JPH0432503A - Method for compacting powder - Google Patents

Abstract

PURPOSE:To manufacture a compact body composed of metal or ceramic by setting lost wax pattern material in a wooden flask, removing the pattern after forming a support molding material having opening part at the upper pat to outer periphery thereof, packing the metal or the ceramic powder in this cavity and pre-sintering. CONSTITUTION:The pattern 1 having complicate shape made of material having easily melting with heating of wax, etc., is set in the wooden flask 4 and the support molding material 3 composed of synthetic resin, etc., mixing the metal or the ceramic is packed to the outer periphery thereof. As the other way, after coating and making hard of the support molding material 3 on outer periphery of the pattern 1, the wax for forming the pattern 1 is melted with heating and removed to form the cavity having pattern shape, and after packing the metal powder or the ceramic powder in there, this is charged in a sintering furnace, and pre-sintered at e.g., 1100 deg.C. This is taken out from the sintering furnace and the support molding material 3 is collapsed and removed and the compact body composed of the metal or the ceramic have the same dimensional accuracy as the pattern 1 is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for obtaining a complex-shaped molded body from powder of metal, ceramics, or the like.

(Prior art) Powder forming methods include - shaft forming, cold isostatic pressing, injection molding, etc. - Axial forming and cold isostatic pressing are forming methods mainly for irregularly shaped powder. By molding under high pressure, the powder is plastically deformed and the powders are entangled, giving the molded body shape retention.Hard powders that do not easily undergo plastic deformation and spherical powders that cannot be expected to become entangled with each other. Molding is carried out by adding a molding aid such as wax to the powder so that the molded product has shape retention properties due to its adhesive strength.

However, injection molding is often used to mold these hard powders and spherical powders. Powder injection molding is a method in which a thermoplastic resin is added to powder as a molding binder, the heated and mixed kneaded product is injected into a mold, and then cooled and solidified to obtain a molded body.

[Problem to be solved by the invention]

Uniaxial molding and cold isostatic pressing are considered to be the most suitable means for molding irregularly shaped powders such as metals that are likely to become entangled with each other due to plastic deformation. When using these methods such as hard powder, ceramic powder, metal spherical powder, etc., some forming aid must be added. However, even if molding is possible in this way, if the powder particle size exceeds 10, the molding aid will be decomposed and removed during the degreasing process, causing the molded product to lose its shape-retaining ability and deform or collapse. happened often.

Similarly, in injection molding, it was difficult to apply coarse powder in terms of shape retention of the molded product. In addition, since it contains a large amount of molding binder, the degreasing process requires 1 to 7 days, and conventional molding methods that use a large amount of molding binder have their own problems. This problem became more pronounced as the shape of the molded article became larger.

The present invention solves the above-mentioned problems, and aims to provide a method for obtaining a complex-shaped molded body from powder of metal, ceramics, etc.

[Means to solve the problem]

The present invention has been made to achieve the above-mentioned object, and includes forming a support mold having at least one opening on the surface of a model of a desired shape of a molded body, and removing the model to fill a cavity obtained with the above-mentioned support mold. It is characterized in that a molded body is obtained by filling powder of a molding material such as metal or ceramics through the opening and then pre-sintering it.

If the model having the desired shape can be taken out from the supporting mold either singly or by dividing it, any material that is difficult to deform may be used, and there is a wide range of possibilities for selecting materials. Applicable materials include metals, ceramics, plastics, and wood.

On the other hand, if it is difficult to take out the support mold even if it is divided, select a material that can be taken out or destroyed by melting, melting, sublimation, etc., as long as it does not interfere with the function of the supporting mold. Materials that can be removed by melting such as wax, PVA, PVB, PE
Materials that can be removed by dissolving in water or organic solvents, such as G, MC, and CMC1 urea, and materials that can be eliminated by sublimation, such as naphthalene, can be used. Among these, waxes that are easily moldable are particularly preferred. Further, powder of metal, ceramics, plastic, wood, etc. may be mixed with these materials in order to adjust strength, rigidity, etc.

There are no particular restrictions on the method of forming a model of a desired shape from these materials. Large blocks may also be machined. It may also be melted and cast into a mold of a desired shape. Injection molding may be performed in a molten or semi-solid state.

The support mold is formed by casting or coating.

There are no particular restrictions on the application method, and brushing, dipping, spraying, etc. can be applied. In the case of the casting method, liquid polyurethane resin, epoxy resin, plaster, etc. can be used as raw materials. A supporting mold is formed by curing these materials, and powders of metal, ceramics, plastic, etc. may be mixed therein in order to control strength and rigidity. On the other hand, in the case of a coating method, water glass, metal alkoxide hydrolyzate, liquid phenol resin, polyurethane resin, epoxy resin, plaster, etc. can be used. A support mold is formed by curing these materials, and in order to control strength and rigidity, powders of metals, ceramics, plastics, etc. may be mixed or sprinkled from the outside. An appropriate supporting mold material is selected in consideration of the preliminary sintering temperature, etc. That is, the supporting mold material must be able to withstand at least until the powder filling in the cavity has shape retention after preliminary sintering is started. Therefore, plastics such as polyurethane resins are used when molding low melting point metals and the like.

The model is removed after the support mold is formed.

The method for removing the model depends on the type of model used, for example, if it can be taken out from the support mold singly or in parts, it is taken out in that way. In addition, in the case of melting and removal, the material is heated to melt it and flow out from the support mold. In the case of dissolution, elution is performed using a solvent that dissolves the model. At that time, heating can be performed if necessary. Sublimation is performed by heating or reduced pressure. It is not necessary to completely carry out these steps; it is sufficient to melt, dissolve, or sublimate the entire model to the extent that it can be taken out without damaging the support mold.

The cavity thus obtained is filled with powder of a molding material such as metal or ceramics. The type of metal, ceramic, etc. only needs to have good fluidity; for example, stainless steel powder,
These include high-speed tool steel powder, tungsten carbide/cobalt mixed powder, alumina powder, silicon nitride powder, and titanium diboride powder. These can also be used in combination of two or more types, if necessary. From the viewpoint of fluidity, the powder particle size is 10 to 1
000p is preferable. It may also be granulated for this purpose. Furthermore, various additives may be added depending on the required physical properties, such as alumina, ittria, etc. in the case of silicon nitride. Filling is performed using the opening of the support mold.

At this time, if necessary, vibration can be added to perform vibration filling.

Next, this filling body is set in a sintering furnace while still in the support mold, and pre-sintered to such an extent that it does not collapse even when taken out from the support mold, and the powder in the filling body is lightly bonded to form a molded body. The preliminary sintering temperature varies depending on the material and particle size of the powder, but it ranges from just below the liquid phase generation temperature (hereinafter abbreviated as Tm (K)) to about 70% of Tm, that is, 0.7Tm to 1
．． OTm is preferred. The preliminary sintering time depends on the temperature, but is usually about 1 to 10 hours, or about 3 to 5 hours.

Preliminary sintering can be performed under normal pressure, but if necessary,
Pressure of about kg/Cu1l may be applied. There is no need to take out the compact after preliminary sintering, and sintering can be continued at a temperature that produces the desired characteristics.

[Effect]

By pre-sintering the molding material powder filled in the cavity of the support mold, the powder particles are lightly bonded to impart or improve shape retention. This method makes it possible to mold metal spheres, hard powders, ceramic powders, etc. that are difficult to mold without using molding aids.

〔Example〕

Example 1 This will be explained according to FIG. A block of paraffin wax with a melting point of 48°C to 50°C was cut to form a shaft with a diameter of 40 mm and a length of 120 mm, a diameter of 120 mm and a thickness of 40 mm.
Anal disc and diameter 120 mm, thickness 40 mm ~
A model 1 was made consisting of a combination of 60 mm irregularly shaped disks. A wooden spacer 2 having a diameter of 40 mm and a length of 40 mm was adhered to the upper part. This was placed inside the wooden frame 4, and calcined gypsum was kneaded with water and poured to a level corresponding to the upper surface of the spacer 2, and left to harden for 24 hours to obtain a support mold 3. Next, Spacer 2 was removed and placed in boiling water for 10 minutes to completely drain the paraffin wax. A cavity was thus formed.

This cavity was placed on a vibrating table 5 as shown in FIG.
was filled with vibration. Immediately insert it into the sintering furnace after filling.
Sintering was carried out at 00"C for 3 hours. After preliminary sintering, the molded product obtained by taking it out of the furnace and collapsing the support mold had excellent transferability and shape retention, and there was no failure even after repeating the same operation 10 times. The reproducibility was also good.

Example 2 This will be explained according to FIG. By heating and melting paraffin wax with a melting point of 48°C to 50"C and casting it into a mold, a shaft with a diameter of 40 holes and a length of 120 pieces, diameter 12
0 Mjl, 40mm thick disc and diameter 120I
A model 1 consisting of a combination of Ml and irregularly shaped disks with a thickness of 40 mm to 60 mm was molded. A wooden spacer 2 with a diameter of 40mm and a length of 40mm was glued to the top of this. spacer 2
A slurry of 70% by weight of 1325 mesh zircon flour dispersed in colloidal silica was applied and dried 5 times on the entire surface except the top surface to form a support mold 3 having a thickness of 2 to 4 mm. Next, remove spacer 2,
It was placed in boiling water for 10 minutes to completely drain the paraffin wax. A cavity was thus formed.

This cavity was placed on a vibrating chiffle 5 as shown in FIG.
was filled with vibration. Immediately insert it into the sintering furnace after filling.
Pre-sintering was carried out at 00°C for 3 hours. After preliminary sintering, the molded body obtained by removing it from the furnace and collapsing the support mold has transferability and
Both shape retention properties were excellent, and even when the same operation was repeated 10 times, there was no failure and the reproducibility was also good.

Example 3 This will be explained according to FIG. A cylindrical model 1 made of nylon with a diameter of 40 mm and a length of 280 mm was made of colloidal silica.
Applying and drying a slurry containing 70% by weight of zircon flower dispersed in 5 meshes was repeated 5 times to create a slurry with a thickness of 2 to 4I1.
A support mold 3 of 11 Tl was formed.

Then, model 1 was extracted and a cavity was formed.

This cavity was placed on a vibrating table 5 as shown in FIG.
was filled with vibration. Immediately insert it into the sintering furnace after filling.
Pre-sintering was carried out at 00°C for 3 hours. After preliminary sintering, the molded body obtained by removing it from the furnace and collapsing the support mold has transferability and
It had excellent shape retention, and even after repeating the same operation 10 times, there was no failure and the reproducibility was good.

〔Effect of the invention〕

As described above, since the filler is pre-sintered within the support mold, it is not only possible to produce a molded body without any molding aid or molding binder, but also the inner surface of the support mold can be transferred as is. This makes it possible to produce molded bodies with high dimensional accuracy.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing a state in which a model is placed in a wooden frame and formed by injecting raw materials for a support mold, and Figs. 2 and 3 are a cross-sectional view showing a model formed by coating instead of injecting raw materials for a support mold. FIG. Figure 4 shows the cavity obtained in Example 2 placed on a vibrating table.
FIG. 3 is a cross-sectional view showing a state in which powder such as ceramics is filled. 1...Model 2...Spacer 3...Support mold 4...Wooden frame 5. Vibrating table 6. Stainless steel rope Applicant: Nippon Button Kan Co., Ltd. Representative Patent attorney Japan-China Political Situation Condolence Map/' No. figure

Claims (1)

[Claims] A supporting mold having at least one opening is formed on the surface of a model having a desired shape of the molded body, and the molding material powder such as metal or ceramic is filled into the cavity obtained by removing the model from the opening. A powder forming method in which a compact is obtained by pre-sintering the powder.