JP2005344153A - Method for producing member made of foamed aluminum alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a member made of a foamed aluminum alloy, which can be applied to aluminum alloys with various melting points regardless of the alloy compositions, and inexpensively produces the member of the foamed alloy having superior recycability. <P>SOLUTION: This production method comprises the steps of: heating the aluminum alloy to melt it; adding a mixture of magnesium carbonate and calcium carbonate into the molten metal to foam it; and rapidly solidifying the foamed molten metal. Alternatively, the production method comprises the steps of: adding the mixture of the carbonates into the molten metal; then, solidifying the molten metal without foaming it; pulverizing it into pellets; forming the pellets into a precursor as needed; and then, heating the precursor in a mold to foam it. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a porous aluminum alloy, particularly a member made of foamed aluminum alloy, a foamed aluminum alloy member produced by the method, and a foamable aluminum alloy pellet used for producing such a foamed member. It is.

  Foamed aluminum is a material that is lightweight and has excellent functions such as heat insulation and sound insulation, and has a so-called plateau phenomenon in which deformation progresses under a certain stress when a compressive load is applied. If applied to this vehicle body, it is possible to efficiently absorb the impact energy at the time of collision, and it is suitable as an impact absorbing member.

As a method for producing such foamed aluminum, a precursor made of a mixture of an aluminum powder and a foaming agent is heated and foamed (for example, see Patent Document 1), or a foaming agent is added to molten aluminum and foamed (for example, In any case, a metal hydride such as TiH ₂ is added as a foaming agent for foaming.
It can be said that such a method of adding a foaming agent to molten aluminum is excellent in productivity and superior in cost compared with a method in which aluminum powder such as sintering is used as a starting material.

On the other hand, it is also known to use carbonate as a cheaper blowing agent instead of the expensive hydride as described above (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 11-12605 JP 2000-328155 A JP 2002-363664 A

However, in such a method of adding a foaming agent, it is common to add Ca in order to adjust the viscosity of the molten aluminum alloy (in addition to the above-mentioned patent documents, for example, Advanced Engineering Materials 2000). , 2, No. 4, p. 179-183), such an aluminum alloy containing Ca is likely to be an obstacle to recycling and reuse.
In addition, in the method of adding a carbonate such as calcium carbonate alone, the foaming temperature, that is, the decomposition temperature of the carbonate is almost constant. Therefore, applicable aluminum alloys are limited to alloys having a melting point corresponding thereto. It will be.

  The present invention has been made paying attention to the above-mentioned problems in the conventional method for producing foamed aluminum in which a foaming agent is added to a molten aluminum alloy. The object of the present invention is various, regardless of alloy components. A method for producing a foamed aluminum alloy member that can be applied to an aluminum alloy having a melting point of 5% and that can be produced at low cost, and a foamed aluminum alloy member produced by such a method. It is to provide.

  In order to achieve the above object, the present inventor has intensively studied the types and amounts of foaming agents, foaming conditions, and the like. As a result, various aluminum having different melting temperatures can be obtained by using a mixture of magnesium carbonate and calcium carbonate as a foaming agent. The present inventors have found that it is possible to deal with alloys and have completed the present invention.

  The present invention is based on the above knowledge, and the method for producing a foamed aluminum alloy member according to the present invention includes adding a mixture of magnesium carbonate and calcium carbonate to a molten metal obtained by heating and melting an aluminum alloy, and foaming the mixture. A manufacturing method for rapidly solidifying the molten foam in a mold, or a mixture of magnesium carbonate and calcium carbonate is similarly added to the molten metal, and the solidified aluminum alloy is pulverized and pelletized before starting foaming. None, in the manufacturing method in which the pellet is molded as necessary to form a precursor (precursor) and then heated in a mold and foamed, and the molten metal temperature of the aluminum alloy is 600 to 700 ° C. The ratio of the amount of magnesium carbonate and calcium carbonate added to is in the range of 90:10 to 50:50.

  The foamed aluminum alloy member of the present invention is manufactured by the above method.

  The expandable aluminum alloy pellets of the present invention are obtained by adding the carbonate mixture to a molten aluminum alloy and grinding the solidified aluminum alloy without foaming.

  According to the present invention, since a mixture of magnesium carbonate and calcium carbonate is used as a foaming agent, the decomposition temperature of the foaming agent is controlled by adjusting the blending ratio of these two carbonates having different decomposition temperatures. It is possible to adapt to the melting points of different aluminum alloys, and foaming can be performed efficiently, and a foamed aluminum alloy member having a high foaming rate can be manufactured stably and at low cost.

  Hereinafter, the present invention will be described in more detail. In the present specification, “%” means mass percentage unless otherwise specified.

In order to produce a foamed aluminum alloy member using a molten aluminum alloy as a starting material, it is necessary to select a foaming agent that decomposes and foams at the melting temperature of the aluminum alloy.
Further, in order to disperse the generated gas in the molten aluminum alloy and retain it, it is necessary to increase the viscosity of the molten metal.

The aluminum alloy to be used is selected in consideration of availability of raw materials, price, mechanical properties according to the purpose of use, and a foaming agent that efficiently foams at the melting temperature of the alloy is desirable.
As an aluminum alloy, not only pure aluminum having a high melting point or an alloy having a small amount of alloy elements, but also a general aluminum alloy having a low melting point, such as an Al-Si alloy, can be advantageous in terms of price and performance.

When carbonate is used instead of expensive metal hydride such as TiH ₂ as a blowing agent, the melting temperature must be adjusted to the decomposition temperature, and the range of choice of aluminum alloy is narrowed.
Therefore, if carbonates with different decomposition temperatures are used in combination without limiting the type of carbonate as a foaming agent to one, the effective decomposition and foaming temperature of the foaming agent can be reduced by melting each aluminum alloy. The temperature can be adapted, and various aluminum alloys can be freely selected according to the purpose.

That is, the decomposition temperature of calcium carbonate is approximately 500 to 900 ° C., and the decomposition temperature of magnesium carbonate is 400 to 700 ° C. Therefore, when these two carbonates are used in combination, the most efficient decomposition / foaming temperature can be obtained depending on the formulation. Can be set.
Specifically, when the melting point of the aluminum alloy to be used is low and it is desired to lower the foaming temperature, the proportion of magnesium carbonate is increased, and when the aluminum alloy having a high melting point is used, the proportion of calcium carbonate is increased. Good.

Since the melting point of practical aluminum alloys is mostly in the range of about 580 to 660 ° C., the molten metal temperature for foaming may be in the range of about 600 to 700 ° C., which is slightly higher than this. The distribution ratio between magnesium carbonate and calcium carbonate as the foaming agent is preferably in the range of 90:10 to 50:50. Moreover, it is more preferable to set it as 90: 10-80: 20 in the range of 600-650 degreeC, and 80: 20-50: 50 in the range of 650-700 degreeC.
When the distribution ratio is out of this range, decomposition / foaming hardly proceeds in the molten metal temperature range, and an aluminum alloy member having a high foaming rate may not be formed.

Further, the amount of the foaming agent to be added varies depending on the form of the member, the required foaming rate, and the like, but a range of 1 to 5% with respect to the molten aluminum alloy is appropriate.
That is, when the addition amount of the foaming agent is less than 1%, the degree of foaming is small, and so-called foamed aluminum is not formed. On the other hand, even if added over 5%, it takes time until it is added and decomposed / foamed, so the amount of oxidative consumption during that time increases, and the effective working ratio decreases. It wo n’t change that much.

In order for the bubbles generated by the decomposition and foaming of the foaming agent to stay and disperse in the molten aluminum alloy, it is desirable that the molten aluminum alloy has a certain high viscosity.
As a method for increasing the viscosity, it is effective to disperse ceramic fine particles or add an active metal such as Ca. However, when recycling foam aluminum parts and scrap after use, these additives are removed. Is not preferable because it is difficult.

Here, Mg and Zr are not as active as Ca, but since the thickening effect can be obtained by the addition amount and stirring, these materials may be added and stirred before adding the foaming agent. desirable.
When adding these Mg and Zr, it is desirable to add them in the form of an Al—Mg alloy or an Al—Zr alloy, and the yield can be improved. When these amounts are small, the effect of increasing the viscosity is thin, while when they are large, the viscosity tends to be too high and the degree of dispersion tends to decrease, so 1 to 3% is preferable.

There are two possible methods for producing the foamed aluminum alloy member of the present invention using a molten aluminum alloy as a starting material.
As a first method, a foamed molten aluminum aluminum alloy is immediately introduced into a mold, rapidly cooled and rapidly solidified to form a member, and a second method is a method of adding a foaming agent to the molten aluminum alloy. And then solidify by cooling before the start of foaming. The resulting ingot is pulverized into pellets, which are directly or molded into a precursor, heated in a mold, foamed, cooled and solidified. It is a member. In the second method, the number of steps is increased, but a member having a stable foaming rate can be obtained. Therefore, it is desirable to use properly according to the required performance of the foamed aluminum alloy member.

  In the first method, it is necessary to rapidly solidify the foamed molten aluminum aluminum alloy in the mold before the bubbles generated in the molten metal have disappeared. What is rapid solidification at this time? A cooling rate of 10 ° C./s or higher, preferably 30 ° C./s or higher is meant.

Moreover, the kind of aluminum alloy used as a base material is not specifically limited, Regardless of its melting point, it can be selected in a wide range according to the required performance of the foamed aluminum alloy member.
For example, in the case of a lower melting point, as a general die casting aluminum alloy, ADC12 (Al—Si—Cu system, melting point: about 580 ° C.), ADC10 (Al—Si—Cu system, melting point) defined in JIS H5302 As an aluminum alloy alloy for gravity casting, AC4B (Al—Si—Cu system, melting point: about 590 ° C.), AC8C (Al—Si—Ni—Cu—Mg system, melting point) as specified in JIS H5202 : About 580 ° C), and 4032 alloy (Al-Si type, melting point: about 580 ° C) defined in JIS H4000 and the like can be exemplified as the wrought material.
On the other hand, in the case where the melting point is higher, 6061 alloy (Al—Mg—Si system, melting point: about 650 ° C.), 5052 alloy (Al—Mg system, melting point: about 650 ° C.) similarly defined in JIS H4000 as an extender, Examples of the casting alloy include AC1A (Al—Cu type, melting point: about 650 ° C.) defined in JIS H5202.

  Furthermore, it is possible to use not only the existing alloys as described above but also newly designed alloys in consideration of strength and other performance.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples.

  1 kg each of various aluminum alloys as shown in Table 1 was dissolved in a crucible and kept at a predetermined temperature, and Mg as a thickener was 1 in each of Examples 1 and 2 and Comparative Examples 1 and 2. 0.5%, and Zr as a thickener was added 2.5% to Example 3, and when the temperature reached a predetermined temperature while adjusting the viscosity by stirring for 10 minutes, each foaming agent was added, The foamed aluminum alloy member was obtained by stirring and foaming for 2 minutes, immediately cooling in a mold, and rapidly solidifying.

The foamed aluminum alloy members according to the obtained Examples and Comparative Examples were cut, the foamed state was observed, and the density and porosity were measured. The results are also shown in Table 1.
Moreover, the cross-sectional photograph of the foaming member concerning Example 3 is shown in FIG. 1 as an example of the foaming aluminum alloy member by this invention.

  As is apparent from the above results, a foamed aluminum member having a relative density (volume ratio occupied by a metal other than the pores) of about 30% is prepared by adding a mixture of calcium carbonate and magnesium carbonate as a foaming agent. It was confirmed that it was possible.

It is a photograph which shows the cross-sectional shape of the foam aluminum alloy member manufactured by this invention.

Claims (7)

  A method for producing a foamed aluminum alloy member in which a mixture of magnesium carbonate and calcium carbonate is added to a molten aluminum alloy and foamed, and rapidly solidified in a mold, and the molten temperature of the aluminum alloy is 600 to 700 ° C. The method for producing a foamed aluminum alloy member, wherein the ratio of the amount of magnesium carbonate and calcium carbonate added to the molten metal is in the range of 90:10 to 50:50.   A mixture of magnesium carbonate and calcium carbonate is added to a molten aluminum alloy, and the aluminum alloy solidified without foaming is pulverized into pellets, and the pellets are heated in a mold and foamed. A manufacturing method characterized in that the molten metal temperature of the aluminum alloy is 600 to 700 ° C., and the ratio of the amount of magnesium carbonate and calcium carbonate added to the molten metal is in the range of 90:10 to 50:50. A method for producing a foamed aluminum alloy member.   When the molten metal temperature is in the range of 600 to 650 ° C., the ratio of the amount of magnesium carbonate and calcium carbonate added to the molten metal is 90:10 to 80:20, and the molten metal temperature is in the range of 650 to 700 ° C. 80: 20-50: 50 is set, The manufacturing method of the foaming aluminum alloy member of Claim 1 or 2 characterized by the above-mentioned.   The method for producing a foamed aluminum alloy member according to any one of claims 1 to 3, wherein the addition amount of the mixture of calcium carbonate and magnesium carbonate is 1 to 5% by mass ratio with respect to the aluminum alloy.   Prior to the addition of the mixture of calcium carbonate and magnesium carbonate, Mg and / or Zr is added in an amount of 1 to 3% by mass with respect to the aluminum alloy. The method according to any one of claims 1 to 4, A method for producing a foamed aluminum alloy member.   A foamed aluminum alloy member manufactured using the method according to any one of claims 1 to 5.   A foamable aluminum alloy pellet obtained by adding a mixture of magnesium carbonate and calcium carbonate to a molten aluminum alloy and crushing the solidified aluminum alloy without foaming.

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