JP2015123463A - Forward extrusion forging device and forward extrusion forging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forward extrusion forging device which can manufacture a rare earth magnet excellent in a magnetic property without causing a rise of a manufacturing cost due to a simple shape of a hollow part of a die, and a forward extrusion forging method.SOLUTION: A die 1 constituting a forward extrusion forging device 10 is formed of a first region 2 in which a punch 6 slides, a bent part 3, and a second region 4. The punch 6 slides in the first region 2, and a work W is extruded to the second region 4, and forged. Shapes of the first region 2 and the second region 4 which are orthogonal to each other in an extrusion direction are rectangular, and when two sides constituting a rectangular cross section of the first region 2 are set as a first side 2a (length t1) and a second side 2b (length t2), and a side corresponding to the first side 2a out of the two sides constituting a rectangular cross section of the second region 4 is set as a third side 4a (length t3), and when a side corresponding to the second side 2b is set as a fourth side 4b (length t4), at least either of t3>t1 and t4>t2 is satisfied.

Description

  The present invention relates to a forward extrusion forging device and a forward extrusion forging method.

  There are two major forms of hot forging. One of the processing methods is to house the contents in a die, press the contents with an extrusion punch having a hollow, and reduce the thickness to extrude a part of the contents into the hollow of the extrusion punch to produce a molded body. This is a processing method, which is based on a so-called backward extrusion process (a method of manufacturing a molded body while extruding the contained material in a direction opposite to the extrusion direction of the punch). On the other hand, another processing method is to store the contents in a hollow die and press the contents with a punch that does not have a hollow to reduce the thickness of the contents while removing a part of the contents from the hollow of the die. This is a processing method for producing a molded body by extrusion, and is based on a so-called forward extrusion process (a method for producing a molded body while extruding the contained material in the extrusion direction of the punch).

  By the way, 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 in driving 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 magnetic properties of the magnet under high temperature use is one of the important research subjects in the technical field.

  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 or eliminate the addition of heavy rare earth elements while miniaturizing the crystal grains described above are currently attracting attention.

  An example of a method for producing a rare earth magnet is outlined below. For example, a fine powder obtained by rapid solidification of a Nd-Fe-B metal melt is pressed into a rare earth magnet precursor (sintered body). In general, a method of producing a rare earth magnet (orientated magnet) by performing hot plastic working to give magnetic anisotropy to a bonded body is applied.

  In this hot plastic working, the above-described forward extrusion and backward extrusion are applied. More specifically, in the backward extrusion process, a sintered body is accommodated in a die, extruded and pressurized by an extrusion punch having a hollow, and a rare earth magnet is manufactured while extruding the sintered body in a direction opposite to the extrusion direction. . On the other hand, in the forward extrusion process, the sintered body accommodated in the die is pressed with a punch that does not have a hollow, and a part of the sintered body is extruded from the hollow of the die to produce a rare earth magnet. In any of the extrusion methods, anisotropy occurs in the direction perpendicular to the pressing direction of the punch in the rare earth magnet formed by pressing with the punch.

  Thus, in the presence of a plurality of types of extrusion methods, the forward extrusion method is taken up and problems in the conventional processing method are described.

  A conventional forward extrusion processing apparatus has a hollow, in which a die as a component thereof extends in one extrusion direction, and the sintered body accommodated in the hollow is forged by being extruded in one direction by a punch. It has become so. Further, as a modification of this forward extrusion process, there is a processing method in which the extrusion direction changes to a right angle in the middle and the workpiece is extruded through a hollow where there is no change in the cross-sectional dimension to give a shear deformation. This is called the CAP method.

  On the other hand, in Patent Document 1, there is a disclosure of a front extrusion processing apparatus forging by extruding a sintered body accommodated in the hollow of a die in one direction with a punch, but the hollow cross-sectional shape disclosed here is The cross-sectional width of one perpendicular (cross-sectional width in the Y direction) is widened, and the other cross-sectional width (cross-sectional width in the X direction) is constricted in a curved manner. That is, it is an apparatus in which the hollow cross-sectional dimension changes midway.

  Thus, since the opening cross section of the die of the forward extrusion processing apparatus disclosed in Patent Document 1 has a complicated shape in which a part of the hollow cross section is narrowed by a curve, the apparatus can be manufactured. It is difficult and it is easy to understand that the device manufacturing cost is high. Further, when the thickness of the rare earth magnet after forward extrusion changes with respect to the initial thickness of the sintered body, the change in the thickness of the sintered body is also 3 because the hollow cross section has a three-dimensionally complicated shape. Since it changes in a dimensional complexity, it is extremely difficult to design changes in thickness and processing rate when changing from a sintered body to a rare earth magnet.

JP 2008-91867 A

  The present invention has been made in view of the above problems, and a hollow formed in a die has a simple cross-sectional shape, so that a manufacturing cost does not become expensive and a rare earth magnet excellent in magnetic properties is obtained. An object is to provide a forward extrusion forging device that can be manufactured and a forward extrusion forging method using the forging device.

In order to achieve the above object, a forward extrusion forging device according to the present invention is a forward extrusion forging device comprising a die having a hollow and bending, and a punch sliding in the die, wherein the die is a punch. And a second region located in the forward direction of the first region with respect to the first region via the bent portion, and the work is accommodated in the first region, the first region The punch slides in the area of, and the workpiece is extruded into the second area and forged, and the shape of the cross section perpendicular to the extrusion direction of the first area and the second area is both rectangular. And two orthogonal sides constituting the rectangle of the cross section of the first region are defined as a first side (length t1) and a second side (length t2), respectively, and the cross section of the second region Of the two orthogonal sides constituting the rectangle, the side corresponding to the first side is the third side (length t3). Upon the side corresponding to the second side and the fourth side (length t4),
It satisfies at least one of t3> t1 and t4> t2.

  The forward extrusion forging device of the present invention has mainly two features. The first feature point is that, unlike the conventional apparatus, a die which is a component thereof is bent, and the first region where the punch slides, and the first region via the bent portion. This is a point in which a die is formed from the second region located forward in the extrusion direction. In addition to the fact that the cross-sectional shapes of the first area and the second area of the dice are both simple rectangles, the second feature point is that two orthogonal sides constituting the rectangular cross section of the first area are defined. The first side (length t1) and the second side (length t2), and the two orthogonal sides constituting the rectangular cross section of the second region are the third side (length t3) and the fourth side. (Length t4) is that at least one of t3> t1 and t4> t2 is satisfied. According to the forging device having a die having two features as described above as a constituent element, the manufacturing cost of the device does not increase because the sectional shape of the opening formed in the die is a simple rectangle. Furthermore, in the case of a sintered body in which the work housed in the die is a rare earth magnet precursor, a shearing force is applied to the sintered body in the process of passing through the bent portion of the opening, and shear strain is introduced, In the second region of the die, which is ahead of the bent portion in the extrusion direction, each crystal of the sintered body extruded by having at least a portion relatively expanded as compared with the first region has a high degree of orientation. It will have and have. Therefore, it is possible to manufacture a rare earth magnet having high magnetic properties, particularly high remanent magnetization.

  In this specification, “the cross section is rectangular” means that the shape of the cross section perpendicular to the extrusion direction of the first region and the second region is not only rectangular but also square.

  Also, “t3> t1, t4> t2 is satisfied” means that t3> t1 and t4> t2, t3> t1 and t4 = t2, t3> t1 and t4 <t2 It is a meaning including. That is, if the corresponding size relationship between the lengths of the third and first sides satisfies t3> t1, the size relationship between the other corresponding lengths of the fourth and second sides is t4 <t2. The relationship may be

  For example, when the side extending in the horizontal direction of the second region of the die is the third side and the side orthogonal to this and extending in the vertical direction is the fourth side, the length t3 of the third side is Is longer than the length t1 of the first side of the first region corresponding to (t3> t1), and the length t2 of the second side is the same as the length t4 of the fourth side (t4 = t2). In this case, the length in the height direction (that is, the thickness) of the sintered body extruded forward from the first region to the second region does not change, and changes from the length t1 to the length t3 only in the width direction. For this reason, the flat crystals constituting the sintered body that has received shearing force at the bent portion and introduced shear strain and moved to the second region are aligned in the horizontal direction in the cross section of the second region, and therefore The crystals are aligned in the vertical direction. In the case of this embodiment, when a rare earth magnet is produced from a sintered body by forward extrusion, the thickness of the sintered body and the rare earth magnet does not change, only the width changes and the crystal orientation is aligned. Therefore, it is preferable because the parameters required for product design are reduced and the product design is facilitated.

  Regarding the “bending” of the die, the extruding direction in the second region with respect to the extruding direction in the first region includes a range of greater than 0 degrees and less than 180 degrees, but is preferably 90 degrees or less. Preferably, it is 10 to 30 degrees, for example, about 20 degrees.

  When the punch slides in the first area and pushes out the work housed in the first area, the pushing may be in the form of a manual as well as an actuator such as a motor or a cylinder mechanism.

  Further, in a preferred embodiment of the forward extrusion forging device according to the present invention, the side of the first region corresponding to the side having a relatively long length in the second region is bent from the middle position of the first region. It gradually increases over the part.

  In the case where the workpiece is a sintered body, for example, when the length suddenly increases from the length t1 to the length t3 through the bent portion from the first side of the first region to the third side of the second region. It is assumed that it is actually difficult for the crystals of the sintered body that has received a shearing force at the bent portion to have the desired crystal orientation.

  Therefore, for example, when the lengths t2 and t4 of the second side and the fourth side do not change and only the length of the third side changes from the first side, the first region is illustrated. The die is designed so that the first side gradually increases from the middle position to the bent portion, and becomes the same length as the length t3 of the third side at the bent portion. As a result, when the sintered body moves from the first region to the second region, the width of the sintered body gradually increases in the direction along the first side from the middle of the first region, and the bent portion The shearing strain is introduced by receiving the shearing force at, and the sintered body moves to the second region with the third side length t3 already provided, so that the orientation of each crystal is executed smoothly. Will be.

  If t3> t1 and t4> t2, in the first region, both the first side and the second side gradually increase toward the bent portion. Further, if t3> t1 and t4 <t2, in the first region, the first side gradually increases toward the bent portion, and the second side gradually decreases toward the bent portion. .

  The present invention also extends to a forward extrusion forging method. This forging method is a forward extrusion forging method for producing a forged product using a forward extrusion forging device, and is a die that has a hollow and is bent. And a forward extrusion forging device comprising a punch that slides in the die, and the die is positioned forward in the extrusion direction from the first region through the bent portion and the first region in which the punch slides. The second region, the workpiece is accommodated in the first region, the punch slides in the first region, the workpiece is extruded into the second region and forged. In addition, the shape of the cross section orthogonal to the extrusion direction of the first region and the second region is both a rectangle, and two orthogonal sides constituting the rectangle of the cross section of the first region are respectively the first side (long T1), the second side (length t2), and the cross section of the second region Of the two orthogonal sides constituting the rectangle, the side corresponding to the first side is the third side (length t3), and the side corresponding to the second side is the fourth side (length t4). The first step of preparing a forward extrusion forging device satisfying at least one of t3> t1 and t4> t2, when the work is housed in a die, the punch is slid to forge the work It consists of the 2nd step which manufactures.

  The forward extrusion forging method of the present invention is a forging method using the forward extrusion forging device described above, has a bent portion, has a rectangular cross-sectional shape before and after bending, and is at least one of t3> t1 and t4> t2. Extrusion forging using a forward extrusion forging machine equipped with a die that satisfies the requirements, and when the workpiece is a sintered body of a rare earth magnet precursor, it has excellent magnetic properties due to a high degree of orientation Rare earth magnets can be manufactured.

  Here, the rare earth magnet to be manufactured by the forging method of the present invention includes not only nanocrystalline magnets having a grain size of the main phase (crystal) constituting the structure of about 200 nm or less, but also those having a grain size of 300 nm or more. Furthermore, a sintered magnet having a grain size of 1 μm or more, a bonded magnet in which crystal grains are bonded with a resin binder, and the like are included. Above all, the size of the main phase of the magnetic powder before the hot plastic working is such that the average maximum size (average maximum particle size) of the main phase of the rare-earth magnet finally produced is about 300 to 400 nm or less. It is desirable that it is adjusted.

  An example of a method for producing a rare earth magnet is to produce a quenched ribbon (quenched ribbon), which is a fine crystal grain, by liquid quenching, and coarsely pulverize it to produce a magnetic powder for a rare earth magnet. For example, an isotropic sintered body is obtained by filling the inside of a die and sintering it while pressing with a punch to achieve bulking.

  This sintered body is, for example, a RE-Fe-B main phase (RE: at least one of Nd and Pr, more specifically one or two of Nd, Pr, and Nd-Pr with a nanocrystalline structure. And a metal structure composed of a grain boundary phase of the RE-X alloy (X: metal element) around the main phase.

  In the second step, the sintered body described above is accommodated in the apparatus, and hot extrusion forging (hot plastic working) giving magnetic anisotropy is performed to produce a rare earth magnet as an oriented magnet.

  As can be understood from the above description, according to the forward extrusion forging device and the forward extrusion forging method of the present invention, the sintered body, which is a rare earth magnet precursor accommodated as a workpiece at the bent portion of the die constituting the device, is sheared. Since the crystals constituting the extruded sintered body are aligned with a high degree of orientation in the second region of the die that is in front of the bending portion in the extruding direction from the bent portion, a rare earth magnet having a high residual magnetization is obtained. Can be manufactured.

(A) is the longitudinal cross-sectional view which showed Embodiment 1 of the forward extrusion forging apparatus of this invention, (b) is a bb arrow line view of (a). (A) is the longitudinal cross-sectional view which showed the condition where the sintered compact which is a workpiece | work is forward extrusion forged in Embodiment 1 of a forward extrusion forging apparatus, (b) is the bb arrow of (a). FIG. (A), (b) is the longitudinal cross-sectional view which showed Embodiment 2, 3 of the forward extrusion forging apparatus. (A) is a figure explaining the microstructure of a sintered compact, (b) is a figure explaining the microstructure of the rare earth magnet. It is the figure which showed the CAE analysis result which specified the dimensional change when a workpiece | work transferred to the 2nd area | region from the 1st area | region.

  Hereinafter, embodiments of the forward extrusion forging device and the forward extrusion forging method of the present invention will be described with reference to the drawings.

(Embodiment of forward extrusion forging device)
1a and 1b are longitudinal sectional views showing Embodiment 1 of a forward extrusion forging device according to the present invention. The forging device 10 shown in the figure includes a die 1 having a hollow 5, a punch 6 that is slidable (in the X1 direction) within the hollow 5 in the first region 2 of the die 1, and an actuator (not shown) that slides the punch 6. Or a heating means (not shown) for heating the die 1 during forging.

  The die 1 has a first region 2 having a longitudinal direction L1 (work extruding direction) in the vertical direction, and is bent at an angle θ1 (= 90 degrees) with respect to the first region 2, and the longitudinal direction L2 in the horizontal direction. It is comprised from the 2nd area | region 4 which has (work extrusion direction), and the bending part 3 which connects the 1st area | region 2 and the 2nd area | region 4. FIG.

  A workpiece (not shown) accommodated in the hollow 5 is pushed forward of the hollow 5 by a punch 6 that slides in the hollow 5 along the inner peripheral surface of the first region 2 located behind the workpiece. It is extruded to the second region 4 through the bent portion 3 and forged.

In both the first region 2 and the second region 4, the cross-sectional shape orthogonal to the longitudinal direction is a rectangle, and in the longitudinal cross-sectional view of the die 1 shown in FIG. Is one side (second side 2b) having a length t2, and one side (fourth side 4b) constituting the rectangular cross section of the second region 4 has a length t4. Further, in the longitudinal sectional view of the die 1 shown in FIG. 1b as viewed from the front, the other side (first side 2a) constituting the rectangular cross section of the first region 2 has a length t1, and the second region 4 The other side (third side 4a) constituting the rectangular cross section has a length t3.
In the illustrated example, the relationship is t3> t1, t4 = t2.

  However, in the forging device of the present invention, at least one of t3> t1 and t4> t2 is set on the third side 4a corresponding to the first side 2a and the fourth side 4b corresponding to the second side 2b. If it is satisfied, the effect of the forging device of the present invention is exhibited. Therefore, a form of t4> t2 when t3> t1, a form of t4 = t2 when t3> t1, a form of t4 <t2 when t3> t1, and the like may be used.

  However, in the form having a relationship of t3> t1 and t4 = t2 as in the illustrated example, for example, when the workpiece to be extruded and forged is a sintered body that is a rare earth magnet precursor, sintering is performed by forward extrusion. When the body is extruded from the first region to the second region through the bend, the width of the sintered body and the rare earth magnet does not change (because t4 = t2), only the thickness changes and the crystal orientation changes. Will be aligned. Therefore, it can be said that this is a preferred embodiment because the parameters required for product design are reduced and product design is facilitated.

  Further, in the illustrated die 1, the first side 2 a in the first region 2 corresponding to the third side 4 a having a relatively long length in the second region 4 is the first region 2. A gradually increasing portion 2 ″ that gradually increases from the midway position 2 ′ to the bent portion 3 is provided.

  As shown in FIG. 2, for example, in the case where the workpiece W is a sintered body, for example, abruptly passing through the bent portion 3 from the first side 2 a of the first region 2 to the third side 4 a of the second region 4. When the length t1 is increased from the length t1 to the length t3, it is assumed that it is actually difficult to achieve the desired orientation of each crystal of the sintered body that has received the shearing force S at the bent portion 3. . Therefore, the first side 2a is gradually increased from the middle position 2 ′ of the first region 2 to the bent portion 3, and the die 1 is set to have the same length as the length t3 of the third side 4a at the bent portion 3. Design it. Thus, when the sintered body moves from the first region 2 to the second region 4, the width of the sintered body gradually increases from the middle of the first region 2 in the direction along the first side 2a. The sintered body is transferred to the second region 4 in a state where the shearing force is introduced by receiving the shearing force at the bent portion 3 and the length t3 of the third side 4a is already provided. The orientation is smoothly executed.

  In FIG. 2b, the horizontally long and flat crystals constituting the rare earth magnet that has been forward-extruded forged and extruded into the second region have their longitudinal directions aligned in the direction along the third side 4a, and are therefore oriented. Are aligned in the direction of the fourth side 4b.

  3a and 3b are longitudinal sectional views showing Embodiments 2 and 3 of the forward extrusion forging device. A forging device 10A shown in FIG. 3a includes a die 1A in which an angle θ2 of the second region 4A passing through the bent portion 3 with respect to the first region 2 is less than 90 degrees, and the forging device 10B shown in FIG. An angle θ3 of the second region 4B that has passed through the bent portion 3 with respect to the first region 2 is greater than 90 degrees and includes a die 1B that is less than 180 degrees.

  As described above, the forward extrusion forging device of the present invention is configured such that when the workpiece passes through the bent portion, the component die is bent at an intermediate position at an angle greater than 0 degrees and less than 180 degrees. A shear force can be applied to the workpiece to introduce a shear strain. Furthermore, the workpiece is configured so that at least one of the two sides of the second region corresponding to the two sides constituting the rectangular cross section of the first region is long, so that the workpiece is a rare earth magnet precursor. In the case of a sintered body, the orientation of each crystal constituting the sintered body can be promoted.

  When the workpiece is a sintered body of a rare earth magnet precursor, the microstructure of this sintered body is shown in FIG. 4a. The rare earth magnet is formed by extrusion forging (hot plastic working) in the forging device 10 illustrated in FIG. 4a. The microstructures are shown in FIG.

  As shown in FIG. 4 a, the sintered body has an isotropic crystal structure in which the grain boundary phase BP is filled between the nanocrystalline grains MP (main phase).

  On the other hand, as shown in FIG. 4b, the nanocrystalline grains MP have a flat shape, and the interface substantially parallel to the anisotropic axis is curved or bent, resulting in a rare earth magnet having high magnetic anisotropy. Yes.

(Embodiments of rare earth magnet manufacturing method and forward extrusion forging method)
Next, the manufacturing method of the rare earth magnet will be outlined together with the forward extrusion forging method.
For example, in a furnace not shown in an Ar gas atmosphere reduced in pressure to 50 kPa or less, a melt spinning method using a single roll melts the alloy ingot at high frequency, and a molten metal having a composition giving a rare earth magnet is sprayed onto the copper roll R to rapidly cool the ribbon. (Quenched ribbon) is manufactured and coarsely pulverized.

  Among the coarsely pulverized quenching ribbons, a quenching ribbon having a maximum dimension of about 200 nm or less is selected, and this is defined by a carbide die and a carbide punch that slides in the hollow. Fill inside. The main phase of the Nd-Fe-B system with a nanocrystalline structure (crystal grain size of about 50 nm to 200 nm) and the main phase are heated by applying a current in the pressing direction while pressing with a carbide punch. A square columnar sintered body consisting of the grain boundary phase of Nd-X alloy (X: metal element) around is manufactured.

  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. 4 a, the sintered body exhibits an isotropic crystal structure in which the grain boundary phase BP is filled between the nanocrystalline grains MP (main phase).

  Once the rectangular columnar sintered body is manufactured, it is accommodated in the first region 2 of the die 1 constituting the forward extrusion apparatus 10 shown in FIG. 1, and forward extrusion forging (hot plastic working) is performed here. Magnetic anisotropy is imparted to the sintered body to produce a rare earth magnet (orientated magnet). As shown in FIG. 4b, the rare earth magnet manufactured by hot plastic working consisting of extrusion forging has a flat shape with nanocrystalline grains MP, and the interface substantially parallel to the anisotropic axis is curved or bent. Thus, the rare earth magnet has excellent magnetic anisotropy.

  Regarding the manufactured rare earth magnet, from the grain boundary phase of the RE-Fe-B main phase (at least one of RE: Nd and Pr) and the RE-X alloy (X: metal element) around the main phase It is preferable that the RE content is 29 mass% ≦ RE ≦ 32 mass%, and the average particle size of the main phase of the manufactured rare earth magnet is 300 nm. When the content ratio of RE is within the above range, the effect of suppressing the occurrence of cracks during hot plastic working is even higher, and a high degree of orientation can be guaranteed. In addition, when the RE content is in the above range, the size of the main phase that can guarantee a high residual magnetic flux density can be secured.

  In addition to heavy rare earth metals such as Dy, manufactured rare earth magnets (orientated magnets) do not contain heavy rare earth metals such as Nd-Cu alloy, Nd-Al alloy, Pr-Cu alloy, and Pr-Al alloy. The modified alloy may be a rare earth magnet in which the grain boundary is diffused and the coercive force is further increased. For example, the eutectic temperature of Nd-Cu alloy is about 520 ° C, the eutectic temperature of Pr-Cu alloy is about 480 ° C, the eutectic temperature of Nd-Al alloy is about 640 ° C, and the eutectic temperature of Pr-Al alloy is These modified alloys are particularly suitable when the rare earth magnet is a nanocrystalline magnet, since these modified alloys are much lower than 700 ° C to 1000 ° C, which encourages the coarsening of the crystal grains constituting the nanocrystalline magnet. is there.

(CAE analysis verifying improved magnetic properties and its results)
The present inventors conducted CAE analysis by the following method. That is, a predetermined amount of magnet raw material (alloy composition is Fe-30Nd-0.93B-4Co-0.4Ga in mass%) is melted in an Ar atmosphere, and then the molten metal is rotated from a crucible orifice to a Cu-made rotor. The film was injected into a roll and quenched to produce a quenched ribbon.

This rapidly cooled ribbon is pulverized with a cutter mill in an Ar atmosphere to obtain a rare earth alloy powder of 0.2 mm or less, and then the rare earth alloy powder is put into a mold having a size of 20 × 20 × 40 mm, and the upper and lower carbide punches. Sealed with. Then, it was set in a chamber, depressurized to 10 ⁻² Pa, loaded with 400 MPa, immediately heated to 650 ° C. with a high frequency coil, and pressed. After pressing and holding for 60 seconds, the bulk body was taken out of the mold and used as a test piece for hot working. The test piece was subjected to a compression test at 750 ° C. and a strain rate of 0.01 to 1 / sec. In addition, the obtained material property data is set as INPUT, and CAE analysis is performed on the conventional E-CAP method (however, a bending device is applied in the same manner as the forging device of the present invention) and the forward extrusion forging method of the present invention. Carried out. The magnetic properties were evaluated from the strain distribution obtained by CAE analysis. Furthermore, the dimensional change in the case of the forward extrusion forging method of the present invention was also specified. The analysis results regarding the magnetic characteristics and dimensional changes are shown in Table 1 below, and the dimensional changes are further shown in FIG.

  First, regarding remanent magnetization (Br), it is possible to predict the remanent magnetization by the equivalent plastic strain and the amount of elongation in the length direction of the third side of the second region. I know. From the equivalent plastic strain of the method compared to this time and the amount of elongation in the length direction of the third side of the second region, it is predicted that the conventional E-CAP method is 1.25T and the forging method of the present invention is 1.32T. .

  Next, it is known that the coercive force (Hc) is substantially correlated only with the equivalent plastic strain, and the equivalent plastic strain of the method to be compared this time and the elongation in the length direction of the third side of the second region. From the quantity, it is estimated that the conventional E-CAP method is 15 kOe and the forging method of the present invention is 16 kOe.

  Regarding the dimensional change, in the conventional E-CAP method, there is no change in the cross-sectional dimension even when the first region is moved to the second region through the bent portion, so the first side of the first region is not changed. And the length of the third side of the second region are both 5 mm.

  On the other hand, as shown in FIG. 5, in the forging method of the present invention, the length of the third side of the second region is carried out in the height direction at three points P1, P2, and P3 from above, An average value of 7 mm was obtained.

  Therefore, when 5 mm in the case of the conventional E-CAP method was normalized, the dimensional change rate by the forging method of the present invention was specified as 1.4.

  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.

  DESCRIPTION OF SYMBOLS 1,1A, 1B ... Dies, 2 ... 1st area | region, 3 ... Bending part, 4, 4A, 4B ... 2nd area | region, 5 ... Hollow, 6 ... Punch 10, 10A, 10B ... Forging apparatus (forward extrusion) Forging device), W ... Work (sintered body), MP ... Main phase (nanocrystal grain, crystal grain, crystal), BP ... Grain boundary phase

Claims (5)

A forward extrusion forging device comprising a die having a hollow and bending, and a punch sliding in the die,
The die is composed of a first region in which the punch slides and a second region located in front of the first region through the bent portion in the pushing direction, and the workpiece is accommodated in the first region. , The punch slides in the first region, the workpiece is extruded into the second region and forged,
Both of the cross-sectional shapes orthogonal to the extrusion direction of the first region and the second region are rectangular,
Two orthogonal sides constituting the rectangle of the cross section of the first region are defined as a first side (length t1) and a second side (length t2), respectively.
Of the two orthogonal sides constituting the rectangle of the cross section of the second region, the side corresponding to the first side is the third side (length t3), and the side corresponding to the second side is the fourth side When the side (length t4)
A forward extrusion forging device that satisfies at least one of t3> t1 and t4> t2.   The forward extrusion forging device according to claim 1, wherein a side of the first region corresponding to a side having a relatively long length in the second region is gradually increased from a middle position of the first region to a bent portion. .   The forward extrusion forging device according to claim 1, wherein t3> t1 and t4 = t2. A forward extrusion forging method for producing a forged product using a forward extrusion forging device,
A forward extrusion forging device comprising a die having a hollow and bending and a punch sliding in the die, the die having a first region through which the punch slides and a first region through the bent portion And a second region located in front of the pushing direction, the workpiece is accommodated in the first region, the punch slides in the first region, and the workpiece is pushed into the second region. The cross-sectional shape perpendicular to the extrusion direction of the first region and the second region is both rectangular, and the two orthogonal sides constituting the rectangular shape of the cross-section of the first region Are the first side (length t1) and the second side (length t2), respectively, and the side corresponding to the first side among the two orthogonal sides constituting the rectangle of the cross section of the second region Is the third side (length t3) and the side corresponding to the second side is the fourth side (length t4), t3> t1, t4> t2 A first step of preparing a forward extrusion forging device satisfying at least one of
A forward extrusion forging method comprising a second step of manufacturing a forged product by housing a work in a die and sliding the punch to forge the work. The workpiece is a powder that becomes a rare earth magnet material, which is a RE-Fe-B main phase (at least one of RE: Nd and Pr) and a RE-X alloy (X: metal) around the main phase. Element) is a sintered body obtained by pressure molding a powder composed of a grain boundary phase,
The forward extrusion forging method according to claim 4, wherein the forward extrusion forging is used to produce a rare earth magnet which is a forged product by subjecting the sintered body to hot plastic processing which gives anisotropy.

Images