JPH0220001A - Manufacture of rare earth element extremely anisotropic permanent magnet - Google Patents

Abstract

PURPOSE:To reduce thermal shrinkage amount, to prevent a permanent magnet from cracking, and to improve its productivity by performing a second stage sintering by employing a specific grain size distribution material and sufficiently raising the density of a compression molded piece. CONSTITUTION:Alloy powder represented by a formula R(Co1-x-y-zFexCuyMz)u (where R is rare earth element, M is one or more of Zr, Ti, Mn, Mo, Al, x is 0.1<=x<=0.3, y is 0.03<=y<=0.1, z is 0.005<=z<=0.04, u is 7.0<=u<=8.0) is compression molded in a magnetic field, sintered, and then pulverized to be so adjusted that mean grain size become 70-100wt.% of 10-50mum and 0-30wt.% of 3-9mum. The powder in which its grain size is sufficiently adjusted is filled in a cavity, a magnetic field is applied in an extremely anisotropic direction, and compression molded while orienting it. The molded piece is resintered at 1100-1250 deg.C, resolubilized, and age-hardened at 400-900 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a cylindrical magnet having high magnetic properties, particularly a sintered rare earth magnet oriented in a polar anisotropic direction.

(Prior Art and Problems) In recent years, increasingly high precision control has been required for robots and NC machines used in factory automation, as well as magnetic heads for picking up electromagnetic signals in computers, VTRs, and the like. For this reason, many servo mechanisms using stepping motors are being adopted, and the demand for multi-pole oriented cylindrical magnets is rapidly increasing.

Conventionally, the following three methods have been used to manufacture such cylindrical magnets.

B) A method of magnetizing an isotropic magnet in various ways on the inner or outer circumference (isotropic magnet); (Isotropic magnet) A method of magnetizing a radially oriented magnet with multiple poles on the inner or outer circumference. (Radial anisotropic magnet) c) Method of forming in a multipolar magnetizer, (Polar anisotropic magnet) The magnitude of magnetic force obtained by these methods is as follows: polar anisotropic magnet> radial anisotropic magnet> isotropic In order of sexual magnetism.

As for servo motors, it is easier to control a servo motor with a small inertia force, and in order to produce the same force, a smaller one is preferable, so in order to reduce the size and weight, a polar anisotropic motor that can generate a larger torque is recommended. Magnets are desired.

Conventionally, polar anisotropic magnets are produced by pulverizing a magnetic alloy ingot into fine powder, orienting it in the polar anisotropic direction, compression molding it, and sintering it into a solution at a temperature of 1000 to 1250°C.
This method is carried out by aging treatment at ~900°C, but this method has the problem that cracks occur during sintering and the yield is very low, making manufacturing extremely difficult.

The causes of this crack generation are as follows: 1) Density becomes uneven during compression molding due to the polar anisotropic magnetic field.

2) There is a difference in the coefficient of thermal expansion in the direction of easy magnetization and in the direction perpendicular to it, causing distortion.

This is thought to be due to the

An object of the present invention is to provide a polar anisotropic cylindrical magnet that does not generate cracks during the sintering process and does not cause a decrease in yield.

(Means for Solving the Problems) In order to achieve the above object, the present inventors have arrived at the present invention as a result of extensive studies, and the present invention has been achieved by combining magnetic powders with different particle sizes. The basic idea is to increase the density of the compression molded product oriented in the anisotropic direction and reduce the thermal shrinkage rate, and the gist is as follows: Formula R (Co1-x-y-tFexCuyMx) u
(In the formula, R is a rare earth element, M is Zr, Ti, Mn, M
o, one or more types of A I, X is 0.1≦x≦
0.3, y is 0.03≦y≦0.112 is o, oos
≦2≦0.04, U is 7.0≦u≦8.0) is compression molded in a magnetic field, sintered, and crushed to reduce the average particle size to 50μm is 70~10
0% by weight and 3 to 9 μm to 0 to 30% by weight, this prepared product is oriented in a magnetic field in the polar anisotropic direction or the radial direction, compression molded, and this molded body is 1100 to 1
A method for producing a rare earth polar anisotropic magnet, which comprises sintering at 250°C and then aging at 400 to 900°C.

The most important feature of the present invention is that the conventional manufacturing process is such that the magnetic alloy ingot is finely pulverized to 2 to 5 μm in step (1), oriented in the polar anisotropic direction in step 2, and compression molded to 100 ON1.
In contrast to the conventional method, which involves sintering and solution treatment at 250°C, aging treatment at 400 to 900°C, and post-processing such as cutting, cutting, and polishing in step 3, magnetization is performed to produce a product. Between the steps 1) and 2), as the IA) step, the magnetic alloy fine powder is compression molded in the direction perpendicular to the magnetic field, sintered and solutionized at 1100 to 1250°C in an argon atmosphere, and then,
This is coarsely crushed to give an average particle size of 10 to 50 μm.
The reason is that the particle size is adjusted so that 0% by weight and 3 to 9 μm become 0 to 30% by weight. Steps 2) and 3) may include compression molding, sintering, solution treatment, aging treatment, post-processing, and magnetization treatment in a polar anisotropic magnetic field, as in the conventional method.

By adding the IA) process to the conventional 1) process,
A sintered body with high saturation magnetization can be obtained, and even if it is crushed in the step 2), the magnetic poles in the coarse powder are uniformly oriented in one direction, so the next step 3) is molding in a magnetic field. In this case, even if coarse powder is used, high orientation can be obtained. Furthermore, by removing the aging treatment in step IA), the coercive force is suppressed, and high orientation can be obtained even if the orientation magnetic field is weak.

Due to the above-mentioned reasons for the pulverization in the IA) process, the average particle size of the pulverization in the l) process was reduced from 2 to 5 μm to 3 to 50 μm.
The particle size range can be expanded up to m, making it easier to further increase the density of the green compact through the next particle size adjustment. Next, the powder whose particle size has been sufficiently adjusted is placed in the cavity, and polar anisotropy is achieved. Compression molding is performed while applying a magnetic field in the direction and orienting the molded body. This molded body is re-sintered and re-solution treated at a temperature of 1100 to 1250°C, and then subjected to an aging treatment at a temperature of 400 to 900°C. As a result, the magnetic properties are comparable to those of the conventional method, and in addition, the density of the compact is increased by using coarse powder with a specific particle size range in step IA), which is a feature of the present invention. By reducing the thermal shrinkage rate, it has become possible to manufacture polar anisotropic permanent magnets that prevent the occurrence of cracks.

If the average particle size of 3 to 9 μm exceeds 30%, the amount of thermal shrinkage during sintering will increase and the incidence of cracks will increase. Furthermore, if a particle having an average particle size of 50 μm or more is used, the orientation will be disturbed and high Br will not be obtained.

By using coarse powder with this specific particle size range, the density after sintering is not as high as that using only fine powder,
The result is a porous sintered body and the residual magnetic flux density is a little low, but if this porous part is impregnated with a binder such as a thermosetting resin, the mechanical strength increases and productivity is greatly improved.

The raw material magnet alloy composition is expressed by the formula R(Cot-x-y-tFemcuyMj u
(In the formula, R is a rare earth element, M is Zr, Ti, Mn, Mo,
One or more types of AI, X is 0.1≦x≦0.3.
y is 0.03≦y≦0.1, Z is o, oos≦2
≦0.04, and U is 7.0≦u≦8.0.
Fe1oCui, 5Zra, s) t, ss, (
SmaoCeao) (Cots, 5Fer9.4C
ue, aZrt) t, zt, etc., and the manufacturing method of the present invention can be applied most efficiently to obtain high magnetic properties.

(Effects of the Invention) By the manufacturing method of the present invention, a polar anisotropic permanent magnet having high magnetic properties that could not be achieved by conventional methods can be obtained. In other words, the present invention involves forming and sintering fine powder, then coarsely pulverizing it,
After adjusting the particle size, it is oriented in the polar anisotropic direction, compression molded, sintered,
The two-step molding and sintering method involves solution treatment and aging treatment.In particular, the second stage of sintering uses a product with a specific particle size distribution, and the density of the compression molded product is sufficiently increased to reduce the amount of heat shrinkage. This prevented the occurrence of cracks and contributed to improved productivity.

Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

(Example 1) Sm (Coy xFe*occus, 5Zri, s
) An ingot with a composition of y, sa is made into a powder of 3 μm, oriented in a magnetic field, and compression molded in the perpendicular direction. This green compact is sintered and solutionized at 1220° C. for 1 hour (in an Ar atmosphere) and then coarsely crushed to an average particle size of 50 μm or less. This coarse powder is loaded into a cavity between a mold with a yoke and a core of a multi-pole magnetizer, magnetized, and pressed with upper and lower punches.Then, this molded body is heated to
) Re-sintered with Ir, re-solutionized at 1200°C x 30 minutes,
Aging treatment was performed at 00°C x 208r. Table 1 shows the characteristic values of the obtained polar anisotropic permanent magnet. This permanent magnet is made of a carbon steel tool and is easy to process, and because there is little dimensional change due to heat shrinkage, the amount of processing is extremely small.Furthermore, by impregnating the porous part with resin, it has improved impact resistance. It also got better.

(Example 2) An oriented sintered body having the same composition as in Example 1 was prepared with an average particle size of 3.
Crush to 0 μm. This coarse powder and a fine powder obtained by pulverizing this coarse powder and having an average particle size of 3 to 9 μm were mixed in a ratio of 8=2, and 0.1% by weight of stearic acid was added to the mixture, followed by molding and heat treatment in the same manner as in Example 1. Table 1 shows the characteristic values of the polar anisotropic permanent magnet obtained.

(Example 3) (SmaoCeao) (Cots, @Fete,
An ingot having a composition of 4 cua, aZrt) t, zt is crushed to 3 μm, oriented in a magnetic field, and compression molded in the perpendicular direction. This green compact was heated at 1170°C under an argon atmosphere.
℃XI) Ir sintering Next, this was
Grind again to the following. This powder has an average particle size of 3 to 9 μm.
The particle size is adjusted to 30% by weight and 70% by weight from 10 to 50 μm, and further, 0.1% by weight of stearic acid is added and mixed. Hereinafter, a polar anisotropic molded body was obtained in the same manner as in Example 1,
This molded body was sintered at 1170℃XIHr, and 1150℃X
Table 1 shows the characteristic values of the polar anisotropic permanent magnet obtained, which was subjected to solution treatment at 800° C. for 5 hours and aging treatment at 800° C. for 20 hours.

(Comparative example) An ingot with the same composition as in Example 1 was ground to an average particle size of 3 μm, and this fine powder was loaded into a cavity between a mold with a yoke and a core of a multipolar magnetizer, oriented in a magnetic field, and pressed with upper and lower punches. do. This molded body was sintered at 1220℃XIHr,
Solution treatment at 1200°C for 30 minutes and aging treatment at 800°C for 20 hours were performed. However, it cracked during sintering, so it was repaired with adhesive and the characteristic values were measured. The results are shown in Table 1.

No. table one

Claims (1)

[Claims] 1. Formula R(Co_1_-_x_-_y_-_zFe_
xCu_yM_z)_u (in the formula, R is a rare earth element, M is Z
One or more of r, Ti, Mn, Mo, Al,
x is 0.1≦x≦0.3, y is 0.03≦y≦0.1,
z is 0.005≦z≦0.04, and u is 7.0≦u≦8.
It is 0. ) The alloy powder shown by is compression molded in a magnetic field, sintered, and then crushed to have an average particle size of 10 to 50 μm but 70 to 1
00% by weight and 3 to 9 μm to 0 to 30% by weight, the prepared product was oriented in a magnetic field in the polar anisotropic direction or in the radial direction, compression molded, and this molded body was molded under an argon atmosphere. After sintering at 1100-1250℃, 400-900℃
A method for producing a rare earth polar anisotropic magnet, characterized by aging treatment at ℃.