Method for producing aluminum ingot

Abstract

To provide a method for producing an aluminum alloy ingot capable of producing aluminum alloy ingots with low copper content from aluminum scraps.SOLUTION: A method for producing an aluminum alloy ingot includes: maintaining a temperature of aluminum scrap containing copper pieces and aluminum alloy, for over 30 minutes, at a temperature above 450°C and below a solidus temperature of the aluminum alloy; then, setting a state of the aluminum scrap to a partially molten state where the temperature is higher than the liquidus temperature of the aluminum alloy, and the copper pieces are solid and the aluminum alloy is molten; then, removing dross containing the copper pieces from the aluminum scrap in the partially molten state; and then, cooling the remaining portion of the aluminum scrap after dross removal.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a method for producing an aluminum alloy ingot. [Background technology]

[0002] In order to realize a sustainable society, there is a need to reduce CO2 emissions. Aluminum is used in a variety of industrial equipment and products. When aluminum alloy ingots are produced from aluminum scrap, CO2 emissions can be reduced by 97% compared to when virgin aluminum ingots are produced from bauxite.

[0003] Aluminum scrap contains multiple types of impurities. In order to produce aluminum alloy ingots from aluminum scrap, it is necessary to separate the impurities contained in the aluminum scrap.

[0004] Patent Document 1 discloses a recycling method for separating aluminum and copper from waste air conditioners. Patent Document 2 discloses a method for refining aluminum. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-172728 A [Patent Document 2] Japanese Patent Application Publication No. 10-130746 Summary of the Invention [Problem to be solved by the invention]

[0006] Among impurities contained in aluminum scrap, it has been particularly difficult to separate copper. In one aspect of the present disclosure, it is preferable to provide a method for producing an aluminum alloy ingot having a low copper content from aluminum scrap. [Means for solving the problem]

[0007] One aspect of the present disclosure is a method for producing an aluminum alloy ingot, comprising: maintaining a temperature of aluminum scrap containing copper flakes and an aluminum alloy at 450°C or higher and lower than the solidus temperature of the aluminum alloy for 30 minutes or more; setting the state of the aluminum scrap at a temperature higher than the liquidus temperature of the aluminum alloy, in which the copper flakes are solid and the aluminum alloy is molten; removing a slag removal target containing the copper flakes from the aluminum scrap in the partially molten state; and cooling a portion of the aluminum scrap that remains after the slag removal target has been removed.

[0008] According to a method for producing an aluminum alloy ingot that is one aspect of the present disclosure, an aluminum alloy ingot having a low copper content can be produced from aluminum scrap that contains copper flakes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Exemplary embodiments of the present disclosure will now be described. 1. Manufacturing method of aluminum alloy ingot (1) Aluminum scrap In the method for producing an aluminum alloy ingot according to the present disclosure, aluminum scrap is used. The aluminum scrap includes copper flakes and an aluminum alloy. The aluminum scrap may or may not include components that are neither copper flakes nor aluminum alloys.

[0010] The copper pieces are members whose main component is copper. The copper pieces may or may not contain components other than copper. The shape of the copper pieces is not particularly limited. Examples of the shape of the copper pieces include tubular, granular, linear, plate, and irregular shapes. When the mass of the aluminum scrap is 100 parts by mass, the mass of the copper pieces is, for example, 0.2 parts by mass or more and 10.0 parts by mass or less. The aluminum scrap contains, for example, a plurality of copper pieces. For example, the plurality of copper pieces are dispersed or unevenly distributed in the aluminum scrap.

[0011] (2) Preheating In the manufacturing method of the aluminum alloy ingot of the present disclosure, aluminum scrap is preheated. The temperature of the aluminum scrap during preheating (hereinafter referred to as preheating temperature) is 450°C or higher and lower than the solidus temperature of the aluminum alloy. The time during which the temperature of the aluminum scrap is the preheating temperature (hereinafter referred to as preheating time) is 30 minutes or longer.

[0012] The preheating temperature is preferably 500° C. or higher, more preferably 640° C. or higher. The higher the preheating temperature is within the range below the solidus temperature of the aluminum alloy, the lower the copper content in the produced aluminum alloy ingot. The preheating temperature may be constant or may increase over time.

[0013] The preheating time is preferably 50 minutes or more, more preferably 300 minutes or more. The longer the preheating time, the lower the copper content in the produced aluminum alloy ingot. The preheating time is preferably 400 minutes or less.

[0014] The preheating is preferably performed in the atmosphere. Examples of the device for heating the aluminum scrap in the preheating include an electric furnace, a rotary kiln, a reverberatory furnace, and a rotary furnace. (3) Partially molten state In the manufacturing method of the aluminum alloy ingot disclosed herein, after preheating, the aluminum scrap is in a partially molten state, the temperature of the aluminum scrap is higher than the liquidus temperature of the aluminum alloy, and the copper pieces are solid and the aluminum alloy is molten.

[0015] In the partially molten state, all of the copper flakes contained in the original aluminum scrap may be solid, or some of the copper flakes may be solid, or some of the copper flakes may be dissolved in the aluminum alloy. In the partially molten state, the copper pieces come into contact with the molten aluminum alloy. The time during which the copper pieces come into contact with the molten aluminum alloy (hereinafter referred to as the contact time) is preferably within 10 minutes. The shorter the contact time, the lower the copper content in the produced aluminum alloy ingot.

[0016] In the partially molten state, the temperature of the aluminum scrap is, for example, 700°C or more, or 740°C or more. The state of the aluminum scrap immediately before it becomes partially molten is, for example, a state in which the molten aluminum alloy is contained inside an oxide film formed on the surface of the aluminum alloy. The partially molten state is reached when the oxide film breaks and the molten aluminum alloy flows out of the oxide film. The contact time is, for example, the time from when the oxide film breaks and the molten aluminum alloy flows out of the oxide film to when the slag removal target containing copper pieces is removed.

[0017] The atmosphere of the aluminum scrap in the partially molten state is preferably air. Examples of an apparatus for heating the aluminum scrap until it is in a partially molten state and maintaining the partially molten state include an electric furnace, a reverberatory furnace, a rotary furnace, and the like.

[0018] (4) Slag removal In the manufacturing method of an aluminum alloy ingot according to the present disclosure, a slag removal target is removed from aluminum scrap in a partially molten state. The slag removal target includes copper flakes. The slag removal target includes, for example, copper flakes and dross. The copper flakes included in the slag removal target are copper flakes that remain without being dissolved in the molten aluminum alloy. For example, the target to be desalted can be desalted using a jig. The shape of the jig is not particularly limited. Note that the contact time ends when the target to be desalted is desalted.

[0019] (5) Cooling In the manufacturing method of the aluminum alloy ingot disclosed herein, after removing the slag from the target to be removed, the portion of the aluminum scrap remaining after removing the slag from the target to be removed is cooled and solidified. The solidified product is an aluminum alloy ingot. For example, the entire amount of the aluminum scrap remaining after removing the slag-removing target may be cooled and solidified. Alternatively, specific components may be further removed from the aluminum scrap remaining after removing the slag-removing target, and then the aluminum scrap may be cooled and solidified.

[0020] The copper content in the produced aluminum alloy ingot is preferably 1.0 mass% or less. The higher the preheating temperature is within a range below the solidus temperature of the aluminum alloy, the lower the copper content in the produced aluminum alloy ingot. Also, the longer the preheating time is, the lower the copper content in the produced aluminum alloy ingot.

[0021] In the partially molten state, the lower the temperature of the aluminum scrap, within a range above the liquidus temperature of the aluminum alloy, the lower the copper content in the resulting aluminum alloy ingot, and the shorter the contact time, the lower the copper content in the resulting aluminum alloy ingot.

[0022] 2. Benefits of the manufacturing method for aluminum alloy ingots (1A) According to the manufacturing method of the aluminum alloy ingot disclosed herein, an aluminum alloy ingot having a low copper content can be manufactured from aluminum scrap containing copper flakes. The reason for this is presumed to be as follows. Preheating causes an oxide film to form on the surface of the copper flakes. The oxide film is composed of a CuO oxide film and a Cu2O oxide film. The Cu2O oxide film exists inside the CuO oxide film. When the copper flakes are in a partially molten state, the copper contained in the copper flakes is difficult to dissolve in the aluminum alloy due to the presence of an oxide film on the surface of the copper flakes. As a result, the copper content in the produced aluminum alloy ingot is reduced.

[0023] (1B) In the manufacturing method of the aluminum alloy ingot disclosed herein, the contact time can be set to 10 minutes or less. In this case, the amount of copper dissolved in the aluminum alloy in a partially molten state is further reduced. As a result, the copper content in the manufactured aluminum alloy ingot is further reduced.

[0024] (1C) According to the manufacturing method of the aluminum alloy ingot disclosed herein, the copper content in the produced aluminum alloy ingot can be set to 1.0 mass % or less. (1D) According to the manufacturing method of the aluminum alloy ingot disclosed herein, dross can be further removed.

[0025] 3. Working Example (1) Preparation of raw materials The raw material was prepared by mixing the following components: Note that this raw material corresponds to aluminum scrap containing copper pieces and aluminum alloys.

[0026] 99.99% pure aluminum ingot: 285g Copper tube: 15g (2) Production of Aluminum Alloy Ingot of Example 1 The raw materials were put into a crucible. Next, the raw materials were preheated in the atmosphere using an electric furnace. The preheating temperature was 450°C or higher and lower than the solidus temperature of the raw materials. The preheating time was 53 minutes. Next, the raw materials were placed in a partially molten state in the atmosphere. In the partially molten state, the temperature of the raw materials was higher than the liquidus temperature of the raw materials. In the partially molten state, the copper tube was solid and the aluminum ingot was molten. Next, a jig was used to remove the copper tube from the partially molten raw material. The copper tube corresponds to the target for slag removal. The contact time was 10 minutes. Next, the remaining part of the raw material after slag removal was cooled to obtain an aluminum alloy ingot.

[0027] (3) Production of aluminum alloy ingot of Example 2 An aluminum alloy ingot was produced basically in the same manner as in Example 1. However, in Example 2, the preheating time was 72 minutes.

[0028] (4) Measurement of copper concentration The copper concentrations in the aluminum alloy ingots produced in Examples 1 and 2 were measured by optical emission spectrometry. The copper concentration in the aluminum alloy ingot produced in Example 1 was 0.1% by mass. The copper concentration in the aluminum alloy ingot produced in Example 2 was 0.4% by mass.

[0029] 4.Reference example (1) Reference example 1 A new copper tube was charged into a molten aluminum alloy kept at 740°C. After 5 minutes had elapsed since the copper tube was charged into the molten metal, the copper tube was pulled out of the molten metal. In the following, the time from the time the copper tube was charged into the molten metal to the time the copper tube was pulled out of the molten metal is referred to as the contact time with the molten metal. In Reference Example 1, the contact time with the molten metal was 5 minutes. After the copper tube was pulled out of the molten metal, the copper concentration in the molten metal was measured by optical emission spectrometry. The measurement results are shown in Table 1.

[0030] [Table 1]

[0031] (2) Reference example 2 Basically, the same treatment as in Reference Example 1 was carried out. However, the contact time with the molten metal was 10 minutes. After the copper tube was pulled out of the molten metal, the copper concentration in the molten metal was measured by optical emission spectrometry. The measurement results are shown in Table 1.

[0032] (3) Reference example 3 A new copper tube was preheated in the atmosphere. The preheating temperature was 400°C. The preheating time was 30 minutes. Next, the copper tube was charged into a molten aluminum alloy kept at 740°C. After 10 minutes had elapsed since the copper tube was charged into the molten metal, the copper tube was pulled out of the molten metal. In other words, the contact time with the molten metal was 10 minutes. After the copper tube was pulled out of the molten metal, the copper concentration in the molten metal was measured by optical emission spectrometry. The measurement results are shown in Table 1.

[0033] (4) Reference examples 4-5 In Reference Examples 4 to 5, the same treatment as in Reference Example 3 was basically performed, except that the preheating temperature and preheating time were as shown in Table 1. In each of Reference Examples 4 to 5, after the copper tube was pulled out of the molten metal, the copper concentration in the molten metal was measured by optical emission spectrometry. The measurement results are shown in Table 1.

[0034] (5) Relationship between preheating conditions and copper concentration in molten metal In Reference Examples 4 and 5, the preheating temperature was 500° C. or more, and the preheating time was 30 minutes or more. In Reference Examples 1 and 2, preheating was not performed. In Reference Example 3, the preheating temperature was 400° C.

[0035] The copper concentration in the molten metal was significantly low in Reference Examples 4 to 5. The copper concentration in the molten metal was higher in Reference Examples 1 to 3 than in Reference Examples 4 to 5. From these results, it was confirmed that the preheating performed in Reference Examples 4 to 5 made it difficult for the copper contained in the copper tube to dissolve in the molten metal. The reason why the copper concentration in the molten metal was significantly low in Reference Examples 4 and 5 is presumed to be as follows. By performing preheating at a temperature of 500°C or higher for 30 minutes or more, an oxide film was formed on the surface of the copper tube. When the copper tube was immersed in the molten metal, the copper contained in the copper tube was difficult to dissolve in the molten metal due to the presence of the oxide film on the surface of the copper tube. As a result, the copper concentration in the molten metal was low.

[0036] The results of the Reference Example show the following: In the Reference Example, when a copper tube was preheated at a temperature of 500°C or higher for 30 minutes or longer, an oxide film was formed on the surface of the copper tube, and the copper contained in the copper tube became difficult to dissolve in the molten aluminum alloy.

[0037] In the manufacturing method of the aluminum alloy ingot disclosed herein, when the aluminum scrap is preheated, the copper flakes contained in the aluminum scrap are difficult to dissolve in the molten aluminum alloy. As a result, the manufacturing method of the aluminum alloy ingot disclosed herein can produce an aluminum alloy ingot with a low copper content from the aluminum scrap containing the copper flakes.

[0038] 5. Other embodiments Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0039] (1) The aluminum scrap may be preheated and then subjected to other processing before being put into a partially molten state. After the slag removal target is removed, other processing may be performed, and the portion of the aluminum scrap remaining after the slag removal may be cooled.

[0040] (2) The function of one component in the above embodiments may be shared by multiple components, or the functions of multiple components may be performed by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0041] (3) In addition to the above-described method for producing an aluminum alloy ingot, the present disclosure can be realized in various forms, such as a method for recovering aluminum, a method for refining aluminum, and a method for separating copper.

[0042] [Technical idea disclosed in this specification] [Item 1] The temperature of the aluminum scrap containing the copper pieces and the aluminum alloy is set to 450° C. or more and less than the solidus temperature of the aluminum alloy for 30 minutes or more; The aluminum scrap is in a state where the temperature is higher than the liquidus temperature of the aluminum alloy, the copper pieces are in a solid state, and the aluminum alloy is in a molten state. A slag removal target containing the copper pieces is removed from the aluminum scrap in the partially molten state; Cooling the portion of the aluminum scrap remaining after removing the slag from the slag removal target; A method for manufacturing aluminum alloy ingots. [Item 2] A method for producing an aluminum alloy ingot according to item 1, The contact time between the copper piece and the molten aluminum alloy is 10 minutes or less. A method for manufacturing aluminum alloy ingots. [Item 3] 3. A method for producing an aluminum alloy ingot according to claim 1 or 2, The copper content in the produced aluminum alloy ingot is 1.0% by mass or less. A method for manufacturing aluminum alloy ingots. [Item 4] A method for producing an aluminum alloy ingot according to any one of items 1 to 3, The slag removal target includes the copper pieces and dross. A method for manufacturing aluminum alloy ingots.

Claims

1. The temperature of the aluminum scrap containing the copper pieces and the aluminum alloy is set to 450° C. or more and less than the solidus temperature of the aluminum alloy for 30 minutes or more; The aluminum scrap is in a state where the temperature is higher than the liquidus temperature of the aluminum alloy, the copper pieces are in a solid state, and the aluminum alloy is in a molten state. A slag removal target containing the copper pieces is removed from the aluminum scrap in the partially molten state; Cooling the portion of the aluminum scrap remaining after removing the slag from the slag removal target; A method for manufacturing aluminum alloy ingots.

2. A method for producing an aluminum alloy ingot according to claim 1, comprising the steps of: The contact time between the copper piece and the molten aluminum alloy is 10 minutes or less. A method for manufacturing aluminum alloy ingots.

3. A method for producing an aluminum alloy ingot according to claim 1 or 2, comprising the steps of: The copper content in the produced aluminum alloy ingot is 1.0 mass% or less. A method for manufacturing aluminum alloy ingots.

4. A method for producing an aluminum alloy ingot according to claim 1 or 2, comprising the steps of: The slag removal target includes the copper pieces and dross. A method for manufacturing aluminum alloy ingots.

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