JPH0317236A - Manufacture of foamed metal - Google Patents

Abstract

PURPOSE:To manufacture the formed metal in which fine gas bubbles are uniformly dispersed over the whole of the metal with high productivity by dissolving a soluble gas into a molten metal, rapidly reducing the pressure to generate gas bubbles and solidifying them in a formed state. CONSTITUTION:A soluble gas (such as an H2 gas and an N2 gas) is dissolved into a molten metal 1 by bubbling and is abundantly incorporated. Next, the pressure in the atmosphere is rapidly reduced and the dissolved gas components are generated as fine gas bubbles over the whole area of the molten metal 1. In the above state, e.g. cooled copper plates 2 are charged into the molten metal 1, which is rapidly solidified as formed and the solidified zone X is discharged as a foamed metal. Furthermore, for regulating the foaming rate to about >=0.8, the atmospheric pressure Pa in a furnace in the treatment at the time of reducing pressure to the equilibrium gas partial pressure Px of the soluble gas components dissolved in the molten metal 1 is controlled by the condition shown in the inequality of Px-Pa>=0.1 (atm). In this way, the foamed metal in a uniform foaming state can easily be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a metal foam having voids inside.

[Conventional technology]

Foamed metals, such as foamed aluminum, in which fine gas bubbles are uniformly dispersed throughout the metal, can be used as construction materials that take advantage of their lightweight rigidity, nonflammability, and sound-absorbing properties, and as shock absorbing materials for automobiles that take advantage of their WN impact absorption and lightness. Due to its light weight and rigidity, it is used in container materials such as the core material of sand inch panels.

[Problem that the invention seeks to solve]

Conventionally, such foamed metal 1 has been manufactured by mixing a foaming agent into molten metal and foaming it, but it is difficult to uniformly disperse the foaming agent, which poses problems in terms of productivity. Ta.

The present invention was devised in view of the above problems, and it is an object of the present invention to provide a new method by which a uniform foamed state can be easily obtained without performing the above-mentioned mixing operation, which is difficult to achieve uniform dispersion.

[Means for solving problems]

Therefore, the basic principle of the present invention is to dissolve a soluble gas in the molten metal, then rapidly reduce the pressure to generate gas bubbles in the molten metal, and solidify the molten metal in this foamed state. It is a feature. The configuration of the present invention will be described in detail below using the examples shown in FIGS. 1(a), 1(b), and 1e. First, the same figure (a)
As shown in , a gas soluble in the molten metal (1) (for example, H2 gas or N2 gas in the case of molten steel) is bubbled into the molten metal (1) to dissolve it. If this is done under a pressurized atmosphere, a large amount of the gas will dissolve. Next, if the atmosphere is rapidly reduced in pressure, such as by making it into a vacuum state, the previously dissolved gas components will appear throughout the molten metal (1) as fine gas bubbles, as shown in Figure (b). ．． In this state, for example, as shown in the same figure (C), the copper plate (2)
(2) The molten metal (
1) If the molten metal is charged into the molten metal (1)
The foam is rapidly cooled and solidified while still in a foamed state.

This solidified portion X is then taken out as a foamed metal.

In addition, the present inventors conducted experiments in the Examples described below, and in carrying out the above method, reduced pressure treatment conditions were determined so that the foaming ratio H, which is generally required for foamed metals, would be 0.8 or more. We will clarify this and propose it as the second invention. That is. 713 Soluble gas dissolved in molten metal (X)
It is characterized by controlling the atmospheric pressure Pa in the furnace during pressure reduction with respect to the equilibrium gas partial pressure Px under the conditions shown in the following equation. Px-Pa≧O. l (at+i) [Example] Specific examples of the present invention will be described below.

First, 1 kg of Fa-based molten metal is melted in an N2 gas atmosphere,
The pressure was rapidly reduced in the vacuum melting furnace. This reduced pressure is due to the N in the molten metal.
The atmospheric pressure Pa in the furnace is lowered to below the equilibrium gas partial pressure Px of the two gases, and the average of (Px-Pa) is 0.2.
It was called ATM. At this time, a large amount of fine N2 gas bubbles are generated throughout the molten metal, resulting in a foaming state. After confirming this foamed state, two cooled copper plates were inserted into it, and the molten metal between the copper plates was solidified to obtain a foamed metal.
When a part of this metal was sampled and its foaming rate H was measured, it was found to be 0.82.

While conducting the above experiments, the inventors realized that the following matters were important. In other words, from the time the cooling operation starts from the foaming state until the molten metal solidifies, it is necessary to maintain the state in which the generated bubbles lift the metal, but in order to do this, a certain amount of gas generation is required. This means that Therefore, the present inventors further conducted an experiment to examine the relationship between the furnace atmosphere pressure Pa, which is related to the amount of gas bubbles generated, and the foaming rate H of the foamed metal, and obtained the results shown in FIG. 2. This figure is a graph showing how much the foaming rate H of the molten metal becomes when the furnace atmosphere pressure Pa is lowered to a value lower than the equilibrium gas partial pressure Px of the N2 gas component in the molten metal. ．． Note that this X-axis coordinate is the average of the difference (Px-Pa) between the equilibrium gas partial pressure Px and the furnace atmosphere pressure Pa during the pressure reduction process. As shown in FIG. 3, the foaming rate H is determined by determining how much h2 the bath surface height after foaming has increased from the bath surface height h0 before foaming, and using the following equation.

As is clear from the figure, the average (Px-Pa) is 0.1
It can be seen that when the foaming rate H is 0.8 or more when the foaming rate is 0.8 or more. Therefore, in order to obtain a foamed metal after solidification, it is necessary to control the furnace atmospheric pressure Pa so that Px-Pa is at least 0.1 atm or more.

〔Effect of the invention〕

As detailed above, according to the method of the present invention, there is no need to perform operations such as mixing a blowing agent. It is possible to obtain a uniform foamed state in molten metal and easily increase the productivity of foamed metal.

[Brief explanation of drawings]

Figure 1 (a), (b), and (c) are process explanatory diagrams of the method of the present invention, Figure 2 is a graph showing the correlation between the foaming rate H and the average (Px-Pa), and Figure 3 is a graph showing the correlation between the foaming rate H and the average (Px-Pa). It is an explanatory diagram explaining how to find. In the figure, (1) shows the molten metal, and (2) shows the copper plate. Figure 1 Qas pub song

Claims (1)

[Claims] 1. Dissolving a gas soluble in the molten metal, and then rapidly reducing the pressure to generate gas bubbles in the molten metal,
A method for producing a foamed metal characterized by solidifying the molten metal in this foamed state. 2. Dissolving a gas soluble in the molten metal, and then rapidly reducing the pressure to generate gas bubbles in the molten metal;
In this method for producing foamed metal in which the molten metal is solidified in the foamed state, when the foaming ratio of the resulting metal is set to 0.8 or more, the soluble gas component [X
] A method for producing a foamed metal, which comprises controlling the atmospheric pressure Pa in the furnace during depressurization with respect to the equilibrium gas partial pressure Px under the conditions expressed by the following formula. Px-Pa≧0.1 (atm)