JPH07331394A - Production of rare earth alloy ingot and alloy powder for permanent magnet, and bond magnet - Google Patents

Abstract

PURPOSE:To produce a rare earth alloy ingot for producing a bond magnet excellent in magnetic properties by specifying the cross-sectional dimensional ratio of a rare earth allay ingot for an R-T-(M)-B permanent magnet and obtaining an ingot in which the concn. of tetragonal Nd2 Fe14B type compounds is regulated to a high one and the concns. of R and B areas are regulated to low ones. CONSTITUTION:As for an ingot constituted of 11.5 to 12.5 at% R (R denotes at least one kind among rare earth elements including Y, and one or more kinds of Pr and Nd are contained by>=50 at% in R), 79 to 83at% T (Fe or a part of Fe is substituted by <=50at.% Co therein), 0.01 to 2at% M (M denotes one or more kinds among Ga, Zr, Nb, Hf and Ta) and 5.5 to 6.5at% B, its cross-sectional dimension is specified so as to regulate the width L to >=30mm, the thickness (d) to 10 to 35mm and the ratio of L/d to >=3.0, and tetragonal Nd2Fe14B type compounds are allowed to present by >=85% in the allay and the areas of 11.0% R and <5.0% B are not allowed to present by >=20% by volume ratio. Thus, the ingot for producing a bond magnet excellent in magnetic properties can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to R (rare earth element) having high magnetization, excellent magnetic anisotropy and high coercive force, which can be used in various motors and actuators.
A tetragonal Nd ₂ Fe ₁₄ -T (iron group element)-(M) -B-based rare earth alloy ingot for permanent magnets and an alloy powder, and a method for manufacturing a bonded magnet, in which a cross-sectional dimension ratio of the ingot is specified. B
An ingot having a R- and B-region with a low concentration of 85% or more of the type compound is obtained, annealed in a specific atmosphere, and hydrogenated in H ₂ gas under specific temperature-raising conditions and atmospheric conditions, Furthermore, by cooling after H ₂ treatment under specific conditions, a rare earth alloy powder having a fine crystal grain size and magnetic anisotropy is obtained,
The present invention relates to a rare earth alloy ingot for permanent magnets and alloy powder for producing a bonded magnet having excellent magnetic properties, and a method for producing a bonded magnet.

[0002]

2. Description of the Related Art As a casting method for an RT- (M) -B type permanent magnet alloy, for example, in Japanese Patent Laid-Open No. 2-251359, a mold release agent is applied to the inner surface when a molten metal is cast into a mold. A method has been proposed in which a molten metal of 1200 to 1700 ° C. is cast into the cast mold and the cooling rate is changed around the peritectic temperature during cooling so that the casting composition becomes almost columnar crystals. It is said that the ingot melted by the above-mentioned casting method has a cast structure oriented in almost one direction, so that a cast magnet having excellent magnetic anisotropy can be obtained.

Further, as a method for producing a rare earth alloy powder for permanent magnets by a hydrotreating method, an RT- (M) -B-based raw material alloy ingot or powder is mixed with H ₂ gas atmosphere or H ₂ gas and an inert gas. In a mixed atmosphere of 500 ℃ ~
After holding at 1000 ° C. to occlude H ₂ in the alloy ingot or powder, the H ₂ gas pressure was 13 Pa (1 × 10
^-1 Torr) or less vacuum atmosphere or H ₂ gas partial pressure 13
A hydrotreating method is proposed in which H ₂ treatment is performed at a temperature of 500 ° C. to 1000 ° C. until an inert gas atmosphere of Pa (1 × 10 ⁻¹ Torr) or less is obtained, and then cooling is performed (JP-A-1-132).
No. 106).

RT produced by the hydrotreating method
The-(M) -B alloy magnetic powder has a large coercive force and magnetic anisotropy. This treatment results in a structure having a very fine recrystallized grain size, that is, an average recrystallized grain size of substantially 0.1 μm to 1 μm, which is magnetically tetragonal Nd ₂ Fe ₁₄ B.
This is because the crystal grain size is close to the single domain critical grain size of the system compound, and these ultrafine crystals are recrystallized to some extent with their crystal orientations aligned.

[0005]

In order for such a crystal structure to have a single orientation direction within the powder particles of about 400 μm or less required for the raw material for bonded magnets, the anisotropic ingot structure of the raw material is required. In order to achieve this, it is necessary to have high properties and a small segregation of the components. For that purpose, it is necessary to simultaneously satisfy the contradictory conditions in casting that a macrostructure with developed columnar crystals is obtained and the crystal structure is sufficiently large. .

However, in the casting of the R-T- (M) -B type rare earth alloy ingot for permanent magnets, the casting structure greatly changes depending on the composition, so that even if the casting conditions are changed, all compositions are anisotropic. It is generally difficult to make all the structures columnar to improve the properties. In particular, in the ingot of the present alloy, columnar crystals are likely to grow by adding excessive R and B to the composition of the intended tetragonal Nd ₂ Fe ₁₄ B type compound phase, but in order to improve the magnetization of the alloy It is not preferable that a phase other than the intended tetragonal Nd ₂ Fe ₁₄ B type compound phase be present, and it was very difficult to satisfy these two contradictory conditions.

According to the present invention, in the casting of a rare earth alloy ingot for an RT- (M) -B type permanent magnet, all the textured parts of the ingot can have an anisotropic degree equivalent to that of columnar crystals. Providing a method for producing an ingot, and further providing a method for producing a rare earth alloy powder having a crystal grain size smaller than that of the ingot and having magnetic anisotropy that is easy to handle and can be produced efficiently, and further It is an object of the present invention to provide a bonded magnet manufacturing method for manufacturing a bonded magnet having excellent magnetic properties from a rare earth alloy powder.

[0008]

In order to complete the present invention, the inventors have made detailed studies on the relationship between the casting structure and composition of the raw material ingot and the casting conditions, and have made the following findings. When the excess R and B are reduced in order to improve the magnetization of the raw ingot, that is, the content of the tetragonal Nd ₂ Fe ₁₄ B-type compound phase in the ingot, the proportion of columnar crystals in the obtained cast structure is reduced. It is reduced and mainly composed of chill crystals, columnar crystals and equiaxed crystals. However, if the ingot size is limited and the cooling conditions are controlled, the equiaxed crystal parts become a texture of dendrite crystals that grow in a constant growth direction, respectively, and as a result, even in the equiaxed crystal parts, regions with the same crystal orientation are formed. As a result, an alloy powder having an anisotropy which is the same as that of the columnar crystal portion even in the equiaxed crystal portion can be obtained. In addition, such excess N
With a composition containing a small amount of d and B, the cast structure can be classified into four or more types along the thickness direction of the ingot, which are a chill crystal, a columnar crystal, an equiaxed crystal, and an iron-rich structure near the central portion. In particular, in the vicinity of the central portion, the composition of Nd and B in the alloy is greatly reduced, the abundance ratio of the tetragonal Nd ₂ Fe ₁₄ B-type compound phase is significantly reduced, and the alloy is not homogenized even by annealing for a long time. It is not possible to obtain high-quality magnetic powder. Therefore, the inventors have variously studied a method in which an iron-rich structure having a small amount of Nd and B in the vicinity of the central portion is not formed, and in the casting conditions of the ingot, the dimensions in the thickness direction and width direction of the ingot cross section are The inventors have found that the cast structure can be controlled by the ratio, and completed the present invention.

That is, according to the present invention, R: 11.5-1.
2.5 at% (at least 1 of rare earth elements including R: Y)
And one or two types of Pr or Nd in R of 50 at% or more), T: 79 to 83 at% (T: F
e or a part of Fe is replaced with 50 at% or less of Co),
M: 0.01 to 2 at% (M: Ga, Zr, Nb, H
f, one or more of Ta), B: 5.5
The cross-sectional dimension of the ingot is 6.5 at% and the width L is 30.
mm or more, thickness d: 10 mm to 35 mm, dimensional ratio L /
d has a relationship of 3.0 or more, tetragonal Nd ₂ Fe ₁₄ B type compound is present in the alloy in an amount of 85% or more, and R is 1 in the ingot.
20% by volume in the region where 1.0% and B are less than 5.0%
% Rare earth alloy ingot for permanent magnets, characterized by not existing.

Further, according to the present invention, the rare earth alloy ingot for a permanent magnet having the above-mentioned structure is annealed at 1120 ° C. to 1160 ° C. for 0.5 hours to 100 hours in an inert atmosphere or vacuum, and then the average grain size is 30 μm to 5000 μm. Crushed into a mixture, and in a temperature increasing process in an H ₂ atmosphere, the temperature range of 600 ° C. to 750 ° C. is increased at a temperature increasing rate of 5 ° C./min to 200 ° C./min, and 750 in H ₂ gas of 10 kPa to 1000 kPa.
° C. to 900 ° C. in heated for 15 minutes to 8 hours, tissues R hydride, T-B compound, T-phase, the hydrogenation disproportionation step of the mixed structure of at least four phases of R ₂ T ₁₄ B compound After that, the absolute pressure of Ar gas or He gas is 100 Pa or more.
700 ° C. while maintaining the hydrogen partial pressure in the furnace at 10 kPa or less in a reduced pressure air flow of 50 kPa or by evacuation.
~ 900 ° C, H ₂ treatment for 5 minutes to 8 hours,
After cooling, the average crystal grain size is 0.05 μm to 1 μm.
And is a method for producing a rare earth alloy powder for a permanent magnet, which is magnetically and anisotropic in crystal orientation.

Further, according to the present invention, the rare earth alloy powder for permanent magnets obtained by the manufacturing method having the above-mentioned constitution is used, and an average particle size of 20 μm to
It is a method for producing a bonded magnet, which comprises pulverizing to 400 μm, mixing the pulverized powder with a resin or a low melting point metal, and molding and solidifying.

Reason for limiting the composition R used in the raw material alloy used in the present invention, that is, the rare earth element, is Y, La, Ce, Pr, Nd, Sm, Gd, T.
b, Dy, Ho, Er, Tm, and Lu are included, at least one of which contains at least one or two of Pr and Nd in an amount of 50 at% or more of R, and all of R is Pr. , Nd may be one or two. The reason why 50 at% or more of R is at least one of Pr and Nd is that sufficient magnetization cannot be obtained at less than 50 at%. If R is less than 11.5 at%, the coercive force and squareness are deteriorated because a large amount of T phase is precipitated in the central portion of the ingot, and if it exceeds 12.5 at%,
In addition to the intended tetragonal Nd ₂ Fe ₁₄ B-type compound, a large amount of R-rich second phase precipitates, and when the amount of this second phase is too large, the magnetization of the alloy is reduced. Therefore, the range of R is 11.5-1
2.5 at%. The preferred range is 11.8-12.
It is 3 at%.

T is an iron group element and includes Fe and Co. When T is less than 79 at%, the second layer has low coercive force and low magnetization.
The phase is crystallized to deteriorate the magnetic properties, and when it exceeds 83 at%, the coercive force and the squareness are deteriorated due to the crystallization of the T phase, so the range of T is set to 79 to 83 at%. Further, even if only Fe is used, the necessary magnetic properties can be obtained, but addition of an appropriate amount of Co is useful for improving the Curie temperature, and Co can be added if necessary. When the atomic ratio of Fe to Co is 50% or less, the amount of decrease in the saturation magnetization of the Nd ₂ Fe ₁₄ B type compound itself becomes large. Therefore, Fe in the atomic ratio of T is set to 50% or more. The preferable range of T is 80 to 82 at%.

The effect of the additional element M is that the decomposition reaction of the mother phase is not completely completed during hydrogenation, and the mother phase, that is, R ₂ T ₁₄ B
An element effective in stabilizing the phase and intentionally remaining is desired. Ga, Zr,
There are Hf, Ta, and Nb. If the addition amount is less than 0.01 at%, the anisotropy will decrease, and if it exceeds 2.0 at%, the second phase that is not ferromagnetic will be precipitated and the magnetization will decrease, so that M is 0.01 to 2. It was 0 at%. The preferable range of M is 0.5 to 1.5 at%.

B is an essential element for stably precipitating a tetragonal Nd ₂ Fe ₁₄ B type crystal structure. When the addition amount is 5.5 at% or less, the R ₂ T ₁₇ phase precipitates to lower the coercive force, and the squareness of the demagnetization curve is significantly impaired. Further, when added in excess of 6.5 at%, the second phase having a small magnetization precipitates to reduce the magnetization of the powder. Therefore,
B was 5.5 to 6.5 at%. A preferred range is 5.8 to 6.3 at%.

Reasons for Limitation of Manufacturing Conditions Reasons for Limitation of Casting Method Generally, the casting structure is determined by the composition of the ingot and the casting conditions, and the present invention is characterized in that it is further controlled by the shape of the ingot. In this invention,
The dimension of the ingot cross section, the thickness: d is 10 to 35 mm, when casting from a crucible containing molten metal into a mold, if the mold thickness is less than 10 mm, it may be difficult in terms of handling in an actual process, Further, it is not preferable because the cost is high due to poor productivity, and when it exceeds 35 mm, even if the ingot width L is substantially infinite, the primary crystal of T is formed in the central portion in the thickness direction of the ingot. Nd and B that crystallize a lot
The structure has a small amount of the component, and in this region, tetragonal Nd ₂
It is not preferable because the abundance ratio of the Fe ₁₄ B type compound phase decreases. Therefore, the ingot thickness: d is set to 10 to 35 mm. Further, the ingot cross-section width: L and the dimensional ratio L / d are such that d is 10
Even if it is mm, L is less than 30 mm, that is, L / d <3.0
Then, when casting the ingot, the region affected by the heat flow direction other than the thickness direction increased, and the crystal orientation of the R ₂ Fe ₁₄ B phase, which is the cause of the anisotropy of the ingot, was oriented in the same direction. The area becomes smaller and the anisotropy decreases. Therefore, L is 30 mm
Above, it is necessary that L / d is 3.0 or more.

In the present invention, the material structure of the mold is not particularly limited as long as it is a metal, a refractory or the like which can be cast with the alloy of the composition of the present invention. It may be selected according to casting conditions, particularly the required cooling rate, and if the ingot thickness is not so thick and the dimension ratio L / d is sufficiently large, an air-cooled iron mold is sufficient, and if necessary, A water-cooled mold made of copper may be used. The thickness of the mold used in the present invention may be a thickness required for the thickness of the ingot. Specifically, it is preferably in the range of about 1/2 to 2 times the thickness of the ingot.
For practical use, it is sufficient to select within the range of 5 to 40 mm.

In the present invention, tetragonal N in the raw material alloy
The content of the d ₂ Fe ₁₄ B-type compound is 85 vo
If it is less than 1%, the magnetic properties deteriorate. More specifically, when the mixed second phase is a primary crystal of T, the coercive force is reduced, and when it is the R-rich phase or the B-rich phase, the magnetization is reduced, so that the tetragonal Nd ₂ Fe ₁₄ B type is used. Abundance ratio of compound is 85v
ol% or more.

Further, the R and B components in the raw material ingot are much lower than the stoichiometric ratio of the tetragonal Nd ₂ Fe ₁₄ B type compound, that is, R <11.0 at% and B <5.0 at.
If the structure of% is present, many phases such as primary crystals of T that reduce the coercive force and squareness remain even after annealing. Therefore R
And B components are 11.0 at% and 5.0 at respectively
It is necessary that no more than 20% of tissues have a ratio of less than 20%.

Reasons for Limiting the Method of Producing Powder Under the annealing conditions of the ingot of the present invention, the annealing temperature is set to 112.
The temperature of 0 ° C. to 1160 ° C. is below 1120 ° C., the solid-phase reaction is the main component, and the diffusion rate is not sufficiently fast, so macrosegregation cannot be eliminated, and grain growth and homogenization due to element diffusion are not sufficient. , The anisotropy of the whole powder when crushed becomes low, and when it exceeds 1160 ° C, a large amount of liquid phase is generated during annealing and it reacts with the container used for annealing, and the equipment becomes large. Not preferable. Therefore, the annealing temperature is 11
It is set to 20 ° C to 1160 ° C. Preferably from 1130 ° C to 1
155 ° C. The reason why the annealing time is set to 0.5 hours to 100 hours is that if it is less than 0.5 hours, the grain growth during the annealing and the homogenization due to the diffusion of the elements are not sufficient, and if it is performed for more than 100 hours, Compared to the case of annealing for a long time, the effect is not significantly changed, and annealing for a long time causes a substantial increase in cost. Therefore, the annealing time is set to 0.5 hours to 100 hours. It is preferably 4 hours to 24 hours.

The coarse pulverization method of the starting material of the present invention may be any one of conventional mechanical pulverization method, natural disintegration by H ₂ occlusion, so-called hydrogen pulverization and the like. The average particle size of the coarsely pulverized powder is limited to 30 μm to 5000 μm because when the average particle size is less than 30 μm, there is a risk of magnetic deterioration due to oxidation of the powder, and when it exceeds 5000 μm, the R hydride phase,
This is because there is a local difference in the progress time of the hydrogenation and disproportionation reactions that phase-separate into the T phase, TB phase, etc., and it becomes difficult to give a large anisotropy.

The hydrotreating method is characterized in that a coarsely pulverized powder having a required particle size does not change its size in appearance and an aggregate having an extremely fine crystal structure can be obtained. That is, for a tetragonal Nd ₂ Fe ₁₄ B type compound, at a high temperature, practically 6
When it is reacted with H ₂ gas in the temperature range of 00 ° C to 900 ° C, it is phase-separated into R hydride phase, T phase, TB phase, etc., and H ₂ gas is removed by H ₂ treatment in the same temperature range. Then,
A recrystallized structure of a tetragonal Nd ₂ Fe ₁₄ B type compound is obtained again. However, in reality, the crystal grain size of the decomposition product and the degree of reaction differ depending on the hydrogenation disproportionation processing conditions, and the metal structure in the hydrogenation disproportionation state has a hydrogenation temperature of 750.
Clearly different below ℃ and above 750 ℃. This difference in the metal structure has a great influence on the magnetic properties of the powder after the dehydrogenation treatment, particularly the magnetic anisotropy. In addition, the state of the ingot before the hydrogenation treatment, especially the grain size, greatly affects the magnetic properties of the magnetic powder after the dehydrogenation treatment, particularly the magnetic anisotropy. Furthermore, depending on the dehydrogenation treatment conditions, tetragonal Nd ₂ F
The recrystallized state of the e ₁₄ B type compound is greatly affected, and the magnetic properties of the magnetic powder produced by the hydrogen treatment method, particularly the coercive force, are greatly affected.

In the present invention, if the rate of temperature rise in H ₂ gas is less than 5 ° C./min, 600 ° C. during the temperature rise process.
Since the decomposition reaction passes through the temperature range of up to 750 ° C., the mother phase, that is, the R ₂ T ₁₄ B phase is not completely decomposed and remains, and the magnetic and crystallographic anisotropy after the dehydrogenation treatment is different. Almost all directions are lost. Further, depending on the treatment conditions, the reaction heat may locally exceed the optimum treatment temperature range due to the large heat of reaction, and thus a practical coercive force may not be obtained. If the heating rate is set to 5 ° C./min or more, the reaction does not proceed sufficiently in the range of 600 ° C. to 750 ° C., and the hydrogenation temperature range of 750 ° C. to 900 ° C. is reached while the mother phase remains. It is possible to obtain a powder having a large magnetic and crystal orientation anisotropy after the elementary treatment.
Therefore, the rate of temperature rise is in the temperature range of 750 ° C or lower.
It is necessary to set it to 5 ° C./min or more. Also, 200 ° C /
A heating rate exceeding min is practically difficult to achieve even if an infrared heating furnace or the like is used, and even if it is possible, the equipment cost becomes excessive, which is not preferable. Therefore, the rate of temperature rise is 5 ° C to 20 ° C.
0 ° C./min.

In the present invention, H in the hydrogenation step
_When the H ₂ gas pressure is less than 10 kPa during holding in ₂ gas, the above-mentioned decomposition reaction does not proceed sufficiently,
If it exceeds kPa, the processing equipment becomes too large, which is industrially unfavorable in terms of cost and safety. Therefore, the pressure range was set to 10 kPa to 1000 kPa. More preferably, it is 50 kPa to 150 kPa.

When the heat treatment temperature in H ₂ gas in the hydrogenation step is less than 600 ° C., R hydride phase, T phase, T-
No decomposition reaction to phase B occurs, and 600-75
In the temperature range of 0 ° C., the hydrogenation and decomposition reactions proceed almost completely because the reaction rate of R hydride formation is fast, and an appropriate amount of R ₂ T ₁₄ B phase does not remain in the decomposition product, resulting in dehydration. Sufficient magnetic or crystallographic anisotropy cannot be obtained after elementary treatment. Further, when the temperature exceeds 900 ° C., the R hydride phase becomes unstable, and the product grains grow to cause tetragonal Nd ₂ Fe ₁₄ B
It becomes difficult to obtain a type compound ultrafine crystal structure. If a region the temperature range 750 ° C. to 900 ° C. the hydrogenation, since the core of the recrystallization reaction upon dehydrogenation R ₂ T ₁₄ B phase is appropriate amount remaining dispersed, after dehydrogenation R ₂ T ₁₄ crystal orientation of the B phase is determined by the residual R ₂ T ₁₄ B phase, the crystal orientation of the resulting recrystallization tissue match the crystal orientation of the material ingot,
At least within the range of the crystal grain size of the raw material ingot, large anisotropy is exhibited. Therefore, the temperature range of the hydrotreatment is set to 750 ° C to 900 ° C. Regarding the heat treatment holding time, 15 minutes or more is required to sufficiently carry out the above decomposition reaction, and if it exceeds 8 hours, the residual R ₂ T ₁₄ B phase decreases and after dehydrogenation treatment. Is not preferable because the magnetic anisotropy of is decreased. Therefore, the heating is maintained for 15 minutes to 8 hours.

The H ₂ removal treatment of the present invention is carried out under reduced pressure or vacuum exhaust in an inert gas, specifically, Ar gas or He gas atmosphere, whereby the substantial H ₂ partial pressure around the powder is reduced. Nearly equilibrium hydrogen pressure, eg 1k at 850 ° C
It becomes about Pa, and the dehydrogenation reaction gradually progresses. The reason for limiting the inert gas to Ar or He is that Ar is easy to use in terms of cost, and He gas is superior in terms of the replaceability of H ₂ gas and the temperature controllability. Other rare gases have no merit in terms of performance and have a problem in cost. Further, N ₂ gas which is generally treated as an inert gas is not suitable because it reacts with a rare earth compound to form a nitride. When the absolute pressure of the atmosphere during depressurization air flow is less than 100 Pa, dehydrogenation reaction occurs rapidly and the temperature drop due to the chemical reaction is large, and furthermore, the dehydrogenation reaction is too rapid, and therefore the crystal structure of the magnetic powder after cooling has coarse crystals. Grains are mixed, and the coercive force is greatly reduced. On the other hand, if the absolute pressure of the atmosphere exceeds 50 kPa,
The dehydrogenation reaction takes too much time, which is a practical problem. Therefore, the absolute pressure of the atmosphere is 100 Pa to 50 kP.
a.

Further, the reason why the dehydrogenation process is carried out in a reduced pressure air flow is to prevent the furnace pressure from rising due to the H ₂ gas released from the raw material by the dehydrogenation reaction.
Practically, an inert gas is introduced from one side, the other side is evacuated by a vacuum pump, and the pressure is controlled by using flow rate adjusting valves attached to each of the supply port and the exhaust port. When dehydrogenation is performed by vacuum exhaust, the pressure is controlled by the dehydrogenation reaction rate, that is, the hydrogen released from the raw material and the vacuum exhaust rate. When the pressure (hydrogen partial pressure) at this time largely deviates from the equilibrium hydrogen pressure, the reaction rate changes, and coarse grains are mixed in the structure of the magnetic powder, or the raw material temperature is lowered due to heat absorption due to rapid dehydrogenation. _The recrystallization reaction into the ₂ Fe ₁₄ B phase becomes incomplete, and the coercive force is greatly reduced. Therefore, the hydrogen partial pressure is 1
It was set to 0 kPa or less.

In the present invention, the temperature for the H ₂ removal treatment is 7
If the temperature is lower than 00 ° C., H ₂ is not released from the R hydride phase, or recrystallization of the tetragonal Nd ₂ Fe ₁₄ B phase compound does not proceed sufficiently. If the temperature exceeds 900 ° C., tetragonal Nd ₂
Although an Fe ₁₄ B phase compound is produced, recrystallized grains grow coarsely and a high coercive force cannot be obtained. Therefore, the temperature range of the H ₂ removal treatment is 700 ° C. to 900 ° C. Further, the heat treatment holding time depends on the exhaust capacity of the treatment equipment, but it is necessary to hold it for at least 5 minutes or more in order to sufficiently perform the recrystallization reaction. On the other hand, on the other hand, if the crystal becomes coarse due to the secondary recrystallization reaction, the coercive force is lowered, so that the time is preferably as short as possible. for that reason,
Heating and holding for 5 minutes to 8 hours is sufficient. The H ₂ removal treatment is
From the viewpoint of preventing the oxidation of the raw materials and also from the viewpoint of the thermal efficiency of the processing equipment, it is preferable to carry out the hydrogenation process continuously.
After hydrotreating, and once cooled the material, again again de H ₂
May be heat treated.

Regarding the recrystallized grain size of the tetragonal Nd ₂ Fe ₁₄ B type compound after the de-H ₂ treatment, it is difficult to obtain an average recrystallized grain size of substantially 0.05 μm or less, and even if it is obtained. Even if there is no advantage in terms of magnetic properties. On the other hand, if the average recrystallized grain size exceeds 1 μm, the coercive force of the powder decreases, which is not preferable. Therefore, the average recrystallized grain size is 0.05 μm
˜1 μm.

Reasons for Limiting the Method of Producing a Bond Magnet In the present invention, the method of pulverizing the rare earth alloy powder by the above-mentioned production method as a raw material for a bond magnet may be a conventional mechanical pulverization method. In the present invention, the average particle size of the powder used to manufacture the bonded magnet is 20 μm to 40 μm.
The reason for limiting the thickness to 0 μm is that if it is less than 20 μm, the magnetic properties may be deteriorated due to the oxidation of the powder, and if it exceeds 400 μm, it is not preferable because it is too coarse for precision molding as a small magnetic component.

Magnetization using the permanent magnet alloy powder according to the present invention may be carried out by any known manufacturing method such as compression molding, injection molding, extrusion molding, roll molding and resin impregnation method shown below. In the case of compression molding, it is obtained by adding and mixing a thermosetting resin, a coupling agent, a lubricant and the like to the magnetic powder, followed by compression molding and curing the heating resin. Further, a low melting point metal such as Zn or Al may be used instead of the resin. For injection molding, extrusion molding, and roll molding,
It can be obtained by adding and mixing a thermoplastic resin, a coupling agent, a lubricant, etc. to the magnetic powder and then molding by any one of injection molding, extrusion molding, and roll molding. In the resin impregnation method, magnetic powder is compression-molded, heat-treated as necessary, impregnated with a thermosetting resin, and heated to cure the resin. Alternatively, the magnetic powder may be obtained by compression molding, heat treatment if necessary, and impregnation with a thermoplastic resin. In the present invention, the weight ratio of the magnetic powder in the bonded magnet varies depending on the manufacturing method, but is 70 to 99.5 wt%, and the remaining 0.5 to 30 wt% is resin or the like. In the case of compression molding, the weight ratio of magnetic powder is 95 to 99.5 wt%, in the case of injection molding, the filling rate of magnetic powder is 90 to 95 wt%,
In the resin impregnation method, the weight ratio of the magnetic powder is 96 to 99.
5 wt% is preferable. As the resin in the present invention, those having any of thermosetting and thermoplastic properties can be used, but a thermally stable resin is preferable, and examples thereof include polyamide, polyimide, phenol resin, fluororesin, silicon resin and epoxy. A resin or the like can be appropriately selected.

[0032]

According to the present invention, a tetragonal Nd ₂ Fe ₁₄ B-type compound is obtained by specifying the cross-sectional dimension ratio of the ingot during the production of the RT- (M) -B system rare earth alloy ingot for permanent magnet. 85
% Or more to obtain an ingot having a low concentration of 20% or more of R and B regions, and to substantially columnarize the structure. For example, anisotropy is the same as that of columnar crystal. Have
A magnet alloy powder having high magnetic properties can be obtained by homogenization by predetermined annealing. Further, the present invention, by annealing the above ingot in a specific atmosphere, hydrogenation treatment in H ₂ gas under specific temperature rising conditions and atmospheric conditions, and further cooling after deH ₂ treatment under specific conditions, It is possible to obtain a rare earth alloy powder having a fine crystal grain size and magnetic anisotropy to manufacture a bond magnet having excellent anisotropy, high magnetization and coercive force.

[0033]

【Example】

Example 1 No. 1 shown in Table 1 obtained by the high frequency induction melting method. 1
It melted by casting the molten metal of the composition of-8 into the iron mold of the size shown in Table 4. No. at this time Fig. 1 shows changes in the R and B components in the thickness direction of the four ingots. This ingot is shown in Table 4
Annealing was performed in an Ar atmosphere under the heat treatment conditions shown in (1) to make the volume ratio of the tetragonal Nd ₂ Fe ₁₄ B type compound in the ingot 90% or more. Furthermore, this ingot was placed in an Ar gas atmosphere (O ₂
(Amount of 0.5% or less) was roughly crushed with a stamp mill to the average particle size shown in Table 4, and the coarsely crushed powder was put into a tubular furnace to obtain 1P.
It was evacuated to below a. Then, the purity is 99.999
While introducing 9% or more of H ₂ gas, the treatment was performed under the hydrotreatment conditions shown in Table 4. The hydrogenated raw material thus obtained was subsequently subjected to dehydrogenation treatment under the dehydrogenation treatment conditions shown in Table 4. A rotary pump was used for evacuation. After cooling
The raw material was taken out when the raw material temperature became 50 ° C. or lower. Table 4 shows the magnetic characteristics of the magnet alloy powder at this time.

Example 2 No. 1 in Table 4 obtained in Example 1 After crushing the magnet alloy powder of No. 10 into a powder having an average particle size of 150 μm in a stamp mill in an Ar gas atmosphere (O ₂ amount of 0.5% or less),
Mix 2.5 wt% of cresol novolak resin,
Molding was performed by applying a pressure of 0.6 GPa in a magnetic field of 1.2 MA / m. The green compact thus obtained was cured in an Ar atmosphere at 160 ° C. for 1 hour to obtain a 10 mm square cubic bonded magnet. Table 2 shows the magnetic characteristics measured by the BH tracer.

Comparative Example 1 Molten metal having eight kinds of compositions having the same composition as in Example 1 shown in Table 1 was cast into an iron mold having dimensions shown in Table 5. No. at this time FIG. 2 shows changes in the components of Nd and B in the thickness direction of the four ingots. The ingot thus obtained was annealed in an Ar atmosphere under the heat treatment conditions shown in Table 5,
After roughly pulverizing with a stamp mill in a gas atmosphere (O ₂ amount of 0.5% or less) to the average particle size shown in Table 5, the mixture was placed in a tubular furnace.
It was evacuated to 1 Pa or less. Then, the purity is 99.9.
While introducing 999% or more of H ₂ gas, hydrogenation treatment and dehydrogenation treatment were performed under the treatment conditions shown in Table 5. Table 5 shows the magnetic characteristics of the magnet alloy powder at this time.

Comparative Example 2 No. 1 obtained in Comparative Example 1 150 powders of 10 powders in an Ar gas atmosphere (O ₂ amount of 0.5% or less) by a stamp mill
After pulverizing to a powder having an average particle size of μm, 2.5 wt% of cresol novolac resin was mixed and molded by applying a pressure of 0.6 GPa in a magnetic field of 1.2 MA / m. The obtained green compact was cured in an Ar atmosphere at 160 ° C. for 1 hour,
A 10 mm square cubic bonded magnet was used. Table 3 shows the magnetic properties measured by the BH tracer.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4]

[0041]

[Table 5]

[0042]

The present invention is the same as RT-T-
In manufacturing a rare earth alloy ingot for (M) -B system permanent magnet,
By specifying the cross-sectional dimension ratio of the ingot, tetragonal Nd ₂
Fe ₁₄ B type compound is 85% or more to obtain a low concentration ingot without R and B regions, and to substantially columnarize the structure,
For example, an equiaxed crystal portion has anisotropy similar to that of a columnar crystal portion and can be homogenized by a predetermined annealing to obtain a magnetic powder having high magnetic properties. Further, the present invention, by annealing the above ingot in a specific atmosphere, hydrogenation treatment in H ₂ gas under specific temperature rising conditions and atmospheric conditions, and further cooling after deH ₂ treatment under specific conditions, It is possible to obtain a rare earth alloy powder having a fine crystal grain size and magnetic anisotropy to manufacture a bond magnet having excellent anisotropy, high magnetization and coercive force.

[Brief description of drawings]

1 is an example No. 1; It is a graph which shows the ingredient (at%) change of Nd and B in the thickness direction of 4 ingots.

2 is a comparative example No. It is a graph which shows the ingredient (at%) change of Nd and B in the thickness direction of 4 ingots.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location H01F 1/06 1/08 7/02 C (72) Inventor Seiichi Hosokawa Egawa, Shimamoto-cho, Mishima-gun, Osaka Prefecture 2-15-17 Sumitomo Special Metals Co., Ltd. Yamazaki Works (72) Inventor Minoru Uehara 2-15-17 Egawa Shimamoto-cho, Mishima-gun, Osaka Prefecture Sumitomo Special Metals Co., Ltd. Yamazaki Works (72) Inventor Satoshi Hirosawa Osaka 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Sumitomo Special Metals Co., Ltd. Yamazaki Works (72) Inventor Toshiro Tomita 4-53-3 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd.

Claims (3)

[Claims] 1. R: 11.5-12.5 at% (R: Y
At least one of rare earth elements including, and containing one or two of Pr or Nd in R of 50 at% or more), T: 79 to 83 at% (T: Fe or a part of Fe of 50 at% or less) Replaced with Co), M: 0.01-2
at% (one or more of M: Ga, Zr, Nb, Hf, and Ta), B: 5.5 to 6.5 at%, and the sectional dimension of the ingot has a width L of 30 mm or more, Thickness d:
10 to 35 mm, the dimensional ratio L / d has a relationship of 3.0 or more, the tetragonal Nd ₂ Fe ₁₄ B type compound is present in the alloy in an amount of 85% or more, and R in the ingot is 11.0. % And B are less than 5.0% in a volume ratio of 20% or more does not exist, a rare earth alloy ingot for a permanent magnet. 2. The rare earth alloy ingot for a permanent magnet according to claim 1, after being annealed at 1120 ° C. to 1160 ° C. for 0.5 hours to 100 hours in an inert atmosphere or vacuum, an average grain size of 3
It is crushed to 0 μm to 5000 μm and heated in a H ₂ atmosphere in a temperature range of 600 ° C. to 750 ° C. at a heating rate of 5
℃ / min ~ 200 ℃ / min to raise the temperature, 10kPa ~
1 at 750 ° C to 900 ° C in H ₂ gas of 1000 kPa
After heating and holding for 5 minutes to 8 hours, the structure is made into a mixed structure of at least four phases of R hydride, T-B compound, T phase, and R ₂ T ₁₄ B compound. After the hydrogenation disproportionation step, Ar gas is further added. Alternatively, the hydrogen partial pressure in the furnace is reduced to 10 in a depressurized air flow of 100 Pa to 50 kPa absolute pressure by He gas or by evacuation.
While maintaining at kPa or lower, 700 ° C. to 900 ° C. is heated and held for 5 minutes to 8 hours for de-H ₂ treatment, and then cooled to have an average crystal grain size of 0.05 μm to 1 μm. A method for producing a rare earth alloy powder for a permanent magnet, which has anisotropy. 3. The rare earth alloy powder for permanent magnets obtained by the manufacturing method according to claim 2, is pulverized to an average particle size of 20 μm to 400 μm, and the pulverized powder is mixed with a resin or a low melting point metal to be molded and solidified. A method for manufacturing a bonded magnet.