JP5910074B2 - R-T-Zr-B rare earth metal magnet - Google Patents

Description

  The present invention relates to an R—T—Zr—B rare earth metal magnet.

  Conventionally, an R-T-B rare earth metal magnet (R is at least one element selected from Y or rare earth elements, and T is at least one element of Fe and Co) has excellent magnetic properties. And used in various electrical equipment. In recent years, the application to transportation equipment has been actively performed, and the demand has been increasing. The coercive force (HcJ), which is the main characteristic of this R-T-B rare earth metal magnet, is improved by making the sintered body texture finer. The mechanism for improving the coercive force of the sintered body has not yet been clarified, but crystal particles having the same particle size as that of the RTB-based rare earth metal magnet powder used in the production of the molded body are obtained. Therefore, it is considered that the refinement of the sintered body structure is important for improving the coercive force. Therefore, in order to refine the sintered body structure, it is necessary to refine the pulverized particle diameter of the RTB-based rare earth metal magnet powder used for producing the molded body.

  Recently, research results have been reported that the coercive force of sintered bodies can be improved by using Nd-Fe-B rare earth metal magnet magnetic powder having a pulverized particle size of about 1 μm. Has attracted attention from the viewpoint of reducing the amount of heavy rare earths used, including Dy. The heavy rare earth refers to a rare earth element having 7 or more 4f electrons, specifically, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. In particular, Dy is effective in improving the coercive force of an R-T-B rare earth magnet. However, because the market price has soared, the price of a product using the magnet body is also increased through the price of the magnet body including Dy. It tends to rise. For this reason, market demands for RTB-based rare earth metal magnets with reduced Dy usage are increasing.

  Usually, an R-T-B rare earth metal magnet is manufactured by molding and sintering an alloy powder prepared to have an average particle size of about 5 μm by pulverization. The crystal grain size of the R-T-B rare earth metal magnet greatly depends on the grain size of the alloy powder before sintering. This is thought to be due to the fact that oxides on the surface of the alloy particles, disorder of the crystal structure, etc. have the effect of suppressing sintering between the pulverized particles, and it is difficult to grow beyond the pulverized particle size. . Therefore, in order to refine the sintered body structure, it is necessary to use an alloy powder having a smaller particle size. Therefore, in order to obtain a magnet having a high coercive force, an ultrafine pulverization technique for reducing the pulverized particle diameter as much as possible is required. Although it is possible to pulverize to about 1 μm with the current ultrafine pulverization technique, in the present invention, the technique of pulverizing to a particle diameter of less than 2 μm is considered as the ultrafine pulverization technique.

  As this ultra fine pulverization technique, it is common to use an air flow pulverization method or a wet pulverization method using helium gas. Since the former is not a closed system, helium, which is a pulverized gas, is always released into the atmosphere, and a huge amount of helium gas is required during pulverization. The latter is a technique in which the magnetic powder is stirred together with the liquid and the pulverized beads, and the impact force between the magnetic powder and the beads is used as the main pulverizing force. However, the liquid component tends to remain in the magnetic powder. As a result, there is a problem that the reproducibility of the magnetic properties of the sintered body is lowered. Therefore, a method for producing an alloy powder for a high coercive force sintered body that does not depend on the ultrafine pulverization technique is required.

  In order to solve this, for example, Patent Document 1 proposes refinement of an alloy structure using the HDDR method. According to this prior art, by pulverizing the alloy structure to the submicron order by the HDDR method, a pulverized powder of 2 μm or less can be obtained in a high yield, and the crystal diameter of the sintered body is about 2 μm, which is finer than before. It is said that a sintered body having a proper crystal structure can be obtained. However, the submicron order crystal structure produced by the HDDR method has disappeared during sintering, and the fact that the pulverized particle size and the crystal size of the sintered body are almost equal can be improved. Absent.

  In the field of R-T-B rare earth metal magnets, Zr is known to have an action of suppressing abnormal growth of crystal grains in the sintering process. In the conventional manufacturing method, Zr is used by paying attention to sintering between pulverized particles, and if the pulverized particle size is equal to the crystal particle size of the sintered body, an effect of suppressing the abnormal growth of crystal particles by Zr is expressed. I thought. The abnormal growth of crystal grains is a result of non-uniform sintering between pulverized grains, so it is assumed that Zr has the effect of keeping the sintering rate constant. That is, it is presumed that abnormal growth of the pulverized particles is suppressed by suppressing the sintering at the contact portion between the pulverized particles which is likely to be sintered. That is, it is considered that the effect of suppressing the abnormal growth of crystal grains by Zr is expressed by suppressing the sintering. If the sintering suppression effect of Zr is applied between crystal particles of submicron order produced by the HDDR method, it is considered that a sintered body having a fine structure can be easily produced. The reason why it was not used is that Zr was easily taken into the crystal particles of the RTB-based rare earth metal magnet in the conventional manufacturing method.

  For example, in the alloy casting method such as the ultra-quenching method described in Patent Document 2 and Patent Document 3, the crystal particles of the RTB-based rare earth metal magnet can be refined to the same extent as the HDDR method. On the other hand, a large amount of amorphous component is generated by the rapid quenching. This amorphous component is recrystallized while incorporating surrounding additive elements in the heat treatment in the sintering process, so that the additive elements such as Zr are incorporated into the crystal particles of the R-T-B rare earth magnet, The original sintering suppression effect cannot be expressed. As a result, the sintering between the crystal particles of the R-T-B system rare earth metal magnet is easy to proceed, and the sintered body has a structure having the same pulverized particle size and crystal particle size. Therefore, in order to refine the sintered body structure, an ultra fine pulverization technique has to be used.

JP 2010-219499 A JP-A 63-196014 JP-A 63-29908

  Therefore, the present invention provides an R-T-B rare earth metal magnet having high magnetic properties and particularly excellent coercive force without using the above-described ultrafine pulverization technique in preparation of the raw material alloy powder. An object of the present invention is to provide an R—T—Zr—B-based rare earth metal magnet added with an element.

In order to achieve the above object, the present invention provides RT-Zr-B (R is at least one element selected from Y, La, Ce, Pr, Nd, Sm, Eu, and T is Fe and Co. of at least one element.) system comprising a sintered body of a rare earth metal magnet, a sintered body of said rare earth metal magnet to R 29 wt% to 37 wt%, 2 wt beyond 0.5 Zr %, The main phase crystal diameter is 0.1 μm to 0.5 μm, Zr is present in the main phase grain boundary, and the grain with respect to the sum of the Zr content in the main phase and the Zr content in the grain boundary phase The sintered body of the R—T—Zr—B-based rare earth metal magnet characterized in that the ratio of Zr in the field phase is 60% or more. The present invention improves the crystallinity of the R—T—B system rare earth metal magnet crystal of the raw material alloy and makes it difficult to incorporate additional elements such as Zr into the R—T—B system rare earth metal magnet crystal grains. Since the Zr concentration in the R-T-B rare earth metal magnet crystal grain boundary (between) is higher than that in the TB rare earth metal magnet crystal grain, it has a high structure with a fine structure regardless of the pulverized particle diameter. A sintered body of the R-T-Zr-B rare earth metal magnet can be obtained. In the present invention, “R” is at least one element selected from Y, La, Ce, Pr, Nd, Sm, and Eu, and “T” is at least one element of Fe and Co. Zr is Zr or an alloy containing Zr.

  Moreover, in this invention, even if the grinding | pulverization particle diameter of RTB type rare earth metal magnet powder used for preparation of a molded object is 2-10 micrometers, it shall be set as the sintered magnet body which has a structure | tissue of a submicron order. Is possible. Accordingly, a rare earth metal magnet having a high coercive force can be obtained without using an ultrafine pulverization technique that pulverizes to a particle size of less than 2 μm.

According to the present invention, it is possible to provide an RT— Zr— B rare earth magnet sintered body having a high coercive force without using an ultrafine pulverization technique for pulverizing to a particle diameter of less than 2 μm. it can.

FIG. 1 is a flowchart showing an example of a manufacturing procedure for an RTZr-B rare earth metal magnet according to the present invention.

  Hereinafter, a preferred embodiment of the present RT-Zr-B rare earth metal magnet will be described in detail.

(RT-Zr-B rare earth metal magnet)
The R-T-Zr-B rare earth metal magnet according to the present embodiment includes R (where R is at least one element selected from Y, La, Ce, Pr, Nd, Sm, Eu) as a constituent component. And at least B, Fe, and Zr. Here, the “constituent component” is a main component contained in the R—T—Zr—B-based rare earth metal magnet and refers to a component that contributes to the improvement of magnetic properties. That is, the R—T—Zr—B-based rare earth metal magnet of the present embodiment may contain inevitable impurities different from the above-described constituent components as long as the effect of having an excellent coercive force is not impaired. In this R-T-Zr-B-based rare earth metal magnet, the content of R is 29 to 37% by mass, preferably 30 to 35% by mass. In addition, “mass%” of each element in the R—T—Zr—B rare earth metal magnet is a mass ratio with respect to the whole R—T—Zr—B rare earth metal magnet.

  If the R content is less than 29% by mass, the R2T14B phase crystal particle diameter, which is the main crystal phase of the RTZr-B rare earth metal magnet, is on the order of submicrons, so Since the surface area per volume is large, the thickness of the R-rich phase existing between the crystal grains becomes thin. As a result, it becomes difficult to magnetically separate the R2T14B phase crystals, and the excellent coercive force is impaired. On the other hand, when R exceeds 37% by mass, the volume ratio of the R2T14B phase, which is the main crystal phase, decreases, and the residual magnetic flux density decreases. In addition, the oxygen content increases due to the reaction between R and oxygen, and accordingly, the R-rich phase effective for improving the coercive force tends to decrease.

  Since Nd and Pr are relatively abundant and inexpensive among the rare earth elements used as magnet materials, R-T-Zr-B rare earth metal magnets contain at least one element of Nd and Pr as R. Preferably, it contains Nd.

  In the present case, T in the R—T—Zr—B-based rare earth metal magnet is T is at least one element of Fe and Co. Here, the content of Co is 30% by mass or less, preferably 5 to 15% by mass. Co forms the same phase as Fe, but the inclusion of Co can improve the Curie temperature and corrosion resistance.

  The content of Zr in the RT-Zr-B rare earth metal magnet is more than 0.50% by mass and not more than 2.0% by mass, preferably 0.60 to 1.8% by mass, and more. Preferably it is 0.65-1.7 mass%. Zr has a function of suppressing sintering between R—T—Zr—B-based rare earth metal magnet crystal particles in the sintering process, and is thus very important for miniaturization of the sintered body structure. If Zr is 0.50% by mass or less, the effect of suppressing grain growth cannot be obtained, and if it exceeds 2.0% by mass, high magnetic properties cannot be obtained.

  The RT-Zr-B rare earth metal magnet according to the present embodiment may contain an additive element or an inevitable impurity in addition to the above-described R, B, Zr, and Fe, which are essential elements. .

  The lower the oxygen content in the RT-Zr-B rare earth metal magnet, the better. The RT-Zr-B rare earth metal magnet more preferably does not contain any oxygen. However, it is difficult to manufacture an RTZrB-based rare earth metal magnet that does not contain oxygen at all in the manufacturing process. From such a viewpoint, the oxygen content is preferably 0.2% by mass or less, more preferably 0.15% by mass or less, and further preferably 0.1% by mass or less.

  The R—T—Zr—B-based rare earth metal magnet may contain another element different from the above essential elements as long as the effect of having an excellent coercive force is not impaired. For example, the coercive force can be further improved by containing Ga in an amount of 0.1 to 0.5% by mass. Examples of elements other than Ga include elements such as Ti, Bi, Sn, Nb, Ta, Si, V, Ag, and Ge. However, from the viewpoint of maintaining high magnetic properties, the content of elements other than Ga is preferably 1% by mass or less, more preferably 0.5% by mass or less, in total.

  The average particle size of the pulverized particles that are the raw material alloy of the RTZr-B rare earth metal magnet of the present embodiment is 2 to 10 μm, more preferably 4 to 6 μm. It is relatively easy to obtain a pulverized powder having an average particle diameter of about 2 μm by using a conventional airflow pulverization method, and high productivity is guaranteed. Further, the smaller the pulverized particle diameter is, the larger the surface area per volume of the pulverized particles is. Therefore, when the pulverized particle diameter is less than 2 μm, the oxidation resistance is remarkably lowered, and the magnetic properties are easily lowered. On the other hand, when the pulverized particle diameter exceeds 10 μm, the capillary force due to the liquid phase is not sufficiently exhibited in the sintering process, and sintering becomes difficult.

  About the average particle diameter of the crystal particle of a R-T-Zr-B type rare earth metal magnet, 0.2-0.5 micrometer is preferable. When the thickness is less than 0.2 μm, for example, in a Nd—Fe—Zr—B-based rare earth metal magnet crystal, the crystal magnetic anisotropy of the Nd 2 Fe 14 B crystal is lowered, and a high coercive force cannot be obtained. Since the single domain critical diameter of the Nd2Fe14B crystal is said to be about 250 to 350 nm, this range should be the crystal particle diameter range in which the highest coercive force can be obtained, but there are crystal particles of about 0.5 μm. However, since a high coercive force can be obtained, the upper limit of the average particle diameter is set to 0.5 μm in the present invention. The average grain size of the R—T—Zr—B rare earth metal magnet of this embodiment can be obtained as the average value of the grain size of the crystal grains in the observation field of view of the scanning electron microscope magnified 20000 times. .

(Production method)
Next, the suitable manufacturing method of the RTZr-B type rare earth metal magnet concerning this invention is demonstrated, referring drawings.

  FIG. 1 shows an example of a manufacturing procedure of an RTZr-B rare earth metal magnet according to the present invention. As shown in FIG. 1, the manufacturing method of the RTZR-B rare earth metal magnet of this embodiment includes a preparation step (S1) for preparing an RTZZr-B rare earth metal magnet raw material alloy, An HDDR treatment step (S2) for preparing HDDR powder as a treatment alloy by subjecting an RT-Zr-B rare earth metal magnet raw material alloy to HDDR treatment, and a hydrogen storage step (S3) for causing the HDDR powder to occlude hydrogen gas. Pulverizing the HDDR powder occluded with hydrogen gas to obtain an alloy powder having an average particle size of 2 to 10 μm (S4), molding the alloy powder in a magnetic field and sintering it, A sintering step (S5) to be obtained, and an aging treatment step (S6) for subjecting the sintered body to an aging treatment.

(Preparation process)
In the preparation step (S1), an RTZ-Zr-B rare earth metal magnet raw material alloy, which is an RTZr-B rare earth metal magnet compound, is prepared by, for example, strip casting (SC). In order to increase the crystallinity of the R—T—B system rare earth metal magnet crystal in the alloy, the alloy is held at 1000 ° C. to 600 ° C. for 5 to 48 hours. As a result, the crystallinity of the R—T—B system rare earth metal magnet crystal can be increased, and Zr can be unevenly distributed at the boundary of the R—T—B system rare earth metal magnet crystal particle, and pulverized in the sintering process. Sintering between R-T-B rare earth metal magnet crystals in the particles can be suppressed, and the microcrystalline structure generated by the microcrystallization method such as the HDDR method can be maintained even after sintering. The coercive force of the R-T-Zr-B rare earth metal magnet can be further improved.

  The composition of the RT-Zr-B rare earth metal magnet raw material alloy may be the same as the composition of the RT-Zr-B rare earth metal magnet finally obtained. When the two alloy method is adopted, two types of RT-Zr-B rare earth metal magnet raw material alloys having different compositions may be prepared. The composition and blending ratio of the R—T—Zr—B rare earth metal magnet raw material alloy can be appropriately changed according to the composition of the target R—T—Zr—B rare earth metal magnet. The preparation method of the R—T—Zr—B rare earth metal magnet raw material alloy is not limited to the strip casting method, but can improve the crystallinity of the R—T—B rare earth metal magnet crystal in the raw material alloy. If possible, a known dissolution method may be used.

  The crystallinity of the raw material alloy is performed using, for example, an XRD pattern for the surface that is in contact with the cooling roll in the SC alloy. In the case of an Nd-Fe-B alloy, the ratio of the diffraction intensity of a peak around 2θ = 44.4 ° to the baseline average diffraction intensity of 2θ = 34.0-34.5 ° where no diffraction peak appears in the Nd2Fe14B crystal. Is a standard for high crystal alloys. Since the surface in contact with the cooling roll is the portion that is most rapidly cooled during alloy casting, an amorphous component is likely to be generated. By evaluating the crystallinity of this part, the crystallinity of the entire SC alloy can be guaranteed. By increasing the crystallinity of the raw material alloy, it becomes difficult for Zr to be taken into the crystal of the Nd—Fe—B rare earth metal magnet, and as a result, Zr is unevenly distributed between the Nd—Fe—B rare earth metal magnet crystals. It becomes like this.

(HDDR processing step)
In the HDDR treatment step (S2), the HDDR powder (treated alloy) is prepared by subjecting the RT-Zr-B base material alloy prepared in the preparation step to HDDR treatment. HDDR (Hydrogenation Decomposition Desorption Recombination) can be performed in, for example, two stages of hydrogen storage treatment (S2-1) and dehydrogenation treatment (S2-2).

  In the hydrogen storage process (S2-1), the RTZr-B-based material alloy is held in a hydrogen gas atmosphere at a temperature of 700 to 900 ° C. for 0.5 to 5 hours. As a result, the R—T—Zr—B-based material alloy undergoes phase decomposition.

  In the dehydrogenation process (S2-2), by introducing nitrogen gas, the hydrogen gas partial pressure is reduced to, for example, 100 Pa or less, and hydrogen is removed from the phase-decomposed RT-Zr-B-based material alloy. To do. The R—T—Zr—B-based material alloy is recrystallized by the dehydrogenation treatment.

  The treatment conditions such as the temperature and time of the hydrogen storage treatment (S2-1) and dehydrogenation treatment (S2-2) described above can be adjusted according to the composition of the R—T—Zr—B-based material alloy. In addition, when using two or more types of HDDR powders having different compositions, the HDDR process may be performed separately or the HDDR process may be performed together. The HDDR powder obtained by the HDDR process has a texture in which a plurality of recrystallized particles having a particle size of 1 μm or less are gathered.

  In this way, HDDR treatment is performed, but Zr is present between the R—T—B system rare earth metal magnet crystal particles in the raw material alloy. It tends to exist between rare earth metal magnet crystal grains. As a result, sintering between crystal grains of the R-T-B rare earth metal magnet can be suppressed, and a fine crystal structure can be maintained even after the sintering process. Regarding the presence of a large amount of Zr between R—T—B system rare earth metal magnet crystal grains, for example, by a TEM-EDS analysis method, a region including R—T—B system rare earth metal magnet grain boundaries and R The determination can be made by performing spot analysis in a region not including the grain boundary of the -T-B rare earth metal magnet and comparing the Zr amounts of the two.

  The amount of Zr present between RTB system rare earth metal magnet crystal particles relative to the sum of the amount of Zr present in RTB system rare earth metal magnet crystal particles and between RTB system rare earth metal magnet crystal particles The ratio may be 60% or more, and is ideally 100%. However, at the present time, it is difficult to analyze only between the RTB-based rare earth metal magnet crystal particles, and the analysis results including the signal derived from Zr present in the RTB-based rare earth metal magnet crystal particles. It has become. Therefore, it exists between the RTB-based rare earth metal magnet crystal particles with respect to the sum of the Zr amounts present in the RTB-based rare earth metal magnet crystal particles and between the RTB-based rare earth metal magnet crystal particles. If the ratio of the Zr amount is 60% or more, it is judged that Zr is present more between the RTB-based rare earth metal magnet crystal particles than in the RTB-based rare earth metal magnet crystal particles. It's okay.

(Hydrogen storage process)
Before the pulverization step, it is preferable to have a hydrogen storage step (S3) for storing hydrogen in the treated alloy. In the hydrogen occlusion process, the HDDR powder is occluded with hydrogen by holding the HDDR powder in a hydrogen gas atmosphere. In the present invention, an R-T-B rare earth magnet is produced through a HDDR-treated treated alloy and a fine alloy powder. However, such a treated alloy or alloy powder has high activity and can be easily nitrided or oxidized. There is a tendency to be. For this reason, it is effective to store hydrogen in the HDDR-processed alloy by the hydrogen storage process as described above. As a result, the active rare earth element is deactivated, and it becomes possible to reduce the formation of nitrides and oxides in the grinding process and the sintering process, and the residual magnetic flux density of the R—T—Zr—B rare earth metal magnet. The coercive force can be further improved while maintaining the above. The hydrogen storage step is preferably performed under the conditions of a pressure of 0.05 to 0.25 MPa, a temperature of 20 to 100 ° C., and a holding time of 0.5 to 5 hours in a hydrogen gas atmosphere.

(Crushing process)
In the pulverization step (S4), it is preferable to add an additive such as zinc stearate or oleic acid amide in an amount of about 0.01 to 0.3% by mass based on the HDDR powder. Thereby, the orientation at the time of shaping | molding alloy powder can be improved. For the pulverization, a jet mill, ball mill (dry / wet), vibration mill, wet attritor or the like can be used.

  For example, when using a jet mill, coarse grain classification can be performed by using a jet mill equipped with a classifier. Thereby, an alloy powder having a desired average particle size can be easily prepared. In the pulverization method using a jet mill, a high-pressure inert gas (for example, nitrogen gas) is released from a narrow nozzle to generate a high-speed gas flow, and the high-speed gas flow accelerates coarse HDDR powder. This is a method of pulverizing by generating a collision between each other or a target or a container wall.

  The pulverized particle diameter may be 2 to 10 μm, and it is not necessary to use an ultrafine pulverization technique that makes the pulverized particle diameter less than 2 μm. The reason why the upper limit is 10 μm is as follows. For example, in the sintering of Nd—Fe—Zr—B-based powder, the sintering proceeds by a liquid phase generated from a low melting point component centering on an excess Nd component that does not contribute to the structure of the Nd 2 Fe 14 B crystal. This is called liquid phase sintering, and the capillary attractive force between the liquid phase and the pulverized particles is important, and it is generally 10 μm or less that this attractive force contributes to the sintering. Therefore, in the present invention, the upper limit of the pulverized particle size is set to 10 μm. On the other hand, in order to make the pulverized particle diameter smaller than 2 μm, it is necessary to use an air pulverization method using He gas as the pulverization gas or an ultrafine pulverization technique such as pulverization using a liquid, and the productivity is low. Moreover, since the surface area per volume of the pulverized particles increases as the pulverized particle diameter decreases, the oxidation resistance decreases and the magnetic properties decrease.

  In addition, when applied to a product in which oxidation resistance is particularly important, such as a bonded magnet, the pulverized particle diameter may exceed 10 μm. When applied to a sintered magnet as described above, the capillary attractive force due to the liquid phase is important in the sintering process, so the upper limit is about 10 μm, but especially in the bonded magnet manufacturing process that does not require the sintering process. This is because there is no such limitation.

(Sintering process)
In the sintering step (S5), first, the alloy powder prepared in the pulverization step is molded in a magnetic field to produce a compact. Molding in a magnetic field may be performed by pressing at 69 to 196 MPa (0.7 to 2.0 t / cm 2) in a magnetic field of 955 to 1353 kA / m (12.0 to 17.0 kOe), for example. Next, the molded body is sintered in a vacuum or an inert gas atmosphere to produce a sintered body. For example, the sintering temperature and the sintering time can be set to 900 to 1100 ° C. and 1 to 5 hours, respectively. Since the sintering conditions in the sintering process greatly affect the coercive force (HcJ) of the R-T-B rare earth magnet, the sintering conditions are appropriately set according to the composition, pulverization method, particle size, particle size distribution, and the like. It is preferable.

(Aging process)
In the aging treatment step (S6), the RTD-Zr-B rare earth metal magnet is obtained by holding the sintered body in a vacuum or an inert gas atmosphere at a predetermined temperature for a predetermined time. The aging treatment may be a two-stage treatment that is held at a temperature of about 800 ° C. and about 500 ° C. for a predetermined time (for example, 0.1 to 5 hours), respectively. (5 hours) It is good also as 1 step processing to hold. By performing the aging treatment, the coercive force of the RT-Zr-B rare earth metal magnet can be further improved.

  In addition, in the manufacturing method of the RTZ-Rr-based rare earth metal magnet of the present embodiment, the atmosphere in each process from the HDDR treatment process to the sintering process described above is a low oxygen atmosphere having an oxygen concentration of less than 100 ppm. It is preferable to do.

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

[Production of R-T-Zr-B Rare Earth Metal Magnet]
(Example 1)
An alloy raw material was prepared, Nd = 36.0 mass%, B = 1.00 mass%, Al = 0.1 mass%, Cu = 0.1 mass%, Zr = 1.00 mass%, Ga = 0. The composition was such that 3% by mass and the balance = iron. (Hereinafter, an alloy having this composition is referred to as an alloy A.) A molten metal was created based on this alloy raw material. During casting, this molten metal was poured into a tundish, and then the molten metal was poured onto the quenched copper roll from the tundish. The average cooling rate in the range of the molten metal temperature (about 1400 ° C.) to 1000 ° C. at this time is the temperature measured by the immersion thermocouple for the molten metal temperature in the tundish, and the alloy temperature at the position where the roll is rotated by 60 degrees The difference from the value obtained by measuring with a meter was calculated by repeating the time for which the roll rotated 60 degrees. As a result, the average cooling rate in the range of the molten metal temperature to 1000 ° C. was 800 ° C./second. The finished alloy was stored in a container for collecting the alloy. After being kept at 800 ° C. for 6 hours in this container, it was cooled to obtain a raw material alloy A.

<HDDR processing step>
The prepared R-T-Zr-B-based material alloy A was subjected to HDDR treatment to prepare HDDR powder. Specifically, first, the RT-Zr-B-based raw material alloy A was hydrophase decomposed by holding in a hydrogen gas atmosphere at 800 ° C. for 1 hour. Next, after introducing Ar gas and switching the atmosphere to Ar gas, evacuation is performed to reduce the processing atmosphere under reduced pressure and hold at 800 ° C. for 1 hour to perform dehydrogenation treatment, thereby recrystallized particles. HDDR powder was obtained. The HDDR powder had a texture composed of a plurality of recrystallized particles having a crystal particle diameter of about 0.2 to 0.5 μm.

<Hydrogen storage process>
The HDDR powder was held in a hydrogen gas atmosphere under conditions of a pressure of 0.1 MPa and room temperature for 2 hours, and the HDDR powder was allowed to occlude hydrogen.

<Crushing process>
Zinc stearate is added to HDDR powder occluded with hydrogen in an amount of 0.1% by mass based on the entire HDDR powder, and finely pulverized by a jet mill equipped with a classifier using high-pressure nitrogen gas. An alloy powder of 4 μm was obtained. The average particle diameter of the alloy powder was measured as a volume average particle diameter using a particle size distribution measuring device (trade name: HELOS & RODOS, manufactured by Nippon Laser Co., Ltd.).

<Sintering process>
The obtained alloy powder was press-molded at 147 MPa (1.5 ton / cm 2) in a magnetic field of 1200 kA / m (15 kOe) to obtain a compact. This molded body was heated in vacuum at 950 to 1000 ° C. for 4 hours to obtain a sintered body. Note that the processing step to the pulverization step were performed in a low oxygen atmosphere.

  The obtained sintered body was subjected to an aging treatment in an Ar atmosphere at 500 ° C. for 1 hour to obtain an R—T—Zr—B-based rare earth metal magnet of Example 1.

(Example 2)
An RT-Zr-B rare earth metal magnet of Example 2 was produced in the same manner as in Example 1 except that the Zr content of the alloy raw material was changed to 0.63% by mass.

(Example 3)
A RT-Zr-B rare earth metal magnet of Example 3 was produced in the same manner as in Example 1 except that the Zr content of the alloy raw material was changed to 2.00% by mass.

Example 4
An RT-Zr-B rare earth metal magnet of Example 4 was produced in the same manner as in Example 1 except that the Zr content of the alloy raw material was changed to 1.80% by mass.

(Example 5)
An example was prepared in the same manner as in Example 1 except that an alloy powder having an average particle size of 6 μm was prepared by changing the classification rotation speed of the classifier in the pulverization process, and the sintering process was performed using the alloy powder. 5 RT-Zr-B rare earth metal magnets were obtained.

(Example 6)
An example was prepared in the same manner as in Example 1 except that the classifying rotational speed of the classifier in the pulverizing process was changed to prepare an alloy powder having an average particle diameter of 2 μm and the sintering process was performed using the alloy powder. 6 RT-Zr-B rare earth metal magnets were obtained.

(Example 7)
An example was prepared in the same manner as in Example 1 except that the classifying rotation speed of the classifier in the pulverization process was changed to prepare an alloy powder having an average particle size of 10 μm and the sintering process was performed using the alloy powder. 7 RT-Zr-B rare earth metal magnets were obtained.

(Example 8)
An RT-Zr-B-based rare earth metal magnet of Example 8 was obtained in the same manner as in Example 1 except that the amount of Nd in the alloy raw material was changed to 32% by mass.

Example 9
An example was prepared in the same manner as in Example 8 except that the classifying rotational speed of the classifier in the pulverizing process was changed to prepare an alloy powder having an average particle diameter of 2 μm and the sintering process was performed using the alloy powder. 9 RT-Zr-B rare earth metal magnets were obtained.

(Comparative Example 1)
The RT-Zr-B rare earth metal magnet of Comparative Example 1 was produced in the same manner as in Example 6 except that the Zr content of the alloy raw material was changed to 0.30% by mass.

(Comparative Example 2)
An R—T—Zr—B-based rare earth metal magnet of Comparative Example 2 was produced in the same manner as in Example 1 except that the Zr content of the alloy raw material was changed to 0.30 mass%.

(Comparative Example 3)
An R—T—Zr—B-based rare earth metal magnet of Comparative Example 3 was produced in the same manner as in Example 6 except that the heat treatment after casting the alloy was held at 800 ° C. for 1 hour.

(Comparative Example 4)
An R—T—Zr—B-based rare earth metal magnet of Comparative Example 4 was produced in the same manner as in Example 6 except that the R amount of the alloy raw material was changed to 28% by mass.

(Comparative Example 5)
An R—T—Zr—B-based rare earth metal magnet of Comparative Example 5 was produced in the same manner as in Example 6 except that the Zr content of the alloy raw material was changed to 0.45 mass%.

(Comparative Example 6)
An R—T—Zr—B-based rare earth metal magnet of Comparative Example 6 was produced in the same manner as in Example 6 except that the Zr content of the alloy raw material was changed to 2.40% by mass.

(Comparative Example 7)
The RT-Zr-B rare earth metal magnet of Comparative Example 7 was produced in the same manner as in Example 5 except that the Zr content of the alloy raw material was changed to 0.45 mass%.

(Evaluation of microstructure)
The cross sections of the RTZr-B rare earth metal magnets of Examples and Comparative Examples prepared as described above were observed with a scanning electron microscope (SEM, magnification: 20000 times). On the SEM observation screen, the particle size of particles in a 50 μm × 50 μm field of view was measured, and the average value of the measured values was taken as the crystal particle size of each RTZr-B rare earth metal magnet. The results are shown in Table 1.

(Evaluation of Zr existence state)
According to the TEM-EDS analysis of the R-T-Zr-B rare earth metal magnet, the grain boundary phase is not included from the spectrum of the region containing the R-T-Zr-B rare earth metal magnet crystal grain boundary phase. The spectrum of the region is subtracted, the remainder at the peak position of Zr is considered as a signal from the grain boundary phase, and the differential peak integrated intensity is calculated. On the other hand, by calculating the sum of the peak integrated intensity of Zr in the spectrum of the region not including the grain boundary phase and the peak integrated intensity of Zr in the region including the grain boundary phase, and dividing the difference peak intensity The ratio of Zr present in the grain boundary phase is calculated. The results are shown in Table 1.

(Evaluation of magnetic properties)
Using a B—H tracer, the magnetic properties of the rare earth magnets obtained in each Example and each Comparative Example were measured. The obtained results are shown in Table 1.

  From the results shown in Table 1, the RTZr-B rare earth metal magnets of Examples 1 to 8 have fine crystal particles in the sintered body, and have excellent coercivity in the sintered body. Had. Moreover, it can be seen from these examples that a high coercive force can be obtained regardless of the pulverized particle diameter.

  On the other hand, in Comparative Example 1 and Comparative Example 2, since there was too little Zr for suppressing sintering between the RTB-based rare earth metal magnet crystal particles, the microstructure after HDDR treatment can be retained after sintering. The HcJ was inferior to Examples 1-9. In Comparative Example 3, since the crystallinity of the raw material alloy is low, Zr is incorporated into the R—T—B system rare earth metal magnet crystal particles, and the sintering suppression effect between the R—T—B system rare earth metal magnet crystal particles is reduced. It was considered that the crystal particle size in the sintered body had grown to the same size as the pulverized particle size, and HcJ was also lower than that of the example because it could not be sufficiently exhibited.

  In Comparative Example 4, since the amount of R was small, the thickness of the grain boundary phase between crystal grains of the R—T—Zr—B-based rare earth metal magnet was reduced, resulting in insufficient magnetic separation between the crystal grains. It is thought that HcJ was lowered. In Comparative Example 5, since the amount of Zr is larger than that in Comparative Example 1, the crystal particle diameter in the sintered body is smaller than that in Comparative Example 1, but the crystal grows to the same extent as the pulverized particle diameter, and the high HcJ Is not obtained. Although the details are not clear in Comparative Example 6, it is considered that the magnetic properties deteriorated because the amount of Zr present at the crystal grain boundaries increased. Moreover, in Comparative Example 1 and Comparative Example 2, and Comparative Example 5 and Comparative Example 7, HcJ is lower as the pulverized particle size is larger, and is affected by the pulverized particle size. On the other hand, from Example 1, Example 5, Example 6, and Example 7, high HcJ could be obtained regardless of the pulverized particle diameter.

Claims (2)

R-T-Zr-B ( R is Y, La, Ce, Pr, at least one element Nd, Sm, Eu, selected from, T is at least one transition metal element selected from Fe, Co) based a sintered body of a rare earth metal magnet, the sintered body of rare earth metal magnets 29 wt% to 37 wt% of R, the Zr exceeds 0.5 containing 2 mass%, the main phase crystal size Is 0.1 μm to 0.5 μm, Zr is present in the main phase grain boundary, and the ratio of Zr in the grain boundary phase to the total of the Zr content in the main phase and the Zr content in the grain boundary phase is 60%. The sintered body of an RTZr-B rare earth metal magnet characterized by the above . The sintered body of the RTZ-Rr -based rare earth metal magnet according to claim 1, wherein the pulverized particle diameter of the raw material alloy is 2 to 10 μm.

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