JP2013145832A - Method for manufacturing rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a rare earth magnet, capable of manufacturing a rare earth magnet excellent in squareness and high in maximum energy product.SOLUTION: A method for manufacturing a rare earth magnet includes: a first step of obtaining selected magnetic powder Q by removing magnetic powder having a particle size of less than 50 μm among magnetic powder comprising a main phase of an RE-T-B system (RE represents at least one of Nd, Pr and Y, and T represents Fe or one obtained by substituting a part of Fe with Co) and a grain boundary phase around the main phase, mixing modified alloy powder T comprising an RE-M alloy (M represents a transition metal element or a typical metal element, and RE may comprise RE1-RE2 where RE1 and RE2 represent at least one of Nd, Pr and Y) having a melting point of 700°C or below with the selected magnetic powder Q, and performing hot press working to manufacture a compact S; and a second step of subjecting the compact S to a hot plasticity processing to manufacture a rare earth magnet C.

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.

  As rare earth magnets, in addition to general sintered magnets with a crystal grain (main phase) scale of 3 to 5 μm constituting the structure, nanocrystal magnets with crystal grains refined to a nanoscale of about 50 nm to 300 nm are available. Among them, nanocrystal magnets that can reduce the amount of expensive heavy rare earth elements added (free) while miniaturizing the crystal grains described above are currently attracting attention.

  An example of a method for producing rare earth magnets is outlined as follows. For example, a rapidly cooled ribbon (quenched ribbon) obtained by rapidly solidifying Nd-Fe-B metal melt is pulverized to a desired size to produce raw magnetic powder. In general, a method of producing a rare earth magnet (orientated magnet) by forming a compact while pressing magnetic powder into a compact and subjecting the compact to hot plastic processing to impart magnetic anisotropy is generally applied.

  In Patent Document 1, a raw material obtained by mixing or covering a magnetic powder made of an Nd—Fe—B alloy with heavy rare earth modified alloy powder is first cold-formed to produce a cold-formed body. A method for producing a rare earth magnet is disclosed in which a hot formed body is produced by hot forming the hot formed body, or a hot plastic formed body is produced by subjecting the hot formed body to further hot plastic working. According to this manufacturing method, heavy rare earth elements such as Dy concentrated in the grain boundary phase can be uniformly distributed, and the coercive force can be improved while suppressing a decrease in residual magnetic flux density.

  By the way, in the process of manufacturing a rare earth magnet by the hot plastic working, a part of crystal grains adjacent to each other is magnetically coupled to a relatively large crystal grain. There are no relatively small grains. This is because the raw magnetic powder has various particle sizes, and among them, the relatively fine magnetic powder easily oxidizes the modified alloy, so that the grain boundary reforming effect by the modified alloy is not good. This is because, as a result, the crystal grains adjacent to each other in the hot plastic working easily break through the grain boundary phase that is insufficiently modified and are magnetically coupled.

  In general, when the crystal grains are small, the coercive force is high, and when the crystal grains are large, the coercive force is low, but instead the magnetization is high. Therefore, when such large and small crystal grains are mixed, the corners of the MH loop (magnetic hysteresis loop) tend to be rounded, which means that the squareness of the magnet (squareness ratio) Can be said to be worse). A magnet having excellent squareness is a magnet in which the M-H loop is as close to a quadrangle as possible, and thus the corners are close to 90 degrees.

  Poor squareness means that the maximum energy product of the magnet becomes small. Therefore, even if a magnet with high coercive force is used, a magnet with poor squareness is applied to a motor. However, the performance will be insufficient.

JP 2010-263172 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a rare earth magnet that can produce a rare earth magnet having excellent squareness and a high maximum energy product.

  In order to achieve the above object, the method for producing a rare earth magnet according to the present invention is based on a RE-TB-based main phase (at least one of RE: Nd, Pr, Y, T: Fe, Fe partially substituted with Co). ) And RE-M alloy (M: transition metal) having a melting point of 700 ° C. or less, with the magnetic powder having a grain size of less than 50 μm removed from the magnetic powder composed of the grain boundary phase around the main phase. RE or RE2 may be RE1-RE2, RE1 or RE2: at least one of Nd, Pr, and Y) is mixed with this selected magnetic powder, It comprises a first step of producing a molded body by pressing and a second step of producing a rare earth magnet by hot plastic working the molded body.

  In the production method of the present invention, when producing a compact (bulk body) by hot pressing, magnetic powder as a raw material is classified, and specifically, magnetic powder having an average particle size of less than 50 μm is removed to obtain the raw magnetic powder. After the selection, the selected magnetic powder is mixed with a modified alloy powder having a melting point of 700 ° C. or lower and hot pressed.

  According to the present inventors, by removing magnetic particles having a particle size of less than 50 μm and using a low melting point modified alloy having a melting point of 700 ° C. or less, it has excellent squareness, and therefore maximum energy. It has been demonstrated that high volume rare earth magnets can be obtained.

  The rare earth element constituting the crystal grains (main phase) is composed of at least one of Nd, Pr, and Y. In addition to this, Di (zidym) known as an intermediate product of Nd and Pr can also be applied. .

  As the “transition metal element” or “typical metal element” constituting the modified alloy powder, any one of Cu, Mn, Co, Ni, Zn, Al, Ga, Sn, etc. can be applied. . It should be noted that heavy rare earth elements are not completely excluded as a component of the reformed alloy powder, and that the rare earth elements such as Dy, Tb, and Ho make alloy compositions under conditions that satisfy the melting point of 700 ° C or lower. Quality alloy powder can also be used.

  The RE-M alloys that form the modified alloy powder include Nd-Cu alloys (eutectic point 520 ° C), Pr-Cu alloys (eutectic point 480 ° C), Nd-Pr-Cu alloys, Nd-Al alloys ( Eutectic point 640 ℃), Pr-Al alloy (650 ℃), Nd-Pr-Al alloy, Nd-Co alloy (eutectic point 566 ℃), Pr-Co alloy (eutectic point 540 ℃), Nd-Pr Any one of -Co alloys can be applied. Examples of alloys containing heavy rare earth elements include 60Nd-30Cu-10Dy alloy (eutectic point 503 ° C.), 50Nd-30Cu-20Dy (eutectic point 576 ° C.), and the like.

Since it can be melted at a low temperature by using the low melting point modified alloy powder in this way, for example, a nanocrystalline magnet (crystal The production method of the present invention is suitable for a particle size of about 50 nm to 300 nm.
Moreover, it is preferable that content rate of RE exists in the range of 28-32 mass% among the said magnetic powder.

  When the RE content is less than 28% by mass, there is a high possibility of cracking during hot plastic working, and the orientation of crystal grains is likely to decrease, and the RE content is 32% by mass. Is greater than the above, it is based on the knowledge of the present inventors that the processing strain during hot plastic working is easily absorbed by the relatively soft grain boundary phase, and hence the orientation of the crystal grains is likely to be lowered. is there.

  Further, it is preferable that the reformed alloy powder is mixed at a ratio of 1.5% by mass or less in the raw material in which the modified alloy powder and the selected magnetic powder are mixed.

  When the mixing ratio of the modified alloy powder exceeds 1.5% by mass, the present inventor says that the processing strain at the time of hot plastic working is easily absorbed by the grain boundary phase, and therefore the orientation of the crystal grains tends to be lowered. Based on such findings.

  Furthermore, it is preferable to perform the hot plastic working in the second step in a temperature atmosphere in the range of 700 to 800 ° C.

  Each crystal grain is oriented in the direction of easy magnetization (so-called C-axis orientation) when the crystal grains constituting the compact are rotated by hot plastic working or slip occurs on an arbitrary crystal plane. When hot plastic working is performed under a temperature condition of less than 700 ° C, the molded body is liable to crack, and when it is performed under a temperature condition of more than 800 ° C, the grain growth rate becomes too rapid and the coercive force This is based on the knowledge of the present inventors that it is likely to greatly decrease.

  As can be understood from the above description, according to the method for producing a rare earth magnet of the present invention, when producing a molded body by hot pressing, magnetic powder having a particle size of less than 50 μm is removed, and the raw magnetic powder is selected. Furthermore, a hot-press process is performed on the selected magnetic powder mixed with a modified alloy having a melting point of 700 ° C. or lower to produce a rare earth magnet precursor, which is then subjected to hot plastic working. By producing rare earth magnets (orientated magnets), the reformed alloy powder is not oxidized with fine magnetic powder, and thus a high grain boundary reforming effect by the reformed alloy powder can be obtained. Magnetic coupling can be suppressed. Therefore, it is possible to produce a rare earth magnet having a large maximum energy product, which is a rare earth magnet made of crystal grains having a uniform grain size, having no large difference in grain size, and having excellent squareness.

It is the schematic diagram explaining the 1st step of the manufacturing method of the rare earth magnet of this invention. FIG. 2 is a diagram illustrating a first step following FIG. 1. FIG. 3 is a diagram illustrating a first step following FIG. 2. It is the figure which expanded the structure | tissue of the molded object manufactured at the 1st step. FIG. 5 is an enlarged view of a portion V in FIG. 4 and shows a microstructure of a crystal structure. It is the schematic diagram explaining the 2nd step of the manufacturing method of the rare earth magnet of this invention. It is the figure which showed the microstructure of the crystal structure of the rare earth magnet manufactured at the 2nd step. It is a figure which shows the experimental result which verified the squareness ratio according to the presence or absence of classification of a magnetic powder, and the particle size in the case of classification. It is a figure which shows the experimental result which verified the squareness ratio at the time of changing the mixing ratio of the presence or absence of classification of magnetic powder, and a modified alloy powder. It is a figure which shows the experimental result which verified the magnetic characteristic at the time of changing the presence or absence of classification of a magnetic powder, and the mixing ratio of a modified alloy powder. It is a figure which shows the MH loop at the time of changing the presence or absence of classification of magnetic powder, and the mixing ratio of reforming alloy powder, (a) is a result when there is no reforming alloy powder, (b) is modification This is the result when the alloy powder is 1% by mass. It is a figure which shows the experimental result which verified the squareness ratio and magnetic characteristic at the time of changing the raw material of a modified alloy powder.

  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 (for example, having a particle size of about 1 μm).

(Rare earth magnet manufacturing method)
1, 2 and 3 are schematic views illustrating the first step of the method of manufacturing a rare earth magnet of the present invention in that order, and FIG. 4 is an enlarged view of the structure of the molded body manufactured in the first step. FIG. 5 is an enlarged view of a portion V in FIG. 4 and shows a microstructure of the crystal structure.

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

  Next, the magnetic powder formed by coarsely pulverizing the quenched ribbon B is classified, and the magnetic powder having a particle size (average particle diameter) of less than 50 μm is removed and the magnetic powder is selected to obtain the selected magnetic powder Q.

  Next, as shown in FIG. 2, the selected magnetic powder Q and the modified alloy powder T are respectively put into a container in a predetermined amount and mixed to produce a molded body raw material R.

  As shown in FIG. 3, the produced molded body raw material R is filled in a cavity defined by a carbide die D and a carbide punch P that slides inside the hollow, and is pressed with the carbide punch P ( X direction) The main phase of RE-Fe-B system (RE: Nd, Pr, Y) of nanocrystal structure (currently 20nm to 200nm crystal grains) by applying current in the pressurizing direction and conducting heating. And a compact S comprising a grain boundary phase of an Nd—X alloy (X: metal element) around the main phase is manufactured by hot pressing (first step).

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

  On the other hand, the modified alloy powder is an RE-M alloy (M: transition metal element or typical metal element, RE may be RE1-RE2, and RE1, RE2: at least one of Nd, Pr, and Y). It is a material. Here, as the transition metal element or the typical metal element, any one of Cu, Mn, Co, Ni, Zn, Al, Ga, Sn and the like can be applied.

  Among them, it is assumed that a low melting point RE-M alloy having a melting point of 700 ° C. or less is used, for example, Nd—Cu alloy (eutectic point 520 ° C.), Pr—Cu alloy (eutectic point 480 ° C.), Nd -Pr-Cu alloy, Nd-Al alloy (eutectic point 640 ° C), Pr-Al alloy (650 ° C), Nd-Pr-Al alloy, Nd-Co alloy (eutectic point 566 ° C), Pr-Co alloy (Eutectic point 540 ° C), any one of Nd-Pr-Co alloy is applied.

  In the selected magnetic powder Q, the RE content is preferably in the range of 28 to 32% by mass. When the RE content is less than 28% by mass, there is a high possibility that cracking will occur during the subsequent second step of hot plastic working, and the orientation of the crystal grains tends to decrease. This is because when the RE content exceeds 32% by mass, the processing strain during hot plastic processing is easily absorbed by the relatively soft grain boundary phase, and hence the orientation of the crystal grains is likely to decrease. .

  Further, in the molded body raw material R in which the modified alloy powder T and the selected magnetic powder Q are mixed, the modified alloy powder T is preferably mixed at a ratio of 1.5% by mass or less. This is because if the mixing ratio of the modified alloy powder exceeds 1.5% by mass, the working strain at the time of hot plastic working is easily absorbed by the grain boundary phase, and therefore the orientation of the crystal grains tends to be lowered.

  In the hot press work shown in FIG. 4, the above-described modified alloy powder T having a low melting point is used, so a relatively low temperature of 700 ° C. or lower (when an Nd alloy having a eutectic point at about 300 ° C. is used) Can be melted in the modified alloy powder T by performing hot pressing (for example, holding at 50 to 500 MPa for 15 seconds or more to increase the density) at a temperature corresponding to the eutectic point. The coarsening of the crystal grains constituting the nanocrystal magnet can be effectively suppressed.

  Then, a melt T ′ of the modified alloy powder obtained by melting the modified alloy powder T spreads over the magnetic powder interface between the magnetic powders constituting the compact S. Note that the microstructure of the magnetic powder Q structure of the compact S exhibits an isotropic crystal structure in which the grain boundary phase BP is filled between the nanocrystal grains MP (main phase) as shown in FIG.

  Once the molded body S is obtained in the first step, the molded body is then placed in the cavity defined by the cemented carbide die D and the cemented carbide punch P that slides in the hollow, as in the first step. By accommodating S and performing hot plastic working, the melt T ′ of the modified alloy powder diffuses into the grain boundary phase, and a rare earth magnet C having an increased coercive force is produced (second second). Step).

  As shown in FIG. 7, the rare earth magnet C is a magnet whose magnetic anisotropy is imparted by hot plastic working and whose magnetization is increased.

  According to the method for producing a rare earth magnet shown in the drawing, when producing a compact by hot pressing, magnetic powder as a raw material is classified, and magnetic powder having a particle size of less than 50 μm is removed to select the raw magnetic powder. A molded body raw material R obtained by mixing a reformed alloy powder T having a melting point of 700 ° C. or lower with the magnetic powder produced is hot pressed to produce a molded body S that is a rare earth magnet precursor. By producing the rare earth magnet C by performing hot plastic working, the modified alloy powder T is not oxidized by the fine magnetic powder, and thus a high grain boundary reforming effect by the modified alloy powder is obtained, Magnetic coupling between crystal grains can be suppressed. Therefore, the rare earth magnet C having no significant difference in particle diameter and made of crystal grains with uniform particle diameters, and thus excellent in squareness and high maximum energy product can be manufactured.

[Experiment and results of verifying the squareness ratio according to the presence / absence of magnetic powder classification and the particle size during classification]
The present inventors conducted an experiment to verify the squareness ratio according to the presence / absence of classification of magnetic powder and the particle size at the time of classification. Hereinafter, the manufacturing methods of Examples 1 and 2 will be described, and the manufacturing methods of Comparative Examples 1 to 6 will be described.

  Rare earth alloy material (alloy composition is 29% by mass, 29Nd-0.2Pr-4Co-0.9B-0.6Ga-bal.Fe) is blended in a predetermined amount and dissolved in an Ar gas atmosphere. The alloy ribbon was produced by injecting it onto a Cu rotating roll with plating and quenching it. After pulverizing this alloy ribbon with a cutter mill, those that are not sieved are referred to as Comparative Examples 1 and 3 (Comparative Example 1 has modified alloy powder, and Comparative Example 3 has modified alloy powder. Nothing), the one that has been sieved, the upper limit is 2 mm and the fine side is classified by 38 μm (Comparative Example 2 has a modified alloy powder, Comparative Example 4 has no modified alloy powder) 1), fine side classified by 53 μm (Example 1 has modified alloy powder, Comparative Example 5 does not have modified alloy powder), fine side classified by 74 μm (Example 2 has a modified alloy powder, and Comparative Example 6 has no modified alloy powder).

  1% by mass of Nd—Cu alloy powder having a particle size of 74 to 250 μm or less was mixed with 9 g of the above various rare earth alloy powders, and mixed for 10 minutes with a powder mixer.

Next, the mixed powder is accommodated in a carbide die having a volume of φ10 mm and a height of 40 mm, sealed with upper and lower carbide punches, set in a chamber, and reduced in pressure to 10 ⁻² Pa while being high-frequency coil. Was heated to 650 ° C and hot pressed at 300MPa at the stage of 650 ° C, and then held for 30 seconds to produce a molded body with a height of 15mm.

  Examples 1 and 2 and Comparative Examples 1 to 6 were stored in a φ20 mm carbide die, sealed with upper and lower carbide punches, and heated to 750 ° C. by high-frequency heating to perform hot plastic working. Each rare earth magnet test piece was manufactured.

  For each test piece of Examples 1 and 2 and Comparative Examples 1 to 6, cut out the center 2 × 2 × 2.2 mm, measure the magnetic properties of each, and create an MH loop to determine the squareness ratio. Asked. The magnetic property evaluation is a measurement of coercive force and magnetization at RT using a vibrating sample magnetometer. The experimental results are shown in Table 1 below and FIG.

  Here, Hc is the coercive force (average coercive force) when the magnetic flux density is zero, Hk is the coercive force when the magnetic flux density is 90% of the residual magnetic flux density, and the value of Hk / Hc is the squareness ratio. It becomes. Note that the coercivity value in SI units (kA / m) is obtained by multiplying the coercivity value in the table by 79.6.

  From Table 1 and FIG. 8, it is demonstrated that Examples 1 and 2 are rare earth magnets having a large maximum energy product and a large square energy ratio as compared with Comparative Examples 1 to 6. This is considered to be because the magnetic powder of less than 53 μm was classified and removed, and the modified alloy powder made of Nd—Cu alloy was mixed as a raw material of the compact. Considering this result and ease of classification (in units of 10 μm, not in units of μm), it is considered better to set the magnetic powder of less than 50 μm to the critical value for classification.

[Experiment and results of verifying the squareness ratio when changing the mixing ratio of the modified alloy powder and the presence or absence of magnetic powder classification]
The present inventors further conducted an experiment for verifying the squareness ratio when the presence / absence of classification of magnetic powder and the mixing ratio of the modified alloy powder were changed.

  In this experiment, a test piece is manufactured by a method substantially similar to the experiment described above. However, with classification, the sieve particle size is 74 μm, and the mixing ratio of the Nd-Cu alloy is 0 mass%, 0.5 mass%, 1 mass%, 1.5 mass%, 2 mass%, 3 mass%, 5 mass It is changed by%. The experimental results are shown in Table 2 below and FIGS.

  From Table 2 and FIGS. 9 and 10, it is proved that each of Examples 2 to 4 improves both the squareness ratio and the magnetization as compared with the comparative example.

  For example, in Comparative Examples 9 to 11, although the squareness ratio is improved as compared with other comparative examples, the magnetization is greatly reduced as compared with the Example, and both the squareness ratio and the magnetization are improved. I can't.

  Specifically, not only the presence / absence of classification and the presence / absence of modified alloy powder made of Nd-Cu alloy, but also the mixing amount of the modified alloy powder has a large effect, and if this mixing ratio exceeds 1.5% by mass, the magnetization will increase. It has been demonstrated to decline.

  This is because, by adding a low melting point Nd-Cu alloy, this alloy melts during hot plastic working and absorbs processing strain. This is thought to lead to a decline in However, when the mixing amount is up to 1.5% by mass, the rate of decrease is small, and the effect of improving the squareness ratio is greater. Therefore, the mixing rate of the modified alloy powder is preferably set to 1.5% by mass or less.

  FIG. 11a shows the M-H loops of Comparative Examples 3 and 6, and FIG. 11b shows the M-H loops of Example 2 and Comparative Example 1.

  In Comparative Examples 3 and 6 in FIG. 11a that does not have the modified alloy powder, a large change in the squareness ratio cannot be confirmed depending on the presence or absence of classification, but from FIG. It can be confirmed that the squareness ratio of Example 2 is greatly improved as compared with Comparative Example 1 depending on the presence or absence of classification.

[Experiment and results of verifying squareness ratio and magnetic properties when changing the material of the modified alloy powder]
The inventors further conducted an experiment to verify the squareness ratio and magnetic characteristics when the material of the modified alloy powder was changed.

  In this experiment, classification is performed with a 53 μm sieve, and hot plastic working is performed at 750 ° C. as in the experiment described above. The following Table 3 and FIG. 12 show the experimental results based on the presence or absence of the modified alloy powder and the difference in the modified alloy powder type.

  From Table 3 and FIG. 12, the modified alloy powders used in Comparative Examples 12 to 14 have melting points exceeding 700 ° C., and both the coercive force and the squareness ratio are markedly higher than those of Examples 5 to 8. It is low. This is considered that the coercive force was not improved because the reformed alloy powder was not melted at the heating temperature during hot plastic working.

  On the other hand, since Examples 5 to 8 have a modified alloy powder having a melting point of 700 ° C. or lower, the modified alloy powder is sufficiently melted during hot plastic working, and the grain boundary phase is good. As a result of the modification, both the coercive force and the squareness ratio are considered to have improved. If hot plastic working is performed at the melting point temperature of each modified alloy powder used in the comparative example, the coarsening of crystal grains becomes a problem, and the coarsening cannot be expected to greatly improve the coercive force.

  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.

  W: Copper roll, B: Quenched ribbon (quenched ribbon), Q: Selected magnetic powder, T: Modified alloy powder, T ′: Melted liquid of modified alloy powder, R: Molded raw material, D: Carbide Dies, P ... Carbide punch, S ... Molded body, C ... Rare earth magnet (orientation magnet), MP ... Main phase (nanocrystal grains, crystal grains), BP ... Grain boundary phase

Claims (6)

RE-TB main phase (at least one of RE: Nd, Pr, Y, T: Fe, a part of Fe is replaced by Co) and a magnetic particle consisting of a grain boundary phase around the main phase Of these, RE-M alloy (M: transition metal element or typical metal element, where RE is RE1-RE2) First, a modified alloy powder made of RE1, RE2: at least one of Nd, Pr, and Y) is mixed with the selected magnetic powder and subjected to hot pressing to produce a molded body,
A method for producing a rare earth magnet comprising a second step of producing a rare earth magnet by hot plastic working the molded body.   The method for producing a rare earth magnet according to claim 1, wherein the RE content in the magnetic powder is in the range of 28 to 32 mass%.   The method for producing a rare earth magnet according to claim 1 or 2, wherein the reformed alloy powder is mixed at a ratio of 1.5% by mass or less of the raw material in which the modified alloy powder and the selected magnetic powder are mixed.   The method for producing a rare earth magnet according to any one of claims 1 to 3, wherein the hot plastic working is performed in a temperature atmosphere in a range of 700 to 800 ° C.   The method for producing a rare earth magnet according to any one of claims 1 to 4, wherein M of the RE-M alloy is any one of Cu, Mn, Co, Ni, Zn, Al, Ga, and Sn.   Nd-Cu alloy, Pr-Cu alloy, Nd-Pr-Cu alloy, Nd-Al alloy, Pr-Al alloy, Nd-Pr-Al alloy, Nd-Co alloy, Pr-Co alloy, Nd as RE-M alloy The method for producing a rare earth magnet according to any one of claims 1 to 5, wherein any one of -Pr-Co alloys is used.

Images