JP7140185B2 - rare earth magnet - Google Patents

Description

The present invention relates to rare earth magnets.

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

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

However, a technique for controlling the grain boundary phase has not been established for a magnetic material having a Sm ₅ Fe ₁₇ intermetallic compound as a main phase. A magnet that makes use of the high coercive force of a magnetic material having a Sm ₅ Fe ₁₇ intermetallic compound as a main phase has not yet been realized.

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

JP-A-2008-133496

Materials Science and Engineering 1 (2009) 012032

The present invention has been made in recognition of such circumstances, and is a rare earth magnet having a compound having a Nd ₅ Fe ₁₇ type crystal structure as a main phase, which has a high sintered density even when fired by a normal sintering method. An object of the present invention is to obtain a rare earth magnet having high remanence Br and high coercive force HcJ.

The present invention is a rare earth magnet comprising R, T and M,
R is one or more rare earth elements essentially including 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 is one type,
Consists of a main phase composed of crystal grains having a Nd ₅ Fe ₁₇ -type crystal structure, and a subphase that is a phase other than the main phase,
at least a portion of said subphase comprises M;
The average content of M in the subphase is 5 at% or more and 30 at% or less,
It is characterized in that the total area ratio of the subphases on any 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 characteristics, a high sintered density can be obtained even by a normal sintering method. Also, the residual magnetic flux density Br and the coercive force HcJ are increased. That is, the magnetic properties are improved.

The rare earth magnet of the present invention may further contain C, and the content of C relative to the entire rare earth magnet may be more than 0 at % and 15 at % or less.

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

4 is a backscattered electron image of Example 3. FIG.

A form (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. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the components described below can be combined as appropriate.

The rare earth magnet 1 according to this embodiment has a main phase 11 of crystal grains having a Nd ₅ Fe ₁₇ -type crystal structure (space group P6 ₃ /mcm). Phases other than the main phase 11 are referred to as subphases 13 . In the following description, the phase consisting of crystal grains having the Nd ₅ Fe ₁₇ -type crystal structure is referred to as the R ₅ T ₁₇ crystal phase.

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

Here, by including M in the rare earth magnet 1 according to the present embodiment, a compound including R and M is generated in the subphase 13 . A phase composed of a compound containing R and M is hereinafter referred to as an RM phase. Note that the RM phase may further contain T. Although there is no particular limitation on the content of R in the RM phase, it is, for example, 24 atomic % or more. A compound containing R and M that constitutes the RM phase has a low melting point and tends to form a grain boundary phase upon sintering. In other words, M diffuses into the grain boundary phase to produce a compound containing R and M. In addition, the grain boundary phase in the present embodiment means a subphase existing between crystal grains of a plurality of R ₅ T ₁₇ crystal phases.

The formation of the RM phase makes it difficult to precipitate RT crystal phases other than the R ₅ T ₁₇ crystal phase, such as the R ₂ T ₁₇ crystal phase and the RT ₃ crystal phase. And it becomes easy to form a uniform grain boundary phase.

As a result, sintering can be performed at a higher temperature than before, and a rare earth magnet 1 having a sufficient sintered density can be obtained without pressurization. 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 of distinguishing the main phase 11 and the subphase 13 in the rare earth magnet 1 is not particularly limited, but for example, a backscattered electron image is obtained using an SEM, and the differences in contrast between the phases can be visually distinguished. . A specific example of a backscattered electron image is shown in FIG. FIG. 1 is a backscattered electron image obtained using an SEM after a cut surface of a sample of Example 3, which will be described later, was mirror-finished by ion milling.

Also, it is preferable to use an SEM with an energy dispersive X-ray spectrometer (EDS) (so-called SEM-EDS). Elemental mapping is performed using EDS, and it can be determined that the main phase 11 is the phase in which the ratio of R and T, which will be described later, is about 5:17, and the subphase 13 is the phase other than vacancies. By combining the backscattered electron image and the elemental mapping image, the main phase 11 and the subphase 13 can be distinguished more accurately. Furthermore, by combining energy dispersive X-ray spectroscopy (TEM-EDS) using a transmission electron microscope (TEM) and electron diffraction, it is possible to distinguish between crystal structures and amorphous phases in minute regions.

In the rare earth magnet 1 according to the present embodiment, at least 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 subphase 13 in an arbitrary cross section The total area ratio is 3% or more and 25% or less.

The average content of M is calculated by measuring and averaging the content of M in all subphases 13 within a measurement range of 50 μm×50 μm or more using SEM-EDS. The measurement range may be set to a size of 50 μm×50 μm or more independently, or the total size of a plurality of measurement ranges may be set to a size of 50 μm×50 μm 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 tends to be densified and its density tends to increase. In addition, the formation of RT crystal phases 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 likely to be improved.

If the average content of M in the subphase 13 is too small, the rare earth magnet 1 is difficult to densify, and the sintered density tends to decrease. In addition, the formation of RT crystal phases 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 uneven. Furthermore, the residual magnetic flux density Br and the coercive force HcJ tend to decrease. If the average content of M in the subphase 13 is too large, the rare earth magnet 1 is difficult to densify, and the sintered density tends to decrease. Moreover, since the distribution of M in the grain boundary phase becomes uneven, the residual magnetic flux density Br and the coercive force HcJ tend to decrease.

The total area ratio of the subphases 13 is calculated by calculating the total area of all the subphases 13 within the measurement range using SEM-EDS in a measurement range of 50 μm×50 μm or more and dividing by the area of the measurement range. do. The measurement range may be set to a size of 50 μm×50 μm or more independently, or the total size of a plurality of measurement ranges may be set to a size of 50 μm×50 μm 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 can be easily densified and its density can be easily increased. In addition, the formation of RT crystal phases 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 likely to be improved.

If the total area ratio of the subphase 13 is too small, the rare earth magnet 1 is difficult to densify, and the sintered density tends to decrease. In addition, the formation of RT phases 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 uneven. Furthermore, the residual magnetic flux density Br and the coercive force HcJ tend to decrease. If the total area ratio of the secondary phase 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 this embodiment is a rare earth magnet containing R, T and M. R is one or more rare earth elements essentially including Sm, T is Fe alone or Fe and Co, 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.

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

The content ratio of T in the rare earth magnet 1 is arbitrary. Moreover, although the content ratio of Co to the entire T is arbitrary, it may be 0 at % or more and 20 at % or less. There is a tendency that the smaller the content of Co, the higher the coercive force. Also, the higher the Co content, the higher the magnetic flux density tends to be.

The content 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 %. If the content of M in the rare earth magnet 1 is too small, it becomes difficult to sufficiently form a compound containing R and M in the subphase 13 (RM phase). Then, the average content of M in the subphase 13, which will be described later, becomes too small. If the content of M is too high, the average content of M in the subphase 13 will be too high. Alternatively, the total area ratio of the subphase 13 becomes too large.

In addition, the rare earth magnet 1 according to this embodiment may further contain C. The content of C in the entire rare earth magnet 1 is preferably more than 0 at % and 15 at % or less, more preferably 1.0 at % or more and 7.5 at % or less.

The coercive force HcJ tends to be improved by including C in the rare earth magnet 1 according to the present embodiment. The reason why the coercive force HcJ is improved is unknown, but the present inventors believe that the inclusion of C in the rare earth magnet 1 facilitates the formation of a compound containing R and C in the grain boundary phase of the subphase 13. . A phase composed of a compound containing R and C is hereinafter referred to as an RC rich phase. Note that the RC rich phase may contain M and/or T. The present inventors believe that the coercive force HcJ of the rare earth magnet 1 is improved because the RC rich phase is a non-magnetic phase and has a high magnetic separation effect.

In the rare earth magnet 1 according to the present embodiment, the ratio of Sm to R is preferably large, and the content ratio of Sm to the entire R in the entire rare earth magnet is preferably 50 at % or more.

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

Therefore, it is preferable that the content of Sm with respect to the entire R is 50 at % or more and 99 at % or less, and the total content of Pr and Nd is preferably 1 at % or more and 50 at % or less. In addition, as R, rare earth elements other than Sm, Pr and Nd may be contained within a range that does not significantly 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 this 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 contained as appropriate. In addition, impurities derived from raw materials may be included. The content of elements other than the elements described above is arbitrary, but is, for example, 3% or less with respect to the entire rare earth magnet 1 .

ICP mass spectrometry is used to analyze the composition ratio of the entire rare earth magnet 1 according to this embodiment. In addition, if necessary, combustion in an oxygen stream-infrared absorption method may be used in combination.

A preferred example of the method for manufacturing the rare earth magnet 1 according to this embodiment will be described below.

The rare earth magnet 1 can be manufactured by appropriately combining a casting method, a strip casting method, an ultra-rapid solidification method, a vapor deposition method, an HDDR method, a sintering method, a hot working method, and the like. An example of the 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 quenching method, a gas atomization method, and the like, and it is preferable to use the single roll method. In the single roll method, the molten alloy is discharged from a nozzle and caused to collide with the peripheral surface of the cooling roll to rapidly cool the molten alloy to obtain a ribbon-like or flake-like quenched alloy. The single roll method has high mass productivity and good reproducibility of quenching conditions compared to other ultra-rapid solidification methods.

As a raw material, first, an alloy ingot having a desired composition ratio is prepared. The raw material alloy can be produced by melting a raw material metal containing R, T, M, etc., in an atmosphere of an inert gas, preferably Ar, by a melting method such as arc melting. When C or other elements are desired to be contained as appropriate, they can be contained in the same manner.

A rapidly quenched ribbon is produced from the alloy ingot produced by the above method by a super-rapid solidification method. As the ultra-rapid solidification method, for example, the above alloy ingot is cut into small pieces by a stamp mill or the like to obtain small pieces, the obtained small pieces are melted by high frequency in an Ar atmosphere to obtain molten metal, and the obtained molten metal is melted at high speed. A melt spin method can be used in which the material is discharged onto a rotating chill roll and rapidly solidified. The melt that has been quenched by the cooling rolls becomes a quenched ribbon that has been quenched and solidified into a ribbon shape.

In addition, the method of cutting into small pieces is not limited to a stamp mill. The atmosphere during high-frequency melting is not limited to the Ar atmosphere. The rotation speed of the chill roll is arbitrary. For example, it may be 10 m/s or more and 100 m/s or less. Any material may be used for the cooling roll, and 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 steps of coarse pulverization and fine pulverization, or may be performed in one step of fine pulverization only.

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

Next, the obtained compact is sintered and crystallized at the same time to obtain the rare earth magnet 1 . Sintering is performed by a normal sintering method. A normal sintering method is a sintering method that does not apply pressure 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 lower sintering temperature than before because part of the heterogeneous phase becomes a liquid phase component with a low melting point during sintering. . Specifically, the sintering temperature (crystallization temperature) can be 500° C. or higher. Also, the temperature may be 750° C. or lower. 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 0.01° C./s or more and 30° C./s or less.

Further, in order to improve the distribution of M in the different phases 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 carried out by raising the temperature from 500° C. to 650° C. at a rate of from 10° C./s to 30° C./s and then keeping the temperature at the heat treatment temperature for 10 minutes to 300 minutes. These treatments are usually performed in an Ar atmosphere.

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

In addition, when the above-described crystallization treatment causes the alloy of R and T to become single magnetic domain grains of the R ₅ T ₁₇ crystal phase, an anisotropic magnet can be obtained by performing compacting in a magnetic field. is also possible.

An example of the method for manufacturing the rare earth magnet 1 according to the present embodiment has been described above, but the method for manufacturing the rare earth magnet 1 is arbitrary.

For example, in the above manufacturing method, the one-alloy method using one type of quenched ribbon is used, but the two-alloy method using two types of quenched ribbons may be used. Also, 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. Then, they can be mixed during or after pulverization of each quenched ribbon. In the two-alloy method, the quenched ribbon composed of R and T mainly becomes the main phase 11 , and the quenched ribbon composed of R and M mainly becomes the subphase 13 . The quenched ribbon composed of R and M as the main subphase 13 may contain T to form a quenched ribbon composed of R, T and M. Also, two or more types of quenched ribbons having different contents of R, T and M may be used. In this case, all the quenched ribbons may not contain all of R, T and M. All the quenched ribbons should contain one or more selected from R, T and M. The total area ratio of the subphase 13 can also be controlled by controlling the mixing ratio of each quenched ribbon. If the amount is small, a single metal powder 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 subjecting the quenched ribbon with R:T close to 5:17 to the crystallization treatment. Crystallization conditions in this case are arbitrary. For example, the crystallization temperature can be 500° C. or more and 700° C. or less, the crystallization time can be 1 minute or more and 50 hours or less, and the cooling rate after crystallization can be 0.01° C./s or more and 30° C./s or less. When two or more kinds of quenched ribbons composed of R and T are used, only the quenched ribbons having an R:T ratio of close to 5:17 may be crystallized.

In addition, when the above-described crystallization treatment causes the alloy of R and T to become single magnetic domain grains of the R ₅ T ₁₇ crystal phase, an anisotropic magnet can be obtained by performing compacting in a magnetic field. is also possible.

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

(Experimental example 1)
First, raw materials consisting of Sm, Pr, Nd, Fe, Cu, Zn, Al, Ga, Ag, Au, Si, Ge, Sn and/or C or alloys thereof were prepared. Each raw material was blended so that the resulting magnet would have the composition shown in Table 1 below, and an alloy ingot was produced by arc melting in an Ar atmosphere. A stamp mill was then used to cut the alloy ingot into small pieces. Next, the small piece was melted by 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 onto 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 pulverized 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 molding the fine powder into a rectangular parallelepiped shape of 10 mm × 15 mm × 12 mm at 100 MPa without a magnetic field, the temperature rise rate is 5 ° C./min, the sintering temperature is 700 ° C. or 725 ° C., and the sintering time is 1 hour. After hardening and sintering, it was quenched to room temperature. After cooling, the sample 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. In addition, it was confirmed that the composition of the obtained sintered body had the composition shown in Table 1 using ICP mass spectrometry and, if necessary, combustion in an oxygen stream-infrared absorption method. Specifically, the combustion in an oxygen stream-infrared absorption method was used to measure the C content.

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 backscattered electron image was observed using a scanning electron microscope (SEM). The SEM used was equipped with an energy dispersive X-ray spectroscope (EDS). From the contrast of the backscattered electron image, it can be roughly determined whether each region is the main phase or the subphase. Next, an observation area of 50 μm×50 μm containing the main phase and the subphase was determined from the backscattered electron image, and elemental mapping was performed using EDS. From the elemental mapping data, it was determined that the phase in which the ratio of R and T was approximately 5:17 was the main phase, and the region other than the vacancies was the subphase. Finally, the main and subphases were identified using both the contrast of the backscattered electron image and the elemental mapping data. 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. In addition, the total area ratio (%) of the subphases was determined from 100×(total area of subphases)/(area of observation region−area of pores). The above operation was performed on four observation areas of 50 μm×50 μm, and the average value was taken as the average content ratio of M in the subphase and the total area ratio of the subphase in each sample.

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

The magnetic properties of the samples were measured using a pulse excitation BH curve tracer. In this example, the case where the residual magnetic flux density Br was 3.5 kG was regarded as good. Also, the case where the coercive force HcJ was 30 kOe or more was evaluated as good.

The relative density (%) of the sample was obtained by 100×(the dimensional density obtained by actually measuring the size and mass of each sample)/(theoretical density of the 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. A sample with a relative density of 80% or more was considered to have a good sintered density.

From Table 1, each example in which the total area ratio of the subphases was 3 to 25% and the average content ratio of M in the subphases was 5 to 30 at% had high relative densities and excellent magnetic properties. On the other hand, Comparative Example 1, which did not contain M and had a low total area ratio of subphases, had a low relative density and poor magnetic properties.

(Experimental example 2)
In Experimental Example 2, unlike Experimental Example 1 in which one type 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 production method up to the production of the quenched ribbon is the same as in Experimental Example 1.

Next, the quenched ribbon 1 was subjected to a 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 mixed at the alloy mixing ratio (weight ratio) shown in Table 2 below and pulverized 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. Table 2 shows the results. Also, it was confirmed by ICP mass spectrometry that the composition of the obtained sintered body had the composition shown in Table 2.

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

(Experimental example 3)
In Examples 23 and 24 of Experimental Example 3, three types of quenched ribbons having 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 was created. The production method up to the production 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 were the same as those in Examples 23 and 24, but the quenched ribbon 3 was not used, and instead fine powder of Zn alone was used. .

Next, the quenched ribbon 1 was subjected to a 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 (in Example 25, each coarse powder and a fine powder of Zn alone) was mixed and finely pulverized while being mixed at the alloy mixing ratio (weight ratio) shown in Table 3 below. 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. Table 3 shows the results. Also, it was confirmed by ICP mass spectrometry that the composition of the obtained sintered body had the composition shown in Table 3.

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

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

Claims (3)

A rare earth magnet comprising R, T and M,
R is one or more rare earth elements essentially including 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 is one type,
Consists of a main phase composed of crystal grains having a Nd ₅ Fe ₁₇ -type crystal structure, and a subphase that is a phase other than the main phase,
at least a portion of said subphase comprises M;
The average content of M in the subphase is 5 at% or more and 30 at% or less,
A rare earth magnet, wherein the total area ratio of the subphases in any cross section of the rare earth magnet is 3% or more and 25% or less. 2. The rare earth magnet according to claim 1, further comprising C, wherein the content of C is more than 0 at % and not more than 15 at % with respect to the entire rare earth magnet. Further containing Pr and/or Nd as R,
3. The rare earth magnet according to claim 1, wherein the content of Sm with respect to the entire R is 50 at % or more and 99 at % or less, and the total content of Pr and Nd is 1 at % or more and 50 at % or less.

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