JPH1046209A - Production of porous aluminum green compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously producing a porous Al green compact having a high porosity and widely applicable as a filter, sound absorbing material, catalyst carrier, nucleate boiling material, adsorbent, heat exchanger, etc., from the powder of Al or its alloy. SOLUTION: A raw powder 1 is obtained by mixing an aluminum powder and an aluminum alloy powder. The aluminum alloy powder contains a eutectoid component forming a eutectic composition having a lower m.p. than aluminum by the reaction with aluminum. This raw powder 1 is compacted at >=60g/cm<2> , kept at 600-660 deg.C for at least 1min in a nonoxidizing atmosphere, heated 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 manufacturing a porous aluminum sintered material, and more particularly, to a method for manufacturing a porous aluminum sintered body.
Simply called Al. ) Or an alloy powder thereof as a raw material, and relates to a production method capable of continuously producing a porous Al sintered material having a large ratio of pores or voids in a unit volume (hereinafter, simply referred to as porosity) with high efficiency. .

[0002]

2. Description of the Related Art Metals, ceramics, synthetic resins and other porous materials are used in various industrial fields. For example, it is widely used as a filter, a sound absorbing material, a catalyst carrier, a nucleate boiling material, an adsorbent, a heat exchanger, and the like, and its use range is extremely wide.

[0003] Porous materials having such a wide range of use are classified into ceramics, metals, plastics, and others according to the materials, and the materials are selected according to the application. Furthermore, various porous materials have been provided in view of the difference in the manufacturing method and the structure involved.

[0004] Among these porous materials, those made of Al material are lightweight and easy to work, and furthermore have sufficient mechanical strength, and have an extremely wide range of application. A
One of the porous materials known to be composed of a material is generally called a so-called punching metal, which is made porous by forming a large number of through holes on an Al plate. It is.

On the other hand, in addition to a porous material made of an Al material, a sintered material is used.
The pores formed between the powder particles are three-dimensionally connected, and have a structure having an infinitely long flow path.

For this reason, the porous sintered body made of Al material has an extremely large filtration area as compared with that made of punched metal, so that it can exert a good effect on filtration of liquids and the like. Effects such as noise reduction and sound absorption are recognized, and they are used as noise reduction materials and soundproofing materials in industrial equipment, buildings, roads, and high-speed trains, for example, soundproof walls of bullet trains.

[0007] As described above, the Al porous sintered material is widely used as a sound deadening material or a sound absorbing material, and although it has an extremely wide range of uses, the raw material Al powder is very easily oxidized. Production by the sintering technique is said to be very difficult.

That is, in the case of using copper as a raw material, the copper powder can be fused together simply by heating without forming a green compact pressurized body before sintering. Quality material can be manufactured. However, powders of Al and its alloys are coated with a hard and high-melting alumina coating on the surface of Al powder particles if heated only in a non-oxidizing atmosphere, especially a reducing atmosphere. It is said that it is impossible to produce a porous material as an industrial product.

The reason for this is that Al itself is a metal that is very easily oxidized, and even when sintered in a non-oxidizing atmosphere containing almost no oxygen, it binds to a trace amount of oxygen contained therein and forms Al powder. This is because a thick and hard oxide film is formed on the surface of the aluminum alloy, and it is difficult to fuse the Al powder particles to each other due to the presence of the oxide film.

[0010] From this point of view, the present applicant has previously disclosed Japanese Patent Publication No. 56-18646 and Japanese Patent Publication No. 56-113.
No. 75, which proposes a method for sintering Al or its alloy powder while maintaining a sufficiently high porosity in Al or its alloy powder particles in which such difficult conditions exist. Did the thing.

In this method, for example, an Al powder substantially containing Al is mixed with an Al alloy powder containing a component such as Cu so as to be eutectic with Al, and the melting point of the Al alloy is eutectic. This is a method in which the Al alloy powder is melted by utilizing the lowest point, and the Al alloy powder is bonded and sintered.

This method solves the problem that it is difficult or almost impossible to produce a porous material by sintering Al powder, and opens the way. The Al porous sintered material manufactured as described above is provided on the market as a filter or a sound absorbing material.

[0013] However, this method has opened the way to the production of a porous sintered material using Al powder as a raw material. Because it depends only on the mechanical properties of the obtained porous sintered material, for example, there are problems with bending and the like, and from the aspect of industrially stable production, there are many points to be improved. Improvement of the point is strongly desired.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances.
In producing Al porous sintered material by sintering using l powder as a raw material, Al porous sintered material can be efficiently produced,
In addition, the manufactured Al porous sintered material provides a manufacturing method having excellent mechanical properties.

[0015]

That is, according to the method of the present invention, when a porous aluminum material is produced by sintering a raw material powder obtained by mixing an aluminum powder and an aluminum alloy powder, the aluminum alloy in the raw material powder is used. The powder contains a eutectic component that reacts with aluminum to form a eutectic composition having a melting point lower than the melting point of aluminum, and the raw material powder is substantially pressed into a carbonaceous or graphite mold. Spray without adding, then apply a pressure of 60 g / cm ² or more to the raw material powder in this mold, and heat and sinter at a temperature of 600 to 660 ° C. for at least 1 minute in a non-oxidizing atmosphere. It is characterized by doing.

The configuration of these means and their operation will now be described in detail.

First, Al is easily oxidized, and the alumina oxide film on the surface inhibits sintering, and sintering is difficult. Therefore, an Al alloy powder having a melting point lower by at least about 5 ° C. than the Al powder is added and blended.

In particular, this Al alloy powder can contain Si, Cu, Mn or Ni as a eutectic component.
One or more of these eutectic components can be blended.

As for the compounding amount of the eutectic component, the lowest melting point can be produced in the eutectic composition. However, in practice, if a decrease in the melting point of at least about 5 ° C. The eutectic component can be blended in any range that produces the eutectic composition.

When the Al alloy powder is blended and sintered as described above, the Al powder, the Al powder and the Al alloy powder are firmly bonded to each other, and a porous material having a strong bonding portion is obtained.

The particle size of the Al or Al alloy powder is preferably within a certain range, and more preferably, the particle size of the Al powder and the Al alloy powder is preferably maintained in a fixed relationship. Without this relationship, the sintering reaction does not go smoothly. In particular, it is necessary to make the Al alloy powder adhere to the periphery of the Al powder so that the particle diameter of the raw material powder has such a relationship.

The powder of Al or an alloy thereof is sintered while controlling the temperature for a certain time while applying a pressure in a certain range. Without such sintering, it is very difficult to efficiently produce a porous aluminum material industrially,
Further, the mechanical strength of the porous sintered material is reduced, and the pores cannot be uniformly dispersed.

By continuously sintering under these conditions, a porous Al sintered material can be manufactured on a commercial basis with the aim of high efficiency production.

The affinity of Al powder or Al alloy powder for oxygen is very large. Usually, even in a reducing atmosphere, A
A strong Al oxide film is formed on the surface of the 1 powder or Al alloy powder by heating, and the raw material particles cannot be fused to each other.

This is a problem when producing a porous sintered material. Particularly, in a porous sintered material in which pores are formed between Al particles, a green compact is formed by pressing before sintering. Therefore, the formation of an alumina-based Al oxide film poses a problem.

Therefore, it has been technically impossible to produce a porous Al material by a method called sintering until recently, and the production was impossible unless advanced technology and high-precision conditions were prepared.

In the present invention, this point has been thoroughly investigated, and the possibility of industrial production has been found.

First, the relationship between the Al powder and the Al alloy powder will be described. That is, in the Al alloy powder to be added,
And the eutectic component therein must be a eutectic composition, a hypoeutectic composition, or a hypereutectic composition, which must be lower than the melting point of Al aluminum.

The eutectic metal to be added forms a eutectic alloy in the initial stage of sintering reaction with Al, and has a concentration of eutectic having a concentration gradient such that its melting point is reduced. It is necessary to select the component metal.

In this regard, as a metal component that satisfies this condition alone, it is conceivable that lead, tin, zinc, etc., which have a lower melting point than Al, may be used. However, it is difficult to produce a porous Al material with these metal components. The reason for this is that the low melting point metal component is accompanied by deterioration of corrosion resistance and mechanical strength. Research has shown that a basic condition is preferably a eutectic alloy having a melting point as close to Al as possible.

Therefore, this range is 5 ° C. to 1 degree higher than that of Al.
It can be seen that the temperature is lower by 20 ° C., and from this point, Si, Mn, Ni, Cu and the like are preferable.

Further, unless the aluminum itself is activated in the vicinity of the melting point, the strength of the product is high and the product does not have the porosity.

In the present invention, the concentration of the eutectic component in the Al alloy powder is also preferably within a certain range.

That is, it is necessary that Al and the eutectic component react to form a liquid eutectic composition.

For example, when an Al-Si alloy is used, the eutectic point is 11.7% Si-Al, and the eutectic alloy used is an alloy having a Si% of 11.7% or more, for example, 27%. When a Si-Al alloy is used, a liquid eutectic composition is generated, and a porous aluminum material can be manufactured.

More specifically, as an initial reaction, first, an alloy having a composition of 20% or more of Si is formed in the vicinity of the melting point of Al and this alloy. A liquid phase forms. This liquid phase becomes a main pillar of the cross-linking reaction between Al particles, and the formation of a porous material is promoted.

When a Cu-Al alloy is added, C
In a u-Al alloy, since 33% Cu-Al has a eutectic composition, it is necessary to use a Cu alloy of 33% or more. For example, a 52% Cu-Al alloy is used.

Further, in order to improve corrosion resistance and workability, a metal which does not generate this liquid phase reaction can be added as an additional element. Examples include Ni and Mn. The former is for improving workability, and the latter is for improving corrosion resistance.

Next, it is necessary to use Al alloy powder having a smaller diameter than Al powder.

The diameter ratio is 1: 0.5 to 1: 0.01.
And

If it is larger than 0.5, the crosslinking reaction does not proceed during sintering, and it is difficult to produce a porous material. The lower limit of the diameter, 0.01, is originally better as small as possible, but there is no point in economically pulverizing further. For example, in the case of an Al-Si alloy, Al-S
The i-alloy used is 125 μm to 5 μm.

In the case of an Al-Cu alloy, it is preferable to use an Al-Cu alloy powder having a diameter of 150 to 50 μm for an Al powder having the same particle size.

Next, a sintering process is started using such a raw material. In this process, important factors are a reducing atmosphere, a pressure, and a temperature curve.

Pressing during sintering is not only to promote sintering and to make the plate size constant, but also to adjust porosity or porosity.

That is, it is preferable to increase the pressing force from the viewpoint of improving the sinterability. However, if the pressing force is too large, the porosity or porosity decreases, and a porous material cannot be formed. On the other hand, if it is too small, sintering does not proceed and it cannot be adjusted to a certain plate size.

From this, the present inventor studied this point and found the lower limit for pressing to such an extent that dimensional accuracy was maintained during sintering.
g / cm ² . If it is less than 60 g / cm ² , the effect is not obtained. Further, in order to ensure a porosity of 30% or more and to make the formed pores uniform, the pressing force should be 500 g / cm ^2.
The following is preferred. By activating the particle surface of the Al powder by applying pressure, the sintering reaction between the Al powder and the Al alloy to be added is promoted, and the force of pulling the particles together can be suppressed. We can manufacture quality materials.

In the case of pressurizing in this way, the most efficient method is to put the raw material powder in a molding die, stack the molding dies in layers, and press the raw material powder located below by its own weight. Become highly efficient.

FIG. 1 shows a specific example. As shown in FIG. 1, molding dies 2 containing raw material powders 1 are sequentially stacked. In this way, a unit lot is piled up and continuously put into a sintering furnace and sintered. This method is the most economical and provides a predetermined pressure during sintering. The atmosphere during sintering is preferably a non-oxidizing atmosphere, in particular, it is desirable to control the reducing atmosphere so that the dew point is -40 ° C or less.

That is, when the sintering is performed repeatedly, the temperature of the raw material powder can be strictly and uniformly maintained throughout, and at least the Al alloy powder added with the Al powder at a temperature of 660 ° C. to 600 ° C. in the above atmosphere. Is held for 1 minute or more.

[0050]

【Example】

Example 1 An Al—Cu alloy (52% Cu—Al, particle size 1) was prepared using powder of Al (purity = 99.8%, particle size 100 to 300 μ).
(50-50 .mu.) Powder is mixed so that Cu is 3% by weight, and this is sprayed on a carbon mold, and a reducing atmosphere (hydrogen 20% -nitrogen, dew point -60.degree. C.) )
The solution was kept at 630 ° C. for 5 minutes, cooled to 100 ° C. or lower, and taken out.

The pressing force at this time was 200 g / cm ² , and a porous Al sintered material having a porosity or a porosity of 45% could be produced.

Example 2 Al powder (purity = 99.8%, particle size 100-300 μm)
Using Al-Si powder (26% Si-Al, particle size 12
(5 μm to 4 μm) was mixed as 1% by weight as Si, and the mixture was sprayed on a mold made of carbon, and reduced under a pressure of 250 g / cm ^{2 under} a reducing atmosphere (20% hydrogen). -Nitrogen) at 630 ° C for 1 minute, 100 ° C
It was cooled and taken out below. 100 pores between Al particles
A porous Al sintered material having continuous pores of about 200 μm was produced.

Example 3 Al powder (purity = 99.8%, particle size 100-300 μm)
Using Al-Si powder (26% Si-Al, particle size 12
5 to 4 μ) as 1% by weight of Si, and Mn powder (particle size of 4 to 70 μ) so as to be 1.4% by weight by weight. The mixture was sprayed on a mold, kept at 630 ° C. for 5 minutes in a reducing atmosphere (20% hydrogen-nitrogen) under a pressure of 60 g / cm ² , cooled to 100 ° C. or lower, and taken out. When a salt spray test (according to JIS Z2371) was carried out for 2,000 hours as corrosion resistance, generation of white rust was hardly observed.

Example 4 Al powder (purity = 99.8%, particle size 100-300 μm)
Using an Al-Cu alloy (52% Cu-Al, particle size 15
0 to 50μ) and 0.4% by weight of Cu, and 1% of Ni powder (3 to 70μ), and the mixture is mixed with a carbon mold. It was sprayed on, kept at 630 ° C. for 5 minutes in a reducing atmosphere (20% hydrogen-nitrogen), cooled to 100 ° C. or lower, and taken out. This pressure was 100 g / cm ² . The porous Al sintered material thus obtained has very good bending workability,
= 25 mm rounding was possible.

[0055]

According to the present invention, an Al alloy containing a eutectic component which reacts with Al to form a eutectic composition having a melting point lower than the melting point of Al is blended with the Al powder, and the raw material powder is made of carbonaceous or carbonaceous material. It is sprayed into the graphite mold without substantially applying pressure, and then 60 g /
The sintering is performed by applying a pressure of ² cm ² or more and maintaining the temperature at 600 to 660 ° C. for at least 1 minute in a non-oxidizing atmosphere.

When manufactured in this manner, a porous Al sintered material can be easily and continuously manufactured, and the resulting porous A
(1) The sintered material can secure mechanical strength, improve bending workability, which has been conventionally regarded as a problem, and can further increase the porosity because the bridge portion itself can be made thinner. Therefore, it is suitable as a sound absorbing material, a filtering material, an adsorbing material, and the like for high-speed trains, automobiles, and industrial equipment.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment for implementing the method of the present invention.

[Explanation of symbols]

 1 Raw material powder 2 Mold

Claims (7)

[Claims] 1. When sintering a raw material powder obtained by mixing an aluminum powder and an aluminum alloy powder to produce a porous aluminum material, the aluminum alloy powder in the raw material powder reacts with aluminum. A eutectic component that produces a eutectic composition having a melting point lower than the melting point of aluminum is contained, and this raw material powder is sprinkled into a carbonaceous or graphitic mold without substantially applying pressure. A step of applying a pressure of 60 g / cm ² or more to the raw material powder in the mold and maintaining the temperature at 600 to 660 ° C. for at least 1 minute in a non-oxidizing atmosphere to heat and sinter the material; The method of manufacturing the binder. 2. The method for producing a porous aluminum sintered material according to claim 1, wherein the particle diameter of said aluminum alloy powder is made smaller than that of said aluminum powder. 3. The aluminum alloy powder has a particle size ratio of 1: 0.5 to 1: 0.01 with respect to the aluminum powder.
The method for producing a porous aluminum sintered material according to claim 1, wherein the adjustment is made to the following conditions. 4. The porous aluminum sintered material according to claim 1, wherein said stacking is performed such that a pressure of 60 g / cm ² or more is applied to the raw material powder in said carbon mold. Production method. 5. The raw material powder in the molding die is added at 60 g / cm.
^{2. The} method according to claim 1, wherein when the sintering is performed by applying a pressure of ² or more and maintaining the temperature at 600 to 660 [deg.] C. for at least one minute or more, the forming dies are vertically stacked and pressed. Method for producing a porous aluminum sintered material. 6. The aluminum alloy powder, wherein one or more components selected from Si, Cu, Mn and Ni are contained as the eutectic component. Item 4. The method for producing a porous aluminum sintered material according to Item 1. 7. The method according to claim 1, wherein the non-oxidizing atmosphere is a reducing atmosphere.