JPH06188120A - Circular arc-shaped magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a circular arc-shaped magnet having excellent magnetic characteristics in the radial direction and substantially uniform magnetic characteristics. CONSTITUTION:An arcuated hot process magnet containing a transition metal T as the main element, rare earth element R including yttrium and boron B and having magnetic anisotropy with the mean grain size of 0.02 to 1.0mum, and a circular arc-shaped magnet having the maximum energy product of 42 MGOe or higher and a value of 0.2 or less which is obtained by dividing thickness with the length in the axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet substantially composed of a rare earth element, a transition metal, and boron. , The maximum energy product in the radial direction is 42M
It is more than GOe and the deterioration of the maximum energy product at the end is 20.
% Arc or less and the manufacturing method thereof.

[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 takes into consideration the thickness of the arc-shaped magnet which is the final shape, and the radius of curvature of the upper punch is a simple design in which 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 above magnet, in a method of processing a warm-worked magnet in which plastic working is performed by upper and lower punches to impart magnetic anisotropy, a radius of curvature smaller than the radius of curvature of the lower punch + the thickness of the final product is set. A method for manufacturing an arc-shaped magnet, characterized by using the upper punch, or a method for manufacturing an arc-shaped magnet, characterized by using a lower punch having a radius of curvature of the upper punch-thickness of a final product. According to the conventional method, the radius of curvature of the upper and lower punches takes into consideration the thickness of the arc-shaped magnet which is the final shape, and the radius of curvature of the upper punch is a simple design in which the value is added to the radius of curvature of the lower punch. 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 deterioration of the maximum energy product reaches as much as 20% at the ends in the circumferential direction as compared with the central part. 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 curvature radii of the upper and lower punches are designed in advance in consideration of a deviation from the ideal direction of the plastic flow of the outer peripheral end portion. 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 1) The arc-shaped magnet attempted to be manufactured has an axial length of 40 mm, an inner radius of 27.3 mm, and an outer radius of 3.
It is 2.3 mm and the spread angle is 90 degrees. We attempted near-net-shape molding of a magnet of this shape by a sintering method, but because the transfer of fine powder was difficult and the pressure transmission was uneven, there was a gradient in the magnetic characteristics in the axial direction, and the degree was 20% or more. Reached
An alloy having a composition of Nd13.5FebalCo7.5B6Ga1.25 was prepared by arc melting. This alloy in an Ar atmosphere 20
Injects onto a single roll rotating at m / sec to produce an amorphous frame
A flaky thin piece was prepared. The obtained flakes were coarsely pulverized to a size of 500 μm or less to obtain a green compact, which was then consolidated by hot pressing. Next, the green compact was subjected to warm plastic working between upper and lower punches having an arbitrary radius of curvature at 750 ° C. to obtain an arc-shaped magnet. The radius of curvature of the lower punch is constant at R = 27.3 mm, and the radius of curvature of the upper punch is R = 27.3, 32.3 mm.
I changed it. 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. Upper punch R27.3m
The central angle dependence of the magnetic properties at m and 32.3 mm are shown in FIGS. 1 and 2, respectively. Upper punch R32.3m
In the sample using m, the energy product at the position of ± 40 ° is about 23% lower than that at the center. on the other hand,
In the sample using the upper punch R27.3 mm, the decrease is about 15%, and the uniformity of the magnetic properties is excellent.

[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.

[Brief description of drawings]

FIG. 1 is a state of distribution of magnetic characteristics of an arc-shaped magnet according to the present invention.

FIG. 2 shows the distribution of magnetic characteristics of a comparative example of the present invention.

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Claims (4)

[Claims] 1. A warm-worked magnet containing a transition metal T as a main component, a rare earth element R containing yttrium and boron B, and having an arc-shaped magnetic anisotropy with an average particle diameter of 0.02 to 1.0 μm. And an arc-shaped magnet having a maximum energy product of 42 MGOe or more and a value obtained by dividing the wall thickness by the length in the axial direction is 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. A method for manufacturing an arc-shaped magnet, comprising using an upper punch having a radius of curvature smaller than a radius of curvature of a lower punch + a thickness of a final product in a method of processing a warm-worked magnet that imparts magnetic anisotropy. 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, comprising using a lower punch having a radius of curvature larger than a curvature radius of an upper punch minus a thickness of a final product in a method of processing a warm-worked magnet that imparts magnetic anisotropy.