Method for manufacturing refined aluminum alloy

Abstract

To provide a method for manufacturing a refined aluminum alloy which can obtain a refined aluminum alloy having a small amount to be mixed of impurity metal elements even when a used aluminum alloy product is used as a raw material.SOLUTION: A method for manufacturing a refined aluminum alloy includes: a first heating step of heating a raw material of an aluminum alloy alone at a heating temperature equal to or higher a liquidus temperature of the aluminum alloy and obtaining liquid molten metal; a cooling step of cooling the liquid molten metal at a cooling temperature which is lower than the liquidus temperature and equal to or higher than a solidus temperature of the aluminum alloy, and producing aluminum alloy particles and a sludge and obtaining semi-solidified molten metal; a second heating step of heating the semi-solidified molten metal at a temperature equal to or higher than the liquidus temperature and equal to or lower than a melting temperature of the sludge, melting the aluminum alloy particles to produce refined liquid molten metal and obtaining sludge-containing liquid molten metal; and recovery step of separating the sludge of the sludge-containing liquid molten metal and the refined liquid molten metal, and recovering the refined liquid molten metal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing refined aluminum alloys. [Background technology]

[0002] Aluminum alloys, which are aluminum to which metal elements such as silicon and copper are added, are used in various industrial products. In addition, recovery and reuse of aluminum alloys from used aluminum alloy products is widely practiced. When recovering aluminum alloys from used aluminum alloy products, the used aluminum alloy products are generally heated to produce molten aluminum alloy. This molten aluminum alloy may contain metal fasteners such as screws and rivets used in the aluminum alloy products or metals that have adhered to the aluminum alloy products during use, and may be dissolved as aluminum alloy. For this reason, methods for removing impure metal elements other than the additive metal elements added to the aluminum alloy from the molten aluminum alloy have been studied.

[0003] As a method for removing iron mixed in an aluminum alloy, a method is known in which an iron / manganese-containing material and an aluminum alloy are melted to obtain a molten metal, the obtained molten metal is cooled to crystallize iron compounds, and the crystallized iron compounds are removed (see Patent Document 1). Another method is known in which the molten aluminum alloy is cooled by contacting a cooling body with the molten metal, the intermetallic compounds of impurities are crystallized in the molten metal, the crystallized intermetallic compounds are allowed to fall by gravity, and a refined aluminum solid phase is fixed and grown on the surface of the cooling body, thereby recovering aluminum (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-111808 A [Patent Document 2] Patent No. 3250256 Summary of the Invention [Problem to be solved by the invention]

[0005] When reproducing aluminum alloy products using aluminum alloys recovered from used aluminum alloy products, it is desirable that the composition of the recovered aluminum alloy is equivalent to that of the aluminum alloy used in the aluminum alloy products before use. In other words, when recovering aluminum alloys from used aluminum alloy products, it is desirable to selectively remove only aluminum compounds containing impure metal elements from the molten metal of the used aluminum alloy products. However, in the method using iron- and manganese-containing materials, there is a risk that the iron- and manganese-containing materials will remain in the aluminum alloy. In addition, in the method of adhering and growing a refined aluminum solid phase on the surface of a cooling body, it is difficult to obtain an aluminum alloy containing added metal elements because aluminum, which has a high melting point, is likely to adhere to the surface of the cooling body.

[0006] The present invention aims to provide a method for producing a refined aluminum alloy that can industrially advantageously produce a refined aluminum alloy having a composition equivalent to that of the aluminum alloy used in the aluminum alloy product, with a small amount of impure metal elements mixed in, even when a used aluminum alloy product is used as a raw material. [Means for solving the problem]

[0007] The present inventors have found that the above-mentioned problems can be solved by cooling a molten aluminum alloy containing impure metal elements to generate aluminum alloy particles and sludge in the molten aluminum alloy to obtain a semi-solidified molten aluminum alloy, heating the obtained semi-solidified molten aluminum alloy to melt the aluminum alloy particles without dissolving the sludge, and then separating the sludge from the liquid molten aluminum alloy, and have thus completed the present invention. Therefore, the present invention provides the following.

[0008] (1) A method for producing a refined aluminum alloy, comprising: a first heating step of heating an aluminum alloy raw material alone at a heating temperature equal to or higher than the liquidus temperature of the aluminum alloy to obtain a molten liquid; a cooling step of cooling the molten liquid at a cooling temperature lower than the liquidus temperature and equal to or higher than the solidus temperature of the aluminum alloy to generate aluminum alloy particles and sludge to obtain a semi-solidified molten liquid; a second heating step of heating the semi-solidified molten liquid at a heating temperature equal to or higher than the liquidus temperature and equal to or lower than the melting temperature of the sludge to melt the aluminum alloy particles to generate a refined liquid molten liquid to obtain a sludge-containing liquid molten liquid; and a recovery step of separating the sludge from the refined liquid molten liquid of the sludge-containing liquid molten liquid and recovering the refined liquid molten liquid.

[0009] In the manufacturing method of refined aluminum alloy of (1), since the raw aluminum alloy material is heated alone in the first heating step, foreign matter from the outside is unlikely to be mixed into the obtained liquid molten metal. Furthermore, aluminum alloy impurities including impure metal elements mixed into the raw aluminum alloy material are turned into solid sludge in the cooling step and separated from the molten aluminum alloy in the recovery step. Furthermore, no additive is required to remove the impure metal elements mixed into the raw aluminum alloy material. Therefore, according to the manufacturing method of refined aluminum alloy of (1), even if a used aluminum alloy product is used as the raw aluminum alloy material, a refined aluminum alloy having a composition equivalent to that of the aluminum alloy used in the aluminum alloy product can be industrially advantageously manufactured, and the obtained refined aluminum alloy can be advantageously used as the raw material for the aluminum alloy product.

[0010] (2) The method for producing a refined aluminum alloy according to (1), wherein the content of the aluminum alloy particles in the semi-solidified molten metal obtained in the cooling step is within a range of 10 to 90 mass %.

[0011] According to the method for producing a refined aluminum alloy in (2), the content of aluminum alloy particles in the semi-solidified molten metal obtained in the cooling step is within the above range, so that the aluminum alloy impurities can be more reliably and efficiently produced as sludge, and the composition of the refined aluminum alloy obtained is closer to that of the aluminum alloy used in the aluminum alloy product.

[0012] (3) The method for producing a refined aluminum alloy according to (1) or (2), wherein the cooling temperature in the cooling step is in the range of a temperature that is 40°C lower than the liquidus temperature or more and a temperature that is 19°C lower than the liquidus temperature or less.

[0013] According to the method for producing a refined aluminum alloy in (3), since the cooling temperature in the cooling step is within the above range, the aluminum alloy impurities can be more reliably and efficiently precipitated as sludge, and the composition of the refined aluminum alloy obtained is closer to that of the aluminum alloy used in the aluminum alloy product.

[0014] (4) A method for producing a refined aluminum alloy according to any one of (1) to (3), wherein the heating temperature in the second heating step is within a range of a temperature that is 1°C higher than the liquidus temperature and a temperature that is 129°C higher than the liquidus temperature.

[0015] According to the method for producing a refined aluminum alloy in (4), since the heating temperature in the second heating step is within the above range, it is possible to dissolve the aluminum alloy particles without dissolving the sludge, and therefore the composition of the refined aluminum alloy obtained is closer to that of the aluminum alloy used in the aluminum alloy product.

[0016] (5) A method for producing a refined aluminum alloy according to any one of (1) to (4), wherein in the second heating step, the sludge-containing liquid molten metal is allowed to stand to allow the sludge to settle in the refined liquid molten metal.

[0017] According to the method for producing a refined aluminum alloy in (5), since the sludge is precipitated in the refined liquid molten metal in the second heating step, the sludge and the refined liquid molten metal can be more reliably separated in the recovery step, and therefore the composition of the refined aluminum alloy obtained becomes closer to that of the aluminum alloy used in the aluminum alloy product.

[0018] (6) The method for producing a refined aluminum alloy according to any one of (1) to (5), wherein the raw material of the aluminum alloy is a used aluminum alloy product.

[0019] According to the method for producing a refined aluminum alloy in (6), since a used aluminum alloy product is used as a raw material for the aluminum alloy, resources can be effectively utilized and the burden on the environment can be reduced. Effect of the Invention

[0020] According to the present invention, it is possible to provide a method for producing a refined aluminum alloy, which can industrially advantageously produce a refined aluminum alloy having a composition equivalent to that of the aluminum alloy used in the aluminum alloy product, with a small amount of impure metal elements mixed in, even when a used aluminum alloy product is used as a raw material. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a flow diagram illustrating a method for producing a refined aluminum alloy according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a conceptual diagram illustrating a cooling step in a method for producing a refined aluminum alloy according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a conceptual diagram illustrating a second heating step in a method for producing a refined aluminum alloy according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a flow diagram illustrating a method for producing a refined aluminum alloy according to one embodiment of the present invention, Fig. 2 is a conceptual diagram illustrating a cooling step in the method for producing a refined aluminum alloy according to one embodiment of the present invention, and Fig. 3 is a conceptual diagram illustrating a second heating step.

[0023] As shown in FIG. 1, the method for producing a refined aluminum alloy according to this embodiment includes a first heating step S1, a cooling step S2, a second heating step S3, and a recovery step S4.

[0024] In the method for producing a refined aluminum alloy of this embodiment, a used aluminum alloy product can be used as the aluminum alloy raw material. The aluminum alloy is an alloy in which an additive metal element is added to aluminum. The additive metal element can be, for example, copper, silicon, magnesium, manganese, or zinc. The aluminum alloy product can be, for example, a cast material, a forged material, or a wrought material. The cast material can be a die-cast material. There is no particular limitation on the type of aluminum alloy, and it can be, for example, an Al-Cu alloy, an Al-Si alloy, an Al-Mg alloy, an Al-Mn alloy, an Al-Cu-Si alloy, an Al-Mg-Si alloy, or an Al-Zn-Mg alloy. Examples of the aluminum alloy raw material include ADC1, ADC3, ADC5, ADC6, ADC10, ADC10Z, ADC12, ADC12Z, and ADC14. The aluminum alloy raw material can be used alone or in combination of two or more types.

[0025] The first heating step S1 is a step of heating the aluminum alloy raw material alone at a heating temperature equal to or higher than the liquidus temperature to obtain a liquid molten metal. The heating temperature of the aluminum alloy raw material in the first heating step S1 is not particularly limited as long as it is equal to or higher than the liquidus temperature of the aluminum alloy. For example, when the aluminum alloy raw material is ADC12 (liquidus temperature: 610°C), the heating temperature may be equal to or higher than 610°C.

[0026] There is no particular limitation on the heating device for heating the aluminum alloy raw material, and for example, a known device used as a melting furnace for aluminum alloys, such as a rotary furnace, can be used.

[0027] The cooling step S2 is a step of cooling the liquid molten metal at a cooling temperature lower than the liquidus temperature and equal to or higher than the solidus temperature to generate aluminum alloy particles and sludge, thereby obtaining a semi-solidified molten metal.

[0028] As shown in FIG. 2, in the cooling step S2, when the liquid molten metal 2 in the heating device 1 is cooled to a temperature below the liquidus temperature, aluminum alloy particles 3 containing additive metal elements are generated. The generation of the aluminum alloy particles 3 reduces the amount of aluminum alloy in the liquid molten metal 2, and the concentration of aluminum alloy impurities containing impure metal elements increases relatively. The aluminum alloy impurities are, for example, intermetallic compounds containing impure metal elements and aluminum. When the concentration of the aluminum alloy impurities in the liquid molten metal 2 increases, the aluminum alloy impurities precipitate and sludge 4 is generated. The liquid molten metal 2 may be cooled while stirring the liquid molten metal 2, or may not be stirred. Examples of impure metal elements include iron, chromium, nickel, and silicon.

[0029] The cooling temperature in the cooling step S2 may be, for example, within a range of a temperature lower than the liquidus temperature by 40° C. or more and a temperature lower than the liquidus temperature by 19° C. For example, when the aluminum alloy raw material is ADC12, the cooling temperature may be within a range of 570 to 591° C. The cooling time is not particularly limited and may be, for example, 30 minutes or more.

[0030] The content of the aluminum alloy particles 3 in the semi-solidified molten metal obtained in the cooling step S2 may be, for example, within the range of 10 to 90 mass %. The content of the aluminum alloy particles 3 can be calculated from the liquidus temperature, solidus temperature, and cooling temperature in the phase equilibrium diagram of the aluminum alloy.

[0031] The second heating step S3 is a step of heating the semi-solidified molten metal at a temperature equal to or higher than the liquidus temperature and equal to or lower than the melting temperature of the sludge to melt the aluminum alloy particles without melting the sludge, thereby obtaining a sludge-containing liquid molten metal.

[0032] As shown in Fig. 3, in the second heating step S3, the semi-solidified molten metal obtained in the cooling step S2 is heated to a temperature equal to or higher than the liquidus temperature, so that aluminum alloy particles not containing aluminum alloy impurities are melted to generate a refined liquid molten metal 2a. In addition, since the heating temperature is set to a temperature equal to or lower than the melting temperature of the sludge 4, the sludge 4 is not easily dissolved in the refined liquid molten metal 2a. The semi-solidified molten metal may be heated while stirring the semi-solidified molten metal or may be heated without stirring. In the second heating step S3, the refined liquid molten metal 2a containing the sludge 4 may be allowed to stand, so that the sludge 4 is allowed to settle and be deposited on the bottom of the heating device 1.

[0033] The heating temperature in the second heating step may be, for example, within a range of a temperature 1° C. higher than the liquidus temperature or more and a temperature 129° C. higher than the liquidus temperature or less. For example, when the aluminum alloy raw material is ADC12 and the sludge is an intermetallic compound containing iron and aluminum, the heating temperature may be within a range of 611 to 739° C. The heating time is not particularly limited and may be, for example, 30 minutes or more.

[0034] The recovery step S4 is a step of separating the sludge from the refined liquid molten metal of the sludge-containing liquid molten metal, and recovering the refined liquid molten metal. The method for recovering the refined liquid molten metal is not particularly limited, and various solid-liquid separation methods such as filtration, decantation, and centrifugation can be used.

[0035] The refined liquid molten metal recovered in the recovery step S4 may be solidified once to form an aluminum alloy ingot. The refined liquid molten metal may also be directly used as a raw material for casting, forging, or wrought materials. Furthermore, additive metal elements may be added to the refined liquid molten metal as necessary.

[0036] In the manufacturing method of the refined aluminum alloy of the present embodiment configured as described above, the raw aluminum alloy material is heated alone in the first heating step S1, so that foreign matter from the outside is unlikely to be mixed into the obtained liquid molten metal. Furthermore, the aluminum alloy impurities including impure metal elements mixed in the raw aluminum alloy material are turned into solid sludge in the cooling step S2 and separated from the molten aluminum alloy in the recovery step S4. Furthermore, no additive is required to remove the impure metal elements mixed in the raw aluminum alloy material. Therefore, according to the manufacturing method of the refined aluminum alloy of the present embodiment, a refined aluminum alloy having a composition equivalent to that of the aluminum alloy used in the used aluminum alloy product used as the raw aluminum alloy material can be industrially advantageously manufactured, and the obtained refined aluminum alloy can be advantageously used as the raw material of the aluminum alloy product.

[0037] In the method for producing a refined aluminum alloy according to the present embodiment, when the content of aluminum alloy particles in the semi-solidified molten metal obtained in the cooling step S2 is within the above range, the aluminum alloy impurities can be more reliably and efficiently produced as sludge. Therefore, the composition of the refined aluminum alloy obtained is closer to that of the aluminum alloy used in the aluminum alloy product. Furthermore, when the cooling temperature in the cooling step S2 is within the above range, the aluminum alloy impurities can be more reliably and efficiently precipitated as sludge. Therefore, the composition of the refined aluminum alloy obtained is closer to that of the aluminum alloy used in the aluminum alloy product.

[0038] In the method for producing a refined aluminum alloy according to the present embodiment, when the heating temperature in the second heating step S3 is within the above range, the aluminum alloy particles can be dissolved without dissolving the sludge. Therefore, the composition of the refined aluminum alloy obtained is closer to that of the aluminum alloy used in the aluminum alloy product. In addition, when the sludge-containing liquid molten metal is left to stand in the second heating step S3 to allow the sludge to settle in the refined liquid molten metal, the sludge and the refined liquid molten metal can be separated more reliably in the recovery step. Therefore, the composition of the refined aluminum alloy obtained is closer to that of the aluminum alloy used in the aluminum alloy product.

[0039] In the method for producing a refined aluminum alloy of this embodiment, a used aluminum alloy product is used as the aluminum alloy raw material, which enables effective use of resources and reduces the burden on the environment.

[0040] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the above embodiment may be modified as appropriate within the scope of the spirit of the present invention. For example, in this embodiment, used aluminum alloy products are used as the aluminum alloy raw material, but the aluminum alloy raw material is not limited to this. A raw material mixture containing metallic aluminum and an additive metal element may be used as the aluminum alloy raw material. The additive metal element may be, for example, copper, silicon, magnesium, manganese, or zinc. In this case, impurities contained in metallic aluminum and the additive metal element can be removed as sludge. EXAMPLES

[0041] [Example 1] A used aluminum alloy die-cast product (ADC12, liquidus temperature: 610°C) was prepared as an aluminum alloy raw material. The prepared ADC12 was placed in a rotary furnace and heated at 650°C to obtain a molten liquid (first heating step). A portion of the obtained molten liquid was extracted, solidified, and its composition was analyzed. The results are shown in Table 1 below as the composition of the used aluminum alloy. Table 1 also shows the composition of the aluminum alloy components of the aluminum alloy die-cast product before use as the composition of the aluminum alloy before use.

[0042] The liquid molten metal was then cooled at 580°C for 30 minutes in a stationary state to obtain a semi-solidified molten metal containing aluminum alloy particles and sludge (cooling step). The content of aluminum alloy particles in the semi-solidified molten metal calculated from the liquidus temperature and solidus temperature in the phase equilibrium diagram of the aluminum alloy and the temperature of the liquid molten metal (580°C) was 63 mass%.

[0043] Next, the semi-solidified molten metal was heated at 620°C for 30 minutes in a stationary state to melt the aluminum alloy particles (second heating step). Sludge was deposited at the bottom of the obtained liquid molten metal. Next, the liquid molten metal and the sludge were separately collected from the rotary furnace (collection step). As a result of analyzing the composition of the collected sludge, it was confirmed that the sludge was an intermetallic compound containing iron and aluminum. In addition, the melting temperature of the sludge was 740°C. The melting temperature of the sludge was measured as follows. The sludge was placed in a heat-resistant container with a thermocouple and put into an electric furnace. Next, the sludge was heated while measuring the temperature of the sludge using a thermocouple. The temperature at which the sludge melted was taken as the melting temperature.

[0044] The recovered liquid molten metal was allowed to cool to obtain an aluminum alloy. The yield of the obtained aluminum alloy was 96%. A portion of the obtained aluminum alloy was sampled and its composition was analyzed. The results are shown in Table 1 below as the content of components in the refined aluminum alloy. Table 1 also shows the amount of change in the component content calculated by the following formula (1) and the rate of change in the component content calculated by the following formula (2). Change in component content (mass%) = component content (mass%) of refined aluminum alloy - component content (mass%) of used aluminum alloy (1) Change rate of component content (%) = [Component content of refined aluminum alloy (mass%) - Component content of aluminum alloy before use (mass%)] / Component content of aluminum alloy before use (mass%) × 100 (2)

[0045] [Table 1]

[0046] From the change in the component contents in Table 1, it was confirmed that the contents of transition metals such as iron, manganese, and chromium could be significantly reduced without significantly changing the contents of copper and silicon, which are the main additive metal elements in ADC12, according to Example 1. In addition, from the change rate of the component contents, it was confirmed that the obtained refined aluminum alloy had a composition equivalent to that of the aluminum alloy before use. [Explanation of symbols]

[0047] 1 Heating device 2 Liquid molten metal 2a Refined liquid metal 3. Aluminum alloy particles 4. Sludge

Claims

1. a first heating step of heating an aluminum alloy raw material alone at a heating temperature equal to or higher than the liquidus temperature of the aluminum alloy to obtain a molten metal; a cooling step of cooling the liquid molten metal at a cooling temperature lower than the liquidus temperature and equal to or higher than the solidus temperature of the aluminum alloy to generate aluminum alloy particles and sludge to obtain a semi-solidified molten metal; a second heating step of heating the semi-solidified molten metal at a heating temperature equal to or higher than the liquidus temperature and equal to or lower than the melting temperature of the sludge to melt the aluminum alloy particles and generate a refined liquid molten metal to obtain a sludge-containing liquid molten metal; and a recovery step of separating the sludge from the sludge-containing liquid molten metal and recovering the refined liquid molten metal.

2. 2. The method for producing a refined aluminum alloy according to claim 1, wherein the content of the aluminum alloy particles in the semi-solidified molten metal obtained in the cooling step is within a range of 10 to 90 mass %.

3. 3. The method for producing a refined aluminum alloy according to claim 1, wherein the cooling temperature in the cooling step is within a range of a temperature that is 40° C. lower than the liquidus temperature and a temperature that is 19° C. lower than the liquidus temperature.

4. 3. The method for producing a refined aluminum alloy according to claim 1, wherein the heating temperature in the second heating step is within a range of a temperature higher than the liquidus temperature by 1° C. or more and a temperature higher than the liquidus temperature by 129° C. or less.

5. 3. The method for producing a refined aluminum alloy according to claim 1, wherein in the second heating step, the sludge-containing liquid molten metal is allowed to stand still to cause the sludge to settle in the refined liquid molten metal.

6. The method for producing a refined aluminum alloy according to claim 1 or 2, wherein the raw material of the aluminum alloy is a used aluminum alloy product.

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