JPWO2019182039A1 - Rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare earth magnet having a compound having an Nd5Fe17 type crystal structure as a main phase, which has a high sintering density even when fired by a normal sintering method, and has high residual magnetic flux density Br and coercive force HcJ. Get a magnet. A rare earth magnet containing R, T and M. R is one or more rare earth elements that require Sm. T is Fe alone or Fe and Co. M is at least one selected from the group consisting of Cu, Zn, Al, Ga, Ag, Au, Si, Ge and Sn. It is composed of a main phase composed of crystal particles having an Nd5Fe17 type crystal structure and a subphase which is a phase other than the main phase. At least a part of the subphase contains M, and the average content of M in the subphase is 5 at% or more and 30 at% or less. The total area ratio of the subphases on any cut surface of the rare earth magnet is 3% or more and 25% or less. [Selection diagram] Fig. 1

Description

The present invention relates to rare earth magnets.

The production of rare earth magnets is increasing year by year due to their high magnetic properties, and they are used in various applications such as for various motors, various actuators, and MRI devices.

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

However, the grain boundary phase control technology has not been established for the magnet material whose main phase is the _{Sm 5} Fe _{17 intermetallic compound.} A magnet that utilizes the high coercive force of a magnet material whose main phase is an Sm ₅ Fe _{17 intermetallic compound 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, sintering is performed at a lower temperature than in a normal sintering method. In addition, pressurization is required during sintering. However, the sintered magnet described in Non-Patent Document 1 has a low density as a sintered body. In addition, a soft magnetic phase exists as a subphase. Further, in general, when the SPS method is used, the magnetic characteristics are deteriorated as compared with the case where the normal sintering method is used. From the above, the sintered magnet described in Non-Patent Document 1 has not obtained the magnetic characteristics expected in the stage before sintering. Further, the SPS method itself is a sintering method that is relatively unsuitable for mass production.

Japanese Unexamined Patent Publication No. 2008-133496

Materials Science and Engineering 1 (2009) 012032.

The present invention has been made in recognition of such a situation, _{and is a rare earth magnet having a compound having an Nd 5} Fe ₁₇ type crystal structure as a main phase, and has a high sintering density even when fired by a normal sintering method. An 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 that require Sm, T is Fe alone or Fe and Co, and M is at least selected from the group consisting of Cu, Zn, Al, Ga, Ag, Au, Si, Ge and Sn. It is one kind
It is _{composed of a main phase composed of crystal particles having an Nd 5} Fe ₁₇ type crystal structure and a subphase which is a phase other than the main phase.
At least part of the subphase contains M
The average content of M in the subphase is 5 at% or more and 30 at% or less.
The total area ratio of the subphase on 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 by a normal sintering method. In addition, the residual magnetic flux density Br and the coercive force HcJ also increase. 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 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 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.

It is a reflected electron image of Example 3.

An embodiment (embodiment) for carrying out the present invention will be described in detail. The present invention is not limited to 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 the present embodiment _{has crystal particles having an Nd 5} Fe ₁₇ type crystal structure (space group P6 ₃ / mcm) as the main phase 11. Then, the phase other than the main phase 11 is designated as the sub-phase 13. In the following description, _{a phase composed of crystal particles 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 contain an amorphous phase. However, it is preferable that there are few RT crystal phases having soft magnetism or low coercive force, such as _{the R 2} T ₁₇ crystal phase and the RT _{3 crystal phase.} Further, what kind of crystals the rare earth magnet 1 according to the present embodiment contains can be confirmed by using an X-ray diffraction method (XRD), a scanning electron microscope (SEM) having 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 is produced in the subphase 13. Hereinafter, the phase composed of a compound containing R and M will be 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. The compounds containing R and M constituting the RM phase have a low melting point and tend to become grain boundary phases by sintering. In other words, M diffuses into the grain boundary phase to give a compound containing R and M. Note that the grain boundary phase in this embodiment is that the secondary phase present between the crystal grains of the plurality of R ₅ T ₁₇ crystal phase.

The formation of the RM phase makes it difficult for 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, to precipitate.} Then, 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 it is possible to obtain a rare earth magnet 1 having a sufficient sintering density without pressurization. Further, it is possible to improve the residual magnetic flux density Br and the coercive force HcJ of the rare earth magnet 1 obtained by having a sufficient sintering density.

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

Further, it is preferable to use an SEM (so-called SEM-EDS) equipped 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 the vacancies are the sub-phase 13. By combining the backscattered electron image and the element mapping image, the main phase 11 and the sub-phase 13 can be distinguished more accurately. Further, by using the energy dispersive X-ray spectroscopy (TEM-EDS) using a transmission electron microscope (TEM) and the electron diffraction method in combination, it is possible to distinguish the crystal structure and the amorphous phase of a minute region.

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

The average content ratio of M is calculated by measuring and averaging the content ratio of M in all subphases 13 in the measurement range using SEM-EDS in a measurement range having a size of 50 μm × 50 μm or more. The measurement range may be a measurement range having a size of 50 μm × 50 μm or more alone, or the total of the plurality of measurement ranges may be 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 the density tends to be high. Then, 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 becomes difficult to densify and the sintering 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 non-uniform. Further, 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 becomes difficult to densify and the sintering density tends to decrease. 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 tend 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 having a size of 50 μm × 50 μm or more and dividing by the area of the measurement range. To do. The measurement range may be a measurement range having a size of 50 μm × 50 μm or more alone, or the total of the plurality of measurement ranges may be 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 tends to be densified and the density tends to be high. Then, 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 becomes difficult to densify and the sintering 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 non-uniform. Further, the residual magnetic flux density Br and the coercive force HcJ tend to decrease. If the total area ratio of the sub-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 the present embodiment is a rare earth magnet containing R, T and M. R is selected from one or more rare earth elements requiring 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 species. 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, and preferably 24.2 at% or more and 30.6 at% or less. If the R content is too small or too large, _{it becomes difficult for the R 5} T ₁₇ crystal phase to be sufficiently formed.

The content ratio of T in the rare earth magnet 1 is arbitrary. The content ratio of Co to the whole 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 tends to be. Further, the larger the Co content ratio, the higher the magnetic flux density tends to be.

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% or less. If the content ratio 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 ratio of M in the subphase 13 described later becomes too small. If the M content is too large, the average M content in the subphase 13 will be too large. Alternatively, 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. The content ratio of C to the entire rare earth magnet 1 is preferably more than 0 at% and 15 at% or less, and more preferably 1.0 at% or more and 7.5 at% or less.

The rare earth magnet 1 according to the present embodiment tends to have a coercive force HcJ improved by containing C. The reason why the coercive force HcJ is improved is unknown, but the present inventors think that the inclusion of C in the rare earth magnet 1 facilitates the formation of compounds containing R and C in the grain boundary phase of the subphase 13. .. Hereinafter, the phase composed of a compound containing R and C will be referred to as an RC-rich phase. The RC-rich phase may contain M and / or T. The present inventors consider 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.

Regarding 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 total 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. Further, 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 subphase 13 can be obtained.} However, if the total content ratio 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, 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 the present embodiment may contain an element other than the above-mentioned elements. For example, elements such as Bi, Ti, V, Cr, Mn, Zr, Nd, Mo, and Mg can be appropriately contained. It may also contain impurities derived from the raw material. The content of elements other than the above-mentioned elements is arbitrary, but is, for example, 3% or less with respect to the entire rare earth magnet 1.

The ICP mass spectrometry method is used to analyze the composition ratio of the entire rare earth magnet 1 according to the present embodiment. Further, if necessary, the 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, an ultra-quenching solidification method, a vapor deposition method, an HDDR method, a sintering method, a hot working method, and the like. An example of a manufacturing method using the method will be described.

Specifically, there are various types of ultra-quezing solidification methods such as a single roll method, a bi-roll method, a centrifugal quenching method, and a gas atomizing method, but it is preferable to use the single roll method. In the single roll method, the molten alloy is discharged from a nozzle and collides with the peripheral surface of the cooling roll to rapidly cool the molten alloy to obtain a flaky or flaky quenching alloy. The single roll method has higher mass productivity and better reproducibility of quenching conditions than other ultra-quezing 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 dissolving the raw metal containing R, T, M and the like in an inert gas, preferably in an Ar atmosphere, by a melting method such as arc melting. When it is desired to appropriately contain C or other elements, it can be contained in the same manner.

From the alloy ingot produced by the above method, a quick-cooled thin band is produced by an ultra-quezing solidification method. As an ultra-quezing solidification method, for example, the above alloy ingot is fragmented with a stamp mill or the like to obtain small pieces, and the obtained small pieces are melted at high frequency in an Ar atmosphere to obtain a 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 cooling roll and rapidly cooled and solidified. The molten metal rapidly cooled by the cooling roll becomes a quick-cooled thin band that has been quick-cooled and solidified in a thin band shape.

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

Next, the obtained quenching thin band 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 product. The molding pressure 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 molded product and crystallizing it at the same time. Sintering is performed by a normal sintering method. The normal sintering method is a sintering method in which no pressurization is performed at the time of sintering, and generally requires a higher sintering temperature as compared with the SPS method or the like. The rare earth magnet 1 according to the present embodiment can be sintered without pressurization and at a lower sintering temperature than before because a part of the different phase becomes a liquid phase component having a low melting point during sintering. .. Specifically, the sintering temperature (crystallization temperature) can be 500 ° C. or higher. Further, the temperature may be 750 ° C. or lower. The atmosphere at the time of sintering is arbitrary. For example, it can be an Ar atmosphere. 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 step is effective. This heat treatment is performed by raising the temperature to a heat treatment temperature of 500 ° C. or higher and 650 ° C. or lower at a rate of 10 ° C./s or higher and 30 ° C./s or lower, and then keeping the heat treatment temperature for 10 minutes or longer and 300 minutes or lower. Usually, these processes are performed in an Ar atmosphere.

Further, when the one alloy method is used, the quenching thin band 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. or higher and 700 ° C. or lower, the crystallization time can be 1 minute or longer and 50 hours or lower, and the cooling rate after crystallization can be 0.01 ° C./s or higher and 30 ° C./s or lower.

Further, when the alloy composed of R and T is _{a single magnetic domain particle of the R 5} T ₁₇ crystal phase by performing the above crystallization treatment, it is formed into an anisotropic magnet by molding in a magnetic field. Is also possible.

Although an example of the method for producing the rare earth magnet 1 according to the present embodiment has been described above, the method for producing the rare earth magnet 1 is arbitrary.

For example, in the above manufacturing method, a one-alloy method using one kind of quenching thin band is used, but a two-alloy method using two kinds of quenching thin bands may be used. Further, three or more types of quenching thin bands may be used.

Specifically, for example, a quenching thin zone composed of R and T and a quenching thin zone consisting of R and M are prepared. Then, each quenching thin band can be mixed during or after crushing. In the case of the two-alloy method, the quenching thin zone composed of R and T is mainly the main phase 11, and the quenching thin band composed of R and M is mainly the subphase 13. T may be contained in the quenching thin band composed of R and M, which is mainly the subphase 13, to form a quenching thin band composed of R, T and M. Further, two or more types of quenching thin bands having different contents of R, T and M may be used. In this case, not all the quenching thin bands need to contain all R, T and M. All quenching strips may contain one or more selected from R, T and M. The total area ratio of the sub-phase 13 can also be controlled by controlling the mixing ratio of each quenching thin zone. If the amount is small, a powder made of a single metal may be used instead of the quenching thin band.

When the two alloy method is used, only the quenching thin band composed of R and T may be crystallized before pulverization. _{In particular, the R 5} T ₁₇ crystal phase can be stably produced by crystallizing the quenching thin zone in which 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. or higher and 700 ° C. or lower, the crystallization time can be 1 minute or longer and 50 hours or lower, and the cooling rate after crystallization can be 0.01 ° C./s or higher and 30 ° C./s or lower. When two or more types of quenching thin bands composed of R and T are used, only the quenching thin band having R: T close to 5:17 may be crystallized.

Further, when the alloy composed of R and T is _{a single magnetic domain particle of the R 5} T ₁₇ crystal phase by performing the above crystallization treatment, it is formed into an anisotropic magnet by molding in a magnetic field. Is also possible.

Hereinafter, the contents of the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(Experimental Example 1)
First, a raw material composed 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 obtained magnet had the composition shown in Table 1 below, and an alloy ingot was prepared by arc melting in an Ar atmosphere. Next, the alloy ingot was fragmented using a stamp mill to obtain a fragment. Next, the small pieces were melted at a high frequency in an Ar atmosphere of 50 kPa to obtain a molten metal. Next, a quenching thin band 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 rapidly cooled thin band. Next, the quenching thin band was coarsely pulverized and finely pulverized to obtain a fine powder having an average particle size of about 5 μm. Coarse pulverization was performed by a stamp mill, and fine pulverization was performed by a jet mill. Next, the fine powder was formed into a rectangular parallelepiped shape of 10 mm × 15 mm × 12 mm at 100 MPa with no magnetic field, and then 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, the combustion in 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 the sub-phase of each of the obtained samples were distinguished, and the composition of each phase was analyzed. Specifically, the cross section obtained by cutting each of the obtained samples was mirror-processed by ion milling, and the reflected electron image was observed using a scanning electron microscope (SEM). As the SEM, one equipped with an energy dispersive X-ray spectrometer (EDS) was used. From the contrast of the reflected electron image, it can be roughly determined whether each region is the main phase or the sub-phase. Next, an observation region of 50 μm × 50 μm including the main phase and the sub-phase was determined from the image of the backscattered electron image, and element mapping was performed using EDS. From the element 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 other regions excluding the vacancies were the sub-phases. Finally, the contrast of the backscattered electron image and the element mapping data were used together to identify the main phase and the subphase. Next, the average composition of the subphase was specified from the element 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 subphase was specified from 100 × (total area of subphase) / (area of observation area-area of vacancies). The above operation was performed for four 50 μm × 50 μm observation regions, 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.

In addition, it was confirmed by using XRD that all the examples and comparative examples had an Nd ₅ Fe _{17 type crystal structure.} Then, it was confirmed that the compositions shown in Table 1 were obtained by using the ICP mass spectrometry method and, if necessary, the combustion in oxygen stream-infrared absorption method in combination for all the samples of Examples and Comparative Examples.

The magnetic properties of the sample were measured using a pulse excitation type BH curve tracer. In this example, the case where the residual magnetic flux density Br is 3.5 kG is considered to be good. Further, the case where the coercive force HcJ was 30 kOe or more was regarded as good.

The relative density (%) of the sample was obtained by 100 × (dimension 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 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 to be good.

From Table 1, each example in which the total area ratio of the sub-phase was 3 to 25% and the average content ratio of M in the sub-phase was 5 to 30 at% had high relative density and excellent magnetic characteristics. On the other hand, in Comparative Example 1 which did not contain M and had a low total area ratio of the subphase, the relative density was low and the magnetic characteristics were also lowered.

(Experimental Example 2)
In Experimental Example 2, unlike Experimental Example 1 in which one type of quenching strip was prepared, two types of quenching strips having the compositions shown in Table 2 below were prepared. Specifically, a quenching thin band 1 containing R and T and a quenching thin band 2 containing R and M were prepared. The manufacturing method until the quenching thin band is produced is the same as in Experimental Example 1.

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

Next, each quenching thin band was roughly pulverized using a stamp mill to obtain a coarse powder of each quenching thin band. Then, using a jet mill, each crude powder was finely pulverized while being mixed at the alloy mixing ratio (weight ratio) shown in Table 2 below to obtain a fine powder.

After that, 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 sub-phase was 3 to 25% and the average content ratio of M in the sub-phase was 5 to 30 at% had high relative density and excellent 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 of M in the subphase was too large, the residual magnetic flux density Br and the coercive force HcJ decreased. 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 quenching strips having the compositions shown in Table 3 below were prepared. Specifically, a quenching thin band 1 containing R and T, a quenching thin band 2 containing R and T but having a different composition from the quenching thin band 1, and a quenching thin band containing M and R or T. 3 and was created. The manufacturing method until the quenching thin band is produced is the same as in Experimental Example 1. In Example 25 of Experimental Example 3, the quenching thin band 1 and the quenching thin band 2 are the same as those of Examples 23 and 24, but the quenching thin band 3 is not used, and a fine powder of Zn alone is used instead. ..

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

Next, each quenching thin band was roughly pulverized using a stamp mill to obtain a coarse powder of each quenching thin band. Then, using a jet mill, each crude powder (in Example 25, each crude powder and a fine powder of Zn alone) is mixed at the alloy mixing ratio (weight ratio) shown in Table 3 below and finely pulverized to perform fine powder. Got

After that, 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. Further, 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 sub-phase was 3 to 25% and the average content ratio of M in the sub-phase was 5 to 30 at% had high relative density and excellent magnetic characteristics.

1 ... Rare earth magnet 11 ... Main phase 13 ... Subphase

Claims (3)

A rare earth magnet containing 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 at least selected from the group consisting of Cu, Zn, Al, Ga, Ag, Au, Si, Ge and Sn. It is one kind
It is _{composed of a main phase composed of crystal particles having an Nd 5} Fe ₁₇ type crystal structure and a subphase which is a phase other than the main phase.
At least part of the subphase contains M
The average content of M in the subphase is 5 at% or more and 30 at% or less.
A rare earth magnet characterized in that the total area ratio of the subphase on 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, and the content ratio of C to the entire rare earth magnet is more than 0 at% and 15 at% or less. R also includes Pr and / or Nd as R.
The rare earth magnet according to claim 1 or 2, wherein the content ratio of Sm with respect to the entire 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.

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