Method for producing refined aluminum alloy

Abstract

The problem to be solved by the present invention is to provide a method for producing a refined aluminum alloy with which it is possible to obtain a refined aluminum alloy in which the mixing amount of impurity metal elements is small even if used aluminum alloy products are used as raw materials. In order to solve the problem, the present invention provides a method for producing a refined aluminum alloy, which comprises: a first heating step for obtaining a liquid molten metal by individually heating an aluminum alloy starting material at a heating temperature that is not less than the liquidus temperature of the aluminum alloy; a cooling step for cooling the liquid molten metal at a cooling temperature that is lower than the liquidus temperature and equal to or higher than the solidus temperature of the aluminum alloy to produce aluminum alloy particles and slag, thereby obtaining a semi-solidified molten metal; a second heating step in which the semi-solidified molten metal is heated at a heating temperature that is not less than the liquidus temperature but not more than the melting temperature of the slag to melt the aluminum alloy particles, thereby producing a refined liquid molten metal and obtaining a liquid molten metal containing the slag; and a recovery step in which the slag of the slag-containing liquid molten metal is separated from the refined liquid molten metal, and the refined liquid molten metal is recovered.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a refined aluminum alloy. Background Art

[0002] Aluminum alloys, in which metal elements such as silicon or copper are added to aluminum, are used in various industrial products. In addition, aluminum alloys are widely recovered from used aluminum alloy products and reused. When recovering aluminum alloys from used aluminum alloy products, the used aluminum alloy products are generally heated to form molten metal of the aluminum alloy. In the molten metal of the aluminum alloy, metal fasteners such as screws or rivets used in the aluminum alloy products or metals attached during the use of the aluminum alloy products are sometimes mixed and melted as aluminum alloy. Therefore, a method is being explored for removing impurity metal elements other than the added metal elements added to the aluminum alloy from the molten metal of the aluminum alloy.

[0003] As a method for removing iron mixed in an aluminum alloy, a method is known in which a molten metal is obtained by melting an iron / manganese-containing material and an aluminum alloy, and the obtained molten metal is cooled to crystallize iron compounds, and the crystallized iron compounds are removed (see Patent Document 1). In addition, a method is known in which a cooling body is brought into contact with the molten metal of the aluminum alloy to cool the molten metal, to crystallize intermetallic compounds of impurities in the molten metal, to make the crystallized intermetallic compounds fall freely, and to make a refined aluminum solid phase adhere and grow on the surface of the cooling body to recover aluminum (see Patent Document 2).

[0004] [Prior Technical Literature]

[0005] (Patent Document)

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-111808

[0007] Patent Document 2: Japanese Patent No. 3250256 Summary of the invention

[0008] [Problems to be solved by the invention]

[0009] When aluminum alloys recovered from used aluminum alloy products are used to re-produce aluminum alloy products, it is expected that the composition of the recovered aluminum alloy is the same as that used in the aluminum alloy products before use. That is, when aluminum alloys are recovered from used aluminum alloy products, it is expected that only aluminum compounds containing impurity metal elements are selectively removed from the molten metal of the used aluminum alloy products. However, in the method using iron / manganese containing materials, the iron / manganese containing materials may remain in the aluminum alloy. In addition, in the method of making the refined aluminum solid phase adhere to the surface of the cooling body, since aluminum with a high melting point is easily adhered to the surface of the cooling body, it is not easy to obtain an aluminum alloy containing added metal elements.

[0010] The object of the present invention is to provide a method for manufacturing a refined aluminum alloy, which can be used to industrially advantageously manufacture a refined aluminum alloy, in which the amount of impurity metal elements mixed in is small even if used aluminum alloy products are used as raw materials, and the alloy has the same composition as the aluminum alloy previously used in the aluminum alloy product.

[0011] [Technical means to solve the problem]

[0012] The present inventors have found that the above-mentioned problems can be solved by cooling a molten metal of an aluminum alloy containing impurity metal elements, generating aluminum alloy particles and slag in the molten metal to obtain a semi-solidified molten metal, heating the obtained semi-solidified molten metal to melt the aluminum alloy particles without melting the slag, and then separating the slag from the liquid molten metal, thereby completing the present invention. Therefore, the present invention provides the following contents.

[0013] (1) A method for producing a refined aluminum alloy, comprising: a first heating step, heating a raw material of an aluminum alloy alone at a heating temperature above the liquidus temperature of the aluminum alloy to obtain a liquid molten metal; a cooling step, cooling the liquid molten metal at a cooling temperature lower than the liquidus temperature and above the solidus temperature of the aluminum alloy to generate aluminum alloy particles and slag to obtain a semi-solidified molten metal; a second heating step, heating the semi-solidified molten metal at a heating temperature above the liquidus temperature and below the melting temperature of the slag to melt the aluminum alloy particles, thereby generating a refined liquid molten metal to obtain a slag-containing liquid molten metal; and a recovery step, separating the slag of the slag-containing liquid molten metal from the refined liquid molten metal and recovering the refined liquid molten metal.

[0014] In the method for manufacturing a refined aluminum alloy of (1), since the raw material of the aluminum alloy is heated separately by the first heating step, foreign matter from the outside is not easily mixed into the obtained liquid molten metal. In addition, aluminum alloy impurities containing impurity metal elements mixed in the raw material of the aluminum alloy are formed into solid slag by the cooling step, and are separated from the molten metal of the aluminum alloy by the recovery step. In addition, no additive is required for removing the impurity metal elements mixed in the raw material of the aluminum alloy. Therefore, according to the method for manufacturing a refined aluminum alloy of (1), even if a used aluminum alloy product is used as the raw material of the aluminum alloy, a refined aluminum alloy having the same composition as that of the aluminum alloy previously used in the aluminum alloy product can be manufactured industrially advantageously, and the obtained refined aluminum alloy can be advantageously used as the raw material of the aluminum alloy product.

[0015] (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 in the range of 10 to 90% by mass.

[0016] According to the method for producing a refined aluminum alloy of (2), since the content of aluminum alloy particles in the semi-solidified molten metal obtained in the cooling step is within the above range, aluminum alloy impurities can be more reliably and efficiently generated as slag. Therefore, the composition of the obtained refined aluminum alloy is closer to the aluminum alloy previously used in aluminum alloy products.

[0017] (3) A method for producing a refined aluminum alloy according to (1) or (2), wherein the cooling temperature in the cooling step is within a range of not less than a temperature 40°C lower than the liquidus temperature and not more than a temperature 19°C lower than the liquidus temperature.

[0018] According to the method for producing a refined aluminum alloy of (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 slag. Therefore, the composition of the obtained refined aluminum alloy is closer to the aluminum alloy previously used in aluminum alloy products.

[0019] (4) A method for producing a refined aluminum alloy according to any one of (1) to (3), wherein the heating temperature of the second heating step is within a range of from 1°C higher than the liquidus temperature to 129°C higher than the liquidus temperature.

[0020] According to the method for producing a refined aluminum alloy of (4), since the heating temperature in the second heating step is within the above range, the aluminum alloy particles can be melted without melting the slag. Therefore, the composition of the obtained refined aluminum alloy is closer to the aluminum alloy previously used in aluminum alloy products.

[0021] (5) The method for producing a refined aluminum alloy according to any one of (1) to (4), wherein, in the second heating step, the slag-containing liquid molten metal is left to stand to allow the slag to settle in the refined liquid molten metal.

[0022] According to the method for producing a refined aluminum alloy of (5), since the slag is deposited in the refined liquid molten metal by the second heating step, the slag and the refined liquid molten metal can be more reliably separated by the recovery step. Therefore, the composition of the obtained refined aluminum alloy is closer to the aluminum alloy previously used in aluminum alloy products.

[0023] (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.

[0024] According to the method for producing a refined aluminum alloy of (6), since used aluminum alloy products are used as raw materials for the aluminum alloy, resources can be effectively utilized and the load on the environment can be reduced.

[0025] (Effects of the Invention)

[0026] According to the present invention, a method for manufacturing a refined aluminum alloy can be provided, which can be used to industrially advantageously manufacture a refined aluminum alloy in which the amount of impurity metal elements mixed in is small even if used aluminum alloy products are used as raw materials, and the alloy has the same composition as the aluminum alloy previously used in the aluminum alloy product. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flowchart for explaining a method for producing a refined aluminum alloy according to one embodiment of the present invention.

[0028] Figure 2 This is a conceptual diagram for explaining a cooling step in a method for producing a refined aluminum alloy according to an embodiment of the present invention.

[0029] Figure 3 This is a conceptual diagram for explaining the second heating step in the method for producing a refined aluminum alloy according to one embodiment of the present invention. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0031] Figure 1 This is a flowchart for explaining a method for producing a refined aluminum alloy according to one embodiment of the present invention. Figure 2 This is a conceptual diagram for explaining a cooling step in a method for producing a refined aluminum alloy according to an embodiment of the present invention. Figure 3 This is a conceptual diagram for explaining the second heating step.

[0032] like Figure 1 As shown, the method for producing a refined aluminum alloy according to the present embodiment includes a first heating step S1 , a cooling step S2 , a second heating step S3 , and a recovery step S4 .

[0033] In the method for manufacturing a refined aluminum alloy of the present embodiment, a used aluminum alloy product can be used as an aluminum alloy raw material. An aluminum alloy is an alloy in which an additive metal element is added to aluminum. As an additive metal element, for example, copper, silicon, magnesium, manganese, and zinc can be used. An aluminum alloy product can also be, for example, a casting material, a forging material, or an extended material. The casting material can also be a die-casting material. There is no particular restriction on the type of aluminum alloy, for example, it can also be 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, and an Al-Zn-Mg alloy. Examples of aluminum alloy raw materials include ADC1, ADC3, ADC5, ADC6, ADC10, ADC10Z, ADC12, ADC12Z, and ADC14. Aluminum alloy raw materials can be used alone or in combination of two or more.

[0034] The first heating step S1 is a step of heating the aluminum alloy raw material alone at a heating temperature above 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 above the liquidus temperature of the aluminum alloy. For example, when the aluminum alloy raw material is ADC12 (liquidus temperature: 610°C), the heating temperature can be above 610°C.

[0035] The heating device for heating the aluminum alloy raw material is not particularly limited, and for example, a known device used as a melting furnace for aluminum alloys, such as a rotary furnace, can be used.

[0036] The cooling step S2 is a step of cooling the liquid molten metal at a cooling temperature lower than the liquidus temperature and higher than the solidus temperature to generate aluminum alloy particles and slag to obtain a semi-solidified molten metal.

[0037] like Figure 2As shown, when the liquid molten metal 2 in the heating device 1 is cooled to a temperature lower than the liquidus temperature by the cooling step S2, aluminum alloy particles 3 containing added metal elements are generated. Due to the generation of aluminum alloy particles 3, the amount of aluminum alloy in the liquid molten metal 2 is reduced, and the concentration of aluminum alloy impurities containing impurity metal elements is relatively increased. Aluminum alloy impurities are, for example, intermetallic compounds containing impurity metal elements and aluminum. When the concentration of aluminum alloy impurities in the liquid molten metal 2 increases, aluminum alloy impurities are precipitated to generate slag 4. The cooling of the liquid molten metal 2 can be carried out by stirring the liquid molten metal 2 or without stirring. Examples of impurity metal elements include iron, chromium, nickel, and silicon.

[0038] The cooling temperature of the cooling step S2 may be, for example, in the range of 40° C. or higher and 19° C. or lower than the liquidus temperature. For example, when the aluminum alloy raw material is ADC12, the cooling temperature may be in the range of 570° C. to 591° C. The cooling time is not particularly limited, and may be, for example, 30 minutes or more.

[0039] The content of the aluminum alloy particles 3 in the semi-solidified molten metal obtained in the cooling step S2 may be, for example, in the range of 10 to 90 mass %. The content of the aluminum alloy particles 3 can be calculated from the liquidus temperature and the solidus temperature of the phase equilibrium diagram of the aluminum alloy and the cooling temperature.

[0040] The second heating step S3 is a step of heating the semi-solidified molten metal at a heating temperature not less than the liquidus temperature and not more than the melting temperature of the slag to melt the aluminum alloy particles without melting the slag, thereby obtaining a liquid molten metal containing slag.

[0041] like Figure 3 As shown, in the second heating step S3, the semi-solidified molten metal obtained in the cooling step S2 is heated at a temperature above the liquidus temperature, so that the aluminum alloy particles that do not contain aluminum alloy impurities melt to generate refined liquid molten metal 2a. In addition, since the heating temperature is set below the melting temperature of the slag 4, the slag 4 is not easily dissolved in the refined liquid molten metal 2a. The heating of the semi-solidified molten metal can be carried out by stirring the semi-solidified molten metal or by not stirring. In the second heating step S3, the refined liquid molten metal 2a containing the slag 4 can also be allowed to settle and accumulate at the bottom of the heating device 1 by leaving it still.

[0042] The heating temperature of the second heating step may be, for example, in the range of 1°C higher than the liquidus temperature and 129°C higher than the liquidus temperature. For example, when the aluminum alloy raw material is ADC12 and the slag is an intermetallic compound containing iron and aluminum, the heating temperature may be in the range of 611°C to 739°C. The heating time is not particularly limited and may be, for example, 30 minutes or more.

[0043] The recovery step S4 is a step of separating the slag of the liquid molten metal containing slag from the refined liquid molten metal and recovering the refined liquid molten metal.

[0044] The method for recovering the refined liquid molten metal is not particularly limited, and various solid-liquid separation methods such as filtration, decantation, and centrifugal separation can be used.

[0045] The refined liquid molten metal recovered in the recovery step S4 may be temporarily solidified to form an aluminum alloy ingot. In addition, the refined liquid molten metal may be directly used as a raw material for casting, forging, and ductile materials. Furthermore, additional metal elements may be added to the refined liquid molten metal as needed.

[0046] In the method for manufacturing a refined aluminum alloy of the present embodiment constructed as above, since the raw material of the aluminum alloy is heated separately by the first heating step S1, foreign matter from the outside is not easily mixed into the obtained liquid molten metal. In addition, aluminum alloy impurities containing impurity metal elements mixed in the aluminum alloy raw material are formed into solid slag by the cooling step S2, and are separated from the molten metal of the aluminum alloy by the recovery step S4. In addition, additives for removing impurity metal elements mixed in the raw material of the aluminum alloy are not required. Therefore, according to the method for manufacturing a refined aluminum alloy of the present embodiment, a refined aluminum alloy having the same composition as that of an aluminum alloy used in a previously used aluminum alloy product used as an aluminum alloy raw material can be manufactured industrially; the obtained refined aluminum alloy can be advantageously used as a raw material for the aluminum alloy product.

[0047] In the method for producing a refined aluminum alloy of 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, aluminum alloy impurities can be more reliably and efficiently generated as slag. Therefore, the composition of the obtained refined aluminum alloy is closer to the aluminum alloy previously used in aluminum alloy products. In addition, when the cooling temperature in the cooling step S2 is within the above range, aluminum alloy impurities can be more reliably and efficiently precipitated as slag. Therefore, the composition of the obtained refined aluminum alloy is closer to the aluminum alloy previously used in aluminum alloy products.

[0048] In the method for manufacturing a refined aluminum alloy of the present embodiment, when the heating temperature in the second heating step S3 is within the above range, the aluminum alloy particles can be melted without melting the slag. Therefore, the composition of the obtained refined aluminum alloy is closer to the aluminum alloy previously used in aluminum alloy products. In addition, when the liquid molten metal containing slag is allowed to stand by the second heating step S3 and the slag is allowed to settle in the refined liquid molten metal, the slag and the refined liquid molten metal can be separated more reliably by the recovery step. Therefore, the composition of the obtained refined aluminum alloy is closer to the aluminum alloy previously used in aluminum alloy products.

[0049] In the method for producing a refined aluminum alloy of the present embodiment, since used aluminum alloy products are used as aluminum alloy raw materials, effective utilization of resources can be achieved, and thus the load on the environment can be reduced.

[0050] As mentioned above, although embodiment of this invention was demonstrated, this invention is not limited to the said embodiment, and the said embodiment can be modified suitably within the range of the summary of this invention.

[0051] For example, in this embodiment, a used aluminum alloy product is used as the aluminum alloy raw material, but the aluminum alloy raw material is not limited thereto. As the aluminum alloy raw material, a raw material mixture containing metal aluminum and an added metal element may also be used. As the added metal element, for example, copper, silicon, magnesium, manganese, and zinc may be used. In this case, impurities contained in the metal aluminum or the added metal element may be removed as slag.

[0052] [Example]

[0053] (Example 1)

[0054] As an aluminum alloy raw material, a used aluminum alloy die-casting product (ADC12, liquidus temperature: 610°C) was prepared. The prepared ADC12 was put into a rotary furnace and heated at 650°C to obtain a liquid molten metal (first heating step). A portion of the obtained liquid molten metal was taken out, solidified, and its composition was analyzed. The results are shown in the following Table 1 as the composition of the used aluminum alloy. In addition, in Table 1, the composition of the components of the aluminum alloy of the aluminum alloy die-casting product before use is recorded as the composition of the aluminum alloy before use.

[0055] Then, the liquid molten metal was cooled at 580°C for 30 minutes in a static state to obtain a semi-solidified molten metal containing aluminum alloy particles and slag (cooling process). The content of aluminum alloy particles in the semi-solidified molten metal calculated from the liquidus temperature and solidus temperature of the phase equilibrium diagram of the aluminum alloy and the temperature of the liquid molten metal (580°C) was 63% by mass.

[0056] Then, the semi-solidified molten metal is heated at 620°C for 30 minutes in a static state to melt the aluminum alloy particles (second heating process). Slag is deposited at the bottom of the obtained liquid molten metal. Then, the liquid molten metal and the slag are recovered separately from the rotary furnace (recovery process). The composition of the recovered slag was analyzed, and the results confirmed that the slag is an intermetallic compound containing iron and aluminum. In addition, the melting temperature of the slag is 740°C. In addition, the melting temperature of the slag is determined as follows. The slag is contained in a heat-resistant container with a thermocouple and put into an electric furnace. Then, the slag is heated while the temperature of the slag is measured using a thermocouple. The temperature at which the slag melts is taken as the melting temperature.

[0057] The recovered molten metal was cooled to obtain an aluminum alloy. The yield of the obtained aluminum alloy was 96%. A portion of the obtained aluminum alloy was collected and its composition was analyzed. The results are shown in Table 1 below as the content of the components of the refined aluminum alloy. In addition, Table 1 shows the change in the component content calculated by the following formula (1) and the change rate of the component content calculated by the following formula (2).

[0058] Change in component content (mass %) = content of component in refined aluminum alloy (mass %) - content of component in used aluminum alloy (mass %) (1)

[0059] Change rate of component content (%) = [content of component in refined aluminum alloy (mass %) - content of component in aluminum alloy before use (mass %)] / content of component in aluminum alloy before use (mass %) × 100 (2)

[0060] [Table 1]

[0061]

[0062] From the changes in the component contents in Table 1, it was confirmed that according to Example 1, the contents of transition metals such as iron, manganese, and chromium can be significantly reduced without significantly changing the contents of copper or silicon, which are the main additive metal elements of ADC12. In addition, from the change rates of the component contents, it was confirmed that the obtained refined aluminum alloy had the same composition as the aluminum alloy before use.

[0063] Reference numerals

[0064] 1 Heating device

[0065] 2 liquid molten metal

[0066] 2a Refining liquid molten metal

[0067] 3Aluminum alloy particles

[0068] 4 Slag

Claims

1. A method for producing a refined aluminum alloy, comprising: In a first heating step, a raw material of the aluminum alloy is heated alone at a heating temperature higher than the liquidus temperature of the aluminum alloy to obtain a liquid molten metal; A cooling step of cooling the liquid molten metal at a cooling temperature lower than the liquidus temperature and higher than the solidus temperature of the aluminum alloy to generate aluminum alloy particles and slag to obtain a semi-solidified molten metal; a second heating step of heating the semi-solidified molten metal at a heating temperature that is higher than the liquidus temperature and lower than the melting temperature of the slag to melt the aluminum alloy particles, thereby generating a refined liquid molten metal to obtain a liquid molten metal containing slag; and The recovery step is to separate the slag of the slag-containing liquid molten metal from the refined liquid molten metal and recover the refined liquid molten metal.

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 in the range of 10 to 90% by mass.

3. The method for producing a refined aluminum alloy according to claim 1 or 2, wherein: The cooling temperature in the cooling step is within a range of not less than a temperature 40° C. lower than the liquidus temperature and not more than a temperature 19° C. lower than the liquidus temperature.

4. The method for producing a refined aluminum alloy according to claim 1 or 2, wherein: The heating temperature in the second heating step is within a range of not less than a temperature 1° C. higher than the liquidus temperature and not more than a temperature 129° C. higher than the liquidus temperature.

5. The method for producing a refined aluminum alloy according to claim 1 or 2, wherein: In the second heating step, the slag-containing liquid molten metal is left to stand to allow the slag 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 aforementioned aluminum alloy is a used aluminum alloy product.

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