JP2018113348A - Manufacturing method of r-t-b type rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an R-T-B type rare earth magnet with high material yield and excellent productivity.SOLUTION: A manufacturing method of an R-T-B type rare earth magnet includes a laminating step of laminating a plurality of preforms 10 made of an R-T-B type rare earth magnet material to form a raw material laminate 1, a hot working step of performing hot working on the raw material laminate 1 to form a processed laminate, and a dividing step of dividing the processed laminate in a position corresponding to the interface between the plurality of preforms 10 constituting the raw material laminate 1 to obtain a plurality of R-T-B type rare earth magnets.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing an R-T-B system rare earth magnet, and more particularly to a manufacturing method for manufacturing a plurality of R-T-B system rare earth magnets through hot working.

  When manufacturing a metal magnet typified by a rare earth magnet, hot working such as hot extrusion can be performed to shape the metal magnet into a desired shape and to impart magnetic anisotropy. For example, in Patent Document 1, (a) a step of melting and casting an alloy to be a rare earth magnet, (b) a step of charging and sealing the cast alloy so as to be in direct contact with an iron-based metal capsule, (c) A rare earth permanent magnet having a step of hot working the capsule, (d) a step of heating and cooling the capsule, (d) a step of removing the cast alloy and heat-treating, and (f) a step of cutting and polishing into a desired shape. A manufacturing method is disclosed.

  When a large number of individual RTB system rare earth magnets are manufactured through hot processing, a large RTB system rare earth magnet is manufactured by hot processing and then divided into a large number by cutting. It is common to do. In the case of the example of Patent Document 1, the material is divided into a plurality of individuals in the step (f) of cutting into a desired shape to obtain a large number of individuals.

JP-A-8-273961

  When a large R-T-B rare earth magnet is manufactured and a large number of solids are obtained by cutting, a material loss (kerfloss) is generated along with the cutting. In particular, when cutting a thin large R-T-B rare earth magnet, the greater the thickness of the cutting blade used for cutting, the larger the kerf loss and the lower the material yield.

  In addition to cutting a large plate material, as a method for producing a small thin plate-shaped RTB-based rare earth magnet, a method of sintering using a sintering mold matched to the thin plate shape is conceivable. Alternatively, a method of performing hot extrusion using a small-diameter punch and a die matched to a thin plate shape can be considered. However, in any case, due to the thinness of the RTB-based rare earth magnet to be manufactured, the molded body is likely to be warped or cracked due to temperature variations during processing and wear of the mold or die. . Therefore, these methods have low productivity and are practically difficult to apply to mass production of a large number of individuals.

  The problem to be solved by the present invention is to provide a method for producing an RTB-based rare earth magnet having a high material yield and excellent productivity.

  In order to solve the above-mentioned problems, the manufacturing method of the RTB-based rare earth magnet according to the present invention includes a stacking step in which a plurality of preforms made of an RTB-based rare earth magnet material are stacked to form a raw material stack. And hot working on the raw material laminate, a hot working step to be a processed laminate, and a position corresponding to an interface between the plurality of preforms constituting the raw material laminate, Splitting the processed laminate to obtain a plurality of R-T-B rare earth magnets. However, R is at least one rare earth element including Y, and T is obtained by replacing Fe or a part of Fe with Co.

  Here, it is good to have the division | segmentation adjuvant supply process which supplies the division | segmentation adjuvant which accelerates | stimulates the division | segmentation of the said process laminated body in the said division | segmentation process to the interface between the some preforming body which comprises the said raw material laminated body. In this case, the splitting aid may contain graphite powder. In the raw material laminate, a notch may be provided continuously at the interface between the plurality of preforms.

  In the hot working step, compressive stress may be applied to the raw material laminate along the lamination direction of the preform. In this case, the preform is a plate-like body, and in the stacking step, the preform is preferably laminated along the thickness direction of the plate-like body. Alternatively, in the hot working step, compressive stress may be applied to the raw material laminate along a direction intersecting the lamination direction of the preform.

  The preform may be formed through a cold pressing step in which a cold pressed body is obtained from the powder of the R-T-B rare earth magnet material by cold pressing. In this case, it is good also as the said preforming body through the hot press process which hot-presses with respect to the said cold press body. That is, you may perform the said hot press process with respect to the said cold press body between the said cold press process and the said lamination process. Or it is good also as the said raw material laminated body through the hot press process which hot-presses with respect to the laminated body of the preforming body which consists of the said cold press body. That is, you may perform the said hot press process with respect to what laminated | stacked the said cold laminated body between the said lamination process and the said hot working process.

  The RTB-based rare earth magnet obtained through the dividing step may be a thin plate having a thickness of 6 mm or less.

  In the method for producing an R-T-B rare earth magnet according to the invention, after hot working in a state where a plurality of preforms are laminated, the position corresponding to the interface between the original preforms Thus, the method of dividing the laminated body into individual pieces is taken, and it is not divided into individual pieces by cutting a large processed body formed integrally. Therefore, the loss of the material unavoidable in the cutting process does not occur, and the method is excellent in material yield. In addition, productivity can be improved by performing hot working of a plurality of individual objects at the same time, and a plurality of preforms can be stacked even when a thin plate-like RTB rare earth magnet is manufactured. In addition, since the hot working is performed with the laminated body having a certain thickness, it is easy to avoid a decrease in productivity due to the thinness of the material, such as warping and cracking.

  Here, in the case of having a split auxiliary agent supplying step for supplying a split auxiliary for promoting the division of the processed laminate in the split step at the interface between the plurality of preforms constituting the raw material laminate, the split step It becomes possible to easily divide the processed laminated body. The dividing auxiliary agent supplying step may be performed before the laminating step or may be performed simultaneously with the laminating step. As a result of passing through the dividing auxiliary agent supplying step, it is possible to suppress the occurrence of chipping and cracking accompanying the division.

  In this case, if the splitting aid contains graphite powder, splitting of the processed laminate in the splitting process can be promoted particularly effectively.

  Alternatively, in the raw material laminate, in the case where a notch is provided continuously at the interface between the plurality of preforms, by dividing the processed laminate from the notch in the dividing step, The division becomes easy, and it becomes easy to suppress the occurrence of chipping and cracking accompanying the division. In particular, in the hot working process, when compressive stress is applied to the raw material laminate along the direction crossing the lamination direction of the preform, the effect of facilitating division by notches is greatly obtained.

  In the hot working step, when compressive stress is applied to the raw material laminate along the lamination direction of the preform, hot working to reduce the thickness is effectively performed on a plurality of preforms. It can be carried out.

  In this case, the preform is a plate-like body, and in the laminating step, according to the configuration in which the preform is laminated along the thickness direction of the plate-like body, the thin plate-like RTB system is used. A plurality of rare earth magnets can be manufactured simultaneously. When the R-T-B rare earth magnet to be manufactured is in the form of a thin plate, the effects of material loss due to cutting of a large thin plate material, and a decrease in productivity due to warpage and cracking during processing become particularly large. Therefore, the effect of improving the material yield and improving the productivity by using a manufacturing method in which a plurality of preforms are laminated and then hot-worked and then divided is particularly increased.

  In addition, in the hot working process, when compressive stress is applied to the raw material laminate along the direction intersecting the lamination direction of the preform, the width and length are reduced with respect to the plurality of preforms. Hot working can be performed effectively.

  When a preform is formed through a cold pressing process in which a cold pressed body is obtained from a powder of an R-T-B rare earth magnet material by cold pressing, the preformed body is formed and hot worked. It can be performed simply. In addition, an RTB-based rare earth magnet having high magnetic anisotropy and excellent magnetic properties can be produced. In addition, a cold press process can be performed at atmospheric temperature (5 degreeC-35 degreeC), for example.

  In this case, the density of the preform can be increased in advance before hot working by further performing a hot pressing process for performing hot pressing, and the R having excellent magnetic properties can be obtained through hot working. A -T-B rare earth magnet can be obtained. By performing the hot pressing step between the cold pressing step and the laminating step, in the hot pressing step, the preform is in a state having a predetermined shape such as a straight edge, and in the laminating step The preform can be stacked in an orderly manner. Thereby, an RTB-based rare earth magnet having high dimensional accuracy can be obtained through hot working. This effect is particularly significant when compressive stress is applied to the raw material laminate along the direction intersecting the lamination direction of the preform. In addition, a hot press process can be performed at 600 to 850 degreeC, for example.

  Alternatively, according to the configuration in which the hot pressing process is performed between the laminating process and the hot working process, not only the hot working process but also the hot pressing process is performed simultaneously on a plurality of individuals. An RTB-based rare earth magnet can be manufactured with high efficiency.

  When the R-T-B rare earth magnet obtained through the splitting process is in the form of a thin plate having a thickness of 6 mm or less, the material yield is improved by eliminating the cutting process, and the thickness of the entire raw material laminate is given. In particular, the effect of improving the productivity by performing hot working is increased.

It is a perspective view which shows the outline of a hot working process about the manufacturing method of the RTB system rare earth magnet concerning one Embodiment of this invention. Each figure of (a)-(c) is different in the lamination direction and compression direction of a preforming body, and represents the 1st form, the 2nd form, and the 3rd form, respectively. It is a figure which shows the structure which provides a notch in a raw material laminated body, and has shown the state of the side surface at the time of laminating | stacking a preforming body in the width direction.

  Below, the manufacturing method of the RTB system rare earth magnet concerning one embodiment of the present invention is explained in detail, referring to drawings.

[Outline of Manufacturing Method of R-T-B Rare Earth Magnet]
The manufacturing method of the RTB system rare earth magnet concerning one embodiment of the present invention manufactures a plurality of RTB system rare earth magnets simultaneously.

In the manufacturing method according to the present embodiment, the following steps are performed.
(1) Preliminary body preparation step (2) Lamination step (3) Hot working step (4) Division step

[Details of each process]
Hereinafter, the steps (1) to (4) described above will be described in order.

(1) Preliminary body preparation process In a preliminary body preparation process, the preform 10 as a raw material used for hot working is prepared.

  The preform 10 is made of an R-T-B rare earth magnet material. Here, R is at least one rare earth element containing Y, and T is Fe or a part of Fe substituted with Co. As a specific RTB system rare earth magnet, an Nd-Fe-B system magnet can be exemplified. The preform 10 may appropriately include a material other than the RTB-based rare earth magnet, such as a binder agent. However, from the viewpoint of magnetic properties, the preform 10 preferably includes only the RTB-based rare earth magnet material. .

  The preform 10 is not particularly limited as long as it can provide magnetic anisotropy by hot working, and a casting ingot obtained by casting as shown in Patent Document 1 and sintering obtained by a sintering method. May be of any shape, such as a body, but from the viewpoint of the simplicity of the pre-formed body preparation step and the subsequent hot working step, etc. It is preferable to use a press body obtained through cold pressing. When magnetic anisotropy is imparted by hot working, it is preferable to use, as a raw material, a powder obtained by a method of manufacturing a ribbon (super quenching method) by super quenching a molten magnet material, for example, It can be a flaky powder composed of amorphous and / or equiaxed grains having a particle size of several tens of nanometers. The size of the powder can be adjusted to a desired size by grinding the ribbon. Hot extrusion is performed on a molded body using such powder. As a result, the anisotropically shaped particles rotate in such a manner that anisotropically shaped particles are generated and / or anisotropically grown in the compact and the easy magnetization axis (c-axis) is parallel to the compression direction. As a result, a hot-worked body in which the axis of easy magnetization of anisotropically shaped grains is oriented in one direction is obtained.

  In the case of preparing the preformed body 10 through the cold pressing process, a mode in which only the cold pressing process is used as the pressing process and the cold pressed body is used as it is as the preformed body 10 can be considered. Or you may further implement the hot press process which hot-presses with respect to a cold press body after a cold press process. By passing through a hot press process, the density of the metal material in the preform 10 can be increased. As a result, the RTB-based rare earth magnet obtained through hot working can be made more excellent in magnetic properties. In addition, a cold press process can be performed at atmospheric temperature (5 degreeC-35 degreeC), for example. Moreover, a hot press process can be performed at 600 to 850 degreeC, for example.

  The outer shape of the preformed body 10 prepared in the preformed body preparing step may be anything. Considering the convenience in orderly laminating a plurality of preforms 10 and the shape desired for an R-T-B rare earth magnet obtained through hot working, as shown in FIG. It is preferable to prepare the molded body 10 in a substantially rectangular parallelepiped shape. Hereinafter, the case where the preform 10 is a rectangular parallelepiped will be described as an example. The direction along the longest side of the rectangular parallelepiped is the longitudinal direction, the direction along the long side is the width direction, and the shortest side is along. The direction is the thickness direction. When the thickness direction is significantly shorter than the longitudinal direction and the width direction, the preformed body 10 takes the form of a plate.

(2) Laminating process In the laminating process, a plurality of preforms 10 prepared in the preformed body preparing process are stacked to form a raw material laminate 1. In this specification, not only the case where a plurality of preforms 10 are stacked in the vertical direction but also the case where a plurality of preforms 10 are arranged in the lateral direction are included in the “lamination”.

  As the plurality of preforms 10 constituting the raw material laminate 1, those having different sizes and shapes may be used, but the laminating step and the subsequent hot working step, the simplicity and productivity of the dividing step, etc. In view of the above, it is preferable to use the same size and shape. And it is preferable to laminate | stack all the preforming bodies 10 mutually in contact with the same orientation.

  What is necessary is just to select the lamination direction of the preforming body 10 in the raw material laminated body 1 according to the shape desired in the R-T-B type rare earth magnet finally obtained, and the direction of the desired magnetic anisotropy. Depending on the combination of the stacking direction of the raw material laminate 1 and the compression direction in the hot working process, the splitting direction in the splitting process and the shape and magnetic anisotropy direction in the R-T-B rare earth magnet are determined. For example, in the example shown in FIGS. 1A and 1C, rectangular parallelepiped (plate-shaped) preforms 10 are stacked in the thickness direction. On the other hand, in the example of FIG. 1B, rectangular parallelepiped preforms 10 are stacked in the width direction.

  What is necessary is just to select suitably the number of lamination | stacking of the preforming body 10 in the raw material laminated body 1 according to the magnitude | size and shape of the preforming body 10, a lamination direction, the kind of processing apparatus which performs hot processing, etc. For example, in terms of enabling sufficient compressive stress to be applied to each preform 10 in the hot working process, and the variation in individual magnetic characteristics in the R-T-B rare earth magnet finally obtained. From the viewpoint of suppression, etc., a mode in which the number of stacked layers is 2 to 6 can be exemplified.

  In the present embodiment, the lamination process is performed after the preform 10 is completed through a cold press process and, if necessary, a hot press process. However, when performing a hot press process, a hot press process may be performed between a lamination process and a hot working process. In this case, a plurality of cold press bodies are hot-pressed at a time in a state where the cold press bodies are laminated in the laminating process, and the process proceeds to the hot working process as it is. By doing in this way, not only a hot working process but a hot press process can be performed efficiently. However, particularly in the embodiment in which compressive stress is applied in the direction intersecting the stacking direction of the preformed body 10 during hot working as in the embodiments of FIGS. 1B and 1C, the hot pressing step and the hot working are performed. It is preferable to perform a lamination process between the processes. By increasing the density of the preformed body 10 by hot pressing, the preformed body 10 can be stacked in an orderly manner, and the dimensional accuracy of the RTB-based rare earth magnet after hot working is increased. It is easy.

(3) Hot working process In a hot working process, hot processing is performed with respect to the raw material laminated body 1 formed at the lamination process, and a process laminated body is formed.

  The type of hot working (hot plastic working) is not particularly limited, but hot extrusion can be mentioned as a suitable one. Starting with a press body, hot extrusion molding is performed by applying a compressive stress in a specific direction to a preformed body 10 made of an R-T-B system rare earth magnet material. High magnetic anisotropy can be imparted to the rare earth magnet. In addition, by compressing the preform 10 in a predetermined direction, an RTB-based rare earth magnet having a desired shape such as a thin plate shape can be obtained. Hereinafter, the case where hot extrusion molding is performed will be described.

  In the hot working step, a plurality of forms of processing can be selected by a combination of a compression direction d for applying a compressive stress to the raw material laminate 1 and a forming direction D corresponding to the direction in which extrusion is performed. Further, the combination of the compression direction d and the forming direction D of the hot working step and the lamination direction of the preform 10 selected in the previous lamination step, and the division direction and division of the processed laminate in the next division step The shape and the direction of magnetic anisotropy in the R-T-B rare earth magnet to be obtained later are defined.

  In FIG. 1, the example about the form of the combination of the compression direction d and the shaping | molding direction D, and the lamination direction of the preforming body 10 is shown. In the first embodiment shown in FIG. 1A, the thickness direction of the preform 10, that is, the material laminate 1 is compared to the material laminate 1 in which the plate-shaped preforms 10 are laminated in the thickness direction. A compression direction d is set along the stacking direction of the preformed body 10 and a molding direction D is set along the longitudinal direction. When forming a cold-pressed body of a rare earth magnet in a plate shape, the thickness direction of the plate is generally an easy axis of magnetization, and as shown in FIG. By applying a compressive stress along the thickness direction of the plate, it is possible to obtain a thin plate-like RTB-based rare earth magnet having high magnetic anisotropy with the thickness direction as the easy axis of magnetization.

  On the other hand, in the second embodiment shown in FIG. 1B, the compression direction along the thickness direction of the preform 10 with respect to the raw material laminate 1 in which the rectangular parallelepiped preforms 10 are laminated in the width direction. The molding direction D is set along the width direction d. In the third embodiment shown in FIG. 1C, the compression direction d is set along the width direction of the preform 10 with respect to the raw material laminate 1 in which the rectangular parallelepiped preforms 10 are laminated in the thickness direction. The molding direction D is set along the longitudinal direction. In the second embodiment and the third embodiment, the compression direction d is set along the direction intersecting the stacking direction of the preform 10. Note that the compression direction d does not have to be only one direction, and can be set as one or a plurality of directions intersecting the forming direction D. When there are a plurality of compression directions d, the direction with the greatest degree of compression is regarded as the main compression direction, and for example, the main compression direction may be selected as one of the above three forms.

  The processed laminated body obtained by performing the hot working process on the raw material laminated body 1 is an R-T-B rare earth magnet in which each preform 10 is compressed and fixed to each other at the interface. . Moreover, the obtained processed laminated body has a dimension in the compression direction d corresponding to the dimension of the die to which the compressive stress is applied by passing during hot working. The degree of compression in the hot working process may be appropriately determined in consideration of the magnetic anisotropy and shape desired in the R-T-B rare earth magnet to be manufactured, but the area reduction rate is 50 to 70%. The form to do can be illustrated.

(4) Division process In a division process, a processing lamination object is divided into a plurality, and a plurality of RTB system rare earth magnets are obtained.

  As described above, the processed laminate obtained in the hot working step is fixed at a position corresponding to the interface between the plurality of preforms 10 constituting the raw material laminate 1 before hot working. Has caused. Therefore, in the dividing step, the processed laminated body is divided into a plurality at a position corresponding to the interface. As a result, a plurality of R-T-B rare earth magnets corresponding to each of the individual preforms 10 can be obtained.

  The direction of division in the division step corresponds to the direction of lamination in the lamination step. That is, when hot working is performed on the first form of FIG. 1A, the processed laminated body is divided in the thickness direction. Then, after the division, a thin plate-like RTB-based rare earth magnet is obtained. When hot working is performed on the second form of FIG. 1B, the processed laminated body is divided along the longitudinal direction. And after division | segmentation, a narrow flat RTB system rare earth magnet is obtained. When hot working is performed on the third form of FIG. 1C, the processed laminated body is divided in the width direction (direction along the processing direction D). After the division, a small R-T-B rare earth magnet having a smaller shape anisotropy than the first and second embodiments can be obtained.

  In each metal material obtained by division, the dimension along the division direction is the dimension obtained by dividing the dimension of the processed laminated body in the lamination direction by the number of laminations if the same preform is used as the plurality of preforms 10. It almost agrees. Furthermore, as in the first embodiment of FIG. 1A, in the hot working process, when compressive stress is applied along the stacking direction, the dimension of the metal material along the compressing direction d is hot working. This is almost the same as the size of the die used for the above divided by the number of layers.

  The processed laminated body can be divided by directly applying a force that separates the two fixed R-T-B rare earth magnets to the interface or applying an impact along the stacking direction. . The latter method is particularly preferable in that the fixation at a plurality of interfaces can be easily eliminated at once.

  Even if hot working is performed, the compacts do not cause fusion at the interface, but are only fixed while maintaining microscopic discontinuities. If this force is appropriately applied, the sticking can be eliminated and the molded body can be divided at each interface. Furthermore, as will be described later, by using application of a dividing aid or formation of a notch, it is possible to assist division and reduce the force required to eliminate sticking.

  As described above, in the manufacturing method according to this embodiment, a plurality of R-T-B rare earth magnets are obtained by performing hot working in a state in which a plurality of preforms 10 are laminated and then performing division. Manufacturing. Since the raw material laminate 1 to be hot-worked is composed of a plurality of preformed bodies 10, even if sticking occurs at the interface of each individual in the hot-working process, cutting using a cutting blade or a cutting tool Without the step, the RTB-based rare earth magnet can be separated again into a plurality of individuals. Thus, by eliminating the step of cutting the metal material, it is possible to eliminate material loss (curfloss) that inevitably occurs with the cutting, and to increase the material yield.

  Moreover, the productivity of the RTB-based rare earth magnet can be increased by performing hot working in a state where the plurality of preforms 10 are laminated. In addition to the fact that a plurality of preforms 10 can be processed by a single hot working, the raw material laminated body 1 as a whole is processed in a state in which a large dimension is secured, thereby processing an individual having a small dimension. This is because the influence that can occur in the event of a failure can be reduced. In particular, as in the first embodiment shown in FIG. 1A, the plate-shaped preform 10 is laminated in the thickness direction, and a compressive stress is applied along the lamination direction to produce a thin plate-like R- When producing a TB-based rare earth magnet, such an effect of improving productivity is greatly obtained. If a thin plate-like RTB-based rare earth magnet is manufactured by hot working one by one on the preformed body 10, RT-T is caused by temperature unevenness or friction with the die. As a result, warping and cracking are likely to occur in the -B-based rare earth magnet, and as a result, the yield rate of the obtained RTB-based rare earth magnet is lowered and productivity is lowered. The same problem can occur when thin metal materials are manufactured one by one by sintering. By performing the hot working in a state where a certain thickness is secured as the entire raw material laminate 1, it is possible to avoid such a decrease in productivity due to the thinness of the work target.

  Furthermore, if hot processing is performed on the preform 10 for each individual, there is a possibility that denaturation, mechanical damage, etc. resulting from the hot processing, such as oxidation, may occur on the surface of each individual. . On the other hand, by performing the hot working by laminating the plurality of preforms 10, it is possible to suppress the influence of them only in the vicinity of the surface of the raw material laminate 1 as a whole. As a result, a high-quality RTB rare earth magnet with little modification and damage can be obtained with a high yield.

  For example, in the case of manufacturing a thin plate-like metal material according to the first embodiment of FIG. 1A, if the thickness of the metal material obtained through the dividing step is 6 mm or less, the material yield can be improved and produced as described above. The effect of improving the properties is particularly large.

[Promoting division in the division process]
As described above, the division of the processed laminate in the dividing step can be performed by applying a force to the processed laminate. However, if the force applied at this time is increased, the R-T-B rare earth magnet may be damaged such as chipping or cracking during the division. Since rare earth magnets are hard and brittle, it may be difficult to divide in a predetermined direction, and damage due to the division is likely to occur. Therefore, it is preferable to reduce the force required for division.

  One way to reduce the force required for splitting is to use a splitting aid. In the raw material laminate 1 before hot working, a dividing aid may be disposed at the interface between the preforms 10. The dividing auxiliary agent supplying step of arranging the dividing auxiliary agent at the interface of the preform 10 can be performed before the laminating step. In this case, the preform 10 may be laminated in a state in which the splitting aid is arranged on the surface of each product preform 10. Alternatively, the dividing auxiliary agent supplying step can be performed simultaneously with the laminating step. In this case, when the preformed bodies 10 are stacked in the stacking step, the stacking may be advanced while sequentially arranging the layers of the splitting aids between the preformed bodies 10.

  Any splitting aid may be used as long as it can promote splitting of the processed laminate. For example, various nonmetallic powders can be used as a splitting aid. Since many non-metallic substances do not change in quality at the time of hot working, if a dividing aid is supplied to the raw material laminate 1 before hot working, when dividing after hot working, Sufficient division promoting action can be obtained. Further, if the layer of the splitting auxiliary agent remaining on the surface after the splitting is removed by machining or the like, the splitting auxiliary agent does not substantially affect the manufactured R-T-B type rare earth magnet.

As a specific splitting aid, the same lubricant as that disposed between the metal material to be processed and the mold can be used in press working or extrusion. For example, nitrides such as BN, oxide such as SiO _2, may be mentioned respective powders of carbon materials such as graphite. Of these, it is preferable to use a splitting aid containing SiO ₂ or graphite powder because it exhibits a particularly high splitting promotion effect. Among these, it is particularly preferable to use a splitting aid containing graphite powder because it exhibits a high lubricating action. As such a splitting aid, graphite powder itself or a graphite lubricant obtained by mixing a graphite powder material with organic solder or the like can be used.

  Examples of a method for supplying the splitting aid to the interface of the raw material laminate 1 include a form in which a powdered splitting aid is sprayed and sprayed on the surface of the preform 10 before stacking. Or the form which apply | coats the liquid or paste-form lubricant containing the powder-form dispersion adjuvant with the organic binder, the organic solvent, etc. to the surface of the preforming body 10 can be mentioned.

  In order to reliably hold the splitting aid at the interface of the raw material laminate 1, when the splitting aid is supplied before the stacking step, it is preferably performed as a step immediately before the stacking step. As described above, when the hot press process is performed in the preformed body preparation process, the lamination process may be performed before or after the hot press process. In addition, the splitting aid is supplied to the surface of each preformed body 10. In this case, in order to avoid the influence of the high temperature on the splitting aid, it is better to wait for the high temperature preform 10 after hot pressing to cool before supplying the splitting aid. In particular, when the splitting aid contains an organic solvent or binder, it is preferable to wait for the preform 10 to cool.

  In addition to supplying the splitting aid, as a method that can facilitate the splitting in the splitting step, formation of a notch (notch) can be mentioned. That is, as shown in FIG. 2, in the raw material laminate 1, the notches 1 b may be provided at positions adjacent to the interface 1 a between the plurality of preforms 10. Then, when a force is applied in the dividing step, even if the force is small, the elimination of the sticking tends to proceed at the interface in the processed laminated body starting from the notch. The notch 1b may be formed by providing a protrusion on the base at the stage of hot working.

  As a method for promoting the division in the division step, whether the supply of the division auxiliary or the formation of the notch is used depends on the shape of the preform 10, the form of lamination and hot working, the interface of the processed laminated body What is necessary is just to select suitably according to the grade of sticking in, etc. For example, when compressive stress is applied to the raw material laminate 1 along the stacking direction of the preformed body 10 as in the first embodiment of FIG. 1A, particularly in the thickness direction of the plate-like preformed body 10. When compressive stress is applied, it tends to be in a state where a large fixing force is generated at the interface of a large area through hot working. In such a case, it is preferable to use a splitting aid in that the effect of promoting splitting can be imparted over the entire large area interface. From the viewpoint of forming notches in the thickness direction of the plate-like body and further difficult to perform division using the notch, it is preferable to select the supply of the division aid. On the other hand, when compressive stress is applied to the raw material laminate 1 along the direction intersecting the lamination direction of the preform 10, as in the second and third embodiments of FIGS. By forming the notches, the division can be effectively promoted. You may use together supply of a division | segmentation adjuvant, and formation of a notch.

  Hereinafter, the present invention will be described in detail using examples.

[1] Verification of magnetic properties of R-T-B rare earth magnet (sample according to examples)
A powder of an Nd—Fe—B rare earth magnet material is prepared by using an ultra-quenching method, the Nd—Fe—B rare earth magnet material is cold pressed, and a plate-like cold pressed body (CP Body). And this cold press body was laminated | stacked. At this time, the number of cold pressed bodies was as shown in Table 1. The thickness of each cold press body is 23.7 mm (Examples 1 to 5) or 28.8 mm (Examples 6 to 10) according to the number of layers. did. In the laminate, a layer of graphite-based splitting aid was formed at the interface of each cold pressed body.

  And hot extrusion molding was performed to the obtained cold press body following hot press processing. At the time of hot extrusion molding, a compressive stress was applied along the laminating direction as in the first embodiment shown in FIG. As a die for hot extrusion molding, one whose thickness of the processed laminate after extrusion is 6.6 mm (Examples 1 to 5) or 8.0 mm (Examples 6 to 10). Using. The temperature during hot extrusion was 600 to 850 ° C. Finally, the obtained processed laminate was divided by applying an impact along the lamination direction. Finally, the layer of splitting aid was removed by machining.

(Sample according to comparative example)
Only one cold-pressed body was prepared, and for the one cold-pressed body, a hot-extrusion molding was performed following the hot press process in the same manner as in the above-described example, and a sample according to a comparative example was obtained. . At this time, in Comparative Example 1, a cold press body was formed with a thickness of 23.7 mm equal to the thickness of the laminates of Examples 1 to 5, and hot extrusion was performed so as to have a thickness of 6.6 mm. Molding was performed. In Comparative Example 2, a cold press body was formed with a thickness of 28.8 mm equal to the thickness of the laminates of Examples 6 to 10 above, and hot extrusion was performed to a thickness of 8.0 mm. It was.

(Evaluation of thickness after hot working)
For each sample according to each example, the thickness was measured for each of the individual specimens obtained through division and removal of the division aid. Among them, the maximum value and the minimum value, and the average value for all samples were recorded.

(Evaluation of magnetic properties)
The magnetic properties of the samples according to the examples and the comparative examples were measured using a direct current BH tracer. In the measurement, in particular, the values of residual magnetic flux density and coercive force at room temperature were recorded.

  For the sample according to each example, measurement is performed on each of the sample individuals obtained through the division and removal of the division aid, and among them, the maximum value and the minimum value, and further the average value for all sample individuals. Was recorded. Regarding the sample according to each comparative example, the sample is cut out from the surface which is the upper surface and the lower surface in the compression direction with a predetermined thickness shown in the table, and the center position between the upper surface and the lower surface is the center. Samples were cut out with the same predetermined thickness, and measurements were performed on the cut sample pieces. Here, the thickness at which the sample piece was cut out was aligned with the average value of the sample thickness in each example.

(result)
Table 1 below shows the measurement results of the thickness, residual magnetic flux density, and coercive force of the specimen after hot working for each example. Table 2 shows the measurement results of the residual magnetic flux density and the coercive force with respect to the sample pieces cut out with a predetermined thickness in Comparative Examples 1 and 2.

  In each example, when the maximum value, the minimum value, and the average value of the thickness of the specimen after hot working are compared, the variation between the values is suppressed to be small. That is, by performing hot working in a state where a plurality of preforms (cold press bodies) are laminated, a plurality of R-T-B rare earth magnets having high uniformity in terms of shape can be obtained. It was confirmed that When the number of stacked layers is small, especially when the number of stacked layers is 4 or less, the variation is extremely small.

  In each embodiment, when the maximum value, the minimum value, and the average value of the residual magnetic flux density and the coercive force are compared, the variation between the values is suppressed to be small. In other words, by performing hot working in a state where a plurality of preforms are laminated, not only the uniformity of the shape evaluated based on the thickness variation as described above, but also the magnetic property is highly uniform. It was confirmed that hot working can be carried out with good properties. Note that as the number of layers increases, the thickness obtained by multiplying the average value of the thickness after hot working by the number of layers tends to decrease, but as the number of layers increases, This is because the total thickness increases.

  Moreover, the value of the residual magnetic flux density and the coercive force, particularly the value of the residual magnetic flux density, does not show a large change between Examples 1 to 5 and Examples 6 to 10 having different numbers of layers. It can be seen that the thinness of the compact does not have a significant effect on the magnetic properties obtained. Furthermore, between Examples 1-5 and Comparative Example 1, and between Examples 6-10 and Comparative Example 2, the thicknesses after hot working (thickness of cut out in Comparative Examples) are the same. When the residual magnetic flux density and the coercive force are compared, the maximum value in each example is very close to the value when cut out from the center in the comparative example. On the other hand, the minimum value in each example is close to the value when cut out from the upper and lower surfaces in the comparative example. Further, the difference between the maximum value and the minimum value in the example increases as the number of layers increases, and the difference between the value when cut from the upper surface and the lower surface and the value when cut from the center in the comparative example is cut out. The smaller the thickness, the larger. From these facts, the layer located outside the laminate of the example and the portion near the top and bottom surfaces of the sample of the comparative example are respectively compared to the layer located inside the laminate and the portion near the center of the sample. Thus, it can be seen that the residual magnetic flux density and the coercive force, particularly the coercive force, tend to be small. However, even when taking a manufacturing method in which a plurality of preforms are laminated in a state of being hot-worked and divided, a case where hot-working is performed on a single preform as in the past It was confirmed that magnetic characteristics that are essentially unchanged can be obtained.

[2] Verification of effect of splitting aid (sample according to examples)
Cold pressing was performed on the same material as in the above test [1] to form a cuboid cold pressed body. Two layers of this cold pressed body were laminated along the width direction to form a laminated body. At this time, various splitting aids shown in Table 3 were supplied to the respective interfaces in the laminate at the thicknesses shown in Table 3. The splitting aid is supplied by spraying the powdered splitting aid or by applying the paste-like splitting aid (lubricant) to the surface of the cold pressed body. It was done by forming.

  And the hot press process and hot extrusion molding were performed in order with respect to the obtained laminated body. At the time of hot extrusion molding, as in the second embodiment shown in FIG. 1B, the lamination direction of the laminate is set to be the width direction of the preform, and the molding direction D is set along the lamination direction. The compression direction d was set in the direction crossing the stacking direction. In addition, the hot extrusion molding conditions were the same as those in the test [1].

  And with respect to the hot-worked body in a state where the sticking has occurred at the interface derived from the interface of the cold press body, the lower side of the direction along the interface, that is, the upper surface of FIG. A load was applied in the direction toward the surface. The applied load was gradually increased, and the magnitude of the load at the time when the adhesion at the interface was eliminated was recorded as the coupling force between the magnets.

  At the same time, in order to evaluate the degree of variation in shape and magnetic properties of the form in which compressive stress during hot working is applied in the direction intersecting with the stacking direction, in order to evaluate the degree of variation in shape and magnetic properties, The length (longitudinal dimension), the residual magnetic flux density, and the coercive force were measured for each sample specimen that had undergone the division and removal of the division aid.

(result)
Table 3 below shows the type and thickness of the splitting aid, the length of the cold pressed body (longitudinal dimension), the magnitude of the coupling force between the magnets, the length after hot working, and the residual magnetic flux density. The measurement result of coercive force is shown.

  According to the results in Table 3, in all of Examples 12 to 23 using a splitting aid, the magnet binding force is significantly reduced as compared with Example 11 using no splitting aid. . In other words, the use of the splitting aid facilitates the elimination of the sticking of the interface after hot working, and splitting is facilitated.

Regardless of which splitting aid is used, the greater the thickness, the smaller the magnet binding force, and splitting is particularly easy. In addition, when comparing the types of splitting aids with the same thickness, the use of SiO ₂ powder or graphite-based material reduces the magnet binding force and makes splitting easier than when BN powder is used. Excellent effect.

  Furthermore, when the length after hot working, the residual magnetic flux density, and the variation in coercive force are observed, the values are suppressed to a small value in any of the examples. This is not only when the compressive stress during hot working is applied along the laminating direction as in the test of [1] above, but also when it is applied in the direction crossing the laminating direction. The characteristic shows that high uniformity can be obtained.

  Heretofore, the embodiments and examples of the present invention have been described. The present invention is not particularly limited to these embodiments and examples, and various modifications can be made.

DESCRIPTION OF SYMBOLS 1 Raw material laminated body 1a Interface 1b Notch 10 Preformed body d Compression direction D Molding direction

Claims (11)

A lamination step in which a plurality of preforms made of an R-T-B rare earth magnet material are laminated to form a raw material laminate;
Hot processing is performed on the raw material laminate, and a hot processing step for forming a processed laminate,
Splitting the processed laminate to obtain a plurality of R-T-B rare earth magnets at a position corresponding to the interface between the plurality of preforms constituting the raw material laminate. The manufacturing method of the RTB system rare earth magnet characterized by these.
However, R is at least one rare earth element including Y, and T is obtained by replacing Fe or a part of Fe with Co.   It has a splitting auxiliary agent supply process which supplies the splitting auxiliary agent which promotes division of the processed layered product in the splitting process in the interface between a plurality of preforms which constitute the raw material layered product. Item 2. A method for producing an R-T-B rare earth magnet according to Item 1.   The method for producing an R-T-B rare earth magnet according to claim 2, wherein the splitting aid contains graphite powder.   The R-T-B according to any one of claims 1 to 3, wherein in the raw material laminate, a notch is provided continuously at an interface between the plurality of preforms. Of manufacturing rare earth magnets.   The RT process according to any one of claims 1 to 4, wherein in the hot working step, compressive stress is applied to the raw material laminate along the lamination direction of the preform. A method for producing a B-based rare earth magnet.   6. The RT according to claim 5, wherein the preform is a plate-like body, and the preform is laminated along a thickness direction of the plate-like body in the stacking step. -Manufacturing method of B type rare earth magnet.   The compressive stress is applied to the raw material laminate along the direction intersecting the lamination direction of the preform in the hot working step. Manufacturing method of RTB-based rare earth magnet.   The preform according to any one of claims 1 to 7, wherein the preform is formed through a cold pressing step of obtaining a cold pressed body by cold pressing from powder of an R-T-B rare earth magnet material. 2. A method for producing an R-T-B rare earth magnet according to item 1.   Furthermore, it has a hot press process which performs a hot press, The said hot press process is performed with respect to the said cold press body between the said cold press process and the said lamination | stacking process. The manufacturing method of the R-T-B type rare earth magnet of description.   Furthermore, it has a hot press process for performing a hot press, and the hot press process is performed on a laminate of the cold laminate between the stacking process and the hot working process. The manufacturing method of the RTB system rare earth magnet of Claim 8.   The RTB-based RTB according to any one of claims 1 to 10, wherein the RTB-based rare earth magnet obtained through the dividing step has a thin plate shape with a thickness of 6 mm or less. Of manufacturing rare earth magnets.

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