JPS62104016A - Manufacture of anisotropic magnet - Google Patents

Abstract

PURPOSE:To easily obtain a diameter bipolar anisotropic magnet having the outer diameter similar to a perfect circle after the sintering by using a dice and a punch so that the external circumference of molding space becomes like an ellipse having the longer diameter in the magnetic field applying direction. CONSTITUTION:The internal wall 2 of dice is formed larger than the internal wall 3 of the prior art and the dice has the elliptical shape. Where, the maximum diameter is set in the M direction (anisotropic direction) and the minimum diameter is set in the direction crossing orthogonally the M direction. Namely, the internal wall of dice becomes like an ellipse defined by a=alpha1Xb where a is longer diameter in the M direction and b is short diameter in the direction crossing orthogonally the M direction. The punch may be designed adopting to the internal wall size of dice. Thereby, a diameter bipolar anisotropic ferrite system permanent magnet having the external diameter similar to a perfect circle can be obtained easily.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to MD.nFe1o1 (where M is Ba,
It is a hard ferrite permanent magnet whose main raw material is at least one of 8r, Pb, and n is 5 to 6.5. This relates to a manufacturing method.

[Conventional technology]

The hard ferrite magnet is Alnico Fe-Cr-C.

It is the most commonly used magnet because its raw material cost is lower than that of Co-Fe 411 stone.

Technically, in order to improve the performance of magnetic properties, there has been a shift from isotropy to dry anisotropy to wet anisotropy, and currently Sr-based ferrite magnets are the mainstream.

(Refer to Journal of the Japan Society of Applied Magnetics VO4, 6161) [Problems to be solved by the invention] However, the conventionally known literature does not mention in detail the structure of the mold used for molding, and - In actual mass production, the shrinkage rate between the molded body and the product is different in the anisotropic direction and the non-anisotropic direction, so if the mold is constructed using the conventional method, a large number of defective products will be produced. There was a problem. In other words, when forming with a die and punch that are close to a perfect circle, the shrinkage in the anisotropic direction is large due to subsequent heat treatment, so the outer diameter of the cross section viewed from the compression direction takes on an elliptical shape. Obtaining it was a karma. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method of manufacturing a bipolar anisotropic magnet having an outer diameter close to a perfect circle with precision.

[Failure to solve the problem]

The present inventors investigated the dimensions of the compact after molding (Lg) and the dimensions of the sintered compact after sintering (Ls), and found that the shrinkage rate (sh) in the anisotropic direction where a magnetic field is applied is different from that in the other direction. They found that this was relatively large and led to the present invention.

That is, the present invention provides a method for molding a hard ferrite-based bipolar anisotropic magnet in which a molding space is filled with magnetic alloy powder and a magnetic field is applied in the radial direction so as to be perpendicular to the compression direction to compression mold the magnet. The present invention is characterized by using a mold consisting of a die and a punch which constitute an elliptical molding cross section with the major axis in the anisotropic direction, or the aforementioned mold provided with a core pin if necessary.

[Function] To be more specific, the shrinkage ratio (Sh)m in the anisotropic direction exceeds 16%, but the shrinkage ratio (sh) in the other direction is less than 16%.

As an example, K to create a bipolar anisotropic magnet with an outer diameter (Ls) is (Sh)M -0,20 and the shrinkage rate in the direction farthest from the anisotropy direction is (Sh)o -0 , 14, the molded body dimensions (Lg) must each satisfy the following formula.

In equations (1) and (2), (Lg)M, (Lg)o
are the dimensions of the compact in the anisotropic direction and in the direction farthest from the anisotropic direction, respectively. From equations (1) and (2), (
3) Equation is obtained.

In formula (3), (ah) M-α20 and (Sh) o-α
Substituting 14 into 1- gives equation (4).

(Lg) M-1ρ且邊-x (Lg)0- t08 (
Lg, )O-(4)α80 From formula (4), if the shrinkage rate in the anisotropic direction is large, in order to obtain a cylindrical two-pole magnet with an outer diameter (Ls) in the sintered body, is the molded body size (Lg)o in the direction farthest from the anisotropic direction, that is, the direction perpendicular to the anisotropic direction, and the molded body size (Lg)M in the anisotropic direction is (Lg)M
It can be seen that it must be -α·(Lg)O-108(Lg)O. The coefficient α satisfies equation (5) and is preferably in the range of to2 to t22.

The above will be explained in more detail regarding the cylindrical magnets (FIGS. 1 and 2) and the cylindrical magnets (FIGS. 3 and 4).

In the figure, M indicates the anisotropy direction (magnetic field application direction).

All figures show molding space 1 inside the die as seen in the compression direction.
shows. There is also a core pin 8 in Figures 3 and 4.

FIG. 2 shows a conventional method, in which the inner wall 3 of the die is cylindrical. On the other hand, FIG. 1 shows a die according to the present invention, in which the inner wall 2 of the die is thicker (and elliptical) than the conventional inner wall 3. However, the inner wall 2 of the die is thicker (and has an elliptical shape). That is, the inner wall of the die according to the present invention has an elliptical shape in which the major axis in the M direction is 8 and the minor axis in the direction orthogonal to the M direction is a-α1xb. Just design it.

FIG. 4 shows a conventional method for producing a cylindrical magnet having a core pin 8. The die inner wall 5 and the core pin outer wall 7 are located concentrically and constitute a molding space 1. On the other hand, FIG. 3 is a die according to the present invention, and as described above, the inner wall of the elliptical die is 4 inches, with the short axis in the direction orthogonal to the M direction and the long axis a in the M direction, and a-false xb. Similarly, an elliptical core pin outer wall 6 having a short axis d in the direction orthogonal to the KM direction and a long axis C in the M direction, c-α3xd, is arranged concentrically to form the molding space 1. The punch may be made to fit the die inner wall 4 and core pin outer wall 6.

In addition, in Fig. 3, the cross-sectional shape of the core pin is elliptical, but since core pins are generally small, (b) d), c-
d (Also, the shape of the inner diameter part of the cylindrical magnet may be made into any shape as required. In the method described above, that is, in a mold in which the outer circumference of the molding space as seen from the compression direction is an ellipse) By molding, a ferrite permanent magnet with a bipolar anisotropy with an outer diameter close to a perfect circle can be easily obtained.The present invention can be applied to various methods.One of them is compression molding of only magnetic alloy powder. This is a method in which heat treatment is performed as required, and then impregnated with a binder (thermoplastic or thermosetting resin) and heated to solidify. It is a so-called sintered magnet, which undergoes heat treatment such as sintering and aging after molding.Also, binder (Aj, Cu) is used during molding.

The present invention is also applicable to a method in which a mixture of Pb-8n alloy, thermoplastic and thermosetting resin) and magnetic alloy powder is compressed and solidified by heating.

Next, the reason for limiting the components of the hard ferrite permanent magnet to which the present invention is applied will be explained.

The essential components are M (M is Pb, Bd, and Sr (both are type 1 co0 and Be, and as an ingredient display, (4), nFe
,01. However, n is a value of 5 to &5. KNa other than the above additives, 0. To, 0. CaO, MgO
,5i01,B@OH,Cr@0@+.

A.J., 0. At least one of these may be added in a total amount of 5 wt % or less for the purpose of improving magnetic properties.

It is preferable that the amount of harmful components such as MrO, CuO, NIP, etc. is as small as possible.

In addition to the above components, stearic acid and stearic acid M salt (M being Ca and Mg) are added for the purpose of improving moldability.

At least one of AJ, Zn, etc.) and PVA
The total amount of one or more selected among these may be 5 wt% or less.

〔Example〕

Next, examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1 8rCO@ and Fe 0@ were mixed in a ratio of 1:5.5, pre-calcined at 1300°C for 1 hour, and further pulverized to an average particle size of 1 μm using a ball mill.

In addition, as an additive before calcination, 3 wt% of Sin was added.
Added. 20 kg of the obtained fine powder slurry (moisture 50
%) K10% PVA aqueous solution was mixed.

This slurry was magnetized in a magnetic field of 5KOe and then dried for 6
It was crushed and sized to 0 mesh or less.

This powder was filled into the molding space shown in Fig. 1 (elliptical shape with a major axis of 52.4 m and a minor axis of 30.0 m), and a molding pressure of 1 to
Molded in a magnetic field (7KOe in the major axis direction) at ll/j,
A molded body was obtained. After molding, sintering was performed at 1240°C for 1 hour, and the product was subjected to measurement.

The results are presented in Table 1 as run@1.

Table 1 Comparative Example 1 Molding space shown in Figure 2 (Dice inner diameter -50,0-) i
The results were shown as Comparative Example 1 in Table 1, which was carried out in the same manner as in Example 1, except that c was used. As shown in Table 1, in the conventional method, the anisotropy direction is small and the variation in the outer diameter dimension is as large as t8■, whereas in the present invention (Example 1), α4
It was found that an outer diameter as small as ■ and close to a perfect circle could be obtained.

Example 2 Molding space shown in Fig. 3 (long axis 58.9 m, short axis 3 & 0 mm)
The results were shown in Table 1 as Example 2 in the same manner as in Example 1, except that the inner diameter of the die and the outer diameter of the core bin (major axis 195-1 minor axis 18.0-) were changed.

It can be seen that the variation in the outer diameter dimension is α5-, and the effect of the present invention is not lost even if a core pin is provided.

Example 3 The same procedure as in Example 2 was carried out except that the outer diameter of the core bin was changed to φ18.0-. The results are shown in Table 1 as Example 5.

Comparative Example 2 The molding space shown in FIG. 4 (inner diameter of the die -36 mm, outer diameter of the core bin 18 mm) was carried out in the same manner as in Example 1, except that K was changed, and the results are shown in Table 1 as Comparative Example 2. When a cylindrical magnet with bipolar anisotropy in diameter is molded in a molding space composed of a die inner diameter that is close to a perfect circle and a core bin outer diameter, the outer diameter variation in the method of the present invention (C1, 5■ in Example 2, It can be seen that the distance is larger at 2.1 m compared to 0.6 m in Example 3.

〔Effect of the invention〕

As described above, when molding is performed using a die and a punch in which the outer peripheral part of the molding space is an ellipse with the major axis in the direction of magnetic field application, the outer diameter becomes a perfect circle after sintering than K. A magnet can be easily obtained, and the industrial value of the present invention is extremely high.

[Brief explanation of drawings]

FIG. 1 is an example of the present invention, and is a view of the molding space viewed in the compression direction. FIG. 2 shows the conventional method. Figure 3 shows
FIG. 3 is a view of a molding space in the compression direction in an example of the present invention in which a core bin is provided. FIG. 4 shows a conventional method in which a core bin is provided. 1... Molding space, 2.3... Die inner wall, 4, 5... Die inner wall, 6, 7...
・Core bin outer wall, 8... Core bin 1st recess
2nd ward MM 1st 30th 4th Himon -ko-

Claims (1)

[Claims] 1. A method for forming a ferrite-based bipolar anisotropic magnet in which a magnetic field is applied in the diametrical direction perpendicular to the compression direction and compression molded, an ellipse whose major axis is in the anisotropy direction. 1. A method for producing an anisotropic magnet, comprising using a mold consisting of a die and a punch forming a shaped cross section. 2. A method of manufacturing an anisotropic magnet according to claim 1, characterized in that a core pin is used.