JPH0971802A - Production of metal product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a producing method of a metal product from a metal clay or a metal paste essentially comprising a metal powder and an org. binder as the source material so that a metal product having a cavity inside is easily produced with little deformation. SOLUTION: This method is to produce a metal product from a metal clay or a metal paste essentially comprising a metal powder and an org. binder as the source material. A core clay comprising a heat-resistant granular material which does not burn, sinter or deform at the sintering temp. of the above metal powder and a binder which burns at the sintering temp. is prepared and the core is coated with a resin coating layer. The metal clay is adhered or the metal paste is applied on the core to form a shaped body. The body is dried and heated to burn the coating layer on the core as well as to burn the org. binder in the shaped body and the core. Further the body is heated to sinter the metal powder of the shaped body. After the sintered body is cooled, the core is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a metal clay or metal paste containing metal powder and an organic binder as a main component as a raw material to easily produce a metal article having voids therein with a small amount of deformation. The present invention relates to a method of manufacturing a metal article that can be manufactured.

[0002]

2. Description of the Related Art Heretofore, there has been known a method for producing a metal article by shaping a metal clay composed of a metal powder and a binder into an arbitrary shape and sintering it. In particular, when manufacturing a metal article having a cavity inside, a core represented by wax or the like is used. That is, a core made of a substance that flows out or disappears due to fluidization, decomposition, combustion or the like when heated is used. The manufacturing process in this case is as follows:
First, the outer peripheral surface of a core molded into an appropriate shape is coated with metallic clay, shaped, and dried to obtain a shaped article. Next, by heating this, the core is removed by burning or the like, and the binder in the modeled object is removed. Further, this is heated and heated to sinter the metal powder in the shaped article. Then, it cools and the metal article which has a cavity inside is obtained.

[0003]

However, since the conventional core made of wax or the like flows out or disappears rapidly due to fluidization, decomposition, combustion, etc., during heating, the inside of the molded article does not sinter. There is a problem that it becomes hollow and loses the internal support function, and it collapses or deforms due to its own weight, especially when the molded object is thin, and a metal article cannot be obtained, or only a metal article different from the shape at the time of modeling can be obtained. It was
Further, when the core made of the wax or the like is burned, the whole core burns, but there is a problem that a large amount of smoke is generated at that stage and the working environment is deteriorated.

On the other hand, there is also known a method of manufacturing using a core made of sand or the like and a binder in casting. The core of this structure has the advantages that the volume is hardly reduced even if the binder is decomposed or burned, so that the internal support function continues until sintering, and sand and the like do not burn, so that less smoke is generated. However, when a core made of the above sand or the like is used in the production of a metal article using metal clay as a raw material, when the metal clay is attached to the outer peripheral surface of the core, the sand or the like on the surface of the core is metal. There is a problem that the work of removing sand and the like from the inside of the metal article obtained by sintering is extremely troublesome because it adheres to clay in a buried state. Further, since the surface of the core has a porous shape, the inner surface of the metal article has a satin finish, which may deteriorate the design of a product having a shape in which the inside can be recognized. In particular, when a crack is formed on the surface of the core, the metal clay bites into the crack, so that a metal article having an unintended protrusion on the inner surface can be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above, and is a method for producing a metal article using a metal clay or a metal paste containing a metal powder and an organic binder as a main material as raw materials. , A heat-resistant granular material that does not burn, sinter, or deform at the sintering temperature of the metal powder constituting the metal clay or metal paste, and an organic binder that decomposes or burns at the sintering temperature Mold the clay for the core into an arbitrary shape, and then coat it with a coating layer made of resin or wax to create a core, and either paste the metal clay on the outer peripheral surface of this core or apply a metal paste. Create a model,
After drying, the coating layer in the core is heated to decompose and burn, and the organic binder in the molded article and the core is decomposed and burned, and the temperature of the metal in the molded article is further increased by heating. The present invention relates to a method for producing a metal article, which comprises sintering a powder, cooling the core, and then removing the core.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The metal clay or metal paste used in the present invention is obtained by mainly mixing a metal powder and an organic binder, and adding a solvent thereto and thoroughly kneading the mixture. A metal powder is a metal (including a noble metal) that sinters when heated in air, a non-oxygen atmosphere, a reducing atmosphere, or the like,
It is a fine powder of metal oxides, ceramic materials and the like. Specifically, precious metal powders such as Au, Ag, Pt, and Pd, Ni, and C
o, Fe, Cu, Ti, Zn, Sn, Zr, Pb, W,
One or more selected from Mo, Ta, SiC and the like or alloys thereof, oxides and oxide alloy powders thereof, other ceramics, ceramic material powders and the like can be appropriately used. The organic binder is decomposed at the sintering temperature of the metal powder,
The material is not particularly limited as long as it burns, and any of thermoplastic resin, thermosetting resin, wax and the like can be used. Specifically, it is selected from water-soluble or oil-soluble resins such as polyacrylic acid ester, polymethacrylic acid ester, polyvinyl chloride, polyvinyl acetate, ABS, cellulose-based, starch, polyethylene, epoxy-based, polyester-based and various waxes. It is possible to appropriately use one or more of the above. Incidentally, a surfactant, a lubricant, an oil and the like can be appropriately blended according to various purposes. The solvent dissolves the organic binder,
Depending on the selected organic binder, a water-based (including water or alcohol-based solvent) or oil-based solvent can be appropriately used. The solvent and the organic binder are combined to form a binder.

The clay for cores used in the present invention comprises a heat-resistant granular material and an organic binder as main components, and a solvent (dispersion medium) is added thereto and sufficiently kneaded. The heat-resistant granular material is not particularly limited as long as it is a material that does not burn, sinter, or deform at the sintering temperature of the metal powder forming the metal clay or the metal paste.
Specifically, metal oxides such as alumina, zinc oxide, and titanium oxide, alumina silicates, kaolin, talc, sekiseki,
One or more selected from diatomaceous earth, silica, sand and the like can be appropriately used. The shape of the heat-resistant particulate material is preferably spherical, spheroidal, etc., with a smooth particle surface. Further, as the organic binder and solvent forming the core clay, the same organic binder and solvent forming the metal clay or metal paste can be used.

The present invention comprises the following steps. a. First, the core clay is formed into an arbitrary shape according to the shape of the cavity provided inside the metal article. b. Next, the surface of the formed molded clay for core is coated with a coating layer made of resin or wax to form a core. The resin or wax forming this coating layer is not particularly limited in its type and coating (coating) method as long as it has film-forming properties, and in particular, if it is a water-soluble resin or an aqueous emulsion type, its surface Even if the surface of the molded clay for core is porous due to the tension, it is difficult to enter the porous holes, which is preferable. Although not particularly limited, this coating layer is provided with a thickness of several to several hundreds μm. c. Further, a metal clay is attached or a metal paste is applied to the outer peripheral surface of the core thus formed to form a molded article. At that time, if the internal cavity of the metal article communicates with the outside, there is no problem, but when the internal cavity of the metal article is a closed space, that is, in the case of producing a hollow metal article, after sintering, It is necessary to provide an opening (communication with the outside) for collapsing and removing the core. d. Then, the formed object is dried and then heated. Usually, when the temperature is 200 ° C. or higher, the coating layer in the core is fluidized by thermal melting, thermal denaturation, etc. and flows out to the outside, or disappears by decomposition, combustion or the like. Further, the organic binder in the shaped article and the core also disappears due to decomposition, combustion, and the like. At this point, the volume of the core is reduced by the amount of the coating layer disappeared, and the volume of the core is also reduced by the disappearance of the organic binder. Therefore, the volume reduction of the core and the volume reduction of the metal sintered body offset each other, and as a result, the internal support function is maintained. e. Furthermore, the temperature is raised to sinter the metal powder in the shaped article. Even when the metal powder in the shaped article starts to sinter, the core maintains the internal supporting function as described above, and therefore the deformation of the metal article due to its own weight is extremely small. f. The finally sintered metal article is cooled and the core is taken out and removed. Since the organic binder has already disappeared in the core, it is substantially composed of only the heat-resistant granular material, so it easily disintegrates with a weak external force and easily dissociates the disassembled heat-resistant granular material to the outside. You can take it out.

In the method of manufacturing a metal article of the present invention having the above-mentioned constitutions, the internal supporting effect of the core continues until the time of sintering, so that a metal article with little thermal deformation can be obtained very easily. In addition, as described above, the core is reduced in volume by the amount of the coating layer disappeared, and the volume is also reduced by the disappearance of the organic binder, but a molded object formed of metal clay or metal paste is also available. Since the organic binder disappears and the metal powder shrinks due to sintering, the metal article is sintered while being supported by the inner core, and is not deformed by its own weight. In addition, since the core is mostly composed of heat-resistant granular material, the generation of smoke due to combustion during heating and sintering is small. Further, since the core has the coating layer formed on the surface thereof, the clay particles for core and the metal clay particles are not directly entangled with each other, and the heat-resistant granular material such as sand is embedded in the inner surface of the modeled object. Without sticking, the core can be easily removed (taken out) after sintering. On the contrary, the coating layer closes the porous holes of the core clay molded body, and even when a crack is formed on the surface of the core clay molded body, the coating layer closes the cracks. It is possible to obtain a highly designed metal article in which the metal paste does not bite into the pores or cracks and the inner surface is a smooth surface.

[0010]

EXAMPLE 14 g of methyl cellulose was dissolved in 70 g of water to prepare 84 g of a binder. 50 g of the binder and 50 g of alumina silicic acid particles (particle size: 10 to 300 μm) were kneaded to prepare a clay for core. 8 g of the binder and silver powder (particle size 1 to 100 μm, average particle size 10 to 20 μm) 1
It was kneaded with 00 g to prepare silver clay. First, the core clay was molded into an egg shape, dried, and then dip coated with an acrylic resin emulsion (solid content 30%), and dried to prepare a core having a coating layer formed on the surface. . Next, the silver clay extended into a plate shape having a thickness of 0.5 mm was attached in layers on the surface of the core and dried. Then, a φ5 mm hole (opening) is opened in a part of the modeled object,
In order to prevent falling, the modeling object was left standing in an electric furnace with the opening facing up in a dish containing river sand, and the temperature was raised from room temperature to 800 ° C for about 1
Heated over time. The temperature was continuously maintained at 800 ° C. for 30 minutes. Then take out the sintered metal article from the electric furnace,
After allowing to cool, the opening was faced down, and the alumina silicic acid particles were discharged and taken out. A small part of the alumina silicic acid particles adhered to and remained on the inner surface of the metal article, but could be easily peeled off and taken out by simply inserting a brush through the opening and touching it lightly. A metal article having almost no deformation and an extremely smooth inner surface was obtained.

[0011]

As described above, according to the method for producing a metal article of the present invention, a resin or wax is formed on the surface of a molded body of core clay containing a heat-resistant granular material and an organic binder as main components. Since the core provided with the coating layer is used, the internal supporting effect of the core continues until the time of sintering, and a metal article that is not thermally deformed can be obtained very easily. Also, the core is mostly composed of heat-resistant granular material,
Since the amount of smoke generated by combustion during sintering is small, the working environment can be improved. In addition, the core has a coating layer on its surface, and because heat-resistant granular substances such as sand do not adhere to the inner surface of the modeled object, it is easy to remove (remove) the core after sintering. Therefore, the workability can be improved. Further, the coating layer closes the porous pores of the core clay molded body, the coating layer also closes the cracks when the cracks are formed on the surface of the core clay molded body,
Since the metal clay or the metal paste does not bite into the porous holes or the cracks, it is possible to manufacture a metal article with a high design property in which the wall surface of the internal cavity is smooth.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shinichi Ishigaki 6-28-3 Minamimachi, Fuchu-shi, Tokyo Aida Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. A method for producing a metal article by using a metal clay or a metal paste containing a metal powder and an organic binder as a main material, the method comprising burning at a sintering temperature of a metal powder constituting the metal clay or the metal paste. , A heat-resistant granular material that does not cause sintering, deformation, etc., and a clay for cores whose main component is an organic binder that decomposes and burns at the above-mentioned sintering temperature, and is formed into a resin or wax. A core is created by coating with a coating layer, and metal clay is applied to the outer peripheral surface of this core, or a metal paste is applied to create a modeled object, which is dried and then heated to cover the core. Decomposes and burns the layer, decomposes and burns the organic binder in the molded article and the core, and further raises the temperature.
After heating to sinter the metal powder in the shaped object and cooling,
A method of manufacturing a metal article, comprising removing a core.