JP2011086830A - R-Fe-B-BASED RARE EARTH SINTERED MAGNET AND METHOD OF PRODUCING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing an R-Fe-B-based rare-earth sintered magnet by which grain boundary diffusion is completed in a shorter period of time than before, the amount of a heavy rare-earth element RH to be vaporized is reduced by shortening the time of the grain boundary diffusion, consequently the grain boundary diffusion of the heavy rare-earth element RH is efficiently carried out, and to provide the R-Fe-B-based rare-earth sintered magnet produced by the method. <P>SOLUTION: An R-Fe-B-based rare-earth sintered magnet body is prepared which contains, as a main phase, an R<SB>2</SB>Fe<SB>14</SB>B type compound crystal grains containing a light rare-earth element RL (at least one of Nd and Pr) as a main rare-earth element R. A pulverized body which contains the heavy rare-earth element RH (at least one selected from among Dy and Tb) and is pulverized by a hydrogen absorption method is disposed in a processing chamber together with the R-Fe-B-based rare-earth sintered magnet body, and heated to diffuse the heavy rare-earth element RH into the R-Fe-B-based rare-earth sintered magnet body while supplying the heavy rare-earth element RH to a surface of the R-Fe-B-based rare-earth sintered magnet body from the pulverized body. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an R—Fe—B based rare earth sintered magnet having R ₂ Fe ₁₄ B type compound crystal grains (R is a rare earth element) as a main phase and a method for producing the same. In particular, the light rare earth element RL (at least one of Nd and Pr) is contained as the main rare earth element R, and at least a part of the light rare earth element RL is selected from the group consisting of heavy rare earth elements RH (Dy, Tb) The present invention relates to an R-Fe-B rare earth sintered magnet substituted by 1 type) and a method for producing the same.

The R-Fe-B rare earth sintered magnet having the R ₂ Fe ₁₄ B-type compound crystal grains as the main phase has excellent magnetic properties, and thus its application is increasingly widespread. Especially in recent years, with the expansion of magnet applications in home appliances, industrial equipment, electric vehicles, and wind power generation in response to environmental problems, the performance of R-Fe-B rare earth sintered magnets has been further improved. It is requested.

  R-Fe-B rare earth sintered magnets are known as the most powerful magnets among permanent magnets. Various motors such as voice coil motors (VCM) for hard disk drives and motors for hybrid vehicles, and home appliances Etc. are used. When the R-Fe-B rare earth sintered magnet is used in each device such as a motor, it is required to have excellent heat resistance and high coercive force characteristics in order to cope with a high temperature use environment.

As a means for improving the coercive force _HcJ of the R-Fe-B rare earth sintered magnet, there is a method of using an alloy prepared by melting a heavy rare earth element RH as a raw material as a magnet material. According to this method, since the rare earth element R of the R ₂ Fe ₁₄ B phase containing the light rare earth element RL as the rare earth element R is replaced by the heavy rare earth element RH, the magnetocrystalline anisotropy of the R ₂ Fe ₁₄ B phase is improves. However, the magnetic moment of the light rare earth element RL in the R ₂ Fe ₁₄ B phase is in the same direction as the magnetic moment of Fe, whereas the magnetic moment of the heavy rare earth element RH is opposite to the magnetic moment of Fe, There is a problem that the residual magnetic flux density Br decreases as the light rare earth element RL is replaced with the heavy rare earth element RH.

  Further, since the rare earth element RH is a rare resource, it is desired to reduce the amount of use. For these reasons, the method of replacing the entire light rare earth element RL with the heavy rare earth element RH is not preferable.

Therefore, as a method for improving the coercive force H _cJ with a relatively small amount of heavy rare earth element RH, Dy etc. is vaporized by sublimation from a bulk body containing heavy rare earth element RH, and R-Fe-B rare earth sintered magnet body. A manufacturing method for diffusing from the surface to the grain boundary has been proposed (see, for example, Patent Document 1). In this method, first, an R—Fe—B rare earth sintered magnet having R ₂ Fe ₁₄ B type compound crystal grains containing a light rare earth element RL (at least one of Nd and Pr) as a main rare earth element R as a main phase. A body (hereinafter simply referred to as a “magnet body” if necessary) is prepared. Furthermore, a bulk body containing a heavy rare earth element RH (at least one selected from the group consisting of Dy, Ho, and Tb) is disposed in the processing chamber together with the magnet body, and the processing chamber is set to 700 ° C. or higher and 1000 ° C. or lower. Heat. Through the above steps, the heavy rare earth element RH is diffused into the magnet body while supplying the heavy rare earth element RH from the bulk body to the surface of the magnet body.

In the above manufacturing method, the heavy rare earth element RH is present in the vicinity of the grain boundary of the R ₂ Fe ₁₄ B phase in order to preferentially generate grain boundary diffusion into the grain boundary phase rather than intragranular diffusion into the main phase grains. Many are distributed. Therefore, it is possible to efficiently improve the magnetocrystalline anisotropy of the R ₂ Fe ₁₄ B phase in the main phase outer shell near the grain boundary.

The coercive force generation mechanism of R-Fe-B rare earth sintered magnets is the nucleation type (nucleation type), so that a large amount of heavy rare earth elements RH are distributed in the outer shell of the main phase. Magnetic anisotropy is increased and nucleation of reverse magnetic domains is prevented. As a result, the coercive force H _cJ is improved. In addition, since the substitution with the heavy rare earth element RH does not occur at the center of the crystal grains that do not contribute to the improvement of the coercive force _HcJ, it is possible to suppress the decrease in the residual magnetic flux density Br.

Japanese Patent No. 4241900

  However, in the method for producing an R—Fe—B rare earth sintered magnet described in Patent Document 1, since the heavy rare earth element RH is vaporized from the bulk body, the heavy rare earth element RH is hardly vaporized, and a predetermined grain boundary diffusion treatment is performed. There was a problem of spending a long time to complete.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to perform grain boundary diffusion treatment in a form that facilitates vaporization of the heavy rare earth element RH, thereby enabling grain boundary diffusion in a shorter time than conventional. R-Fe-B rare earth sintering that diffuses heavy rare earth elements RH efficiently by reducing the amount of heavy rare earth elements RH to be vaporized by completing the grain boundary diffusion treatment in a short time A magnet manufacturing method and an R-Fe-B rare earth sintered magnet manufactured by the manufacturing method are provided.

The method for producing an R—Fe—B rare earth sintered magnet according to claim 1 of the present invention includes:
In addition to preparing an R-Fe-B rare earth sintered magnet body containing R ₂ Fe ₁₄ B type compound crystal grains containing light rare earth elements RL (at least one of Nd and Pr) as the main rare earth element R ,
A pulverized material containing a heavy rare earth element RH (at least one selected from Dy and Tb) and pulverized by a hydrogen storage method is placed in a processing chamber together with the R-Fe-B rare earth sintered magnet body. Heating
While supplying the heavy rare earth element RH from the pulverized product to the surface of the R-Fe-B rare earth sintered magnet body, the heavy rare earth element RH is diffused inside the R-Fe-B rare earth sintered magnet body. This is a method for producing an R—Fe—B rare earth sintered magnet.

The R-Fe-B rare earth sintered magnet according to claim 2 is:
Manufactured by the manufacturing method according to claim 1,
R ₂ Fe ₁₄ B type compound crystal grains containing a light rare earth element RL (at least one of Nd and Pr) as a main rare earth element R as a main phase,
This is an R—Fe—B rare earth sintered magnet containing a heavy rare earth element RH (at least one selected from Dy, Ho, Tb).

  According to the present invention, the RH hydride is used as the heavy rare earth element RH supply material on the surface of the R-Fe-B rare earth sintered magnet body, so that RH can be vaporized compared to the bulk body of RH to be pulverized. It can be easily generated. Accordingly, the predetermined grain boundary diffusion process can be completed in a shorter time because vaporization is easier.

  In addition, since the grain boundary diffusion process can be completed in a shorter time, the amount of RH vaporized from the RH supply material can be suppressed, so that it is more RH than the grain boundary diffusion process in the RH bulk body. Can be reduced.

The R-Fe-B rare earth sintered magnet of the present invention is a surface of a sintered R-Fe-B rare earth sintered magnet body (hereinafter simply referred to as “magnet body” as necessary). It contains heavy rare earth element RH introduced inside by grain boundary diffusion. Here, the heavy rare earth element RH is at least one selected from Dy and Tb. The magnet body has R ₂ Fe ₁₄ B type compound crystal grains containing a light rare earth element RL (at least one of Nd and Pr) as a main rare earth element R as a main phase.

  As raw materials for the R-Fe-B rare earth sintered magnet of the present invention, the light rare earth element RL of 25 wt% to 40 wt% as the main rare earth element R, B (boron) of 0.6 wt% to 1.6 wt%, An alloy containing the remaining Fe and inevitably mixed impurities is prepared. Part of B may be substituted by C (carbon), O (oxygen), and N (nitrogen), and part of Fe is substituted by other transition metal elements (for example, Co or Ni). Also good. The alloys are Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb, and Bi for various purposes. About 0.01 to 1.0 wt% of at least one additive element M selected from the group consisting of

  The above alloy is produced by quenching a molten raw material alloy by, for example, a strip casting method.

  In the production method of the present invention, a bulk body containing the heavy rare earth element RH is pulverized by a hydrogen storage method to form a pulverized product (hereinafter, this pulverized product is referred to as “RH hydride” if necessary), The RH hydride and the magnet body are heated in a temperature range of 1000 ° C. or less. By using the pulverized RH hydride, vaporization (sublimation) of the heavy rare earth element RH is more easily promoted than the bulk body. Furthermore, by setting the temperature range to 1000 ° C or less, the growth rate of the RH film on the surface of the magnet body is suppressed to such an extent that it does not become extremely higher than the diffusion rate of RH inside the magnet, while flying to the surface of the magnet body. The heavy rare earth element RH is quickly diffused into the magnet body. The temperature range of 1000 ° C. or lower is a temperature at which the vaporization of the heavy rare earth element RH hardly occurs, but is also a temperature at which the rare earth element is actively diffused in the R—Fe—B rare earth sintered magnet. For this reason, it is possible to promote the diffusion of grain boundaries into the magnet body preferentially rather than the heavy rare earth element RH flying on the magnet body surface forming an RH film on the magnet body surface.

In the present invention, supplying the rare earth element RH from the RH hydride to the surface of the magnet body and diffusing the heavy rare earth element RH from the surface of the magnet body to the inside may be simply referred to as “evaporation diffusion”. According to the present invention, the heavy rare earth element RH diffuses into the magnet body at a rate higher than the rate at which the heavy rare earth element RH diffuses into the main phase located near the surface of the magnet body. It penetrates. In the present invention, “grain boundary diffusion” occurs preferentially over “intragranular diffusion” even in the surface layer region of the magnet body, suppressing the decrease in residual magnetic flux density Br and effectively improving the coercive force H _cJ. It becomes possible to make it.

Since the coercive force generation mechanism of R-Fe-B rare earth sintered magnets is a nucleation type, if the magnetocrystalline anisotropy in the main phase outer shell is increased, the reverse magnetic domain is near the grain boundary phase in the main phase. Nucleation is suppressed. As a result, the coercive force H _{cJ of the} entire main phase is improved.

Furthermore, since the heavy rare earth substitution layer can be formed in the outer shell of the main phase not only in the region close to the surface of the magnet body but also in the region deep from the surface of the magnet body, the magnetocrystalline anisotropy is enhanced throughout the magnet, The coercive force H _cJ is improved while suppressing a decrease in the overall residual magnetic flux density Br.

  Furthermore, since the heavy rare earth element RH supply material on the surface of the magnet body is pulverized by using RH hydride, RH vaporization can be easily generated as compared with a bulk body of RH. Accordingly, the predetermined grain boundary diffusion process can be completed in a shorter time because vaporization is easier.

  In addition, since the grain boundary diffusion process can be completed in a shorter time, the amount of RH vaporized from the RH supply material can be suppressed, so it is more RH than the grain boundary diffusion process in the RH bulk body. Can be reduced.

As the heavy rare earth element RH to be replaced with the light rare earth element RL in the outer shell of the main phase, Dy is most preferable in consideration of easiness of vapor deposition diffusion, cost, and the like. However, the crystal magnetic anisotropy of Tb ₂ Fe ₁₄ B is higher than the crystal magnetic anisotropy of Dy ₂ Fe ₁₄ B, and is about three times the crystal magnetic anisotropy of Nd ₂ Fe ₁₄ B. Therefore, when Tb is vapor-deposited and diffused, the characteristics of the magnet body can be improved most efficiently (coercivity H _cJ can be improved without lowering the residual magnetic flux density Br).

  The bulk body containing the heavy rare earth element RH is pulverized by the hydrogen storage method as follows. First, a heavy rare earth element RH (at least one selected from Dy and Tb) is contained, and a predetermined amount of the RH bulk body is accommodated in a hydrogen furnace that is a sealed container. Next, the inside of the hydrogen furnace is evacuated and depressurized through the evacuation means until a predetermined pressure is reached. After confirming that the inside of the hydrogen furnace has reached the specified pressure, hydrogen is introduced into the hydrogen furnace, the temperature of the hydrogen furnace is increased by heating the hydrogen furnace, and hydrogen storage into the RH bulk body is started. .

  Due to hydrogen embrittlement by the hydrogen storage method, the RH bulk body is crushed to form RH hydrides, and RH hydrides are prepared.

Next, a preferred example of the grain boundary diffusion treatment according to the present invention will be described with reference to FIG. FIG. 1 shows an arrangement example of the magnet body 1 and the RH hydride 2. In the example shown in FIG. 1, the magnet body 1 and the RH hydride 2 are disposed to face each other with a predetermined interval inside the processing chamber 3 made of a refractory metal material. As magnet body 1, an R—Fe—B based rare earth sintered magnet having R ₂ Fe ₁₄ B type compound crystal grains containing light rare earth element RL (at least one of Nd and Pr) as main rare earth element R as a main phase. Prepare your body. The processing chamber 3 in FIG. 1 includes a member that holds a plurality of magnet bodies 1. In the example of FIG. 1, the magnet body 1 and the lower RH hydride 2 are held by a net 4 made of Nb. The configuration for holding the magnet body 1 and the RH hydride 2 is not limited to the above example and is arbitrary. The arrangement relationship between the magnet body 1 and the RH hydride 2 may be an arrangement in which the magnet body 1 and the RH hydride 2 move up and down, left and right, or move relative to each other. However, the structure which interrupts | blocks between the magnet body 1 and RH hydride 2 should not be employ | adopted. The “opposite” in the present application means that the magnet body 1 and the RH hydride 2 face each other without being interrupted. Further, the “facing arrangement” is not limited to the meaning that the main surfaces are arranged so as to be parallel to each other.

  After the magnet body 1 and the RH hydride 2 are arranged as shown in FIG. 1, the processing chamber is evacuated and decompressed until reaching a predetermined pressure via a vacuum exhaust means (not shown), and when the processing chamber reaches a predetermined pressure, the processing chamber is illustrated. The temperature of the processing chamber 3 is raised by heating the processing chamber 3 with a heating device that does not. At this time, the temperature of the processing chamber 3 is raised stepwise and held at a predetermined temperature for a certain time. Thereby, dehydrogenation processing of RH hydride 2 is performed. The set temperature in the processing chamber 3 under reduced pressure is adjusted to a range of 1000 ° C. or lower. When the temperature in the processing chamber 3 reaches the start temperature of the grain boundary diffusion process in this way, the RH bulk body 2 is heated to substantially the same temperature as the processing chamber 3 and starts to vaporize. RH steam atmosphere is formed.

  In the above temperature range of 1000 ° C. or less, the vapor pressure of the heavy rare earth element RH is slight and hardly vaporizes. However, in the present invention, the vaporization of the heavy rare earth element RH is promoted as compared with the RH bulk body by finely crushing the RH bulk body by the hydrogen storage method to increase the surface area. Therefore, it is possible to deposit heavy rare earth metal RH on the surface of the magnet body 1 by arranging the magnet body 1 and the RH hydride 2 in close proximity to each other, and the temperature of the magnet body 1 can be set to RH. By adjusting the temperature within the appropriate temperature range (1000 ° C. or lower) to be equal to or higher than the temperature of the hydride 2, the heavy rare earth metal RH deposited from the gas phase is diffused deeply into the magnet body 1 as it is. obtain. The temperature range of 1000 ° C. or less is a preferable temperature range in which the heavy rare earth element RH diffuses into the interior through the grain boundary phase of the magnet body 1, and the slow precipitation of the heavy rare earth element RH and the rapid inside the magnet body Diffusion is performed efficiently.

  Further, the predetermined grain boundary diffusion process can be completed in a shorter time because vaporization is likely to occur. In addition, since the amount of RH vaporization from the RH supply can be reduced as the grain boundary diffusion treatment time is shortened, the amount of RH used is further reduced compared to the grain boundary diffusion treatment in the RH bulk material. It becomes possible.

The RH metal flying and depositing on the surface of the magnet body diffuses in the grain boundary phase toward the inside of the magnet body using the difference between the heat of the atmosphere and the RH concentration at the interface of the magnet body as a driving force. At this time, a part of the light rare earth element RL in the R ₂ Fe ₁₄ B phase is replaced by the heavy rare earth element RH diffused and penetrated from the surface of the magnet body. As a result, a layer enriched with heavy rare earth elements RH is formed in the main phase outer shell of the R ₂ Fe ₁₄ B phase.

By forming such an RH enriched layer, the magnetocrystalline anisotropy of the main phase outer shell is increased, and the coercive force H _cJ is improved. That is, by using a small amount of the heavy rare earth element RH, the heavy rare earth element RH is diffused and penetrated deep inside the magnet body, and an RH concentrated layer is efficiently formed in the outer shell of the main phase. It is possible to improve the coercive force H _cJ over the entire magnet body while suppressing the decrease.

  Furthermore, in the present invention, a special process or apparatus for vaporizing RH, which is a vapor deposition material, is not required, and RH metal can be deposited on the surface of the magnet body by pulverizing the RH bulk body by a hydrogen storage method. . The “processing chamber” in this specification includes a wide space in which the magnet body 1 and the RH hydride 2 are arranged, and may mean a processing chamber of a heat treatment furnace. It may also mean a processing container to be accommodated.

  The shape and size of the RH hydride is not particularly limited, and may be used as it is after being pulverized by the hydrogen storage method. The RH hydride is preferably formed from an RH metal or an alloy containing RH containing at least one heavy rare earth element RH. The RH hydride does not need to be composed of one kind of element, but the heavy rare earth element RH and the element X (X is Y, Gd, Tb, Ho, Er, Nd, Pr, La, Ce, Al , Zn, Sn, Cu, Co, Fe, Ag, Ca, Mg, and In may be included.

  In the present invention, the vaporization amount of the heavy rare earth element RH is small, but since the magnet body 1 and the RH hydride 2 are disposed in a non-contact and close distance, the vaporized heavy rare earth element RH is present on the surface of the magnet body 1. It deposits efficiently, and there is little adhesion to the wall surface etc. in the processing chamber 3. Furthermore, if the wall surface in the processing chamber 3 is made of a material that does not react with the heavy rare earth element RH, such as a heat-resistant alloy such as Nb or ceramics, the heavy rare earth element RH attached to the wall surface is vaporized again, and finally Deposited on the surface of the magnet body 1. For this reason, useless consumption of the heavy rare earth element RH which is a valuable resource can be suppressed.

  In the processing temperature range (1000 ° C. or less) of the grain boundary diffusion process performed in the present invention, the RH hydride 2 is not melt-softened, and the heavy rare earth element RH is vaporized from the surface thereof. The external appearance of 2 does not change greatly and can be used repeatedly.

  Furthermore, since the RH hydride 2 and the magnet body 1 are arranged close to each other, the amount of the magnet body 1 that can be mounted in the processing chamber 3 having the same volume can be increased, and the loading efficiency is high. Moreover, since a large-scale apparatus is not required, a general vacuum heat treatment furnace can be used, and an increase in manufacturing cost can be avoided, which is practical.

  The surface state of the magnet body is preferably closer to a metal state so that the heavy rare earth element RH can easily diffuse and penetrate, and it is better to perform an activation treatment such as acid cleaning or blasting in advance. However, in the present invention, when the heavy rare earth element RH is vaporized and deposited on the surface of the magnet body in an active state, it diffuses into the interior of the magnet body at a higher rate than the formation of a solid layer. For this reason, the surface of the magnet body may be in a state in which oxidation has progressed, for example, after the sintering process or after the cutting process is completed.

  Note that the grain boundary diffusion step in the present invention is not sensitive to the surface condition of the magnet body, and a film made of Al, Zn, or Sn may be formed on the surface of the magnet body before the diffusion step. This is because Al, Zn, and Sn are low-melting-point metals, and if they are in a small amount, they do not deteriorate the magnet characteristics and do not hinder the above-mentioned grain boundary diffusion. Elements such as Al, Zn, and Sn may be included in the RH hydride.

  Next, after performing the grain boundary diffusion treatment for a predetermined time, the operation of the heating means (not shown) is stopped, the inert gas is introduced through the gas introduction means (not shown), and the vaporization from the RH hydride 2 is stopped. Let Then, once the temperature in the processing chamber 3 is lowered, the introduction of the inert gas is stopped and evacuation is performed, and the heating means is operated again as necessary to change the temperature in the processing chamber 3 to 450 ° C. to 700 ° C. Heat treatment (aging treatment) for further improving or recovering the coercive force may be applied by setting in the range of ° C. When the aging treatment is performed, finally, the treatment chamber 3 is cooled and the magnet body 1 is taken out from the treatment chamber 3.

  The inside of the processing chamber 3 during the heat treatment is preferably an inert atmosphere. The “inert atmosphere” in this specification includes a vacuum or a state filled with an inert gas. The “inert gas” is a rare gas such as argon (Ar), for example. It is included in “gas”. The pressure of the inert gas is reduced to show a value lower than the atmospheric pressure.

  Practically, it is preferable to subject the magnet body after vapor diffusion to surface treatment. The surface treatment may be a known surface treatment, and for example, a surface treatment such as Al vapor deposition, electric Ni plating, or resin coating can be performed. Prior to the surface treatment, a known pretreatment such as sandblasting, barrel treatment, etching treatment or mechanical grinding may be performed. Moreover, you may perform the grinding for dimension adjustment after a grain boundary diffusion process.

  Hereinafter, preferred embodiments of the method for producing an R—Fe—B rare earth sintered magnet according to the present invention will be described.

<Example 1>
First, an alloy containing 30.11 wt% of light rare earth elements RL (Nd and Pr), 0.99 wt% of B as the main rare earth element R, the balance Fe and inevitable impurities is prepared. A part of B may be substituted by C, O, N, and a part of Fe may be substituted by other transition metal elements (for example, Co or Ni). This alloy can be used for various purposes, such as Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb, and About 0.30 to 0.32 wt% of at least one additive element M selected from the group consisting of Bi may be contained.

  The above alloy is produced by rapidly cooling a molten raw material alloy by, for example, a strip casting method. The alloy cast slab produced in the flake shape by the above-mentioned strip casting method is roughly pulverized to about 0.1 mm to several mm (average particle size of 500 μm or less) by hydrogen embrittlement treatment by hydrogen storage method, and after dehydrogenation treatment, jet Using a mill device, an attritor device, or a ball mill device, the powder is finely pulverized to a powder of about 0.1 to 20 μm (preferably 2 to 5 μm). In fine pulverization, a lubricant such as zinc stearate may be used as a pulverization aid.

  Next, the magnetic powder produced by the above-described method is molded in an orientation magnetic field using a press device (vertical magnetic field molding machine, lateral magnetic field molding machine, RIP method, etc.). The strength of the magnetic field to be applied is, for example, 1.5 to 5.5 Tesla (T) depending on the press device. The molding pressure is set so that the density of the molded body is, for example, about 2.5 to 4.5 g / cm 3. Furthermore, it sinters at 1000-1200 degreeC with respect to the obtained powder compact. In addition, since it is possible to perform a vapor deposition diffusion process even if the surface of a sintered magnet body is oxidized, you may grind after a sintering process.

Next, an RH bulk body containing RH (Dy) and having a purity of 99.9% is prepared, and the bulk body is housed inside a hydrogen furnace that is a sealed container. Next, the inside of the hydrogen furnace is evacuated and reduced in pressure until it reaches 1.3 × 10 ⁻³ Pa through the vacuum exhaust means. After confirming that the inside of the hydrogen furnace has reached the specified pressure, 1 atm (101,325 Pa) of hydrogen is introduced into the hydrogen furnace, and the temperature of the hydrogen furnace is increased to 280 ° C. by heating the hydrogen furnace with a heating device. Start storing hydrogen in the bulk.

  The RH bulk body and RH hydride need not be composed of one kind of element, but the heavy rare earth element RH and element X (Y, Gd, Tb, Ho, Er, Nd, Pr, La, Ce, It may contain an alloy of at least one selected from the group consisting of Al, Zn, Sn, Cu, Co, Fe, Ag, Ca, Mg, and In.

  Due to hydrogen embrittlement by the hydrogen storage method, the RH bulk body is crushed to form RH hydrides, and RH hydrides are prepared.

Next, as shown in FIG. 1, the produced magnet body 1 and the RH hydride 2 are disposed opposite to each other inside the processing chamber 3, and the pressure is reduced by vacuuming until a predetermined pressure of 1.3 × 10 ⁻³ Pa is reached. When the predetermined pressure is reached, the processing chamber 3 is heated with a heating device, and the temperature of the processing chamber 3 is increased stepwise (in this embodiment, 200 ° C., 300 ° C., 400 ° C., 500 ° C., 900 ° C.) and dehydrated. While performing the raw treatment, hold for a certain time (6 hours) and perform the grain boundary diffusion treatment.

  After the grain boundary diffusion treatment, the operation of the heating means is stopped, an inert gas (Ar) is introduced through a gas introduction means (not shown) (for example, 1 atm = 101,325 Pa), and RH from the RH hydride 2 is introduced. Stop vaporization. Then, the introduction of the inert gas is stopped and evacuation is performed.

Magnet characteristics (residual magnetic flux) of the R-Fe-B rare earth sintered magnet sample subjected to the grain boundary diffusion treatment as described above and the R-Fe-B rare earth sintered magnet sample before the grain boundary diffusion treatment. Density: Br, coercivity: H _cB , H _cJ , maximum energy product: (BH) max) were measured with a BH tracer. Table 1 shows the characteristics obtained by the measurement. Also, the graph of Br and H _cJ in the R-Fe-B rare earth sintered magnet sample before the grain boundary diffusion treatment is shown in Fig. 2, and the R-Fe-B rare earth sintered magnet subjected to the grain boundary diffusion treatment. The graph of Br and _{HcJ in} the sample is shown in FIG.

As can be seen from the comparison of the graphs in FIG. 2 and FIG. 3, an improvement in the coercive force H _cJ of about 2.9 (kOe) was confirmed for the magnet sample after the grain boundary diffusion treatment. This is because a Dy concentrated layer having a high anisotropic magnetic field was formed in the outer shell of the main phase (Nd ₂ Fe ₁₄ B type compound crystal) by RH diffusion into the magnet body.

Explanatory drawing which shows typically an example of the structure of the processing container used for the manufacturing method of the R-Fe-B rare earth sintered magnet by this invention, and the arrangement | positioning relationship between RH hydride and a magnet body in a processing container. The Br-H _cJ graph in the R-Fe-B rare earth sintered magnet sample before the grain boundary diffusion treatment. The Br-H _cJ graph in the R-Fe-B system rare earth sintered magnet sample which performed grain boundary diffusion processing concerning the present invention.

1 Magnet body 2 RH hydride 3 Processing chamber 4 Net

Claims (2)

In addition to preparing an R-Fe-B rare earth sintered magnet body containing R ₂ Fe ₁₄ B type compound crystal grains containing light rare earth elements RL (at least one of Nd and Pr) as the main rare earth element R ,
A pulverized material containing a heavy rare earth element RH (at least one selected from Dy and Tb) and pulverized by a hydrogen storage method is placed in a processing chamber together with the R-Fe-B rare earth sintered magnet body. Heating
While supplying the heavy rare earth element RH from the pulverized product to the surface of the R-Fe-B rare earth sintered magnet body, the heavy rare earth element RH is diffused inside the R-Fe-B rare earth sintered magnet body. Method for producing R-Fe-B rare earth sintered magnets. Manufactured by the manufacturing method according to claim 1,
R ₂ Fe ₁₄ B type compound crystal grains containing a light rare earth element RL (at least one of Nd and Pr) as a main rare earth element R as a main phase,
An R-Fe-B rare earth sintered magnet containing a heavy rare earth element RH (at least one selected from Dy and Tb).