JP3143157B2 - Manufacturing method of rare earth permanent magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth permanent magnet having excellent magnetic properties and used for various electric and electronic devices.

[0002]

2. Description of the Related Art Among rare earth magnets, Nd-Fe-B magnets are:
In recent years, Nd, which is a main component, is abundant in resources, low in cost, and excellent in magnetic properties, and thus its use has been expanding in recent years. Research and development for improving magnetic properties has been energetically conducted since the invention of the Nd-based magnet, and many studies and inventions have been proposed. There are many methods for manufacturing high-performance Nd magnets by mixing and sintering two types of alloy powders having different compositions, which is one of the methods for manufacturing Nd-based sintered magnets (hereinafter referred to as the two-alloy method). Inventions have been proposed.

The two alloy methods proposed so far can be roughly classified into three types. In the first method, one of the raw material alloy powders to be mixed is made into an amorphous or microcrystalline alloy by a liquid quenching method, and a normal rare earth alloy powder is mixed therewith, or both raw material alloy powders are mixed together. A method of producing and mixing by a liquid quenching method [JP-A-63-9
3841, JP 63-115307, JP 63-252403, JP Akira 63 -278
208, JP-A-1-108707, JP-A-1-46310, JP-A-1-146309,
Japanese Patent Application Laid-Open No. 1-155603]. Recently, a 50MG alloy using this liquid quenching alloy has been
Reported that magnetic properties exceeding Oe were obtained [E. Otuki, T. Otuka
and T.Imai; 11th.Int.Workshopon Rare Earth Magnet
s, Pittsburgh, Pennsylvania, USA, October (1990), p. 328
See].

A second method is to prepare an alloy in which the two kinds of raw material alloy powders to be mixed are changed mainly as R ₂ Fe ₁₄ B compounds and the kinds and contents of the rare earth elements contained therein are mixed and sintered. Is the way. That is, a method of mixing two kinds of alloys in which the amount ratio of the contained Nd-rich phase or the kind of the rare earth element is changed [Japanese Patent Application Laid-Open Nos. 61-81603, 61-81604 and 61-816]
05, JP-A-61-81606, JP-A-61-81607, JP-A-61-11900
7, JP 61-207546, JP 63-245 90 3, Hei 1-177335 is the JP reference.

The third method is to use one of the alloys mainly as R ₂
A method of producing an Nd-based rare earth magnet by mixing and sintering powders of various low-melting elements, low-melting alloys, rare-earth alloys, carbides, borides, hydrides and the like into an alloy powder composed of an Fe ₁₄ B compound [ JP-A-60-230959, JP-A-61-263201, JP-A-62-1
81402, JP-A-62-182249, JP-A-62-206802, JP-A-62-270
746, JP-A-63-6808, JP-A-63-104406, JP-A-63-114939,
JP-A-63-272006, JP-A-1-111843, and JP-A-1-146308.

[0006]

There are many points that the two-alloy method according to the prior art is not suitable or insufficient for realizing the truly excellent magnetic properties of Nd-based magnet alloys. That is, in the first method described above, the energy product of the magnet alloy is high, but the coercive force is about 9 kOe, and the coercive force decreases with increasing temperature. Magnet properties. The biggest problem is the magnetic field orientation. In the first method, an alloy exhibiting magnetism at room temperature can be obtained by appropriately selecting the composition. However, since the alloy obtained by the liquid quenching method becomes an amorphous amorphous phase or a fine crystal, the alloy is formed into a fine powder and a magnetic field. A specific crystal orientation cannot be oriented in the direction of the magnetic field even if it is oriented in a magnetic field. Therefore, the orientation of the molded body obtained even when the mixed raw material alloy powder is molded in a magnetic field is poor,
After sintering, sufficient magnet properties cannot be obtained.

In the second method, R ₂ in the magnet alloy is
The phase coexisting with Fe ₁₄ B compound is Nd rich phase or Nd _{1 + X}
Fe ₄ B ₄ phase, both of which do not show magnetism at room temperature. Therefore, the presence of a compound having no magnetism disturbs the orientation, and a magnet having excellent magnetic properties cannot be obtained.
Also, in the third method using various elements and various compounds as powders to be mixed, since these compounds do not have magnetism, the demagnetizing field increases during orientation in a magnetic field, and the effective magnetic field strength decreases. Therefore, the rotation of the magnetic particles in the direction of the magnetic field becomes insufficient, and the orientation is disturbed.

In the third method, there is a proposal to improve the magnetic properties by using a low melting point element or alloy in the powder to be mixed. This is based on the idea that nucleation sites such as lattice defects and oxide phases existing at the grain boundaries of the R ₂ Fe ₁₄ B compound are removed and the grain boundaries are cleaned to improve the coercive force. However, the presence of the low melting point phase is actually a disadvantageous condition for improving the magnetic properties for the following reasons. If the low-melting phase is melted from, for example, around 660 ° C., the viscosity of the low-melting phase becomes considerably small at an actual sintering temperature of 1,100 ° C. As a result, the compact shrinks due to liquid phase sintering, and at the same time, the viscosity of the melt surrounding the grains is low, so that the rotation of the magnetic particles easily occurs, the orientation is disturbed, and the magnetic properties deteriorate. In other words, a desirable liquid phase component in the liquid phase sintering of the Nd magnet needs to maintain an appropriate viscosity without disturbing the orientation of the particles, and also to densify the compact and sufficiently clean up the grain boundaries. In the conventional two-alloy method, the roles of the magnetic field orientation and the coercive force improvement involving the liquid phase component are both sufficiently taken into consideration, and the magnetism and melting point of the liquid phase alloy component are appropriately adjusted so that these become the optimum conditions. I didn't adjust it. An object of the present invention is to improve the above-mentioned drawbacks of the two-alloy method and to provide a method for producing a rare-earth permanent magnet having excellent balanced magnetic properties.

[0009]

Means for Solving the Problems In order to solve the above problems, the present inventors have basically reviewed the two-alloy method, and it is sufficient to properly select and combine the types and characteristics of the constituent phases of the magnetic material. The present inventors have found that satisfactory and well-balanced magnetic properties can be obtained, and have studied the manufacturing conditions in detail to complete the present invention. The gist of the present invention is that the alloy A is mainly composed of R ₂ T ₁₄ B
Phase (here R is, Nd, Pr, at least one or more rare earth elements mainly containing Dy, T represents Fe and Co) and alloys consisting of, a B alloy containing R, Co, Fe, and B and R ₂ T ¹ ₁₄ B phase and / or the R-rich phase as a phase in the alloy (in which R is as defined above, T ¹ represents a transition metal element mainly Fe, a Co) and RT ² ₄ Phase B, RT ²
_3-phase, RT ² _2-phase, R ₂ T ² ₇ phase and RT ² ₅ phase (wherein R is as defined above, the transition metal element T ² are mainly Fe, and Co, or the transition metal elements and B 5)
An alloy consisting of one or more of the above phases, and a B alloy powder in an amount of 99 to 70% by weight of the A alloy powder.
-30% by weight, and press-molding the mixed alloy powder in a magnetic field, sintering the compact in a vacuum or inert gas atmosphere, and further aging heat treatment at a low temperature below the sintering temperature to contain Co A method for producing a rare earth permanent magnet, characterized in that the magnet alloy comprises
T ² ₄ B-phase, RT ² _3-phase, RT ² _2-phase, R ^₂ T _{2 7} phase and RT ² _5-phase five of at least one or more phases of the constituent phases melting point 1,155 ° C. or less of 700 ° C. or higher An intermetallic compound, wherein at least one phase is a magnetic material having a Curie temperature of room temperature or higher, and at least one phase is a magnetic material having a Curie temperature of room temperature or higher and crystal magnetic anisotropy This is a method for producing a rare earth magnet.

Hereinafter, the present invention will be described in detail. The present invention relates to a rare-earth permanent magnet (hereinafter referred to as a magnet alloy C) called a so-called two-alloy method.
A) as a raw material is mainly composed of an R ₂ T ₁₄ B compound phase, and R is Y containing La, Ce, P
It is at least one or more rare earth elements mainly composed of Nd, Pr, and Dy selected from r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. T represents Fe and Co, and the Co content is 0.1 to 40% by weight. The addition of Co increases the Curie temperature of the A alloy and also improves the corrosion resistance of the alloy. The alloy A is prepared by melting a raw metal in a vacuum or an inert gas, preferably an Ar atmosphere. As a raw material metal, a pure rare earth element or a rare earth alloy, pure iron, ferroboron, or an alloy thereof is used, but a trace impurity inevitable in general industrial production is included. In the obtained ingot, since the R ₂ Fe ₁₄ B phase is formed by the peritectic reaction between αFe and the rare-earth rich phase, the αFe phase, R-rich phase, B-rich phase, Nd3C
An o-phase or the like may remain. In the present invention, it is desirable that the amount of the R ₂ Fe ₁₄ B phase in the A alloy is large, so that a solution treatment is performed as necessary. The heat treatment may be performed in a vacuum or Ar atmosphere at a temperature of 700 to 1,200 ° C. for 1 hour or more.

The B alloy is an alloy mainly composed of R, Co, Fe, and B , and has a composition formula RaFebCocBd (where R is Y
La, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er,
At least one or more rare earth elements mainly composed of Nd, Pr and Dy selected from Tm, Yb and Lu, 15 ≦ a ≦ 40, 0 ≦ b
≤ 80, 5 ≤ c ≤ 85, 0 ≤ d ≤ 20, a + b + c + d = 100 (atomic%)). Is melted and cast in an Ar atmosphere. As a raw material metal, a pure rare earth element or a rare earth alloy, pure iron, pure cobalt, ferroboron, or an alloy thereof is used, but a trace impurity inevitable in general industrial production is included. Rare earth element R
Amount a is not obtained a sufficient amount of liquid phase at the sintering step for R is too small it is less than 15 atomic%, no longer rise density of the sintered body, is a 40 atomic percent is exceeded and alloy melting point It becomes too low and the effect of improving the magnetic properties is lost. RT ² ₄ B phase in an amount c is less than 5 atomic% of Co, RT ² _3-phase, RT ² ₂
Phases, each phase of the R ₂ T ² ₇ phase and RT ² ₅ equality is no longer appear, not the effect of improving magnetic characteristics. Further, a B alloy can be produced by heat-treating a ribbon obtained by the liquid quenching method. That is, in the liquid quenching method, the B alloy after quenching is in an amorphous phase or a fine crystalline phase. By heating this at a temperature higher than the crystallization temperature for a certain period of time, crystallization or recrystallization growth is performed. Thus, the predetermined constituent phase of the present invention can be precipitated.

[0012] Phase mainly appears in B alloy in this composition range, R ₂ T ¹ ₁₄ B phase (mainly R ₂ Fe ₁₄ B phase)
R-rich phase (wherein R is as defined above, T ¹ represents a transition metal element Fe, a Co mainly) and RT ² ₄ B-phase,
RT ² _3-phase, RT ² _2-phase, R ^₂ T _{2 7} phase and RT ² ₅
Phase (here, R is the same as above, and T ² is a transition metal element mainly composed of Fe or Co, or the transition metal element and B), and the like in the present invention. It is characterized in that a B alloy containing at least one or two or more phases is used. The phase described as R-rich phase is R-phase.
It is intended to represent all of the various R-rich phases whose components are at least 35 atomic%. Of these seven phases, R ₂ Fe ₁₄ B
The two phases, the R-rich phase and the R-rich phase, are phases that have also appeared by a conventionally known two-alloy method or a normal rare-earth iron-boron-based magnet alloy manufacturing method. Remaining RT ² ₄ B phase, RT ² ₃ phase, R
T ² _2-phase, R ₂ T ² ₇ phase, five phase RT ² ₅ phase,
Appears by adding 5 atomic% or more of Co to the B alloy and is unique to the two-alloy method of the present invention. These five phases first appeared as an equilibrium phase in the B alloy by adding 5 atomic% or more of Co. FIG. 1 shows an example in which a photograph of the casting structure of the alloy B of the present invention was taken with a scanning electron microscope and the composition was determined by EPMA (electron probe X-ray microanalyzer) and X-ray diffraction . RT ²
₄ Phase B; RT ² _3-phase, 3. RT ² ₂ phase, 4. The presence of the R-rich phase is clearly shown. The two-alloy method according to the present invention is characterized in that at least one of these five phases is contained in the B alloy, and the presence of these phases realizes high magnetic properties for the magnet alloy produced by the two-alloy method. I was able to.

In the present invention, the above alloys A and B are mixed at a specific ratio, and a magnet alloy C is produced by a so-called two-alloy method, whereby high magnetic properties can be exhibited. Less than,
The reason why the presence of these mixed phases in the B alloy resulted in the high magnetic properties of the magnet alloy will be described. The first reason is that these mixed phases have a Curie temperature above room temperature, which was achieved by the additive element Co. Further, these phases have magnetocrystalline anisotropy in a specific crystal direction. Therefore, when a B alloy powder containing one or more of these phases as a main constituent phase is mixed with an A alloy powder mainly composed of R2Fe14 B phase and oriented in a magnetic field, the B alloy is also a ferromagnetic material and has a different magnetic property. Since it has anisotropy, almost all particles are oriented with the crystal direction aligned in the direction of the applied magnetic field, and high magnetic properties can be obtained.

The second reason is that the melting points of these phases are in a temperature range suitable for liquid phase sintering of Nd-based rare earth magnets, ie, 700 ° C.
It should be in the range of not less than 1,155 ° C. This temperature range is higher than the melting point of the Nd-rich phase (500-650 ° C),
In addition, the temperature is lower than the melting point of the R ₂ Fe ₁₄ B phase (1,155 ° C.). Therefore, at the normal sintering temperature, only the Nd-rich phase is present and the viscosity of the melt does not decrease too much, so that the orientation of the particles is not disturbed, and the liquid phase is formed. The density is increased while cleaning the grain boundaries, and high magnet properties are realized after sintering. Another effect of the addition of Co is an improvement in corrosion resistance. The B alloy contains more rare earth elements than the A alloy and thus is easily oxidized and deteriorated. However, by adding Co, the oxidized deterioration can be prevented and stable magnetic properties can be obtained. Addition of Co to the A alloy also improves the corrosion resistance of the alloy, reduces oxidative degradation, and provides stable magnetic properties. Dy added to the B alloy is present in the vicinity of the grain boundary even after co-sintering, and has an effect of improving the coercive force of the magnet alloy C.

Next, a method for producing the magnet alloy C by the two-alloy method will be described. The A alloy and the B alloy obtained as described above are separately mixed and then mixed at a predetermined ratio. The pulverization is performed by wet or dry pulverization. Rare earth alloys are very active, and are used in an atmosphere such as Ar or nitrogen in the case of dry grinding and in a non-reactive organic solvent such as Freon in the case of wet grinding in order to prevent oxidation during grinding. Done. The mixing step is also performed in an inert atmosphere or a solvent as necessary. The pulverization is generally performed stepwise as coarse pulverization and fine pulverization, but mixing may be performed at any stage.
That is, a predetermined amount may be mixed after coarse pulverization and then finely pulverized, or may be mixed at a predetermined ratio after all pulverization is completed. It is necessary that both the A and B alloys are uniformly mixed with substantially the same average particle size. The average particle size is preferably in the range of 0.5 to 20 μm, and if it is less than 0.5 μm, it is easily oxidized and deteriorated.
If it exceeds sinterability, the sinterability deteriorates.

The mixing ratio of the A alloy powder and the B alloy powder is
It is preferable to mix the B alloy powder in the range of 1 to 30% by weight with respect to 99 to 70% by weight of the alloy powder. If it exceeds 30% by weight, the proportion of the nonmagnetic phase after sintering becomes too large, and the residual magnetic flux density becomes small. The obtained mixed powder of the alloy A and the alloy B is molded into a desired size by a molding press in a magnetic field, and further subjected to a sintering heat treatment. The sintering is performed in a vacuum or argon atmosphere at a temperature in the range of 900 to 1,200 ° C. for 30 minutes or more, followed by an aging heat treatment at a temperature lower than the sintering temperature for 30 minutes or more. After sintering, magnet alloy C
The compact has a density of 95% or more in terms of true density, so that a high residual magnetic flux density can be obtained.

[0017]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described with reference to examples, but the present invention is not limited thereto. (Example 1, Comparative Example 1) An alloy having a composition formula of 12.5Nd-6B-1.5Co-80Fe (each atomic%) was prepared using Nd and Fe metal having a purity of 99.9% by weight and ferroboron in an Ar atmosphere of a high-frequency melting furnace. After ingot casting, the ingot was solution-solutioned at 1,070 ° C. in an Ar atmosphere for 20 hours.
This is an A1 alloy. Next, 99.9% by weight of N
d, Dy, Fe, Co Using metal and ferroboron, formula 20Nd-
An alloy of 10Dy-20Fe-6B-44Co was melt-cast in an Ar atmosphere using a high-frequency melting furnace to obtain a B1 alloy. The A1 alloy ingot and the B1 alloy ingot were each separately coarsely pulverized in a nitrogen atmosphere to 30 mesh or less, and then the A1 alloy coarse powder was weighed to 90% by weight and the B1 alloy coarse powder was weighed by 10% by weight and replaced with nitrogen. Mix in V blender for 30 minutes. This mixed coarse powder was finely pulverized with a jet mill using high-pressure nitrogen gas to an average particle size of about 5 μm. 15 kOe of the obtained mixed fine powder
Press molding at a pressure of about 1 Ton / cm ² while orienting in a magnetic field. Next, this compact was sintered in a sintering furnace in an Ar atmosphere at 1,070 ° C. for 1 hour, and further subjected to aging heat treatment at 530 ° C. for 1 hour and rapidly cooled to produce a magnet alloy C1.

For comparison, an alloy having the same composition as in Example 1 was produced by a conventional one-alloy method, and Comparative Example 1 was obtained. That is,
The same composition (magnet alloy C1) as after mixing both alloys A1 and B1 was weighed from the beginning, melted, pulverized, sintered, and subjected to aging heat treatment.
The magnet characteristics were compared with the magnet by the alloy method (magnet composition C1 of Example 1). The composition of this magnet alloy C1 was 13.1 Nd- in both Example 1 by the two-alloy method and Comparative Example 1 by the one-alloy method.
0.8Dy-4.5Co-6.0B-75.6Fe. Table 1 shows the values of the magnetic properties and the sintered body densities obtained for both sintered body magnets of Example 1 and Comparative Example 1. The magnetic properties of Example 1 are almost the same as those of Comparative Example 1, but the density of the sintered body is almost the same. However, Example 1 is far superior in all values such as residual magnetic flux density, coercive force, and maximum energy product. I have. As described above, even if the composition of the magnet alloy C is exactly the same, there is a considerable difference in the magnetic properties, indicating that the two-alloy method is a very effective method for improving the magnetic properties of the Nd magnet. The metal structure of the B1 alloy in the cast state is shown in FIG. 1 by a backscattered electron image photograph of a scanning electron microscope. As can be seen from the light and dark of the photograph, there are four main constituent phases in the B1 alloy. Each phase is analyzed by EPMA (electron probe X-ray microanalyzer) and X-ray analysis.
RT ² ₄ B-phase as shown in FIG, RT ² _3-phase, RT ² ₂ phase,
It turned out to be an R-rich phase.

(Examples 2 to 9 , Comparative Examples 2 to 9 ) As shown in Table 1, corresponding to the alloy compositions of Examples 2 to 9 , the compositions of A1, A3, A5 to A7 , and A9 as A alloys Make an alloy,
A composition alloy of B2, B4 to B7 , and B9 was prepared as a B alloy, pulverized in the same manner as in Example 1, mixed in a predetermined ratio, molded in a magnetic field, and sintered (1,050 to 1,120 ° C. × 1 hour). performs an aging treatment (500 ~600 ℃ × 1~10 hours) to produce a 2 alloy method magnet alloy C2~C 9, tables 1 and 2 to measure its magnetic properties
It was also described in. Except prepared by alloy 1 alloy method having the same composition as in Example 2-9 for comparison to produce magnet alloy C2～C 9 by the same conditions as in Example 2-9, Comparative Example to measure the magnetic properties 2 to 9 are shown in Tables 1 and 2.

[0020]

[Table 1]

[Table 2]

[0021]

The rare-earth permanent magnet produced according to the present invention has several steps of superior magnetic properties to the conventional rare-earth magnet having the same composition by effectively utilizing expensive additional elements, and has high coercive force and high coercivity. It has become possible to provide a high-performance magnet with a good balance of residual magnetic flux density and high energy product. Therefore, it is expected that it will be widely used as a high-performance magnet for various electric and electronic devices in the future.

[Brief description of the drawings]

FIG. 1 is a metallographic view of a cast state of a B1 alloy of Example 1 by a scanning electron micrograph.

[Explanation of symbols]

1 RT ² ₄ B-phase 2 RT ² _3-phase 3 RT ² ₂ Phase 4 R-rich phase

Continuation of the front page (56) References JP-A-2-288305 (JP, A) JP-A-1-111184 (JP, A) JP-A-63-313807 (JP, A) JP-A-3-250607 (JP) , A)

Claims (5)

(57) [Claims] 1. An alloy A mainly composed of an R ₂ T ₁₄ B phase (where R represents at least one or more rare earth elements mainly composed of Nd, Pr, and Dy, and T represents Fe and Co). , B
Alloy R, Co, Fe, and containing B, and R ₂ T ¹ ₁₄ B phase and / or the R-rich phase as a phase in the alloy (in which R is as defined above, T ¹ is mainly Fe, and Co and a transition metal element represents a) and RT ² ₄ B phase, RT ² _3-phase, RT ² _2-phase, R ₂ T ²
₇ phase and RT ² ₅ phase (where R is as above, T ² is Fe,
A transition metal element mainly composed of Co or a mixed phase of one or more of the five phases of the transition metal element and B); B alloy powder is mixed in an amount of 1 to 30% by weight with respect to 70% by weight, the mixed alloy powder is molded under pressure in a magnetic field, and the molded body is sintered in a vacuum or an inert gas atmosphere. A method for producing a rare-earth permanent magnet, comprising aging heat treatment at a low temperature equal to or lower than a temperature to obtain a Co-containing magnet alloy. 2. The RT contained in the B alloy according to claim 1.
² ₄ B-phase, RT ² _3-phase, RT ² _2-phase, R ^₂ T _{2 7} phase and RT ² ₅
The melting point of at least one of the five constituent phases of the phase
A method for producing a rare earth permanent magnet, which is an intermetallic compound having a temperature of 700 ° C. or more and 1,155 ° C. or less. 3. A rare earth magnet, wherein at least one of the five constituent phases contained in the B alloy according to claim 1 or 2 is a magnetic material having a Curie temperature of room temperature or higher. Manufacturing method. 4. A magnetic material in which at least one of the five constituent phases contained in the B alloy according to claim 1 or 2 or 3 has a Curie temperature of room temperature or higher and a magnetocrystalline anisotropy. A method for producing a rare earth magnet, comprising: 5. A method for producing a rare earth magnet, wherein the average particle size of the A alloy, B alloy and AB mixed alloy powder according to claim 1 is in the range of 0.5 to 20 μm.