JPH06108111A - Production of ferromagnetic powder sintered body - Google Patents

Abstract

PURPOSE:To provide the process for production of the sintered body of ferromagnetic powder which can easily handle powder molded articles, has excellent productivity and is suppressed in the degradation in magnetic force as far as possible. CONSTITUTION:The ferromagnetic powder consisting of particles having magnetic anisotropy is packed into a molding container 2 and a magnetic field is acted on this molding container 2 to orient the powder in the molding container 2 in a magnetic field direction; thereafter, the molding container 2 is subjected to cold isotropic pressurizing, by which the powder in the molding container 2 is compression molded. After the powder molded article is demagnetized, the molded article is sintered and magnetized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ferromagnetic powder sintered body having magnetic anisotropy.

[0002]

2. Description of the Related Art Conventionally, magnetic materials such as permanent magnets have been manufactured by uniaxially compression-molding ferromagnetic powder in a magnetic field by a magnetic field press and sintering the molded powder compact. Since compression molding is performed at the same time as imparting uniaxial magnetic anisotropy, the orientation of the powder is disturbed during molding, and the magnetic force is inevitably reduced.

Therefore, in recent years, as a suitable method for producing a powder-sintered magnetic material, as disclosed in JP-A-63-227701, a ferromagnetic powder made of particles having magnetic anisotropy is molded. To give uniaxial magnetic anisotropy in a magnetic field, and then cold isostatic pressing (referred to as CIP).
Has developed a method for compression-molding powder in a molding container and sintering the resulting powder compact. According to this method
Since uniaxial magnetic anisotropy is imparted and compression molding is separated, and CIP which is less likely to cause disorder in powder orientation is adopted as a molding means, a magnetic material having a relatively good magnetic force can be obtained. .

[0004]

However, since the particles of the ferromagnetic powder are magnetized and arranged in the same polarity at the end faces of the powder compact after CIP molding in the magnetic direction, they repel each other and the orientation of the powder is disturbed. Is likely to occur. This turbulence progresses inside the molded body with the passage of time. Therefore, the magnetic force of the ferromagnetic powder sintered body tends to decrease.

Further, since the powder compacts are magnetized, they are attracted to each other, and the handling is troublesome, and the powder compacts are apt to be damaged or broken on the carrying tray. In particular, CIP molding enables high-density molding at a relatively low pressure as compared with uniaxial compression molding, so that physical bonding (adhesion) between powder particles is weak and the tendency is high. In addition, when mounting on a sintering tray, it is necessary to set a sufficient distance between the molded bodies so that the molded bodies do not stick to each other, which causes a problem of poor productivity.

The present invention has been made in view of the above problems, and is a method for producing a ferromagnetic powder sintered body in which the powder compact is easy to handle, has excellent productivity, and the decrease in magnetic force is suppressed as much as possible. The purpose is to provide.

[0007]

A method for producing a ferromagnetic powder sintered body according to the present invention comprises filling a molding container with a ferromagnetic powder composed of particles having magnetic anisotropy, and applying a magnetic field to the molding container. After orienting the powder in the molding container in the magnetic field direction, CIP the molding container to compression-mold the powder in the molding container, and sinter the molded powder compact to produce a ferromagnetic powder sintered body. In the method, after ferromagnetic powder is CIP-molded, the powder compact is demagnetized, sintered, and then magnetized.

[0008]

[Function] Since the powder compact is demagnetized after CIP molding,
During subsequent transportation and during the sintering process, suction between the molded bodies,
There is no need to consider adsorption, handling is easy, and multiple simultaneous treatments are possible. In addition, since magnetic interference of the powder particles at the magnetic end of the compact is eliminated, disorder of particle orientation does not progress, and a strong ferromagnetic powder sintered body can be obtained.

[0009]

1 to 3 show an example of a powder molding apparatus for carrying out the present invention, which is a ring-shaped rotary table 1
The powder feeding station S1 and the pre-compression station S
2, magnetizing station S3, CIP molding station S
4, demagnetization station S5, discharge / placement station S
Molded containers at each station, with 6 equally spaced
2 is transferred to the next adjacent station by rotating the rotary table 1 at a predetermined angle between the adjacent stations.

On the outer peripheral portion of the rotary table 1, a powder feeding device 3 for filling and feeding the ferromagnetic powder into the molding container 2 placed at the powder feeding station S1 and a preliminary compression station S2 are placed. Powder in the molding container 2
Pre-compressing device 4 for pre-compressing the whole, a magnetizing device 5 for imparting uniaxial magnetic anisotropy to the powder in the pre-compressed molding container 2 placed at the magnetizing station S3, and a uniaxial magnetic anisotropic CIP molding device 6 for CIP-molding the powder to which the property is imparted together with the molding container 2 mounted on the CIP molding station S4, and the powder after CIP molding in the molding container 2 mounted on the demagnetization station S5. The demagnetizing device 7 for demagnetizing the compact and the demagnetized powder compact in the compact container 2 placed at the discharging / placing station S6 are carried out of the rotary table 1 together with the compact container 2. At the same time, an unloading / mounting device (not shown) for mounting the empty molded container 2 on the rotary table 1 at the same station S6 is arranged. As the carry-out / placement device, a robot or a carrier device used for a preliminary compression device 4 described later can be used.

As shown in FIG. 2, the rotary table 1 includes a ring-shaped table top plate 8 and a ring 9 with a gear attached to a lower portion thereof, which is rotated by balls on a support leg 11 provided upright on a frame 10. It is supported freely. The geared ring
The gear portion 9 is meshed with a drive gear that is interlocked with a motor (not shown). The powder supply device 3 includes a hopper 13 containing a ferromagnetic powder, and a powder feeder 15 for measuring the powder amount according to the capacity of the molding container 2 and supplying the powder to the container 14. A certain amount of powder is fed from the hopper 13 through the feeder 16. The molding container 2 is generally composed of a bottomed cylindrical main body and an upper lid for removably closing the upper opening of the main body, and is formed of a high elastic polymer material such as rubber or resin. As the ferromagnetic powder, various types such as ferrite type, Sm-Co type and Nd-Fe-B type can be used.

As shown in FIG. 2, the precompressor 4 includes a uniaxial press 18 for uniaxially compression-molding the powder in the molding container 2 together with the molding container 2, and a molding container on the rotary table 1.
2 is conveyed to the uniaxial press 18 and a conveying device 19 for returning the pre-compressed molded container 2 to the rotary table 1. The uniaxial press 18 is a cylindrical mold 20.
And an upper punch 21 that can be inserted into and removed from the mold 20 by a pressure cylinder and a lower punch 22 that can move in the mold 20. On the other hand, the transfer device 19 is provided with a clamp 24 that holds the molding container 2 openably and closably, the clamp 24 is movable between the rotary table 1 and the uniaxial press 18 by a transfer cylinder 25, and the transfer cylinder 26 is a transfer cylinder.
It is said to be able to move up and down in increments of 25. These devices are frames
It is attached to 27.

The operation of the precompressor 4 in one cycle will be described below. The molding container 2 transferred to the precompression station S2 of the rotary table 1 is clamped by the clamp 24 of the transfer device 19.
It is gripped by and is transferred to the uniaxial press 18 side by the retreat of the transfer cylinder 25, is placed on the lower punch 22 in the die 20, and is sandwiched and pressed by the upper punch 21 and the lower punch 22. The pre-compression-molded molding container 2 is again gripped by the clamp 24 at the rising position of the lower punch 22, and the transfer cylinder 25
Is returned to the rotary table 1 by the forward movement of the clamp 24
It is placed on the turntable 1 by opening.

The mechanical structures of the magnetizing device 5 and the demagnetizing device 7 are substantially the same, and basically the mold 20 of the precompressing device 4 is replaced with an electromagnetic coil. However, the magnetic field directions of the electromagnetic coils of both devices 5 and 7 are opposite. The electromagnetic coil is energized while the molding container is lightly gripped by the upper punch and the lower punch. The power supplied to the electromagnetic coil may be pulsed.

As shown in FIG. 3, the CIP molding device 6 includes a CIP press 29 for CIP molding the powder in the molding container 2 together with the container 2, and a molding container on the rotary table 1.
Conveying device for conveying 2 to the CIP press 29 and returning the molding container 2 after CIP molding onto the rotary table 1.
It is composed of 30 and. The CIP press 29 includes a pressure vessel 31 supported by a fixed frame 36, and a lower lid which can be inserted into and removed from an opening at a lower end of the pressure vessel 31 by a lifting cylinder 32.
33 and a press frame 34 for carrying an axial force of the pressure vessel 31 to which the lower lid 33 is attached. The press frame 34 is moved between the pressure vessel 31 side and the fixed frame 36 side by a pair of transfer cylinders 35, and is inserted into the pressure vessel 31 on which the lower lid 33 is attached on the pressure vessel 31 side. The transfer device 30 is horizontally mounted on the rotary table 1 by a support frame 38, and has a clamp 39 for holding the molding container 2 on the rotary table 1 and placing it on the lower lid 33 of the CIP press 29. The clamp 39 is movable in a lift box 41 that is lifted by a lift cylinder 40 between a rotary table 1 side and a pressure container 31 side by a transfer cylinder (not shown).

The operation of the CIP molding device 6 in one cycle will be described below. The molding container 2 transferred to the CIP molding station S4 of the rotary table 1 is gripped by the clamp 39 of the transfer device 30, and is transferred to the CIP press 29 side by the transfer cylinder in the elevating box 41, and the lower lid is opened by opening the clamp 39. It is placed on the upper surface of 33. After that, the lower lid 33 is raised to house the molding container 2 in the pressure container 31, the press frame 34 is inserted, and then the pressure medium is injected into the pressure container 31.
As a result, the molding container 2 is CIP-molded via the elastic partition wall for pressure in the pressure container 31. After molding, the pressure is released, the press frame 34 is moved to the outside of the pressure vessel 31, and then the lower lid 33
, Hold the molded container 2 on the lower lid 33 with the clamp 24, and use the transfer cylinder to rotate the clamp 39 to the rotary table.
CI by moving to the 1 side and opening the clamp 24
The molding container 2 after P molding is placed on the rotary table 1.

Next, the method of the present invention will be described together with the operation of the powder molding apparatus. Molding container 2 (container body) that was placed on the carry-out / placement station S6 on the turntable 1
Is transferred to the powder feeding station S1 by rotating the rotary table 1 at an angle between adjacent stations, and the powder feeding step is carried out there. That is, the powder supplying device 3 fills the ferromagnetic powder, and the container body is provided with the upper lid by an appropriate means. By the rotation of the rotary table 1, each of the molding containers 2 after the respective processes in the powder feeding station S1, the pre-compression station S2, the magnetizing station S3, and the CIP molding station S4 on the rotary table 1 is moved to the next adjacent station. Then, in each station, the steps of precompression, imparting uniaxial magnetic anisotropy, CIP molding, and demagnetization are performed. In addition, the molded container 2 that was in the demagnetization station S5 is the unloading / loading station S.
6, the container is carried out by the molding container unloading / mounting device, and an empty molding container (container body) is placed on the same station. The rotation timing of the rotary table 1 is when all the processing at each station is completed.
Of the processes, the CIP molding process takes the longest time,
In effect, the rotary table 1 rotates the angle between adjacent stations by one pitch due to the end of the CIP molding process.

In the molding container 2 carried out by the molding container carrying-out / mounting device, the powder compact is taken out from the inside thereof,
A plurality of them are stored in a carrying tray and sent to the sintering process. Then, it is transferred to a sintering tray and sintered, and if necessary, subjected to heat treatment or the like for improving magnetic force, and after machining,
It is magnetized and made into a product. According to the powder molding device,
It is extremely easy to convey the molding container between the steps, and the productivity of the powder compact can be improved.

In the above embodiment, the discharge station for the molded container on the rotary table and the station for mounting the empty container are set at the same position, but they may be arranged at different positions so that the stations are equidistant. Good. Further, although a rotary table is provided in the embodiment as a means for transferring the molding container,
It is possible to manufacture a powder sintered magnetic material in the same manner as described above by providing a linear conveying means such as a conveyor, providing each station at equal intervals along the line, and feeding the line at a pitch between adjacent stations. . Further, for the process having the longest cycle time, that is, the CIP molding process, it is possible to shorten the entire production cycle by providing a plurality of CIP molding devices.

[0020]

As described above, according to the method for manufacturing a ferromagnetic powder sintered body of the present invention, the powder molded body is once demagnetized after CIP molding. It is possible to prevent the disorder of the orientation of the powder particles of the powder compact, and to prevent damage and cracking due to suction / adsorption, and thus to improve the magnetic force and productivity of the ferromagnetic powder sintered body. Can be planned.

[Brief description of drawings]

FIG. 1 is a plan layout view of a powder molding apparatus for carrying out the present invention.

FIG. 2 is a view on arrow A in FIG.

FIG. 3 is a view on arrow B of FIG.

[Explanation of symbols]

 2 molding container 3 powder supply device 5 magnetizing device 6 CIP molding device 7 demagnetizing device

Claims (1)

[Claims] 1. A molding container is filled with a ferromagnetic powder composed of particles having magnetic anisotropy, and a magnetic field is applied to the molding container to orient the powder in the molding container in the magnetic field direction. In a method of manufacturing a ferromagnetic powder sintered body, in which the powder in a molding container is compression-molded by cold isostatic pressing and the molded powder compact is sintered, the ferromagnetic powder is cold isostatically pressed. A method for producing a ferromagnetic powder sintered body, comprising depressurizing the powder molded body after pressure molding, sintering and magnetizing.