JPH0987708A - Method for joining porous sintered metal bodies - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a method for joining a porous sintered metal body capable of producing a joined body of porous sintered metal bodies of various shapes while preventing structural changes in the joined portion as much as possible. provide. A porous sintered metal body having a foamed structure obtained by preparing, molding, drying, and firing a foamable slurry containing metal powder is joined together. 2 The surfaces to be joined are brought into close contact with each other and sintered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining a porous sintered metal body having a foamed structure to obtain a joined body having a desired shape.

[0002]

2. Description of the Related Art The present inventors have developed a sponge-like porous sintered metal body having a foam structure obtained by preparing a foamable slurry containing metal powder, molding, drying and firing the foamable slurry. This porous sintered metal body is manufactured by sintering a dry molded body (green body) that is dried after molding.
During sintering, the whole shrinks by about 20%, and the shrinkage may cause cracking, so that it is difficult to obtain a flat plate having a large area.

Further, in the case of directly producing a thick one from a foamable slurry containing metal powder, the foaming process requires a considerably long time (for example, it takes about 4 hours to produce a product having a thickness of 3 cm). Is disadvantageous. Therefore, we manufacture a porous metal plate of a size that does not break during sintering,
There is a need for a technique for joining these to obtain a desired large area or thick one.

Conventionally, as a method of joining porous metal plates,
For example, the end portions of a porous metal sheet and another porous metal sheet are overlapped with each other with a thermoplastic resin interposed therebetween, heated to a temperature equal to or higher than the softening point of the thermoplastic resin, and the polymerized portion of the sheet is pressed and compressed. There is a method to do it (Japanese Patent Publication Sho 61-65)
No. 01).

Further, there is a method in which end faces to be joined of two foam metal members to be joined are butted to each other, and molten metal is poured into the butted portions to join the foam metal members to each other (Japanese Patent Publication No. 4-68071). Gazette).

[0006]

However, in the former method, the density of the foam metal is doubled at the joint portion, the porosity at the joint portion becomes small, and the pore structure of the obtained joint body is reduced. Is non-uniform. In addition, the latter method also has a problem that the density at the joint changes and the structure becomes nonuniform at the joint. In both of these methods, the structure of the joint is different from that of the other parts, and the deterioration of the performance at the joint is unavoidable.

The present invention has been made in view of the above circumstances, and it is possible to manufacture a joined body of porous sintered metal bodies having various shapes while preventing the structural change in the joined portion as much as possible. It is an object of the present invention to provide a method for joining bonded metal bodies.

[0008]

In order to achieve the above object, the present invention provides the following method for joining porous sintered metal bodies. (1) A method of joining porous sintered metal bodies having a foamed structure obtained by preparing, molding, drying, and firing a foamable slurry containing metal powder, which comprises: A method for joining a porous sintered metal body, characterized in that the surfaces to be joined are brought into close contact with each other and sintered.

The method for joining porous sintered metal bodies of the present invention is as follows.
Porous sintered metal bodies can be joined to each other without using an adhesive or the like, and the porous sintered metal body developed by the present inventors is utilized as a sintered body of metal powder. This is based on the finding that when the fine sintered metal bodies are fired while being brought into close contact with each other, the close contact surfaces can be sintered and joined.

Therefore, since the bonding can be performed without using an adhesive and without compression, the change in the physical properties such as the porosity of the bonded portion is as small as possible, and the obtained bonded body is uniform throughout. You can get things.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below. As described above, the method for joining the porous sintered metal bodies of the present invention includes the steps of preparing a porous slurry containing metal powder, molding, drying, and firing the porous sintered metal bodies having a foamed structure. It joins without an adhesive.

Here, the foamable slurry is prepared by, for example, metal powder, a water-soluble resin binder (binder), a foaming agent,
A slurry containing a surfactant, water, etc. is prepared. In this case, the type of metal powder is not limited, and for example, gold, silver,
All sinterable metals and alloys such as copper can be used. The particle size of the metal powder is such that the average particle size is 500 μm or less, and especially 0.
The range of 5 to 100 μm is preferable. Average particle size is 0.5μ
If it is smaller than m, the porosity may be small, while if the average particle size is larger than 500 μm, the strength of the resulting porous metal plate may be too weak. The blending amount of the metal powder in the slurry is preferably 5 to 80% (weight%, the same applies hereinafter), and particularly 30 to 80%.

The water-soluble resin binder functions as a binder to maintain the shape of the porous molded body when the slurry is dried. It also functions as a viscosity modifier for the slurry. Examples of the water-soluble resin binder include methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose ammonium, ethyl cellulose, polyvinyl alcohol and the like. The content of the water-soluble resin binder is preferably 0.5 to 20%, particularly preferably 2 to 10%. If the blending amount is less than 0.5%, the strength of the dry molded product may be weak, which may hinder handling.
If it is more than 20%, the viscosity may be too high and molding may be difficult.

The foaming agent is only required to be capable of generating gas to form bubbles, and a compound which decomposes at a constant temperature to generate gas and a volatile organic solvent can be selected. As a volatile organic solvent, for example, carbon number 5
8 hydrocarbon-based organic solvents. Such an organic solvent is a liquid at room temperature, is volatile, forms micelles in the slurry by the action of the surfactant, and vaporizes at room temperature or under heating to form fine bubbles. Carbon number 5
As the hydrocarbon-based organic solvent of ~ 8, for example, pentane,
Examples include neopentane, hexane, isohexane, isoheptane, benzene, octane, toluene and the like. The blending amount of the foaming agent is 0.05 to 10%, and particularly, 0.1.
The range of 5 to 5% is preferable. If the compounding amount is less than 0.05%, the generation of bubbles may be insufficient and the porosity may not increase, while if the compounding amount is more than 10%, the micelles will have a large diameter, and accordingly the molded body will be formed. Since the bubbles formed therein also have a large diameter, the strength of the obtained molded body and sintered body may decrease. Instead of using the foaming agent, the foamable slurry can be prepared by a method of vigorously mixing a gas such as air.

The surfactant has a function of stabilizing the foaming state and forming micelles of the foaming agent, and is alkylbenzene sulfonate, α-olefin sulfonate, alkyl sulfate ester salt, alkyl ether sulfate ester salt, alkane sulfone. Examples thereof include anionic surface active agents such as acid salts, nonionic surface active agents such as polyethylene glycol derivatives and polyhydric alcohol derivatives. The content of the surfactant is preferably 0.05 to 5%, particularly preferably 0.5 to 3%. If the amount is less than 0.05%, the formation of micelles may become unstable and it may be difficult to maintain fine bubbles, while if it is more than 5%, no further effect may be obtained. .

In addition to the above components, the foamable slurry according to the present invention may contain a plasticizer, a combustible agent for promoting pore formation, and the like. The plasticizer is for imparting plasticity to the molded product, and is a polyhydric alcohol such as ethylene glycol, polyethylene glycol, glycerin, sardine oil, rapeseed oil, oils and fats such as olive oil, ethers such as petroleum ether, diethyl phthalate, Examples thereof include diN-butyl phthalate, diethylhexyl phthalate, dioctyl phthalate, sorbitan monooleate, sorbitan trioleate, sorbitan palmitate and sorbitan stearate. The blending amount of the plasticizer is 0.
The range of 1 to 15%, especially 2 to 10% is preferable. If the content is less than 0.1%, the plasticizing effect may be insufficient, while if it is more than 15%, the strength of the molded product may be insufficient.

Further, the combustible agent for promoting pore formation is for facilitating the formation of pores by eliminating it during the firing of the molded dried body. Therefore, it is possible to select a powder or fibrous material that retains its shape and disappears during firing. Specifically, the powdery material has a particle size of about 0.1 to 200 μm and a length of 200 μm or less, preferably 30 to 12
A fibrous material of about 0 μm is preferable. Examples of the material include pulp, cotton, lint, corn starch, carboxymethyl cellulose, water-insoluble cellulose fiber, polyvinyl butyral resin, polyvinyl resin, acrylic resin, polyethylene resin and the like.

The foamable slurry according to the present invention can be obtained by mixing the above components. In this case, the mixing order is not limited, but it is preferable to mix the foaming agent lastly in order to limit foaming as much as possible during mixing. Incidentally, when the slurry foams, the viscosity of the slurry decreases and the moldability deteriorates, but the time from the addition of the foaming agent to the foaming of the slurry is the type of the foaming agent, the addition amount,
The temperature and the temperature can be controlled, and the temperature can be controlled appropriately, and molding can be performed while the fluidity is maintained. Also, the viscosity of the slurry is 20000c at 20 ° C.
Range of ps to 70,000 cps, especially 30,000 to 5
A range of 5000 cps is preferred. If the viscosity is lower than 20000 cps, the foamed structure may collapse during drying, whereas if the viscosity is higher than 70,000 cps, the viscosity may be too high and molding may be difficult.

Next, the foamable slurry thus prepared is molded into a plate shape. The molding method is not particularly limited,
The doctor blade method is suitable. An outline of the doctor blade device is shown in FIG. This apparatus includes a first roll 20 around which the carrier sheet 10 is wound, and a second roll 21 around which the carrier sheet 10 sent out from this roll is wound, and conveys between the first roll 20 and the second roll 21. The carrier sheet 10 functions as if it were a belt conveyor. Then, from the first roll 20 side to the second roll 2
A slurry reservoir 30, a foaming zone 40, and a drying zone 50 are sequentially provided on the first side. The slurry reservoir 30 has a rectangular box shape in contact with the upper surface of the carrier sheet near the first roll 20, and the wall of the slurry reservoir 30 on the carrier sheet advancing direction side is separated from the carrier sheet with an adjustable gap. A doctor blade 60 is provided, and the thickness of the molded body is adjusted by the gap between the doctor blade 60 and the carrier sheet 10. When the prepared foamable slurry S is put into the slurry reservoir 30 and the carrier sheet 10 is conveyed, the foamable slurry S is extruded from the gap between the doctor blade 60 and the carrier sheet 10 and formed into a plate having a predetermined thickness. This plate-shaped molded body 2A is molded into a body 2A.
Are carried to the carrier sheet 10 and moved to the next foaming zone 40.

As a doctor blade 60, FIG.
It is preferable to use a double-blade blade as shown in FIG. This removes large bubbles from the gap between the two blades,
According to the knowledge that large bubbles do not enter the plate-shaped molded body extruded from the gap between the first blade and the carrier sheet, and that the thickness of the molded body can be made uniform regardless of the height of the foamable slurry. . In this case, the carrier sheet 10
The gap G1 between the edge of the first blade B1 on the downstream side and the carrier sheet is preferably larger than the gap G2 between the edge of the second blade B2 and the carrier sheet.
In addition, the gap D between the first blade B1 and the second blade B2
Is preferably about 5 to 20 mm, for example. Further, the gap G between the second blade B2 and the carrier sheet 10
2 is preferably in the range of 0.2 to 2 mm.

The foaming zone is formed before drying the molded body.
This is a step of sufficiently completing foaming. If you dry immediately after molding, the surface of the molded product will be dried first, and the skin will be in a state where the foaming inside the molded product and the evaporation of water are prevented,
Foaming may be uneven. For this reason, it is preferable to provide a foaming step between the molding step and the drying step.

When foaming is performed simultaneously with foaming, cracks are likely to occur on the surface of the molded article. Therefore, it is preferable to perform foaming in a high-humidity atmosphere in order to prevent drying as much as possible during foaming. Specifically, for example, the slurry viscosity is 35
When it is 000 cps or more, the humidity is 65% or more, preferably 80% or more. If the humidity is lower than 65%, cracks may be formed on the surface of the molded body during drying. Foaming temperature is 15
The range of ˜65 ° C., particularly 28˜40 ° C. is preferable. If the foaming temperature is lower than 15 ° C., the foaming may take, for example, 2 hours or more. On the other hand, if the foaming temperature exceeds 65 ° C., the molded body may excessively foam and the molded body may collapse. Foaming time is usually 1
It is in the range of 0 to 45 minutes.

The foamed molded product 2B is conveyed to the drying zone 50 subsequent to the foaming zone 40, and is dried therein. The bubbles before drying are maintained by the presence of the water film. At this time, the slurry aggregates at the interface between the bubbles to form a skeleton structure (foam structure). If the water film breaks in this state, the slurry forming the skeleton will flow and the skeleton structure will collapse. A molded product having a foam structure can be obtained by drying so as not to cause such disintegration. Dry as quickly as possible so as not to cause collapse of the water film. Far infrared drying is suitable for this. Further, it is preferable to set the slurry composition such that the viscosity remarkably increases when the water in the slurry evaporates slightly.

As specific conditions for the drying step, for example, far-infrared rays may be used, and a heater temperature of 120 to 180 ° C., an ambient temperature of 40 to 80 ° C., and a drying time of 20 to 120 minutes may be adopted. As a result, a plate-shaped dry molded body 2C can be obtained. The thickness of the dry molded body 2C becomes 3 to 8 times the thickness of the normal molded body due to foaming. In the doctor blade device shown in FIG.
By carrying the carrier sheet 10 on which the sheet is placed while bending it in the lower right direction, a dried molded body (green body) 2
C and the carrier sheet 10 are separated. Subsequently, the dried molded body 2C is cut into predetermined lengths by the cutter 70 and sent to the next firing step. In the description, an example in which the molding step, the foaming step, and the drying step are continuously performed has been described, but it goes without saying that separate devices may be used for these steps.

The firing step is preferably a two-step process. The first step is called degreasing, and is a step of volatilizing organic substances (such as a binder), and the second step is a step of sintering metal powder. Also, these steps can be continuous. The degreasing step is performed under an atmosphere of, for example, a reducing gas such as hydrogen gas at 300 to 70.
It can be baked at a temperature of about 0 ° C. for 10 to 60 minutes. In addition, in the sintering process, an ammonia decomposition gas atmosphere,
It is preferable to perform firing at a temperature of about 800 to 1400 ° C. for 20 to 120 minutes under a reducing atmosphere such as hydrogen gas, or in a vacuum, and further in an atmosphere of air. Degreasing
Since the volume shrinks by about 20% during sintering, it is preferable to carry out degreasing and sintering by placing it on a floor plate with good sliding such as a graphite plate. After the sintering step, the thickness may be changed by skin pass rolling or the like.

The method for joining porous sintered metal bodies of the present invention is as follows.
The porous sintered metal bodies thus obtained are joined together. As described above, the joining method is that the surfaces to be joined of the porous sintered metal body are brought into close contact with each other, and in that state, they are fired again to sinter the closely contacted surfaces to join them.

The joining mode of the porous sintered metal bodies is, for example, as shown in FIG. 1, by joining the end faces of the porous sintered metal plate 2 to each other to form the joined body 1a of the large area porous sintered metal bodies. Method of obtaining, as shown in FIG. 2, two or more porous sintered metal plates 2
To obtain a thick bonded body 1b of porous sintered metal bodies, or, as shown in FIG. 3, use a large number of porous sintered metal plates 2 and connect these end faces to each other. There is a method of obtaining a bonded body 1c of a large-sized porous sintered metal body with a large thickness by closely adhering to increase the area and by laminating and bonding a plurality of them. It is preferable that the porous sintered metal plate to be joined is cut into a predetermined shape in advance so that the end faces can be easily attached. Further, the porous sintered metal bodies are not the same, but those having different porosities, types of metal powders, etc. may be joined together. The sintering conditions can be the same as the sintering conditions at the time of manufacturing the porous sintered metal body.

The obtained joined body of porous sintered metal bodies can be made larger in area and thicker, and porous metal bodies having different properties are combined to have different porosities in the thickness direction, for example. Therefore, it can be used for various purposes. For example, it can be applied to filters, antibacterial filters, precious metal products, catalysts, base materials for composite materials, and the like. [Example] Three kinds of foaming slurries having different kinds of metal powders were prepared with the components shown in Table 1 and the blending amount (% by weight).

[0029]

[Table 1] The prepared foamable slurry was molded into a thickness of 1 mm by using a doctor blade method, and then was held in a thermo-hygrostat having a humidity of 90% and a temperature of 40 ° C. for 15 minutes for foaming. afterwards,
A green body was produced by holding in an air circulation type far-infrared dryer having a heater temperature of 160 ° C. and an ambient temperature of 40 ° C. for 1 hour and drying. At this time, the green body swelled in the above-mentioned foaming process, and its thickness was about 5 times the molding thickness. The obtained green body was cut into 20 cm square pieces, placed on a substrate obtained by spraying boron nitride (BN) on a graphite plate, and held in air at a temperature of 380 ° C. for 2 hours for degreasing (debinding). Then, sintering was performed under the sintering conditions shown in Table 2 to obtain a porous sintered metal plate.

Next, a large number of the obtained porous sintered metal plates were prepared and, as shown in FIG. 3, their end faces were brought into close contact with each other to have a large area, and two layers were stacked. Then, this is fired again under the same conditions as those shown in Table 2,
The porous sintered metal plates were sintered and bonded.

The pore size of the joined portion and the whole of the joined body of the obtained porous sintered metal bodies was measured. The results are also shown in Table 2.

[0032]

[Table 2] The strength at the joint of the obtained porous sintered metal body was sufficient.

[0033]

According to the method for joining porous sintered metal bodies of the present invention, it is possible to easily obtain joined bodies of porous sintered metal bodies having various shapes.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating one embodiment of a joining method of the present invention.

FIG. 2 is a schematic cross-sectional view showing another aspect of the joining method of the present invention.

FIG. 3 is a schematic cross-sectional view showing still another aspect of the joining method of the present invention.

FIG. 4 is a sectional view showing an outline of a doctor blade device.

FIG. 5 is a schematic sectional view showing a doctor blade having two blades.

[Explanation of symbols]

 2 Porous Sintered Body 2'Porous Sintered Body after Joining 1a, 1b, 1c Joined Body

Claims (1)

[Claims] 1. A method of joining porous sintered metal bodies having a foamed structure obtained by preparing, molding, drying and firing a foamable slurry containing a metal powder, the porous sintered metal body comprising: A method for joining a porous sintered metal body, comprising the steps of bringing the surfaces to be joined together into close contact with each other and sintering.