JP4124461B2 - Manufacturing method of rare earth sintered magnet - Google Patents

Description

  The present invention relates to a method for producing a rare earth sintered magnet containing a rare earth element, and more particularly to a technique for improving the production yield of a rare earth sintered magnet.

  Rare earth sintered magnets, for example, Nd-Fe-B based sintered magnets have advantages such as excellent magnetic properties, Nd as a main component is abundant in resources, and is relatively inexpensive. In recent years, the demand has been increasing. Under these circumstances, research and development for improving the magnetic properties of Nd—Fe—B based sintered magnets and improvement of manufacturing methods for producing high quality rare earth sintered magnets are being promoted in various fields. ing.

  Basically, rare earth sintered magnets are obtained by press-molding an alloy powder obtained by pulverizing a raw material alloy in a magnetic field to form a magnet compact, and sintering the magnet compact in a sintering furnace. However, if sintering is performed with the magnet compact exposed to a sintering furnace, impurity gases such as oxygen and water vapor present inside the sintering furnace may adversely affect the magnet compact. . For this reason, the magnet compact is accommodated in a sealed structure called a sintered case, and the magnet compact is sintered in this state.

  By the way, in order to improve the production efficiency of the sintering process, a magnet molded body is laminated and sintered in a sintering case. In this case, it is important to prevent welding of the magnet molded bodies in the vertical direction due to high heat applied during sintering. For example, in Patent Document 1, a sintered plate on which a magnet molded body is placed is opened from the opening. A configuration has been proposed in which a slidable plate is horizontally slidable and a sintered plate is installed in multiple stages in a sintered case.

  However, such a sintered case is very expensive because it has a large and complicated structure. In addition, since the sintered case with a complicated structure is subjected to a high-temperature heat treatment exceeding, for example, 1000 ° C. during the sintering process of the magnet compact, it is easily deformed by heat, has a short life, and is expensive to replace. There is an inconvenience of becoming.

  For this reason, it is also possible to simply stack a plurality of magnets mounted on a plate made of metal or the like and place them in a sintering case having a simple structure such as a box shape and sinter them. Although it is conceivable, since the sintering case is heated at the time of sintering, there is a problem that the magnet molded body and the sintering case or a metal plate are welded at a contact point. When a magnet molded body and a sintering case or a metal plate are welded, it takes a lot of labor and time to peel off the sintered case etc. from the welded magnet molded body. There are problems such as causing an appearance defect such as chipping or cracking in the magnet molded body to apply a large force, and causing deterioration of characteristics due to deformation or insufficient sintering because uniform sintering is not possible.

  In view of this, it has been practiced to employ a material (Mo, stainless steel, etc.) in which the magnet compact is difficult to weld to the sintering case (see, for example, Patent Document 1 and Patent Document 2). If only Mo or stainless steel is used for the case or the sintering jig, it is not possible to completely prevent the magnet molded body from being welded to the sintering case or the sintering jig.

  In addition, in order to prevent welding between the magnet compact and the sintering case or sintering jig, a powder having low reactivity with the magnet compact, such as alumina powder, is spread on the plate on which the magnet compact is arranged. There are also techniques (see, for example, Patent Document 2). In this case, however, (1) it is necessary to coat the powder uniformly to some extent, so that it takes a long time to work, and (2) the magnet molded body and the bottom of the case after the sintering is finished. Because the powder is closely attached to the magnet, the load of the process of removing these cleanly is large. (3) In particular, a large force is applied when removing the powder adhering to the magnet compact after sintering. There are drawbacks such as frequent appearance defects such as cracks and scratches, resulting in a decrease in yield.

On the other hand, using a Mo or Mo-based alloy net has been proposed as a sintering jig for preventing welding between the sintered case and the magnet compact (see, for example, Patent Document 3). By interposing this Mo metal mesh between the base plate laid on the bottom of the sintered case and the magnet molded body, it is said that adhesion between the magnet molded body and the base plate can be prevented during sintering.
JP 2000-315611 A Japanese Patent Laid-Open No. 2002-20803 JP-A-6-7875

  However, in Patent Document 3, although it is described that a Mo or Mo-based alloy net is sandwiched between a base plate for arranging the compacts and the compact, the magnet compacts are laminated and sintered. Is not assumed. Since the surface of the Mo or Mo-based alloy net described in Patent Document 3 is substantially flat by rolling, a large load is applied to the magnet compact when the magnet compact is laminated, and the net and the magnet compact are separated. Since it becomes easy to weld, it is thought that it causes the fall of a yield.

  Moreover, although the above-mentioned sintering case is a closed type, inflow of impurity gas existing in the sintering furnace into the inside of the sintering case is unavoidable, and as a result, it is the same as the case where the sintering case is not used. In addition, the impurity gas in the sintering furnace has various adverse effects, and there is a problem that the yield of the rare earth sintered magnet is lowered. Therefore, the present applicant has devised a technique for sintering a magnet compact in a state of being wrapped with a metal foil when manufacturing a rare earth sintered magnet. According to this technique, the metal foil absorbs the impurity gas in the sintering furnace, and contamination of the magnet compact can be prevented. However, in this technique, the magnet molded body and the metal foil are welded at a contact portion, which causes deterioration of characteristics and may cause a poor appearance when the metal foil is peeled off from the magnet molded body. There is.

  Therefore, the present invention has been proposed in view of such a conventional situation, and it is possible to suppress the welding of the parts used during sintering to the magnet compact and to improve the yield. It aims at providing the manufacturing method of a magnet.

  As a result of repeated studies to solve the above-mentioned problems, the inventors of the present invention have adopted a mesh as a means for avoiding welding between magnet molded bodies and welding between a magnet molded body and parts used during sintering. We have found that the use of a plate-like plate is extremely effective.

The present invention has been completed on the basis of such knowledge, and is a method for producing a rare earth sintered magnet for sintering a magnet molded body containing a rare earth element. And a mesh structure is placed on the top and bottom to form a laminated structure, and the entire periphery of the laminated structure is wrapped with metal foil, and the laminated structure wrapped with metal foil is further contained in a container. The sintering is performed.

  According to the manufacturing method of the rare earth sintered magnet as described above, the magnet compact including the rare earth element is sintered in a state of being laminated through the mesh-like plate, thereby welding the magnet compact between the upper and lower sides. Can be prevented. Further, since the mesh-like plate has a small contact area with the magnet molded body and is difficult to weld, even when the magnet molded body is laminated and sintered, the welding to the magnet molded body is suppressed. . For this reason, there is no deformation or lack of sintering due to welding, and there is no need to peel off the parts welded to the magnet molded body, so there is no appearance defect and an improvement in yield is realized. .

Furthermore, since the metal foil adsorbs the impurity gas present in the sintering furnace, for example, by wrapping the magnet molded body with the metal foil, the contamination of the magnet molded body with the impurity gas is suppressed. As a result, inconveniences such as deformation of the magnet molded body due to the impurity gas and deterioration of characteristics are suppressed, and the yield is improved. In addition, by interposing a mesh-like plate between the metal foil and the magnet molded body, the contact between the metal foil and the magnet molded body becomes point contact, and the contact area is minimized, so these are welded. Is prevented. For this reason, there is no deformation or lack of sintering due to welding, and an operation of peeling off the parts and the like welded to the magnet molded body is not required, so that the appearance defects are generated and the yield is improved.

  In the present specification, the pre-sintered magnet molded body before the sintering process, the sintered magnet molded body during the sintering process, and the sintered body after the sintering process are collectively referred to as a magnet molded body. I will do it. Further, the term “sintering” in the specification of the present application refers to heat treatment of a magnet molded body in order to produce a rare earth sintered magnet, and is a term including firing accompanied by a chemical reaction.

  According to the present invention, by laminating the magnet molded body through the mesh-shaped plate, it is possible to prevent both the welding of the magnet molded body and the mesh-shaped plate and the welding of the magnet molded bodies, and the yield. Improvements can be made. Further, by laminating and sintering the magnet compacts, a large amount of magnet compacts can be sintered at a time, so that the productivity can be greatly improved.

  Further, according to the present invention, the metal foil that wraps the magnet molded body suppresses contamination of the magnet molded body by the impurity gas, and the metal foil is provided by interposing a mesh plate between the magnet molded body and the metal foil. Therefore, the yield can be improved.

Hereinafter, a method for producing a rare earth sintered magnet according to the present invention will be described with reference to the drawings.
The method for producing a rare earth sintered magnet according to the present invention prevents welding of a magnet molded body to various sintering parts such as a sintering case, a flat plate for sintering, a metal foil, and welding between magnet molded bodies. Therefore, the main feature is to use a mesh-like plate-like thin plate. In the following, a rare earth sintered magnet manufactured by the method of manufacturing a rare earth sintered magnet according to the present invention will be described first, then an outline of the method of manufacturing the rare earth sintered magnet will be described, and then a magnet compact is laminated. Next, a method for interposing a mesh plate between upper and lower magnet compacts during sintering will be described, and then, between the magnet compact and the metal foil for preventing contamination of the magnet compact by impurity gas. A method of interposing a mesh-like plate in the case will be described.

  The rare earth sintered magnet to be manufactured by the method for manufacturing a rare earth sintered magnet of the present invention is mainly composed of a rare earth element. As the magnet composition, for example, R-T-B (R is one or more of rare earth elements, where the rare earth element is a concept including Y. T is a transition metal element in which Fe or Fe and Co are essential. In the case of using a rare earth sintered magnet having excellent magnetic properties, in the magnet composition after sintering, the rare earth It is preferable that the composition be such that the element R is 20 to 40% by weight, the boron B is 0.5 to 4.5% by weight, and the balance is the transition metal element T. Here, R is one or more selected from rare earth elements, that is, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu. Especially, since Nd is abundant in resources and relatively inexpensive, the main component is preferably Nd. Further, the inclusion of Dy is effective in improving the coercive force Hcj because it increases the anisotropic magnetic field.

  Alternatively, the additive element M can be added to form an R-T-B-M rare earth sintered magnet. In this case, examples of the additive element M include Al, Cr, Mn, Mg, Si, Cu, C, Nb, Sn, W, V, Zr, Ti, Mo, Bi, and Ga. A seed | species or 2 or more types can be selected and added. The addition amount of these additional elements M is preferably 3% by weight or less in consideration of magnetic characteristics such as residual magnetic flux density. If the amount of additive element M added is too large, the magnetic properties may be deteriorated.

  In addition, SmCo-based rare earth sintered magnets, SmFeN-based magnet powders, and the like can be manufactured by the method for manufacturing a rare earth sintered magnet of the present invention. Of course, it is needless to say that the present invention is not limited to these compositions, and can be applied to all known compositions as rare earth sintered magnets.

  Next, the manufacturing method of the rare earth sintered magnet of this invention is demonstrated. For producing a rare earth sintered magnet, for example, a powder metallurgy method is employed. Hereinafter, a method for producing a rare earth sintered magnet by powder metallurgy will be described.

  FIG. 1 shows an example of a process for producing a rare earth sintered magnet by powder metallurgy. This manufacturing process basically includes an alloying step 1, a coarse pulverizing step 2, a fine pulverizing step 3, a magnetic field forming step 4, a sintering / aging step 5, a processing step 6, and a surface treatment step 7. Is done. In order to prevent oxidation, most of the steps after sintering are performed in a vacuum or in an inert gas atmosphere (in a nitrogen atmosphere, an Ar atmosphere, etc.).

  In the alloying step 1, a metal or alloy as a raw material is blended according to the magnet composition, melted in a vacuum or an inert gas, for example, Ar atmosphere, and cast into an alloy. As a casting method, a strip casting method (continuous casting method) in which molten high-temperature liquid metal is supplied onto a rotating roll and an alloy thin plate is continuously cast is preferable from the viewpoint of productivity and the like. It is not limited to that. As the raw material metal (alloy), pure rare earth elements, rare earth alloys, pure iron, ferroboron, and alloys thereof can be used. A solution treatment may be performed as necessary for the purpose of eliminating solidification segregation. As a condition for the solution treatment, for example, it is held in a 700 to 1500 ° C. region for 1 hour or more under vacuum or Ar atmosphere.

  As the alloy, a single alloy having a final magnet composition may be used, or a plurality of types of alloys having different compositions may be mixed so as to have a final magnet composition. Mixing may be performed in any process of alloy, raw material coarse powder, and raw material fine powder.

  In the coarse pulverization step 2, the previously cast raw alloy thin plate, ingot or the like is pulverized until the particle size is about several hundreds of micrometers. As the pulverizing means, a stamp mill, a jaw crusher, a brown mill, or the like can be used. In order to improve the coarse pulverization property, it is effective to perform coarse pulverization after occlusion of hydrogen.

  The coarse pulverization step 2 can be constituted by a plurality of steps in which a plurality of pulverization means are combined. For example, the coarse pulverization step 2 can be two steps of a hydrogen pulverization step and a mechanical coarse pulverization step. The hydrogen pulverization step is a step in which hydrogen is occluded in the cast raw material alloy and pulverized in a self-destructive manner utilizing the fact that the hydrogen occlusion amount varies depending on the phase. Thereby, it can grind | pulverize to the magnitude | size about particle size several mm. The mechanical coarse pulverization step is a step of pulverizing using a mechanical method such as a brown mill as described above. The raw alloy powder pulverized to a size of about several millimeters by the hydrogen pulverization step is used. Then, pulverize until the particle size is about several tens of μm. When performing the hydrogen pulverization step, the mechanical coarse pulverization step may be omitted.

  After the coarse pulverization step 2 is completed, a pulverization aid is usually added to the coarsely pulverized raw material alloy powder. As the grinding aid, for example, a fatty acid compound or the like can be used. In particular, by using a fatty acid amide as the grinding aid, a rare earth sintered magnet having good magnetic properties can be obtained. The addition amount of the grinding aid is preferably 0.03 to 0.4% by weight. When the grinding aid is added within this range, the amount of residual carbon after sintering can be reduced, which is effective in improving the magnetic properties of the rare earth sintered magnet.

  After the coarse pulverization step 2, a fine pulverization step 3 is performed. The fine pulverization step 3 is performed using, for example, a jet mill. The conditions for fine pulverization may be appropriately set according to the airflow pulverizer to be used, and the raw material alloy powder is finely pulverized until the average particle size becomes about 1 to 10 μm, for example, 3 to 6 μm. A jet mill opens a high-pressure inert gas (for example, nitrogen gas) from a narrow nozzle to generate a high-speed gas flow, accelerates powder particles by this high-speed gas flow, and collides powder particles with each other. Or, it is a method of crushing by generating a collision with a target or a container wall. Jet mills are generally classified into jet mills that use fluidized beds, jet mills that use vortex flow, jet mills that use impingement plates, and the like.

  After the pulverizing step 3, in the forming step 4 in the magnetic field, the raw material alloy fine powder is formed in the magnetic field. Specifically, the raw material alloy fine powder obtained in the fine pulverization step 3 is filled in a mold in which an electromagnet is arranged, and is molded in a magnetic field with a crystal axis oriented by applying a magnetic field. Forming in the magnetic field may be either longitudinal magnetic field shaping or transverse magnetic field shaping. The forming in the magnetic field may be performed at a pressure of about 130 to 160 MPa in a magnetic field of 800 to 1500 kA / m, for example.

  Next, in the sintering / aging step 5, sintering and aging treatment are performed. That is, after forming the raw material alloy fine powder in a magnetic field, the magnet compact is sintered in a vacuum or in an inert gas atmosphere (in a nitrogen atmosphere, an Ar atmosphere, or the like). The sintering temperature needs to be adjusted according to various conditions such as composition, pulverization method, difference in particle size and particle size distribution, etc. For example, sintering may be performed at 1000 to 1150 ° C. for about 5 hours, and rapid cooling after sintering. Is preferred. After sintering, the obtained sintered body is preferably subjected to aging treatment. This aging treatment is an important step in controlling the coercive force Hcj of the obtained rare earth sintered magnet. For example, the aging treatment is performed in an inert gas atmosphere or in a vacuum. As the aging treatment, a two-stage aging treatment is preferable, and in the first aging treatment step, the temperature is maintained at a temperature of about 800 ° C. for 1 to 3 hours. Next, a first quenching step is provided for quenching to room temperature to 200 ° C. In the second stage aging treatment step, the temperature is maintained at about 550 ° C. for 1 to 3 hours. Next, a second quenching step for quenching to room temperature is provided. Since the coercive force Hcj is greatly increased by heat treatment at around 600 ° C., when aging treatment is performed in a single stage, it is advisable to perform aging treatment at around 600 ° C.

  After the sintering / aging step 5, a processing step 6 and a surface treatment step 7 are performed. The processing step 6 is a step of mechanically forming into a desired shape. The surface treatment process 7 is a process performed to suppress oxidation of the obtained rare earth sintered magnet. For example, a plating film or a resin film is formed on the surface of the rare earth sintered magnet.

  In the present invention, in the sintering and aging process 5 of the above manufacturing process, in order to prevent the magnet molded body from being welded to the sintering case or the sintered part, or between the magnet molded bodies, The main feature is in using the mesh 10 as shown in FIG. Hereinafter, an example of sintering using the mesh 10 will be described in detail with reference to FIG.

  In the sintering and aging process, as shown in FIG. 3, the magnet molded body 11 includes a main body 14 having a bottom surface 12 and a side wall 13 and an opening, and a lid 15 made of, for example, Mo that closes the opening. Housed in the enclosed space. A mesh 10 is laid on the bottom surface 12 of the main body, and a plurality of magnet molded bodies 11 are placed on the mesh 10 with a predetermined interval. By disposing the mesh 10 on the bottom surface 12, it is possible to prevent contact between the first-stage magnet molded body 11 and the main body bottom surface 12 and to prevent welding. The mesh 10 is placed on the first-stage magnet molded body 11, and a plurality of magnet molded bodies 11 are further placed on the mesh 10 with a predetermined interval. By repeating this, the four-stage magnet molded body 11 is laminated via the mesh 10.

  Although it does not specifically limit as the mesh 10 used here, The thing etc. which knit the wire which consists of metals and made it thin plate shape etc. can be used. Generally, as a metal mesh-like plate, the surface is substantially wavy by knitting a metal wire, and the surface is substantially wavy without rolling by applying a rolling process after knitting the metal wire. However, in the present invention, it is preferable to use a mesh-like plate having a substantially wavy surface by knitting a metal wire. Because the mesh 10 and the magnet molded body 11 disposed above and below the mesh 10 are in point contact, the mesh 10 and the magnet molded body 11 are difficult to weld, and even when they are welded, they can be easily peeled off. Because. The mesh plate whose surface is made substantially flat by rolling or the like has a large contact area with the magnet molded body 11, and therefore suppresses the welding between the mesh plate and the magnet molded body 11. In particular, when the magnet molded body 11 is laminated and sintered, there is a problem that the magnet molded body 11 and the mesh plate are significantly welded.

  Although it does not specifically limit as a material which comprises the mesh 10, For example, Mo, the alloy containing Mo, etc. can be used. An appropriate value of the spacing between the wire rods of the mesh 10 (hereinafter simply referred to as mesh spacing) varies depending on the shape and size of the magnet molded body 11 to be placed, but is preferably 0.05 mm or more. When the mesh interval is less than 0.05 mm, stability is not secured when the small magnet molded body 11 is placed, and when the large magnet molded body 11 is placed, the contact portion between the wire rod and the magnet molded body 11 is not secured. A load is applied, and deformation or discoloration may occur. However, considering the welding between the mesh 10 and the magnet molded body 11, the mesh interval is preferably 5 mm or less. The mesh interval is more preferably 0.5 mm to 2.5 mm. In addition, the mesh space | interval here is the distance from the width direction edge part b of a certain one wire 10a to the edge part d by the side of the wire 10a of the adjacent wire 10c including the said wire 10a, as shown in FIG. Represents.

  The main body 14 is not limited to a box shape and may have any shape as long as the magnet molded body 11 can be placed thereon. As the material of the main body 14, any material used for a case for sintering a general rare earth sintered magnet can be used. For example, a high melting point metal such as Mo, Ti, W, Ir, or a ceramic such as alumina. And carbon. The magnet molded body 11 may have any shape such as a cylindrical shape or a rod shape, or may be a powder shape.

  As shown in FIG. 3, in the sintering process, by interposing the mesh 10 between the laminated magnet molded bodies 11, welding of the magnet molded bodies 11 can be prevented. In addition, conventionally, alumina powder and iron powder have been interposed between magnet molded bodies in order to prevent adhesion between laminated magnet molded bodies. Although the operation | work which removes powder was required, since it is only necessary to arrange | position the mesh 10 between the magnet moldings 11 in this invention, the working time can be shortened significantly. As described above, since the mesh 10 can be used to prevent the magnet molded bodies 11 from being welded to each other, the work of peeling the welded magnet molded bodies 11 is not necessary, and the magnet molded body 11 caused by the peeling work is broken. As a result, cracks and the like are not generated, and the yield can be improved. In addition, the work time can be shortened. Furthermore, by laminating and sintering the magnet compacts 11, it is possible to sinter a large number of magnet compacts 11 at a time, contributing to productivity improvement.

  Although it is conceivable to use a metal plate to prevent the laminated magnet molded bodies 11 from being welded to each other, the mesh 10 is lighter than the metal plate, and therefore has the advantage of less load application.

  As described above, an example of the sintering process to which the present invention is applied has been described. In the present invention, for example, as shown in FIG. 5, the metal foil 16 is used for the purpose of preventing contamination of the magnet molded body 11 with impurity gas, A method using the mesh 10 may be employed for the purpose of preventing the metal foil 16 and the magnet molded body 11 from being welded. In the description of FIG. 5, the same members as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted here.

  As shown in FIG. 3, the magnet molded body 11 is wrapped with a metal foil 16, and has a main body 14 having an opening and a bottom surface 12 and a side wall 13, and a lid 15 made of, for example, Mo that closes the opening. It is accommodated in the space surrounded by. That is, the metal foil 16 is laid on the bottom surface 12 of the main body, the mesh 10 is placed on the metal foil 16, and the plurality of magnet molded bodies 11 are placed on the mesh 10 with a predetermined interval. The same mesh 10 as the mesh 10 disposed under the magnet molded body 11 is placed on the magnet molded body 11, and these are wrapped with a metal foil 16.

  As the metal foil 16, any metal having a melting point higher than the maximum sintering temperature at the time of sintering can be used without particular limitation, and examples thereof include Nb foil, Ti foil, platinum foil, and stainless steel foil. The type of the metal foil 16 may be appropriately selected according to the purpose, and it is preferable to use a stainless steel foil in consideration of the price and availability. Also, when oxygen and the like are released during sintering, Since there exists a possibility of contaminating the other magnet molded object 11, it is preferable to use Nb foil when oxygen adsorption property is considered.

  Although there is no restriction | limiting in particular as thickness of the metal foil 16, It is preferable to set it as the range of 0.001 mm-0.2 mm, and by setting it as this range, it was excellent in breakage resistance and sufficient adsorption capacity of impurity gas. It is possible to achieve both realization and excellent flexibility and handling, and price control. Moreover, the more preferable range of the metal foil 16 is 0.003 mm to 0.1 mm, and the more preferable range is 0.005 mm to 0.05 mm.

  The metal foil 16 may be a single metal foil, but the metal foil may be used in a double, triple, or more layer for the purpose of improving hermeticity and reducing the risk of breakage during use. . The metals to be stacked may be different or the same. For example, by forming the metal foil 16 into a double structure in which an Nb foil having excellent oxygen adsorptivity is arranged on the inside and a stainless steel foil having excellent damage resistance is arranged on the outside, the oxidation of the magnet compact 11 during sintering can be prevented. It is possible to achieve both the maintenance of the airtightness of the structure for sintering.

  Impurity gases such as oxygen and water vapor are present in the sintering furnace in which the sintering structure 1 is accommodated during the sintering, but as shown in FIG. By sealing, the metal foil 16 adsorbs the impurity gas and suppresses contamination of the magnet molded body 11 accommodated in the metal foil 16. For this reason, it is possible to suppress inconveniences such as deformation of the magnet molded body 11 due to the impurity gas and deterioration of characteristics, and to improve the yield. In addition, since the metal foil 16 can be easily replaced, the replacement of the metal foil 16 with a new one can further suppress contamination of the magnet molded body 11 and further increase the yield.

  Further, although it is necessary to replace the metal foil 16 with a new one according to the degree of contamination or breakage, the metal foil 16 is much cheaper than the conventional rigid sintered case. The manufacturing cost can be reduced even in consideration of easy breakage and high replacement frequency. Further, when the metal foil 16 is damaged or contaminated, it can be easily replaced with a new metal foil 16, and the cost for the replacement is small.

  Furthermore, in the sintering process, the mesh 10 is interposed between the metal foil 16 and the magnet molded body 11, thereby preventing the magnet molded body 11 and the metal foil 16 from contacting each other and welding them. Can be prevented. For this reason, the operation | work which peels off the metal foil 16 welded to the magnet molded object 11 is unnecessary, and while work time can be shortened, the crack of the magnet molded object 11 resulting from a peeling operation, a crack, etc. do not generate | occur | produce. Yield improvement can be realized.

  Hereinafter, specific examples to which the present invention is applied will be described based on experimental results. In addition, it cannot be overemphasized that this invention is not limited to description of a following example.

<Example 1>
In Example 1, a cylindrical NdFeB magnet was manufactured. First, an NdFeB-based cylindrical magnet compact having a diameter of 10 mm and a thickness of 10 mm having a composition of Nd 30 wt%, Dy 3 wt%, Fe 65 wt%, B 1 wt%, and Co 1 wt% was formed by powder metallurgy.

  In the sintering / aging process, a structure for sintering having the structure shown in FIG. 6 was used. 6, the inner wall of the main body 14 having the bottom surface 12 and the side wall 13 is covered with a metal foil 16, and the opening of the main body 14 is closed with a lid 15 made of, for example, Mo. In FIG. 6, a metal foil 16 wraps four layers of a plurality of magnet molded bodies 11 arranged on the mesh 10 and further overlaps the mesh 10.

  The main body of the structure for sintering is made of Mo having a thickness of 2.0 mm. Moreover, the metal foil used the stainless steel foil of thickness 0.01mm, and covered the bottom face and side surface inside a main body.

  Next, a # 24 mesh made of Mo (mesh spacing 1 mm) and a wire diameter of 0.35 mm is placed on the bottom metal foil of the sintering structure so that the magnet compact is not overlapped on the mesh. Arranged side by side. The same mesh as that laid on the bottom surface was placed on the placed magnet molded body, and the magnet molded bodies were further arranged side by side. Similarly, four stages of magnet moldings placed on the mesh were installed, and the mesh was placed on the uppermost magnet molding. Next, the uppermost mesh was covered with a stainless steel foil, the magnet molded body and the entire mesh were covered with the stainless steel foil, and the remaining end was folded into the upper part of the mesh, thereby enclosing the magnet molded body and the mesh.

  In this state, sintering was performed in a sintering furnace, and an aging treatment was performed to obtain the rare earth magnet of Example 1. Sintering was performed at a sintering temperature of 1100 ° C., sintering in vacuum for 2 hours, and then sintering at a sintering temperature of 800 ° C. for 1 hour. Thereafter, an aging treatment was performed at 550 ° C. for 2.5 hours.

<Comparative Example 1>
Instead of the mesh, the same procedure as in Example 1 was performed except that the iron powder was uniformly dispersed on the bottom metal foil of the structure for sintering and the iron powder was uniformly dispersed on the magnet molded body. A rare earth sintered magnet of Comparative Example 1 was produced.

  Comparing Example 1 and Comparative Example 1 above, in Comparative Example 1 after completion of the sintering / aging treatment, the magnet compact and the iron powder are welded, and the iron powder is peeled off from the magnet compact. On the other hand, in Example 1, no fusion between the magnet compact and the mesh as the sintering jig was observed. Further, no welding between the magnet compacts was observed. As a result, an operation of peeling a sintering jig such as a mesh from the magnet compact becomes unnecessary.

  Regarding the rare earth sintered magnets of Example 1 and Comparative Example 1 described above, those in which no chipping or cracking was observed were evaluated as non-defective products, and those in which chipping or cracking occurred were evaluated as defective products. As a result, the defective rate of Comparative Example 1 was 7%, whereas the defective rate of Example 1 was 2%, which was found to be greatly improved.

  Moreover, the product yield of Example 1 and Comparative Example 1 was also evaluated. As a result, the product yield increased to 93% in Example 1 compared to 93% in Comparative Example 1. Furthermore, in Example 1, it was possible to completely prevent the metal foil from adhering to the magnet molded body. Although the metal foil attached to the mesh was somewhat observed, the metal foil attached to the mesh could be easily peeled off, and the working efficiency was improved as compared with Comparative Example 1.

<Example 2>
In this example, a rod-shaped SmCo magnet was manufactured as follows.
First, by a powder metallurgy method, a SmCo-based bar magnet compact 11 having a composition of Sm 25% by weight, Fe 15% by weight, Cu 5% by weight, Zr 2% by weight and the balance Co and having a length of 40 mm, a width of 15 mm, and a height of 20 mm is formed. did.

  In the sintering / aging process, a structure for sintering having the structure shown in FIG. 5 was used. As the main body of the structure for sintering, a Mo case having a thickness of 2.0 mm was used. Further, as the metal foil, a stainless steel foil and a Nb foil having a thickness of 0.01 mm were superposed with the Nb foil on the inside and the stainless steel foil on the outside.

  With this metal foil, the bottom surface and the inner side surface of the Mo case were covered. Next, a # 24 mesh made of Mo (mesh spacing 1 mm) and a wire diameter of 0.35 mm is placed on the bottom metal foil of the sintering structure so that the magnet compact is not overlapped on the mesh. Arranged side by side. A mesh similar to that laid on the bottom surface was placed on the placed magnet molded body, and a double metal foil (stainless steel foil and Nb foil) was folded on the upper mesh. Further, another double metal foil was covered to completely enclose the magnet molded body and the mesh. An Mo plate was placed on the metal foil enclosing the magnet compact and the mesh.

  In this state, sintering was performed in a sintering furnace, and an aging treatment was performed to obtain a rare earth magnet of Example 2. Sintering was performed at a sintering temperature of 1200 ° C., sintering in vacuum for 2 hours, and then sintering at a sintering temperature of 1150 ° C. for 1 hour. Thereafter, an aging treatment was performed to obtain a rare earth sintered magnet of Example 2.

<Comparative example 2>
Instead of the mesh, the same procedure as in Example 2 was performed except that the iron powder was uniformly dispersed on the bottom metal foil of the structure for sintering and the iron powder was uniformly dispersed on the magnet molded body. A rare earth sintered magnet of Comparative Example 2 was produced.

  Comparing Example 2 and Comparative Example 2 above, in Comparative Example 2 after completion of the sintering and aging treatment, the magnet compact and the iron powder are welded, and the iron powder is peeled off from the magnet compact. However, in Example 2, welding between the magnet compact and the mesh as the sintering jig was not recognized at all, and as a result, the magnet compact was sintered from the mesh. The work of peeling the linking jig is no longer necessary.

  Moreover, about the rare earth sintered magnets of Example 2 and Comparative Example 2, those in which no chipping or cracking was observed were evaluated as good, and those in which chipping or cracking occurred were evaluated as defective. As a result, the defective rate of Comparative Example 2 was 7%, whereas the defective rate of Example 2 was 2%, which was found to be greatly improved.

  Furthermore, the product yield of Example 2 and Comparative Example 2 was also evaluated. As a result, the product yield was 93% in Comparative Example 2, but increased to 98% in Example 2. Furthermore, in Example 2, it was possible to completely prevent the metal foil from adhering to the magnet molded body. Although some metal foil was attached to the mesh, the metal foil attached to the mesh could be easily peeled off, and the working efficiency was improved as compared with Comparative Example 2.

It is a flowchart which shows an example of the manufacturing process of a rare earth sintered magnet. It is a top view of the mesh used for the manufacturing method of the rare earth sintered magnet of this invention. It is sectional drawing explaining an example of a sintering and an aging process. It is a top view for demonstrating the space | interval of the wire rod of a mesh. It is sectional drawing explaining the other example of a sintering and an aging process. It is sectional drawing for demonstrating the sintering and aging process of Example 1.

Explanation of symbols

10 mesh, 11 magnet molded body, 12 bottom surface, 13 side wall, 14 body, 15 lid, 16 metal foil

Claims (13)

A method for producing a rare earth sintered magnet for sintering a magnet molded body containing a rare earth element, wherein the magnet molded body is laminated via a mesh plate, and a mesh structure plate is arranged above and below the laminated structure. In addition, a method for producing a rare earth sintered magnet, comprising: surrounding the entire laminated structure with a metal foil, further housing the laminated structure wrapped with the metal foil in a container, and performing the sintering. The magnet molded body is laminated in multiple stages via a mesh-like plate and a mesh-like plate is arranged on the upper and lower sides to form a laminated structure, and the periphery of the entire laminate is wrapped with metal foil, and further laminated with metal foil The method for producing a rare earth sintered magnet according to claim 1, wherein the structure is contained in a sealed container and the sintering is performed.   2. The method for producing a rare earth sintered magnet according to claim 1, wherein the mesh-shaped plate is made of a wire woven in a net-like shape, and has a substantially wavy surface.   The method of manufacturing a rare earth sintered magnet according to claim 1, wherein the mesh plate is made of Mo or an alloy containing Mo.   The method for producing a rare earth sintered magnet according to claim 1, wherein an interval between the wires of the mesh-shaped plate is 0.05 mm to 5 mm.   6. The method for producing a rare earth sintered magnet according to claim 5, wherein an interval between the wires of the mesh plate is 0.5 mm to 2.5 mm.   The method for producing a rare earth sintered magnet according to claim 1, wherein the metal foil has a thickness of 0.001 mm to 0.2 mm.   The method for producing a rare earth sintered magnet according to claim 7, wherein the metal foil has a thickness of 0.003 mm to 0.1 mm.   The method for producing a rare earth sintered magnet according to claim 8, wherein the metal foil has a thickness of 0.005 mm to 0.05 mm.   The method for producing a rare earth sintered magnet according to claim 1, wherein the melting point of the metal foil is higher than a maximum sintering temperature.   The method for producing a rare earth sintered magnet according to claim 1, wherein the metal foil is one or more selected from Nb foil, Ti foil, platinum foil, and stainless steel foil.   The method for producing a rare earth sintered magnet according to claim 11, wherein the metal foil is an Nb foil and / or a stainless steel foil.   The method for producing a rare earth sintered magnet according to claim 12, wherein the metal foil has a double structure in which an Nb foil and a stainless steel foil are laminated in this order from the inside.

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