JP3399056B2 - Manufacturing method of anisotropic magnet - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an anisotropic magnet, and more particularly to a method for magnetically anisotropically forming a compact of an amorphous powder by hot compression and plastic deformation. The present invention relates to an improvement in a method of manufacturing an anisotropic magnet. [0002] Generally, rare earth anisotropic magnets such as Fe-Nd-B magnets are classified into sintered crystalline anisotropic magnets and amorphous hot-pressed anisotropic magnets. It is roughly divided. [0003] A sintered crystalline anisotropic magnet is prepared by mixing and melting a predetermined raw metal element with a desired composition to form an alloy, pulverizing the solidified alloy, and forming the powder in a magnetic field. The molded body is made magnetically anisotropic by sintering and heat-treating the molded body in a furnace to adjust the crystal. On the other hand, an amorphous hot-pressed anisotropic magnet is manufactured by a process as shown in FIG. That is, first, as shown in (a), an amorphous powder produced by rapid solidification by an atomizing method or the like is press-formed in a forming die 2 provided in a heating furnace 1. Next, as shown in (b), after releasing the molded body 3 from the mold, as shown in (c), the molded body 3 is placed on a table 5a provided in the heating furnace 4, The ram 5b is lowered to plastically deform the molded body 3 by hot pressing. Then, a minute anisotropic crystal is crystallized inside the powder, so that the magnet 6 has magnetic anisotropy in a direction perpendicular to the direction of plastic deformation as shown in FIG. The related technology of this manufacturing method is disclosed in Japanese Patent Application Laid-Open Nos. 64-69006 and 4-6811. [0005] In the method of manufacturing an amorphous hot-pressed anisotropic magnet, since the magnet is pressed from a direction perpendicular to the plastic deformation direction of the magnet, A mountain-shaped pressure distribution occurs in the direction of plastic deformation as shown in FIG. Therefore, the pressure distribution produces a velocity distribution of the plastic flow as shown in FIG. 9, and the distribution of the plastic state becomes an anisotropic distribution as it is, which hinders the uniformization of the anisotropy and reduces the yield. There was a problem that the productivity was worsened. In view of the above problems, it is an object of the present invention to make the pressure distribution and the flow velocity distribution in plastic deformation uniform, to make the magnetic anisotropy uniform, and to improve the productivity. An object of the present invention is to provide a method for manufacturing an anisotropic magnet. [0007] In order to achieve the above object,
The method for manufacturing an anisotropic magnet according to the present invention is characterized in that a mold having an upper and lower punch in which a pressing surface is inclined with respect to a pressing axis at an angle of less than 60 ° from a horizontal is formed by rapidly solidifying amorphous powder. Hot pressing while applying shearing force at
The magnetic anisotropy is caused by plastic deformation. According to the above construction, the upper and lower punches for hot press plastic deformation have their press surfaces inclined with respect to the press shaft at an angle of less than 60 ° from the horizontal. By inclining the pressurized surface in this way, the flow velocity in plastic deformation becomes uniform, and the pressure distribution becomes uniform along with this. Therefore, if the plastic state is uniform, minute anisotropic crystals are uniformly crystallized inside the densified powder, so that the magnetic anisotropy is also made uniform. As a result, the yield of the anisotropic magnet is improved, and the productivity is improved. The reason why the inclination angle of the pressing surface of the upper and lower punches is set to less than 60 ° from the horizontal is as shown in FIG.
When the inclination angle θ is 60 ° or more, the plastic deformation of the formed body is difficult to be uniform, the shearing force is locally concentrated, and the magnetic flux density B
This is because r decreases. A preferred embodiment of a method for manufacturing an anisotropic magnet according to the present invention will be described below in detail with reference to the accompanying drawings. In the method of manufacturing an anisotropic magnet of this embodiment, first, an amorphous powder is produced by rapidly solidifying a rare earth alloy such as an Fe-Nd-B alloy by an atomizing method or the like. Next, as shown in FIG. 1, the amorphous powder is hot-pressed in a mold 11 provided in a heating furnace 12. As shown, the molding die 11 is provided in a heating furnace 12, and includes upper and lower punches 13a and 13b for pressing and molding amorphous powder.
and a cylindrical mold 14 which surrounds the periphery of a and 13b and guides its movement. In the present embodiment, the heating furnace 12 is provided around the molding die 11, but the invention is not limited to this, and the molded body may be directly heated by energization. The faster the flow rate due to plastic deformation is, the better the heating efficiency is when heating by energization, so that the flow rate can be increased. [0014] The heating temperature is, as shown in FIG.
At a temperature of 0 ° C. or more, the plastic deformation rate becomes remarkably high,
If the temperature is 0 ° C. or higher, the Fe component is separated, so that the temperature is preferably 500 ° C. or higher and lower than 800 ° C. In this case, 50
The temperature is raised at a rate of ~ 400 ° C / min, especially 250 ° C / m
A heating rate of about in is preferred. Further, as shown in FIG.
The upper and lower punches 13a and 13b tilt the pressing surface F with respect to the pressing shaft S at an angle θ of less than 60 ° from the horizontal.
That is, each pressing surface F of the upper and lower punches 13a and 13b
Are inclined at the same angle θ in the same direction in a state where they face each other.
When the pressing surfaces F of the upper and lower punches 13a and 13b are inclined in this way, as shown in FIG. 4, as the inclination angle θ increases, the magnetic flux density Br at each deformation rate in the thickness direction increases. However, as shown in FIG.
° or more, the plastic deformation of the molded body is difficult to be uniform,
The shearing force concentrates on a local portion (for example, only the central portion), and the magnetic flux density Br decreases. Therefore, in order to forcibly generate a uniform shearing force, the inclination angle θ is preferably in a range from horizontal to less than 60 °, and a range of 10 to 50 ° is considered effective from the viewpoint of controllability. [0016] The pressing force is 100 to 1500 kg / c.
Although it can be set within the range of m ² , as shown in FIG.
It is preferable to select the temperature within the range of 250 to 500 kg / cm ² according to the set temperature. More specifically, hot pressing by the upper and lower punches 13a and 13b is performed by placing a preformed body 15 on a lower punch 13b provided in the heating furnace 12 and lowering the upper punch 13a. Thus, the compact 15 is plastically deformed. As a result, fine anisotropic crystals are uniformly crystallized inside the densified powder, so that a uniform magnetic anisotropy is generated. Next, the operation of the above embodiment will be described. As described above, the pressing surfaces F of the upper and lower punches 13a and 13b provided in the molding die 11 for hot-pressing plastic deformation of the amorphous powder compact 15 have an angle of less than 60 ° from the horizontal. It is inclined with respect to the pressing axis S. The reason why the pressing surface F is inclined in this way is to make the flow velocity in plastic deformation uniform, and when the flow velocity becomes uniform, the pressure distribution also becomes uniform. That is,
If the plastic state is uniform, fine anisotropic crystals are uniformly crystallized inside the densified powder, so that the magnetic anisotropy can be made uniform. Therefore, an anisotropic magnet can be manufactured with a high yield, so that its productivity can be improved. Further, in order to clarify the operation and effect of the method for manufacturing an anisotropic magnet according to the present invention, a comparative study will be made with related prior art. First, a comparison is made with "a method and apparatus for manufacturing a magnetic anisotropic magnet material" disclosed in Japanese Patent Application Laid-Open No. 1-139736. This prior art is mainly intended to have polar anisotropy in the radial direction and to perform extrusion in a ring shape. Therefore, in order to perform extrusion in a ring shape in this prior art, a lower punch having a tapered central portion is necessary, but in the present invention, both the upper and lower punches 13a and 13b have a pressing surface F having an inclination angle θ. . In the extrusion, as in the injection molding of plastics, there is a problem of the flow and remaining of the molding material. Therefore, it is a natural idea that the tip of the lower punch has a conical shape as seen on the injection shaft of plastics. That is, this prior art emphasizes the fluidity of the molding material in extrusion, and it is clear that the purpose and action and effect are different from the generation of the forced shear force which is the main object of the present invention. Note that similar conditions such as a heating temperature, a pressing force, and a deformation rate are disclosed, because the raw materials used are similar. Next, comparison will be made with "anisotropic magnet and method for producing the same" disclosed in JP-A-4-98804. In this prior art, the inclination angle is 4 with the vertical direction being 0.
Although it is set at 5 to 85 °, in the present invention, it is 60 ° from the horizontal.
The pressure surface F has an inclination angle θ of less than 0 °. Although seemingly similar technology, this prior art is intended mainly for roll rolling, and was created from the need to maintain the roll position of a sample during rolling. On the other hand, the present invention differs in the function and effect from the point that the present invention was created mainly for uniform magnetic anisotropy by making the pressure distribution and flow velocity in plastic deformation uniform by generation of forced shear force. It is clear to do. Therefore, it is believed that the present invention is different from these prior arts and has sufficient difficulty in construction due to distinct differences in purpose and effect. As described above, according to the method of manufacturing an anisotropic magnet according to the present invention, the pressure distribution and the flow velocity distribution in plastic deformation are made uniform, and the magnetic anisotropy is made uniform. And an excellent effect that the productivity can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an entire molding die used in an embodiment of a method for manufacturing an anisotropic magnet according to the present invention. FIG. 2 is a schematic diagram showing a main part of FIG. FIG. 3 is a graph showing a relationship between a temperature and a plastic deformation rate in this example. FIG. 4 is a graph showing a relationship between a deformation rate and a magnetic flux density in the present embodiment. FIG. 5 is a graph showing a relationship between an inclination angle and a magnetic flux density in the present embodiment. FIG. 6 is a graph showing a relationship between a temperature and a pressure required for plastic deformation in this example. FIG. 7 is an explanatory view showing an example of a conventional method for manufacturing an anisotropic magnet. FIG. 8 is an explanatory diagram showing a pressure distribution state in an example of a conventional method for manufacturing an anisotropic magnet. FIG. 9 is an explanatory diagram showing a flow velocity distribution state in an example of a conventional method for manufacturing an anisotropic magnet. [Description of Signs] 11 Mold 12 Heating furnace 13a Upper punch 13b Lower punch 14 Mold 15 Molded body θ Inclination angle S Pressure axis F Pressure surface

Continuing from the front page (72) Inventor Masayuki Kato 8 Dosana, Fujisawa-shi, Kanagawa Prefecture, Isuzu Central Research Laboratory Co., Ltd. (72) Inventor Hideo Ishiyama 8, Isuzu Central Fujisawa-shi, Kanagawa Prefecture, Isuzu Central Research Laboratory Co., Ltd. (72) ) Inventor Makoto Ogawa 8 Tsurana, Fujisawa-shi, Kanagawa Prefecture Isuzu Central Research Laboratory Co., Ltd. (56) References JP-A-5-135976 (JP, A) JP-A-62-247056 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01F 41/02

Claims (1)

(57) [Claims 1] A molding die having upper and lower punches in which an amorphous powder produced by rapid solidification is inclined at an angle of less than 60 ° from a horizontal with respect to a pressing axis. A method for producing an anisotropic magnet, characterized in that magnetic anisotropy is generated by plastic deformation by hot pressing while applying a shearing force inside the magnet.