JP2002083705A - Anisotropic rare earth sintered magnet and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an Sm2Co17-based sintered magnet which has superior magnetic characteristics and optimum temperature range of sintering and solution treatment which is wider than that of the conventional one. SOLUTION: Sm2Co17-based permanent magnet alloy is composed of R (where R is Sm or at least two kinds of rare earth elements containing Sm of at least 50 wt.%) of 20-30 wt.%, 10-45 wt.% Fe, 1-10 wt.% Cu, 0.5-5 wt.% Zr, 0.01-1.0 wt.% Ti, residue Co and unavoidable impurities. In crystal texture of the alloy, TbCu7 type crystal structure of at least 50 vol.% is contained. The alloy is ground, molded, sintered, solved and then aged, and an anisotropic rare earth sintered magnet, where (BH)max is at least 25 MGOe, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a Sm ₂ Co ₁₇ based sintered magnet and a method for producing the same.

[0002]

2. Description of the Related Art
The method for producing a sintered magnet in a Sm ₂ Co _17- based permanent magnet is as follows.
After pressure molding in a magnetic field, the
At 100-1300 ° C, usually around 1200 ° C, 1
Sinter and solution under conditions of ~ 5 hours. Then 700 ~
It is a general practice to carry out an aging treatment in which the temperature is maintained at 900 ° C., usually about 800 ° C. for about 10 hours, and gradually cooled to 400 ° C. or less at a temperature lowering rate of −1.0 ° C./min. In the normal process, sintering and solution treatment are ± 3
There is an optimum temperature range of ° C, and strict control is required. This is because, during sintering and solution treatment, the presence of various types of constituent phases causes the growth of crystal grains due to portions and the variation of the phase change due to the heat treatment temperature, and the high characteristic Sm ₂ Co ₁₇ As the system sintered magnet becomes, the temperature control tends to be strict. In order to maintain the optimum temperature range and obtain good magnetic properties, a uniform alloy structure with as little segregation as possible is indispensable.

As a casting method for obtaining a Sm ₂ Co _17- based magnet alloy having a uniform structure, a method of casting a molten alloy in a box-shaped mold or the like so that the macro structure becomes a columnar crystal is adopted. ing. Here, in order to obtain columnar crystals, the cooling rate of the molten alloy must be increased to some extent, but in the casting method using a box-shaped mold, in the center of the ingot, the cooling rate is lower than the cooling rate at which the columnar crystals are generated. This tends to cause coarsening of the structure and generation of equiaxed crystals. Although this problem can be solved by a method such as reducing the thickness of the ingot, efficient productivity is reduced. For this reason, an ingot having a certain thickness is produced, and the structure is coarsened and an equiaxed crystal is often generated. The coarsening of the structure and the generation of equiaxed crystals result in the segregation of the ingot, which has a bad influence on the magnet structure after sintering and solution treatment, and causes no good magnetic properties to be obtained.

As a method for solving this problem, a casting method using a single roll (strip casting method) has been proposed (JP-A-8-260083). The structure of the ingot manufactured by this method has a fine crystal structure and is considered to be uniform in the macro structure. However, the constituent phase of the Sm ₂ Co _17- based permanent magnet alloy after casting is usually the same regardless of whether it is an ingot cast by a box mold or an ingot manufactured by a strip casting method. ₂ Zn
₁₇ phase, Th ₂ Ni ₁₇ phase, 1-7 phase, 1-5 phase, 2-phase
Even if a sintered magnet is manufactured using an ingot cast by a strip casting method, the sintered magnet is manufactured in the same manner as in the case of using an ingot cast in a box mold as a raw material. The solution treatment has an optimum temperature range of ± 3 ° C. and requires strict control.

[0005] When a sintered magnet is manufactured using an ingot having a fine crystal structure as a raw material, the coercive force is improved as compared with a sintered magnet using an ingot cast with a box-shaped mold as a raw material. It has been confirmed that the residual magnetic flux density, the maximum energy product, and the square shape are rather reduced (Japanese Patent Application Laid-Open No. 9-111383). An ingot having a fine crystal structure has a much smaller average crystal grain size than an ingot cast with a box mold. for that reason,
When each ingot is finely pulverized to an average fine powder particle size of 5 μm in the process of manufacturing a sintered magnet, the ingot having a fine crystal structure has a value close to the average crystal particle size and the average fine powder particle size. In addition, the finely pulverized particles are no longer single crystals, and the proportion of the polycrystalline finely pulverized particles increases. From this, it is considered that the degree of orientation during molding in a magnetic field also decreases, and as a result, the degree of orientation of the sintered magnet after heat treatment decreases, leading to a decrease in residual magnetic flux density and maximum energy product. ing. From the above, Sm ₂ Co
_{In the 17} series sintered magnet, the ingot cast by the strip casting method is not used as a raw material ingot.

The present invention solves the above problems, has excellent magnetic properties, and has a wide optimum temperature range for sintering and solution treatment. Therefore, heat treatment conditions can be relaxed and productivity can be improved. It is an object of the present invention to provide a rare earth sintered magnet and a method for manufacturing the same.

[0007]

Means for Solving the Problems and Embodiments of the Invention In order to achieve the above object, the present inventor studied the relationship between the alloy structure and the magnetic properties of the Sm ₂ Co ₁₇ based sintered magnet. 50% by volume or more of the constituent phase of the ₂ Co _17- based sintering ingot is used in a TbCu ₇ crystal structure (hereinafter, 1-7).
Phase)), superior magnetic properties can be obtained compared to a case where a sintered magnet is manufactured using a conventional cast ingot and a case where the other constituent phases are used as a main phase. Was issued. This means that the 1-7 phase in the Sm ₂ Co _17- based magnet alloy is replaced by another phase (2-17, 1-5, 2-
7,1-3 phase etc.), indicating that the orientation during molding in a magnetic field is better, and the higher the proportion of the 1-7 phase in the Sm ₂ Co _17- based magnet alloy, the better. Magnetic properties can be obtained. In addition, when 50% by volume or more of the constituent phases is occupied by the 1-7 phase, sintering and solution treatment are performed.
It was also found that the optimum temperature conditions for heat treatment and the like, which had to be strictly controlled, could be relaxed without causing crystal grain growth and phase change due to the heat treatment temperature due to the portions. In this case, it was also found that by setting the average crystal grain size in the alloy to 20 to 300 μm, more excellent magnetic properties can be provided.

Accordingly, the present invention provides a method for preparing R (where R is Sm or two or more rare earth elements containing 50% by weight or more of Sm) 2
0 to 30% by weight, Fe 10 to 45% by weight, Cu 1 to 10
Wt%, Zr 0.5-5 wt%, Ti 0.01-1.0
Sm ₂ C consisting of% by weight, balance Co and inevitable impurities
o ₁₇ type permanent magnet alloy, wherein the crystal structure in the alloy is T
(BH) max is at least 25 MGOe obtained by pulverizing, forming, sintering, solutionizing and further aging the alloy containing at least 50 volume% of a bCu ₇ type crystal structure. Rare earth sintered magnet and R (however,
R is Sm or two or more rare earth elements containing 50% by weight or more of Sm) 20 to 30% by weight, Fe 10 to 45% by weight, C
u1-10% by weight, Zr0.5-5% by weight, Ti0.0
An Sm ₂ Co _17- based permanent magnet alloy consisting of 1 to 1.0% by weight, the balance Co and inevitable impurities is 1100 ° C. to 125 ° C.
Heat treated at 0 ° C. for 0.5 to 20 hours to contain TbCu ₇ type crystal structure at 50% by volume or more in the crystal structure of the alloy, and pulverize, form, sinter, solutionize, and further age the alloy. To provide a method for producing an anisotropic rare earth sintered magnet having a (BH) max of 25 MGOe or more. In this case, the average crystal grain size in the alloy is preferably 20 to 300 μm.

According to the present invention, the magnetic properties of a sintered magnet due to problems such as coarsening of the structure in the central portion and segregation of the composition caused by the generation of equiaxed crystals, such as an ingot cast by a conventional box mold, are disclosed. To solve the deterioration,
Furthermore, the optimum temperature conditions, such as sintering and solution treatment, which had to be strictly controlled can be relaxed, and productivity can be improved. Further, the average crystal grain size is 20 to 3
By setting it to 00 μm, the fine powder becomes polycrystalline by pulverization, and the degree of orientation when molded in a magnetic field is reduced,
As a result, the degree of orientation of the sintered magnet after heat treatment is also low, and the residual magnetic flux density and the maximum energy product do not decrease,
An Sm ₂ Co ₁₇ sintered magnet having excellent magnetic properties can be manufactured.

Hereinafter, the present invention will be described in more detail.
The present invention provides an Sm ₂ Co _17- based sintered magnet casting alloy having fine crystals by performing an optimal heat treatment so that the alloy contains a TbCu _7- type crystal structure of 50% by volume or more of the constituent phase, This is a Sm-Co-based sintered magnet obtained by pulverizing a Sm ₂ Co _17- based magnet alloy, molding in a magnetic field, sintering, solutionizing, and then aging.

In the present invention, the composition of the Sm ₂ Co ₁₇ permanent magnet alloy is R (where R is Sm or 50% by weight of Sm).
Two or more rare earth elements including the above) 20 to 30% by weight, F
e 10 to 45% by weight, Cu 1 to 10% by weight, Zr 0.5
-5% by weight, 0.01-1.0% by weight of Ti, balance Co and unavoidable impurities. The rare earth metal other than Sm is not particularly limited, and Nd, Co,
Pr, Gd and the like can be mentioned. When the content of Sm in the rare earth element is less than 50% by weight, or when the amount of the rare earth element is less than 20% by weight or more than 30% by weight, it is impossible to have effective magnetic properties.

The Sm ₂ Co _17- based sintered magnet ingot of the present invention is obtained by melting a raw material having the above composition range in a non-oxidizing atmosphere by high frequency melting and casting. This casting
For example, it can be performed by a mold casting method, a strip casting method, a gas atomizing method, a melt spun method, or the like. In the present invention, the ingot is subjected to a heat treatment in a non-oxidizing atmosphere so that the alloy has 50% of the constituent phase.
Contains more than 1-7 phases by volume. 1-7 in the constituent phase
The phase is preferably at least 65% by volume, and if less than 50% by volume, the effects of the present invention cannot be obtained. The heat treatment temperature is
It is preferably 1100 ° C to 1250 ° C, and 1100 ° C
If it is less than 50% or more of the constituent phases in the ingot, 1-7
It is difficult to form a phase and it is not efficient because a long heat treatment is required. At temperatures above 1250 ° C,
The ingot reached its melting point, and the constituent phases of the ingot were 2-17 phase, 1-7 phase, 1-5 phase, 2-7 phase, 1 phase.
-3 phase etc., 50% of the constituent phases in the ingot
% Or more cannot be 1-7 phase.

The average crystal grain size of the above alloy is 20-3.
It is preferably set to 00 μm, more preferably 50 to 300 μm, and still more preferably 100 to 300 μm.

The heat treatment time is preferably 0.5 to 2 hours.
0 hours and less than 0.5 hours, the constituent phases vary, and if the heat treatment is performed for more than 20 hours, the alloy deteriorates due to the leak of the heat treatment furnace, and further, Sm in the ingot evaporates. Therefore, good magnetic characteristics cannot be obtained. In addition, ingots having no fine crystals have a long inter-phase distance, so that a phase change hardly occurs by heat treatment. Even if the heat treatment is performed for a long time or at a high temperature, it is difficult to reduce the 1-7 phase in the ingot to 50% by volume or more.

When the average crystal grain size is less than 20 μm, as described above, the average crystal grain size in the ingot and the fine grain size in the sintered magnet manufacturing process are close to each other. However, it becomes polycrystalline, disturbs the degree of orientation of the magnet, the residual magnetic flux density, the deterioration of the maximum energy product may be caused, and to obtain an average crystal grain size exceeding 300 μm,
Long-term or high-temperature heat treatment is required, which may adversely affect the magnetic properties of the sintered magnet due to deterioration of the alloy structure or loss of uniformity of the structure.

Next, the Sm ₂ Co ₁₇ sintered magnet alloy is coarsely pulverized, and has an average particle size of 1 to 10 μm, preferably about 5 μm.
Pulverize to μm. This coarse pulverization can be performed, for example, in an inert gas atmosphere by a jaw crusher, a brown mill, a pin mill, hydrogen storage, or the like. The pulverization can be performed by a wet ball mill using alcohol, hexane or the like as a solvent, a dry ball mill in an inert gas atmosphere, a jet mill by an inert gas stream, or the like.

Further, the finely pulverized powder is preferably
With a press machine in a magnetic field capable of applying a magnetic field of Oe or more, preferably 500 kg / cm ² or more and 2000
Compression molding with a pressure of less than kg / cm ² . continue,
The obtained compression-molded body is heated at 1100 ° C. to 1300 ° C. in a non-oxidizing atmosphere gas such as argon by a heat treatment furnace.
Preferably at 1150 ° C to 1250 ° C, 0.5 to
Sinter and solution for 5 hours, then quench after completion. Subsequently, 700 ° C to 900 ° C, preferably 750 ° C to 85 ° C
Aging treatment is performed at a temperature of 0 ° C. for 5 to 40 hours.

The anisotropic rare earth sintered magnet obtained as described above has a (BH) max of 25 MGOe or more, and gives good magnetic properties.

[0019]

EXAMPLES Next, the present invention will be described specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

[Example 1] Sm ₂ Co _17- based magnet alloy was composed of 25.5% by weight of Sm, 15.0% by weight of Fe,
u: 5.0% by weight, Zr: 2.5% by weight, Ti: 0.1
% By weight, with the balance being Co, melted in a high frequency melting furnace using an alumina crucible in an argon gas atmosphere, and strip cast (using a water-cooled single roll, 1.5 m / s Roll peripheral speed, cooling speed-
(2000 ° C./s). Next, the Sm-Co-based magnet alloy was subjected to a heat treatment at 1180 ° C. for 2 hours in an argon atmosphere using a heat treatment furnace. Sm ₂ Co ₁₇ obtained here
The system magnet alloy is identified for its constituent phases by X-ray diffraction (Cu-Kα), and the ratio of 1-7 phases in the constituent phases is measured. Further, the structure is observed with a polarizing microscope, and the average crystal grain size is measured. went. The ratio of the 1-7 phase is determined by comparing the peak intensity of the Th ₂ Zn ₁₇ type crystal structure obtained by X-ray diffraction with the TbC
It was determined by comparison of the peak intensities of u ₇ type crystal structure. Here, the average crystal grain size is a particle size when the volume is converted into a sphere (hereinafter, the average crystal grain size is obtained by this method).

Next, the Sm-Co magnet alloy was roughly pulverized to about 500 μm or less by a jaw crusher or a brown mill, and then finely pulverized to an average particle size of about 5 μm by a jet mill using a nitrogen stream. The obtained finely pulverized powder was 1.5 t / cm in a magnetic field of 15 kOe by a press machine in a magnetic field.
Molded at a pressure of ² . The obtained compact was sintered in an argon atmosphere at 1200 ° C. for 2 hours using a heat treatment furnace, and then subjected to a solution treatment at 1180 ° C. for 1 hour in an argon atmosphere. After the solution treatment, the mixture was rapidly cooled, and each of the obtained sintered bodies was kept in an argon atmosphere at 800 ° C. for 10 hours, and gradually cooled to 400 ° C. at a temperature lowering rate of −1.0 ° C./min. A sintered magnet was produced. The magnetic properties of the obtained sintered magnet were measured with a BH tracer.

Example 2 Thickness of Sm ₂ Co _17- based magnet alloy obtained by melting in a high-frequency melting furnace using an alumina crucible in an argon gas atmosphere so as to have the same composition as in Example 1. Was cast into a copper box mold so that the diameter was 3 mm. Next, the obtained Sm ₂ Co _17- based magnet alloy was subjected to a heat treatment in the same manner as in Example 1, and after completion, was rapidly cooled. The Sm ₂ Co _17- based magnet alloy obtained here was used in Example 1
Identification of constituent phases by X-ray diffraction (Cu-Kα)
And the ratio of 1-7 phase was measured, and further, the structure was observed with a polarizing microscope, and the average crystal grain size was measured.

The obtained Sm ₂ Co _17- based magnet alloy was subjected to coarse pulverization, fine pulverization, molding in a magnetic field, sintering, solution treatment, and then aging treatment in the same production method as in Example 1, A magnet was produced. Example 1 was obtained for the obtained sintered magnet.
The magnetic properties were measured in the same manner as described above.

Comparative Example 1 An alloy having the same composition as in Example 1 was produced by a similar casting method. However, heat treatment after casting was not performed. The obtained Sm ₂ Co _17- based magnet alloy was subjected to X-ray diffraction (Cu-Kα) in the same manner as in Example 1.
To identify the constituent phases, and to measure the ratio of the 1-7 phase. Further, the structure was observed with a polarizing microscope, and the average crystal grain size was measured.

The obtained Sm ₂ Co _17- based magnet alloy was subjected to coarse pulverization, fine pulverization, compaction in a magnetic field, sintering, solution treatment, and then aging treatment in the same production method as in Example 1. A magnet was produced. Example 1 was obtained for the obtained sintered magnet.
The magnetic properties were measured in the same manner as described above.

Comparative Example 2 Thickness of Sm ₂ Co _17- based magnet alloy obtained by melting in a high-frequency melting furnace using an alumina crucible in an argon gas atmosphere so as to have the same composition as in Example 1. Was cast to a copper box-type mold so that the diameter was 15 mm. However, heat treatment after casting was not performed. The Sm ₂ Co _17- based magnet alloy obtained here was used in Example 1
Identification of constituent phases by X-ray diffraction (Cu-Kα)
And the ratio of 1-7 phase was measured, and further, the structure was observed with a polarizing microscope, and the average crystal grain size was measured.

The obtained Sm ₂ Co _17- based magnet alloy was subjected to coarse pulverization, fine pulverization, compacting in a magnetic field, sintering, solution treatment, and then aging treatment in the same production method as in Example 1, followed by aging. A magnet was produced. Example 1 was obtained for the obtained sintered magnet.
The magnetic properties were measured in the same manner as described above.

Table 1 shows the proportions of the 1-7 phase in the alloys of Examples 1 and 2 and Comparative Examples 1 and 2, the average particle size of the alloys, and the magnetic properties of the obtained sintered magnets. From now on, one of the magnet alloys
Examples 1 and 2 having a large proportion of −7 phase are Comparative Examples 1 and 2.
It is clear that the residual magnetic flux density and the maximum energy product are excellent. In addition, the figure shows an X-ray diffraction image and a polarization image photograph of the above Examples and Comparative Examples.

[0029]

[Table 1]

[0030]

According to the present invention, the Sm ₂ Co ₁₇ based sintered magnet is
It has excellent magnetic properties and can be manufactured with a wider optimum temperature range of sintering and solution heat than conventional.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction image of a Sm ₂ Co _17- based magnet alloy in Example 1.

FIG. 2 is an X-ray diffraction image of a Sm ₂ Co _17- based magnet alloy in Example 2.

FIG. 3 is an X-ray diffraction image of a Sm ₂ Co _17- based magnet alloy in Comparative Example 1.

FIG. 4 is an X-ray diffraction image of a Sm ₂ Co _17- based magnet alloy in Comparative Example 2.

FIG. 5 is a polarization image photograph of a magnet material of Example 1 taken by a polarization microscope.

FIG. 6 is a polarization image photograph of a magnet material in Example 2 taken by a polarization microscope.

FIG. 7 is a polarization image photograph of a magnet material of Comparative Example 1 taken by a polarization microscope.

FIG. 8 is a polarization image photograph of a magnet material in Comparative Example 2 taken by a polarization microscope.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C22C 19/07 H01F 1/04 B (72) Inventor Koji Sato 2-1 Kitafu, Takefu-shi, Fukui 5 Shin-Etsu Chemical Co., Ltd. Magnetic Materials Research Laboratory (72) Inventor Takehisa Minowa 2-1-5 Kitafu, Takefu-shi, Fukui Prefecture Shin-Etsu Chemical Co., Ltd. Magnetic Materials Research Laboratory F-term (reference) 4K018 AA11 BA05 BB06 CA04 FA09 KA45 5E040 AA08 AA19 BD01 CA01 HB11 NN01 NN06 NN14 NN18 5E062 CD04 CG05

Claims (3)

[Claims] 1. 20 to 30% by weight of R (where R is Sm or two or more rare earth elements containing 50% by weight or more of Sm)
Fe10 to 45% by weight, Cu1 to 10% by weight, Zr0.
5-5% by weight, Ti 0.01-1.0% by weight, balance Co
Sm ₂ Co _17- based permanent magnet alloy comprising unavoidable impurities and containing at least 50% by volume of a TbCu ₇ type crystal structure in a crystal structure of the alloy, and pulverizing, molding, sintering, solutionizing, Further obtained by aging, (B
H) An anisotropic rare earth sintered magnet, wherein max is 25 MGOe or more. 2. An alloy having an average crystal grain size of 20 to 300 μm.
2. The anisotropic rare earth sintered magnet according to claim 1, wherein m is m. 3. 20 to 30% by weight of R (where R is Sm or two or more rare earth elements containing 50% by weight or more of Sm)
Fe10 to 45% by weight, Cu1 to 10% by weight, Zr0.
5-5% by weight, Ti 0.01-1.0% by weight, balance Co
And an Sm ₂ Co _17- based permanent magnet alloy comprising unavoidable impurities is heat-treated at 1100 ° C. to 1250 ° C. for 0.5 to 20 hours, and a TbCu _7- type crystal structure is added to the crystal structure of the alloy by 50%.
(BH) max is 2 characterized in that the alloy is pulverized, molded, sintered, solution-treated and further aged.
A method for producing an anisotropic rare earth sintered magnet of 5 MGOe or more.