Method for producing molten aluminum alloy and method for producing aluminum alloy casting

Abstract

A method for producing a molten aluminum alloy that can increase the melting yield when producing a molten aluminum alloy using raw materials containing aluminum chips. [Solution] This is a method for producing molten aluminum alloy by melting raw materials using a melting furnace (1) that directly heats the raw materials with a combustion flame (15) spewing from the nozzle of a burner, and producing molten aluminum alloy. The raw materials include ingots (16) and aluminum chips (17) with a number of 15 or more pieces per 10 g, and the aluminum chips (17) are placed in the melting furnace (1) so that the ingots (16) are positioned between the aluminum chips (17) and the nozzle of the burner, and the raw materials are heated.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a molten aluminum alloy and a method for producing an aluminum alloy casting. [Background technology]

[0002] In recent years, reducing greenhouse gas (GHG) emissions, such as carbon dioxide, which cause global warming, has become an issue. For this reason, there is a demand to reduce greenhouse gas emissions from aluminum alloy materials used in aluminum alloy castings and other products. One method for reducing greenhouse gas emissions from aluminum alloy materials is to use aluminum chips as the raw material for the aluminum alloy materials.

[0003] For example, Patent Document 1 describes a method and apparatus for melting aluminum chips, which are cutting scraps of aluminum metal or alloy, to obtain molten aluminum. Patent Document 1 also describes an aluminum melting apparatus that produces molten aluminum by melting preheated aluminum chips using a crucible-type melting furnace indirectly heated by a combustion burner. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-183275 Summary of the Invention [Problem to be solved by the invention]

[0005] To produce molten aluminum alloys industrially and efficiently, it is preferable to use a method of producing molten aluminum alloys by melting raw materials using a melting furnace in which the raw materials are directly heated by a combustion flame ejected from the nozzle of a burner. However, when such a melting furnace is used to melt raw materials containing aluminum chips to produce a molten aluminum alloy, a larger amount of molten metal residue (dross) is generated during the production of the molten aluminum alloy than when raw materials containing no aluminum chips are used. As a result, when a molten aluminum alloy is produced using raw materials containing aluminum chips, the melting yield becomes low, which is a problem.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing a molten aluminum alloy that can increase the melting yield when producing a molten aluminum alloy using a raw material that contains aluminum chips. Another object of the present invention is to provide a method for producing an aluminum alloy casting, which includes a step of producing a molten aluminum alloy using the method for producing a molten aluminum alloy of the present invention, and which uses raw materials containing aluminum chips to produce an aluminum alloy casting with a high raw material yield. [Means for solving the problem]

[0007] The present inventors have conducted extensive research into the cause of the large amount of molten metal residue (dross) that is generated when molten aluminum alloy is produced by melting raw materials containing aluminum chips using a melting furnace in which the raw materials are directly heated by a combustion flame ejected from the nozzle of a burner. As a result, it was found that aluminum chips are easily oxidized when heated by direct contact with the combustion flame ejected from the burner nozzle, and that small aluminum chips are particularly susceptible to oxidation when heated by direct contact with the combustion flame ejected from the burner.

[0008] Therefore, in order to suppress oxidation of aluminum chips when melting raw materials containing small-sized aluminum chips, the inventors focused on the relationship between the arrangement of burner nozzles in a melting furnace and the arrangement of aluminum chips in the raw materials and conducted extensive research. As a result, the inventors discovered that by placing an ingot between small aluminum chips (15 or more chips per 10 g) and the burner nozzle so that the combustion flame spewing from the burner nozzle does not directly hit the aluminum chips, and thereby suppressing oxidation of the aluminum chips when the raw materials are melted, it is possible to increase the melting yield of the molten aluminum alloy, and thus arrived at the present invention. The present invention provides the following means.

[0009] [1] A method for producing a molten aluminum alloy, comprising melting raw materials in a melting furnace that directly heats the raw materials with a combustion flame emitted from a burner nozzle, to produce a molten aluminum alloy, The raw material includes an ingot and aluminum chips having a number of 15 or more pieces per 10 g, a melting furnace for melting aluminum alloys, the melting furnace being configured to heat the aluminum chips and the ingots, the aluminum chips being placed in the melting furnace and the ingots being placed between the aluminum chips and the burner nozzle.

[0010] [2] After the molten aluminum alloy is discharged from the melting furnace, until the temperature of the bottom surface of the melting furnace becomes 100°C or less, The method for producing a molten aluminum alloy according to [1], wherein the aluminum chips are placed in the melting furnace so that the ingot is disposed between the aluminum chips and the bottom surface, and heating of the raw material is started.

[0011] [3] The method for producing a molten aluminum alloy according to [1] or [2], wherein the content of the aluminum chips contained in the raw material is 0.1 mass % to 30 mass %.

[0012] [4] a molten aluminum alloy forming step of producing a molten aluminum alloy by melting raw materials including aluminum chips; a casting step of solidifying the molten aluminum alloy to obtain an aluminum alloy casting, A method for producing an aluminum alloy casting, wherein the method for producing a molten aluminum alloy according to [1] or [2] is used in the molten aluminum alloy forming step.

[0013] [5] The method for producing an aluminum alloy casting according to [4], wherein the content of the aluminum chips contained in the raw material is 0.1 mass % to 30 mass %. [Effects of the Invention]

[0014] In the method for producing a molten aluminum alloy of the present invention, aluminum chips having 15 or more particles per 10 g are placed in a melting furnace so that the ingot is positioned between the aluminum chips and the burner nozzle, and a raw material containing the ingot and the aluminum chips is heated. This makes it possible to increase the melting yield when producing a molten aluminum alloy by melting a raw material containing small aluminum chips having 15 or more particles per 10 g using a melting furnace that directly heats the raw material with a combustion flame ejected from the burner nozzle. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic side view illustrating an example of an apparatus for producing an aluminum alloy cast product, including a melting furnace that can be used in the method for producing a molten aluminum alloy according to a first embodiment. FIG. [Figure 2] 2 is a schematic cross-sectional view of the melting furnace shown in FIG. 1 taken along the line AA shown in FIG. [Figure 3] 2 is a schematic cross-sectional view of the melting furnace shown in FIG. 1 taken along the line AA shown in FIG. 1, and is a schematic cross-sectional view for explaining another arrangement of raw materials placed in the melting furnace. FIG. [Figure 4] FIG. 1 is a schematic side view illustrating another example of an apparatus for producing an aluminum alloy casting, including a melting furnace that can be used in the method for producing a molten aluminum alloy of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The method for producing a molten aluminum alloy and the method for producing an aluminum alloy cast product according to this embodiment will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate modifications may be made within the scope of the present invention.

[0017] [Method of manufacturing molten aluminum alloy] Fig. 1 is a schematic side view illustrating an example of an apparatus for producing an aluminum alloy cast product, including a melting furnace that can be used in the method for producing a molten aluminum alloy according to the first embodiment. Fig. 2 is a schematic cross-sectional view of the melting furnace shown in Fig. 1, taken along line AA shown in Fig. 1. In this embodiment, raw materials are melted using a melting furnace 1 shown in FIGS. 1 and 2 to produce a molten aluminum alloy.

[0018] 1, reference numeral 1 denotes a melting furnace, reference numeral 2 denotes a holding furnace, and reference numeral 3 denotes a casting machine. In the method for producing a molten aluminum alloy according to the first embodiment, the melting furnace 1, the holding furnace 2, and the casting machine 3 can all be known.

[0019] The melting furnace 1 shown in Fig. 1 uses a combustion flame emitted from a burner nozzle to directly heat and melt raw materials to produce a molten aluminum alloy. The melting furnace 1 has a main body 1c, a supply port 1a for supplying raw materials, and a discharge port 1b for discharging the molten aluminum alloy produced by melting the raw materials in the melting furnace 1. Supply port 1a is closed by a furnace door provided on the side of main body 1c in an openable and closable manner. Discharge port 1b is provided near the bottom of the side of main body 1c opposite supply port 1a in an openable and closable manner. As shown in Figure 1, discharge port 1b is connected to a trough 4 that supplies molten aluminum alloy from melting furnace 1 to holding furnace 2.

[0020] The holding furnace 2 is made of firebricks or the like. The holding furnace 2 heats the molten aluminum alloy and holds it in a molten state. As shown in FIG. 1, a trough 4 connected to the outlet 1b of the melting furnace 1 is connected to the top surface of the holding furnace 2. In addition, a trough 5 for supplying the molten aluminum alloy from the holding furnace 2 to a casting machine 3 is connected to the bottom surface of the holding furnace 2. In FIG. 1, one casting machine 3 is connected to the holding furnace 2, but multiple casting machines 3 may be connected to the holding furnace 2.

[0021] The main body 1c of the melting furnace 1 shown in Fig. 1 is made of firebricks, etc. As shown in Fig. 2, the main body 1c has a bottom surface 12, a ceiling surface 14, and a side surface 13 connecting the bottom surface 12 and the ceiling surface 14. The bottom surface 12 has a plate-like shape that is generally rectangular in plan view. The ceiling surface 14 has a semicircular cross section when viewed from a first direction (see FIG. 2), and the side surface when viewed from a second direction perpendicular to the first direction has a rectangular shape. In other words, the outer shape of the main body 1c has a columnar cross section when viewed from the first direction that extends in the second direction.

[0022] A plurality of burners are provided on the ceiling surface 14 of the main body 1c shown in Fig. 2. In this embodiment, the burner nozzles are arranged in two linear rows at equal intervals along the extension direction of the highest point of the ceiling surface 14, symmetrically with respect to the highest point of the ceiling surface 14. The number and arrangement of burner nozzles arranged within the main body 1c are not limited to the example shown in Fig. 2. For example, some or all of the burner nozzles arranged on the ceiling surface 14 may be arranged on the side surface 13. Furthermore, the burner nozzles may be arranged in three rows along the extension direction of the highest point of the ceiling surface 14. Any known burner that can be installed in the melting furnace 1 can be used.

[0023] In the method for producing a molten aluminum alloy according to this embodiment, first, raw materials are supplied from a supply port 1a into a main body 1c of a melting furnace 1 shown in FIG. In this embodiment, the raw materials used include ingots 16 and aluminum chips 17, as shown in Fig. 2. The ingots 16 used include a connected rectangular ingot 16a having a shape in which a plurality of rectangular ingots are arranged at equal intervals on a flat plate, and a columnar ingot 16b having a rectangular columnar shape in cross section.

[0024] In this embodiment, an example will be described in which the raw material contains a plurality of connected rectangular ingots 16a and a plurality of columnar ingots 16b, but the shape of the ingots 16 contained in the raw material is not limited to the shape of the ingots 16 shown in Fig. 2 and may be, for example, rectangular, granular, or plate-shaped. Furthermore, the types of shapes of the ingots 16 contained in the raw material are not limited to two types, connected rectangular ingots 16a and columnar ingots 16b, but may be three or more types or only one type.

[0025] Each ingot 16 contained in the raw materials may have a weight (size) of, for example, 1 kg to 800 kg, and may be appropriately selected depending on the size of the melting furnace 1 and the amount of molten aluminum alloy produced by melting the raw materials. If each ingot 16 weighs 1 kg or more, by placing the ingot 16 between the aluminum chips 17 and the burner nozzle, it is easy to prevent the combustion flame 15 spewing from the burner nozzle from directly hitting the aluminum chips 17. Furthermore, if each ingot 16 weighs 800 kg or less, the ingots 16 are easy to handle. The weight of each ingot 16 is preferably 5 kg to 30 kg, and more preferably 10 kg to 20 kg.

[0026] In this embodiment, the weights (sizes) of the multiple ingots 16 contained in the raw material may be different from one another, or some or all of them may be the same. Therefore, the weights of the connected square-shaped ingots 16a and the columnar ingots 16b contained in the raw material may be the same or different. Furthermore, the weights (sizes) of the multiple connected square-shaped ingots 16a may be different from one another, or some or all of them may be the same. Furthermore, the weights (sizes) of the multiple columnar ingots 16b may be different from one another, or some or all of them may be the same.

[0027] Furthermore, multiple types of ingots with different compositions may be used as the ingot 16. Specifically, it is preferable to use an aluminum bullion ingot and a master alloy ingot made from aluminum and a metal element other than aluminum, so as to obtain an aluminum alloy molten metal having a predetermined aluminum alloy composition, as the ingot 16.

[0028] The aluminum chips 17 used have a number of 15 or more pieces per 10 g. The aluminum chips 17 may have a number of 30 to 50 pieces per 10 g, or may have a number of 50 to 110 pieces per 10 g. When the number is 30 or more pieces per 10 g, a larger number of small-sized aluminum chips 17 are contained, and therefore, the effect of increasing the melting yield by using the method for producing a molten aluminum alloy of this embodiment becomes significant.

[0029] As the aluminum chips 17, for example, peeling chips, cutting chips, and other aluminum chips that are generated when molten aluminum alloy is processed into a predetermined shape can be used. The aluminum alloy composition of the aluminum chips 17 is not particularly limited, and any composition selected from the 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, and 7000 series can be used. It is preferable to use an aluminum alloy composition of the 3000 series or 6000 series for the aluminum chips 17. This is because cutting tends to form relatively long (in other words, large) chips that are resistant to oxidation when producing a molten aluminum alloy, thereby suppressing the generation of molten metal residue (dross).

[0030] In the method for producing a molten aluminum alloy according to this embodiment, the content of aluminum chips 17 contained in the raw material is preferably 0.1% by mass to 30% by mass. When the content of aluminum chips 17 is 0.1% by mass or more, the effect of increasing the melting yield by using the method for producing a molten aluminum alloy according to this embodiment becomes significant. Furthermore, when the content of aluminum chips 17 is 0.1% by mass or more, the effect of reducing greenhouse gas emissions from the aluminum alloy material produced using the molten aluminum alloy produced by the production method according to this embodiment becomes significant. The content of aluminum chips 17 is more preferably 1% by mass or more, and even more preferably 5% by mass or more. Furthermore, when the content of aluminum chips 17 is 30% by mass or less, the melting yield can be further increased. The content of aluminum chips 17 is more preferably 15% by mass or less, and even more preferably 10% by mass.

[0031] The composition of the aluminum alloy raw material is determined depending on the application of the molten aluminum alloy and is not particularly limited, and can be, for example, a 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, or 7000 series composition.

[0032] In this embodiment, the raw material may contain a raw material that is neither an ingot 16 (slab) nor aluminum chips 17 having 15 or more particles per 10 g. Examples of raw materials that are neither an ingot 16 (slab) nor aluminum chips 17 having 15 or more particles per 10 g include manufacturing process scrap materials such as scrap materials generated in the process of manufacturing products, can scrap materials, aluminum scrap materials such as A sash scrap materials and B sash scrap materials, and aluminum chips having less than 15 particles per 10 g. The content of raw materials that are neither an ingot 16 (slab) nor aluminum chips 17 having 15 or more particles per 10 g contained in the raw material is preferably 50 mass% or less.

[0033] In the method for producing a molten aluminum alloy of this embodiment, when raw materials are supplied into the melting furnace 1, as shown in Fig. 2, connected square-shaped ingots 16a are placed in contact with the bottom surface 12 of the main body 1c, aluminum chips 17 are placed on the connected square-shaped ingots 16a, and columnar ingots 16b are placed on the aluminum chips 17. In this way, ingots 16 are placed between the aluminum chips 17 and the nozzle of a burner placed on the ceiling surface 14. The arrangement of the raw materials in the melting furnace 1 is not limited to the example shown in FIG. 2, as long as the ingot 16 is placed between the aluminum chips 17 and the nozzle of the burner.

[0034] Fig. 3 is a schematic cross-sectional view of the melting furnace shown in Fig. 1 taken along line AA in Fig. 1, illustrating another arrangement of raw materials placed in the melting furnace. As shown in Fig. 3, the raw materials in the melting furnace 1 may be arranged in layers on the bottom surface 12 of the main body 1c in the following order: columnar ingot 16b, aluminum chips 17, connected square-shaped ingots 16a, aluminum chips 17, and columnar ingot 16b. In addition, the raw materials in the melting furnace 1 may be stacked in the following order on the bottom surface 12 of the main body 1c: columnar ingots 16b, aluminum chips 17, and connected square ingots 16a; or may be stacked in the following order on the bottom surface 12 of the main body 1c: aluminum chips 17, connected square ingots 16a, aluminum chips 17, and columnar ingots 16b; or may be stacked in the following order: aluminum chips 17, connected square ingots 16a, and columnar ingots 16b.

[0035] In the method for producing a molten aluminum alloy of this embodiment, as shown in FIG. 2, raw materials are placed in a melting furnace 1, and the raw materials are directly heated by a combustion flame 15 ejected from the nozzle of a burner to melt the raw materials and produce a molten aluminum alloy. The conditions for heating the raw materials with the combustion flame 15 spewing from the nozzle of the burner can be, for example, conditions for heating in the air atmosphere so that the temperature inside the melting furnace 1 reaches 800°C, and are determined appropriately depending on the composition of the molten aluminum alloy.

[0036] In the method for producing a molten aluminum alloy of this embodiment, aluminum chips 17 are placed in a melting furnace so that ingots 16 are placed between the aluminum chips 17 and the nozzle of a burner, and a raw material containing ingots 16 and aluminum chips 17 is heated. This makes it possible to suppress oxidation of aluminum chips 17, which would otherwise be caused by directly heating the raw material with combustion flame 15 ejected from the nozzle of the burner. As a result, the generation of molten metal residue (dross) in the molten aluminum alloy is suppressed, and the melting yield is increased.

[0037] In this embodiment, as shown in Fig. 1, the molten aluminum alloy obtained by heating and melting raw materials in a melting furnace 1 is discharged from a discharge port 1b and supplied to a holding furnace 2 via a trough 4. The molten aluminum alloy supplied to the holding furnace 2 is supplied to a casting machine 3 via a trough 5 and cast by a known method to produce an aluminum alloy casting.

[0038] In the method for producing a molten aluminum alloy of this embodiment, after the molten aluminum alloy is discharged from the melting furnace 1, it is preferable to supply raw materials into the melting furnace 1 again and start heating the raw materials before the temperature of the bottom surface 12 of the main body 1c of the melting furnace 1 drops to 100°C or less. This is because less energy is required to melt the raw materials. In the method for producing a molten aluminum alloy of this embodiment, it is more preferable to supply raw materials into the melting furnace 1 again and start heating the raw materials before the temperature of the bottom surface 12 of the main body 1c of the melting furnace 1 drops to 400°C or less, because less energy is required to melt the raw materials.

[0039] In the method for producing a molten aluminum alloy according to this embodiment, the flow rate of the molten aluminum alloy discharged from outlet 1b is preferably 0.6 t / min or more, and more preferably 0.7 t / min or more, because this allows the temperature of main body 1c of melting furnace 1 to decrease during the period from when the molten aluminum alloy is discharged from melting furnace 1 to when raw materials are again supplied into melting furnace 1 and melting of the raw materials is started.

[0040] In the method for producing molten aluminum alloy of this embodiment, after the molten aluminum alloy is discharged from the melting furnace 1, when raw materials are again supplied into the melting furnace 1 and heating of the raw materials begins before the temperature of the bottom surface 12 of the main body 1c of the melting furnace 1 drops below 100°C, aluminum chips 17 are placed in the melting furnace 1 so that ingots 16 are placed between the aluminum chips 17 and the nozzle of the burner, and also between the aluminum chips 17 and the bottom surface 12.

[0041] In this case, the arrangement of the raw materials in the melting furnace 1 may be such that the ingots 16 are arranged between the aluminum chips 17 and the burner nozzle, and that the ingots 16 are also arranged between the aluminum chips 17 and the bottom surface 12. This may be the arrangement shown in Figure 2 or Figure 3, or the raw materials may be arranged in a stack of columnar ingots 16b, aluminum chips 17, and connected square truncated ingots 16a on the bottom surface 12 of the main body 1c in this order.

[0042] In the method for producing a molten aluminum alloy according to the present embodiment, after the molten aluminum alloy is discharged from the melting furnace 1, raw materials are again supplied into the melting furnace 1 and heating of the raw materials is started before the temperature of the bottom surface 12 of the main body 1c of the melting furnace 1 drops to 100°C or less. In this case, aluminum chips 17 are placed in the melting furnace 1 so that ingots 16 are also placed between the aluminum chips 17 and the bottom surface 12. Therefore, even if the temperature of the bottom surface 12 of the main body 1c of the melting furnace 1 is high and exceeds 600°C, oxidation of the aluminum chips 17 contained in the raw materials due to contact with the bottom surface 12 can be suppressed. As a result, the generation of molten metal residue (dross) in the molten aluminum alloy is suppressed, and the melting yield can be increased.

[0043] In contrast, for example, if, after the molten aluminum alloy is discharged from the melting furnace 1, a raw material containing aluminum chips 17 is placed in contact with the bottom surface 12 of the main body 1c of the melting furnace 1 and heating of the raw material is started before the temperature of the bottom surface 12 of the melting furnace 1 drops below 100°C, the aluminum chips 17 contained in the raw material are easily oxidized. As a result, molten metal residue (dross) is likely to be generated in the molten aluminum alloy, resulting in a low melting yield.

[0044] The method for producing molten aluminum alloy according to this embodiment has been described using an example in which a melting furnace 1 connected to a holding furnace 2 via a trough 4 as shown in Fig. 1 is used, but the melting furnace may also serve as a holding furnace. Furthermore, the method for producing molten aluminum alloy according to this embodiment has been described using an example in which an aluminum alloy casting production apparatus is used in which molten metal is supplied from one melting furnace 1 and one holding furnace 2 to one casting machine 3 as shown in Fig. 1, but an aluminum alloy casting production apparatus in which molten metal is supplied from a plurality of melting furnaces 1 and one holding furnace 2 to one casting machine 3 may also be used.

[0045] Fig. 4 is a schematic side view illustrating another example of an apparatus for producing an aluminum alloy casting, including a melting furnace, which can be used in the method for producing a molten aluminum alloy of the present invention. In Fig. 4, the same components as those in Fig. 1 are designated by the same reference numerals, and their description will be omitted. In Figure 4, reference numeral 11 denotes a melting and holding furnace 11. Each of the two melting and holding furnaces 11 shown in Figure 4 is an integrated melting furnace and holding furnace, and functions as both a melting furnace and a holding furnace. The two melting and holding furnaces 11 shown in Figure 4 alternately supply molten metal to one casting machine 3. This allows for efficient production of aluminum alloy castings.

[0046] Similar to the melting furnace 1 shown in Fig. 1, the melting holding furnace 11 shown in Fig. 4 has a main body 1c, a supply port 1a for supplying raw materials, and a discharge port 1b for discharging the molten aluminum alloy obtained by melting the raw materials in the melting holding furnace 11. Similarly to the main body 1c of the melting furnace 1 shown in Fig. 1, the main body 1c shown in Fig. 4 has a bottom surface 12, a ceiling surface 14, and a side surface 13 connecting the bottom surface 12 and the ceiling surface 14 (see Fig. 2). Similar to the main body 1c of the melting furnace 1 shown in Fig. 1, the ceiling surface 14 of the main body 1c shown in Fig. 4 is also provided with a plurality of burners.

[0047] The molten aluminum alloy obtained by heating and melting raw materials in the main bodies 1c of the two melting and holding furnaces 11 shown in Fig. 4 is discharged from the outlets 1b of the main bodies 1c. The molten aluminum alloy discharged from the outlets 1b is supplied to the casting machine 3 via the troughs 51 connected to the melting and holding furnaces 11 and the trough 52 connecting the two troughs 51 to the casting machine 3.

[0048] In the method for producing molten aluminum alloy of this embodiment, even when two melting and holding furnaces 11 shown in FIG. 4 are used, aluminum chips 17 are placed in the melting furnace so that ingots 16 are positioned between the aluminum chips 17 and the nozzle of a burner located on the ceiling surface 14, and raw materials including ingots 16 and aluminum chips 17 are heated, just as in the case of using the melting furnace 1 shown in FIG.

[0049] Furthermore, if raw materials are to be supplied again into the melting holding furnace 11 after the molten aluminum alloy has been discharged from the melting furnace 1 and before the temperature of the bottom surface 12 of the main body 1c of the melting holding furnace 11 drops below 100°C, the aluminum chips 17 are placed in the melting furnace 1 so that the ingots 16 are positioned between the aluminum chips 17 and the burner nozzle, and also between the aluminum chips 17 and the bottom surface 12. As a result, the generation of molten metal residue (dross) in the molten aluminum alloy can be effectively suppressed, and the melting yield can be increased.

[0050] [Method of manufacturing aluminum alloy castings] Next, the method for producing an aluminum alloy casting according to this embodiment will be described in detail. The method for producing an aluminum alloy casting of the present embodiment includes a molten aluminum alloy forming step of producing a molten aluminum alloy by melting raw materials including aluminum chips, and a casting step of solidifying the molten aluminum alloy to obtain an aluminum alloy casting.

[0051] In this embodiment, the above-described method for producing a molten aluminum alloy according to this embodiment is used in the molten aluminum alloy forming step. In the molten aluminum alloy forming step, the content of aluminum chips contained in the raw material is preferably in the range of 0.1 mass % to 30 mass %.

[0052] The casting step in this embodiment is a step of cooling and solidifying the molten aluminum alloy produced in the molten aluminum alloy forming step to obtain an aluminum alloy cast product, and any known method can be used for this casting step. As the casting step, it is preferable to use a continuous casting method such as a horizontal continuous casting method or a vertical continuous casting method.

[0053] In the method for producing an aluminum alloy casting according to this embodiment, the above-described method for producing a molten aluminum alloy according to this embodiment is used in the molten aluminum alloy forming step. Therefore, by using aluminum chips as a raw material, an aluminum alloy casting with reduced greenhouse gas emissions can be obtained. Moreover, since the above-described method for producing a molten aluminum alloy according to this embodiment is used in the molten aluminum alloy forming step, the melting yield is increased, and an aluminum alloy casting with a high raw material yield can be obtained.

[0054] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as set forth in the claims. [Example]

[0055] "Examples 1 to 7" 20 t of raw material was supplied into melting furnace 1 shown in FIG. 1. The raw material used contained aluminum chips 17, the number of pieces per 10 g of which was shown in Table 1 and which had the aluminum alloy composition shown in Table 1, in the proportions shown in Table 1, with 60 mass% of connected square truncated ingots 16a and the remainder being columnar ingots 16b. The aluminum alloy composition of the raw material was the same as that of aluminum chips 17.

[0056] [Table 1]

[0057] As shown in FIG. 2, the raw materials were arranged in such a manner that a connected square ingot 16a was placed on the bottom surface 12 of the main body 1c, aluminum chips 17 were placed on the connected square ingot 16a, and a columnar ingot 16b was placed on the aluminum chips 17. Thereafter, the raw materials were directly heated in the air atmosphere by a combustion flame 15 spewing from the nozzle of the burner until the temperature inside the melting furnace 1 reached 800°C, thereby melting the raw materials and producing a molten aluminum alloy.

[0058] "Comparative Examples 1 to 4" 20 t of raw material was supplied into melting furnace 1 shown in FIG. 1. The raw material used contained aluminum chips 17, the number of pieces per 10 g of which was shown in Table 1 and which had the aluminum alloy composition shown in Table 1, in the proportions shown in Table 1, with 60 mass% of connected square truncated ingots 16a and the remainder being columnar ingots 16b. The aluminum alloy composition of the raw material was the same as that of aluminum chips 17.

[0059] The raw materials were arranged in such a manner that connected square ingots 16a were placed on the bottom surface 12 of the main body 1c, a columnar ingot 16b was placed on the connected square ingots 16a, and aluminum chips 17 were placed on the columnar ingots 16b. Thereafter, the raw materials were directly heated in the air atmosphere by a combustion flame 15 spewing from the nozzle of the burner until the temperature inside the melting furnace 1 reached 800°C, thereby melting the raw materials and producing a molten aluminum alloy.

[0060] For the molten aluminum alloys of Examples 1 to 7 and Comparative Examples 1 to 4 obtained in this manner, the melting yield was calculated by the method shown below. [Melt yield calculation method] After melting, the molten metal residue (dross) floating on the surface of the molten metal was collected. The mass of the collected molten metal residue (dross) was measured using a weighing scale, and the melting yield was calculated using the following formula [I] from the amount of molten metal residue (dross) generated and the mass of the raw materials supplied to the melting furnace. The results are shown in Table 1. Melting yield (%) = {1 - (mass of melted residue / mass of raw material)} × 100 [I]

[0061] As shown in Table 1, the molten aluminum alloys of Examples 1 to 7 had higher melting yields than the molten aluminum alloys of Comparative Examples 1 to 4. This is presumably because in Examples 1 to 7, aluminum chips 17 were placed in melting furnace 1 so that ingot 16 was positioned between aluminum chips 17 and the burner nozzle, and the raw materials containing ingot 16 and aluminum chips 17 were heated, thereby suppressing oxidation of aluminum chips 17 caused by directly heating the raw materials with combustion flame 15 ejected from the burner nozzle.

[0062] Furthermore, from Examples 1 to 4, it was found that the lower the content of aluminum chips in the raw material, the higher the melting yield tends to be, and that the lower the number of aluminum chips per 10 g, the higher the melting yield tends to be. [Explanation of symbols]

[0063] 1...Melting furnace 1a…Supply port 1b…Discharge port 1c...Main unit 2…Holding furnace 3...Casting machine 4, 5, 51, 52...Gutter 11...Melting and holding furnace 12...Bottom 13...Side 14...Ceiling surface 15...Burning flame 16...Ingot 16a...Connected square ingot 16b...Columnar ingot 17...Aluminum chips

Claims

1. A method for producing a molten aluminum alloy, comprising melting raw materials in a melting furnace that directly heats the raw materials with a combustion flame emitted from a burner nozzle, thereby producing a molten aluminum alloy, The raw material includes an ingot and aluminum chips having a number of 15 or more pieces per 10 g, a melting furnace for melting aluminum alloys, the melting furnace being configured to heat the aluminum chips and the ingots, the aluminum chips being placed in the melting furnace and the ingots being placed between the aluminum chips and the burner nozzle.

2. After the molten aluminum alloy is discharged from the melting furnace, until the temperature of the bottom surface of the melting furnace becomes 100°C or less, 2. The method for producing a molten aluminum alloy according to claim 1, wherein the aluminum chips are placed in the melting furnace so that the ingot is disposed between the aluminum chips and the bottom surface, and then heating of the raw material is started.

3. 3. The method for producing a molten aluminum alloy according to claim 1, wherein the content of the aluminum chips contained in the raw material is 0.1% by mass to 30% by mass.

4. a molten aluminum alloy forming step of producing a molten aluminum alloy by melting raw materials including aluminum chips; a casting step of solidifying the molten aluminum alloy to obtain an aluminum alloy casting, A method for producing an aluminum alloy casting, wherein the method for producing a molten aluminum alloy according to claim 1 or 2 is used in the molten aluminum alloy forming step.

5. 5. The method for producing an aluminum alloy casting according to claim 4, wherein the content of the aluminum chips contained in the raw material is 0.1% by mass to 30% by mass.

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