JPH06124829A - Circular magnet and its manufacture - Google Patents

Abstract

PURPOSE:To provide a circular magnet, which is a permanent magnet, made of rare earth, transition metal and boron, and which is also a hot working magnet to which magnetic anisotropy is applied under hot working, with high energy product, improved flatness of magnetic characteristic accompanied. CONSTITUTION:The titled magnet is a circular worm working magnet, chiefly made of a transition metal T and is containing a rare earth element R, containing yttrium, and boron B, and has magnetic anisotropy, with its average grain size between 0.02-1.0mum. Manufacture of a circular magnet which has the maximum energy product of more than 42MGOe, the value obtained by dividing its wall thickness with the length in its axial direction is 0.2 or less, and the degradation amount of maximum energy product at the periphery of the magnet is 20% or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a warm-worked magnet which is a permanent magnet consisting essentially of rare earths, transition metals and boron, and which imparts magnetic anisotropy by warm working.

[0002]

2. Description of the Related Art RTB-based magnets, which are essentially composed of rare earths, transition metals, and boron, have been attracting attention because they are inexpensive and have high magnetic properties. However, this magnet is
-34242 and the sintered magnet disclosed in JP-A-60-10
It is roughly classified into the ultra-quenching magnet described in JP-A No. 0402. Regardless of which manufacturing method is used, it is necessary to mold into a desired shape, and it is difficult to intentionally control arbitrary magnetic characteristics in this molding process. For example, when trying to obtain magnetic anisotropy in a sintered magnet, a step of molding in a magnetic field is essential, and the shape is restricted by the molding direction and the orientation magnetic field direction. Although it is possible to control the magnetic characteristics in the magnet by controlling the orientation magnetic field strength, it is technically difficult and it is not a method that makes full use of the potential of this system magnet. Therefore, most arc-shaped magnets have a straight orientation. On the other hand, in the case of ultra-quenched magnets, molten metal of RTB-based alloy is solidified by the ultra-quenching method to obtain thin strips or flakes, crushed, hot-pressed, and then subjected to warm plastic working to impart magnetic anisotropy. These are permanent magnets (hereinafter referred to as "warm-worked magnets"), and the ribbons and flakes obtained by the ultra-quenching method further have innumerable fine crystal grains inside. Therefore, although the thin strip or thin piece obtained by the ultra-quenching method has an irregular shape with a thickness of about 30 μm and a side length of 500 μm or less, the crystal grains contained therein are 1 to 90 μm smaller than that of the sintered magnet. It is as fine as 0.02 to 1.0 μm, and it is possible to obtain essentially excellent magnetic characteristics close to the critical dimension of 0.3 μm of the single magnetic domain of the magnet of this system. In warm-working magnets, 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 having a required shape, it is possible to improve the orientation by allowing plastic flow to be carried out efficiently and sufficiently over the entire workpiece, which in turn makes it possible to produce a magnet with high magnetic properties. Become.

[0003]

As described above, in the sintered magnet, the means for anisotropy is forming in a magnetic field,
Although the potential of the magnetic properties of the material is at the same level as that of the ultra-quench magnet, it is difficult to manufacture a magnet that is long in the axial direction and thin in the thickness direction. That is, since the length is long in the axial direction, non-uniformity of pressure transmission occurs during molding in a magnetic field, resulting in non-uniformity of magnetic characteristics. In the manufacture of a magnet thin in the thickness direction, it was difficult to transfer fine powder into a mold, which was not suitable for mass production. For the above reasons, in the sintered magnet, it is difficult to manufacture an arc-shaped magnet whose value obtained by dividing the wall thickness by the axial length is 0.2 or less.
It was impossible to manufacture an arc-shaped magnet having the above magnetic properties and radial anisotropy. Therefore, in the case of a sintered magnet, a magnet larger than the required size and shape was previously formed and cut out by machining. As a matter of course, in this method, the material yield is poor and the cost increases. On the other hand, in the case of ultra-quenched magnets, the above problems are solved, but the plastic flow at the machined surface of the material, especially the outer peripheral edge, is disturbed by the friction between the punch and the workpiece during plastic working, which inevitably causes deterioration of the magnetic properties. It This problem can be improved to some extent by improving the lubrication of the punch and the work, but since it is impossible to eliminate friction, it is not a sufficient countermeasure. In addition, the following factors can be considered as factors that deteriorate the magnetic characteristics of the end portion of the arc-shaped magnet manufactured by the ultra-quenching method. According to the conventional method, the curvature of the upper and lower punches is determined based on a simple design in which the thickness of the arc-shaped magnet as the final shape is taken into consideration and the value is added to the radius of curvature of the lower punch. However, the pressing force applied for anisotropy is a component force in the vertical and parallel directions to the upper and lower punch surfaces, and the arc-shaped magnet with a larger divergence angle from the center of curvature has a stress acting perpendicular to the radial direction. The magnetic anisotropy increases and magnetic anisotropy is hard to be imparted. Therefore, it is an object of the present invention to obtain an arc-shaped magnet having high magnetic characteristics in the radial direction and substantially uniform magnetic characteristics by improving the processing method by making the best use of the characteristics of the warm-working magnet.

[0004]

DISCLOSURE OF THE INVENTION The present invention contains a transition metal T as a main component, a rare earth element R containing yttrium and boron B, and an arc-shaped magnetic anisotropic having an average particle diameter of 0.02 to 1.0 μm. It is a warm-working magnet with the property of 42M
A radial anisotropic arc-shaped magnet having a maximum energy product of GOe or more and a value obtained by dividing the wall thickness by the length in the axial direction is 0.2 mm or less. Further, the present invention is a radial anisotropic arc-shaped magnet, characterized in that the deterioration of the maximum energy product at the end of the product is 20% or less in the arc-shaped magnet. Further, in manufacturing the magnet, in a method of processing a warm-worked magnet in which plastic working is performed by upper and lower punches to give magnetic anisotropy, the radius of curvature of the outer R of the compacted compact is the final product shape. Method of manufacturing arc-shaped magnet characterized by being larger than radius of curvature of punch given, or manufacture of arc-shaped magnet characterized in that radius of curvature of radius R of a compacted compact is smaller than radius of curvature of punch Is the way. According to the conventional method, the inner and outer radii of curvature of the densified sample match the radii of curvature of the upper and lower punches, and the radius of curvature of the upper and lower punches is designed to be the inner and outer radii of curvature of the final product. In the arc-shaped magnet manufactured by this method, the magnetic characteristics of the outer peripheral end of the magnet are significantly deteriorated. In particular, the magnetic properties at the end portions in the circumferential direction are deteriorated by 20% or more as compared with the central portion. As a result of investigating this, it was found that the easy magnetization direction was deviated from the radial direction by about 15 degrees at the circumferential end. As a result, it was found that the magnetic characteristics at the circumferential end portion were deteriorated because the direction cosine corresponding to this deviation angle was obtained. That is, this phenomenon suggests that the plastic flow is inclined from the tangential direction toward the center due to the frictional force between the upper punch and the work, and it is confirmed that the flow of the flakes is actually that way. It was Therefore, the radius of curvature of the inside and outside of the sample, which has been densified in advance by allowing for a deviation from the ideal direction of the plastic flow at the outer peripheral edge, was designed as claimed.
With this design, it was possible to reduce the deterioration of the magnetic properties of the outer peripheral end of the magnet. Further, in the process of performing the warm working by the above method, the working may be divided into a plurality of times in order to suppress the generation of cracks on the outer peripheral portion, and the outer circumference may be restrained at each working rate. Further, in order to suppress the bulging phenomenon that occurs during warm working, the compact may be preformed into any shape. Further, a method of slowing the plastic deformation speed to the extent that the magnetic properties such as coercive force are not deteriorated may be adopted.

[0005]

【Example】

(Example 1) The arc-shaped magnet that was attempted to be manufactured had an axial length of 4
0 mm, inner R27.3 mm, outer R32.3 mm, divergence angle 90 degrees. An attempt was made to perform near net shape molding of a magnet of this shape by a sintering method, but it was difficult to transfer fine powder, and a gradient of magnetic characteristics was generated in the axial direction, and the degree thereof reached 20% or more. An alloy having a composition of Nd _13.5 Fe _bal Co _7.5 B ₆ Ga _1.25 was prepared by arc melting. This alloy was injected onto a single roll rotating at 20 m / sec in an Ar atmosphere to produce an irregular flaky flakes. 500 pieces of the obtained flakes
After roughly pulverizing to a particle size of less than or equal to μm to obtain a green compact, hot pressing is performed to obtain inner R27.3 mm, outer R32.3 mm and 36.
It was densified to 3 mm. Next, this compact is
Warm plastic working was performed between the upper and lower punches having the curvature of the final product shape at 50 ° C. to obtain arc-shaped magnets. From the arc-shaped magnet thus obtained, the magnetic characteristics were measured at every 10 degrees at the ends in the circumferential direction with the center at 0 degree by a BH tracer. In both samples, the maximum energy product was 43 MGOe or more in the range of the central angle of -30 to +30 degrees. From the measurement results, when the outer radius R of the compact is made to match the outer radius R of the final product as in the conventional case, the magnetic characteristics at the central angle ± 40 ° position, which is the end portion in the circumferential direction, deteriorates by 23% compared to the central portion. there were. On the other hand, in the sample in which the outer radius R of the compact was 36.3 mm, the deterioration in the circumferential end portion was 15%. As a result, the outside R of the compact
It has been found that the uniformity of the magnetic properties is improved by making the value R larger than the outer radius R of the final product. (Example 2) In the same manner as in Example 1, a consolidated body having an outer radius of 32.3 mm and an inner radius of 27.3 mm and 24.3 mm was prepared, and further, at 750 degrees, upper and lower punches having a radius of curvature of a final product shape were used. Warm plastic working was performed to obtain arc-shaped magnets.
From the arc-shaped magnet thus obtained, the magnetic characteristics were measured at every 10 degrees at the ends in the circumferential direction with the center at 0 degree by a BH tracer. From the measurement results, when the inner radius R of the compact is made to match the inner radius R of the final product as in the conventional case, the magnetic characteristics at the central angle ± 40 degrees, which is the end in the circumferential direction, are 25% compared to the central portion.
There was deterioration. On the other hand, in the sample in which the inner radius R of the compact was 24.3 mm, the deterioration in the circumferential end portion was 18%. As a result, it was found that the uniformity of the magnetic properties was improved by making the inner radius R of the compact body larger than the inner radius R of the final product.

[0006]

According to the present invention, it is possible to stably manufacture an arc-shaped magnet having an excellent magnetic property uniformity from the central portion to the end portion in the radial direction.

Claims (4)

[Claims] 1. Containing at least one rare earth element R containing a transition metal T as a main component and containing yttrium and boron B,
A warm-worked magnet having an arc-shaped magnetic anisotropy having an average particle diameter of 0.02 to 1.0 μm, having a maximum energy product of 42 MGOe or more, and having a wall thickness divided by an axial length. An arc-shaped magnet having a value of 0.2 or less. 2. The radial anisotropic arc-shaped magnet according to claim 1, wherein deterioration of the maximum energy product at the end of the product is 20% or less. 3. A rare earth element R containing a transition metal T as a main component and containing yttrium, and an RTB containing boron B.
The raw material is the RTB-based quenching thin piece obtained by quenching and solidifying the molten alloy of the system alloy. The raw material is pressed at a temperature of 500 ° C to 900 ° C to be densified, and then subjected to plastic working by the upper and lower punches. In the method of processing a warm-worked magnet that imparts magnetic anisotropy, the manufacture of an arc-shaped magnet characterized in that the radius of curvature of the outer R of the compacted compact is larger than the radius of curvature of the punch that gives the final product shape. Method. 4. An R-T-B containing a transition metal T as a main component and a rare earth element R containing yttrium and boron B.
The raw material is the RTB-based quenching thin piece obtained by quenching and solidifying the molten alloy of the system alloy. The raw material is pressed at a temperature of 500 ° C to 900 ° C to be densified, and then subjected to plastic working by the upper and lower punches. A method for manufacturing an arc-shaped magnet, wherein a radius of curvature of a radius R of a compacted compact is smaller than a radius of curvature of a punch in a method of processing a warm-worked magnet that imparts magnetic anisotropy.