KR20090099310A - Extrusion method for fabricating micro scale article with nano scale powder and shaped article made therefrom, powder compaction device and extrusion eaquipment applied therof - Google Patents

Abstract

An extrusion method for fabricating a micro scale product using nano scale powder and a product manufactured by the method, and a powder compaction device and an extrusion device used for the method are provided to distribute the extrusion load uniformly over a material by forming powder compact and then performing extrusion using the powder compact. An extrusion method for fabricating a micro scale product using nano scale powder comprises the steps of manufacturing powder compact by compaction before injecting nano powder in an extruding device, injecting the powder compact in the extruding device to extrude a product, and sintering the product. A nano powder compacting apparatus for manufacturing a micro scale product comprises a powder compacting mold(110) having an inlet to put in nano powder, a bottom punch(120) installed beneath the powder compacting mold, a top punch(130) installed on the powder compacting mold opposite the bottom punch, and a RAM(140) which is installed on the top punch and delivers pressure to the top punch in order to make the nano powder into powder compact.

Description

Extrusion method for fabricating micro scale article with nano scale powder and shaped article made therefrom, powder compaction device and extrusion eaquipment applied therof}

The present invention relates to an extrusion process, and more particularly, by using a nano-powder of a polymer, plastic or metal, but by lowering the extrusion load by uniformly transferring the extrusion load to the entire material to be extruded, the deformation of the material is made smoothly The present invention relates to an extrusion method for producing a micro-part for preventing cracks on the surface of an extruded molded body, a molded product produced therefrom, and an extrusion die applied thereto.

Recently, the production of micro parts has been increasing, and since the micro parts are applied in various forms to medical, sensors, and electronic devices, the utilization of nano powder is increasing.

On the other hand, in general, extrusion is to put a large plastic material into a container, pressurize it, and pass it through a hole in the die to make a long product having a cross-sectional area of various shapes such as a cross section, a pipe, a wire, etc. Extrusion can be obtained by one extrusion that is difficult to hot roll in large size, and the shape having a complicated cross section can be processed relatively easily.

Therefore, extrusion is being applied to the manufacture of micro-parts, and powder extrusion, in particular, has recently been attracting attention as an advanced material manufacturing method, and is a technology having the following characteristics.

First, it is advantageous in molding an material which is difficult or impossible to manufacture by casting and annealing, by extrusion.

In addition, there is a characteristic that can improve the performance by miniaturization of the specific texture of the powder process, minimizing segregation, and has a feature of obtaining a forged structure by sintering and other heat treatment.

In addition, powder extrusion generally has a lower extrusion pressure than casting materials and has a wide range of extrusion temperatures and extrusion speeds.

However, the extrusion of nanopowders using the conventional powder extrusion method having such characteristics had the following problems.

First, when the conventional extrusion method is to extrude the nano-powder itself, there is a problem that the pressure is not transmitted well to the bottom of the nano-powder injected into the extrusion apparatus, and to solve this, the extrusion load must be increased.

In increasing the extrusion load in this manner, the punch may be broken in severe cases.

In addition, the size of the extrusion device is increased in order to increase the acting extrusion force has a disadvantage that it is difficult to miniaturize the equipment.

In addition, when the extrusion pressure is not transmitted smoothly, cracks are generated on the surface of the molded body of the extruded micro-scale.

Therefore, the development of an extrusion method using nano-powders that can solve these problems is urgently required.

The present invention is to solve the above-mentioned problems, by improving the extrusion method using nano-powder so that the extrusion load can be evenly transmitted to the whole material to be extruded to lower the load required for extrusion, thereby miniaturizing the extrusion apparatus The purpose is to make it possible.

In addition, the present invention has an object to provide a molded article that does not generate cracks on the surface by the smooth deformation of the material as produced from the improved extrusion method using nano-powder.

On the other hand, the present invention is applied to the improved extrusion method as described above to make the deformation of the material smoothly to prevent the phenomenon of cracks on the surface of the extruded molded body (micro scale powder compaction) ) To provide an apparatus and an extrusion die.

In order to achieve the above object, the present invention provides a method for producing a molded body by inserting the nano-powder into an extrusion apparatus and extruding; Extrusion for manufacturing a micro-scale molded article using the nano-powder, characterized in that the step of making the green compact through compacting before the nano-powder is put into the extrusion device, and the extruding the green compact into the extrusion device A method is provided.

At this time, the density of the green compact is compacted so that the green compact has a value equal to or greater than the density capable of maintaining its shape.

The nano powder is characterized by being spherical, the material of the nano powder is a polymer, plastic, or metal is used.

On the other hand, the present invention may further comprise the step of sintering the molded body after extrusion.

According to another aspect of the present invention for achieving the above object, a compacting mold having an injection hole into which the nanopowder is injected, a lower punch provided at a lower side of the compacting mold, and a lower punch at an upper side of the compacting mold. And an upper punch installed to face the upper punch, and a ram installed on the upper punch to transfer the pressing force to the upper punch so that the nano powder becomes a green compact. Is provided.

On the other hand, according to another aspect of the present invention for achieving the above object, a container into which the nano-powder green compact as the material to be extruded; An extrusion die installed below the container, the die hole having a conical shape; A backer installed below the extrusion die to support the extrusion die; Provided is a nano-powder extrusion device for producing a micro-scale molded article, characterized in that it comprises a; extrusion punch for pressing the green compact.

At this time, the die angle (DIES 半角; Die angle) of the extrusion die is characterized in that it forms an angle within the range of 30 ~ 60 °.

The present invention forms a green compact through the process of compacting the nanopowder prior to extrusion, and then performs the extrusion using the green compact so that the extrusion load can be evenly transmitted to the entire material to be extruded, thereby making it necessary for extrusion. It has the effect of lowering the load.

In addition, if the load required for extrusion is lowered, it is possible to realize a sufficient extrusion load even if the extrusion apparatus is downsized, so that the extrusion apparatus can be downsized.

In addition, parts and molded bodies produced from the improved extrusion method of the present invention are smoothly deformed of the material, so that cracks do not occur on the surface, thereby obtaining a good surface.

Meanwhile, the present invention provides a micro scale powder compaction apparatus and an extrusion die suitable for application to an improved extrusion method, so that deformation of the material can be made smoothly, and cracks are generated on the surface of the extruded molded body. Is effectively prevented.

Hereinafter, with reference to FIGS. 1 to 7 will be described in detail for the practice of the present invention.

FIG. 1 is a sectional view of a compacting apparatus applied to the present invention, and FIG. 2 is a perspective view of the green compact formed by the compacting apparatus of FIG. 1.

3A is a cross-sectional view of an extrusion apparatus to which the extrusion die of the present invention is applied, FIG. 3B is an enlarged view of the extrusion die of FIG. 3A, FIG. 4 is a perspective view of the extrusion die of the present invention applied to the extrusion apparatus of FIG. 3A, Figure 5 is a reference picture showing the surface state of the gear extruded by the extrusion device to which the extrusion die of the present invention is applied.

On the other hand, Figure 7 is a perspective view of a conventional extrusion die, Figure 8 is a reference picture showing the surface cracks of the gear extruded by the conventional extrusion die.

The present invention is a method for producing a molded body by inserting the nano-powder, such as metal, polymer, plastic, etc. into the extrusion device, the step of making the green compact through compacting before the nano-powder is injected into the extrusion device And, it is characterized in that it comprises a step of extruding the green compact 200 in an extrusion apparatus.

At this time, the nano-powder is spherical, it is produced by the explosion molding method.

The relative density of the green compact 200 is 0.84 or more, but the relative density is obtained by dividing the dry weight by the value obtained by subtracting the weight of the water from the impregnating weight and dividing this value by the metal density.

In the present invention, the green compact 200 forms a kind of billet by agglomeration made by compacting nano powder, but is different from billets used for general metal extrusion. That is, the billet used for general metal extrusion is produced by a casting method in which molten metal is poured into a mold, cooled, and solidified, and the physical and chemical properties and the extrusion characteristics of the green compact 200 of the present invention made by compacting powder mechanically. There is a difference.

In addition, it is assumed that the molded article of the present invention is defined as including a preform to which sintering and other heat treatment are applied after extrusion.

On the other hand, the present invention, for the compacted powder of the nano-powder, the compacting mold 110 having an injection hole into which the nano-powder is injected, the lower punch 120 is installed on the lower side of the compacting mold 110, the compacting mold The upper punch 130 is installed on the upper side of the 110 to face the lower punch 120, and the upper punch 130 is installed on the upper punch 130 to press the force to press the nanopowder to the green compact 200 It is provided with a nano powder compaction apparatus including a ram 140 to deliver to the punch (130).

The ram 140 may operate in any operating manner, such as mechanical or hydraulic.

In addition, the present invention is a container 310 into which the green compact 200, which is a material to be extruded, is inserted, an extrusion die 320 installed below the container 310, and is installed below the extrusion die 320 and extruded. In the extrusion apparatus including a backer 330 supporting the die 320 and an extrusion punch 350 for pressing the green compact 200, the die holes 321 of the extrusion die 320 are conical overall. It is characterized by the formation of a (ical) hole.

Specifically, the die hole is composed of a conical portion (C) for smooth deformation of the material and a die land portion (D) for forming a desired molded body.

At this time, the die half angle (DIES () of the extrusion die 320 may have a range of 0 ~ 90 ° but the smaller the angle can be obtained a good gear shape. That is, preferably, the die half (DIES 의) of the extrusion die 320 to form an angle within the range of 30 ~ 60 °.

On the other hand, the outer side of the extrusion device to heat the container 310 and the extrusion die 320, etc. Heater 340 is installed.

The operation of the present invention configured as described above is as follows.

According to the present invention, the nano powder is compacted through a compacting apparatus to be made into a compact 200, and then injected into a container 310 constituting the extrusion apparatus and hot extruded in a heated state. Since the extrusion is made in the state (200), because the extrusion is made even at a small load, it is possible to miniaturize the extrusion apparatus.

That is, conventionally, the nano-powder is injected into the extrusion apparatus, which is extruded immediately. In this case, the total volume of the nano-powder injected is large, and thus, a large extrusion pressure is required for the extrusion, which makes it difficult to miniaturize the extrusion apparatus.

In particular, the conventional extrusion die 320a has a structure in which the die hole 321a formed in the center portion is sharply narrowed (see FIG. 7), so that deformation of the material is not performed smoothly, thereby causing cracks on the surface of the material (see FIG. 8). There was a disadvantage.

In addition, conventionally, a very large force must be applied to the extrusion pressure to be delivered to the bottom of the nano-powder injected into the extrusion device, even for this purpose it was difficult to miniaturize the extrusion device.

However, the present invention is to compact the nano-powder in the compacting apparatus to form a compacted body 200, so that the compacted powder 200 is put into the extrusion apparatus to extrude, to solve the problems caused by the conventional nano-powder direct extrusion It becomes possible.

That is, since the green compact 200 is integrated by compacting the nanopowder, the extrusion pressure is directly transmitted to the lower compact of the green compact 200 so that the extrusion pressure can be lowered compared to the conventional extrusion method. It is possible to miniaturize.

Experimental Example

Hereinafter, an embodiment of the present invention will be described in more detail through an experiment in which fine gears are manufactured using metal nanopowders.

end). Overview of the experiment

Recently, the production of micro parts has been increasing, and since the micro parts are applied in various forms to medical, sensors, and electronic devices, the utilization of nano powder is increasing. Therefore, this experiment focused on the production of fine gear using nano powder.

To date, microgear machining has mainly been made by MEMS or LIGA methods, and the material is often polymer or plastic. This method was disadvantageous in terms of equipment cost and mass production was impossible. In this embodiment, a spur gear-shaped preform having a pitch circle diameter of 1.5 mm was produced using tin powder having an average particle size of 230 nm by using the hot extrusion method. In order to produce a gear having a precise shape and strength by sintering the preform, it is important to have a good surface shape and a high relative density. Accordingly, the effects of the extrusion process variables such as temperature, die angle, ram speed, and relative density of initial materials were confirmed.

I). Experiment apparatus and experimental conditions

First, referring to the experimental apparatus and experimental conditions of the present embodiment, the powder used in the experiment was a tin powder, having a purity of 99.9%, an average particle size of 230 nm, and a spherical shape, and manufactured by an explosion molding method. In addition, by coating the surface of the powder with an oxide film about 2nm was stabilized so as not to react in the air. The green compact was uniaxially press-molded into a compact powder by adding 1.48, 1.33, and 1.18 g of tin powder to a relative density of 0.84, 0.85, and 0.86, respectively. The green compact size was Φ4.8 and the height was 12mm, and a release agent was used to prevent adhesion and adhesion and to improve the surface aesthetic at the time of manufacturing the green compact.

Extrusion equipment is AISI H-13 material of the American Steel Council, and the wire is discharged and punched, container, die, backer as shown in [Reference 1] below. Produced.

[Reference Figure 1] Reference Photo of Extrusion Apparatus Used in Experiment and Dimensional Design

The gear shape is 6 gear teeth, module 0.25, outer diameter 2 mm, pitch diameter 1.5 mm, pressure angle 14.5 ° and die land length is 1 mm. Die half angles were produced at 30 °, 45 °, 60 °, and 90 °, and the extrusion ratios were all 10.2: 1.

The experimental conditions are shown in [Table 1] below, and the process variables consist of temperature, ram speed, die half angle and initial relative density of green compact.

TABLE 1

Hot Extrusion Condition Condition Temperature (℃) 100,120,140,160 Relative density 0.84,0.85,0.86 Die half angle (°) 30,40,60,90 Punch Speed (mm / min) 60,120,240

All). Experiment result analysis

The surface and cross section of the extruded shape according to the conditions of Table 1 are shown in [Reference Figure 2] below, and the extrusion load is shown in [Reference Figure 3].

[Reference Figure 2] Actual picture showing the shape of the molded body extruded under each condition

[Reference Figure 3] Graph showing the size of the extrusion load for each condition

The extrusion load decreased with increasing temperature, and cracks occurred on the surface at 100 and 160 ° C. The cause of the surface crack is due to the speed difference between the outside and inside of the material due to the friction between the material and the wall of the die land part. Therefore, in order to reduce such friction, it is necessary to increase the temperature to reduce the extrusion load to prevent the adhesion by pressure.

In addition, release agents should be sprayed onto the die prior to extrusion to prevent the material from sticking. At 160 ℃, the load decreased, but due to the high temperature, the surface of the extruded specimens cracked and oxidized, resulting in poorly shaped gear teeth and color change.

As the ram speed was increased, the load increased as the ram speed was changed to 60, 120, 240 mm / min. This is because, as the extrusion speed increases, the work applied per unit time increases. In addition, if the extrusion rate is too high, it is recommended that the material be processed at an appropriate speed since the temperature may rise due to pressure and cause initial melting on the surface.

The die half angle was changed to 30, 45, 60, and 90 °, and the load increased as the die half angle increased. Good gear shape and cross section was shown at 30 ~ 60 °, but surface crack occurred at die half angle 90 °. This is because the shear deformation is severe and the extrusion load is large, and the adhesion of the material to the die land part occurs periodically due to the friction between the green compact and the extrusion die.

In addition, the experiment was carried out by changing the relative density of the initial green compact to 0.84, 0.85, 0.86.

Experimental results show that the lower the relative density, the lower the relative density, the extrusion tends to be delayed due to the compacting of the green compact, and the lower the initial mass, the shorter the extrusion length, thereby reducing the load due to the decrease in frictional force. However, since the relative density of the extruded specimens decreases as the initial relative density decreases, deformation or torsion of the preform may occur in the sintering process. Therefore, it is judged that increasing the initial relative density is advantageous to increase the relative density.

[Reference Figure 4] Graph showing extrusion load by initial relative density

In this experiment, the initial relative density is obtained by the following equation.

Initial relative density = {dry weight / (impregnated weight-underwater weight)} / metal density

Here, the dry weight (g) is the weight of the green compact specimen, the impregnation weight (g) is the measured weight after the green compact specimen is placed in a paraffin solution to block pores, and the weight in water (g) is the green compact specimen after impregnation with paraffin. Weight, metal density (g / cc) is the density of the original metal]

In the above formula (impregnating weight-water weight) means the volume of the green compact specimen. That is, the green powder specimen completely submerged in water decreases the weight of the green powder specimen by the buoyancy to the weight of the water corresponding to the volume of the green powder specimen, so that the volume of the green powder specimen and the dried pressure obtained from the reduced water weight and water density are reduced. The density can be calculated from the weight of the powder.

On the other hand, since the relative density of the extruded material has a great influence on the sintering process, the initial and end portions of the extruded specimens were cut out by 2 mm for each condition, and then the relative density was measured. As a result, as shown in the following [Reference Figure 5], the higher the extrusion temperature was able to produce a preform having a higher relative density as the die half angle is smaller.

[Reference figure 5] relative density for each condition

Therefore, the optimum process conditions in this experiment were the temperature 140 ° C, die half angle 30 °, ram speed 120 mm / min, initial relative density 0.86, and the preform had the highest relative density value.

As described above, in the present experiment, the experiment was carried out for the purpose of improving the shape accuracy and density distribution of the preform having a spur gear shape to prevent the distortion of the component during the sintering process. As a result, the relative density of the extruded specimens increased with increasing temperature and initial relative density, and the relative density increased with decreasing die half angle. In addition, the experimental results showed that the relative density was about 0.9. This means that shape deformation due to shrinkage during sintering can be greatly reduced.

The rights of the present invention are not limited to the embodiments described above, but are defined by the claims, and those skilled in the art can make various modifications and adaptations within the scope of the claims. It is self-evident.

That is, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the technical idea of the present invention.

Recently, the production of micro parts has been increasing, and since the micro parts are applied in various forms to medical, sensors, and electronic devices, the utilization of nano powder is increasing.

Therefore, the present invention can be variously applied to medical, sensor, and electronic device manufacturing fields that require ultra-fine parts and finished products, such as manufacturing a fine gear using nano powder.

1 is a cross-sectional view of a compacting apparatus applied to the present invention

FIG. 2 is a perspective view of the green compact formed by the green compact of FIG.

3A is a cross sectional view of an extrusion apparatus to which an extrusion die of the present invention is applied.

FIG. 3B is an enlarged view of the extrusion die of FIG. 3A

4 is a perspective view of an extrusion die of the present invention applied to the extrusion apparatus of FIG. 3A

5 is a reference picture showing the surface state of the gear extruded by the extrusion device to which the extrusion die of the present invention is applied.

6 is a flow chart showing the extrusion process of the present invention in order

7 is a perspective view of an existing extrusion die

8 is a reference picture showing the surface crack of the gear extruded by the conventional extrusion die

Explanation of symbols on the main parts of the drawings

110: compaction mold 120: lower punch

130: upper punch 140: ram

200: green compact 310: container

320: extrusion die 321: die hole

330: backer 340: heater

350: punch

Claims (9)

What is claimed is: 1. A method for producing a molded body by injecting nano powder into an extrusion apparatus and extruding; Before the nano-powder is put into the extrusion apparatus to make a compacted body 200 through the compacting, Extrusion method for producing a micro-scale molded article using a nano-powder, characterized in that the green compact is put into the extrusion apparatus to extrude. The method of claim 1, The green compact 200 is an extrusion method for producing a micro-scale molded article using nano-powder, characterized in that the powder is compacted to have a density or more that can maintain the shape of the green compact. The method of claim 1, The nano-powder is characterized in that the spherical, the extrusion method for producing a micro-scale molded article using a nano-powder, characterized in that the material of the nano-powder is a polymer, plastic, or metal. The method of claim 1, An extrusion method for producing a micro-scale molded article, characterized in that it further comprises the step of sintering the molded body after extrusion. It is manufactured by the method of any one of Claims 1-4, The micro scale molded object characterized by the above-mentioned. A compaction mold 110 having an injection hole into which the nanopowder is injected, A lower punch 120 installed at a lower side of the compaction mold 110, An upper punch 130 installed on the upper side of the compaction mold 110 so as to face the lower punch 120; The nano-powder compacting apparatus for manufacturing a micro-scale molded article, characterized in that it comprises a ram 140 is installed on the upper punch 130 to transmit the pressing force to the upper punch so that the nano-powder is a green compact (200). . A container 310 into which the nano-powder green compact 200 which is an extruded material is injected; An extrusion die 320 installed below the container 310 and having a die hole 321 having a conical shape as a whole; A backer 330 installed below the extrusion die 320 to support the extrusion die 320; Extrusion punch (350) for pressing the green compact (200); Nano powder extrusion apparatus for manufacturing a micro-scale molded article, characterized in that it comprises a. The method of claim 7, wherein The die hole 321 is a nano-powder extrusion device for manufacturing a micro-scale molded article, characterized in that the conical portion (C) to make the deformation of the material is made smoothly and the die land portion (D) to make the desired shaped body. The method of claim 7, wherein Die half of the extrusion die 320 is a nano-powder extrusion device for producing a micro-scale molded article, characterized in that to form an angle within a range of 30 ~ 60 °.

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