JPH04147605A - Manufacture of rare earth iron-boron permanent magnet - Google Patents

Abstract

PURPOSE:To manufacture a high performance uniform magnetic characteristic rare earth-iron-boron permanent magnet by using a plurality of raw materials having different grain growth speeds with respect to processing temperature as the raw materials before hot processing. CONSTITUTION:Stock material powder in which a grain growth speed is low with respect to temperature and fine crystal grain sizes are likely to be yielded is a raw material to which there is added about 0.2 to 2 atomic % of Ga, Ti, Zr, Si, Hj, and Ta for example. For example, the raw material is raw material powder in which contents of a rare earth element are properly controlled. Raw material powder different in supercooling upon quenching is a material which is made amorphous by raising the supercooling for example. For example, raw material powder completely crystallized in a quenching state by reducing the supercooling for example. Where a large- sized anisotropic magnet is manufactured, there may be used raw material powder reduced in coersive force after hot processing for a part in contact with a die inner wall upon hot processing when a preliminary molded structure in cold processing, while there may be used at the magnet center a raw material in which the absolute value of the coersive force is relatively greater and the growth speed of the crystal grain is medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a rare earth-iron-boron permanent magnet with high performance and uniform magnetic properties.

[Conventional technology]

Rare earth-iron-boron permanent magnets are conventional high-performance rare ±l
! The market demand for magnets has been increasing in recent years because they have higher magnetic properties than rare earth cobalt magnets. Particularly in the field of voice coil motors, which are magnetic head drive devices used in external magnetic storage devices such as large-scale computers, rare earth-iron-boron magnets are now being used as the majority of magnets. Furthermore, as a new use for rare earth magnets, demand for large magnets used in magnetic circuits such as wigglers, undulators, and linear motor cars has increased in recent years. The performance required of permanent magnets used in these applications is that they have a high energy product, and uniformity of the magnet is also an important performance.

In these application fields, rare earth-iron-boron magnets or rare-earth cobalt magnets using powder metallurgy are currently used.

[Problem to be solved by the invention]

However, the maximum energy product obtained by these magnets is approximately 38 MGOe at most. In addition, rare earth magnets produced by powder metallurgy are produced by orienting fine magnet powder in a mold using a magnetic field, cold-opening it, sintering it at high temperatures, and then heat-treating it, but the weight of a single magnet exceeds 500g. There are various technical problems with such large magnets. First, when a large magnet is magnetically formed in a mold, variations in the degree of orientation are unavoidable because the magnetic field distribution in the mold is not uniform.As a result, the residual magnetic flux density varies by about 5% within the product. is unavoidable.

The second problem is that when large permanent magnets are sintered at high temperatures, the shrinkage rates in the C-axis direction and C-plane direction are different, so if the temperature distribution in the furnace is poor, problems such as warping may occur. This may cause a decrease in yield. The third problem is that in the case of sintered magnets made by powder metallurgy, appropriate coercive force is imparted through heat treatment, but in the case of large magnets, the thermal history is different between the inside and the surrounding area of the magnet, and the cooling during cooling. Since the speeds are different, there is a drawback that the coercive force inevitably varies by about 10 to 20% between the inside of the magnet and the periphery.

Particularly in the case of rare earth-iron-boron magnets, the temperature coefficients of coercive force and residual magnetic flux density are large, and such variations in coercive force are a constraint on application. On the other hand, as a new manufacturing method for rare earth-iron-boron magnets, amorphous or microcrystalline ribbons or powder obtained by supercooling methods such as quenching of molten metal are used as raw materials, and warm pressure sintering or plastic working is used. , methods of obtaining isotropic or anisotropic magnets have been proposed. Various proposals have been made regarding the manufacturing method of this new rare earth-iron-boron magnet. For example, in JP-A-2-94604, the present inventors added an organic compound as an internal lubricant to create a high magnetic field of 40 MGOe or more. It has acquired characteristics. They also proposed an invention that improved the residual magnetic flux density by improving the external lubrication side and the processing method. However, Wiggler,
When manufacturing large magnets such as undulators and linear motor cars, there is a problem that, like sintered magnets, a variation in coercive force of 10 to 20% between the center and the outer circumference of the magnet cannot be avoided. This is because the coercive force of a rare earth-iron-boron magnet basically depends on the size of the individual crystal grains that make up the magnet. Therefore, in order to obtain a uniform coercive force throughout the magnet, it is important to make the temperature distribution of the workpiece as uniform as possible during warm working and to make the crystal grain size as uniform as possible. However, since the workpiece is warm-processed while being externally heated, a certain degree of temperature difference between the center and the outer circumference of the magnet is unavoidable in the case of large magnets. Since the growth rate of crystal grains is generally proportional to a logarithmic function of temperature, this is a factor that causes non-uniformity in crystal grain size between the outer periphery and the center of the magnet. In order to solve this problem,
For example, it is possible to make the temperature distribution of the workpiece uniform by taking sufficient preheating time before warm working, but in this case, the crystal grain size of the entire magnet becomes coarse and the overall coercive force decreases. Become.

[Means to solve the problem]

In order to solve these problems with the conventional technology, the present inventors used multiple raw materials with different grain growth rates with respect to the processing temperature as raw materials before warm processing, thereby increasing the coercive force even in large magnets. We have discovered that high-performance permanent magnetic force with uniform residual magnetic flux density can be obtained. In the present invention, the plurality of raw materials having different grain growth rates are, for example, raw material powders having different compositions, for example, raw material powders having different degrees of supercooling during rapid cooling. For example, Ga
, Ti, Zr, Si, Hj, Ta, 0.2
It is a raw material to which about 2 atomic % is added, for example, a raw material powder in which the content of rare earth elements is appropriately controlled.

Raw material powders having different degrees of supercooling during quenching are, for example, materials that have been made into an amorphous state by increasing the degree of supercooling, and are, for example, raw material powders that have been completely crystallized in a quenched state by reducing the degree of supercooling.

For example, when manufacturing a large anisotropic magnet according to the present invention,
It is sufficient to use raw material powder that has a small coercive force drop after warm processing for the part in contact with the inner wall of the mold during cold preform forming, and for the part in contact with the inner wall of the mold during special hot processing, while at the center of the magnet, the absolute coercive force It is sufficient to use a raw material with a relatively large grain size and a medium grain growth rate.As a method of distributing such different types of powder, the raw material powder with a slow grain growth rate is first placed in the mold during cold growth. After adding a certain amount, a certain amount of raw material powder with a medium grain growth rate is added as an intermediate layer, and then a raw material powder with a slow grain growth rate is added and cold-formed to create a preform with a sandwich inch structure. It is possible to mold the body. In addition, when distributing raw material powder with a slow crystal grain growth rate to the outer periphery of the preform, it is necessary to set a threshold in the mold cavity when raw material is introduced during cold-open molding. It is possible to produce a preformed body in which a raw material with a medium grain growth rate is bonded inside a raw material with a slow grain growth rate. Further, the present invention also includes a preformed body in which the above two methods are combined and a core material is arranged with a raw material having a medium grain growth rate.

By pressure-sintering the preformed body at, for example, 650 to 750''C, and then subjecting it to plastic working at 700 to 750''C, it is possible to manufacture a permanent magnet with uniform coercive force throughout the magnet.

The present invention will be described in detail with reference to Examples below.

〔Example〕

(Example 1) A super-quenched ribbon of NdHaFebalCOsGao and sBb was used as a molten metal window.

Produced by cold method (single roll method). (Powder A) On the other hand, N
d I L 5Feba l Co? , 5Gao,
Super 2 cold ribbons of sTj o and sBb were produced. (
Powder B) These two types of powder were placed in a container with a diameter of 60a+s and a depth of 100sn.
Inside the mold with a cavity of well diameter 3oIIIl
The sills are arranged in concentric circles, and powder A is placed on the inside of the sills.
After filling the outside of the sill with a certain amount of powder B, the sill was pulled out on a vertical line and then molded at a molding pressure of 3), /cd to produce a preformed body with a diameter of 60IIIl and a height of 6oIllI11.

This preform was heated at 650 ”C to 0.5 toy/d.
After pressure sintering under the pressure of , diameter 1
A magnet body with a height of 201IIll and a height of 10ml was obtained. - As a comparative example, only powder A (B) was used, and the diameter was 60 m.
A preformed body with a diameter of 120 ns and a height of 10 mm was obtained in the same manner as in the example.

The upsetting magnet obtained in this way is placed in a straight line including the center.
It was divided into two parts, the coercive force of each was measured, and the distribution of coercive force on the center line was investigated. Similarly, the coercive force distribution of comparative materials was investigated, and the results are shown in FIG.

As is clear from FIG. 1, by using the preform according to the present invention, an ultra-quenched magnet having a uniform coercive force throughout the magnet can be obtained.

(Example 2) Ultra-quenched ribbons of Nd+a, 5FebafCO7, 5Ga+, and Ji were produced by a single roll method. The cooling section speed during quenching of the molten metal is 25 m/sec for one and 10-7 for the other.
Seconds.

These two types of super-quenched ribbons were heat-treated in a temperature range of 650 to 800° C. for 30 minutes to examine temperature changes in coercive force of the super-quenched ribbons. The results are shown in Figure 2. The coercive force of the ribbon rapidly cooled at 10 m/s decreases above 750°C, but the coercive force of the ribbon rapidly cooled at 25 s/s reaches 800°C.
It can be seen that it has a relatively high coercive force. Using these two types of ultra-quenched ribbons, φ60Ilst 4
A cold preformed body having a 7-inch Santoinchi structure was produced. Magnetic powder obtained by pulverizing a thin ribbon obtained by rapidly cooling a molten metal at 10 M/sec is placed in the center of the cold preform, and thin ribbons obtained by rapidly cooling a molten metal at 25-7 seconds are placed at both upper and lower ends of the cold preform. Pulverized magnetic powder was used. This preformed band having a sandwich structure was pressure sintered at 700'C, and φ3C1+mXf
A compacted body of 30 m was obtained. As a comparative example, a similar compacted body was produced using only the powder obtained by rapidly cooling the molten metal at 25 m/sec. This compacted body was divided into five parts in the length direction, and the distribution of coercive force in the length direction was measured. The results are shown in Figure 3. As is clear from FIG. 3, according to the present invention, a magnet with uniform coercive force can be obtained.

(Example 3) Ultra-quenched ribbon (A) with a composition of Nd+JebafCO7,5Gao, sBb and Nd14FebafICo7,5G
An ultra-quenched ribbon (B) having a composition of ao, svO, and SB6 was produced in the same manner as in Example 1, and coarsely ground to obtain magnetic powder of 500 μm or less. These two types of powder were filled so that the A powder was placed in the core of the preform, and the B powder was placed in the outer periphery. A preform of 80+m was obtained. This preform was subjected to upsetting processing in two steps in the same manner as in Example 1 to a final processing rate of 75%.

Mouth 120 +++mX f! An anisotropic magnet of 1311111 was obtained. From each part of this magnet, the mouth 10mmX i
A 13#1m test piece for coercive force measurement was cut out and the distribution of coercive force in each part of the magnet was examined. The results are shown in Figure 4 in comparison with comparative materials.

〔Effect of the invention〕

According to the present invention, it has become possible to manufacture large-scale super-quenched rare earth-iron-boron permanent magnets with uniform magnetic properties, especially coercive force, which were previously impossible, such as wigglers, undulators,
It can be applied to linear motor cars, etc.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the distribution of coercive force of the permanent magnet according to the present invention, FIG. 2 is a diagram showing the relationship between upsetting temperature and coercive force,
FIG. 3 is a diagram showing the coercive force distribution, and FIG. 4 is a scatter diagram showing the coercive force distribution in the sample. Figure 1 Sample division position Figure 2 Upsetting temperature (C) Figure 3 BCDEF Figure 4 Numbers indicate coercive force

Claims (1)

[Claims] 1. Ultra-quenched ribbon made of amorphous or microcrystalline or a mixture thereof, obtained by solidifying a magnetic alloy mainly composed of rare earth elements, iron, and boron in a supercooled state such as quenching of a molten metal. Alternatively, magnet powder obtained by pulverizing the powder to 500 μm or less is cold-formed to form a preform, and then isotropically formed by warm pressure sintering or warm pressure sintering followed by warm plastic working. Alternatively, in a method for manufacturing a rare earth-iron-boron magnet for manufacturing an anisotropic magnet, the rare-earth-iron-boron magnet is characterized in that two or more types of magnetic powders having different compositions are laminated and molded during cold forming. A method of manufacturing permanent magnets. 2. In the method for producing a rare earth-iron-boron permanent magnet alloy as described in claim 1, two or more types of magnetic powders having different degrees of supercooling are laminated and formed in advance during cold preforming. A method for manufacturing a rare earth-iron-boron permanent magnet. 3. The method for producing a rare earth-iron-boron permanent magnet alloy according to claim 1, characterized in that two or more types of magnetic powders having different compositions are concentrically arranged and molded during cold preforming. A method for producing a rare earth-iron-boron permanent magnet. 4. A rare earth-iron-boron permanent magnet alloy according to claim 3, characterized in that two or more kinds of magnetic powders having different degrees of supercooling are concentrically arranged and molded. A method of manufacturing permanent magnets. 5. Rare earth metal - iron - according to claim 1 or 2
A method for manufacturing a boron-based permanent magnet alloy, which is characterized by preforming two or more types of magnetic powders having different compositions or degrees of supercooling by laminating and concentrically arranging them. Production method. 6. In the method for producing a rare earth-iron-boron permanent magnet alloy according to any one of claims 1 to 5, the magnetic powder arranged on the outer periphery of the preform has a grain growth rate. Rare earth metal - iron - characterized by low temperature dependence
A method for producing a boron-based permanent magnet alloy.