JPS61231144A - Manufacture of porous aluminum - Google Patents

Abstract

PURPOSE:To manufacture high-quality porous Al with high productivity by allowing powdery potassic salt of aluminum CONSTITUTION:A slurry of powdery flux consisting of potassic salt of aluminum fluoride in an aqueous or volatile solution is.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing porous aluminum.

[Conventional technology]

Various methods have been proposed to produce porous metals, including a sintering method that utilizes the diffusion phenomenon of metal atoms caused by external thermal energy at the interface between two contacting powder metals. As a manufacturing method that utilizes the porosity of other materials, there is an incineration method in which metal is attached to the surface of expanded polystyrene using a surface treatment method such as electrodeposition, and then the expanded polystyrene is burned to obtain a mesh-like porous metal. By baking water-soluble particles such as sodium chloride into a predetermined shape,
There is an elution method in which a molten metal is injected under pressure into the gaps between the particles and solidified, and then this sodium chloride is dissolved in water to obtain a network-like porous metal.
A foaming method is known in which a porous metal is obtained by adding a gas generating compound such as a hydride of r to supersaturating the gas content of the molten metal and solidifying the metal to create a porous metal.

[Problem that the invention seeks to solve]

However, in the above sintering method, it takes several hours for the metal atoms to diffuse, and if there is dirt or foreign matter on the contact surface, the diffusion rate is extremely reduced and the bonding force between the metals is weakened. In addition, in the incineration method or elution method that utilizes the porosity of other materials, styrofoam oxides and sodium chloride may be deposited inside the porous metal. There is a risk of residual particles, etc., and since the thickness of the metal body becomes thinner, there are problems such as low mechanical strength.Furthermore, in the foaming method, there are variations in the location of pores, and the molten metal There was a problem in that the temperature distribution, especially near the bottom of the furnace and near the surface of the molten metal, had a large temperature difference, and the solidification rate also depended on the size of the pores, resulting in uneven pore distribution and unstable quality.

In addition to the above, a lightweight particle diffusion method is known, but the porous metal produced by this method has an extremely low porosity (
It cannot be said to be a true porous metal.

Furthermore, in the above-mentioned sintering method and elution method, in order to bond separated metals together, if the metals are in a solid state, the oxide covering the metal surface must be removed to remove the metal atoms. Due to the added energy required for diffusion, a high temperature and high pressure atmosphere had to be created. Furthermore, since the application of high temperature makes the gaps between the metals very dense, it is not suitable as a method for manufacturing porous metals that bond metals together and require large gaps.

In addition, as a method of bonding separated metals, a type of brazing method is known in which the oxide coating the metal surface is chemically removed using flux, and the metal atoms are bonded by heating. However, the porous metal obtained by this method has the drawbacks of weak mechanical bonding strength and poor bending workability and impact resistance, and like the above method, it was not an appropriate method.

[Means for solving problems]

The present invention was devised in view of these points of view, and has good productivity and workability, allows for arbitrary control of pore size and porosity, and has strong intermetallic bonds with no residual foreign matter. The present invention provides a method for producing porous aluminum.

That is, the present invention is capable of cutting Al-S into a linear shape, an 11M shape, a chip shape, etc., and having a large difference between the solidus temperature and the liquidus temperature.
n-based, Al-Pb-based, Al-Si-Cu-based, Al-Mg
-Si-based or Al-Zn-Mg based alloy material surface,
After applying an aqueous slurry of a powdered flux or a slurry of a volatile solution consisting of potassium aluminum fluoride salt and drying it, it is placed in a mold, etc., and heated in a heating furnace etc. to a temperature higher than the homophase line temperature of the above alloy. This is a method for producing porous aluminum, in which the above materials are fused together by heating to a temperature below the phase line temperature and formed into a desired shape.

[Effect]

In the method of the present invention, a material such as an Al-Sn alloy or an Al-Pb alloy, on which 7 lux has been adhered and dried, is placed in a mold for molding, and the liquidus temperature is higher than the solidus temperature of the alloy. When heated to the following temperature, the shape of the metal materials (1) and (2) is maintained as shown in Figure 1, while
The liquid phase portions (1a) and (2a) of the metal partially eluted from the materials (1) and (2) are in a state where they are most easily diffused, so they are easily fused together.

Therefore, the liquid phase part (1a) (2a) of this eluted metal
), the metal (1) in the solid phase state (
2) are mechanically and metallically bonded to each other to form a porous metal.

Figure 2 shows, as an example, a binary phase diagram mainly based on Att-si in an Al-Si-Cu alloy. , solid state 1 (α in Fig. 2)
, the part indicated by α+β) is maintained within the temperature range (upper limit temperature...
solid state (511 m degrees), temperature range in which solid and liquid coexist (part indicated by L+α in Figure 2) (upper limit temperature...liquidus temperature), and all in a liquid state (in Figure 2). There are three states in the temperature range (above the liquidus temperature).

The present invention focuses on the above-mentioned temperature characteristics of aluminum alloys, and the temperature range where the same phase and liquid phase coexist is the temperature condition for bonding metal materials without destroying their shape. , the in-phase rate [in-phase amount/
It has been found that the temperature at which 1] of (same phase + liquid phase) is 60 to 95% is most suitable, and the method was completed based on this result.

In other words, when the solid phase ratio is within the above range, the metals in the liquid phase partially eluted from the adjacent metal materials (1) and (2) are in a state where atoms are most easily diffused, so they easily fuse together. Furthermore, because the in-phase ratio is high, the metal skeleton is strong and the state before heating is maintained.

Therefore, by heating to the above-mentioned in-phase ratio and immediately cooling, the fused liquid phase parts (1a) (2a) are solidified, and the adjacent metal material (1) is solidified as shown in FIG.
(2) are firmly connected.

Furthermore, Fig. 3 shows a binary phase diagram of an Al-Pb alloy. In this figure, when looking at the thermal properties of an aluminum alloy based on aluminum, the solid state l1l (in Fig. 3 α , the part indicated by α + β) is kept in the m degree range (upper limit temperature...solidus temperature), the temperature range where solid and liquid are mixed (solid phase - liquidus temperature), and all in the liquid state (The part indicated by L in Figure 3)
There are three states in the temperature range (above the liquidus temperature), but even in the case of this aluminum alloy, the optimal temperature condition for bonding the metal materials without destroying their shape is the in-phase state. In particular, in the temperature range where Pb with a low melting point is unevenly distributed in the grain boundaries of Al-Pb alloys, and when the state in which the grain boundaries are molten is regarded as the liquid phase, the solid phase ratio is 60 ~ The temperature range at which 95% is achieved is the above Al-Si-C
It has been found that this is preferable for the same reasons as in the case of U-based alloys.

Note that when the solid phase ratio is 95% or more, there is little liquid phase to be eluted, so that the metal materials (1) (2>) that are in mechanical contact with each other, as shown in ), the probability of fusion decreases, poor fusion occurs, and the metals tend to separate after solidification and cooling.

On the other hand, when the solid phase ratio is 60% or less, more liquid phase m is eluted, and this liquid phase flows to the lower layer due to the action of gravity and fills the gaps between the entangled metals.
Homogeneous porous metal cannot be obtained.

[Example 7] Hereinafter, the method for producing porous aluminum of the present invention will be specifically explained based on Examples.

First, a continuous casting billet (diameter 100φ) of Al-Pb (Al-5 wt % Pb) based aluminum alloy was lathed to an average width of 111111 and an average length of 300 m%.
A fibrous material with an average thickness of 0.3 am was obtained, and this material was degreased and washed with ethyl alcohol to produce a fibrous metal material (1).
shall be.

A slurry of 7 lux of potassium aluminum fluoride salt added to ethyl alcohol or water at a rate of about 1 g/100 CC was applied to the surface of the metal material (1) using an air spray method and dried.

Next, after filling the metal material (1) into the mold,
This mold is placed in a heating furnace with a nitrogen gas atmosphere, and the above-mentioned material (
1) The temperature at which the solid phase ratio becomes 60-95% (200-30%
0°C).

After the mold reaches the above temperature, the mold is taken out of the heating furnace, and after forced air cooling (using a fan in this embodiment), the porous aluminum is taken out from the mold.

Here, in the above embodiment, Al-P is used as the metal material.
b (Al-5 wt % Pb) type aluminum alloy is used, but in addition to this, Al-Pb type alloy, A j-
Si-Cu alloy system, Al-Mq-Si alloy system, or Al
-Aluminum alloys such as Zn-Mg alloys can be used.

Note that the heating temperature when using these aluminum alloys, that is, the temperature at which the solid phase ratio becomes 60 to 95%, is Al-
200-300℃ for Pb alloy, Al-81-C
u alloy system, Al-Mg-Si alloy system, and Al-Zn-
In each case of Mg-based alloys, the temperature is 490 to 550°C.

In addition, in the above embodiment, 7 lux of aluminum potassium fluoride salt made into a slurry is deposited on the surface of the metal material (1) by one air spray method, but instead of this one air spray method, A dipping method or a simple coating method may be used.

Furthermore, although a nitrogen gas atmosphere heating furnace is used as the heating furnace, it may be a normal heating furnace or a heating furnace that combines a heating furnace with an inert gas atmosphere and a vacuum heating furnace.

Furthermore, the shape of the porous aluminum product is formed into a desired shape such as a circle, square, triangle, polygon, etc. using a mold.

(Effects of the Invention) According to the method for producing porous aluminum of the present invention, (a) Compared to conventional sintering methods, heating and holding times are shortened, productivity is significantly improved, and costs are reduced. be able to.

(b) Conventional sintered metals and foamed metals are brittle and have poor workability, whereas the products obtained by the present invention have extremely high mechanical properties, especially ductility (elongation), and are difficult to bend, cut, etc. It's easy.

(c) In the case of the conventional method, the pore size and porosity depend on the manufacturing method and the effective range is narrow, but with the method of the present invention, the pore size and porosity can be changed arbitrarily by simply changing the shape of the material. , its t, lJ control range is wide.

(d) Since the metal bond is strong, it is resistant to heat shock and can be welded, for example.

(e) There is very little foreign matter contamination or residual foreign matter.

(f) The heat transfer coefficient is significantly improved due to the significant increase in the heat transfer area.

(g) It has electrical conductivity and has a high current collecting effect.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the state in which metal materials are bonded to each other in the method of the present invention, and FIGS. 2 and 3 are two-dimensional diagrams showing the state in which metal materials are bonded to each other. FIG. Explanation of symbols (1) (2)...Metal material, (1a) (2a)...Liquid phase part (3)...Contact part Fig. 1 Fig. 2 Fig. 3

Claims (7)

[Claims] (1) Al-Sn-based, Al-P that is cut into linear, fibrous, chip, etc., and has a large difference between solidus temperature and liquidus temperature.
An aqueous slurry of a powdered flux or a slurry of a volatile solution consisting of potassium aluminum fluoride salt is applied to the surface of a material of B type, Al-Si-Cu type, Al-Mg-Si type, or Al-Zn-Mg type alloy. A method for producing porous aluminum, which comprises adhering and drying the material, and then heating the material to a temperature above the solidus temperature and below the liquidus temperature of the alloy to fuse and shape the materials together. (2) The heating temperature for each of the above alloys is such that the solid phase ratio is 60 to 95%.
The method for producing porous aluminum according to claim 1, wherein the temperature is in the range of . (3) The heating temperature of the Al-Sn alloy is 200°C to 3
The method for producing porous aluminum according to claim 1, wherein the temperature is 00°C. (4) The heating temperature of the Al-Pb alloy is 200°C to 3
The method for producing porous aluminum according to claim 1, wherein the temperature is 00°C. (5) The heating temperature of the Al-Si-Cu alloy is 490°C.
The method for producing porous aluminum according to claim 1, wherein the temperature is 550°C to 550°C. (6) The heating temperature of the Al-Mg-Si alloy is 490°C.
The method for producing porous aluminum according to claim 1, wherein the temperature is 550°C to 550°C. (7) The heating temperature of the Al-Zn-Mg alloy is 490°C.
The method for producing porous aluminum according to claim 1, wherein the temperature is 550°C to 550°C.