JPS62202003A - Molding method for powder - Google Patents

Abstract

PURPOSE:To mold raw material powder to be treated with a hyrostatic press with high dimensional accuracy by packing said powder into a rubber bag inserted into a casting mold which is formed by vacuum-packing and molding dry sand with an air permeable film then sucking the inside thereof to a vacuum and premolding the powder. CONSTITUTION:A pattern 3 is provided to a mold stool 2 having vent holes on a suction box 1 and the air permeable film 7 is coated thereon. A metallic flask 11 with a filter 10 is then imposed on the mold stool 2 and the powder 16 for forming a mold support such as dry sand is thrown into the flask. The inside of the flask is sucked to a vacuum by a vacuum pump 14 to form the cope of the costing mold. The brag is similarly formed by using a metallic flask 19. The cope and drag are joined to each other to obtain the casting mold. The rubber bag is then inserted into the cavity of the casting mold and the inside of the bag is sucked to a vacuum by vacuum pumps 6, 14 through the above-mentioned film 7 to expand the bag. The raw material powder 22 is packed into a rubber mold 28 formed in such a manner and after the inside thereof is sucked to a vacuum by a vacuum pump 27, the inlet is clamped 29 and the preform 31 is obtained. The preform 31 is thereafter treated with the cold hydrostatic press, by which the molding compacted by shrinkage is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for molding powder, which involves molding powder such as metal powder or ceramics to obtain a molded body with high dimensional accuracy.

[Conventional technology]

The cold isostatic pressing method is a method in which a bag of powdery rubber-like elastic material such as metal or ceramics is filled and sealed, and a liquid such as water or oil is pressed from the outside as a pressurizing medium. . In this method, latex, Pv
A rubber-like mold such as C or polyurethane is used. This rubber-like mold must be strong and thick enough not to be deformed by the weight of the powder it is filled with.

However, when performing the above-mentioned cold isostatic pressing method, the deformation behavior of the rubber and powder fillings is different, so the hydrostatic pressure applied from each part of the rubber-like mold is not directly transmitted to the powder filling inside, and the corner Powder in parts may be restrained by the rubber and difficult to shrink. For this reason, the molded body will not fit into a shape that deviates from the cavity shape of the rubber-like mold when no load is applied, and stress may remain inside, causing cracks. Therefore, there is a problem in that it is difficult to obtain a perfect molded product with high dimensional accuracy using the normal cold isostatic pressing method. For this reason, in contrast to the cold isostatic pressing method, a method was invented in which a mold is formed by applying tension to a thin rubber-like bag.
-183780].

According to this method, the rubber-like bag shrinks following the shrinkage of the powder filling, so that the filling uniformly shrinks and a molded article having a shape similar to the initial filling is obtained. However, the breathable mold support used in this method requires sufficient surface properties for the rubber-like elastic material to slide and dimensional accuracy of the cavity via, making it expensive. Therefore, there was a problem in that the summary was limited to those that were produced in relatively large quantities.

Therefore, in order to solve the above-mentioned problems, there is a method in which this expensive air-permeable mold support is replaced with a mold support whose shape is maintained by filling the powder with negative and positive. In this method, the main part 1 is composed of a water-soluble film and a filter, and a thin rubber-like material with water supported on the outer surface is placed in the cavity of a mold support that maintains its shape by making the powder filling negative and positive. The water-soluble film is dissolved by contact with the rubber-like bag, and the suction effect is applied to the rubber-like bag, and tension is applied to this rubber-like bag to bring it into close contact with the cavity wall. Created a mold.

[Problem that the invention seeks to solve]

The following are two problems with the method configured as above.
There are several points. The first point is that the water molecules ik to be carried in the rubber-like bag for insertion must be appropriately controlled. If the amount of water to be supported is too small, the water-soluble film will not dissolve and the rubber-like mold will not adhere tightly to the cavity wall of the mold support. On the other hand, if the amount of water to be supported is too large, the water-soluble film will locally dissolve first, and the rubber-like mold will not adhere uniformly, resulting in the mold breaking.

The second problem is that the powder constituting the mold support Y becomes moist due to the moisture carried thereon, and when reusing the powder, an operation is required to dry the powder.

The present invention was made in order to solve the above-mentioned problems, and an object of the present invention is to obtain a method for molding powder with high dimensional accuracy.

[Means for solving the problems] The present invention has been made in order to achieve the above objects,
A broken mold is created by vacuum-backing the dry sand with a breathable film, and a rubber bag whose surface is wetted with water is inserted into the clear mold, and the rubber is dissolved in the breathable film to spread and cover the inner surface of the mold. The present invention provides a powder molding method 7gt in which after the rubber is brought into close contact, the raw material is filled, the inside of the rubber is vacuum-suctioned to maintain the shape, and then the sand mold is removed and the powder is heated in a cold isostatic press.

[For production]

Filling of powder A rubber bag-like material is expanded and brought into close contact with the inside of a breathable mold support whose shape is maintained under negative pressure to form a mold. After vacuum degassing, the mold is sealed, the breathable mold support is dismantled, and the preform Y is housed in a bag-like object.
It is taken out and subjected to cold isostatic pressing treatment to make it denser.

[English example]

In the present invention, powder for forming a support is sealed in a space of a desired mold shape, which constitutes the main parts of a film and a filter, and has at least a wall corresponding to a cavity made of an air-permeable film. A process of creating a breathable mold support made of powder by maintaining the shape of the space by suction from the vacuum chamber, and inserting a bag made of a thin rubber-like elastic material into the cavity of the mold support. , a process of applying suction to the rubber-like bag through a breathable film to create tension and forming a mold consisting of the rubber-like bag that adheres to the cavity wall, and injecting metal or A step of filling powder such as ceramics, a step of suctioning the inside of the mold to create a negative pressure and then sealing the mold, a step of removing the powder constituting the mold support, and a step of filling the mold thus obtained. The film used in the present invention relates to a method for forming powders of gold and ceramics, which comprises the step of cold isostatic pressing an encapsulated preform to form a compact. It is also necessary to have an appropriate thickness t with high tensile strength.

Specific examples of materials with such characteristics include polyethylene film, polypropylene film,
These are soft polyvinyl chloride films, polyvinyl alcohol-based synthetic resin films, chlorinated rubber films, polybutylene films, etc., and their thicknesses cannot be uniformly determined because they vary depending on the shape of the target mold and where the film is applied. No, but 20 μm to 200 if necessary
An appropriate selection is made from those on the order of μm. Moreover, the breathable film applied to the cavity wall can be used even if pinholes are formed in the above-mentioned film by mechanical or chemical treatment. A polyolefin-based breathable film can also be applied as is. Specific examples of the means for making the pinhole include a method using a needle, a method using a laser beam, a method using a solvent, etc., and these methods can be selected and used in combination as appropriate. These breathable films require a negative pressure on the powder charge until the rubber-like bag is inserted, so a pressure difference must be created across the film.

For this reason, the range of application of breathable films that can be applied using the suction force from the filter is different, but the film surface 1
The area occupied by the through pores is 0.001 parts to 0.00 parts.
Preferably, the amount is 2 parts, and the pore diameter is preferably 1 part or less. Particles constituting the powder for forming a mold support must not be easily powdered or deformed when placed in the flat space of the support, but particles such as sand, plastic powder, ceramic powder, metal powder, etc. It is possible to choose from a wide range of options. It is desirable that the metal or ceramic powder to be molded be processed to have a powder size and shape with good fluidity. Specifically, in the case of stainless steel, tool steel, superalloys, etc., spherical powder produced by argon gas atomization, vacuum atomization, or rotating electrode method is suitable, and titanium and titanium alloys are also produced by plasma rotating electrode method. The resulting spherical powder is good. In addition, fine metal powders such as carbonyl iron and carbonyl nickel, cemented carbide powders, alumina, zirconia, silicon nitride, silicon carbide, sialon, etc. are usually irregularly shaped fine powders of several μm or less and do not have good fluidity, so they are processed into granules. It is preferable to use spherical powder.

1 to 12 are explanatory diagrams showing embodiments of the present invention. First, as shown in FIG. 1, a surface plate 2 having a vent hole AI is set on top of the suction box 1, and a model 3' is placed at a predetermined position on the surface plate 2.

Next, as shown in FIG. 2, a vacuum suction system consisting of a three-way switching valve 4, a dust filter 5, and a vacuum pump 6 is attached to the suction box 1, and a breathable or non-breathable film 7 is placed above the model 3. A clamp frame 8 and an electric heater 9 are installed. Note that the heating is not limited to the electric heater 9, but may be a gas heater or a hot air heater. After activating the vacuum pump 6, the film 7 is heated with an electric heater 9, and when it reaches the appropriate temperature for forming, the clamp frame 8 is moved to the surface plate 2, and the film 7 is heated by vacuum suction as shown in FIG. is brought into close contact with the model 3 and the surface plate 2, and then the clamp frame 8 is removed and the whole is fixed to the vibrating tape IL/17 at 5 as shown in FIG. Note that in the case of a simple shape, the step of heating the film 7 with the electric heater 9 is not necessarily necessary. Next, place model 5'lk on surface plate 2: K to surround it.

Filter 10! Place an 11ft metal frame and place 12.0ft of pulp on it. Filter 13. The vacuum suction system consisting of the pump 14 is tangentially connected and the sleeve 15 covered with the film 7 is attached to the model 3.
, and the powder 16 for molding the mold support is added thereto. Next, the vibrating table 17 is operated to pack the mold support forming powder 16 into the metal frame 11 under pressure, and excess powder is removed by scraping. After doing this, as shown in FIG. 5, the vacuum pump 14 is operated, the upper part of the metal frame 11 is covered with a non-permeable film, and
After stopping, as shown in the sixth factor, the metal frame 11yk moves upward and performs die cutting.

A lower mold is molded using the metal frame 19 using the same procedure as the upper mold described above, and the upper and lower metal frames 11.1 are formed as shown in FIG.
9'Y match. The cavity wall formed by fitting the upper and lower metal frames 11 and 19 must be made of a breathable film. If the film 7 used in FIG. 2 is breathable, the following description is unnecessary.

It is necessary to open bottle balls in the mold support made in FIG. 6 at the places that will become the cavity walls in the future. When making simple shapes such as cylinders, spheres, rectangular parallelepipeds, etc., it is sufficient to drill one or two holes of 0.51 diameter per shoulder of the cavity wall. In the case of a complex shape, it is desirable to preferentially drill holes at the ridgeline and apex of the cavity wall. It is advantageous to make as many small holes as possible in order to faithfully copy the shape of the cavity wall of the mold support. Of course, even if you use a breathable film, it is okay to have pinholes on the wall of the cavity.For example, the upper frame is made of film with holes made, and the lower frame is made of breathable film. Depending on the shape, it may be more advantageous to use it.

Next, as shown in FIG.
5, and enlarged and brought into close contact with the cavity wall of the rubber bag 20L' via a breathable film.

If the opening area of the film is too large, it is possible to suppress the sudden expansion of the rubber bag 2o by lowering the suction force of the pump to the extent that the mold support does not collapse. can prevent breakage. In this way, the rubber bag 2° adheres tightly to the entire cavity wall to form a mold of thin-walled rubber-like material. After this mold is completed, as shown in FIG.
The vacuum pump 14. Pump 6 continues to operate. material? After filling No. 2, as shown in Fig. 10, the dust filter 24'Y is installed in the date 21, and the internal pressure is reduced to below ft100 torr, preferably below 1Q torr, via the valve 25 and filter 26 with the vacuum pump 27. Deaerate the air existing in the gaps between the raw material powder.

While you are doing this, press the button 14. The pump 6 continues to operate, and after the internal pressure applied to the rubber mold 28 reaches a predetermined value, the vacuum pump 14 stops, and the three-way switching valve 12
When the external pressure of the upper rubber mold 28 is returned to atmospheric pressure by switching, the rubber at the inlet of the rubber mold 28 is soaked, so the gate 21 is pulled up and the rubber at the inlet is clamped and sealed with the clamps 29. The vacuum pump 27 is stopped, and the dust filter 24 and gate 21 are removed. During this time, the operation of the vacuum pump 6 continues. Next, gold frame 11°191
jt! KM above the screen 6° shown in Figure 11 while lying down.
After this, the vacuum pump 6 is stopped, and the outside of the lower rubber mold is returned to atmospheric pressure by switching the three-way switching valve 4. In this operation, the powder for forming the mold support in the metal frame 11 and 19 collapses under its own weight, breaks the permeable film and filament A/AV, passes through the screen 30, and falls, forming the preform. Body 31 remains on the screen. This preformed body 3
Since the inside of the preform 31 is under negative pressure, a hydrostatic pressure equivalent to the pressure difference from atmospheric pressure is applied to the preform 31, which allows it to maintain its shape even without external support. be able to.

Finally, this preliminary bottom body 51%r: is placed in a cold isostatic press 32 as shown in FIG. When held, the preform 31 shrinks and densifies to become a molded body 56. After performing this operation, the pressure inside the apparatus is reduced to normal pressure, and the molded article 53'1\: is taken out.

The molded body 63 thus obtained can be easily taken out by removing the clamp 29 and then peeling off the rubber mold 29. The molded body 33ti can also be sintered to form a sintered body, if necessary.

Specifically, a molded body obtained by the above method using cemented carbide granules of WC-IQ%co as a raw material was degreased, vacuum sintered,
A high-density sintered body can be obtained by hot isostatic pressing (HIP), and Sj, N, -13%y, o,
A sintered body can also be obtained by degreasing a molded body obtained by the above method using the granules as a raw material and then sintering it under normal pressure in a nitrogen atmosphere. Furthermore, INI manufactured by the rotating electrode method
A compact obtained by the above method using Do superalloy spherical powder as a raw material may be sintered in a vacuum and further subjected to HIP treatment to form a high-density sintered compact.

In the specific example of the above example, two types of molded bodies were made: C1018 steel spherical powder (particle size 80 to 200 mesh) and alumina granules (particle size 20 to 100 μm).First, a shaft with a diameter of 20 stories and a length of 60 mesh was made. and a diameter of 80 m5 and a thickness of 15 installed at a position 20 m from the end.
Using a model consisting of the disc of (2), crushed sand (particle size 100 to 150 mesh) was used as the powder for the mold support, E, V, A, 50μ thick film was used, and a thin rubber-like elastic material was used as the film. Approximately 2 thick as a bag
A rubber latex bag with a diameter of approximately 10 m and a length of 50 m was used. A heated piano wire with a diameter of 0.3 mm is pressed against the inner wall of the mold support cavity, and 5-
Holes were made at intervals to obtain a preform by the method described above, and the preform was compacted by cold isostatic pressing at a pressure of 3000 atm to obtain a compact disk. When the roundness of this disk was measured, there was almost no variation in the disk diameter, and the rate of change was within 1.5%. The diameter of the disk at this time was as follows.

Steel spherical material 72.92±0.15as Alumina granules 68.13±0.11m [Basic of the invention] As is clear from the above description, according to the present invention, an expensive molded body can be used as a breathable mold support. without using
It is now possible to use a mold support made of inexpensive powder, and by using a breathable film, it is possible to prevent contamination of the powder by moisture. Not only can this be eliminated, but it also has the remarkable effect of allowing molded bodies with high dimensional accuracy to be manufactured at low cost from metal and ceramic powders.

[Brief explanation of drawings]

Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Figure 9% Figure 10, Figure 11, Figure 12 is the present invention. It is an explanatory diagram showing an example of. 7.18...Film, 16...Powder for forming a support, 20...Bag. In each figure, the same reference numerals indicate the same or equivalent parts. Book frame; Film 8; Club frame Fig. 2 91 J-2- Fig. 7 Fig. 8 Fig. 9 Fig. 1 ON 2 sky

Claims (1)

[Claims] A mold was made by vacuum-packing dry sand with a breathable film, and a rubber bag whose surface had been wetted with water was inserted into the mold, and the breathable film was dissolved to spread the rubber and tightly adhere to the inner surface of the mold. A powder forming method in which the powder is filled with raw material powder, the inside of the rubber is vacuum-sucked to maintain the shape, the sand mold is removed, and the powder is subjected to cold isostatic pressing.