JP2008045148A - Method for producing magnet and production apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems of a conventional method that an expensive large-scale magnetic-field molding machine is necessary, a die life is short, a large amount of expensive Dy is used which is small in absolute magnitude on the earth, and treatment for preventing a surface from being oxidized and from forming rust is necessary. <P>SOLUTION: This production method includes steps for: charging a molded workpiece in a molding die of a magnetic-field molding machine which utilizes a magnetic attractive force; and temporarily baking the workpiece. Then, the method does not need to consider mechanical strength, does not need to charge adhesives, accordingly can align directions of easy axes of magnetization, and can produce a high-performance magnet at a low cost. In addition, the molding die is not used at a high temperature in a sintering process, and has the long life and an economical advantage, because the workpiece is temporarily baked at a low temperature and the temporarily baked workpiece is immediately taken out of the die so as not to be exposed to the high temperature. Furthermore, the method includes steps for using Al, Ni, Co, an alloy or the like together with the expensive Dy, and simultaneously alloying them with the temporarily-baked workpiece in a full-sintering step to improve magnetic performance and conduct rust prevention treatment. Accordingly, the method can omit a vapor deposition process or a plating process thus increasing an economical effect. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnet manufacturing method and apparatus.

Conventionally, there has been a drawback of requiring a large and expensive magnetic field press, but as a measure to improve it, a method of not performing molding has been invented. However, this method is a filling process in which the raw material has a predetermined density, without applying a magnetic field, and in order to give a magnetic field in the subsequent process, the powder particles are difficult to move freely when aligned in the easy magnetization axis direction. In addition, since powder press molding is not performed, the product cannot be taken out and must be sintered together with the container, so that there is a disadvantage that the case is consumed frequently.
Patent Application Notice Sho 47-21197 Patent Application Notice Sho 55-26601 Patent application publication number JP2006-19521 Patent Application Publication Number Japan Society of Applied Magnetics 147th Research Report Latest Trends and Applications of Rare Earth Magnets

  It was extremely uneconomical because it used an expensive large 100-ton magnetic field press. Because the molding material was filled with powder raw material and the particles could move freely, there was no process of molding while applying a magnetic field, so the easy axis of magnetization could not be adjusted sufficiently It was not possible to obtain sufficient magnetic properties. In order to take out the molded product from the molding die, an operation such as demagnetizing the magnetization of the magnetized molded product is necessary, and there is a problem in terms of economy and magnet characteristics. In addition, there is a method in which one of the excellent inventions of the prior art is sintered in a raw material filled container, but this method makes it difficult for the filled container to sufficiently withstand the sintering temperature of the molded product. Was uneconomical. Finally, metal magnets have many defects due to the occurrence of rust on the surface, and have defects that require oxidation treatment such as metallization or plating. Many of these defects were present as problems.

First, it was common sense to use a large 100-ton class magnetic field molding machine. However, in the present invention, the applied pressure is limited to a level that allows sufficient molding with a magnetic field attractive force, and the molded product is taken out from the molding die. Without any problem, temporary firing is performed while the molded product remains in the molding die. In order to perform the main sintering after removing the molded product from the mold after pre-baking at a temperature much lower than that of the main sintering by this work and performing a predetermined surface treatment again, The mold is highly durable and economical only by being exposed to a temperature much lower than the main sintering temperature. Further, as shown in FIG. 1, the fine powder as the raw material of the magnet is provided with a lower plate 20 made of ferromagnetic material at the bottom of the outer frame 1 made of ferromagnetic material, filled with powder 3 therein, and separator 4 The powder raw material 3 is inserted again, and an appropriate number of sheets is selected depending on the shape of the repetitively molded product. In the drawing, for convenience, four sheets are simultaneously molded in a magnetic field.

  FIG. 2 shows a state in which the powder raw material 3 is filled at the top for the fourth time, and FIG. 3 shows a state in which the powder raw material is compressed by the weight of the lid, the individual raw materials 3 and the separator 4 by covering the upper lid 21. Is shown. In this state, it is difficult to move the particles freely when aligning the easy axis directions of the individual powder particles with an external excitation field, resulting in deterioration of magnetic characteristics. In order to solve this problem, magnetic poles 51 and 50 are provided on the upper and lower sides as shown in FIG. 4, and a magnetic field is applied to the upper lid 21 and the lower lid 20 to extend the space where the particles are present, thereby widening the space for free movement of the magnetic raw material particles. As shown in FIG. 5, the upper and lower magnetic poles 51 and 50 are brought closer to the magnetic attractive force by sufficiently increasing the magnetic field strength to enhance the magnetic attractive force.

  In this process, various types of excitation fields can be freely reinforced by, for example, obliquely or by providing excitation coils around the periphery of the molding die such as a pulse type. In the old days, there are many documents such as patent application publication 47-21179 having both lubricity and adhesion, but unfortunately, if you try to increase the strength of the molding by adding an adhesive, the adhesive As a result, it becomes difficult to sufficiently align the easy magnetization axis, and sufficient magnetic properties cannot be obtained. At the same time, a molded product containing many adhesives is sintered. At the same time, a large amount of gas is generated, and at the same time, there is a defect that the decomposed residue of the adhesive becomes vacancies and decreases the density of the magnet, and ideally moves freely to the particles without the adhesive However, the present invention in which the molding is temporarily fired without worrying about the mechanical strength of the molded product can greatly contribute to the production of magnets from the viewpoints of economy and performance.

  Finally, one of the features of the present invention is that as shown in FIG. 6, the magnetic flux generated from the residual magnetic flux of the molded product 3 (compressed powder particles) molded in a magnetic field is not disturbed as much as possible. In addition, while maintaining the magnetic flux flow F as shown by the arrow, even if the molded product 3 is taken out of the mold, it is raised in a reducing atmosphere to a temperature at which it does not sufficiently collapse and calcined. Although this temperature differs depending on the composition of the powder raw material or the size of the particles, the calcination should generally be completed at 900 ° C. or lower. By this, the life of the molding die is so long and economical that it cannot be compared with the case where it is performed until the main firing.

  The pre-fired molded product is previously taken out from a molding die having a structure in which the contents can be easily taken out, such as a split mold, and a polymer having a relatively high decomposition temperature (Polyethyleneglycol 2000 molecular structure: H-CH2-CH2-O) ) N-OH molecular weight: 2000 g / mol) with a solvent (Diethylene Glycol Monobutyl Ether CH3OCH2CH2OCH2CH2OH molecular weight: 162.2 g / mol Boiling point: 230.6 ° C.) A mechanical alloying method is applied to a metal having an effect of increasing the coercive force, for example, a fine powder of Dy and one, or two or more kinds of fine powders of Al, Co, Ni, etc. After adhering a fine powder mixed well with By carrying out the main firing in the air or in a reducing atmosphere, Dy diffuses into the grain boundary phase and is expensive as known to preferentially diffuse with respect to the main phase of the temporary sintered body. Can effectively improve the coercive force by efficiently using Dy, and at the same time, the alloy of Al, Co, Ni, etc., which has strong rust prevention action on the surface of the Fe and Nd rich part, is baked by the alloying action. Alloying is performed during the main sintering in a vacuum or in a reducing atmosphere so that it is not necessary to perform the sintering.

  As detailed in the previous section, without using an expensive large-scale magnetic field molding machine, utilizing an economical magnetic field adsorption force, using a molding die with a simple molding machine, the easy axis of particles is a bonding agent, Put a lubricant, etc., and press-mold while adjusting without disturbing the movement of the particles, while the magnetic flux flow of the molding is the structure of the molding die made of a ferromagnetic material, while acting as a magnetic yoke, Temporary firing is performed without disturbing the magnetic alignment of the steel, and after the preliminary firing, the molded product is taken out from the mold, and Dy, Mo, V, etc. for improving the magnetic properties and Al, Ni, Co, which have a rust-proofing effect, are fine. In order to allow powder to be alloyed on the surface of the molded product, by performing main sintering in a vacuum or in a reducing atmosphere, it is possible to produce a magnet that is economically efficient and does not require surface treatment. is there.

  In the present invention, the energy composition of the magnet is high, and a typical composition not containing expensive Dy is expressed in mass%, and the alloy raw material is prepared by a predetermined method based on the composition of 31Nd-68Fe-1B (w%). The main component is an alloy material made of Ni, Co, Al, etc. of a ferromagnetic material having a magnetic yoke function that is generated from the molding after the molding of the present invention, after forming a melted and pulverized powder raw material As shown in a schematic cross-sectional view in FIGS. 1 to 3, the raw material powder 3 is sequentially filled through the separator 4 and the upper and lower magnetic poles 51 and 50 are fixed as shown in FIG. 4. In this state, a pulse or an alternating magnetic field is passed through the upper and lower lids 21 and 20 of the molding die, applied to the particles of the molding object, the easy magnetization axis is aligned, and the magnetized state is maintained while maintaining the magnetized state. Pressurize using the suction force and close the upper and lower lids 21 and 20 Dy and rust prevention to increase the coercive force on the surface of the calcined product after maintaining the digitized state and performing the calcining treatment in a vacuum or reducing atmosphere at 900 ° C. or lower with the molding object placed in the molding die In order to deposit one or more alloys of Al, Ni, and Co that have an effect, after coating the above-mentioned organic adhesive, a predetermined alloy fine powder such as Dy, Al, Ni, Co, etc. is deposited. When the treatment is performed in a vacuum or a reducing atmosphere at a main sintering temperature equal to or higher than the firing temperature, the effect of the present invention can be maximized.

  As shown in the cross-sectional views of FIG. 1 to FIG. Then, a hollow outer frame 1 is prepared, a lid having a thickness of 10 mm and a separator having a thickness of 5 mm, which can be inserted inside, are prepared, and filled in a molding die in accordance with the procedure described above with reference to FIG. Since the raw material powder filled with the separator's own weight is compressed and it is difficult to align the direction of the easy magnetization axis of the particles, the upper lid is positioned at the top of the outer frame of the molding die as shown in FIG. A magnetic pole is fixed, an alternating magnetic field of 10 KOe or more is provided on the outer periphery of the outer frame to provide a pulse excitation air core coil (not shown in the figure), and the magnetic force is applied as a molding pressure source. While applying, pressure molding was performed. Next, pre-baking is performed at 870 ° C. in a hydrogen atmosphere furnace while the object to be molded is placed in a molding die, the pre-baked product is taken out from the die and the surface is coated with an adhesive, and then the 2Dy-98Ni weight ratio is determined. As a result of adhering the alloy fine powder and sintering it in a hydrogen atmosphere furnace at 900 ° C. or higher and simultaneously alloying these Dy and Ni, Dy diffuses preferentially in the grain boundary phase, and the coercive force At the same time, Ni became a kind of metallizing mold for the surface of the sintered body, and surface rusting was prevented.

The molding die which is one of the apparatuses for magnet manufacture of this invention is shown with sectional drawing. The process of filling the magnetic powder raw material 3 through the separator 4 sequentially from the lower part to the molding die is shown. This example shows a state where powder raw materials are filled up to the fourth stage in order to obtain four molded products. This shows a state where it is difficult to move the powder when aligning the easy magnetization axis of the powder in a state where all the powder raw materials are compressed by the weight of the upper lid 21 and the separator 4 and the powder raw material 3. Magnetic poles 51 and 50 are fixed to the upper and lower surfaces of the outer frame of the molding die, and the upper lid is pulled up by various magnetic attraction forces. At the same time, the space filled with the powder raw material is sequentially expanded to align the easy magnetization axis of the powder. The state where the movement of the powder particles is made easy is shown. It shows a state where the magnetic poles 51 and 52 are unfixed and the upper and lower lids of the molding die are pressed by applying the magnetic attraction force. The upper and lower magnetic poles 51 and 50 are extracted, and the magnetic flux lines F generated from the molded product in the molding die are schematically shown in a state where they are maintained in the state of easy magnetization in the direction of magnetization. is there.

Explanation of symbols

1 Outer frame made of ferromagnetic material

20 Lower lid made of ferromagnetic material

21 Top cover made of ferromagnetic material

3 Fine powder raw material

4 Spacer made of ferromagnetic material

50 Bottom pole

51 Upper magnetic pole

F Magnetic flux flow

Claims (5)

  A method for producing a magnet, characterized by forming the particles by applying the attractive force while aligning the easy axis of magnetization of the particles with a magnetic force.   After the magnet powder is filled into the molding die, it is mounted on a molding machine that uses a magnetic attraction force as a pressurizing source, and an excitation force and an attraction force are exerted from an alternating current (including pulse) and direct current power source. A method for producing a magnet, characterized in that pressure molding is performed in a state where the directions of easy magnetization axes of magnet powder in the mold are aligned.   A molding die made of a material containing a ferromagnetic material is a magnetic material in which a magnetic flux flows so that the magnetization direction of a pressure-molded body made of a group of particles in which the easy axis direction of magnetization is aligned does not deviate from a desired direction. A magnet manufacturing apparatus having a function as a yoke.   4. The molding die according to claim 3, wherein the molding die is made of an alloy material such as Ni or Co that can withstand the temperature of temporary firing of the molded body.   Using a pre-adhesive or the like on the surface of the pre-fired product, well-known fine powder A of Dy, Mo, V for magnetic improvement, and one or more of Al, Ni, Co, etc. of the present invention The fine powder B composed of the above is sufficiently finely mixed to prepare an A + B powder, which is adhered to the surface of the product and subjected to heat treatment for the main sintering. A magnet manufacturing method characterized by diffusing into a field phase to improve coercive force and simultaneously preventing rusting with an alloy of Al, Ni, and Co.

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