JPH01117003A - R-tm-b system radical an isotropic permanent magnet and its manufacture - Google Patents

Abstract

PURPOSE:To improve angluar quality which is not expected in conventional arts, and enable the mass production of anisotropic permanent magnet, by setting inner diameter roundness and angluar quality at the respective specified values. CONSTITUTION:An isotropic permanent magnet of cylindrical shape whose composition is rare earth(R), transition metal(TM) and boron(B) is formed. On that occasion, the inner radius roundess is set equal to or less than 0.085mm, and the angular quality is set larger than or equal to 10kOe. The inner diameter roundness is defined by the deformation quantity of inner diameter (maximum value of deviation with respect to an ideal circle). The angular quality is defined by the value of magnetization force when magnetic flux density becomes 90% of the residual magnetic flux density. Thereby, improving the angular quality which is not expected in conventional arts, and enabling mass production of an isotropic permanent magnet.

Description

[Detailed description of the invention] [Field of application in the reed industry] The present invention is directed to rare earths, transition metals, boron (hereinafter referred to as “R-TM-
It is abbreviated as BJ. ) type radially anisotropic permanent magnet and its manufacturing method, and particularly relates to one having good circularity and good squareness of the demagnetization curve.

[Conventional technology]

Stepping motor, linear actuator.

In magnetic coupling and the like, cylindrical permanent magnets with so-called radial anisotropy, in which the anisotropic direction of magnetization is radial, are often used. This is because the surface magnetic flux density can be higher than that of conventional isotropic permanent magnets. Therefore,
Radial anisotropic permanent magnets are in high demand as they can meet the above-mentioned needs for light, thin, short and small electronic instruments.

By the way, conventional radially anisotropic permanent magnets have been produced by molding permanent magnet powder in a magnetic field. This method is well known for rare earth cobalt magnets, and an improved method based on the same principle was proposed for R-TM-B permanent magnets as a new material (Japanese Unexamined Patent Publication No. 6
1-154118.

JP-A-61-284907, JP-A-62-11730
(Refer to each bulletin No. 5).

When radial anisotropic permanent magnets are used as rotors or stators in the above-mentioned electronic equipment, due to the trend of decreasing gap dimensions due to miniaturization, the roundness of the inner diameter of the cylinder is 1. There is also a strong demand for improved dimensional accuracy, and even at present there is a demand for a perfect circle*0.1 tm or less and a straightness d/D of 0.05 W or less.

[Problem that the invention attempts to solve]

However, in the limited molding method based only on the conventional magnetic field forming method, cracks tend to occur during sintering, and the current d/D method requires sintering with a low degree of orientation. 62-1173
This is because the radial orientation provides not only magnetic anisotropy but also mechanical anisotropy, which causes non-uniform shrinkage during sintering. Therefore, in the above-mentioned publication, the degree of orientation was limited to 70 to 98 degrees. In fact, according to additional tests conducted by the present inventor, cracking failure during sintering was severe in large ring anisotropic permanent magnets unless the degree of orientation was lowered to about 70%. Furthermore, the magnetic properties, especially the squareness of the demagnetization curve, are poor, and as a result, (BH)max cannot fully bring out the original potential of the material.
/D was the current situation.

Furthermore, in order to ensure the roundness of the inner diameter of the cylinder when it is assembled into a product, an internal grinding process is required after sintering, which is a major factor in increasing costs. Concerning the straightness of the cylinder, there was a problem with warpage during sintering, which caused a decrease in yield.

[Means to calendar problems]

Therefore, the present invention provides an R-TM-B radial anisotropic permanent magnet, which has an inner diameter roundness of 0.1 m or less and a squareness Hk of 10 kOe or more. R-TM-, which is characterized by a dial anisotropic permanent magnet and sintering in a restrained state, especially with a cylinder inserted in the inner diameter
This is a method for manufacturing a B-based radial anisotropic permanent magnet.

The present inventor has discovered that by sintering a molded body in a restrained state, the inner diameter roundness of the radially anisotropic permanent magnet is improved and the squareness of the demagnetization curve is improved. It is.

In the present invention, the inner diameter roundness is defined by the amount of deformation of the inner diameter (the maximum value of the deviation with respect to a perfect circle). In addition, the squareness Hk is the second quadrant (demagnetization curve) of the hysteresis curve of the permanent magnet.
It is defined as the value of the magnetizing force H when the magnetic flux density B becomes 90% of the residual magnetic flux density Br. A large swim value indicates good squareness; h l) (
BH) max is also large. In the R-TM-B filamentary anisotropic permanent magnet sintered in a restrained state in the present invention,
Although it is not certain whether or not the squareness will be improved, R-
In TM-B alloy, R-Co alloy (hexagonal system)
It is assumed that the stress field generated by restraint, especially the contribution of shear stress, is effective in developing good magnetic properties, which is different from the case of . Therefore, the effect of the present invention is not limited to the constraint of inserting a cylinder into the inner diameter surface of the cylinder. Note that the sintering used in the present invention generates bonding between particles using powder metallurgy. In addition to normal sintering, plastic working is also performed under high temperature conditions, also known as sintering (Japanese Unexamined Patent Publication No. 6
0-100402). In short, it is fine as long as it can be heated while being restrained.

Further, the raw material powder used in the present invention may be one obtained by pulverizing an R-TM-B casting alloy (see, for example, JP-A No. 59-46008), or one obtained by ultra-quenching (for example, JP-A-59-46008).
1859-64739), or a material obtained by ultra-quenching and consolidated by hot pressing etc. to cause plastic flow and completely impart magnetic anisotropy (% Kaisho 60
-100402)) may be re-pulverized.

The stress-induced anisotropy according to the present invention can also be emphasized by adding some stress during sintering.

The present invention will be specifically illustrated below based on Examples.

〔Example〕

(Example 1) Ndo, *Dyo, + (FebILtBo, os
Nbo, oss ) 5.7 A magnetic alloy with a composition of The average particle size was 5 μm. The powder is 28.5 in outer diameter x 20.7 in inner diameter x 25 in length (-)
The mixture was filled into a mold and molded in a transverse magnetic field of 2230 (G) (the direction of magnetic field application is perpendicular to the molding direction). 25 after molding
A ton mechanical press was used. Molding pressure is 0.7 to
'7, the magnetic field strength is 10.700 (Oe).

Here, after molding, the diameter (d) is 17.78 to 19.80k.
) in which 16 types of cylinders were inserted, and as a comparative example, hollow ones without any cylinders were created.

The obtained molded body was sintered at 1050° C. for 2 hours to a point '1' where the cylinder was inserted. The sintered body was subjected to two-step heat treatment at 900℃ x 2 hours and 600℃ x 1 hour.The inner diameter of the sintered body was 17.6-
The relationship between the ratio d/D to the inserted cylinder diameter d and the magnetic properties of the obtained permanent magnet is shown in FIG. Here symbol M/
The symbol M indicates the magnetic property in the direction parallel to the anisotropy direction, and the symbol M indicates the magnetic property in the direction perpendicular to the anisotropy direction.

It can be seen from FIG. 1 that the squareness Hk becomes 10 kOe or more when the diameter d/D ranges from 1.055 to 1.125. Also, (BH)max has improved to more than 17MGOe, and when d/D = 1, Hk is 11.6kOe in 08.
, (BH)rrljLX is 18.6MGOe, and the case of sintering without any conventional restraint is 7.8 (k
Oe), 16.6 (MGOe) and 1.
The increase of 48 times + (B H)max by 1.12 times is a significant effect.

In addition, as shown in Table 1, the inner diameter of the circular plate is 0.09 in the comparative example.
5 (,,), but it was reduced to about 0.06 (simplified). The number of samples is 10 for each diameter ratio.
The average value is 0. 7, Table 1 * Diameter ratio Q = 0 indicates the case of sintering in the conventional hollow state 0 From Table 1, when a cylinder is inserted into the inner diameter and restrained, the squareness Hk and (B H) Although the inner diameter roundness tends to deteriorate slightly when max is set within the preferred range, it is still found to be superior to that obtained by the conventional sintering method.

The degree of orientation of the product obtained according to the present invention was approximately 94 degrees, and no cracks were observed.

(Example 2) In the same manner as in Example 1, the squareness HkO value and the presence or absence of cracks were confirmed when only the degree of orientation was changed.

In this case, the diameter ratio of the inserted cylinder was selected to be 1.08. This result shows that in the present invention, a radially anisotropic permanent magnet with a high degree of orientation, sufficiently free from cracking, and good squareness (10 kOe or more) can be obtained.

Table 2 [Effects of the Invention] According to the present invention, there is an effect of improving squareness that was not previously expected, and it is possible to mass-produce radially anisotropic permanent magnets with high magnetic energy and capacity. Furthermore, good d/D can be obtained without internally grinding the inner diameter of the cylinder.

[Brief explanation of the drawing]

Claims (4)

[Claims] 1. The composition is rare earth (R), transition metal (TM), boron (B)
), the R-TM-B radial anisotropic permanent magnet is characterized by having an inner diameter circularity of 0.085 mm or less and a squareness Hk of 10 kOe or more. . 2. R-TM-B characterized by sintering in a restrained state
A method for producing a permanent magnet with radial anisotropy. 3. R-TM- according to claim 2, wherein the restraint is performed with a cylinder inserted into the inner diameter.
A method for manufacturing a B-based radial anisotropic permanent magnet. 4. The ratio d/ of the cylinder diameter d and the inner diameter D of the cylindrical shape
7. The method for manufacturing an R-TM-B radially anisotropic permanent magnet according to claim 6, wherein D is 1.01 to 1.125.