JP2691444B2 - Extrusion molding method of magnetic material having hollow portion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECT OF THE INVENTION [Industrial field of use] The present invention relates to a method for producing a sintered product of a magnetic material by extrusion molding, and in particular, an extrusion molding method which is excellent in the removability and shape retention of a thin product having a hollow portion inside. Is provided.

[Conventional technology]

In the conventional method, the raw material pellets have an average particle size of 0.5μ.
ratio of Ni-Zn ferrite powder with m and iron with an average particle size of 10 μm
50%, 50% cobalt weight ratio alloy powder and average particle size 12 μm
The thermoplastic binder of the composition shown in Table 1 is mixed with the powder of the samarium-cobalt-based magnet, and the mixture is kneaded at a predetermined temperature for about 20 minutes using a kneading machine, and this is ground to be a raw material.

The raw material was extruded from the raw material by the extruder 1 shown in FIG. In FIG. 7, 1 is an extruder, 2 is a belt, and 4
Is a molded body, 5 is a take-up device, and 6 is a hopper. The raw material is put into the hopper 6, and the molded body 4 is molded and extruded by the extruder. The molded body 4 is conveyed and taken out by the belt 2 rotated by the rolls. In the conventional method, the molded body was molded by such a method, but according to this conventional method, it was limited to a prism without a hollow portion, a cylinder, an elliptic cylinder and the like. Further, in the case of a prismatic or elliptic cylindrical molded body, the prismatic, cylindrical, or elliptical cylindrical wall thickness was limited to a thick molded body of 7 to 10 mm. Recently, a thin molded product having a thickness of 2 to 3 mm has been required, and it has been difficult to manufacture a thin molded product by the conventional method.

[Problems to be solved by the invention]

Generally, in the process of manufacturing a sintered product of a magnetic material by a powder metallurgy method, a method of obtaining a green compact before sintering by compression molding is widely used. Since this is usually formed by pressing magnetic powder from above and below with a punch, the shape is limited to a relatively simple shape. Especially, thin-walled products with hollow parts inside are defective if they deform significantly. Therefore, molding could not be performed.

On the other hand, in the field of ceramic products centering on so-called engineering ceramics, etc.
It is beginning to be industrially started to efficiently produce even a comparatively complicated shaped article by adding an organic binder of up to 20% by weight, mixing and kneading, and then extrusion molding, which is attracting attention. Furthermore, this technology is a recent mixing / kneading technology,
With the development of extrusion molding technology, application to metal products has been attempted. However, the problem here is that the material used for such molding is filled with powder at a high concentration,
When it is extruded in a horizontal direction with a high density, there is a drawback that a thin-walled one having a hollow portion inside tends to be deformed by its own weight immediately after being extruded from a die. In order to solve this, it is conceivable to make the extruder vertical, or use a crosshead to make the extrusion direction vertical, but in such a method, the process after extrusion is performed with the die and the floor surface. However, the production speed and workability are limited, and it is not a fundamental solution.

The present invention relates to the production of a rectangular tube, a cylinder, an elliptic tube having a complicated shape, that is, a thin-walled molded body having a hollow portion inside, and a molded body which is difficult to manufacture by the conventional technique due to the above-mentioned problems. It is intended to be manufactured without deformation.

B. Structure of the Invention [Means for Solving the Problems] The present invention is a mixture of magnetic powder and a binder containing a polymer compound as a main component In the method for molding a material, at least one surface of an extruded product extruded from an extruder and a belt that takes the extruded product constitute a magnetic circuit, and the belt has a structure for adsorbing the extruded product. Is a method of extrusion molding a magnetic material having a hollow portion. That is, the molded body immediately after being extruded by the extruder is in a state of not sufficiently cooled and solidified,
A thin-walled product having a hollow portion inside will be deformed by its own weight. A method for attracting a molded body from above and below by utilizing a magnetic force as a method for pulling it without causing deformation, and taking it while maintaining a good shape, provides a method capable of improving the yield of the molded body. It is characterized by being

Next, embodiments of the present invention will be described in detail with reference to the drawings.

[Action]

In the extrusion molding method, the molded body of the ferromagnetic material extruded from the extruder is deformed by the resistance of the friction force of the take-up plate when extruded as it is on the take-up device,
Since the molded product is held and conveyed by the belt 2 as shown in FIG. 1 because it is damaged, it is deformed by the weight of the molded product and the friction between the belt and the molded product. In particular, a thin prismatic, cylindrical, or elliptic cylindrical molded body having a hollow inside is desired to have a flat surface, and if parallelism is not obtained, the yield is poor and further a sag is formed in the hollow portion.

Therefore, in order to prevent this, a plate-like magnet 3 is installed inside the belt as shown in FIG. 1, and the molded body of the ferromagnetic material is conveyed while being attracted by the magnet installed on the back surface of the belt. Therefore, there is no deformation. The cylindrical or elliptical molded body functions to prevent deformation by molding the belt according to the shape of the molded body as shown in FIG. 5 and using the belt itself as a magnet.

〔Example〕

 Embodiment 1 FIG. 1 is a block diagram showing the first embodiment of the present invention.

FIG. 2 is a transverse sectional view for explaining FIG. The second
The arrow in the width of the belt 3 in the figure indicates the magnetic field line.

As shown in Table 1, the raw material pellets were Ni-Zn ferrite calcined powder with an average particle size of 0.5 μm, 91% by weight of magnetic powder and 20% by weight of vinyl acetate in ethylene-
5% by weight of vinyl acetate copolymer, 3% by weight of paraffin wax having a melting point of 60 ° C., 1% by weight of dioctyl phthalate of reagent grade and 1% by weight of thermoplastic binder were mixed, and a pressure kneader was used. After kneading at 130 ° C. for 20 minutes, the raw material for pellets was obtained by pulverizing. This raw material is put into a hopper, and an extruder having a hollow inside has a size of 15 mm in length, 30 mm in width, and 3 mm in wall thickness by an extruder (screw diameter of 30 mm, L / D: 22) 1 shown in FIG. Extruded product. The barrel temperature of the extruder 1 was set to a constant temperature between 120 and 140 ° C. by a band heater.

FIG. 2 shows the take-up device 5 and the molded body 4 shown in FIG.
FIG. The cross-sectional shape of the molded body 4 has a rectangular shape with the above dimensions of 15 mm in width, 30 mm in width and 3 mm in wall thickness, and has a hollow portion inside, and is extruded by the extruder 1 shown in FIG. The body 4 is guided and taken up between the upper and lower belts 2 of the take-up device 5. At this time, the distance between the upper and lower belts 2 is 15 mm, which is the same as that of the molded body 4.
The take-up speed is set at about 80 cm / min so as to be synchronized with the extrusion speed of the extruder 1.

Immediately after being kneaded and extruded by the extruder 1, the molded body 4 is in a state where it is not sufficiently cooled and solidified, and the shape retention is not sufficient, and in particular, a hollow portion is present inside the product as shown in FIG. The upper part of the molded body 4 that has been made is in a state where it is likely to be deformed by its own weight. Here, there is a gap of 1 to 3 mm between the belt 3 and the magnet 3 inside the belt 2, and the flat plate-shaped magnet 3 held by the holder is installed to make it from the ferromagnetic powder. Since the molded body 4 is attracted from the vertical direction by this, the molded body 4 is pulled and advanced without being deformed by its own weight. At this time, the molded body 4 is deprived of heat by coming into contact with the belt 2, and is cooled and solidified while maintaining a good shape, so that it does not deform even if it is separated from the take-up device 5. Further, the belt 2 that has been taken off and separated from the molded body 4 has the heat carried by the molded body in the process of cooling the molded body 4, and in this state, the molded body 4 will be sufficiently removed in the next take-up. There is a possibility that deformation will occur when the belt 2 is separated from the belt 2 without being solidified by cooling. As a method of solving this, by blowing the compressed air A onto the belt 2 separated from the molded body 4,
The belt 2 is cooled, and when the next take-up is carried out, the molded body 4 is again returned.
It becomes possible to take away the heat. Since the molded body 4 immediately after being extruded has a temperature of 120 to 140 ° C. due to overheating by a heater, the material of the belt 2 to be used needs to have excellent heat resistance. Use a metal with good thermal conductivity such as silicon rubber or copper.

The molded body 4 produced by the above method is cut into a length of 50 mm, and a degreasing furnace is used to heat it in the atmosphere with a temperature gradient of 20 ° C / Hr in the atmosphere, hold it at 500 ° C for 1 hour, and then cool it in the furnace. Was degreased by. After that, this was sintered in the atmosphere at 1200 ° C. for 3 hours. As a result, the size is 12.9 mm in height and 25.9 in width.
A magnetic material sintered body having a thickness of 2.6 mm and a density of 5.19 was obtained.
As a result, a molded body without deformation was obtained, and the initial purpose could be achieved.

Embodiment 2 FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is a sectional view for explaining FIG. The arrow in the belt 21 in FIG. 2 indicates the magnetic force line.

As a raw material powder, an alloy having a composition of iron weight ratio of 50% -cobalt weight ratio of 50% was melt-produced by high frequency heating in an argon gas atmosphere, and powder produced to have an average particle size of 10 μm by a water atomizing method was used. As shown in Fig. 4, an ethylene-vinyl acetate copolymer having a magnetic powder weight ratio of 94% and a vinyl acetate content of 20% by weight was blended at a weight ratio of 4%. The same conditions as in Example 1 with a binder composition having a paraffin wax weight ratio of 1% at 1 ° C and a reagent grade dioctyl phthalate weight ratio of 1%,
That is, 50% by weight of iron and 50% by weight of cobalt have an average particle size of 10μ.
The powder raw material of m and the binder composition were mixed, kneaded in a pressure kneader at 130 ° C. for 20 minutes, and then pulverized to obtain a raw material for pellets. This raw material was put into a hopper, and the extruder shown in FIG. 1 (screw diameter 30 mm, L /
D: 22) has a hollow inside with a length of 15 mm and width of 30 m
A product with a shape of m and a thickness of 3 mm was extruded. The barrel temperature was set to a constant temperature between 120 and 140 ° C as in Example 1,
Here, in order to maintain the shape of the molded body 4, a magnetized belt main body 21 of the take-up machine was used instead of the magnet 3 installed in the first embodiment. A rubber magnet having silicon rubber as a base material was used as the material of the belt, and the cooling and solidification of the molded body 41 was performed in the same manner as in Example 1.

The molded body 41 produced by the above method is cut into a length of 50 mm, heated in an argon gas atmosphere with a temperature gradient of 10 ° C./Hr using a degreasing furnace, kept at 600 ° C. for 1 hour, and then cooled. Degreasing was performed by this. Thereafter, this was sintered in a hydrogen atmosphere at 1200 ° C. for 2 hours. As a result, a magnetic material sintered body having dimensions of 12.8 mm in length, 25.5 mm in width, 2.6 mm in wall thickness, and 7.90 in density was obtained.

Example 3 FIG. 5 is a cross-sectional view of the take-up machine and the molded body, and the arrows in the belt 211 indicate the lines of magnetic force. An ingot having a composition of samarium weight ratio 25.2% -cobalt weight ratio 49.2% -copper weight ratio 9.2% -iron weight ratio 15.0% -zirconium weight ratio 1.4% was melted and manufactured, and solution-treated for 5 hours at 1180 ° C in an argon gas atmosphere. After that, aging treatment was performed at 800 ° C. for 2 hours. Further, a powder was crushed to a mean particle size of 12 μm with a jaw crusher, a disc mill and a ball mill.
Using this as a raw material powder, as shown in Table 1,
5% under the same conditions as in Example 1 with a binder composition of 94% by weight of magnetic powder, 3% by weight of ethylene-vinyl acetate copolymer, 2% by weight of paraffin wax and 1% by weight of dioctyl phthalate. The shape of the product shown in Fig. 3, that is, the elliptical product was molded with a width of 40 mm, a length of 15 mm and a wall thickness of 3 mm. (Of course, it is possible to form a cylindrical product by the same method.) In FIG. 5, 211a is the N pole of the rubber magnet, and 211b
Is an S pole, and 411a is in contact with the S pole, so it is an N pole. A rubber magnet whose base material is silicon rubber is used for the belt 211, and the contact surface of the belt 211 with the molded body 411 is the molded body 41.
It was processed into the same shape as 1. The cooling and solidification of the molded body 411 was performed in the same manner as in Example 1. Cut the molded body 411 produced by the above method to a length of 50 mm,
Degreasing was performed by using a degreasing furnace, heating at a temperature gradient of 10 ° C./Hr under an argon gas stream, holding at 500 ° C. for 1 hour, and then cooling the furnace. Then, this is put under vacuum at 1200 ℃.
Sintered for 5 hours and aged at 800 ° C for 2 hours.
As a result, a sintered body of Sm ₂ Co ₁₇ magnetic material having dimensions of 12.7 mm in length, 25.5 mm in width, 2.5 mm in wall thickness, and 8.40 in density was obtained.

Comparative Example Pellets for extrusion molding were prepared under the same conditions as in Example 1, and extrusion molding was performed without installing the magnet 3 in the take-up device 5.

FIG. 6 shows the amount of deformation of the molded product by the conventional extrusion molding method, and the strain rate at that time is shown by b / from b in FIG.
sought as a. As a result, the distortion rate of the molded body 4 when the magnet 3 was installed and taken back was 0 to 0.026, whereas the distortion rate of the molded body 4 when the magnet 3 was taken out and installed. Was 0.2 to 0.3.

C. EFFECTS OF THE INVENTION [Advantages of the Invention] As described in detail above, according to the extrusion molding method of the magnetic powder of the present invention, in the production of a thin-walled molded article having a hollow portion inside, a good molded article without deformation is obtained. Since the magnetic material sintered product having the above-mentioned shape can be efficiently produced, it is industrially very useful.

[Brief description of the drawings]

FIG. 1 is a configuration front view showing a first embodiment of the present invention. FIG. 2 is a cross-sectional view for cutting the inside of the belt for explaining FIG. FIG. 3 is a front view of the configuration showing the second embodiment. FIG. 4 is a cross-sectional view for cutting the inside of the belt for explaining FIG. FIG. 5 is a cross-sectional view for cutting the inside of the belt showing the third embodiment. FIG. 6 is a cross-sectional view showing the amount of deformation of a molded body by the conventional extrusion molding method. FIG. 7 is a configuration front view showing a conventional extrusion molding machine. 1 ... Extruder, 2,21,211 ... Belt, 3 ... Magnet,
4,41,411 …… Molded body, 5 …… Collection device, 21a, 211a, 3a, 4
a, 41a, 411a: N pole, 21b, 211b, 3b: S pole, A: Direction of blowing compressed air for cooling the belt, a: Width of molded body, b: Deformation amount of molded body.

Claims (1)

(57) [Claims] 1. A method for molding a magnetic material having a hollow portion by using an extrusion molding machine for a mixture obtained by mixing, kneading and pelletizing magnetic powder and a binder containing a polymer compound as a main component, the method being an extrusion molding machine. A magnetic material having a hollow portion, characterized in that at least one surface of the extruded product extruded further and a belt for taking the extruded product constitute a magnetic circuit, and the belt has a structure for adsorbing the extruded product. Extrusion method.