JP6003452B2 - Rare earth magnet manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a rare earth magnet.

  Rare earth magnets using rare earth elements such as lanthanoids are also called permanent magnets, and their uses are used in motors for driving hard disks and MRI, as well as drive motors for hybrid vehicles and electric vehicles.

  Residual magnetization (residual magnetic flux density) and coercive force can be cited as indicators of the magnet performance of this rare earth magnet. However, in response to increased heat generation due to miniaturization of motors and higher current density, rare earth magnets used also The demand for heat resistance is further increasing, and how to maintain the coercive force of a magnet under high temperature use is one of the important research subjects in the technical field. Taking Nd-Fe-B magnets, one of the rare-earth magnets frequently used in vehicle drive motors, to refine crystal grains, use a composition alloy with a large amount of Nd, Attempts have been made to increase the coercivity by adding heavy rare earth elements such as high Dy and Tb.

  Of the heavy rare earth elements that increase coercive force performance, Dy, which is used in large quantities, is taken up by the fact that Dy's reserves are unevenly distributed in China, as well as the production and export volume of rare metals such as Dy by China. The price of Dy's resources has risen sharply since the beginning of 2011. Therefore, the development of Dy-less magnets that guarantee coercive force performance while reducing the amount of Dy and Dy-free magnets that guarantee coercive force performance without using any Dy is one of the important development issues raised by the nation in Japan. It has become.

  An outline of an example of a method for producing a rare earth magnet is as follows. For example, a fine powder obtained by rapid solidification of a Nd-Fe-B metal melt is formed into a compact while being pressed, and the magnetic anisotropy is applied to the compact. Of rare earth magnet precursor (orientation magnet) by performing hot plastic working to impart a rare earth magnet, and a rare earth magnet is manufactured by diffusing and infiltrating a modified alloy that increases the coercive force of the rare earth magnet precursor. Is generally applied.

  Here, Patent Documents 1 and 2 disclose a method of manufacturing a rare earth magnet made of a nanocrystalline magnet by applying a heavy rare earth element having high coercive force performance by various methods.

  The manufacturing method disclosed in Patent Document 1 is a manufacturing method in which an evaporated material containing at least one of Dy and Tb is evaporated from a molded body that has been subjected to hot plastic working, and grain boundaries are diffused from the surface of the molded body.

  This manufacturing method requires a high-temperature treatment of about 850 to 1050 ° C. in the process of evaporating the evaporation material, and this temperature range is specified from the improvement of the residual magnetic flux density and the suppression of crystal grain growth. It is assumed.

  However, when heat treatment is performed in a temperature range of about 850 to 1050 ° C., the crystal grains become coarse, and as a result, the coercive force is likely to be reduced. That is, while Dy and Tb are diffused at the grain boundaries, the coercive force cannot be sufficiently increased as a result.

  On the other hand, in Patent Document 2, at least one element of Dy, Tb, and Ho, or these and at least one of Cu, Al, Ga, Ge, Sn, In, Si, P, and Co is formed on the surface of the rare earth magnet. A manufacturing method is disclosed in which an alloy of elements is brought into contact and subjected to heat treatment so that the crystal grain size does not exceed 1 μm to diffuse grain boundaries.

  Here, in patent document 2, when the temperature at the time of heat processing is the range of 500-800 degreeC, it is excellent in the balance of the diffusion effect to the grain boundary phase, such as Dy, and the coarsening suppression effect of the crystal grain by heat processing, and high maintenance. It is said that it will be easier to obtain magnetic rare earth magnets. The various examples disclosed are heat-treated at 500 to 900 ° C. using a Dy-Cu alloy. Among various examples, the melting point of a typical 85Dy-15Cu alloy is 1100 ° C. Therefore, when trying to diffuse and infiltrate this molten metal, high temperature treatment of about 1000 ° C. or higher is required, and as a result, coarsening of crystal grains cannot be suppressed.

  In view of these various situations (Dy, etc., rising prices, coarsening of crystal grains in a high temperature atmosphere when a modified alloy containing a high melting point heavy rare earth element is diffused into the grain boundary phase, etc.) By using a modified alloy (modified phase) that does not use heavy rare earth metals such as Tb, the coercive force of rare earth magnets, particularly high-temperature atmospheres, is achieved by diffusing and infiltrating the melt of the modified alloy under relatively low temperature conditions. A proposal of a method for producing a rare earth magnet having a high coercivity below is desired.

  Therefore, in Patent Document 3, an alloy powder composed of a light rare earth element such as Y or Sc and a transition element such as Fe or Cu is present on the surface of a sintered body that is a rare earth magnet precursor, and this is vacuum or inert gas. A method for producing a rare earth magnet is disclosed in which an alloy powder is diffused into the sintered body by heating in an atmosphere at a temperature lower than the sintering temperature of the sintered body.

  According to the manufacturing method disclosed in Patent Document 3, since the alloy powder diffused into the sintered body does not contain heavy rare earth elements, the temperature during internal diffusion can be lowered. However, when the internal diffusion of the alloy powder is performed in a vacuum atmosphere, there is a problem that the equipment cost is high because an equipment (vacuum furnace) capable of forming a vacuum atmosphere is required. In addition, since such a vacuum furnace generally performs heat treatment at 1000 ° C. or higher, it becomes overspecial for diffusing and infiltrating the modified alloy into the compact at a relatively low temperature of about 700 ° C. or lower. On the other hand, for example, when the internal diffusion of the alloy powder is performed in an inert gas atmosphere using inexpensive nitrogen gas, it has been found that the diffusion and penetration of the alloy powder is not sufficiently performed.

JP 2011-035001 A JP 2010-114200 A JP 2011-014668 A

  The present invention has been made in view of the above-mentioned problems, and does not use heavy rare earth metals such as Dy and Tb, and has a lower coercive force (particularly, a coercive force in a high temperature atmosphere) than a conventional method for producing rare earth magnets. It is possible to diffuse and infiltrate the modified alloy that increases the magnetic force), and furthermore, it is possible to carry out sufficient diffusion and penetration of the modified alloy in an inert gas atmosphere, thereby reducing the material cost and reducing the equipment cost. An object of the present invention is to provide a manufacturing method capable of manufacturing a rare earth magnet having a high coercive force while reducing the manufacturing cost based on the above.

  In order to achieve the above object, a method for producing a rare earth magnet according to the present invention includes a RE-Fe-B main phase (at least one of RE: Nd and Pr) and a RE-X alloy (X : Metallic element) A reformed alloy made of RE-Y alloy (Y: metal element but not heavy rare earth element) is contacted with the compact of the metallographic structure composed of the grain boundary phase, and the heat-treated modified alloy In the method of manufacturing a rare earth magnet by diffusing and infiltrating a molten metal into a molded body, the heat treatment is performed at a temperature higher than the melting temperature of the RE-Y alloy exceeding 400 ° C. in an inert gas atmosphere. In this temperature rising process, the temperature range of 260 to 400 ° C. is adjusted to less than 120 seconds.

  The method for producing a rare earth magnet of the present invention uses an expensive apparatus for diffusion penetration of this modified alloy when a rare earth magnet is produced by diffusing and infiltrating a modified alloy containing no heavy rare earth elements such as Dy and Tb into the compact. It is a manufacturing method that can guarantee sufficient diffusion and penetration of the modified alloy while being carried out in an inert gas atmosphere instead of the required vacuum atmosphere.

  According to the present inventors, the reason why the modified alloy cannot sufficiently diffuse and penetrate in an inert gas atmosphere is as follows: RE-Y alloy (RE: Nd, etc., Y: a metal element and no heavy rare earth element) It has been specified that Nd or the like reacts with moisture in the inert gas to form a hydroxide when the modified alloy is heated to inhibit diffusion and penetration of the modified alloy.

  And it is specified that the temperature range in which this hydroxylation reaction occurs is a temperature range of 260 to 400 ° C. which is lower than the temperature range in which the modified alloy diffuses and penetrates.

  That is, a temperature of 260 to 400 ° C. at which a hydroxylation reaction occurs in the process of raising the temperature to a melting temperature of the RE-Y alloy exceeding 400 ° C. in a state where the reformed alloy is in contact with the compact in an inert gas atmosphere. Will pass the range.

  Therefore, by heating the reforming alloy and controlling the temperature rise so that it quickly passes through the above temperature range where a hydroxylation reaction occurs in the process of raising the temperature, Nd and the like undergo a hydroxylation reaction in the temperature raising process. Therefore, when the temperature is raised to the diffusion penetration temperature of the modified alloy, the modified alloy can be sufficiently diffused and penetrated into the molded body.

  Note that the temperature at which the modified alloy diffuses and penetrates, that is, the melting temperature of the modified alloy is at least 400 ° C. or higher, and therefore the hydroxylation reaction of the modified alloy does not occur when the melting temperature is reached.

  Here, when passing through the temperature range of 260 to 400 ° C. quickly, the hydroxylation reaction starts to progress in 120 seconds, so the hydroxylation reaction is adjusted by adjusting this temperature range to less than 120 seconds. It is possible to raise the temperature to the diffusion permeation temperature of the modified alloy without causing it.

  By the way, the rare earth magnets to be manufactured by the manufacturing method of the present invention include not only nanocrystalline magnets having a grain size of the main phase (crystal grains) constituting the structure of about 200 nm or less, but also those having a grain size of 300 nm or more. In addition, a sintered magnet having a grain size of 1 μm or more and a bonded magnet in which crystal grains are bonded with a resin binder are included. Among them, a grain boundary is formed by a modified alloy having a relatively low melting point of 700 ° C. or less. Phase reforming is performed, so that coarsening of crystal grains does not become a problem, and coarsening of crystal grains is a problem in conventional manufacturing methods using modified alloys containing heavy rare earth metals with a high melting point. It is suitable for the nanocrystalline magnet that has been formed.

  First, a quenching ribbon (quenching ribbon), which is a fine crystal grain, is manufactured by liquid quenching, and this is coarsely pulverized to produce magnetic powder for rare earth magnets. This magnetic powder is filled into, for example, a die and punched. Sintering while pressurizing at the same time, the bulk of the RE-Fe-B system of nanocrystal structure (RE: at least one of Nd, Pr, more specifically Nd, Pr, Nd-Pr Any isotropic or two or more types) and a grain boundary phase of the RE-X alloy (X: metal element) around the main phase are obtained.

  In this molded body, the RE-X alloy constituting the grain boundary phase differs depending on the main phase component, but when RE is Nd, at least one or more of Nd and Co, Fe, Ga, etc. For example, Nd-Co, Nd-Fe, Nd-Ga, Nd-Co-Fe, Nd-Co-Fe-Ga, or a mixture of two or more of these And it is Nd rich. When RE is Pr, the state is Pr-rich like Nd.

  Next, a reformed alloy made of a RE-Y alloy (Y: a metal element and not containing a heavy rare earth element) is brought into contact with the compact and heat-treated at a temperature equal to or higher than the melting point of the reformed alloy, and the melt By diffusing and penetrating from the surface of the molded body, the RE-Y alloy melt is sucked into the grain boundary phase, and a rare earth magnet having an increased coercive force while causing a structural change inside the molded body is manufactured. Note that when the modified alloy is brought into contact with the molded body, a chip or lump having a desired shape and size processed into the modified alloy can be brought into contact with the molded body.

  With respect to this heat treatment, the production method of the present invention is performed by raising the temperature to a melting temperature of the RE-Y alloy exceeding 400 ° C. in an inert gas atmosphere. By adjusting the range to less than 120 seconds, it is possible to suppress the formation of hydroxides such as Nd constituting the modified alloy during the temperature rising process.

  Before the modified alloy is diffused and infiltrated into the molded body, a rare earth magnet precursor is manufactured by applying anisotropy hot plastic working, and the modified alloy is diffused and infiltrated into the rare earth magnet precursor. Thus, it is possible to produce a rare earth magnet that is further excellent in coercive force performance.

  Here, as the modified alloy, it is preferable to use any one of Nd—Cu alloy, Nd—Al alloy, Pr—Cu alloy, and Pr—Al alloy.

  Nd-Cu alloy has a melting point of about 520 ° C, Pr-Cu alloy has a melting point of about 480 ° C, Nd-Al alloy has a melting point of about 640 ° C, and Pr-Al alloy has a melting point of about 650 ° C. It is far below 700 ° C-1000 ° C, which indicates the coarsening of crystal grains constituting the magnet. Therefore, in order to produce rare earth magnets using these modified alloys, it is only necessary to perform heat treatment of the modified alloy in the range of the molten metal of the modified alloy from the minimum melting point of 480 ° C. to the maximum melting point of 650 ° C. .

When performing this heat treatment in an inert gas atmosphere, N ₂ , Ar, He, etc. are generally used as the inert gas atmosphere, but an N ₂ atmosphere furnace using the most versatile N ₂ gas is used. By using it, the equipment cost can be reduced.

  As can be understood from the above explanation, according to the method for producing a rare earth magnet of the present invention, a modified alloy which does not contain heavy rare earth metals such as Dy and Tb and has a relatively low melting point and low material cost is used. When producing a rare earth magnet by heat-treating the modified alloy in an active gas atmosphere and diffusing and infiltrating the compact, the temperature range of 260 to 400 ° C is adjusted to less than 120 seconds during the temperature rise process, and the modified alloy is melted. By raising the temperature to the temperature (diffusion penetration temperature), the modified alloy can be diffused and penetrated into the molded body without causing a hydroxylation reaction. Therefore, the modified alloy can be sufficiently diffused and penetrated into the molded body under low material cost and equipment cost, and a rare earth magnet having excellent coercive force performance can be manufactured.

It is the schematic diagram explaining until it manufactures a molded object in the manufacturing method of the rare earth magnet of this invention in order of (a) and (b). It is the figure explaining the microstructure of the molded object shown in FIG. 1b. FIG. 2 is a diagram illustrating a process up to manufacturing a rare earth magnet precursor in the manufacturing method of the present invention following FIG. 1. It is the figure explaining the microstructure of the rare earth magnet precursor of FIG. FIG. 4 is a diagram illustrating a process up to manufacturing a rare earth magnet by performing a heat treatment on a rare earth magnet precursor in the manufacturing method of the present invention following FIG. 3. It is a temperature rise control figure in the furnace in the case of heat processing. (A) is a diagram showing an X-ray diffraction analysis shows the (b) differential scanning calorimetry to identify the temperature range in which hydroxylation reaction occurs in the reforming alloy due to moisture in N ₂ gas (DSC) results FIG. It is a figure explaining the microstructure of the manufactured rare earth magnet. When the modified alloy is heat-treated and diffused and penetrated, the temperature rise time in an experiment that verified the possibility of diffusion and penetration of the modified alloy by variously changing the passing time in the temperature range of 260 to 400 ° C. It is the figure which showed the relationship (temperature increase rate) of temperature.

  Embodiments of a method for producing a rare earth magnet according to the present invention will be described below with reference to the drawings. The illustrated example describes a method for producing a rare-earth magnet, which is a nanocrystalline magnet. However, the method for producing a rare-earth magnet of the present invention is not limited to the production of a nanocrystalline magnet, and relative crystal grains Of course, it can be applied to the production of large sintered magnets. Further, the present invention is a method for producing a rare earth magnet having a coercive force distribution by partially diffusing and infiltrating a melt of a modified alloy into a desired portion without subjecting a formed body to hot plastic working. May be.

(Rare earth magnet manufacturing method)
FIGS. 1a and 1b are schematic views illustrating in order the manufacturing process of the molded body in the rare earth magnet manufacturing method of the present invention, and FIG. 2 is a diagram illustrating the microstructure of the molded body shown in FIG. 1b. 3 is a diagram for explaining the steps up to production of the rare earth magnet precursor in the production method of the present invention subsequent to FIG. 1, and FIG. 4 is a diagram for explaining the microstructure of the rare earth magnet precursor shown in FIG. is there. FIG. 5 is a diagram for explaining the process up to manufacturing the rare earth magnet by performing the heat treatment on the rare earth magnet precursor in the manufacturing method of the present invention following FIG. 3, and FIG. FIG. 8 is a temperature control diagram, and FIG. 8 is a diagram illustrating the microstructure of the manufactured rare earth magnet.

  As shown in FIG. 1a, for example, an alloy ingot is melted at a high frequency by a melt spinning method using a single roll in a furnace (not shown) in an Ar gas atmosphere whose pressure is reduced to 50 kPa or less. To produce a quenched ribbon B (quenched ribbon), which is coarsely pulverized.

  As shown in FIG. 1B, the coarsely pulverized quenched ribbon B is filled into a cavity defined by a carbide die D and a carbide punch P sliding in the hollow, and is pressed with the carbide punch P. (X direction) Nd-Fe-B main phase (crystal grain size of about 50 nm to 200 nm) of nanocrystalline structure and Nd around the main phase by flowing current in the pressurizing direction and conducting heating. A compact S composed of a grain boundary phase of -X alloy (X: metal element) is produced.

  Here, the Nd—X alloy constituting the grain boundary phase is composed of Nd and at least one alloy of Co, Fe, Ga, etc., for example, Nd—Co, Nd—Fe, Nd—Ga, Nd Any one of -Co-Fe and Nd-Co-Fe-Ga, or a mixture of two or more of these, is in an Nd-rich state.

  As shown in FIG. 2, the compact S exhibits an isotropic crystal structure in which the grain boundary phase BP is filled between the nanocrystal grains MP (main phase).

  Therefore, in order to give anisotropy to the molded body S, as shown in FIG. 3, the carbide punch P is brought into contact with the end surface in the longitudinal direction of the molded body S (the horizontal direction is the longitudinal direction in FIG. 1b). By applying hot plastic working while pressing with the punch P (X direction), a rare-earth magnet precursor C having a crystalline structure having anisotropic nanocrystalline grains MP as shown in FIG. 4 is manufactured. When the degree of processing (compression rate) by hot plastic working is large, for example, the case where the compression rate is about 10% or more can be referred to as hot strong processing or simply strong processing.

  In the crystal structure of the rare earth magnet precursor C shown in FIG. 4, the nanocrystal grains MP have a flat shape, and the interface substantially parallel to the anisotropic axis is curved or bent.

Next, as shown in FIG. 5, the manufactured rare earth magnet precursor C is accommodated in a high-temperature furnace H with a built-in heater, and a mass M of the reformed alloy is arranged above and below the rare earth magnet precursor C. It is contacted and heat-treated to the melting point which is the diffusion permeation temperature of the modified alloy while the inside of the furnace is in an inert gas atmosphere with N ₂ gas.

  Here, as the modified alloy M, an RE-Y alloy (RE: Nd, at least one of Pr, Y: transition metal element) containing no heavy rare earth element is used. As the transition metal element Y, any one of Cu and Al is applied. Therefore, as the RE-Y alloy, any of Nd-Cu alloy, Nd-Al alloy, Pr-Cu alloy and Pr-Al alloy can be used. Or use a kind.

  When the above-exemplified alloy is used as the RE-Y alloy, the eutectic point of the Nd-Cu alloy is 520 ° C, the eutectic point of the Pr-Cu alloy is 480 ° C, the eutectic point of the Nd-Al alloy is 640 ° C, The eutectic point of the Pr—Al alloy is 650 ° C., both of which have a low melting point of 700 ° C. or less.

  When an Nd-Cu alloy is used as the reforming alloy M, the eutectic point is 520 ° C. Therefore, the temperature inside the high temperature furnace H is about 520 ° C or higher (eg, about 600 ° C). As a result, the Nd—Cu alloy, which is a modified alloy, melts.

By the way, in order to make a high temperature furnace into a vacuum atmosphere at the time of this heat processing, the installation cost regarding a high temperature furnace becomes expensive, such as providing a vacuum suction device in a high temperature furnace. Therefore, in the illustrated example, a controlled furnace is used in which N ₂ gas is provided in the high temperature furnace H, and the inside of the furnace is made an inert gas atmosphere by N ₂ gas by circulation of exhausting air from the high temperature furnace H. The high temperature furnace H that provides such N ₂ gas is general-purpose and relatively inexpensive.

However, when a rare earth magnet precursor C and a modified alloy such as an Nd—Cu alloy in contact with the rare earth magnet precursor C are heat-treated in an N ₂ gas atmosphere, the Nd—Cu alloy is whitened to form Nd (OH) _3. It has been confirmed in the following experiment that a problem such that the material remains without being diffused and permeated may occur.

That is, the present inventors conducted an experiment in which an Nd—Cu alloy plate material and a powder slurry equivalent to 5.0 mass% (thickness 0.1 mm) were applied to the surface of the molded body in a N ₂ gas atmosphere and subjected to heat treatment. . Here, the N ₂ gas is 10 liters / minute and the dew point is -45 ° C, the magnet used is an upsetting product, the diffusion penetration temperature is 580 ° C, the temperature rise is 50 ° C / minute, and the holding time is 165 minutes It was.

FIG. 7a shows the result of X-ray diffraction analysis of Nd—Cu of the Nd—Cu alloy slurry powder remaining after the heat treatment, and Nd (OH) ₃ is identified from this analysis.

This is because Nd undergoes the following hydroxylation reaction in an N ₂ gas atmosphere during the heat treatment.
Nd + 3H ₂ O → 2Nd (OH) ₃ + 3 / 2H ₂

And the result of having investigated the temperature range which this reaction produces by differential scanning calorimetry (DSC) is shown in FIG. From the figure, it is specified that the hydroxylation reaction by moisture in N ₂ gas is in the temperature range of 260 to 400 ° C.

From this, at the time of heat treatment during diffusion penetration of the reformed alloy, in the process of raising the temperature to the melting temperature of the reformed alloy, the temperature of 260 to 400 ° C. is fast enough not to cause a hydroxylation reaction due to moisture in the N ₂ gas. By controlling the temperature so as to pass through the temperature range, the reformed alloy is prevented from undergoing a hydroxylation reaction, and the reformed alloy can be sufficiently diffused and penetrated into the formed body.

  Regarding this “speed that does not cause a hydroxylation reaction”, a time of less than 120 seconds has been specified as a result of experiments by the present inventors as described below.

  From the above, when the modified alloy is heat-treated and diffused into the compact, as shown in the control diagram of FIG. 6, the Nd—Cu alloy diffusion penetration temperature increases to the melting point of 520 ° C. In the process of heating, the temperature is controlled so that the temperature range of 260 to 400 ° C. is less than 120 seconds from the time t1 of 260 ° C. to the time t2 of 400 ° C., and the temperature is raised to the melting temperature of the modified alloy. Is.

  The molten Nd-Cu alloy melt diffuses and penetrates into the grain boundary phase BP, and Nd-Co, Nd-Fe, Nd-Ga, Nd-Co-Fe, Nd-Co-Fe-Ga and these A grain boundary phase in which a part or all of the mixed grain boundary phase is modified with the Nd—Cu alloy is formed.

  When Nd-Al alloy is used as the modified alloy M, the melting point is 640 to 650 ° C. Therefore, the Nd-Al alloy is melted by setting the temperature atmosphere to 640 to 650 ° C. The melt can be diffused and penetrated into the grain boundary phase, and Nd-Co, Nd-Fe, Nd-Ga, Nd-Co-Fe, Nd-Co-Fe-Ga and one of these Part or all of the grain boundary phase is modified with an Nd—Al alloy.

  Thus, by using a low melting point alloy alloy M having a low melting point of 700 ° C. or less and melting at a low temperature, for example, in the case of a nanocrystalline magnet, there is a problem when placed in a high temperature atmosphere of about 800 ° C. or more. The problem of coarsening of the crystal grains cannot occur.

  By using any one of the Nd-Cu alloy, Nd-Al alloy, Pr-Cu alloy, and Pr-Al alloy described above and performing a heat treatment for a predetermined time at a temperature equal to or higher than their melting points (at most 650 ° C), FIG. As shown, a rare earth magnet RM in which the grain boundary phase BP is modified to a composition rich in Nd or Pr is manufactured.

As shown in the figure, an interface (specific surface) substantially parallel to the anisotropic axis is formed when the reforming by the reforming alloy M is sufficiently advanced. Thus, the rare earth magnet RM of the present invention obtained by the manufacturing method described above is 700 ° C. with respect to the rare earth magnet precursor C obtained by performing hot plastic working for imparting anisotropy to the compact S. By diffusing and infiltrating the melt of the following low melting point modified alloy into the grain boundary phase, residual strain caused by hot plastic working is removed by contact with the melt of the reformed alloy, and crystal grains are further removed. The coercive force is improved by promoting the miniaturization and magnetic separation between crystal grains. In particular, the reformed alloy does not undergo a hydroxylation reaction during the heat treatment in an inert gas atmosphere such as N ₂ gas, but sufficiently diffuses and penetrates into the molded body at the melting point or higher of the reformed alloy. It is possible to manufacture rare earth magnets with excellent coercive force performance while significantly reducing manufacturing costs based on the reduction of material costs by not using them and the reduction of equipment costs by not using vacuum high temperature furnaces. Become.

[Experiment and results of verifying whether or not the modified alloy can diffuse and penetrate by changing the passage time in the temperature range of 260 to 400 ° C, which is the temperature rising process, when the modified alloy is heat treated and diffused and penetrated]
In the process of heat-treating the modified alloy by heat treatment, the present inventors adjust how much the transit time of 260 to 400 ° C., which is a temperature range in which Nd constituting the modified alloy can cause a hydroxylation reaction, is adjusted. An experiment was conducted on whether or not the occurrence of the hydroxylation reaction can be suppressed by doing so.

(Experimental conditions)
First, the test piece magnet was created by upsetting. The heat treatment was performed under two conditions: an inert gas atmosphere with N ₂ gas and a vacuum atmosphere.

The experiment in an inert gas atmosphere using N ₂ gas was performed using ULVAC's MILA-3000 as the lamp furnace, the heat treatment conditions were 650 ° C., the heat treatment time was 120 minutes, and the heating rate was as shown in FIG. , N ₂ gas: dew point -65 ° C. at 5 liters / minute, Nd—Cu alloy plate was used as the modified alloy, and the penetration amount was 10 mass%.

On the other hand, in the experiment under a vacuum atmosphere, ULVAC's MILA-3000 was used as a lamp furnace, the heat treatment conditions were 650 ° C., the heat treatment time was 120 minutes, and the heating rate was as shown in FIG. : 10 ^-3 Pa, Nd-Cu alloy plate was used as the modified alloy, and the penetration amount was 10 mass%.

  The conditions regarding the transit times of Comparative Examples 1 to 5 and Examples of 260 to 400 ° C. are shown in Table 1 below.

(Experimental result)
The experimental results are shown in Table 2 below.

（注記）拡散浸透の可否については、高価な真空炉を使用してなる比較例4、5と同等かそれ以上の改質効果が得られた場合を○、そうでない場合を×としている。

(Note) With regard to the possibility of diffusion and penetration, ○ is indicated when a reforming effect equivalent to or higher than Comparative Examples 4 and 5 using an expensive vacuum furnace is obtained, and × is indicated otherwise.

  From Table 2, from the measurement results of the coercive force before and after the treatment, Comparative Examples 1 to 3 showed no reforming effect, and the reforming effect could be confirmed in Examples and Comparative Examples 4 and 5.

  From the results of Comparative Examples 4 and 5 using these Examples and an expensive vacuum furnace, it is demonstrated that the Examples can obtain a higher reforming effect than Comparative Examples 4 and 5 using a vacuum furnace. .

  Moreover, as a result of observing the test pieces before and after the treatment, in Comparative Examples 1 to 3, it was confirmed from this observation that the Nd—Cu alloy plate remained on the surface of the molded body and the diffusion and penetration was not sufficiently performed. .

  On the other hand, it was confirmed from this observation that almost no Nd—Cu alloy plate remained on the surface of the molded body in the test piece of the example and sufficiently diffused and penetrated into the molded body.

  From this experimental result, a good result was obtained at 112 seconds as a transit time of 260 to 400 ° C., and a good result was not obtained at 168 seconds or more. By setting the extremely close 120 seconds as the threshold value for the modified alloy to sufficiently diffuse and penetrate, and adjusting the transit time of 260-400 ° C to less than 120 seconds, sufficient diffusion and penetration of the modified alloy is promoted and the coercive force is increased. It was concluded that a rare earth magnet with excellent performance could be manufactured.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  R: Copper roll, B: Quenched ribbon (quenched ribbon), D: Carbide die, P ... Carbide punch, S ... Molded body, C ... Rare earth magnet precursor, M ... Modified alloy (lumps), MP ... main phase (nanocrystal grains, crystal grains), BP ... grain boundary phase, RM ... rare earth magnet, H ... high temperature furnace

Claims (4)

RE formed into a compact of a metal structure composed of a RE-Fe-B main phase (at least one of RE: Nd and Pr) and a grain boundary phase of an RE-X alloy (X: metal element) around the main phase. Rare earths that produce rare earth magnets by contacting a reformed alloy made of an -Y alloy (Y: a metal element and not containing heavy rare earth elements) and then heat-treating the melt of the modified alloy to diffuse into the compact In the method of manufacturing a magnet,
The heat treatment is performed by raising the temperature above the melting temperature of the RE-Y alloy exceeding 400 ° C. in an inert gas atmosphere. In this temperature rising process, the temperature range of 260 to 400 ° C. is set to less than 120 seconds. Manufacturing method of rare earth magnet to be adjusted.   The RE-Y alloy is made of any one of Nd-Cu alloy, Nd-Al alloy, Pr-Cu alloy, and Pr-Al alloy, and the melting temperature of the RE-Y alloy is in the range of 480 to 650 ° C. Item 2. A method for producing a rare earth magnet according to Item 1.   The method for producing a rare earth magnet according to claim 1, wherein the inert gas is nitrogen gas.   The method for producing a rare earth magnet according to any one of claims 1 to 3, wherein hot plastic working which gives anisotropy to the compact is performed before the reformed alloy is brought into contact with the compact.

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