RU2233346C1 - Aluminum alloy for preparing aluminum foam and method for preparing aluminum foam from it - Google Patents

Abstract

FIELD: metallurgy, alloys.

SUBSTANCE: invention can be used in preparing metal foams. Invention proposes alloy comprising the following components, wt.-%: magnesium, 5-6; zinc, 20-40; copper, 4-6; aluminum, the balance. Invention proposes also a method for preparing aluminum foam from this alloy that involves preparing the melt of aluminum alloy by the preparing aluminum melt, addition of magnesium to it in the amount 45-55% of the required content in ready alloy, intensive stirring of prepared melt for 8-10 min at temperature above liquidus temperature of the prepared alloy and addition of other components and magnesium. Then method involves continuous casting the aluminum alloy melt with simultaneous addition to it a blowing agent, deformation of ingot and its thermal treatment. The proposed alloy for preparing aluminum foam and a method for preparing aluminum foam from it provides preparing the highly qualitative solid ingot owing to prevention of melt foaming before ingot solidifying that allow carrying out the effective deformation of ingot under pressure.

EFFECT: improved preparing method.

3 cl, 1 ex

Description

The present invention relates to the field of metallurgy and can be used to obtain foam metals.

Known aluminum alloy composition A1 - 9% Si with the addition of 10-20% SiC and a method for producing foam from it, including the preparation of a melt based on aluminum, preliminary heat treatment of porophore (TiH ₂ ) to delay its decomposition, the introduction of silicon carbide (SiC in the melt) ), the introduction of porophore, pouring into the mold and heat treatment of the obtained casting (A Novel Melt-Based Route to Aluminum Foam Production. V. Gergely, TW Clyne, Metal foams and porans metal structures. International Conference on Metal Foams and Porous Metals Structures, 14 th -16 th June, 1999, Bremen (Germany), p. 83-89).

The disadvantage is the high liquidus temperature of the alloy (~ 600 ° C), this leads to a partial decomposition of the porophore upon introduction and, as a result, to the formation of gas shells in the resulting casting.

Known deformable aluminum alloy B95 containing: 1.4-2.0% Cu; 1.8-2.8% Mg; 0.2-0.6% Mn; 5-7% Zn; 0.1-0.25% Cr (see GOST 4784-65) and a method for producing foam from it, including melt preparation, continuous casting with the simultaneous introduction of porophore, deformation and heat treatment (see I. S. Polkin. Russia, patent No. 2180361 (2002).

The disadvantage is the partial decomposition of the porophore prior to solidification of the melt due to the high temperature of the liquidus alloy (638 ° C). As a result, obtaining a partially foamed ingot or termination of the continuous flow (casting) of the melt. The foamed ingot is not suitable for obtaining high-quality deformed semi-finished products, homogeneous foam aluminum.

In addition, in the heat treatment process due to insufficient viscosity, a high foaming coefficient and, as a result, a low specific gravity are not achieved; a high foaming rate is not ensured and, as a result, a high probability of foam destruction is created. As a result, the yield is reduced.

An aluminum alloy is proposed containing magnesium, zinc, copper with a ratio of components, wt.%:

Magnesium 5-6

Zinc 20-40

Copper 4-6

Aluminum Else

The proposed alloy differs from the prototype in that the components are taken in the ratio, wt.%:

Magnesium 5-6

Zinc 20-40

Copper 4-6

Aluminum Else

A method for producing foamed aluminum from an aluminum alloy is proposed, which includes producing an aluminum melt, introducing magnesium into it in an amount of 45-55% of the required content in the finished alloy, intensively mixing the obtained melt for 8-10 minutes at a temperature not higher than the liquidus temperature of the obtained alloy, introduction other components and magnesium, continuous casting of an aluminum alloy melt with the simultaneous introduction of porophore, deformation and its heat treatment. The proposed method differs from the prototype in that the melt of the aluminum alloy according to paragraph 1 is obtained by obtaining an aluminum melt, introducing magnesium in it in an amount of 45-55% of the required content in the finished alloy, intensively mixing the resulting melt for 8-10 minutes at a temperature not above the liquidus temperature of the resulting alloy, and the introduction of the remaining components and magnesium.

Effect: obtaining a high-quality dense (non-foamed) ingot due to the prevention of foaming of the melt before the ingot solidifies. As a result, the possibility of effective deformation under pressure (pressing, rolling). An increase in viscosity in the liquid-solid state and, as a consequence, an increase in the coefficient of foaming, an increase in the speed of foaming. As a result, a decrease in specific gravity, a decrease in the risk of foam destruction, an increase in the yield.

To obtain foamed aluminum, titanium hydride (TiH ₂ ) is usually used as a porophore. This is due to the fact that the temperature range of the active decomposition of titanium hydride (≈550-650 ° С) is close to the temperature range of crystallization of industrial aluminum alloys (≈500-650 ° С). On the other hand, the proximity of temperature ranges indicated by physicochemical transformations determines the difficulty of introducing titanium hydride into the molten aluminum alloys, while avoiding the active decomposition of TiH ₂ . Taking into account kinetic factors, in the process of continuous casting, this is possible provided that the temperature of the liquidus of the alloy is lower than the temperature of the onset of active decomposition of titanium hydride, i.e. the liquidus of the alloy should not exceed 550 ° C.

The liquidus temperature of the proposed alloy is ~ 500-530 ° C, therefore, the active decomposition of porophore when it is introduced into the melt stream during continuous casting does not occur. This leads to good fluidity during casting and the possibility of obtaining a dense (non-foamed) ingot suitable for obtaining high-quality deformed semi-finished products and, correspondingly, high-quality foam aluminum, characterized by uniformity of the feather space and a high foaming coefficient.

The latter is ensured by increasing the viscosity of the alloy in the liquid-solid state by mixing dispersed magnesium oxide into the melt, obtained by dispersing the surface oxide film during mechanical mixing of the melt.

A viscosity high enough for effective foaming is also maintained at elevated temperatures after the alloy is melted during the heat treatment, since the resulting molten / magnesium oxide system is a suspension. The viscosity of the suspension increases with increasing dispersion of MgO particles, which is achieved in the case of melt mixing (before casting) at a temperature not higher than the liquidus of the alloy. An increase in the coefficient of foaming due to an increase in viscosity is achieved in conjunction with an increase in the rate of foaming. The corresponding reduction in exposure during heat treatment reduces the risk of foam destruction.

Example. In a crucible induction furnace, ~ 500 kg of an alloy of the following composition was prepared (as calculated): Mg - 5%; Zn - 40%; Cu - 5%; Al is the rest.

The liquidus temperature of the alloy of this composition is ~ 530 ° C. First, aluminum was melted (300 kg), magnesium was introduced into molten aluminum in an amount of 12.5 kg, which is 50% of the required content.

The liquidus temperature of the obtained Al alloy is 4.2% Mg and is, according to the Al-Mg state diagram, ~ 638 ° C. After the introduction of magnesium, the melt was intensively mixed at a temperature of ≈630 ° C using a paddle mechanical mixer rotating at a speed of ≈1100 rpm for 10 minutes. At the end of mixing, the melt was heated and copper, zinc and the remaining magnesium were introduced in the amount of 12.5 kg.

After the alloying components were introduced, the melt was poured using a siphon into a casting mixer and, at a temperature of ≈600 ° C, was poured by continuous casting into a sliding mold with a diameter of ⌀ 200 mm and a height of H = 100 mm. The casting speed was ~ 10 cm / min. At the same time, TiH ₂ porophore was introduced in the form of a powder with a dispersion of ≈30 μm (1.2 wt.% Calculated) into a liquid alloy well in a crystallizer with continuous stirring using a rotating mechanical stirrer. The result was an ingot containing ≈1 wt.% Uniformly distributed particles of TiH ₂ . The obtained ingot was pressed onto a strip, which was rolled into a 3 mm thick sheet. The sheet was cut into dimensional blanks measuring 400 × 600 mm. Heat treatment was carried out at an electric furnace temperature of ≈700 ° С. Received a relatively homogeneous foam aluminum blanks with a foaming coefficient of ≈6, with a specific gravity of ≈0.5 g / cm ³ . For comparison, foam aluminum samples were obtained from alloy B95 with the composition: Al - 1.5%, Cu - 2%, Mg - 0.5%, Mn - 7%, Zn - 0.2%, Cr (prototype). Concentrated gas shells were found in the samples. The foaming coefficient was ~ 3, with a specific gravity of 0.8 g / cm ² .

Thus, the proposed alloy for producing foam aluminum and a method for producing foam from it can increase the uniformity of the pore space, increase the foaming coefficient (twice), reduce the specific gravity (≅ 1.6 times) of foam products, which will increase the yield not less than 30% and cost reduction.

Claims (2)

1. An aluminum alloy for producing foam aluminum containing magnesium, zinc, copper, characterized in that the components are taken in the following ratio, wt.%: Magnesium 5-6 Zinc 20-40 Copper 4-6 Aluminum Else 2. A method of producing foam aluminum from an aluminum alloy, comprising producing an aluminum melt, continuously casting an aluminum alloy melt with simultaneous introduction of porophore, deformation of the ingot and its heat treatment, characterized in that the aluminum alloy is melt according to claim 1 by producing an aluminum melt, introduction it contains magnesium in the amount of 45-55% of the required content in the finished alloy, intensively mixing the obtained melt for 8-10 minutes at a temperature not higher than the liquidus temperature of the obtained alloy and the introduction of the remaining components and magnesium.