JPH0215135A - Manufacture of permeable foamed aluminum - Google Patents

Abstract

PURPOSE:To obtain the title Al effective for a soundproof material, muffling material or filter by cutting foamed Al formed with many closed cells into the thickness thinner than the diameter of the closed cells and thereafter multitudiously laminating the obtd. permeable thin plates. CONSTITUTION:A foaming agent such as TiH2 is added and mixed to the molten metal in which metallic Al is melted and a thickener such as Mg is added to increase its viscosity, which is foamed and is thereafter subjected to cooling/ solidification to obtain foamed Al contg. closed cells. At this time, the diameter of the cells is suitably regulated to 1 to 3mm and the bulk density is preferably regulated to 0.2 to 0.4g/cm<2>. The foamed Al is then cut into the thickness thinner than that of the closed cells contained therein to prepare permeable thin plates in which closed cells are formed into through holes. At this time, the thickness of the thin plates is suitably regulated to 1 to 2mm in the case of 2 to 3mm diameter of the cells. The thin plates are then multitudiously laminated, by which the objective permeable foamed Al can be obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention cuts aluminum foam with a thickness thinner than the closed cells it contains, and makes the closed cells open holes to provide air permeability. The present invention relates to a method for manufacturing breathable aluminum foam useful as a sound deadening member or filter.

[Conventional technology] Methods for producing foamed metal include the solubility difference method, which utilizes the phenomenon in which scum dissolved in molten metal is released due to a rapid decrease in solubility during solidification, and the mixing of metal powder and foam cutting powder. There are two methods: the powder metallurgy method, in which the metal is heated above the melting point of the metal and foamed, and the molten direct mixing method, in which a foaming agent is directly added to the molten metal to cause it to foam, but the molten direct mixing method is the most commonly used. .

The molten metal direct mixing method consists of a melting process, a thickening process, a mixing process, and a foaming process. The thickening process is to give the molten metal an appropriate viscosity for the retention and dispersion of bubbles generated in the molten metal, and consists of blowing air or steam into the molten metal, adding additives for thickening, etc.

The mixing step is a step of mixing a blowing agent, and a compound that decomposes near the solidification temperature of the molten metal to generate gas is selected as the blowing agent. The foaming step is a step in which the foaming temperature is maintained to promote foaming of the foaming agent.

All of the above-mentioned methods for producing foamed metal generate foam by generating a large number of gases in the molten metal, so the cells contained in the foamed metal are all closed cells and have no air permeability, so they are also used for soundproofing. It was limited to materials. Therefore, in order to obtain a porous metal with air permeability, it has been necessary to use a precision casting method using a casting mold having communicating holes. However, the production of porous metals by precision casting has the disadvantage that production costs are extremely high.

[Problems to be Solved by the Invention] Therefore, if the closed cells contained in aluminum foam are made to have air permeability as communicating holes using an extremely simple and inexpensive method, aluminum foam will be able to muffle noise by utilizing the air permeability. Applications for parts, various filters, etc. will expand. The present invention was made in view of the above-mentioned problems with foamed aluminum, and the closed cells contained in foamed aluminum are used as communicating holes to provide air permeability. An object of the present invention is to provide a method for producing aluminum foam.

[Means for Solving Problem 1] The present inventor focused on the fact that when aluminum foam is cut to a thickness thinner than the diameter of the closed cells contained in the foamed aluminum, the closed cells become a large number of through holes, and furthermore, the inventors have focused on the fact that when aluminum foam is cut to a thickness thinner than the diameter of the closed cells contained in the foamed aluminum, the closed cells become a large number of through holes. The present invention was completed based on the idea that breathable foamed aluminum could be manufactured by laminating a large number of thin plates.

The method for producing breathable foamed aluminum of the present invention includes a step of melting metal aluminum and adding a thickener to thicken the molten metal, a step of adding and mixing a foaming agent to the molten metal, and a step of adding a foaming agent to the molten metal and mixing it. A step of foaming and then cooling and solidifying it to form foamed aluminum having closed cells; and a step of cutting the foamed aluminum to a thickness thinner than the diameter of the closed cells it contains to form a breathable thin plate with the closed cells as through holes. and a step of laminating a large number of the air-permeable thin plates.

[Operation] Melting of the metal is achieved using any known melting furnace. Suitable thickeners to be added are Mg, Ca or A1□03. By adding a thickener, the molten aluminum is given sufficient viscosity to retain air bubbles.

The blowing agent is preferably a compound that has a melting point near the melting point of dissolved aluminum and generates decomposition gas; in the case of aluminum, T i H2 or ZrH2 is used. It is necessary to uniformly disperse the blowing agent into the highly viscous molten metal very quickly.

The molten metal mixed with no blowing agent is heated and maintained at a temperature at which the blowing agent generates decomposed gas, foams, and then solidifies. The amount and size of the bubbles contained in the foamed metal can be freely controlled by controlling the viscosity in the thickening process that is performed prior to foaming the molten metal, and by controlling the amount of the blowing agent mixed into the molten metal. The diameter of the bubbles is 1 to 3III1
1 is suitable, and its bulk density is 0.2 to 0,4 H/
It is preferably in the range of cm2. The diameter of the bubble is 1m
If the diameter is less than m, no through holes will be formed when the thin plate is manufactured, and if the diameter of the bubbles exceeds 3 mm, the air permeability will become too large. Also, the bulk density is Q, 2
This is because if the bulk density is less than 4 g/cm2, the number of through holes will be insufficient, and if the bulk density exceeds 4 g/cm2, the function as a filter or the like will be insufficient.

The thickness of the breathable thin plate cut out from foamed aluminum is made thinner than the diameter of the closed cells contained in the foamed aluminum. When the diameter of the bubbles is 2 to 3 m+n, the appropriate thickness of the breathable thin plate is 1 to 2 mm. This is because if the thickness of the breathable thin plate is less than 1 mm, the thin plate has insufficient strength and is easily broken, and if it exceeds 2I, sufficient through holes cannot be secured. The number of laminated breathable thin plates is appropriately selected depending on the application.

“Examples” The present invention will be explained using Examples to clarify the characteristics of the present invention.

5 kg of aluminum was melted in a melting furnace and poured into a ladle.
1 kg of A I 20 * finely ground to 0 mesh was added and thoroughly stirred to thicken the mixture.

Subsequently, T I was added to the thickened molten aluminum as a blowing agent.
820.05 kg was added, and the molten aluminum was thoroughly mixed using a stirrer equipped with a blade at the tip.

Next, molten aluminum was poured into a mold that had been previously heated to 500°C. At this time, since the molten aluminum was sticky due to the thickening process, it was squeezed out of the ladle using gas pressure.

Next, the molten aluminum in the mold is heated to 72°C along with the mold.
The temperature was raised to 0°C and held for 7 minutes to decompose the foaming agent mixed into the molten aluminum and generate scum. The molten aluminum was cooled while some foaming still existed to obtain a foamed metal.

The obtained foamed aluminum 11 was cut to a thickness of 2 mm,
As shown in FIG. 1, a breathable thin plate 12 with through holes 10 made of closed cells was obtained. A filter 14 was formed by stacking ten of these breathable thin plates 2 as shown in FIG.

When this filter 14 was attached to a gasoline engine and used as a blow-by gas filter, it did not become clogged even after long-term use and had superior filter performance compared to paper or cloth filters. Ta.

Although this example shows an example of use as a flow-by gas filter, the foamed metal filter of the present invention can be used as a filter for flow-by gas.
It can also be used as a filter for other gases containing oil mist.

Furthermore, the breathable aluminum foam obtained by the present invention is
It was confirmed that it exhibited excellent performance not only as a filter but also as a sound deadening member.

[Effects of the Invention] The method for producing breathable foamed aluminum of the present invention is as follows: After foaming molten aluminum, the foamed aluminum is cut to a thickness thinner than the diameter of the closed cells it contains. By manufacturing a breathable thin plate with closed cells as through holes and stacking a large number of these breathable thin plates, the closed cells are interconnected to form breathable foamed aluminum, which gives breathability to the foamed aluminum. By doing this, it is possible to obtain breathable metal foam in an extremely simple way and at low cost, and it has the excellent effect of expanding its use as a sound deadening material or filter, which was previously limited to use as a soundproofing material. .

[Brief explanation of the drawing]

FIG. 1 is a plan view of the breathable thin plate, and FIG. 2 is a sectional view of the filter. 10.Thin plate, 14.Filter. Diagram

Claims (1)

[Claims] (1) A step of melting metallic aluminum and adding a thickener to thicken the molten metal, a step of adding a foaming agent to the molten metal and mixing it, and a step of foaming the molten metal and then cooling and solidifying it to form closed cells. a step of cutting the foamed aluminum to a thickness thinner than the diameter of the closed cells it contains to form a breathable thin plate with the closed cells as through holes; 1. A method for producing breathable foamed aluminum, the method comprising the step of laminating layers.