JPH0693405A - Production of thin hollow metallic article - Google Patents

Abstract

PURPOSE:To provide the process for production of the thin hollow metallic article which does not require a large-scale apparatus for production and precision molds and necessitates the shorter working time associated with production operation. CONSTITUTION:A core having a desired shape is formed by the core for production of the thin hollow metallic article consisting of a brazing filler metal, etc. A soln. contg. a flexible compsn. consisting of metal or alloy powder and binder is sprayed to the surface of such core to form a coating layer 12 and this coating layer is dried, by which an intermediate body 11 formed with the porous coating layer on the surface of the core is formed. This intermediate body 11 is heat treated to melt and evaporate the core; thereafter, the flexible compsn. constituting the coating layer is calcined. The thin hollow metallic article 13 is produced with extremely high production efficiency.

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 thin hollow metal article using a solution containing a flexible composition comprising a metal or alloy powder and a binder as materials.

[0002]

2. Description of the Related Art A thin hollow metal material 1 made of a noble metal (for example, a ball forming a necklace or a bracelet) 1 as shown in FIG. 2 has been required to reduce its weight or save the precious metal material. As a method for manufacturing such a thin hollow metal article 1, there is a method in which two hemispherical shell-shaped parts 1a, 1a are manufactured by a casting method or the like, and their respective end portions are joined and brazed.

[0003]

However, in the conventional method for manufacturing the thin hollow metal article 1, a large-scale manufacturing apparatus and a precise mold are required, the cost for manufacturing the mold is high, and two hemispherical shell-shaped products are required. There is a problem that skill is required to bond 1a and 1a, and a long bonding time is required.

The present invention has been made in view of the above circumstances, and provides a method for manufacturing a thin-walled hollow metal article which does not require a large-scale manufacturing apparatus and a precise mold and requires a short processing time in manufacturing work. The purpose is to do.

[0005]

In order to solve the above-mentioned problems, the method for producing a thin hollow metal article of the present invention forms a core having a desired shape by a core for producing a thin hollow metal article made of a brazing material or the like. Spraying a solution containing a flexible composition comprising a metal or alloy powder and a binder onto the surface of the core to form a coating film comprising the flexible composition, and drying the coating film. To form an intermediate body having a porous coating layer on the surface of the core, and then heat-treating the intermediate body to dissolve and evaporate the core, and then to form the coating layer. It is characterized in that the composition is baked.

[0006]

According to the method of the present invention, a flexible composition-containing solution consisting of a metal or alloy powder and a binder is sprayed onto a core of a predetermined shape, so that the surface of the core is filled with the flexible composition. It is possible to form a porous coating layer having a uniform film thickness on the surface of the core by forming a coating layer made of (1) and drying it. When the intermediate body having the coating layer formed on the core is heated and fired, the core is dissolved and evaporated, and the core-forming substance is a porous coating layer of the flexible composition. It will be smoothly discharged to the outside from the pores on the surface, avoiding unreasonable stress acting on the coating layer during firing by the evaporated core-forming substance, and defects such as cracks and deformations in the coating layer. It is possible to form a thin hollow metal article by a continuous series of steps, since it is possible to form a thin hollow metal article by preventing the occurrence of the above phenomenon and further firing it.

Therefore, according to the method of the present invention, a thin hollow metal article can be easily manufactured by the above method without requiring large-scale manufacturing equipment and skill. Further, the thin hollow metal article can be manufactured with extremely high production efficiency, and the cost of the product can be significantly reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the method for manufacturing the thin hollow metal article 1 of this example, a flexible composition containing a noble metal powder is used as a raw material. This flexible composition contains: Noble metal powder 50-98.5% by weight Cellulose water-soluble binder 0.4-10% by weight Surfactant 0.001-5% by weight Oil / fat 0.1-15% by weight The balance consists of water and inevitable impurities.

A flexible composition having the above composition is manufactured by the following method. First, the above cellulose-based water-soluble binder is mixed with water and left for a while to form agar. Next, a surfactant is added to this and mixed, and further, a predetermined noble metal powder is added and mixed. Then, a flexible composition having the above composition is manufactured by adding and mixing fats and oils to the noble metal powder mixture.

Next, the reason why the composition of the flexible composition is determined as described above will be explained. (A) Noble metal powder As the noble metal powder, spherical particles having an average particle size of 50 μm or less,
Irregular or flat powders can be used. The noble metal forming the noble metal powder includes Pt, Ru, Rh, Pd, Ir,
One or more selected from the group consisting of platinum group such as Os, Au and Ag, and alloys containing these are used. This noble metal powder is a main component that constitutes the flexible composition and is a main factor that determines the color of the product, but if its content is less than 50% by weight, it has no effect.
If the content exceeds 98.5% by weight, the elongation and strength of the obtained flexible composition will be reduced, which is not preferable. Therefore, the content of precious metal powder is 50 as described above.
.About.98.5% by weight.

(B) Cellulose Water-Soluble Binder The cellulosic water-soluble binder quickly gels and solidifies when heated, and facilitates maintaining the shape of the molded body.
However, if the addition amount is less than 0.4% by weight, the effect cannot be obtained, while if the addition amount is more than 10% by weight, the viscosity becomes too large and the coating film of the flexible composition is formed by spraying. Will be difficult. Therefore, as described above, the content of the aqueous cellulose-based binder is set to 0.4 to 10% by weight. As the cellulose-based water-soluble binder, methyl cellulose, ethyl cellulose and the like are preferable.

(C) Surfactant When the surfactant is added and mixed, the solid matter produced by the reaction between the binder and water is pulverized, and the mixing property of the noble metal powder and the binder is improved. The action is obtained. However, the amount of surfactant added is 0.00
If the amount is less than 1% by weight, the effect is not sufficient. On the other hand, if the amount of the surfactant added is more than 5% by weight, the viscosity of the obtained plastic composition is lowered and the fluidity is increased to form a uniform coating film. It is not preferable because it is difficult to form. Therefore, as described above, the addition amount of the surfactant is set to 0.001 to 5% by weight.

(D) Fats and oils By adding fats and oils, lubricity can be imparted to the flexible composition. However, the amount added is 0.1% by weight.
If less than 15% by weight, the effect cannot be obtained. On the other hand, if more than 15% by weight is added, the flexible composition becomes oily and slippery, and it becomes difficult to form a uniform coating film, which is not preferable. Therefore, as described above, the content of oil is 0.1 to 1
It was set to 5% by weight.

Examples of fats and oils include higher organic acids (eg phthalic acid) and higher organic acid esters (eg phthalic acid-n-
Dioctyl, n-butyl phthalate), higher alcohols, higher polyhydric alcohols (eg, polyvinyl alcohol, polyethylene glycol, ethers) and the like.

Next, a method of manufacturing the thin hollow metal article 13 according to an embodiment of the present invention will be described with reference to the drawings. First, as shown in FIG. 1A, a brazing filler metal is poured into a mold 10 having a spherical cavity 10a to form a spherical core 11. The diameter of the cavity 10a is 10 mm.

Then, the flexible composition comprising the above composition is dried, and a solution containing the flexible composition prepared by dissolving pulverized powder in water is sprayed onto the surface of the core 11 by a sprayer or the like. A covering film is formed and dried to form the core 11
An intermediate body 12 of a thin hollow metal article having a porous coating layer 12a formed on its surface with a uniform film thickness is formed. Then, the intermediate body 12 is heated in a heating furnace to produce the coating layer 1
The flexible composition constituting 2a is fired. The heating conditions differ depending on the material of the noble metal powder in the flexible composition forming the intermediate 12. The heating atmosphere conditions are as follows: when the precious metal powder has stable physical properties in the air, it is heated and baked in the air, and when the precious metal powder has unstable physical properties in the air, an inert atmosphere is used. And heat to bake. The heating temperature and time are 980 to 1020 ° C. for 2 hours when the precious metal powder in the flexible composition is pure gold, 850 to 890 ° C. for 2 hours when the 18 gold alloy is used, and 1580 to 1620 when platinum is used. 2 hours at ℃.

When heated in this manner, the core-forming substance that constitutes the intermediate 12 is dissolved and evaporated, and is discharged from the pores on the surface of the porous coating layer 12a made of the flexible composition to the outside. . Further subsequently, after the cellulosic water-soluble binder and the fats and oils in the flexible composition constituting the coating layer 12a are evaporated by heat, the coating layer 12a is fired, as shown in FIG. 1 (c). A thin hollow metal article 13 is formed.

The porosity of the flexible composition constituting the coating layer 12a is preferably 5% to 75%.
When the porosity is less than 5%, the core-forming substance can be smoothly discharged to the outside when the intermediate body 12 is heated and the core 11 constituting the intermediate body 12 is dissolved or evaporated. However, the core-forming substance that has been melted or evaporated by heating boils or expands, pressure is applied to the coating film 12a from the inside, and defects such as cracks and deformation are easily generated in the thin coating film 12a due to the pressure. If the porosity is greater than 75%, the thin hollow metal article 13 completed by firing the coating layer 12a does not have the metal thin film densely formed and is fragile and easily broken.

The solution containing the flexible composition for forming the coating film 12a first forms a solid flexible composition as described in the above embodiment, In addition to the method of producing by drying and pulverizing the powder to be dissolved in water or a water-soluble solvent, the concentration of the component elements constituting the plastic composition is adjusted as follows, and it is directly formed into a slurry. Even if the coating solution containing the plastic composition formed as described above is sprayed onto the core 11, and the porosity of the coating layer 12a made of the plastic composition after drying is 5% as in the above-described example. It goes without saying that the manufacturing process of the solution containing the plastic composition forming the coating layer 12a may be any as long as it is within the range of 75% to 75%.

Therefore, a manufacturing example of a thin-film hollow metal article manufactured by using the method for manufacturing a thin-walled hollow metal article according to the above embodiment will be described below. (Production Example) First, wax was poured into a mold having a spherical cavity having a diameter of 10 mm to form a spherical core.

Then, 9% by weight of methyl cellulose, 3% by weight of alkylbenzene sulfonate and phthalic acid-di-2
A binder was prepared by mixing 10% by weight of ethylhexyl and water. 22 parts by weight of this binder and 78 of gold powder
The part by weight was kneaded to obtain a noble metal flexible composition. As the gold powder, pure gold powder having an average particle size of 40 μm was used.

Then, the flexible composition comprising the above composition is dried, and a solution containing the flexible composition prepared by dissolving pulverized powder in water is sprayed onto the surface of the core by a sprayer or the like. A film is formed and dried to give a film thickness of 1 on the core surface.
mm to form an intermediate having a porous coating layer having a porosity of 25%. Then, after heating this intermediate in a heating furnace in the air at 150 ° C. for 2 hours, the flexible composition forming the coating layer was further baked at 1000 ° C. for 2 hours. In this way, a thin hollow metal article having a film thickness of 0.8 mm could be obtained.

As described above, according to this embodiment, the surface of the core 11 is sprayed onto the core 11 having a predetermined shape by spraying the solution containing the flexible composition comprising the metal or alloy powder and the binder. It is easy to form a porous coating layer 12a on the surface of the core 11 with a uniform film thickness by forming a coating film made of the flexible composition on the core and drying it. When the intermediate body 12 composed of the core 11 covered with the coating layer 12a is heated, the core 11 is heated.
Will dissolve and evaporate, and the core-forming substance will be smoothly discharged to the outside through the pores on the surface of the porous coating layer 12a made of the flexible composition. Then, the intermediate body 12 from which the core-forming substance has been removed to the outside, that is, the coating layer 12a made of the flexible composition is fired to form a thin hollow metal article 13.

Therefore, according to the method according to the present embodiment as described above, it is possible to easily manufacture the thin hollow metal article 13 without requiring large-scale manufacturing equipment and skill. Also, in the present embodiment, the core 11 is used as a basic prototype of the inside of the product only in the molding process of the core 11 which requires the molding technique. Since it does not affect the natural shape of the product, it does not require strict precision in its molding technique, complete mechanization of the thin hollow metal article 13 and cost reduction are achieved, and the thin hollow metal article 13 is extremely It is possible to manufacture with high production efficiency.

[0025]

As described above, according to the method of the present invention, a core containing a metal or alloy powder and a binder is sprayed onto a core having a predetermined shape to spray a core-containing solution. By forming a coating film of the flexible composition on the surface and drying the coating film, it is easy to form a porous coating layer on the surface of the core with a uniform film thickness. Then, when the intermediate body composed of the core coated with the coating layer is heated, the core is dissolved and evaporated, and the core-forming substance is formed on the surface of the porous coating layer composed of the flexible composition. It will be smoothly discharged to the outside through the holes. And further, the intermediate obtained by removing the core-forming substance to the outside,
That is, a thin hollow metal article is formed by firing a coating layer made of a flexible composition.

Therefore, according to the method of the present invention, a thin hollow metal article can be easily manufactured by the above-mentioned method without requiring large-scale manufacturing equipment and skill. Further, the thin hollow metal article can be manufactured with extremely high production efficiency, and the cost of the product can be significantly reduced.

[Brief description of drawings]

FIG. 1 (a) is a view for explaining a core manufacturing process in a method for manufacturing a thin hollow metal article according to an embodiment of the present invention. FIG. 1 (b) is a diagram for explaining the step of forming a coating film in the method for manufacturing a thin hollow metal article of one embodiment of the present invention. FIG. 1 (c) is a sectional view of a thin hollow metal article completed in the method for manufacturing a thin hollow metal article according to an embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view of a conventional thin hollow metal article.

[Explanation of symbols]

 11 Intermediate 12 Covering film 13 Thin hollow metal article

Claims (1)

[Claims] 1. A flexible composition comprising a core having a desired shape formed by a core for producing a thin hollow metal article made of a brazing filler metal, and a metal or alloy powder and a binder on the surface of the core. By spraying a solution containing, to form a coating film composed of the flexible composition, by drying this to form an intermediate body having a porous coating layer formed on the surface of the core,
Then, the intermediate body is heat-treated to dissolve and evaporate the core, and then the flexible composition constituting the coating layer is fired, to produce a thin hollow metal article.