JP5786708B2 - Rare earth magnet manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a rare earth magnet that is an oriented magnet by hot plastic working.

  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.

  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. In general, a method of producing a rare earth magnet (orientated magnet) by performing hot plastic working to impart the above-mentioned properties is applied.

  In the hot plastic working, for example, a compact is disposed between upper and lower punches (also referred to as punches) and heated and pressed with the upper and lower punches for a short time of, for example, about 1 second or less. When the molded body is crushed while being plastically deformed by pressing with a punch, there is a problem that the side surface of the plastically deformed molded body is likely to crack. One reason for this is that the portions that are in contact with the upper and lower punches are not easily deformed, and the central portion of the side surface is excessively swollen so as to be deformed in a so-called drum shape. When this crack occurs, the processing strain formed to increase the degree of orientation is released at the cracked location, and the strain energy cannot be sufficiently directed to the crystal orientation, resulting in a high degree of orientation (this Therefore, it is difficult to obtain an oriented magnet having high magnetization.

  Therefore, a manufacturing method disclosed in Patent Document 1 can be cited as a prior art that can solve the problem of cracking during such hot plastic working. In this manufacturing method, after the whole molded body is encapsulated in a metal capsule, hot plastic working is performed while pressing the metal capsule with upper and lower punches. The magnetic anisotropy is further improved.

  However, if the entire molded body is completely surrounded by the metal capsule, the plastic deformation to the side of the molded body due to pressing from above and below is extremely restricted, and the side surface of the molded body after plastic deformation is cracked. In spite of the fact that it does not occur, sufficient plastic deformation is difficult to be performed, and as a result, another problem that it is difficult to obtain a high degree of orientation may occur. For example, when taking a cylindrical shaped body having an upper surface, a lower surface and a circumferential side surface as an example, when a side region corresponding to the side surface of the molded body of the metal capsule is about to be plastically deformed laterally, The upper surface region and the lower surface region corresponding to the upper surface and the lower surface of the molded body integrated with the side surface region are constrained by restraining the spread of the side surface region.

JP-A-2-250920

  The present invention has been made in view of the above-described problems, and relates to a manufacturing method for manufacturing a rare earth magnet through hot plastic working, in which cracks are generated on the side surface of a molded body that is plastically deformed during hot plastic working. It is an object of the present invention to provide a method for producing a rare earth magnet capable of producing a rare earth magnet having a high degree of orientation by suppressing sufficient plastic deformation.

  In order to achieve the above object, the method for producing a rare earth magnet according to the present invention comprises a first step of producing a molded body having an upper surface, a lower surface and a side surface by pressure-molding a powder as a rare earth magnet material, the molded body. A frame body having a ductility relatively higher than that of the molded body is provided on the side surface of the molded body to form a unit body of the molded body and the frame material surrounded by the side surface, and sandwiched between the upper and lower punches. The second step is to produce a rare earth magnet which is an oriented magnet by performing hot plastic working which gives anisotropy while directly pressing the upper and lower surfaces of the compact.

  The method of manufacturing a rare earth magnet according to the present invention is not limited to enclosing the entire compact in a metal cap in the hot plastic working in the production process, but rather the upper and lower pressing the compact during the hot plastic working. The upper and lower surfaces of the molded body corresponding to the punch (or punch) are opened, and hot plastic working is performed by pressing with a punch in a posture in which only the side surface of the molded body is surrounded by a frame material.

  Here, the frame material that surrounds only the side surface of the molded body is made of a material having a ductility that is relatively higher than the ductility of the molded body, and is formed when a certain pressing force is applied from the upper and lower punches. Without excessively restraining the plastic deformation to the side of the body, the frame material is also plastically deformed to the side, thereby ensuring sufficient plastic deformation to the side of the molded body, with a slight restriction. Generation of cracks on the side of the molded body can be suppressed.

  For example, copper, its alloys, mild steel, low carbon steel, etc. can be cited as metal materials that are more ductile than this compact, which can be formed by pressure molding Ne-Fe-B powder. Then, the frame member made of the material metal rich in ductility is fitted so as to completely surround the side surface of the molded body to form a unit body made of the molded body and the frame material.

  By placing this unit body between the upper and lower punches and directly pressing the upper and lower surfaces of the molded body constituting the unit body with the upper and lower punches, both the frame material and the molded body are crushed while plastically deforming sideways. However, the plastically deformed molded body does not reach excessive plastic deformation to the extent that cracks occur in the frame material located on the outer periphery thereof, however, it is plastically deformed to such an extent that a high degree of orientation can be ensured, and magnetic anisotropy is achieved. An excellent oriented magnet is formed. In particular, since the side surface can be prevented from swelling in a drum shape, it has a great effect on preventing cracks.

  In addition to the hexahedron and other polyhedrons (such as octahedrons), the molded body can be applied to a variety of solid shapes such as cylinders, truncated cones, truncated pyramids, etc. Shaped frame material is used.

  If the mold used in hot plastic processing is composed of upper and lower punches and a frame-shaped die on which these punches slide, the mold is formed in a cavity defined by the die and the punch. The mold will be accommodated and hot plastic working will be performed, but the size of this cavity should not be large enough to prevent the molded body and the surrounding frame material from being sufficiently plastically deformed. Become.

  In another embodiment of the method for producing a rare earth magnet according to the present invention, the first step of producing a molded body having an upper surface, a lower surface, and a side surface by pressure-molding a powder to be a rare earth magnet material, the molding Two lid members which are provided with a duct material having a ductility relatively higher than that of the molded body on the side surface of the body, and which have a ductility which is relatively higher than that of the molded body and which are cut off from the frame material. Are formed on the upper surface and the lower surface of the molded body, respectively, to form a unit body consisting of a frame material and a lid material whose side surfaces and upper and lower surfaces are mutually cut off, and a molded body surrounded by these, and this is formed by upper and lower punches. From the second step of manufacturing a rare earth magnet that is an oriented magnet by sandwiching and performing hot plastic processing to give anisotropy while pressing the upper and lower lids positioned on the upper and lower surfaces of the molded body with the upper and lower punches It will be.

  In the present embodiment, the unit body is formed by covering the molding die with upper and lower lid materials which are cut off from the frame material and are relatively more ductile than the molding die, and the upper and lower lids are formed by upper and lower punches. Hot plastic working is performed while pressing the material.

  Not only the molded body, but also the frame material and the lid material can be sufficiently plastically deformed. Therefore, the upper and lower punches do not directly press the molded body but press the lid material, so that the molded body is The damage that can occur when pressed directly by the punch can be completely eliminated.

  Further, by interposing a lid material having a higher ductility than the molded body between the punch and the molded body, the lid material is plastically deformed and a pressing force from the punch is applied to the molded body. By playing a role like a cushion material (also referred to as a lubrication effect), it is possible to further suppress cracks that may occur in the molded body.

  Furthermore, since the frame material and the lid material are cut off, the lid material does not hinder the deformation of the frame material as in the prior art described above, and the frame material can be deformed independently, so the crack prevention effect is Extremely high.

  According to the verification by the present inventors, due to the above-described lubricating effect of the lid material, the pressing force from the punch is transmitted to the molded body via the upper and lower lid materials, thereby the thickness direction (or height direction) of the molded body. A uniform pressing force can be applied to the molded body, and the molded body is uniformly deformed in the thickness direction (if the drum has a drum shape that swells only near the thickness center, this deformation tends to cause cracking), and the degree of orientation of the entire magnet is high. It has been proved to be an oriented magnet.

  Apply a lubricant to the surface where the frame or lid material contacts the molded body, or the surface where the lid material contacts the punch, and reduce the frictional force between the members in contact with each other as much as possible. It is preferable to perform plastic working.

  As can be understood from the above description, according to the method of manufacturing a rare earth magnet of the present invention, in the hot plastic working in the manufacturing process, instead of enclosing the entire compact in a metal cap, The upper and lower surfaces of the molded body corresponding to the upper and lower punches that press the molded body during processing are opened, and hot plastic working is performed by pressing with the punch in a posture in which only the side surface of the molded body is surrounded by the frame material. By carrying out the process, the molded body can be sufficiently plastically deformed without causing cracks in the molded body or hardly causing cracks, thereby producing a rare earth magnet having a high degree of orientation and excellent magnetizing performance. be able to.

It is the schematic diagram explaining the 1st step of the manufacturing method of the rare earth magnet of this invention in order of (a) and (b). It is a figure explaining the microstructure of the molded object manufactured at the 1st step. (A) is the figure which showed the condition which is going to fit the frame material in the molded object, (b) is the figure which showed the unit body which consists of a molded object and a frame material. (A) is the figure which showed the condition which is going to arrange | position the cover material to the unit body of FIG. 3, (b) is the figure which showed the unit body which consists of a molded object, a frame material, and a cover material. It is the figure explaining the 2nd step of the manufacturing method in order of (a) and (b). It is a figure explaining the microstructure of the manufactured oriented magnet (rare earth magnet). It is a figure which shows the experimental result which verified the relationship between a processing rate and orientation degree. (A) is a photograph of the oriented magnet of Example 1 after the experiment, and (b) is a photograph of the oriented magnet of Comparative Example 1 after the experiment. (A) is a figure which shows the experimental result which verified the relationship between the distance from the upper surface of a molded object, and a processing rate, (b) is a photograph figure of Example 3. FIG. It is a figure which shows the experimental result which verified the relationship between the distance from the upper surface of an orientation magnet, and a residual magnetization.

  Embodiments of a method for producing a rare earth magnet according to the present invention will be described below with reference to the drawings. Although the illustrated oriented magnet has been described for a case of a nanocrystalline magnet (particle size is about 200 nm or less), the oriented magnet targeted by the production method of the present invention is limited to a nanocrystalline magnet. These include, but not limited to, those having a particle size of 300 μm or more, sintered magnets having a particle size of 1 μm or more, and bonded magnets in which crystal grains are bound with a resin binder. In the illustrated example, the molded body formed in the first step is a cylindrical body, but various shapes other than this, for example, a polyhedron such as a hexahedron (an octahedron, etc.), a truncated cone, Of course, a three-dimensional shape such as a truncated pyramid may be used.

(Rare earth magnet manufacturing method)
FIGS. 1a and 1b 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. 2 is a view illustrating the microstructure of the molded body manufactured in the first step. is there. FIG. 3 is a diagram showing a unit body composed of a molded body and a frame material, and FIG. 4 is a diagram showing a unit body composed of the molded body, the frame material, and upper and lower lid materials. 5A and 5B are schematic views illustrating the second step of the manufacturing method in that order, and FIG. 6 is a diagram illustrating the microstructure of the oriented magnet (rare earth magnet) manufactured in the second step. is there.

  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 cylindrical shaped body S composed of a grain boundary phase of -X alloy (X: metal element) is manufactured (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.

  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).

  When the molded body S is manufactured in the first step, a metal frame material having ductility (deformability) higher than that of the mold S is attached to the side surface of the cylindrical molded body S. More specifically, as shown in FIG. 3 a, a ring-shaped frame material C having the same height as the molded body S and the same inner diameter as the molded body S with respect to the cylindrical molded body S. To form a unit body U composed of a molded body S and a frame material C as shown in FIG.

  Depending on the material of the frame material, the dimensional relationship between the molded body and the frame material is preferably as follows. That is, when the frame material is made of copper or a copper alloy and the molded body is a cylindrical body, when the diameter of the molded body is D, use a frame material with a thickness of 0.1D to 0.3D, When the molded body is a rectangular parallelepiped, a thick frame material of 0.1 L to 0.3 L is used when one side in the extending direction of the molded body is L. This is because the crack prevention effect is small when it is less than 0.1D and 0.1L, and the plastic flow for orientation is disturbed when it exceeds 0.3D and 0.3L.

  On the other hand, when the frame material is made of mild steel and the molded body is a cylindrical body, when the diameter of the molded body is D, a frame material with a thickness of 0.05D to 0.15D is used, and the molded body is In the case of a rectangular parallelepiped, a thick frame material of 0.05 L to 0.15 L is used, where L is one side in the extending direction of the molded body. This is because the crack prevention effect is small when it is less than 0.05D and 0.05L, and the magnet is cracked when it exceeds 0.15D and 0.15L.

  Further, as shown in FIG. 4a, an upper lid F and a lower lid F may be arranged above and below a unit body made up of the mold S and the frame material C, and a separate unit body U1 may be formed as shown in FIG. 4b. .

  The next step will be described using the unit body U shown in FIG. 3b. As shown in FIG. 5a, the unit body U is accommodated in a cavity defined by a carbide die D and a carbide punch P sliding in the hollow, and the upper and lower punches P, P are used to The lower surface, that is, the upper and lower surfaces of the molded body S exposed vertically is sandwiched between the end surfaces of the frame member C.

  Then, by sliding the upper and lower punches P, P in close proximity to each other in a high temperature atmosphere in the cavity in a short time of 1 second or less (hot plastic working) (in the X direction in FIG. 5a) Pressing), as shown in FIG. 5b, the molded body S and the frame material C having higher ductility are plastically deformed laterally (Y direction).

  By imparting a working strain to the molded body S by this lateral plastic deformation, an oriented magnet S ′ (rare earth magnet) having magnetic anisotropy and a high degree of orientation is obtained (second step). (In the figure, C ′ is a frame material after plastic deformation). In this hot plastic working, in addition to the processing temperature and processing time, adjustment of the strain rate is also an important factor.

  By this hot plastic working, as shown in FIG. 6, an oriented magnet S ′ having a crystalline structure having anisotropic nanocrystalline grains MP is manufactured. When the degree of processing (compression rate) by hot plastic working is large, for example, hot plastic working when the compressibility is about 10% or more can be referred to as strong working.

  At the time of hot plastic working, as shown in FIG. 3, the unit body U in which the side surface of the molded body S is surrounded by a frame material with higher ductility is pressed with the upper and lower punches P and P, thereby forming the frame material C and the molded body. Both of the bodies S are crushed while being plastically deformed to the side. However, the plastically deformed molded body S ′ does not lead to excessive plastic deformation to the extent that the frame material C ′ located on the outer periphery thereof is cracked. An oriented magnet S ′ having excellent magnetic anisotropy by plastic deformation to such an extent that the degree can be guaranteed is manufactured.

  This is because the frame material C does not completely surround the molded body S including its upper and lower surfaces, so that the frame material C suppresses excessive plastic deformation to the extent that the molded body S is cracked. This is because the plastic deformation is not excessively constrained by its own structure.

  Further, by pressing the upper and lower punches P and P using the unit body U1 having the upper and lower cover bodies F and F shown in FIG. 4b, the pressing force from the punches P and P is changed to the upper and lower cover materials F and F. Can be applied uniformly to the thickness direction (or height direction) of the molded body S by transmitting it to the molded body S, thereby producing an oriented magnet with a higher degree of orientation. Can do.

[Experiment to verify the relationship between processing rate and degree of orientation and its results]
The inventors of the present invention manufactured oriented magnet test pieces of Example 1 and Comparative Examples 1 to 3 in each manufacturing method shown below, and observed the appearance by taking a photograph of the appearance after hot plastic working, and processing An experiment was conducted to verify the relationship between the rate and the degree of orientation.

(Example 1)
A rare earth alloy raw material (alloy composition is Fe-30Nd-1B-4Co-0.6Ga in mass%) is mixed in a predetermined amount, dissolved in an Ar gas atmosphere, and then the molten metal is subjected to Cr plating from an orifice. An alloy ribbon was produced by injection onto a rotating roll made of metal and quenching, and this was pulverized with a cutter mill in an Ar gas atmosphere and sieved to obtain a rare earth magnet powder of 0.2 mm or less.

  8.4 g of the obtained rare earth magnet powder was placed in a carbide die having a volume of φ10 × 40 mm and sealed with upper and lower carbide punches.

This was set in a chamber, depressurized to 10 ⁻² Pa, and immediately after being loaded with 400 MPa, it was pressed while heating at 650 ° C. with a high-frequency coil. After pressing for 60 seconds, a molded body having a height of 14 mm was taken out of the mold.

  For this molded body, an oxygen-free copper ring with an outer diameter of 12.5 mm, an inner diameter of 10 mm, and a height of 14 mm is fitted into the molded body, the heating temperature is 750 ° C., the processing rate is 60%, 65%, 70%, 75%, It was changed at 80% and hot plastic working was performed at a strain rate of 10 / sec. The punch surface was coated with graphite for lubrication.

(Comparative Example 1)
In the manufacturing method of Example 1, without using a copper ring, an oriented magnet having an outer diameter of 12.5 mm, an inner diameter of 10 mm, and a height of 14 mm was processed at 60%, 65%, 70%, 75%, and 80%. Made by changing.

(Comparative Example 2)
In the manufacturing method of Example 1, without using a copper ring, a copper capsule (carbon steel S25C, φ14 mm x 18 mm) is used to enclose the molded body inside, and hot plastic working is performed under the same conditions. I made an oriented magnet.

(Comparative Example 3)
In the manufacturing method of Example 1, without using a copper ring, a copper capsule (carbon steel S25C, φ11mm × 15mm) is used to enclose the molded body inside, and hot plastic working is performed under the same conditions. I made an oriented magnet. The strain rate is changed at 0.01, 0.1, 1, 10, 30 / sec.

(Evaluation method)
In Example 1 and Comparative Example 1, a test piece of 10 mm × 10 mm × 2.5 mm (thickness) was cut out from the center of the magnet and magnetic measurement was performed. In Comparative Example 1, since a test piece of this size could not be collected due to cracking, it was cut out and measured at a size of 2 × 2 × (1-2) mm (thickness). The measurement results are shown in Table 1 below, and the results of evaluation of the orientation degree Mr / Ms from the MH loop are shown in FIG. Further, a photograph of the oriented magnet of Example 1 after the experiment and a photograph of the oriented magnet of Comparative Example 1 after the experiment are shown in FIGS. 8a and 8b, respectively.

  First, from FIGS. 8a and 8b, in Example 1, although the whole molded body is satisfactorily flattened, cracks cannot be confirmed. On the other hand, in the molded body of Comparative Example 1, many cracks can be confirmed on the outer peripheral portion.

  Also, from Table 1, in Example 1, the higher the processing rate, the higher the Br than in Comparative Example 1. This is considered to be because the degree of orientation Mr / Ms is increased from FIG.

  In Comparative Example 1, strain is released due to cracks generated in the molded body during hot plastic working, and it is considered that anisotropic orientation cannot be sufficiently promoted, while Example 1 has no cracks and is hot. It is considered that the strain at the time of plastic working is sufficiently directed to the anisotropic orientation.

  Further, when Comparative Examples 2 and 3 were compared, Comparative Example 2 was crushed normally, but in Comparative Example 3, the capsule was broken and the magnet slightly protruded from the portion.

  Furthermore, as a result of conducting a cross-sectional investigation on Comparative Example 2, there were many cracks inside the magnet, and it was impossible to cut out a test piece for magnetic measurement. The cause of this crack is thought to be that the magnet could not resist the restraining force due to the thermal contraction of the capsule material during cooling. The thermal expansion coefficient of the magnet is 4 ppm / K, and the capsule (S25C) is 12.2 ppm / K.

  On the other hand, in Comparative Example 3, there was no cracking due to restraint during thermal shrinkage of the capsule, but since the capsule was thin, the capsule was broken by being pulled by the punch surface with little up and down for free elongation. It showed uniform plastic flow. That is, the crystal was not crushed as the processing rate was large, and the degree of orientation was not high (orientation degree 0.86).

[Section observation of the test piece when the thickness of the frame material (ring) was changed, the result, and the result of measuring the magnetic performance]
The inventors of the present invention created a test piece of Example 2 by the following method, and the frame material (ring) used at that time was made of two types, one made of copper and one made of carbon steel (S25C), and A plurality of test pieces were manufactured by varying the wall thickness of each ring, the cross-section was observed, and the magnetization was measured. The results are shown in Table 2 below.

(Example 2)
A rare earth alloy raw material (alloy composition is Fe-30Nd-1B-4Co-0.6Ga in mass%) is mixed in a predetermined amount, dissolved in an Ar gas atmosphere, and then the molten metal is subjected to Cr plating from an orifice. An alloy ribbon was produced by injection onto a rotating roll made of metal and quenching, and this was pulverized with a cutter mill in an Ar gas atmosphere and sieved to obtain a rare earth magnet powder of 0.2 mm or less.

  27.4 g of the obtained rare earth magnet powder was placed in a carbide die having a volume of 15 × 15 × 40 mm and sealed with upper and lower carbide punches.

This was set in a chamber, depressurized to 10 ⁻² Pa, and immediately after being loaded with 400 MPa, it was pressed while heating at 700 ° C. with a high frequency coil. After pressing for 60 seconds, a molded body having a height of 16 mm was taken out of the mold.

  An oxygen-free copper ring with an outer diameter of 12.5 mm, an inner diameter of 10 mm, and a height of 14 mm is fitted into this molded body, and hot plastic working is performed at a heating temperature of 780 ° C, a processing rate of 75%, and a strain rate of 1 / sec. I did it. The punch surface was coated with graphite for lubrication. And the thing made from oxygen-free copper and the thing made from carbon steel (S25C) were used for the frame material (ring), and the thickness of each ring was variously changed between 0.3-4 mm.

  When the material of the frame material (ring) was copper and the wall thickness was 0.75 mm or less, the binding force was too small to confirm the effect on cracking. On the other hand, when the thickness is 3 mm or more, the crystal orientation is disturbed because of resistance to plastic flow, and as a result, Br is low.

  On the other hand, when the material was S25C and the wall thickness was less than 0.5 mm, the strength was insufficient, and when it was 2 mm or more, the magnet was cracked.

  The relationship between the thickness of the frame material, the presence or absence of cracks, and the magnetization is considered to depend on the volume of the molded body, and the frame material is considered to act effectively in the following relationship.

  When the frame material is made of copper or copper alloy and the molded body is a cylindrical body, when the diameter of the molded body is D, a thick frame material of 0.1D to 0.3D is used, and the molded body In the case of a rectangular parallelepiped, a thick frame material of 0.1 L to 0.3 L is used, where L is one side in the extending direction of the molded body.

  On the other hand, when the frame material is made of mild steel and the molded body is a cylindrical body, when the diameter of the molded body is D, a frame material with a thickness of 0.05D to 0.15D is used, and the molded body is In the case of a rectangular parallelepiped, a thick frame material of 0.05 L to 0.15 L is used, where L is one side in the extending direction of the molded body.

[Experiment to confirm the effect when the molded body is surrounded by a frame material and a lid material cut into a frame material and its results]
The inventors further manufactured each test piece of Example 3, Example 1 ′, and Example 4 below, and for Example 3, hot plastic working was performed using a 1 mm-thick lid material. With respect to the test piece, the powder processing rate was measured for each distance from the upper surface of the test piece (the surface that was in close contact with the upper lid material). FIG. 9A is a diagram showing experimental results, and FIG. 9B is an external view photograph of Example 3.

  In addition, the test piece of Example 3 cut out 5 types of samples at 10 mm × 10 mm × 0.2-3 mm from the center, and each test piece of Example 1 ′ and Example 4 was 10 mm × 10 mm × 1 mm from the center. Samples were cut out and their magnetizations were measured. FIG. 10 shows the magnetization measurement result.

(Example 3)
A rare earth alloy raw material (alloy composition is Fe-30Nd-1B-4Co-0.6Ga in mass%) is mixed in a predetermined amount, dissolved in an Ar gas atmosphere, and then the molten metal is subjected to Cr plating from an orifice. An alloy ribbon was produced by injection onto a rotating roll made of metal and quenching, and this was pulverized with a cutter mill in an Ar gas atmosphere and sieved to obtain a rare earth magnet powder of 0.2 mm or less.

  8.4 g of the obtained rare earth magnet powder was placed in a carbide die having a volume of φ10 × 40 mm and sealed with upper and lower carbide punches.

This was set in a chamber, depressurized to 10 ⁻² Pa, and immediately after being loaded with 400 MPa, it was pressed while heating at 650 ° C. with a high-frequency coil. After pressing for 60 seconds, a molded body having a height of 14 mm was taken out of the mold.

  An oxygen-free copper ring with an outer diameter of 12.5 mm, an inner diameter of 10 mm and a height of 14 mm is fitted into the molded body, and the thickness T1 is 0.3, 0.5, 1, 2, and 3 mm with a diameter of 14 mm above and below the molded body. A copper plate was installed, and hot plastic working was performed at a heating temperature of 750 ° C., a processing rate of 75%, and a strain rate of 10 / sec.

(Example 1 ')
In Example 3, hot plastic working was performed without using a copper plate.

(Example 4)
In Example 3, hot plastic working was performed using a mild steel plate (SS41, plate thickness T1 = 1 mm) instead of the copper plate.

  First, FIG. 9b is an external view photograph of Example 3, and due to the large plastic deformation caused by processing the copper plate at 750 ° C., the overall shape of the internal molded body is not a bulge due to a lubricating effect, but a cylindrical shape. It can be confirmed that it is deformed.

  Further, from FIG. 9a, it is proved that in Example 3, the magnet powder is uniformly deformed in the thickness direction of the molded body due to the lubricating effect by the copper plate.

  Furthermore, as shown in FIG. 10, when the thickness of the plate material is in the range of 0.5 to 2 mm, the molded body is crushed over the entire width direction of the molded body (because the distortion in the vicinity of the punch is large). It is considered that the crystal is oriented and Br is large. It has been confirmed that if the plate material is too thick, the surface thereof is excessively stretched and cracks in the vertical direction are generated on the surface. On the other hand, when there is no plate material or iron that is not as soft as copper, the lubrication effect cannot be expected, deformation near the punch is reduced, and orientation does not advance at that location, indicating that there is little improvement in magnetization. It was.

  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, S '... Oriented magnet (rare earth magnet), C ... Frame material, F ... Lid Material, U, U1 ... Unit body, MP ... Main phase (nanocrystal grains, crystal grains), BP ... Grain boundary phase

Claims (1)

A first step of producing a molded body having an upper surface, a lower surface and a side surface by pressure-molding a powder to be a rare earth magnet material;
A frame material having a ductility relatively higher than that of the molded body is arranged on the side surface of the molded body, and further, two frames having a ductility relatively higher than that of the molded body and edged with the frame material. The lid material is arranged on the upper surface and the lower surface of the molded body, respectively, to form a unit body composed of a frame material and a lid material whose side surfaces and upper and lower surfaces are mutually cut off, and a molded body surrounded by these. A second rare earth magnet that is an oriented magnet is manufactured by sandwiching with punches and applying anisotropy while pressing the upper and lower lids positioned on the upper and lower surfaces of the compact with the upper and lower punches. A method for producing a rare earth magnet comprising steps.

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