameter of the R ₃ Co phase or RCu phase appearing in the magnet cross section is usually 50 μm or less.

The composition of the magnet is determined by the composition of the alloy for compacts, the composition of the alloy for infiltration, the ratio of these alloys, etc. Preferably, R is 30 to 60% by weight and B is 0.
3 to 6% by weight, more preferably R is 35
.About.45% by weight and B in an amount of 0.6 to 1.3% by weight. The balance is T derived from the alloy for compacts and M derived from the alloy for infiltration.

<Others> In order to improve the corrosion resistance, the magnet may be provided with an anticorrosion coating by electrodeposition coating of a resin, electroless plating and / or electrolytic plating, if necessary.

The present invention is particularly suitable for manufacturing thin anisotropic ring-shaped magnets and anisotropic plate-shaped magnets which require dimensional accuracy.

[0061]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

<Example 1> First, an alloy ingot for a molded body was subjected to high frequency melting in an Ar gas atmosphere and cast.
The composition of the ingot was (30Nd-3Dy) -1.2B-balance Fe in weight percentage. The average grain size of this alloy ingot is 120
It was μm. The ingot was mechanically pulverized in a nitrogen gas atmosphere and then pulverized with a jet gas in a nitrogen gas stream to obtain an alloy powder for a molded body having an average particle diameter of 4.5 μm.

This alloy powder for compacts was compression-molded in a magnetic field of 15 kOe by applying a pressure of 6 t / cm ^{2 in} a direction orthogonal to the magnetic field direction, and a compact having a cubic shape of 10 mm × 10 mm × 10 mm was formed. Got The density of this molded body is 5.20 g / cm ^3.
Met. The heat shrinkage start temperature of this molded product is 650 to 7
It was in the range of 00 ° C.

Next, an alloy for infiltration was manufactured by arc melting in an Ar gas atmosphere. The composition of the alloy for infiltration was 85Nd-15Fe in weight percentage. The melting point of the infiltration alloy was 650 ° C.

Next, on the compact of the alloy powder for compact,
An infiltration alloy crushed into a few millimeters square was placed. The amount of the alloy for infiltration used was increased by 3% by weight of the amount of voids in the molded body calculated. These were heated to 950 ° C. in a vacuum in an electric furnace and held for 2 hours. The alloy for infiltration is
It melted around its melting point and soaked into the molded body. After cooling
Aging treatment was performed by raising the temperature again and holding it at 620 ° C. for 1 hour to obtain magnet sample No. 1.

The shrinkage ratio of the magnet sample No. 1 with respect to the molded body was 2.5% in the magnetic field direction during molding and 1.4% in the direction perpendicular to the magnetic field direction. Magnet density is 7.40 g / cm
³ (98% or more of the theoretical density), which was equivalent to that of a sintered magnet. The magnetic characteristics of sample No. 1 have a residual magnetic flux density (Br) of 9.1 kG and a coercive force (HCJ) of 12.5 kO.
e, the maximum energy product {(BH) max} was 19.7 MGOe.

Example 2 A magnet sample was manufactured in the same manner as in Example 1 except that the composition of the infiltration alloy was as shown in Table 1. All of the infiltration alloys shown in Table 1 are 950 ° C.
It melts up to and including Sample No. 2-8, 2-
Except for 10, 2-12 and 2-13, the melting point of the infiltration alloy was 700 ° C or lower. The same measurements as in Example 1 were performed on these samples. The results are shown in Table 1.

[0068]

[Table 1]

Example 3 A magnet sample was manufactured in the same manner as in Example 1 except that the composition of the alloy for compacts was as shown in Table 2. The heat shrinkage initiation temperatures of the alloy powder compacts shown in Table 2 were all 650 ° C or higher. The same measurements as in Example 1 were performed on these samples. The results are shown in Table 2.

[0070]

[Table 2]

Example 4 A magnet sample was manufactured in the same manner as in Example 1 except that the molding pressure was changed to the value shown in Table 3. The same measurement as in Example 1 was performed on each sample. The results are shown in Table 3.

[0072]

[Table 3]

In each of the above examples, the composition of each sample contained 30 to 60% by weight of R and 0.3 to 6% by weight of B, and the relative density of each sample was 98% or more. there were.

<Structure of Sub-Phase> Regarding the magnet samples shown in Table 4, the structure of the sub-phase was examined. Sample No. 5 in Table 4
Nos. 1, 5-2 and 5-3 were produced in the same manner as Sample No. 1 except that the alloys for infiltration shown in Table 4 were used.

Each of the samples in Table 4 had a main phase derived from the powder of the alloy for compacts and a subphase derived from the alloy for infiltration. Table 4 shows the volume ratios of the R ₃ Co phase, the RCu phase, the R phase and the phases other than these contained in the sub phase. All of these volume ratios are volume ratios to the entire sample. In addition, Table 4 also shows the volume ratio of the entire subphase in the sample. These volume ratios were calculated from the area of each phase measured using a scanning electron micrograph (composition image) of a sample cross section. A cross-sectional photograph of Sample No. 2-18 is shown in FIG. In FIG. 1, the black region is the main phase, the gray region is the RCu phase, and the white region is R ₃
It is a Co phase and an R oxide phase. Sample No. 2-1
The R ₃ Co phase and the RCu phase appearing in the cross sections of 1, 2-18 and 5-1 had a diameter of 20 μm or less. SEM-EDX and EPMA were used for identification of each phase.

For each sample shown in Table 4, a pressure cooker test (120 ° C.
(00% RH), and after 100 hours, the amount of change in weight per unit surface area of the sample was determined. The results are shown in Table 4.
Shown in. In Table 4, the sign of the amount of change in weight is negative because the main phase was dropped due to intergranular corrosion near the sample surface.

[0077]

[Table 4]

The "other" phase in the subphases shown in Table 4 means
Although it is mainly an Nd oxide phase, Sample No. 1-1 was mainly composed of an NdFe phase.

As shown in Table 4, sample Nos. 2-11 and 2-1 having both R ₃ Co phase and RCu phase.
It can be seen that in Nos. 8 and 5-1, the amount of change in weight is extremely small and the corrosion resistance is extremely good. On the other hand, sample Nos. 5-2 and 5 containing only the R ₃ Co phase without containing the RCu phase
-3, the corrosion resistance is low, and in Sample No. 1-1 containing neither R ₃ Co phase nor RCu phase,
Corrosion resistance is extremely low.

Sample Nos. 2-11, 2-18,
In No. 5-1, part of Co in the R ₃ Co phase was replaced with Cu and Fe, and part of Cu in the RCu phase was replaced with Co and Fe. Specifically, the composition of the R ₃ Co phase is _{w≈0.25, x≈0.23 in} R ₃ (Co _1-wx Fe _w Cu _x ), and the composition of the RCu phase is R (Cu _{1 -yz Co y Fe z) y ≒} 0.10 in, had a z ≒ 0.12.

The samples shown in Tables 1 to 3 also
It has a main phase derived from the powder of the alloy for compacts and a subphase derived from the alloy for infiltration, and the ratio of the subphase in the sample was in the range of 20 to 40% by volume. .

<Comparison with Semi-Sintered Magnet> 29Nd-1B-remaining Fe (wt%) was used as the alloy for compacts, and 85Nd-remaining Fe (wt%) was used as the infiltration alloy for infiltration. A magnet sample No. 6-1 was prepared. However, the heat treatment at the time of infiltration is the same as that described in the above-mentioned JP-A-3
It was carried out at 700 ° C. for 10 hours according to the example of -80508.

Further, according to the method described in JP-A-3-80508, the molded body used in Sample No. 6-1 was
Sample No. 6 after heat treatment at 00 ℃ for 0.5 hours
Infiltration was carried out in the same manner as in No. 1 to obtain Sample No. 6-2.

The magnetic properties of these samples were measured. As a result, sample No. 6-1 had Br = 8.6 kG, HCJ = 6.1 kOe, and (BH) max = 13 MGOe, whereas sample No. 6-2 had Br = 8.2 kG. , HCJ = 5.1 kOe, (BH) max = 11 MGOe, and deterioration of the magnetic properties due to the heat treatment of the compact was observed.

From the results of the above examples, the effects of the present invention are clear.

[Brief description of drawings]

FIG. 1 is a drawing-substituting photograph showing a particle structure, which is a scanning electron micrograph (composition image) of a cross section of a magnet of the present invention.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 5, 1994

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (21)

[Claims] 1. R (R is at least one kind of rare earth element including Y), T (T is Fe, Co, N
i and Cu is at least one and Fe) and containing B, substantially the molded body alloy containing phase consisting R ₂ T ₁₄ B, wherein the R, R-rich than R ₂ T ₁₄ B A method for producing a magnet, characterized in that the molten alloy for infiltration is infiltrated into a compact of a powder of the alloy for compact to obtain a magnet. 2. The method for producing a magnet according to claim 1, wherein the melting point of the infiltration alloy is 1000 ° C. or lower. 3. The method for producing a magnet according to claim 1, wherein the melting point of the infiltration alloy is lower than the heat shrinkage initiation temperature of the compact. 4. The method for producing a magnet according to claim 1, wherein the infiltration alloy is melted by raising the temperature in a state where the compact and the infiltration alloy are in contact with each other. 5. The method for producing a magnet according to claim 1, wherein the molded body has a density of 4.0 g / cm ³ or more. 6. The method for producing a magnet according to claim 1, wherein a magnet having a relative density of 95% or more is produced. 7. The magnet for producing a magnet according to claim 1, wherein the alloy for a molded body contains 26 to 38% by weight of R, 0.9 to 3% by weight of B, and the balance is substantially T. Method. 8. The method for producing a magnet according to claim 1, wherein Nd + Pr accounts for 50% by weight or more of R of the alloy for molded body. 9. The method for producing a magnet according to claim 1, wherein Fe + Co accounts for 50% by weight or more of T. 10. The method for producing a magnet according to claim 1, wherein the powder of the alloy for molding has an average particle diameter of 0.1 to 50 μm. 11. The method for producing a magnet according to claim 1, wherein the infiltration alloy contains 40 to 99% by weight of R. 12. The balance of the infiltration alloy is substantially M (M
Is at least one of Fe, Co, Ni, Cu, Al, Sn, Ga and Ag). 13. B, Si and C in place of part of M
13. The method for producing a magnet according to claim 12, wherein the total content of these is at least 3% by weight of the alloy for infiltration. 14. The method for producing a magnet according to claim 1, wherein the molded body is molded in a magnetic field. 15. The method for producing a magnet according to claim 1, wherein the infiltrated compact is subjected to heat treatment at a temperature higher than the melting point of the infiltration alloy. 16. The holding temperature during the heat treatment is 800 ° C.
The method for manufacturing a magnet according to claim 15, which is the above. 17. A substantially R ₂ T ₁₄ B phase (R is at least one of rare earth elements including Y, T is Fe, or at least one of Co, Ni and Cu and Fe). And a subphase that is R richer than R ₂ T ₁₄ B and surrounds the main phase, and contains a R ₃ Co phase and / or an RCu phase in the subphase, A magnet characterized in that the proportion of the subphase in the magnet is 20 to 40% by volume. 18. The magnet according to claim 17, wherein at least a part of Co in the R ₃ Co phase and at least a part of Cu in the RCu phase are substituted with Fe. 19. The magnet according to claim 17, wherein at least part of Co in the R ₃ Co phase is replaced with Cu, and at least part of Cu in the RCu phase is replaced with Co. 20. The _subphase is R ₃ (Co _1-wx Fe _w Cu
_x ) phase (0.01≤w≤0.3, 0.01≤x≤0.
3) and R (Cu _1-yz Co _y Fe _z ) phase (0.01
≦ y ≦ 0.3, 0.01 ≦ z ≦ 0.3), and the content of each of these phases in the magnet is 1 to 30% by volume.
And the total content of these phases in the magnet is 20
18. The magnet of claim 17, which is -40% by volume. 21. The magnet according to claim 17, which contains 30 to 60% by weight of R and 0.3 to 6% by weight of B.