JPH04352402A - Circular arc-shaped magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To stably manufacture a circular arc-shaped magnet having high magnetic characteristic in a radial direction. CONSTITUTION:A circular arc-shaped magnet for a circular arc-shaped hot processed magnet formed of an R-T-B series quenched thin piece obtained by quenching and solidifying molten R-T-B series alloy containing transition metal T as a main ingredient, a rare earth element R containing yttrium and boron B, as a material and having magnetic anisotropy and 0.02-1mum of mean particle size by hot processing the material, wherein both ends of the circular arc shape is 120 deg. or less from the center of curvature of the circular arc.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to the improvement of a warm-worked magnet, which is a permanent magnet made essentially of rare earth elements, transition metals, and boron, and which imparts magnetic anisotropy through warm working, and is particularly strong in the radial direction. The present invention relates to an arc-shaped magnet having magnetic anisotropy and a method for manufacturing the same.

0002

2. Description of the Related Art RTB magnets, which are essentially composed of rare earth elements, transition metals, and boron, are attracting attention as they are inexpensive and have high magnetic properties. However, this type of magnets can be broadly classified into sintered magnets and ultra-quenched magnets as described in Japanese Patent Publication No. 61-34242. No matter which manufacturing method is used, it is necessary to mold it into a desired shape, and moldability is important. However, in order to obtain magnetic anisotropy in a sintered magnet, a process such as molding in a magnetic field is essential, and the shape is constrained by the molding direction and the orientation magnetic field direction. For example, in the case of vertical magnetic field molding (the direction of the magnetic field and the direction of press molding are parallel), a uniform magnetic field cannot be obtained within the mold cavity, resulting in uneven orientation of the powder and poor uniformity of magnetic properties. Further, even if the orientation is good due to the application of a magnetic field, the orientation will be disturbed again by molding, resulting in poor magnetic properties as a whole, and this is not a molding method that takes full advantage of the potential of the present magnet. On the other hand, in the case of transverse magnetic field forming (the magnetic field direction and the press forming direction are perpendicular), it is further divided into two types depending on the orientation direction. One is straight orientation and the other is radial orientation. In the case of straight orientation, the resulting sintered magnet is of course straight oriented and cannot have radial orientation. In the case of radial orientation, it is possible to obtain an arc-shaped magnet with near net radial orientation, but due to the low bulk density when filling the powder, it is necessary to fill the mold with a height that is about four times the height of the final product shape. It is necessary to invest in Therefore, press molding is extremely difficult and the orientation of the powder is poor, leading to non-uniform magnetic properties in the product. On the other hand, ultra-quenched magnets are made by solidifying molten R-T-B alloy by an ultra-quenching method, obtaining ribbons or flakes, pulverizing and hot pressing, and then warm plastic working to impart magnetic anisotropy. Permanent magnets (hereinafter referred to as "warm worked magnets") are described in detail in Japanese Patent Laid-Open No. 100402/1983. The ribbon or flake obtained by the ultra-quenching method further consists of countless fine crystal grains inside. Therefore, although the ribbons and flakes obtained by the ultra-quenching method have an irregular shape with a thickness of about 30 μm and a side length of 500 μm or less, the crystal grains contained inside the ribbons are about 1 to 90 μm thick than those of sintered magnets.
It is as fine as 0.02 to 1.0 .mu.m compared to m, and is close to the critical dimension of 0.3 .mu.m of a single magnetic domain in this type of magnet, so that essentially excellent magnetic properties can be obtained. In warm-worked magnets, a close correlation between plastic flow and magnetic alignment in the direction perpendicular to it is important. In other words, when producing a warm-worked magnet with a desired shape, the orientation is improved by efficiently and sufficiently applying plastic flow to the entire workpiece, which in turn makes it possible to produce a magnet with high magnetic properties. Become.

0003

[Problems to be Solved by the Invention] In the above-mentioned R-T-B warm-processed magnet produced by the ultra-quenching method, a special feature is that magnetic anisotropy is imparted by warm plastic working without using an orienting magnetic field. Moreover, since the magnetic anisotropy is imparted parallel to the pressing direction, it has been limited to a simple shape such as a flat magnet or a ring shape in which the C-axis direction is radially oriented by extrusion processing. Therefore, when producing a warm-processed magnet with an arcuate shape, the applied force is decomposed into force components perpendicular and parallel to the upper and lower punch surfaces, resulting in insufficient orientation and uneven magnetic properties. There is a possibility that it will become. Furthermore, since processing is performed on a surface with curvature, priority is naturally given to the direction of plastic flow, and since the tendency of anisotropy is fundamentally different from the simple flat plate shape described above, it becomes anisotropic both macroscopically and microscopically. involves a complex process. Therefore, it is not a good idea to blindly apply pressure between the upper and lower punches having curvature. Therefore, an object of the present invention is to establish a processing method for obtaining target characteristics and shape in producing an arc-shaped magnet having stable magnetic characteristics.

0004

[Means for Solving the Problems] The present invention provides R obtained by rapidly solidifying a molten R-T-B alloy containing a transition metal T as a main component, a rare earth element R including yttrium, and boron B. - Using T-B system quenched flakes as a raw material, this raw material is warm-processed to have an average grain size of 0.0 with magnetic anisotropy.
In a warm-processed magnet with an arc shape of 2 to 1 μm, both ends of the final arc shape are 120 mm from the center of curvature of the arc.
This is an arc-shaped magnet characterized by a diameter of less than . The pressing force applied for anisotropy is a force component both perpendicular and parallel to the upper and lower punch surfaces, so if the arc-shaped magnet extends more than 120 degrees from the center of curvature, the edge of the magnet will eventually Since more than 80% of the applied stress acts perpendicularly to the crystal grain anisotropy direction (the normal direction from the center of curvature), anisotropy is very difficult to form. Therefore 12
An angle of 0° or less is desirable. Further, the arc-shaped warm-processed magnet processed by this method is characterized in that the residual magnetic flux density in the direction perpendicular to the normal line drawn from the center of curvature of the arc is 6 kG or less at any part. For example, if the axis of easy magnetization is the radial direction, the maximum energy is 30M.
When trying to obtain an arc-shaped magnet with magnetic properties of GOe or higher, the residual magnetic flux density in the direction perpendicular to the normal line drawn from the center of curvature of the arc must be 6 kG or less for this type of magnet, as described above. It is a condition. In other words, in an arc-shaped magnet with a spread angle of 120° or more, it is difficult to make it anisotropic due to component forces, especially at the ends, and as a result, a product with high magnetic properties in the radial direction cannot be obtained. The present invention uses rapidly solidified R-T-B flakes obtained by rapidly solidifying a molten R-T-B alloy containing transition metal T as a main component, rare earth element R including yttrium, and boron B. In the method for manufacturing a warm-worked magnet, the raw material is pressurized at a temperature of 500° C. to 900° C. to densify it, and then subjected to plastic working with upper and lower punches to impart magnetic anisotropy, wherein the upper and lower punches are optional. The present invention relates to a method for producing an arc-shaped magnet, which has a curvature of In the present invention, it is desirable that the upper and lower punches have the same curvature as the final shape of the arc-shaped magnet. Furthermore, in order to suppress the occurrence of cracks on the outer periphery, a method may be adopted in which processing is divided into multiple steps and the outer periphery is restrained at each processing rate. Further, in order to suppress the bulging phenomenon that occurs during warm working, the compacted body may be preformed into an arbitrary shape and then finished into a predetermined shape in the final working. Furthermore, a method may be used to slow down the plastic deformation rate to an extent that does not significantly reduce magnetic properties such as coercive force. Furthermore, the present invention provides a sample in which the strain in the arc direction of the arc-shaped magnet after plastic deformation is 20% or more and 12%.
The present invention relates to a method for manufacturing an arc-shaped magnet characterized in that it is 0% or less. During warm plastic working, each fine crystal grain in the compacted body is flattened and made anisotropic while shifting its position relative to each other due to plastic flow, so it is preferable to give a degree of freedom in the arc direction. In other words, if no strain is applied in the arc direction, the strain will only occur in the longitudinal direction of the magnet, which will inhibit ideal flattening and make it impossible to obtain high magnetic properties. On the other hand, if a large degree of freedom is given, as the flattening of each crystal grain approaches its limit, it becomes relatively difficult to move and cracks are likely to occur. Therefore, in the arc direction of the arc shape, 20% or more 1
It is desirable to apply a strain of 20% or less.

[0005]

【Example】

[Example 1] Nd13.8FebalCo7.5B6G
An alloy having a composition of a1.25 was produced by arc melting. This alloy was jetted onto a single roll rotating at 20 m/sec in an Ar atmosphere to produce irregularly shaped flakes. The obtained flakes were coarsely pulverized to 500 μm or less to form a green compact, and then compacted using a hot press. Next, this compacted body was heated to 75
Warm plastic processing was performed between upper and lower arc-shaped punches at 0°C to form an arc-shaped magnet. The processing rate is such that the strain in the length direction and arc direction is constant at 80% for the same direction dimensions of the consolidated body, and in the arc direction, both ends of the magnet are from 0° to 1° from the center of curvature.
The shape of the compact and the dimensions of the mold were adjusted so that the angle was 60°. For the completed arc-shaped magnet, 3.2 mm square samples were cut out from positions where the spread angle from the center of curvature was 0°, θ/4, and θ/2. Next, the magnetic properties in the normal direction (radial direction) from the center of curvature and in the direction perpendicular thereto were measured using a VSM. The experimental outline and magnetic property measurement positions are shown in FIG. 1, and the obtained results are shown in FIG. 2. The residual magnetic flux density in the direction perpendicular to the normal direction from the center of curvature increases as the divergence angle θ increases, especially at 12
This tendency is remarkable for a and b when the angle exceeds 0°. On the other hand, the maximum energy performance in the normal direction (radial direction) shows the opposite tendency. From the above results, it can be seen that even if the same processing rate is given in the arc direction and length direction of the arc-shaped magnet, as the spread angle of the arc increases, it becomes difficult to achieve radial orientation. [Example 2] A compacted body was produced in the same process as described in Example 1, and then warm working was performed by changing the processing rate in the arc direction and length direction of the arc shape, and the relationship between the amount of strain and magnetic properties was determined. Examined. As another condition, the compacted body and the mold were adjusted so that the spread angle from the center of curvature was constant at 60°. A VSM was used to measure the magnetic properties, and the measurement position was at the end of the magnet corresponding to c in FIG. The results are shown in Figure 3. Arc direction (εθ) or length direction (εl)
When any one of them is constrained (ε=0), the overall peak value of the magnetic properties is low. However, as the degree of freedom is given in the length direction and the strain in the arc direction increases, the magnetic properties improve. When processed 120% only in the length direction, microcracks were generated at the ends, and when processed 140%, it was impossible to measure. On the other hand, cracks also occurred in the arc direction when the processing rate exceeded 120%.

[0006]

According to the present invention, arc-shaped magnets having high magnetic properties in the radial direction can be stably manufactured.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an outline of an experiment and measurement positions of magnetic properties.

FIG. 2 is a diagram showing the magnetic characteristics of an arc-shaped magnet in the normal direction from the center of curvature and in the direction perpendicular thereto.

FIG. 3 is a diagram showing changes in the maximum energy product in the radial direction with the amount of strain in the arc direction and length direction.

[Explanation of symbols]

1 Center of curvature of circular arc

Claims (4)

[Claims] Claim 1: R- containing a transition metal T as a main component, a rare earth element R including yttrium, and boron B.
R-T-B obtained by rapidly solidifying molten T-B alloy
In an arc-shaped warm-processed magnet with an average grain size of 0.02 to 1 μm that has magnetic anisotropy by warm-processing this raw material using quenched thin flakes as a raw material, both ends of the arc-shape are from the center of curvature of the arc. An arc-shaped magnet characterized by an angle of 120° or less. 2. An arc characterized in that the entire portion of the arc-shaped magnet according to claim 1 has a residual magnetic flux density of 6 kG or less in a direction perpendicular to a normal line drawn from the center of curvature of the arc shape. shape magnet. 3. R- containing a transition metal T as a main component, a rare earth element R including yttrium, and boron B.
R-T-B obtained by rapidly solidifying molten T-B alloy
The raw material is heated from 500°C to 900°C using rapidly quenched flakes.
A method for manufacturing a warm-worked magnet, in which the magnet is densified by pressing at a temperature of 1000, and then subjected to plastic working by applying pressure from upper and lower punches having curvature to impart magnetic anisotropy. 4. The circular arc according to claim 3, wherein the strain in the circular arc direction of the circular arc-shaped magnet after plastic deformation is 20% or more and 120% or less with respect to a sample obtained by densifying raw material flakes. Method of manufacturing shaped magnets.