WO2019182039A1

WO2019182039A1 - Rare earth magnet

Info

Publication number: WO2019182039A1
Application number: PCT/JP2019/011806
Authority: WO
Inventors: 英一郎福地; 将志伊藤
Original assignee: Tdk株式会社
Priority date: 2018-03-23
Filing date: 2019-03-20
Publication date: 2019-09-26
Also published as: JPWO2019182039A1; JP7140185B2

Abstract

[Problem] To obtain a rare earth magnet having, as a main phase, a compound that has an Nd₅Fe₁₇-type crystal structure, wherein the rare earth magnet has a high sintering density even when fired using a normal sintering method, and has characteristics such that the residual magnetic flux density Br and coercivity HcJ are high. [Solution] A rare earth magnet containing R, T, and M. R is one or more rare earth elements necessarily including Sm. T is standalone Fe, or Fe and Co. M is at least one element selected from the group consisting of Cu, Zn, Al, Ga, Ag, Au, Si, Ge, and Sn. The rare earth magnet comprises a main phase comprising crystal particles that have an Nd₅Fe₁₇-type crystal structure, and a sub phase that is a phase other than the main phase. At least a part of the sub phase contains M, and the average content ratio of M in the sub phase is 5-30 at%. The total area ratio of the sub phase on a discretionary cut surface of the rare earth magnet is 3-25%.

Description

Rare earth magnets

The present invention relates to a rare earth magnet.

Rare earth magnets are increasing in production year by year due to their high magnetic properties, and are used in various applications such as for various motors, various actuators, and MRI equipment.

For example, a magnet material having a main phase of Sm ₅ Fe ₁₇ intermetallic compound described in Patent Document 1 has a very high coercive force of 36.8 kOe at room temperature. Therefore, it is considered as a promising magnet material.

However, the control technology of the grain boundary phase has not been established for the magnet material whose main phase is Sm ₅ Fe ₁₇ intermetallic compound. The magnet utilizing the coercive force high magnetic material the main phase of the Sm ₅ Fe ₁₇ intermetallic compounds has not yet been realized.

Non-Patent Document 1 reports a sintered magnet using a discharge plasma sintering method (SPS method). In the SPS method, the sintering is performed at a lower temperature than in a normal sintering method. Moreover, pressurization is required at the time of sintering. However, the sintered magnet described in Non-Patent Document 1 has a low density as a sintered body. Moreover, a soft magnetic phase exists as a subphase. Further, in general, when the SPS method is used, the magnetic properties are deteriorated as compared with the case of using a normal sintering method. As described above, the sintered magnet described in Non-Patent Document 1 does not have the magnetic characteristics as expected in the stage before sintering. Furthermore, the SPS method itself is a sintering method that is relatively unsuitable for mass production.

JP 2008-13396 A

The present invention has been made in view of such a situation, and is a rare earth magnet having a Nd ₅ Fe ₁₇ type crystal structure compound as a main phase, and has a high sintering density even when fired by a normal sintering method. Another object of the present invention is to obtain a rare earth magnet having high residual magnetic flux density Br and coercive force HcJ.

The present invention is a rare earth magnet containing R, T and M,
R is one or more rare earth elements essential for Sm, T is Fe alone or Fe and Co, M is at least selected from the group consisting of Cu, Zn, Al, Ga, Ag, Au, Si, Ge and Sn One kind,
A main phase composed of crystal grains having an Nd ₅ Fe ₁₇ type crystal structure, and a subphase which is a phase other than the main phase,
At least a portion of the subphase comprises M;
The average content ratio of M in the subphase is 5 at% or more and 30 at% or less,
The total area ratio of the subphase at an arbitrary cut surface of the rare earth magnet is 3% or more and 25% or less.

Since the rare earth magnet of the present invention has the above-mentioned characteristics, a high sintering density can be obtained even with a normal sintering method. Further, the residual magnetic flux density Br and the coercive force HcJ are also increased. That is, the magnetic characteristics are improved.

The rare earth magnet of the present invention may further contain C, and the content ratio of C to the whole rare earth magnet may be more than 0 at% and not more than 15 at%.

The rare earth magnet of the present invention may further contain Pr and / or Nd as R,
The content ratio of Sm with respect to the entire R may be 50 at% or more and 99 at% or less, and the total content ratio of Pr and Nd may be 1 at% or more and 50 at% or less.

6 is a reflected electron image of Example 3.

DETAILED DESCRIPTION A mode (embodiment) for carrying out the present invention will be described in detail. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined.

The rare-earth magnet 1 according to the present embodiment uses, as the main phase 11, crystal grains having an Nd ₅ Fe ₁₇ type crystal structure (space group P6 ₃ / mcm). A phase other than the main phase 11 is defined as a subphase 13. In the following description, a phase composed of crystal grains having an Nd ₅ Fe ₁₇ type crystal structure is referred to as an R ₅ T ₁₇ crystal phase.

The structure of the subphase 13 is arbitrary. For example, an RT crystal phase other than the R ₅ T ₁₇ crystal phase may be included. Examples of the RT crystal phase include an RT ₂ crystal phase, an RT ₃ crystal phase, an R ₂ T ₇ crystal phase, an RT ₅ crystal phase, an RT ₇ crystal phase, an R ₂ T ₁₇ crystal phase, and an RT ₁₂ crystal phase. Can be mentioned. The subphase 13 may include an amorphous phase. However, it is preferable that the RT crystal phase having a soft magnetism or a low coercive force such as the R ₂ T ₁₇ crystal phase and the RT ₃ crystal phase is small. In addition, what kind of crystals the rare earth magnet 1 according to the present embodiment includes may be confirmed using an X-ray diffraction method (XRD), a scanning electron microscope (SEM) with an elemental analysis function, or the like. it can.

Here, when the rare earth magnet 1 according to the present embodiment contains M, a compound containing R and M in the subphase 13 is generated. Hereinafter, a phase composed of a compound containing R and M is referred to as an RM phase. The RM phase may further contain T. The content ratio of R in the RM phase is not particularly limited, but is, for example, 24 at% or more. A compound containing R and M constituting the RM phase has a low melting point and is likely to become a grain boundary phase by sintering. In other words, M diffuses into the grain boundary phase, resulting in a compound containing R and M. In addition, the grain boundary phase in this embodiment is a subphase existing between crystal grains of a plurality of R ₅ T ₁₇ crystal phases.

When the RM phase is generated, an RT crystal phase other than the R ₅ T ₁₇ crystal phase, such as the R ₂ T ₁₇ crystal phase and the RT ₃ crystal phase, is hardly precipitated. And it becomes easy to form a uniform grain boundary phase.

As a result, it becomes possible to sinter at a higher temperature than before, and the rare earth magnet 1 having a sufficient sintering density can be obtained without pressing. Furthermore, the residual magnetic flux density Br and the coercive force HcJ of the rare earth magnet 1 obtained by having a sufficient sintered density can be improved.

The method for distinguishing the main phase 11 and the subphase 13 in the rare earth magnet 1 is not particularly limited. For example, a reflected electron image can be obtained using an SEM, and can be visually distinguished from the difference in contrast in each phase. . A specific example of the reflected electron image is shown in FIG. FIG. 1 shows a backscattered electron image obtained using SEM after a cut surface of a sample of Example 3 described later is mirror-finished by ion milling.

It is also preferable to use an SEM (so-called SEM-EDS) with an energy dispersive X-ray spectrometer (EDS). Elemental mapping is performed using EDS, and it can be determined that the phase in which the ratio of R and T, which will be described later, is approximately 5:17, is the main phase 11, and the other phases excluding vacancies are the subphases 13. By combining the reflected electron image and the element mapping image, the main phase 11 and the subphase 13 can be more accurately distinguished. Furthermore, by using together an energy dispersive X-ray spectroscopy (TEM-EDS) using a transmission electron microscope (TEM) and an electron diffraction method, it is possible to distinguish a crystal structure and an amorphous phase in a minute region.

In the rare earth magnet 1 according to the present embodiment, at least a part of the subphase 13 contains M, the average content of M in the subphase 13 is 5 at% or more and 30 at% or less, and The total area ratio is 3% or more and 25% or less.

The average content ratio of M is calculated by measuring the M content ratio in all the subphases 13 in the measurement range using SEM-EDS in a measurement range of 50 μm × 50 μm or more and averaging. In addition, about a measurement range, you may make it become a measurement range of a magnitude | size of 50 micrometers x 50 micrometers or more independently, and you may make it the sum total of several measurement ranges become a magnitude | size of 50 micrometers x 50 micrometers or more.

By setting the average content ratio of M in the subphase 13 to 5 at% or more and 30 at% or less, the rare earth magnet 1 is easily densified and the density is easily increased. Then, the generation of an RT crystal phase other than the R ₅ T ₁₇ crystal phase, such as the R ₂ T ₁₇ crystal phase and the RT ₃ phase, is suppressed. As a result, the residual magnetic flux density Br and the coercive force HcJ are easily improved.

When the average content ratio of M in the subphase 13 is too small, the rare earth magnet 1 is difficult to be densified and the sintered density is likely to be lowered. In addition, the generation of an RT crystal phase other than the R ₅ T ₁₇ crystal phase, such as the R ₂ T ₁₇ crystal phase and the RT ₃ crystal phase, is not sufficiently suppressed. As a result, the composition of the grain boundary phase tends to be non-uniform. Furthermore, the residual magnetic flux density Br and the coercive force HcJ are likely to decrease. When the average content ratio of M in the subphase 13 is too large, the rare earth magnet 1 is difficult to be densified and the sintered density is likely to be lowered. Further, since the distribution of M in the grain boundary phase becomes non-uniform, the residual magnetic flux density Br and the coercive force HcJ are likely to decrease.

The total area ratio of the sub-phase 13 is calculated by calculating the total area of all the sub-phases 13 in the measurement range using SEM-EDS in the measurement range of 50 μm × 50 μm or larger and dividing by the area of the measurement range. To do. In addition, about a measurement range, you may make it become a measurement range of a magnitude | size of 50 micrometers x 50 micrometers or more independently, and you may make it the sum total of several measurement ranges become a magnitude | size of 50 micrometers x 50 micrometers or more.

By setting the total area ratio of the subphase 13 to 3% or more and 25% or less, the rare earth magnet 1 is easily densified and the density is easily increased. Then, the generation of an RT crystal phase other than the R ₅ T ₁₇ crystal phase, such as the R ₂ T ₁₇ crystal phase and the RT ₃ crystal phase, is suppressed. As a result, the residual magnetic flux density Br and the coercive force HcJ are easily improved.

When the total area ratio of the subphase 13 is too small, the rare earth magnet 1 is difficult to be densified and the sintered density is likely to be lowered. In addition, generation of an RT phase other than the R ₅ T ₁₇ crystal phase such as the R ₂ T ₁₇ crystal phase and the RT ₃ phase is not sufficiently suppressed. As a result, the composition of the grain boundary phase tends to be non-uniform. Furthermore, the residual magnetic flux density Br and the coercive force HcJ are likely to decrease. When the total area ratio of the subphase 13 is too large, the total area ratio of the main phase 11 in the rare earth magnet 1 becomes too small. As a result, the residual magnetic flux density Br tends to decrease.

The rare earth magnet 1 according to the present embodiment is a rare earth magnet including R, T, and M. R is one or more rare earth elements that require Sm, T is Fe alone, or Fe and Co, and M is selected from the group consisting of Cu, Zn, Al, Ga, Ag, Au, Si, Ge, and Sn. At least one. M may be at least one selected from the group consisting of Cu, Zn, Al, Ga, Ag, and Au.

Although the content ratio of R in the rare earth magnet 1 is arbitrary, it may be 15 at% or more and 35 at% or less, and is preferably 24.2 at% or more and 30.6 at% or less. If the R content is too small or too large, the R ₅ T ₁₇ crystal phase is not sufficiently formed.

The content ratio of T in the rare earth magnet 1 is arbitrary. Further, the content ratio of Co with respect to the entire T is arbitrary, but may be 0 at% or more and 20 at% or less. The smaller the Co content, the higher the coercive force. Moreover, it exists in the tendency for it to become high magnetic flux density, so that the content rate of Co is large.

The content ratio of M in the rare earth magnet 1 is arbitrary, but may be 0.2 at% or more and 10 at% or less, and preferably 0.3 at% or more and 4.2 at%. When the content ratio of M in the rare earth magnet 1 is too small, a compound containing R and M (RM phase) in the subphase 13 is not sufficiently formed. And the average content rate of M in the subphase 13 mentioned later becomes small too much. When the content ratio of M is too large, the average content ratio of M in the subphase 13 becomes too large. Or the total area ratio of the subphase 13 becomes too large.

Further, the rare earth magnet 1 according to the present embodiment may further contain C. And it is preferable that the content rate of C with respect to the whole rare earth magnet 1 is more than 0 at% and 15 at% or less, and it is further more preferable that they are 1.0 at% or more and 7.5 at% or less.

The rare earth magnet 1 according to the present embodiment tends to improve the coercive force HcJ by containing C. The reason why the coercive force HcJ is improved is unknown, but the present inventors believe that when the rare earth magnet 1 contains C, a compound containing R and C is easily formed in the grain boundary phase of the subphase 13. . Hereinafter, a phase composed of a compound containing R and C is referred to as an RC rich phase. The RC rich phase may contain M and / or T. The inventors consider that the coercive force HcJ of the rare earth magnet 1 is improved because the RC rich phase is a nonmagnetic phase and has a high magnetic separation effect.

In the rare earth magnet 1 according to the present embodiment, it is preferable that the ratio of Sm in R is larger, and the content ratio of Sm with respect to the entire R in the entire rare earth magnet is preferably 50 at% or more.

Further, when one or more of Pr or Nd is contained as R, the effective magnetic moment of Pr or Nd is larger than Sm, so that the residual magnetic flux density tends to be improved. Furthermore, in the case of containing Pr or Nd is the effect of suppressing the generation of the low-coercivity components such as R ₂ T ₁₇ crystal phase and RT ₃ crystal phase can be obtained in the subphase 13. However, if the total content of Pr and Nd in R is too large, the coercive force HcJ tends to decrease.

Therefore, the content ratio of Sm with respect to the entire R is preferably 50 at% or more and 99 at% or less, and the total content ratio of Pr and Nd is preferably 1 at% or more and 50 at% or less. Further, R may contain rare earth elements other than Sm, Pr, and Nd within a range that does not greatly affect the magnetic properties. The content of rare earth elements other than Sm, Pr and Nd is, for example, 5 at% or less with respect to the entire R.

The rare earth magnet 1 according to the present embodiment may contain elements other than the elements described above. For example, elements such as Bi, Ti, V, Cr, Mn, Zr, Nd, Mo, and Mg can be appropriately contained. Moreover, you may contain the impurity originating in a raw material. The content of elements other than the above-described elements is arbitrary, but is, for example, 3% or less with respect to the entire rare earth magnet 1.

Note that ICP mass spectrometry is used for analysis of the composition ratio of the entire rare earth magnet 1 according to the present embodiment. Further, if necessary, a combustion in oxygen stream-infrared absorption method may be used in combination.

Hereinafter, a preferred example of the method for manufacturing the rare earth magnet 1 according to the present embodiment will be described.

The rare earth magnet 1 can be manufactured by appropriately combining a casting method, a strip casting method, a super rapid solidification method, a vapor deposition method, a HDDR method, a sintering method, a hot working method, and the like. An example of a manufacturing method using the method will be described.

Specific examples of the ultra rapid solidification method include a single roll method, a twin roll method, a centrifugal quench method, and a gas atomization method, but it is preferable to use a single roll method. In the single roll method, the molten alloy is discharged from a nozzle and collided with the peripheral surface of the cooling roll, whereby the molten alloy is rapidly cooled to obtain a ribbon-like or flaky quenched alloy. The single roll method has higher mass productivity and better reproducibility of the rapid cooling conditions than other ultra rapid solidification methods.

First, an alloy ingot having a desired composition ratio is prepared as a raw material. The raw material alloy can be produced by dissolving a raw material metal containing R, T, M and the like in an inert gas, preferably an Ar atmosphere, by a melting method such as arc melting. When it is desired to appropriately contain C or other elements, they can be contained in the same manner.

A quenched ribbon is produced from the alloy ingot produced by the above method by the ultra rapid solidification method. As the ultra-rapid solidification method, for example, the above-mentioned alloy ingot is cut into small pieces by a stamp mill or the like to obtain small pieces, and the obtained small pieces are melted at a high frequency in an Ar atmosphere to obtain a molten metal. It is possible to use a melt spin method that discharges onto a rotating cooling roll and rapidly solidifies. The melt rapidly cooled by the cooling roll becomes a rapidly cooled ribbon that is rapidly solidified into a thin strip.

In addition, the method of fragmenting is not limited to the stamp mill. The atmosphere during high frequency melting is not limited to the Ar atmosphere. The rotation speed of the cooling roll is arbitrary. For example, it is good also as 10 m / s or more and 100 m / s or less. The material of the cooling roll is arbitrary. For example, a copper roll may be used as the cooling roll.

Next, the obtained quenched ribbon is pulverized to obtain a fine powder having a particle size of about several μm. The pulverization may be performed in two stages of coarse pulverization and fine pulverization, or may be performed in one stage of only fine pulverization.

Next, the obtained fine powder is molded into a predetermined shape to obtain a molded body. The pressure at the time of molding is arbitrary. For example, it is 10 MPa or more and 1000 MPa or less.

Next, the rare earth magnet 1 can be obtained by sintering the obtained compact and simultaneously performing crystallization. Sintering is performed by a normal sintering method. The normal sintering method is a sintering method in which no pressure is applied during sintering, and generally requires a higher sintering temperature than the SPS method or the like. The rare earth magnet 1 according to the present embodiment can be sintered without pressure and at a sintering temperature lower than that of the prior art because a part of the different phases becomes a low melting point liquid phase component during sintering. . Specifically, the sintering temperature (crystallization temperature) can be 500 ° C. or higher. Moreover, 750 degrees C or less may be sufficient. The atmosphere during sintering is arbitrary. For example, an Ar atmosphere can be used. The sintering time (crystallization time) is arbitrary. For example, it can be 10 minutes or more and 10 hours or less. The cooling rate after sintering is arbitrary. For example, it can be set to 0.01 ° C./s or more and 30 ° C./s or less.

Further, in order to improve the distribution of M in the heterogeneous phase of the rare earth magnet 1 and form a uniform grain boundary phase, heat treatment after the sintering process is effective. This heat treatment is performed by raising the temperature to a heat treatment temperature of 500 ° C. or more and 650 ° C. or less at a rate of 10 ° C./s or more and 30 ° C./s or less and then keeping the heat treatment temperature for 10 minutes or more and 300 minutes or less. Usually, these treatments are performed in an Ar atmosphere.

In addition, when using the one alloy method, the quenched ribbon containing R, T and M may be crystallized before pulverization. The crystallization treatment conditions in this case are arbitrary. For example, the crystallization temperature can be 500 ° C. to 700 ° C., the crystallization time can be 1 minute to 50 hours, and the cooling rate after crystallization can be 0.01 ° C./s to 30 ° C./s.

In addition, if the alloy composed of R and T is a single domain particle of the R ₅ T ₁₇ crystal phase by performing the above crystallization treatment, an anisotropic magnet is formed by performing molding in a magnetic field. Is also possible.

As mentioned above, although the example of the manufacturing method of the rare earth magnet 1 which concerns on this embodiment was demonstrated, the manufacturing method of the rare earth magnet 1 is arbitrary.

For example, in the above manufacturing method, the one alloy method using one kind of quenched ribbon is used, but the two alloy method using two kinds of quenched ribbon may be used. Three or more types of quenched ribbons may be used.

Specifically, for example, a quenched ribbon made of R and T and a quenched ribbon made of R and M are prepared. And it can mix during the grinding | pulverization of each quenching ribbon, or after grinding | pulverization. In the case of the two-alloy method, the quenched ribbon made of R and T mainly becomes the main phase 11, and the quenched ribbon made of R and M mainly becomes the subphase 13. T may be contained in the quenched ribbon made of R and M which mainly becomes the subphase 13, and the quenched ribbon made of R, T and M may be used. Two or more types of quenched ribbons having different contents of R, T and M may be used. In this case, not all the quenched ribbons need to contain all of R, T, and M. All the quenching ribbons may contain one or more selected from R, T and M. And the total area ratio of the subphase 13 etc. can be controlled also by controlling the mixing ratio of each quenching ribbon. If the amount is small, a powder made of a single metal may be used instead of the quenched ribbon.

In the case of using the two-alloy method, only the quenched ribbon made of R and T may be crystallized before pulverization. In particular, the R ₅ T ₁₇ crystal phase can be stably generated by crystallizing a quenched ribbon whose R: T is close to 5:17. The crystallization treatment conditions in this case are arbitrary. For example, the crystallization temperature can be 500 ° C. to 700 ° C., the crystallization time can be 1 minute to 50 hours, and the cooling rate after crystallization can be 0.01 ° C./s to 30 ° C./s. When two or more types of quenching ribbons made of R and T are used, only the quenching ribbons with R: T close to 5:17 may be crystallized.

Hereinafter, the content of the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to the following examples.

(Experimental example 1)
First, a raw material made of a simple substance or an alloy of Sm, Pr, Nd, Fe, Cu, Zn, Al, Ga, Ag, Au, Si, Ge, Sn and / or C was prepared. Each raw material was blended so that the resulting magnet had the composition shown in Table 1 below, and an alloy ingot was produced by arc melting in an Ar atmosphere. Next, the alloy ingot was cut into small pieces using a stamp mill to obtain small pieces. Next, the small piece was melted at high frequency in an Ar atmosphere of 50 kPa to obtain a molten metal. Next, a quenched ribbon was obtained from the molten metal by a single roll method. Specifically, the molten metal was discharged to a cooling roll (copper roll) rotated at a peripheral speed of 50 m / s to obtain a quenched ribbon. Next, the quenched ribbon was coarsely and finely pulverized to obtain a fine powder having an average particle size of about 5 μm. Coarse pulverization was performed with a stamp mill, and fine pulverization was performed with a jet mill. Next, after forming the fine powder into a rectangular parallelepiped shape of 10 mm × 15 mm × 12 mm at 100 MPa with no magnetic field, the crystal is crystallized at a heating rate of 5 ° C./min, a sintering holding temperature of 700 ° C. or 725 ° C., and a sintering holding time of 1 hour. After crystallization and sintering, it was rapidly cooled to room temperature. The sample after cooling was subjected to heat treatment at a heating rate of 20 ° C./s, a heat treatment temperature of 550 ° C., and a heat treatment holding time of 30 minutes to obtain a rare earth magnet. Further, it was confirmed that the composition of the obtained sintered body was the composition shown in Table 1 by using ICP mass spectrometry and, if necessary, combustion in an oxygen stream-infrared absorption method. Specifically, the combustion in oxygen stream-infrared absorption method was used to measure the amount of C.

Next, the main phase and subphase of each obtained sample were distinguished, and the composition of each phase was analyzed. Specifically, a cross section obtained by cutting each obtained sample was mirror-finished by ion milling, and a reflected electron image was observed using a scanning electron microscope (SEM). The SEM was equipped with an energy dispersive X-ray spectrometer (EDS). It can be generally judged from the contrast of the reflected electron image whether each region is a main phase or a sub-phase. Next, an observation region of 50 μm × 50 μm including the main phase and subphase was determined from the backscattered electron image, and elemental mapping was performed using EDS. From the elemental mapping data, the phase in which the ratio of R and T was approximately 5:17 was determined as the main phase, and the other region excluding the vacancies was determined as the subphase. Finally, the main phase and the subphase were identified by using the contrast of the reflected electron image and the data of element mapping. Next, the average composition of the subphase was specified from the elemental mapping data of the subphase portion, and the average content ratio (at%) of M in the subphase was specified. Further, the total area ratio (%) of the subphase was determined from 100 × (total area of subphase) / (area of observation region−area of vacancy). The above operation was performed on four 50 μm × 50 μm observation regions, and the average value was defined as the average content ratio of M in the subphase in each sample and the total area ratio of the subphase.

Moreover, it confirmed using XRD that all the Examples and Comparative Examples had a Nd ₅ Fe ₁₇ type crystal structure. Then, it was confirmed that all the samples of Examples and Comparative Examples had the compositions shown in Table 1 by using ICP mass spectrometry and, if necessary, combustion in an oxygen stream-infrared absorption method.

The magnetic characteristics of the sample were measured using a pulse excitation type BH curve tracer. In this embodiment, the case where the residual magnetic flux density Br is 3.5 kG is considered good. Moreover, the case where the coercive force HcJ was 30 kOe or more was considered good.

The relative density (%) of the sample was obtained by 100 × (dimensional density obtained by actually measuring the size and mass of each sample) / (theoretical density of Sm ₅ Fe ₁₇ crystal phase). In this experimental example, the theoretical density of the Sm ₅ Fe ₁₇ crystal phase was set to 7.922 g / cm ³ , which is a literature value. When the relative density of the sample was 80% or more, the sintering density was considered good.

From Table 1, each of the examples in which the total area ratio of the subphase is 3 to 25% and the average content ratio of M in the subphase is 5 to 30 at% has a high relative density and excellent magnetic characteristics. On the other hand, Comparative Example 1 which did not contain M and had a low total area ratio of the subphase had a low relative density and a reduced magnetic property.

(Experimental example 2)
In Experimental Example 2, unlike in Experimental Example 1 in which one kind of quenched ribbon was produced, two types of quenched ribbons having the compositions shown in Table 2 below were produced. Specifically, a quenched ribbon 1 containing R and T and a quenched ribbon 2 containing R and M were prepared. The manufacturing method up to the preparation of the quenched ribbon is the same as in Experimental Example 1.

Next, the quenching ribbon 1 was subjected to crystallization treatment. Specifically, it was heated to 650 ° C. in an Ar atmosphere at a heating rate of 20 ° C./min, held at 650 ° C. for 30 hours, and then rapidly cooled to room temperature.

Next, each quenched ribbon was coarsely pulverized using a stamp mill to obtain a coarse powder of each quenched ribbon. Then, using a jet mill, each coarse powder was finely pulverized while being mixed at an alloy mixing ratio (weight ratio) shown in Table 2 below to obtain a fine powder.

Thereafter, magnets of each sample were obtained in the same manner as in Experimental Example 1 and evaluated in the same manner as in Experimental Example 1. The results are shown in Table 2. Further, it was confirmed by ICP mass spectrometry that the composition of the obtained sintered body was the composition shown in Table 2.

From Table 2, each example in which the total area ratio of the subphase was 3 to 25% and the average content ratio of M in the subphase was 5 to 30 at% was high in relative density and excellent in magnetic characteristics. On the other hand, in Comparative Example 2 in which the average content ratio of M in the subphase was too small, the relative density decreased and the residual magnetic flux density Br decreased. In Comparative Example 3 in which the average content ratio of M in the subphase was too large, the residual magnetic flux density Br and the coercive force HcJ were reduced. In Comparative Example 4 in which the total area ratio of the subphases was too large, the residual magnetic flux density Br decreased.

(Experimental example 3)
In Examples 23 and 24 of Experimental Example 3, three types of quenched ribbons having the compositions shown in Table 3 below were produced. Specifically, a quenched ribbon 1 containing R and T, a quenched ribbon 2 containing R and T but having a composition different from that of the quenched ribbon 1, and a quenched ribbon containing M and R or T 3 and made. The manufacturing method up to the preparation of the quenched ribbon is the same as in Experimental Example 1. In Example 25 of Experimental Example 3, the quenched ribbon 1 and the quenched ribbon 2 are the same as in Examples 23 and 24, but the quenched ribbon 3 was not used, but instead a fine powder of Zn alone was used. .

Next, each quenched ribbon was coarsely pulverized using a stamp mill to obtain a coarse powder of each quenched ribbon. Then, using a jet mill, each coarse powder (each coarse powder and Zn simple powder in Example 25) is mixed at an alloy mixing ratio (weight ratio) shown in Table 3 below, and finely pulverized. Got.

Thereafter, magnets of each sample were obtained in the same manner as in Experimental Example 1 and evaluated in the same manner as in Experimental Example 1. The results are shown in Table 3. Moreover, it was confirmed by ICP mass spectrometry that the composition of the obtained sintered body was the composition shown in Table 3.

From Table 3, each example in which the total area ratio of the subphase was 3 to 25% and the average content ratio of M in the subphase was 5 to 30 at% was high in relative density and excellent in magnetic characteristics.

DESCRIPTION OF SYMBOLS 1 ... Rare earth magnet 11 ... Main phase 13 ... Subphase

Claims

A rare earth magnet comprising R, T and M,
R is one or more rare earth elements essential for Sm, T is Fe alone or Fe and Co, M is at least selected from the group consisting of Cu, Zn, Al, Ga, Ag, Au, Si, Ge and Sn One kind,
A main phase composed of crystal grains having an Nd 5 Fe 17 type crystal structure, and a subphase which is a phase other than the main phase,
At least a portion of the subphase comprises M;
The average content ratio of M in the subphase is 5 at% or more and 30 at% or less,
A rare earth magnet, wherein a total area ratio of the subphases in an arbitrary cut surface of the rare earth magnet is 3% or more and 25% or less.
The rare earth magnet according to claim 1, further comprising C, wherein a content ratio of C to the whole rare earth magnet is more than 0 at% and not more than 15 at%.
R further includes Pr and / or Nd,
The rare earth magnet according to claim 1 or 2, wherein the content ratio of Sm with respect to the whole R is 50 at% or more and 99 at% or less, and the total content ratio of Pr and Nd is 1 at% or more and 50 at% or less.