JPH08181028A - Method and apparatus for processing rare earth permanent magnet - Google Patents

Abstract

PURPOSE: To improve the processing capacity while preventing the decrease in the magnetic characteristics by processing the molded form of a rare earth permanent magnet while being dipped in mineral oil, synthetic oil or vegetable oil. CONSTITUTION: Before processing, a movable table 6 is lifted by a driving shaft 8 from the surface of processing solution (mineral oil, synthetic coil or vegetable oil) 2, a molded form 3 is fixed to a spacer 3 at this position, and assembled with the table 6. Then, after a working blade 4 is arrived at a predetermined rotation, the table 6 is pressed down by the shaft 8, and hence the form 3 is brought into contact with the blade 4 and cut. Cuttings generated by the cutting are transferred together with the solution 2 by a circulating pump 10 via a tube 1 to a cutting recovering unit 12. The solution 2 in which the cuttings are removed is again returned to a processing tank 1. When the cutting is completed, the table 6 is again lifted above the surface of the solution 2, and the form 3 in which the processing is finished is removed. Thus, the processing capacity can be improved while preventing the decrease in magnetic characteristics due to the reaction with oxygen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for processing a compact obtained by pressure-molding a fine powder for a rare earth permanent magnet in a magnetic field.

[0002]

2. Description of the Related Art A rare earth permanent magnet obtained by sintering a compact obtained by compacting a fine powder for a rare earth permanent magnet in a magnetic field is generally ground by a diamond or CBN grindstone. The reason why grinding with a small processing capacity is performed is that the rare earth magnet after sintering is a hard and brittle hard-to-process material and it is difficult to apply processes other than grinding. As one of the methods to improve the processing ability, there is so-called green processing in which a green body before sintering is processed into a desired size and shape and then sintered.However, a green body of a rare earth permanent magnet reacts with oxygen in the atmosphere. In that case, the magnetic properties are deteriorated. Further, the chips generated during processing similarly react with oxygen, and in the worst case, heat generation and ignition occur. As a countermeasure, JP-A-53-899
As disclosed in the publication, a method of performing processing in an inert gas such as nitrogen gas is disclosed.

[0003]

However, the above-described method of processing the molded body in an atmosphere of an inert gas such as nitrogen gas while preventing oxidation of the molded body has the following problems. First of all, in order to maintain an inert gas atmosphere, the molding target, the holding mechanism for the molding, and the processing tool are all housed in a closed container, which makes the device large and complicated.
Further, it is necessary to carry out a gas replacement work for maintaining an inert gas atmosphere every time the molded body is carried into the closed container and carried out after the processing. In addition, since the machining is a dry machining that does not use a machining fluid, the clogging of the tool by the cutting chips occurs and the machining capability is reduced. Further, since it is difficult to discharge the chips, it is necessary to frequently interrupt the processing and perform the gas replacement work described above. It is an object of the present invention to provide a method for processing a rare earth permanent magnet capable of improving the processing capability while preventing the deterioration of magnetic characteristics due to the reaction with oxygen, and a processing apparatus used for the method.

[0004]

The present invention relates to a method of processing a molded product obtained by pressure molding a fine powder for a rare earth permanent magnet into a desired size and shape in a magnetic field, wherein the molded product is a mineral oil, a synthetic oil or a vegetable oil. It is characterized in that it is processed in a state of being immersed in. Further, in an apparatus for processing the molded body into a desired size and shape, a rotatable processing blade having a main shaft is provided in a processing tank so as to be submerged in a processing fluid of mineral oil, synthetic oil or vegetable oil, and movable. A moving table for mounting a molded body having a slide shaft and a drive shaft was provided so as to face the machining blade, and a circulation pump and a chip collecting device were connected between the machining tank bottom portion and the machining tank upper surface vicinity through piping. It is characterized by

[0005]

The advantage of the method of processing a molded product in this liquid is that the atmosphere containing oxygen is completely cut off to prevent the deterioration of the magnetic properties due to the reaction with oxygen, while maintaining the inertness described above. Compared to an apparatus that processes in gas, the apparatus can be remarkably simplified, and gas replacement work with an inert gas that is carried out each time the molded body is loaded and unloaded after processing is not required. It is possible to continuously discharge chips by circulating the working fluid, and to significantly reduce the clogging of the working blade and improve the working capacity.

[0006]

[Embodiment 1] An embodiment of the present invention will be described with reference to FIG. First, the method of forming the molded body in this example is as follows. Weight percentage of Nd 27.5%, Pr2.
5%, Dy 1.0%, B 1.0%, Nb 0.6%, Co
Nd—Fe—B rare earth permanent magnet coarse powder having a composition of 4.0%, Al 0.2%, Ga 0.1% balance Fe was finely pulverized in a nitrogen stream, and a fractional distillation point was obtained at the fine powder discharge port of the pulverizer. Is 200
Install a container filled with mineral oil [made by Idemitsu Kosan, trade name MC Oil P02] having a kinematic viscosity of 2.0 cSt at room temperature up to 300 ° C. It was collected in and used as a raw material mixture. The raw material fine powder weight ratio of this raw material mixture was 70%. The average particle size of the raw material fine powder was 4.0 μm. A magnetic field of 8 kOe was applied to and held in the mold cavity, the raw material mixture was pressure-filled into the cavity at a pressure of 10 kgf / cm 2, and then compacted at a molding pressure of 1 ton / cm 2 to obtain a compact 3.

The working tank 1 accommodates a moving table 6 on which the molded body 3 is mounted, a working blade 4 and one end of a spindle 5. The moving table 6 is structured so as to be held by a slide shaft 7 fixed to the working tank 1 and to be linearly movable in the rotation direction of the working blade 4 by a drive shaft 8. At the bottom of the processing tank 1, a circulating pump 10 is used to collect a processing liquid 2 containing cutting chips in a chip collecting device 12
A pipe 11 is provided for leading to. Further, a spacer 9 for adjusting the positional relationship between the processing blade 4 and the molded body 3 is provided between the molded body 3 and the moving table 6. The processing tank 1 was filled with a mineral oil [made by Idemitsu Kosan, trade name MC Oil P02] as the processing liquid 2 until all the processing blades 4 were submerged in the processing liquid 2. Since the cutting process was performed in this example, a metal saw having a diameter of 200 mm and a blade thickness of 0.8 mm having a notch in the outer peripheral portion was adopted as the processing blade 4. The rotation speed of the main shaft 5 is 200 to 500 rp
The peripheral speed of the processing blade is 125-315 because it was adjusted in the range of m.
m / min.

The machining operation with the above configuration is as follows. Prior to processing, the moving table 6 was pulled up above the surface of the processing liquid 2 by the drive shaft 8. At this position, the molded body 3 was fixed to the spacer 9, and this was mounted on the moving table 6. After the machining blade 4 reaches a predetermined rotation, the movable table 6 is pushed down by the drive shaft 8 so that the compact 3 comes into contact with the machining blade 4 and is cut. The spacer 9 is provided with a relief groove so that the machining blade 4 and the spacer 9 do not come into contact with each other. The chips generated by the cutting settle at the bottom of the processing tank 1, but are transferred together with the processing liquid 2 to the chip collecting device 12 by the circulation pump 10 via the pipe 11. The machining fluid 2 from which the chips have been removed is returned to the machining tank 1 again. In this embodiment, in order to prevent chips from accumulating on the compact 3, the compact 3 is considered to move in the vertical direction. When the cutting was completed, the moving table 6 was pulled up again onto the surface of the working liquid 2, and the molded body 3 after processing was removed.

Similar cutting of a sintered body is usually performed using a diamond grindstone, and in this case, the processing speed is about 2 to 5 mm / min, but in this embodiment, 10 to 30 mm / min. Processing was possible.

Since the solvent of mineral oil, synthetic oil, or vegetable oil remains in the molded body after processing, if the normal sintering is performed as it is, the remaining solvent evaporates during heating and the inside of the sintering furnace And is partially decomposed and remains in the sintered body. For this reason, the residual carbon amount of the sintered body increases, the sintered body density decreases, and the residual magnetic flux density and the maximum energy product decrease. In order to prevent this, the molded body after processing must be subjected to desolvation treatment and then sintered. The processed compact is subjected to demineralized oil treatment at 200 ° C. for 2 hours under a pressure of 5 × 10 −2 Torr, and then heated to 1070 ° C. at the same pressure at a heating rate of 15 ° C./min, It hold | maintained for 3 hours and sintered. The sintered body was subjected to heat treatment at 900 ° C. × 1 hour and 620 ° C. × 1 hour once in an Ar atmosphere.

The magnetic properties, oxygen content, carbon content and density of this sample were measured.
3.1 kG, coercive force 13.9 kOe, maximum energy product 41.0 MGOe, oxygen content 1800 ppm, carbon content 0.05% by weight, density 7.57 g / cc, and no deterioration in magnetic properties was observed.

[0012]

Example 2 Nd 27.5% and Pr2.5 by weight percentage
%, Dy 1.0%, B 1.0%, Nb 1.0%, Co
Nd- having a composition of 2.0% and Al 0.2% balance Fe
The Fe-B rare earth permanent magnet coarse powder was finely pulverized in a nitrogen stream to obtain fine powder having an average particle size of 3.9 μm. This fine powder was put into a mold cavity and pressure-molded under the conditions of an orientation magnetic field strength of 10 kOe and a molding pressure of 1.0 ton / cm @ 2 to obtain a molded body. This molded body was immersed in mineral oil [trade name: MC oil P02 manufactured by Idemitsu Kosan], and then processed under the same apparatus and conditions as in Example 1. The molded body after processing is subjected to demineralizing oil treatment in which the temperature is raised from room temperature to 500 ° C at a heating rate of 5 ° C per minute under a pressure of 5 × 10 -2 Torr, and then the same pressure is applied up to 1100 ° C. The temperature is raised at a heating rate of 30 ° C./min,
It was held for 2 hours for sintering. Sintered body is 90 in Ar atmosphere
Heat treatment was performed once at 0 ° C. for 1 hour and at 600 ° C. for 1 hour each.

The magnetic characteristics, oxygen content, carbon content and density of this sample were measured.
The magnetic property was 2.2 kG, the coercive force was 14.5 kOe, the maximum energy product was 34.7 MGOe, the oxygen amount was 4750 ppm, the carbon amount was 0.06 wt%, and the density was 7.55 g / cc.

The types of the mineral oil and the synthetic oil used as the solvent of the present invention are not specified, but when the kinematic viscosity at room temperature exceeds 10 cSt, the binding force between the fine powders is strengthened due to the increase in viscosity, and the magnetic field is increased. It adversely affects the orientation of the fine powder during medium-wet molding. Therefore, the kinematic viscosity of the mineral oil and the synthetic oil at room temperature is preferably 10 cSt or less. If the fractional distillation point of mineral oil or synthetic oil exceeds 400 ° C, it becomes difficult to remove the solvent during sintering, and the amount of residual carbon in the sintered body increases, resulting in deterioration of magnetic properties. Therefore, the fractional distillation points of mineral oils and synthetic oils must be 400 ° C or lower. Vegetable oil refers to oil extracted from plants, and the type thereof is not particularly limited. For example, soybean oil, rapeseed oil, corn oil,
Examples include safflower oil and sunflower oil.

The desolvation treatment is carried out by keeping the molded product in the temperature range of 100 to 500 ° C. for 30 minutes or more under a reduced pressure of 0.1 Torr or less. The holding temperature is 100 to 50
The temperature does not have to be one point as long as it is in the range of 0 ° C., and may be two or more points. Desolvation can also be performed by setting the rate of temperature increase from room temperature to 500 ° C. to 10 ° C./min or less under a reduced pressure of 0.1 Torr or less.

The sintered body is subjected to heat treatment under the condition corresponding to its composition, but it may be subjected to additional processing after the heat treatment as required to obtain a product with high dimensional accuracy. Further, additional processing may be performed after the heat treatment of the sintered body.

[0017]

As described above, according to the present invention, there is provided a method for processing a rare earth permanent magnet capable of improving the processing ability while preventing the deterioration of the magnetic characteristics due to the reaction with oxygen, and the processing apparatus used for the method. It becomes possible to provide.

[Brief description of drawings]

FIG. 1 is an overall view of a processing apparatus used in an embodiment of the present invention

[Explanation of symbols]

 1 Processing Tank 2 Processing Liquid 3 Formed Body 4 Processing Blade 5 Spindle 6 Moving Table 7 Slide Shaft 8 Drive Shaft 9 Spacer 10 Circulation Pump 11 Piping 12 Chip Recovery Device

Claims (2)

[Claims] 1. Fine powder for rare earth permanent magnet [R-Co5 system,
R2-Co17 system or R-Fe-B system. Here, R is one or more of rare earth elements containing Y] is processed into a desired size and shape in a magnetic field by pressure molding, and the molded body is converted into mineral oil, synthetic oil or vegetable oil. A method for processing a rare earth permanent magnet, which is characterized in that it is processed in an immersed state. 2. A rotatable processing blade having a main shaft is provided so as to be submerged in a processing liquid of mineral oil, synthetic oil or vegetable oil, and a molded body having a movable slide shaft and a drive shaft is mounted in the processing tank. 2. The processing according to claim 1, wherein the movable table is provided so as to face the processing blade, and the circulation pump and the chip collecting device are communicated with each other through the pipe between the processing tank bottom portion and the processing tank upper surface vicinity. Rare earth permanent magnet processing equipment used for.