JPH0889731A - Filter made of metal powder and its production - Google Patents

Abstract

PURPOSE: To produce a multilayered metal powder filter having a specified filtration degree or lower and a constant permeation amt. by alternately laminat ing layers (A) having specified properties and layers (B) which are more coarse than the layers (A) to form two or more layers. CONSTITUTION: This filter is a sintered multilayered metal powder filter and consists of two or more layers of layers (A) and layers (B) alternately laminated. (a) The layer (A) shows such properties that (i) pores of <=5μm diameter are present in >=1×10<3> number per 1mm<2> in any cross section of the layer and (ii) pores penetrate the cross section of the filter. (b) The layer (B) shows such properties that (i) pores having larger diameter than the pores 10 the layer (A) are present by >=1×10<3> number per 1mm<2> in any cross section and (ii) pores penetrate the cross section of the filter. (C) The porosity of the filter is 40 to 70%. Thereby, the obtd. multilayered metal powder filter has about <1μm filtration degree and about >=0.2l/min/cm<2> permeation of nitrogen gas under about 0.2kgf/cm<2> pressure difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a filtration filter used in various industrial fields, for example, water treatment, a liquid such as a refrigerant in a refrigerator, or a gas having a filtration degree of 1 μm or less for filtering gas. The present invention relates to a metal powder filter and a method for manufacturing the same. Here, for example, a filtration degree of 1 μm or less means that STADE having a uniform particle size in an aqueous ethanol solution.
It refers to a filter in which X standard particles (true spherical polyester latex particles) are dispersed and the diameter of the particles passed through the filter at a differential pressure of about 0.1 kgf / cm ² is 1 μm or less.

[0002]

2. Description of the Related Art It is well known that, in a refrigerator or a refrigerator, a so-called refrigerant is compressed and vaporized to be adiabatically expanded to obtain a cooling effect. Since the pipe in which the refrigerant is circulated has a small inner diameter, dust remaining in the pipe or an adhering substance in the pipe when the pipe is assembled clogs the pipe in which the refrigerant is circulated. Therefore, it becomes necessary to filter various dusts and the like generated in the refrigerant pipe.

It is said that the filtration degree of such a filter is preferably 1 μm or less. However, since a filter made of metal powder having a filtration degree of 1 μm or less has not been manufactured, a filter made of synthetic resin such as ceramic or fluororesin has been used. However, ceramic has poor toughness,
There is a risk of damage during use, a filter made of a synthetic resin such as a fluororesin is also easily damaged, and a jig for fixing the filter is required, which is extremely inconvenient to handle.

Therefore, there is a demand for a metal powder filter which can be welded during installation and has a toughness and a filtration degree of 1 μm or less. However, as described below, such a filter made of metal powder could not be manufactured.

Conventionally, a method for producing a filter made of metal powder, which is produced by using metal powder, is a powder compacting method in which metal powder is compressed and molded, or a powder filling method in which a metal powder is simply filled in a mold. The method of sintering these to manufacture a metal filter is adopted.

A conventional method for manufacturing a metal powder filter will be described with reference to FIG. In the filling method in the conventional method for producing a filter made of metal powder, for example, spherical metal powder produced by a gas atomization method such as bronze and stainless steel is first sieved to a predetermined particle size, and a powder of 60 to 900 μm, for example, is obtained. Then, this is filled in a container having a predetermined shape and sintered.

On the other hand, in the pressure molding method, the bronze,
Irregular shaped metal powder such as stainless steel manufactured by water atomization method is sieved to 40 to 500 μm powder, or spherical powder is mixed with binder such as paraffin wax and compression molded by pressure. The prepared product is filled in a box-shaped container and is sintered. After sintering, these sintered bodies were taken out from the box, processed into a predetermined shape as required, and then pickled, or subjected to an appropriate surface treatment to manufacture a metal filter.

In such a manufacturing method, even if the powder having the smallest particle diameter was used, the average pore diameter was about 20 μm, and it was not possible to manufacture a filter having a filtration degree of 1 μm. On the other hand, when a metal powder having a spherical shape of several μm to several tens of μm obtained by an ultrahigh pressure water atomizing method or a carbonyl method is used and a filter is manufactured by a powder compacting method, the filtration degree is 1 μm or less, At that time, the pressure drop was extremely large and could not be practically used.

In the pressure molding method, the metal particles are deformed and compressed in the powder compacting process, the porosity is lowered, and the pores having a filtering action are variously bent in the thickness direction of the filter. The passage resistance of the passing liquid or gas body becomes large, and the pressure drop before and after the filter is extremely large.

Further, in the so-called powder filling method, if these powders are simply filled and sintered, they are agglomerated to some extent nonuniformly due to the adhesive force such as intermolecular force between particles and the interfacial tension, and uniform filling is achieved. If it is not possible, for example, bridging occurs, and the particles are not uniformly filled, stable production cannot be performed and a filter having a certain degree of filtration cannot be obtained. Therefore, for applications with filtration of 1 μm or less, for example, ceramic,
A filter made of a synthetic resin such as a fluororesin has been used.

On the other hand, a method for producing a microfiltration ceramic filter intended for a filtration degree of 1 μm or less is described in, for example, JP-A-64-56111 and JP-A-64-583.
Although disclosed in Japanese Laid-Open Patent Publication No. 05, etc., no technology related to a practical method for producing a filter made of a metal powder having a filtration degree of 1 μm or less has been disclosed.

Japanese Unexamined Patent Publication (Kokai) No. 5-195110 discloses a method for producing a filter having an average pore diameter of about 1 μm by compacting and sintering a metal oxide powder and reducing the powder. . However, this method has a problem in terms of cost because it involves complicated steps such as sintering in the air for a long time and then reducing the metal oxide using a reducing gas such as hydrogen gas. Further, for example, in the case of filtering the above-mentioned refrigerant, nitrogen gas is used, and a differential pressure of 0.2 kgf / cm ² is 1.5 l / mi.
Although air permeability of n / cm ² or more is required, the filter disclosed in the above publication does not satisfy such performance.

Further, JP-A-3-137913 discloses a method for producing a metal porous filter by mixing metal powder and acrylic fine particles, kneading with a wax binder, molding and sintering. However, a sintered body having an apparent porosity of 20 to 37% and a maximum pore diameter of 1 to 2.5 μm was obtained. However, it does not disclose the important air permeability in the filter.

[0014]

In the present invention, a commercially available metal powder having a particle size of about 10 μm or less is used,
The object is a metal powder filter having a filtration degree of 1 μm or less, and a method for producing the same. The filtration degree is 1 μm
Even if it is below, a certain amount of passage is required. The passing amount changes depending on the pressure difference before and after the filter. Desired throughput, the pressure difference with nitrogen gas at 0.2 kgf / cm ² or less, about 0.2 l / min / cm ² or more, preferably 0.5l / min / cm ² or more, more preferably 1.5
It is 1 / min / cm ² or more. A filter having such performance is an object of the present invention.

[0015]

In the present invention, a metal powder having a particle size of 10 μm or less is dispersed in a slurry liquid,
Pour this onto, for example, a ceramic substrate or a pre-manufactured metal filter, precipitate the metal powder on it, create a membrane filter element, and dry and sinter it to create aeration. High filtration rate 1 μm
The following metal filters were successfully manufactured.

(1) The invention of claim 1 is a metal powder filter having the following structure. (A) A sintered metal powder filter having pores with an equivalent diameter of 5 μm or less on any cross-sectional surface.
1 × 10 ³ or more per mm ² exists, (b) the pores penetrate the longitudinal section of the filter, and (c) the porosity of the filter is 40 to 70%. (2) In the invention of claim 2, the following A layer and B layer are alternately arranged to be 2
It is a filter made of metal powder in which more than one layer is laminated. (A) The A layer has (i) 1 × 10 ³ or more pores having an equivalent diameter of 1 μm or less per 1 mm ² on the surface of any cross section thereof, and (ii) the pores are longitudinally cut through the filter. (B) the B layer has (i) pores having a diameter larger than that of the A layer on the surface of any of its cross sections (1 × 10 ³ per mm ^2).
And (ii) the pores penetrate the longitudinal section of the filter, and (c) the porosity of the filter is 40 to 70%. (3) In the invention of claim 3, the metal of the metal powder filter is any one of Ni, Co, Ti, Cr, W, Mo, and an alloy containing one or more of them. The metal powder filter described in any one of 1. (4) The invention of claim 4 is a method for producing a metal powder filter, which comprises the following steps. (A) a step of preparing a powder made of a metal powder having a predetermined particle diameter, and (b) a step of adding the metal powder made of a metal powder to a slurry liquid containing at least a dispersion medium and a binder to disperse the slurry. (C) a step of precipitating the metal powder dispersed in the slurry on the substrate and then drying the slurry liquid; and (d) a step of sintering the dried metal powder. (5) The invention of claim 5 is a method for producing a filter made of metal powder, which comprises the following steps. (A) a step of preparing a pre-manufactured single-layer or multi-layer metal powder filter (first filter); and (b) a slurry containing at least a dispersion medium and a binder of metal powder powder having a predetermined particle size. A step of adding to the liquid to disperse the slurry to form a slurry; (c) a step of precipitating and drying the slurry on the first filter; and (d) a baking of the first filter in which the slurry is precipitating and drying. The process of binding. (6) The invention according to claim 6 is a method for producing a filter made of metal powder, wherein the predetermined particle size is about 10 μm or less in Fisher subsieve particle size. (7) The invention of claim 7 is characterized in that the step of settling and drying the slurry is performed on the air-permeable substrate or on the surface opposite to the surface where the slurry is settled on the metal powder filter consisting of one or more layers. The method for producing a metal powder filter according to any one of claims 4 to 6, which is a step of causing a pressure difference between them and sucking air from the opposite surface to precipitate and dry the slurry.

[0017]

The metal filter can generally filter particles having a diameter of about 1/5 of the pore diameter. This is because the particles form crosslinks in the pores during filtration, so that the particles that flow in later are blocked at this portion. Therefore, in order to achieve the filtration degree of 1 μm or less, which is the object of the present invention, the maximum pore diameter must be 5 μm or less. Further, in the case of spherical powder, the relationship between the pore diameter and the powder diameter is about 1: 5. Therefore, when the pore diameter is 5 μm or less, the diameter of the powder needs to be 25 μm or less.

However, the so-called absolute filtration rate is required in the semiconductor industry. In this case, when the filtration degree is 1 μm or less, the maximum pore diameter needs to be 1 μm or less.
However, from the viewpoint of manufacturing cost, it is desirable to use a commercially available powder that is mass-produced, but as the commercially available metal powder, for example, a powder of about several μm produced by the carbonyl method is used. Powders of 1 μm or less are expensive because they are not mass produced. Therefore, if an inexpensive commercially available powder is used, the limit of the absolute filtration degree is about 0.4 μm.

However, in the present invention, since the production method described below is adopted, the filtration degree is 1 μm even if a commercially available powder is used.
Filters of m or less can be manufactured with a single layer structure. When an absolute filtration degree of 0.4 μm or less is required, this can be achieved by forming the filter into a multilayer structure.

The structure of the multilayer metal powder filter according to the present invention will be described with reference to FIG. FIG. 1 shows various embodiments of single-layer and multilayer filters according to the present invention. The hatched portion A is a layer having pores having an equivalent diameter of the pores (the diameter of a circle having the same area is referred to because the cross section of the pores is not necessarily circular) is 5 μm or less, and the other layer B is layer A. Is a layer having pores having a diameter larger than that of This is because the filterability of the filter is determined by the diameter of the pores of the layer A, and if the equivalent diameter of the pores of this layer is 5 μm or less, the filterability is 1 μm or less as described above.

Since the pores of the layer A have a small diameter, increasing the thickness thereof increases the ventilation resistance. Therefore, it is desirable that the thickness thereof is thin. On the other hand, if it is thin, its mechanical strength becomes small, which is a practical problem. Therefore, for example, the thickness of the A layer is 0.05 to 0.5 mm, and the thickness of the B layer is 0.5 to 5 mm.
When laminated with a thickness of about mm, it is possible to suppress an increase in passage resistance while increasing the mechanical strength of the filter. The mode of lamination is shown in FIGS. 1 (a) to 1 (e).

On the other hand, as described above, the filter is required to pass a certain amount of gas or liquid at a predetermined differential pressure. As described above, the desired flow rate is about 0.2 l when the pressure difference is 0.2 kgf / cm ² or less with nitrogen gas.
/ Min / cm ² or more, preferably 0.5 l / min /
cm ² or more, more preferably 1.5 l / min / cm ²
That is all. To secure this minimum passage amount, A
It has been experimentally confirmed that it is necessary that 1 × 10 ³ or more pores having an equivalent diameter of 1 μm or less are present per mm ^{2 on} any cross-sectional surface of the layer. It is necessary that the pores are straight or penetrate even if bent.

Furthermore, in the layer B, there are 1 × 10 ³ or more pores having a diameter larger than that of the layer A per mm ² on the surface of any cross section, and the pores penetrate the longitudinal section of the filter. It is necessary to have The function of the layer B is to remove the large particles in advance, prevent the pores of the layer A from clogging, and have the above-described structure in order to maintain the mechanical strength of the filter as described above. Also, as shown in FIG.
As shown in (d) and (e), the plurality of A layers are provided for the purpose of enhancing the reliability of microfiltration.

Next, a method of manufacturing the filter according to the present invention will be described. The steps of the manufacturing method in the present invention are shown in FIG. The steps of the manufacturing method according to the present invention will be described with reference to FIG. In the following description, when the particle diameter of powder is referred to, it means Fischer sub-sieve particle diameter (average particle diameter). The Fischer sub-sieve particle size means a particle size (μm) measured by a Fischer sub-sieve cider. In the present invention, the powder used as the material for the metal filter is 25 μm.
The following is desirable, and more desirably 10 μm or less.

This is because if the particle size of this metal powder is too large, the diameter of the pores penetrating the inside of the filter after sintering will not be 1 μm or less. The diameter of the pores is JIS K
D = 4γ cos θ / Δ, where ΔP is the pressure at the bubble point using the filter disk bubble point tester specified in 3832 (1990).
Refers to the diameter calculated by P. Here, d: diameter of pores, γ: surface tension of liquid θ: contact angle of solid-liquid, ΔP: pressure difference.

The metal constituting the metal powder may be any metal as long as it has a particle size of 25 μm or less. However, the corrosion resistance, durability, and
Or considering heat resistance, Ni, Co, Ti, C
Usually commercially available powders such as r, W and Mo are desirable, and further, alloy powders containing one or more of these are desirable. However, any metal powder may be used depending on the application.

Since these powders are usually sold in a predetermined container or the like, these powders are first crushed by using, for example, a ball mill, and the powders are dispersed into particles as much as possible. Next, this metal powder is mixed with a previously prepared slurry liquid to prepare a slurry of the metal powder.

The slurry liquid is prepared by the following procedure. The method of preparing the slurry is shown in FIG.
For example, pure water, acetone, alcohol and the like, if necessary, ammonium carboxylate as a dispersant are mixed and stirred, and a binder such as polyvinyl alcohol or polyacrylic acid is added, and the mixture is added at 60 ° C to 70 ° C.
Heat and stir at ℃ for about 1 hour.

After that, metal powder is added to this and further stirred, and then ultrasonic waves are applied to sufficiently disperse the metal powder. After that, deaeration is performed under reduced pressure and stirring is performed. The above is one example of the method for forming the slurry. An example of blending the slurry is as follows. Pure water 101 g, dispersant 2.8 g, polyvinyl alcohol 11 g, and metal powder 200 g are added thereto.

Returning to FIG. 2, this slurry is precipitated on a ceramic substrate having a predetermined shape, for example, a substrate of Al ₂ O ₃ . The substrate has, for example, a cylindrical shape with a shallow bottom (diameter is, for example, 50 mm). As a mode of precipitation, there is a method of immersing the substrate in a slurry, pulling it up, and then drying, a method of dropping the slurry on the substrate and drying it, and a method of applying the slurry on the substrate.

Al₂O₃Ceramic substrates such as
It is breathable, has a smaller thermal expansion than metal powder, and is sintered.
It is necessary that it does not react with
It need not be ceramic. For example, Al₂O₃, S
i₃N_Four, ΑSiC, SiO ₂, Β sialon etc. used
it can. Whichever method is used,
For example, the metal powder described above is slurried to a thickness of 1-2 mm.
After that, the slurry liquid is dried.

For example, in the case of a cylindrical filter, an air-permeable Al ₂ O ₃ cylinder is prepared, and the slurry is immersed in the inner surface of the cylinder, sucked from the outer surface of the cylinder, pulled up, and dried. it can. The metal powder filter is manufactured by sintering the slurry liquid after it is sufficiently dried. It is desirable to set the sintering temperature and atmosphere according to the properties of the metal powder.
For example, when the metal powder is carbonyl nickel, it is sintered at 850 to 1100 ° C. for 30 minutes in a reducing atmosphere such as hydrogen gas.

Since the sintered metal powder is not compression-molded, it is homogeneous without deformation. In addition, since it is in contact with the substrate during sintering, shrinkage is suppressed, a large porosity and a filter having pores penetrating in the filtering direction are obtained. After sintering, there is a difference in thermal contraction with the substrate, so that it is easily separated. The above is the method for manufacturing the metal powder filter having a single layer. This single layer has a porosity of 40.
-70%, the pore diameter is 0.1-5 μm, and the pore diameter is about ⅕ of the particle diameter like the conventional spherical powder, but the porosity is higher and the ventilation is higher than that of the conventional manufacturing method. A filter with excellent properties can be obtained. In the case of producing a metal powder filter having a composite layer, the following steps can be adopted.

The slurry prepared by the above-mentioned method is precipitated and dried on the first layer prepared by the above-mentioned method or a pre-made filter such as a conventional stainless steel powder filter having a filtration degree of 1 μm or more. On this occasion,
From the viewpoint of productivity, it is more desirable to suck air from the lower side of the filter covered with the slurry and suck a liquid component to dry the filter.

The method of intake and drying is shown in FIG. After drying, the metal powder filter formed in at least two layers is sintered. In the case of multiple processes, the steps of intake, drying and sintering can be repeated a plurality of times to produce a metal powder filter having two or more layers.

In this case, it is necessary that at least one layer is a layer obtained by dispersing the one layer by the above-mentioned slurry, drying and sintering the layer. The other layers may be the same as in the present invention, or may be a metal powder filter formed by a conventional sintering method using a powder having a larger particle size than the powder used in the slurry. . As the metal filter manufactured by the conventional sintering method, for example, one obtained by sintering stainless steel (SUS) powder can be used.

The structure of the filter thus manufactured is as already shown in FIG. When such a manufacturing method is adopted, the layer B is a coarse filter, but the layer (A layer) formed at the boundary between this layer and the next layer B is a filter layer having fine pores. Since the metal powder in the slurry forming the next B layer penetrates into the pores exposed on the surface of the previous B layer and becomes a homogeneous and more filled state, the pores have a small diameter and are thin. This is because a layer is formed. The performance of the filter is determined by the diameter of the fine pores in this boundary layer.

In the case of a ceramic filter, it is usually shown in FIG.
The structure shown in (b) is general. A method of forming a second thin layer as thin as possible by a doctor blade method or the like on a preformed-sintered first layer and forming a slurry based on a ceramic powder having a particle size smaller than that of the first layer, and sintering the slurry. Is. In the case of ceramics, even if the second layer is sintered, there is almost no shrinkage, so the second layer becomes the A layer as it is.

In the present invention, since the metal powder is used, the sintering progresses during the sintering and generally causes a large shrinkage. However, in the second layer formed by the slurry, the portion in contact with the surface of the first layer and the portion penetrating into the pores exposed in the surface of the first layer are the same as those in the ceramic substrate in the production of the single layer filter described above. Since the contraction is constrained, the part on the opposite side does not contract and becomes the same rough layer as the first layer, resulting in the structure shown in FIG. 1D.

Moreover, A formed on the boundary between the first layer and the second layer
The layer has a restraining force at the time of contraction and when the slurry is vacuum sucked, the surface of the first layer and the powder in the slurry come into close contact with each other, so that the sintering is activated and the porosity becomes low, but it is very small. A thin layer with a pore size is formed. Therefore, even if the same particle size is used, it is possible to form pores having a diameter much smaller than that of ceramics. Generally, in the case of ceramics, the pore diameter formed is about 1/5 of the particle diameter, but when the method of the present invention is used, the pore diameter formed is
The particle size is about 1/10 to 1/50.

In the case of this method, the thickness of the layer A is determined by the specific gravity of the powder used, the viscosity of the slurry, and the suction force when vacuum suction is performed. Further, in the case of the structure of FIG. 1 (d), since the rough B layer is essentially unnecessary, the viscosity of the slurry is suppressed, or the second layer is formed by the doctor blade method or the like.
It is possible to use only layers (FIG. 1 (b)).

FIG. 6 shows carbonyl nickel powder (INC
Type 123) manufactured by O company is used to precipitate, dry, and sinter the slurry on the alumina substrate by the method described above to form the first layer, and further vacuum suction of the slurry, precipitation, and drying are performed.
3 is a photograph of a cross section of a filter that is made by sintering (second layer) and repeating the same process once more (third layer). As is clear from the photograph, a dense A layer is formed between the first layer and the second layer and between the second layer and the third layer.

As described above, in the present invention,
A large amount of commercially available powder such as carbonyl powder can be used, a molding press is not necessary, and since it can be sintered for a short time, for example, a continuous furnace such as a mesh belt furnace can be used. Inexpensive mass production is possible.

[0044]

Example 1 Carbonyl nickel powder (INC having an average particle size of 3 to 7 μm)
TYPE123 manufactured by O. was used to prepare a slurry by the method described above, and a 50 mm square high-purity alumina substrate was immersed in the slurry, pulled up, and dried in the atmosphere at 25 ° C. for 24 hours. Next, this substrate and the nickel metal powder adhered to the substrate were sintered at 950 ° C. for 30 minutes in a hydrogen stream. The manufactured Ni filter was about 50 mm square and had a thickness of about 0.8 mm.

Example 2 Using the nickel metal filter manufactured by the above method as a substrate, the slurry prepared by the above method was further deposited on one surface of the substrate and degassed from below to remove the slurry liquid. After that, the slurry forming the second layer was dried in the atmosphere at 25 ° C. for 24 hours, and then sintered in a hydrogen stream at 900 ° C. for 30 minutes. As a result, a metal powder filter having a total thickness of about 1.0 mm could be manufactured.

Example 3 The filter produced according to the example was further precipitated into the above-mentioned slurry and sintered to obtain a filter having a thickness of 1.3 mm.

Example 4 In exactly the same manner as in Examples 2 and 3, the pressure-sintered stainless steel powder filter produced by the conventional method was used as the first layer metal filter. A metal filter composed of two layers was produced. This stainless steel powder filter uses powder having an average particle size of 30 μm (according to the high pressure water atomizing method) at a pressure of 1.2 ton / c.
It was molded by m ² and sintered at 1100 ° C. for 30 minutes, and its thickness was 0.5 mm.

Table 1 shows the results of examining the performance of the metal filters produced by the above method. In Table 1, the test piece was processed into a shape of 47 mm, and the evaluation was performed as follows. Measurement of maximum pore diameter: It is a method specified in JIS-K-3832. Air permeability: The differential pressure before and after the filter and the gas passage amount when a nitrogen gas having an original pressure of 0.5 kgf / cm ² was passed were measured with a mercury column and a flow meter, respectively. Filtration degree: True spherical polystyrene latex particles (STADEX-SC-021S) having a diameter of 0.208 μm were mixed in 10 ml of ethyl alcohol, and the resulting liquid had a differential pressure of 0.1 k.
After passing through the filter at about gf / cm ² , the number of latex particles contained in the filtrate was measured with an auto counter. Whether or not 100% filtration was performed was confirmed by observing with a SEM after drying the filtrate.

[0049]

[Table 1]

[0050]

The metal powder filter manufactured by the method of the present invention can be manufactured as a metal powder filter having a filtration degree of 1 μm or less, as can be confirmed from the result of the filtration test. Can be used in place of conventional synthetic resin filters. Compared with a filter made of synthetic resin, it is a metal powder filter which has excellent heat resistance and durability, is easy to handle, and can be welded to the place of use, and is excellent in performance and use. Its applications include filtration of refrigerant in refrigerators, purification of various polymers and monomers, water treatment of wastewater,
It can be widely used for refining gases and liquids for the semiconductor industry.

[Brief description of drawings]

FIG. 1 is a diagram showing various configurations of a metal powder filter according to the present invention.

FIG. 2 is a diagram showing an outline of a manufacturing process of a metal powder filter according to the present invention.

FIG. 3 is a schematic diagram showing a method for producing a slurry used in the manufacturing process of the present invention.

FIG. 4 is a diagram showing a suction method in the method for manufacturing the composite metal powder filter according to the present invention.

FIG. 5 is a schematic view showing a manufacturing process of a conventional metal sintered body.

FIG. 6 is a micrograph of a cross section of a filter according to the present invention.

Claims (7)

[Claims] 1. A metal powder filter having the following structure. (A) A sintered metal powder filter having pores with an equivalent diameter of 5 μm or less on any cross-sectional surface.
There are 1 × 10 ³ or more per mm ² , (b) the pores penetrate the longitudinal section of the filter, and (c) the porosity of the filter is 40 to 70%. 2. A metal powder filter in which two or more layers A and B below are alternately laminated. (A) The A layer has (i) 1 × 10 ³ or more pores having an equivalent diameter of 5 μm or less per 1 mm ² on the surface of any cross section thereof, and (ii) the pores are longitudinally cut through the filter. (B) the B layer has (i) pores having a diameter larger than that of the A layer on the surface of any of its cross sections (1 × 10 ³ per mm ^2).
And (ii) the pores penetrate the longitudinal section of the filter, and (c) the porosity of the filter is 40 to 70%. 3. The metal of the metal powder filter is N
The metal powder filter according to any one of claims 1 and 2, which is one of i, Co, Ti, Cr, W, Mo, and an alloy containing one or more of these. 4. A method for producing a filter made of metal powder, which comprises the following steps. (A) a step of preparing a metal powder having a predetermined particle size,
(B) adding the metal powder powder to a slurry liquid containing at least a dispersion medium and a binder to prepare a dispersed slurry, and (c) precipitating the metal powder dispersed in the slurry on a substrate. And then drying the slurry liquid, and (d) sintering the dried metal powder. 5. A method for producing a metal powder filter, which comprises the following steps. (A) a step of preparing a pre-manufactured single-layer or multi-layer metal powder filter (first filter);
(B) a step of adding a metal powder having a predetermined particle diameter to a slurry liquid containing at least a dispersion medium and a binder to disperse the powder to form a slurry; (c) the first slurry.
A step of settling / drying on a filter, and (d) a step of sintering the first filter on which the slurry is settling / drying. 6. The method for producing a metal powder filter according to claim 4, wherein the predetermined particle size is a Fischer sub-sieve particle size of about 10 μm or less. 7. The step of precipitating / drying the slurry comprises applying a pressure difference between the surface on which the slurry is precipitated and the surface opposite to the surface of the air-permeable substrate or a filter made of metal powder composed of one or more layers. 5. A step of causing the slurry to be aspirated from the opposite surface to precipitate and dry the slurry.
7. The method for producing the metal powder filter according to any one of items 1 to 6.