JP3367726B2 - Manufacturing method of permanent magnet - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a rare earth permanent magnet.

[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. But this one
It has a drawback that the raw material prices of Sm and Co are high. Among the rare earth elements, elements with small atomic weight, such as Ce and P
r and Nd are more abundant and cheaper than Sm. Also,
Fe is cheaper than Co. Therefore, in recent years, Nd-Fe
RTB type magnets such as -B magnets and Nd-Fe-Co-B magnets have been developed, and a sintered magnet is disclosed in JP-A-59-46008. In the magnet by the sintering method, the conventional Sm-Co-based powder metallurgy process (melting → master alloy ingot casting → ingot coarse crushing → fine crushing → molding → sintering →
(A magnet) can be applied and high magnetic properties can be easily obtained. The master alloy ingot produced by casting is
In general, a non-magnetic R-rich phase (hereinafter referred to as a grain boundary phase) covers a ferromagnetic R ₂ T ₁₄ B phase (hereinafter referred to as a main phase) constituting a crystal grain I have The mother alloy ingot is crushed to a particle size smaller than the crystal grain size thereof to obtain magnet powder. The grain boundary phase has a function of promoting sintering by becoming a liquid phase, and also plays an important role in generating coercive force of the sintered magnet.

R-T-B magnets have lower thermal stability than Sm-Co magnets. For example, ΔiHc / ΔT in the range of room temperature to 180 ° C. is −0.60 to −0.55%
When the temperature reaches about / ° C and is exposed to a high temperature, irreversible marked demagnetization occurs. Therefore, when the RTB magnet is applied to a device used in a high temperature environment, for example, various electric and electronic devices for automobiles, there is a problem that it is not practical.

In order to reduce the irreversible demagnetization due to the heating of the RTB-based magnet, in JP-A-62-165305, a part of Nd is replaced with Dy and a part of Fe is replaced with C.
It is proposed to replace it with o. However, ΔiHc / ΔT cannot be remarkably reduced only by adding Dy and Co, and the maximum energy product (BH) max decreases if the Dy substitution amount is large.

Further, in Japanese Patent Laid-Open No. 64-7503,
Proposals have been made to improve thermal stability by adding Ga. In IEEE Trans.Magn.MAG-26 (1990) 1960, Mo, V
Has been proposed to improve the thermal stability.
However, when Ga, Mo, V or the like is added, the thermal stability is improved but the maximum energy product is reduced.

On the other hand, the applicant of the present invention, in order to improve the thermal stability and suppress the decrease of the maximum energy product, Sn and Al
Has been proposed (Japanese Patent Laid-Open No. 32362/1993).
No. 02). However, the maximum energy product tends to decrease even if Sn is added, so it is desirable to minimize the amount of Sn added.

A method of adding Sn to a magnet by the so-called two-alloy method has also been reported. The two-alloy method is a method in which two kinds of alloy powders having different compositions, specifically, an alloy powder having a composition close to the main phase composition and an alloy powder having a composition close to the grain boundary phase composition are mixed and sintered. . Proc.11th Inter.Workshop on Ra
re-Earth Magnets and their Applications, Pittsburg
H., 1990, p.313, Nd _14.5 Dy _1.5 Fe ₇₅ AlB ₈ alloy powder, Fe ₂ Sn powder or CoSn powder 2.5.
Sintered magnets are manufactured by mixing less than or equal to wt%. The Nd ₆ Fe ₁₃ Sn phase is precipitated in the grain boundary phase of the magnet after the sintering, and it has been reported that the thermal dependence of the coercive force is improved in this sintered magnet.

However, according to the experiments by the present inventors, Fe
_{2 Since} Sn and CoSn have poor grindability, it is difficult to obtain a fine powder having a uniform particle size. Therefore, Fe ₂ Sn and CoSn
In the magnet obtained by mixing the above powder with the powder of the RTB-based alloy and sintering, the sizes of the Nd ₆ Fe ₁₃ Sn phase become uneven and the distribution becomes uneven. This is
It is also clear from Fig. 5. Therefore, good thermal stability cannot be stably obtained. In addition, Sn is replaced with Fe ₂ S
Nd ₆ Fe when added as n powder or CoSn powder
_Since R and Fe in the main phase are used to form 13Sn, the composition of the main phase is affected and the magnetic characteristics deteriorate.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to stably obtain a high thermal stability, and further, the magnetic properties, especially the R-T-B having a high maximum energy product. An object is to provide a system sintered permanent magnet.

[0010]

The above objects are achieved by the present invention described in (1) to (12) below. (1) A mixture of the powder of the main phase master alloy and the powder of the grain boundary phase master alloy is molded and then sintered to obtain R (R
Is at least one rare earth element including Y), T
(T is Fe or Fe and Co and / or Ni) and B as a main component, and substantially R ₂ T
A method for producing a permanent magnet having a main phase composed of ₁₄ B, wherein the main phase master alloy is substantially R ₂ T ₁₄ B
And a crystal grain boundary mainly composed of an R-rich phase having a higher R content than R ₂ T ₁₄ B, and the master alloy for the grain boundary phase is R, T '( T'is at least one of Fe, Co and Ni) and M (M is Sn
And at least one of In and Ga), 30 to 100% by weight of M is Sn, and these contents are R: 40 to 65% by weight, T ′: 30 to 60. % By weight, M: 1 to 12% by weight, and a method for producing a permanent magnet having an R ₆ T ′ ₁₃ M phase. (2) The method for producing a permanent magnet according to (1), wherein the ratio of the grain boundary phase master alloy in the mixture is 0.2 to 10% by weight. (3) The above-mentioned (1) or (2), wherein the main phase master alloy has a main phase of columnar crystal grains having an average diameter of 3 to 50 μm.
Manufacturing method of permanent magnet of. (4) The composition of the manufactured permanent magnet has R: 27 to 38% by weight, B: 0.5 to 4.5% by weight, M: 0.03 to 0.5% by weight, T: 51 to 72% by weight. %, The method for producing a permanent magnet according to any one of (1) to (3) above. (5) The method for producing a permanent magnet according to any one of the above (1) to (4), wherein a permanent magnet having an R ₆ T ′ ₁₃ M phase in a grain boundary is produced. (6) The molten alloy is cooled from one direction or two opposite directions to manufacture the main phase master alloy, and the main phase master alloy has a thickness in the cooling direction of 0.1 to 2 mm, and The master alloy for main phase is substantially free of α-Fe phase.
The method for producing a permanent magnet according to any one of (5). (7) The molten alloy is cooled from one direction or two opposite directions to produce the grain boundary phase master alloy, and the grain boundary phase master alloy has crystal grains with an average diameter of 20 μm or less, The method for producing a permanent magnet according to the above (6), wherein the grain boundary phase master alloy has a thickness in the cooling direction of 0.1 to 2 mm. (8) The method for producing a permanent magnet according to the above (6) or (7), wherein the molten alloy is cooled by a single roll method, a twin roll method or a rotating disk method. (9) The above (1) to (1) including a crushing step of crushing the main phase master alloy by a jet mill after absorbing hydrogen
The method for producing a permanent magnet according to any one of (8). (10) The method for producing a permanent magnet according to any one of the above (1) to (9), which comprises a crushing step of crushing the master alloy for grain boundary phase by a jet mill after absorbing hydrogen. (11) In the crushing step, the temperature of the mother alloy is set to 30
The method for producing a permanent magnet according to the above (9) or (10), in which the temperature is raised to a range of 0 to 600 ° C., hydrogen storage treatment is performed, and then pulverization is performed without hydrogen release treatment. (12) The method for producing a permanent magnet according to the above (9) or (10), wherein hydrogen is released in the mother alloy and then hydrogen is released.

[0011]

ACTIONS AND EFFECTS The present inventors have found that Sn-added R-
In the magnet produced by sintering a T-B type alloy powder, since the R ₆ T ₁₃ Sn is present in the grain boundaries, it was produced at the grain boundaries R ₆ T ₁₃ Sn improves the thermal stability I found it. It was also found that Sn remaining in the main phase reduces the maximum energy product.

Therefore, in the present invention, the two-alloy method is used when M (M is at least one of Sn, In and Ga) is added to the RTB magnet, and M is added to the master alloy for the main phase. An alloy containing M is used as the grain boundary phase master alloy without addition. Thus, since M is added only to the grain boundary phase master alloy, a sufficient amount of M can provide a sufficient thermal stability effect.

In the present invention, R ₆ is used as the grain boundary phase master alloy.
An alloy having a composition centered on T ′ ₁₃ M (T ′ is at least one of Fe, Co and Ni) is used. The alloy of this composition is easy to grind unlike Fe ₂ Sn and CoSn, and can be easily grinded into a fine powder by hydrogen storage. Therefore, in the magnet after sintering, the R ₆ T ′ ₁₃ M phase has uniform sizes in the crystal grain boundaries, and the uniformity of the distribution is good. Therefore, it is possible to stably mass-produce magnets having good thermal stability. On the other hand, Fe ₂ Sn and CoSn described above hardly occlude hydrogen, and therefore hydrogen occluding and pulverizing is impossible. In addition, R ₆ T _'13
When an alloy having a composition centering on M is used as the master alloy for the grain boundary phase, when the R ₆ T ′ ₁₃ M phase is present in the crystal grain boundaries, the main phase composition is hardly affected, and the master alloy for the main phase is almost eliminated. Magnetic properties according to the composition of the alloy can be obtained without deterioration.

[0014] In the present invention, when the crystal grain size of the grain boundary phase for mother alloy was within the above range, since the finer the powder is obtained, R ₆ T _'13 M phase dimension is more uniform in the magnet , Its dispersion is even better. Therefore, higher magnetic properties and its thermal stability can be obtained. The grain boundary phase master alloy having such a crystal grain size can be produced by cooling the molten alloy from one direction or two opposing directions by a single roll method, a twin roll method, or the like.

In the two-alloy method, an alloy having a composition close to that of R ₂ T ₁₄ B is generally used as a master alloy for the main phase. However, when this alloy is manufactured by a melt casting method, a soft magnetic α-Fe phase is precipitated. High magnetic properties cannot be obtained. For this reason, solution treatment is required. Solution treatment generally needs to be performed at about 900 ° C. or higher for 1 hour or longer. For example, JP-A-5-21219
In the publication, the R ₂ T ₁₄ B alloy produced by the high frequency melting method is subjected to solution treatment at 1070 ° C. for 20 hours. Since the solution treatment at high temperature and for a long time is required as described above, it is not possible to manufacture at a low cost when the melt casting method is used. In addition, as disclosed in Japanese Patent Laid-Open No. 5-105915, 2
When the R ₂ Fe ₁₄ B alloy used in the alloying method is manufactured by the direct reduction diffusion method, the content of Ca in the alloy becomes high, so that a high-performance magnet cannot be obtained.

On the other hand, in the preferred embodiment of the present invention,
A main phase master alloy having columnar crystal grains with an average diameter of 3 to 50 μm is used. This master alloy for the main phase has a good dispersion of the R-rich phase and does not substantially contain the α-Fe phase. For this reason,
In the magnet powder obtained by crushing the master alloy for main phase, the proportion of magnet particles having no R-rich phase is extremely low, and the content of the R-rich phase in each magnet particle is uniform. Therefore, the sinterability is good, and the R-rich phase is well dispersed even in the magnet after sintering, so that a high coercive force can be obtained. Further, since pulverization is extremely easy and a sharp particle size distribution is obtained, the uniformity of the crystal grain size after sintering becomes good,
High coercive force can be obtained. Further, since the crushing time is short, the amount of oxygen mixed is low, and a high residual magnetic flux density can be obtained.
In particular, when pulverization is performed by storing hydrogen, a very sharp particle size distribution is obtained. Further, it is not necessary to perform solution treatment for extinguishing the α-Fe phase.

Such a master alloy for the main phase is produced by cooling the molten alloy from one direction or two opposite directions, such as the single roll method and the twin roll method, as in the above grain boundary phase master alloy. can do.

In the above-mentioned Japanese Patent Laid-Open No. 4-338607, a crystalline or amorphous RE ₂ T ₁₄ B ₁ alloy powder having fine crystal grains of 10 μm or less and RE-T are used.
Although the alloy and the alloy are manufactured by the single roll method, there is no disclosure of the thickness of the alloy in the cooling direction. Further, there is no disclosure about the crystal grain size of the RE-T alloy. The composition of the RE-T alloy is different from that of the grain boundary phase master alloy used in the present invention.

[0019]

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

In the present invention, a mixture of the main phase master alloy powder and the grain boundary phase master alloy powder is molded and sintered to produce a rare earth sintered magnet.

<Main Phase Master Alloy> The main phase master alloy is R (R
Is at least one rare earth element including Y), T
(T is Fe or Fe and Co and / or Ni) and B as main components, and columnar crystal grains composed of substantially tetragonal R ₂ T ₁₄ B and R ₂ T ₁₄ B
And a crystal grain boundary mainly composed of an R-rich phase having a higher R content.

The rare earth elements in this case are Y, lanthanides and actinides, and R is Nd, Pr,
At least one of Tb, particularly Nd, is preferable, and it is preferable that Dy is further contained. Also, La, Ce, G
1 of d, Er, Ho, Eu, Pm, Tm, Yb, Y
It may include more than one species.

A mixture of misch metal or the like can be used as the raw material of the rare earth element.

The composition of the master alloy for the main phase is not particularly limited and may be appropriately determined in consideration of the composition of the master alloy for the grain boundary phase and the mixing ratio thereof, depending on the intended magnet composition. , R: 27 to 38% by weight, B: 0.9 to 2% by weight, T: the balance. In addition to R, T, B, Al,
Cr, Mn, Mg, Si, Cu, C, Nb, W, V, Z
Elements such as r, Ti and Mo may be added, but if the addition amount exceeds 6% by weight, the residual magnetic flux density will decrease.

In the main phase master alloy, in addition to these elements,
Carbon or oxygen, for example, may be contained as the unavoidable impurities or trace additives.

The average diameter of the columnar crystal grains of the master alloy for the main phase is preferably 3 to 50 μm, more preferably 5 to 50 μm,
More preferably 5 to 30 μm, most preferably 5 to 1
5 μm. If the average diameter is too small, the magnet particles obtained by pulverization become a polycrystalline body and a high degree of orientation cannot be obtained,
If the average diameter is too large, the above-mentioned effects cannot be realized.

The average diameter of columnar crystal grains is determined as follows. First, the master alloy for main phase is cut or polished so that the cross section of the columnar crystal grains that is substantially parallel to the major axis direction is exposed.
In this cross section, the width of at least 100 columnar crystal grains is measured to obtain an average value, which is taken as the average diameter of the columnar crystal grains. The width of the columnar crystal grains means the length in the direction perpendicular to the major axis direction.

The axial ratio (longitudinal length / diameter) of the columnar crystal grains is not particularly limited, but is usually about 2 to 50, and particularly 5 to 3.
It is preferably about 0.

In such a master alloy for main phase, the dispersion of the R-rich phase is good, and this state can be confirmed by, for example, an electron micrograph (backscattered electron image).

The width of the crystal grain boundary mainly composed of the R-rich phase is
Although it varies depending on the R content, it is usually about 0.5 to 5 μm.

The main phase master alloy having such a structural structure is preferably manufactured by cooling the molten alloy containing R, T and B as the main components from one direction or two opposite directions. When manufactured by these methods,
The major axis direction of the columnar crystal grains substantially coincides with the cooling direction.

In the present specification, the cooling direction means a direction perpendicular to the surface of the cooling substrate such as the peripheral surface of the cooling roll, that is, the heat transfer direction.

As a method of cooling from one direction, a single roll method and a rotating disk method are preferable.

The single roll method is a method in which the molten alloy injected from a nozzle is brought into contact with the peripheral surface of a cooling roll to cool it. The structure of the device is simple and the durability is high, and the cooling rate is easy to control. is there. The master alloy for main phase produced by the single roll method is usually in the form of a ribbon. There is no particular limitation on various conditions in the single roll method, it may be appropriately set so as to obtain a main phase master alloy having the above-described structural structure,
Usually, the conditions are as shown below. Cooling roll is C
It may be made of various materials such as u and Cu alloys such as Cu-Be which are used in a normal melt cooling method. A cooling roll having a surface layer made of a metal different from that of the base material may be used on the peripheral surface of the roll-shaped base material made of the above material. The surface layer is usually provided for adjusting thermal conductivity and improving wear resistance. For example, when the base material is made of Cu or a Cu alloy and the surface layer is made of Cr, the difference in cooling rate in the cooling direction of the main phase master alloy is small, and a homogeneous main phase master alloy is obtained. Further, since Cr has good wear resistance, a master alloy for main phase having uniform characteristics can be obtained when continuously manufacturing a large amount of master alloy for main phase.

The rotary disk method is a method in which the molten alloy injected from a nozzle is brought into contact with the main surface of a rotating disk-shaped cooling substrate to cool it. The main phase master alloy produced by the rotating disk method is usually in the form of scales. In the rotating disk method, the cooling rate of the peripheral portion of the scale-like main phase master alloy is likely to be high, so that it is difficult to obtain a uniform cooling rate as compared with the single roll method.

A twin roll method is preferable as a method for cooling the molten alloy from two opposite directions. In the twin roll method,
Two cooling rolls similar to the single roll method described above are used, the peripheral surfaces of both rolls are arranged so as to face each other, and the molten alloy is injected between these peripheral surfaces. The main phase master alloy produced by the twin roll method is usually in the form of a ribbon or flakes. Various conditions in the twin roll method are not particularly limited, and may be appropriately set so as to obtain the above-described tissue structure.

Of these various cooling methods, the single roll method is most preferable.

The molten alloy is preferably cooled in a non-oxidizing atmosphere such as nitrogen or Ar or in vacuum.

When the molten alloy is cooled in one direction or in two opposite directions to produce the master alloy for the main phase, the thickness of the master alloy for the main phase in the cooling direction is preferably 0.1 to 2 mm, more preferably Is 0.2 to 1.0 mm, more preferably 0.2 to
0.5mm. If the thickness in the cooling direction is too small, it becomes difficult to set the average diameter of the columnar crystal grains to 3 μm or more.
On the other hand, if the thickness in the cooling direction is too large, especially when the method of cooling from one direction is used, the unevenness of the tissue structure in the cooling direction becomes large. Specifically, since the crystal grain size becomes too small on the cooling surface side, it tends to become polycrystalline grains when pulverized, which leads to a decrease in sintered density and deterioration of orientation, and good magnetic properties are obtained. I will not be able to. If the thickness in the cooling direction is too large, the average diameter of the columnar crystal grains will be 50 μm.
It becomes difficult to do the following.

When such a cooling method is used, a composition having a relatively small R content, for example, an R content of 26 to 3 is used.
Even if the amount is about 2% by weight, it is possible to manufacture a main phase master alloy that does not substantially contain the α-Fe phase. Specifically, the content of the α-Fe phase is 5% by volume or less, particularly 2% by volume.
It can be: Therefore, the solution treatment for reducing the ratio of different phases is unnecessary.

<Master Alloy for Grain Boundary Phase> The master alloy for grain boundary phase is
It contains R, T ′ (T ′ is at least one of Fe, Co and Ni) and M (M is at least one of Sn, In and Ga). These contents are R: 40 to 65% by weight, T ': 30 to 60% by weight,
M: 1 to 12% by weight, preferably R: 50 to 6
0% by weight, T ': 40 to 50% by weight, M: 4 to 10% by weight.

If the amount of R is too large, it is likely to be oxidized.
Unsuitable as a starting material. If T'is too much, α-F
The magnetic phase deteriorates due to the precipitation of soft magnetic heterogeneous phase such as e. And if R or T'is too small or too large,
When the R ₆ T ′ ₁₃ M phase, which will be described later, is generated during sintering, the main phase composition is affected and the magnetic properties deteriorate. In addition,
The composition of R in the grain boundary phase master alloy (the ratio of each rare earth element in R) is not particularly limited, but since the final composition is easily adjusted, it is almost the same as the composition of R of the main phase master alloy. Preferably.

Co and Ni improve the corrosion resistance of the magnet, but when they are present in the main phase of the magnet, they lower the coercive force. Therefore, Co and Ni are mainly present in the grain boundary phase in the sintered magnet. preferable. Therefore, it is preferable that the master alloy for the grain boundary phase contains Co and / or Ni.

As M, Sn is particularly preferable, and 30 to 100% by weight of M is preferably Sn.

For the grain boundary phase master alloy, Al, Si, Cu,
One or more elements such as Nb, W, V and Mo may be added, but the total addition amount is preferably 5% by weight or less in order to suppress a decrease in the residual magnetic flux density.

In addition to these elements, the mother alloy for the grain boundary phase may contain carbon or oxygen as unavoidable impurities or trace additives.

The master alloy for grain boundary phase, 'comprises ₁₃ M phase, _{further, RT' R 6 T 2,} RT '3, RT' 7, R 5 T '
It consists of a mixed phase which may contain at least one of the ₁₃ and other RT ′ and RT′-M phases, which is independent of the manufacturing method. The R ₆ T ′ ₁₃ M phase is body-centered cubic. The existence of each phase is described in, for example, J. Magnetism and Magnetic Materials 101
(1991) 417-418, it can be confirmed by electron diffraction or the like.

In the crystalline grain boundary phase master alloy produced by the quenching method such as the arc melting method, the high frequency melting method, or the single roll method, when the above-mentioned phases are usually present and the cooling rate is high. It becomes amorphous. In the present invention, such an alloy is usually crushed and used as it is. However, such a grain boundary phase master alloy is annealed to obtain R ₆ T ′ ₁₃
The ratio of the M phase may be increased, or the R ₆ T ′ ₁₃ M phase may be generated. The annealing in this case is 600
It may be carried out at about 900 ° C. for about 1 to 20 hours. If the temperature during annealing is too high, Nd will dissolve, and if it is too low, almost no change in the phase structure will be observed.

The upper limit of the average crystal grain size of the grain boundary phase master alloy is
It is preferably 20 μm, more preferably 10 μm.
If the average crystal grain size is too large, the distribution of each phase described above becomes non-uniform. Therefore, the composition of each particle is greatly different when crushed. When the powder of the grain boundary phase master alloy consisting of such particles is mixed with the powder of the main phase master alloy,
R ₆ which is important for improving the characteristics because the composition distribution is not uniform
_{'Our 13} M phase precipitation becomes difficult, R ₆ T' T occurs region primary phase composition is affected for ₁₃ M-phase deposition, thermal stability and magnetic properties (coercivity, squareness) Insufficient Becomes There is no particular lower limit to the average crystal grain size, and a grain boundary phase master alloy in an amorphous state may be used. However, if the average crystal grain size is small, pulverization becomes easy, and therefore, depending on the pulverization conditions, a large amount of ultrafine powder may be generated during pulverization. Since it is difficult to collect ultrafine powder, if ultrafine powder is generated, the recovery rate of the grain boundary phase master alloy is selectively reduced when the mixture of coarse powders of both mother alloys is pulverized, and the recovery rate also fluctuates. Sometimes. For this reason, compositional deviation (reduction of the content ratio of R and M) and its variation may occur, resulting in reduction of thermal stability, coercive force, sintering density and the like and variation thereof. Therefore, depending on the pulverization conditions, the average crystal grain size is 0.1 μm or more, and particularly, 0.1.
It may be 5 μm or more.

The method for producing the grain boundary phase master alloy is not particularly limited, and may be produced by an ordinary casting method or the like, but it is preferable to use one of the molten alloys as in the case of the main phase mother alloy described above. It is manufactured by a method of cooling from one direction or two opposite directions. Various conditions in these cooling methods are preferably the same as those in the case of the main phase master alloy described above.
The thickness of the grain boundary phase master alloy in the cooling direction is preferably in the same range as the main phase master alloy described above.

<Pulverizing Step and Mixing Step> The method for producing the mixture of the main phase master alloy powder and the grain boundary phase master alloy powder is not particularly limited. For example, a mixture may be produced by coarsely pulverizing both mother alloys at the same time and further finely pulverizing them. After coarsely pulverizing each mother alloy, coarse powders of both mother alloys are mixed and then finely pulverized. A mixture may be produced, and each master alloy may be roughly pulverized and then finely pulverized to mix fine powders of both mother alloys. However, the method in which both mother alloys are separately finely pulverized and then mixed is complicated in process and difficult to reduce the cost.

When a master alloy for grain boundary phases having a small average crystal grain size produced by a single roll method or the like is used, it is preferable to mix both master alloys, simultaneously pulverize them, and further pulverize them. In this way, a homogeneous mixture is easily obtained. On the other hand, in the case of using the grain boundary phase master alloy produced by the melting method, after coarsely pulverizing each mother alloy, the coarse powders of each mother alloy are mixed, and then finely pulverized, or each It is preferable to use a method in which the mother alloys are roughly pulverized and then finely pulverized, and the fine powders of the respective mother alloys are mixed. Since the grain boundary phase master alloy produced by the melting method has a large crystal grain size, it is difficult to perform coarse pulverization at the same time as the main phase master alloy.

The ratio of the grain boundary phase master alloy in the mixture is preferably 0.2 to 10% by weight, more preferably 0.5 to 10% by weight. If this ratio is too low, the effect of adding the grain boundary phase master alloy becomes insufficient,
If this ratio is too high, the magnetic properties, especially the residual magnetic flux density will be insufficient.

The method of crushing each mother alloy is not particularly limited, and a mechanical crushing method, a hydrogen absorbing crushing method or the like may be appropriately selected, and crushing may be performed by combining these methods. However, it is preferable to carry out hydrogen storage pulverization because a magnet powder having a sharp particle size distribution can be obtained.

Hydrogen may be absorbed directly in the ribbon-shaped mother alloy, or may be absorbed after the mother alloy is roughly ground by a mechanical grinding means such as a stamp mill. Coarse pulverization is usually carried out until the average particle size becomes about 15 to 500 μm.

Various conditions for hydrogen storage and pulverization are not particularly limited, and a usual hydrogen storage and pulverization method, for example, hydrogen storage treatment and hydrogen release treatment are performed at least once each, and further,
After releasing hydrogen, a method of performing mechanical pulverization can be used if necessary.

However, the temperature of the mother alloy is 300 to 600 ° C.
The temperature may be raised to the range of, preferably 350 to 450 ° C., hydrogen storage treatment may be performed, and mechanical pulverization may be performed without hydrogen release treatment. According to this method, it is not necessary to perform the hydrogen releasing treatment, so that the manufacturing time can be shortened. Further, if such a hydrogen storage treatment is applied to the main phase master alloy, a powder having a sharp particle size distribution can be obtained.

When the main phase master alloy is subjected to hydrogen storage treatment, hydrogen is selectively stored in the R-rich phase constituting the crystal grain boundaries and the volume of the R-rich phase increases, so that pressure is applied to the main phase. , The region in contact with the R-rich phase becomes a starting point and cracks occur in the main phase. The cracks tend to occur in layers in a plane substantially perpendicular to the long axis direction of the columnar crystal grains. on the other hand,
Since hydrogen is hardly occluded in the main phase, irregular cracks are less likely to occur inside the main phase. Therefore, generation of fine powder and coarse powder is prevented during the subsequent mechanical pulverization, and magnet particles having uniform diameters are obtained.

The hydrogen stored in the above temperature range is
R dihydride is formed in the R-rich phase of the main phase master alloy, but since the R dihydride is extremely easy to break, generation of coarse powder is prevented.

If the temperature of the main phase master alloy during hydrogen storage is less than the above range, a large amount of hydrogen will be stored in the main phase, and R in the R-rich phase will become a trihydride and become H. _Since it reacts with ₂ O, the amount of oxygen in the magnet tends to increase.
If the temperature of the main phase master alloy exceeds the above range, R dihydride will not be produced.

In the conventional hydrogen storage pulverization, a large amount of fine powder was generated, and since the fine powder was removed and then sintered, there was a problem in the deviation of the R content between the composition before pulverization and the composition after pulverization. However, since the generation of fine powder is prevented by this method, the composition deviation of R is almost eliminated. Further, hydrogen is selectively occluded in the crystal grain boundaries of the master alloy for the main phase and hardly occluded in the main phase, so that the amount of hydrogen used is remarkably reduced to about 1/6.

Hydrogen is released during sintering.

Even during hydrogen storage treatment of the grain boundary phase master alloy, the volume increases due to hydrogen storage and cracks occur,
Be crushed.

The hydrogen storage step is preferably carried out in a hydrogen atmosphere, but may be a mixed atmosphere containing an inert gas such as He and Ar and other non-oxidizing gas. The hydrogen partial pressure is usually about 0.05 to 20 atm, but generally 1
It is preferable that the pressure is not more than atmospheric pressure. Also, the occlusion time is 0.
It is preferably about 5 to 5 hours.

For mechanical pulverization after hydrogen storage, it is preferable to use an air flow type pulverizer such as a jet mill. By using the air flow type pulverizer, magnet powder having a uniform particle size can be obtained.

The jet mill is generally classified into a jet mill using a fluidized bed, a jet mill using a vortex, a jet mill using a collision plate, and the like. FIG. 1 is a schematic configuration diagram of a jet mill that uses a fluidized bed, FIG. 2 is a schematic configuration end view of a main portion of a jet mill that uses a vortex flow, and FIG. 2 is a schematic configuration cross-sectional view of a main portion of a jet mill that uses a collision plate. As shown in FIG.

In the jet mill having the structure shown in FIG. 1, a plurality of gas introducing pipes 22 are provided on the peripheral side surface of the cylindrical container 21 and the gas introducing pipes 2 are provided on the bottom surface of the container.
From 3, the air flow is introduced into the container 21. On the other hand, the raw material (the mother alloy after hydrogen storage) is charged into the container 21 through the raw material charging pipe 24. The input raw materials are
The fluidized bed 25 is formed by the air flow introduced into the container 21, and collisions are repeated in the fluidized bed 25.
It also collides with the wall surface of No. 1 and is pulverized. The fine powder obtained by the pulverization is classified by the classifier 26 provided on the upper part of the container 21, and is discharged to the outside of the container 21. On the other hand, the powder that has not been sufficiently pulverized returns to the fluidized bed 25 again and continues to be pulverized.

FIG. 2A is a plan end view and FIG. 2B is a side end view. In the jet mill having the configuration shown in FIG. 2, a raw material introducing pipe 32 and a plurality of gas introducing pipes 33 are arranged on the wall surface of the container 31. From the raw material introduction pipe 32, the raw material is introduced into the container 31 together with the carrier gas,
Gas is injected into the container 31 from the gas introduction pipe 33.
The raw material introducing pipe 32 and the gas introducing pipe 33 are respectively the containers 3
It is arranged so as to be inclined with respect to the inner wall surface of No. 1 and the injected gas forms a vortex in a horizontal plane in the container 31 and forms a fluidized bed by a vertical motion component. . The raw material repeatedly collides in the swirl flow and the fluidized bed in the container 31, and collides with the wall surface of the container 31 to be finely pulverized. The fine powder obtained by the pulverization is discharged from the upper part of the container 31. Further, the powder which has not been sufficiently pulverized is classified in the container 31, sucked through the hole on the side surface of the gas introduction pipe 33, further injected into the container 31 together with the gas, and the pulverization is repeated.

In the jet mill having the structure shown in FIG. 3, the raw material charged from the raw material charging port 41 is supplied to the nozzle 4
It is accelerated by the air flow introduced from 2 and collides with the collision plate 43 to be crushed. The crushed raw material is classified, the fine powder is discharged to the outside of the jet mill, and the fine powder that has been insufficiently pulverized is returned to the raw material input port 41 again, and the pulverization is repeated in the same manner as above.

The air flow in the air flow type crusher is preferably composed of a non-oxidizing gas such as N ₂ gas or Ar gas.

The average diameter of the powder obtained by pulverization is from 1 to
It is preferably about 10 μm.

The conditions for the pulverization differ depending on the dimensions and composition of the mother alloy, the configuration of the air flow type pulverizer used, etc., and therefore may be appropriately set.

Incidentally, due to hydrogen absorption, not only cracks may occur but also at least part of the mother alloy may collapse. When the size of the mother alloy after hydrogen storage is too large, preliminary pulverization may be performed by other mechanical means before pulverization by the gas stream pulverizer.

<Molding Step> The mixture of the main phase master alloy powder and the grain boundary phase master alloy powder is usually molded in a magnetic field. In this case, the magnetic field strength is preferably 15 kOe or more, and the molding pressure is preferably about 0.5 to ³ t / cm ² .

<Sintering Step> The sintering conditions of the molded body are usually
It is preferable that the temperature is set to 1000 to 1200 ° C. for 0.5 to 5 hours, and after the sintering, it is rapidly cooled. The sintering atmosphere is A
The atmosphere is preferably an inert gas such as r gas, or vacuum. Then, after sintering, it is preferable to perform an aging treatment in a non-oxidizing atmosphere or in a vacuum. As this aging treatment, a two-step aging treatment is preferable. In the first-step aging treatment step, the temperature is maintained in the range of 700 to 900 ° C. for 1 to 3 hours. Next, a first quenching step of quenching to within the range of room temperature to 200 ° C. is provided. In the second aging process,
Hold in the range of 500 to 700 ° C. for 1 to 3 hours. Then, a second quenching step of quenching to room temperature is provided. The cooling rate in each of the first and second quenching steps is preferably 10 ° C./min or more, and particularly preferably 10 to 30 ° C./min. Further, the rate of raising the temperature to the holding temperature in each aging treatment step is not particularly limited, but is usually 2 to 10 ° C.
It should be about / min.

After the aging treatment, it is magnetized if necessary.

<Magnet Composition> The magnet composition is determined by the composition of the main phase master alloy, the composition of the grain boundary phase master alloy, and the mixing ratio of both master alloys. In the present invention, the composition of the magnet after sintering is R:
27-38% by weight, B: 0.5-4.5% by weight, M:
It is preferably 0.03 to 0.5% by weight, particularly preferably 0.05 to 0.3% by weight, and T: 51 to 72% by weight.

The residual magnetic flux density improves as the R content decreases, but when the R content decreases, an iron-rich phase such as the α-Fe phase precipitates, which adversely affects the pulverization and deteriorates the magnetic properties. Moreover, since the ratio of the R-rich phase decreases,
Since it becomes difficult to sinter and the sintered density becomes low,
The improvement of the residual magnetic flux density will reach the ceiling. However, in the present invention, even when the R content is as small as 27% by weight, the sintered density can be increased and the precipitation of the α-Fe phase is substantially not present. However, if R is less than 27% by weight, magnetization becomes difficult. If the R content is too large, a high residual magnetic flux density cannot be obtained. If the B content is too small, a high coercive force cannot be obtained, and if the B content is too large, a high residual magnetic flux density cannot be obtained.

[0079]

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

<Sample No. 1-1 to 1-8 (Example)
> Nd, Fe, Co, Sn, each having a purity of 99.9%,
A Ga-In master alloy was prepared by arc melting in an Ar atmosphere using Ga and In. In addition, the purity is 99.
Using 9% of Nd, Dy, Fe, Co, Al and ferroboron, a master alloy for main phase was manufactured by high frequency melting in an Ar atmosphere. The composition of each master alloy is shown in Table 1.

Next, each mother alloy was separately crushed. Coarse crushing was performed with a jaw crusher and a brown mill in a nitrogen atmosphere. Next, the coarse powder of the grain boundary phase master alloy and the coarse powder of the main phase master alloy were mixed in a nitrogen atmosphere.
Table 1 shows the mixing ratio (weight ratio) and the composition (magnet composition) of the obtained mixture. Then, the mixture was finely pulverized by a jet mill using high-pressure nitrogen gas to a particle size of 3 to 5 μm. The obtained fine powder was applied in a magnetic field of 12 kOe for 1.5
Molding was performed at a pressure of t / cm ² to obtain a molded body. The compact was sintered in vacuum at 1080 ° C. for 4 hours and then rapidly cooled. The obtained sintered body was subjected to a two-step aging treatment in an Ar atmosphere. The first aging treatment was performed at 850 ° C. for 1 hour and the cooling rate was 15 ° C./min. The second stage aging treatment was performed at 620 ° C. for 1 hour and the cooling rate was 15 ° C./min. After the aging treatment, it was magnetized to obtain a magnet sample.

For each sample, coercive force Hcj, maximum energy product (BH) max, dHcj / 25-180 ° C.
dT was measured by BH tracer and VSM.
Each sample was processed to have a permeance coefficient of 2, magnetized with a magnetic field of 50 kOe, stored in a thermostat for 2 hours, and further cooled to room temperature. Then, measure the irreversible demagnetization rate with a flux meter and confirm that the irreversible demagnetization rate is 5
The temperature T (5%) which reaches 100% was determined. The results are shown in Table 1.

<Sample No. 2-1 to 2-4 (comparative example)
A master alloy for magnet having the composition shown in Table 2 was manufactured in the same manner as the master alloy for main phase used in the above-mentioned example samples.

Then, in the same manner as the above-mentioned example samples, coarse pulverization, fine pulverization, molding, sintering, aging, and magnetizing were performed to obtain magnet samples. The same measurement as above was performed on these samples. The results are shown in Table 2.

[0085]

[Table 1]

[0086]

[Table 2]

Comparison between sample Nos. 1-1 and 2-3, comparison between sample Nos. 1-2 and 2-2, sample No. 1-
As is clear from the comparison between 3 and 1-4 and 2-4,
Even if the Sn content of the example sample is half that of the comparative example sample, thermal stability equal to or higher than that is obtained, and since the Sn content is small, higher magnetic characteristics are obtained. Further, from the comparison between Sample Nos. 1-1 and 2-2, it is understood that the present invention improves the magnetic properties as well as the thermal stability when the Sn content is the same. Also, sample No. 1
Comparison with -2 and 1-5, the composition ratio of the grain boundary phase for master alloy the closer the R ₆ T _'13 M, it can be seen that the improved thermal stability and magnetic properties. The composition of the grain boundary phase master alloy used in Sample No. 1-2 was 50.5Nd-42.5Fe-
7.0Sn (wt%) is Nd ₆ F when converted to atomic ratio
e ₁₃ Sn. Also, sample No. 1-6 and sample
From the comparison with No. 2-3, it is understood that the present invention can suppress the deterioration of magnetic properties even when the Sn content is the same. Then, from sample Nos. 1-7 and 1-8, Ga, In
It can be seen that addition of is also effective.

[0088] Incidentally, the grain boundary phase for mother alloy used in Example samples shown in Table _{1, R 6 T '13 M,} RT' 2, RT '
₃ , RT ' ₇ and R ₅ T' ₁₃ phases were included, and the average crystal grain size was 20 μm. Identification of the phase constitution and measurement of the crystal grain size were carried out by SEM-EDX after polishing the alloy.

<Sample No. 3-1 (Example)> A master alloy for main phase was manufactured by a single roll method. A Cu roll was used as the cooling roll, and its peripheral speed was 2 m / s. The obtained alloy was a ribbon having a thickness of 0.3 mm and a width of 15 mm.
Table 3 shows the composition of the master alloy for the main phase. Main phase master alloy,
It was cut so that the surface including the cooling direction appeared, the cross section was polished, and a photograph of the backscattered electron image was taken with an electron microscope.
In the obtained photograph, columnar crystal grains whose major axis direction was the cooling direction (thickness direction of the ribbon) were observed. This columnar crystal grain 1
When the average diameter of 00 pieces was calculated, it was 10 μm. The existence of α-Fe phase was not recognized in the mother alloy.
This master alloy for main phase was roughly pulverized in the same manner as in the above-described example sample.

The master alloy for the grain boundary phase was manufactured in the same manner as in the sample of the above-mentioned example, and similarly crushed. The composition of the grain boundary phase master alloy is shown in Table 3.

The coarse powder of the main phase master alloy and the coarse powder of the grain boundary phase master alloy were mixed in a nitrogen atmosphere. Mixing ratio (weight ratio)
Is shown in Table 3.

Next, the mixture was subjected to a hydrogen storage treatment under the following conditions and mechanically pulverized without performing a hydrogen desorption treatment.

Hydrogen storage treatment mixture temperature 400 ° C. treatment time 1 hour treatment atmosphere 0.5 atmosphere of hydrogen atmosphere

A jet mill having the structure shown in FIG. 2 was used for mechanical grinding. The pulverization was performed until the average particle diameter of each magnet powder became 3.5 μm.

In the steps after fine pulverization, magnet samples were obtained in the same manner as the above-mentioned example samples, and the same measurements as above were performed. The results are shown in Table 3.

<Sample No. 3-2 (Example)> Sample No. 3-2 was manufactured by the single roll method under the same conditions as those of the main phase master alloy of Sample No. 3-1. N
A magnet sample was obtained in the same manner as in o.3-1. The master alloy for the grain boundary phase was a ribbon having a thickness of 0.3 mm and a width of 15 mm.
The same measurement as above was performed for this sample.
The results are shown in Table 3.

<Sample No. 3-3 (Example)> Sample No. 3-3 except that the peripheral speed of the cooling roll was 30 m / s when the master alloy for the grain boundary phase was manufactured by the single roll method. Two
A magnet sample was obtained in the same manner as in. The same measurement as above was performed for this sample. The results are shown in Table 3.

<Sample No. 3-4 to 3-5 (comparative example)
A master alloy for a magnet having a composition shown in Table 3 was manufactured by a melting method or a single roll method. The single roll method was carried out under the same conditions as in the above-mentioned Example Sample No. 3-1. Then, roughly crushed, finely crushed, molded, sintered, similarly to the above-mentioned example samples,
Each treatment of aging and magnetization was performed to obtain a magnet sample.
The same measurement as above was performed on these samples. The results are shown in Table 3.

[0099]

[Table 3]

[0100] Incidentally, the sample No. 3-1 and the grain boundary phase for mother alloy used each _{3-2, R 6 T '13 M,} R
_{T '2, RT' 3,} RT comprises the phases of _{'7, R 5 T' 13} , the average crystal grain size sample No. 3-1 is 25 [mu] m, the sample No. 3-2 was 10 [mu] m. Also a sample
The grain boundary phase master alloy used in No. 3-3 was amorphous.

From the results shown in Table 3, the average diameter is 3 to 50.
When using the master alloy for the main phase with columnar crystal grains of μm,
It can be seen that extremely high (BH) max is obtained. And
An average diameter of 20 as in Sample Nos. 3-2 and 3-3
It can be seen that the thermal stability and magnetic properties are further improved when the master alloy for grain boundary phase having crystal grains of μm or less is used.

In each of the above examples, the same effect was obtained even when a part of Fe in the grain boundary phase master alloy was replaced with Ni. Further, when the grain boundary phase master alloy was annealed at 700 ° C. for 20 hours, the proportion of the R ₆ T ′ ₁₃ M phase increased, but the magnetic properties and thermal stability of the magnet sample using this were It was equivalent to each sample above.

[Brief description of drawings]

FIG. 1 is a side view showing a jet mill using a fluidized bed by cutting out a part thereof.

FIG. 2 is an end view showing a main part of a jet mill that uses a vortex flow, (a) is a plan end view, and (b) is a side end view.

FIG. 3 is a sectional view showing a main part of a jet mill using a collision plate.

[Explanation of symbols]

21 containers 22,23 Gas introduction pipe 24 Raw material input pipe 25 fluidized bed 26 classifier 31 containers 32 Raw material introduction pipe 33 gas introduction pipe 41 Raw material input port 42 nozzles 43 collision plate

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 4-119604 (JP, A) JP 64-706 (JP, A) JP 5-222488 (JP, A) JP 5- 117701 (JP, A) JP 5-182814 (JP, A) JP 5-74618 (JP, A) JP 4-268050 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01F 1/00-1/117 B22F C22C

Claims (12)

(57) [Claims] 1. A mixture of a main phase master alloy powder and a grain boundary phase master alloy powder is molded and then sintered to obtain R.
(R is at least one kind of rare earth element including Y), T (T is Fe, or Fe and Co and / or Ni) and B as main components, and substantially R ₂ T ₁₄ a method of manufacturing a permanent magnet having formed main phase from B, the main-phase master alloy is substantially a main phase consisting of R ₂ T ₁₄ B, than R ₂ T ₁₄ B The grain boundary phase master alloy has R and T ′ (T ′ is Fe and Co).
And Ni is at least one kind) and M (M is
Sn and at least one of In and Ga), 30 to 100% by weight of M is Sn, and the content of these is R: 40 to 65% by weight, T ': 30 to. 60 wt%, M: 1 to 12 percent by weight, method of manufacturing a permanent magnet having a R ₆ T _'13 M phase. 2. The method for producing a permanent magnet according to claim 1, wherein a ratio of the grain boundary phase master alloy in the mixture is 0.2 to 10% by weight. 3. The main phase master alloy has an average diameter of 3 to 50.
The main phase of columnar crystal grains having a size of μm.
Manufacturing method of permanent magnet of. 4. The composition of the manufactured permanent magnet is R: 27 to 38% by weight, B: 0.5 to 4.5% by weight, M: 0.03 to 0.5% by weight, T: 51 to 72% by weight The method for producing a permanent magnet according to claim 1, wherein 5. The method for producing a permanent magnet according to claim 1, wherein a permanent magnet having an R ₆ T ′ ₁₃ M phase in a grain boundary is produced. 6. The molten alloy is cooled from one direction or two opposite directions to manufacture the main phase master alloy, and the main phase master alloy has a thickness in the cooling direction of 0.1 to 2 mm. The method for producing a permanent magnet according to claim 1, wherein the main phase master alloy does not substantially include an α-Fe phase. 7. The molten alloy is cooled in one direction or in two opposite directions to produce the grain boundary phase master alloy, and the grain boundary phase master alloy has crystal grains with an average diameter of 20 μm or less. The method for producing a permanent magnet according to claim 6, wherein the mother alloy for the grain boundary phase has a thickness in the cooling direction of 0.1 to 2 mm. 8. The method for producing a permanent magnet according to claim 6, wherein the molten alloy is cooled by a single roll method, a twin roll method, or a rotating disk method. 9. The method for producing a permanent magnet according to claim 1, further comprising a pulverizing step of pulverizing the master alloy for main phase with a jet mill after occluding hydrogen. 10. The method for producing a permanent magnet according to claim 1, further comprising a pulverization step of pulverizing the grain boundary phase master alloy with a jet mill after occluding hydrogen. 11. The crushing step according to claim 9, wherein after the temperature of the mother alloy is raised to a range of 300 to 600 ° C., hydrogen storage treatment is performed, and then pulverization is performed without hydrogen release treatment. Manufacturing method of permanent magnet of. 12. The method for producing a permanent magnet according to claim 9, wherein hydrogen is released after the mother alloy stores the hydrogen.