Method for producing aluminum alloy forged product

Abstract

A method for producing an aluminum alloy forged product includes: a molten metal formation step for melting a raw material to obtain an aluminum alloy molten metal; a casting step; and a forging step. The raw material contains an aluminum scrap material comprising one or more selected from can scrap materials, aluminum sash scrap materials, and manufacturing process scrap materials. The total aluminum scrap material content in the raw material is within a range of 0.1 mass% to 90 mass%. The aluminum alloy molten metal has a specific aluminum alloy composition.

Description

Manufacturing method for aluminum alloy forgings

[0001] This invention relates to a method for manufacturing aluminum alloy forged products. This application claims priority based on Japanese Patent Application No. 2024-174831, filed in Japan on October 4, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, aluminum alloys have seen increasing use as structural components in various products where weight reduction is required. For example, traditionally, high-tensile steel has been used for undercarriage parts such as suspension arms and bumper parts in automobiles. However, in recent years, high-strength aluminum alloys have begun to be used in place of high-tensile steel in these automobile parts.

[0003] Patent Document 1 describes an aluminum alloy forged product that can be used for suspension arms of vehicles such as automobiles. Patent Document 1 describes a forged product made of aluminum alloy containing Cu in the range of 0.30 mass% to 1.0 mass%, Mg in the range of 0.80 mass% to 1.8 mass%, Si in the range of 0.90 mass% to 1.9 mass%, Mn in the range of 0.30 mass% to 1.2 mass%, Fe in the range of 0.20 mass% to 0.65 mass%, Zn in the range of 0.25 mass%, Cr in the range of 0.050 mass% to 0.30 mass%, Ti in the range of 0.01 mass% to 0.1 mass%, and B in the range of 0.0010 mass% to 0.030 mass%. The aluminum alloy forging material is described, having an alloy composition in which Zr is contained in a range of 0.0010% by mass or more and 0.050% by mass or less, the ratio of Fe content to Mn content Fe / Mn is less than 1.4 by mass, and the remainder consists of Al and unavoidable impurities, wherein the average grain size of the alloy structure after forging is in the range of 50 μm or more and 120 μm or less, and the average grain size of AIFeSi(Mn)-based compounds present at the grain boundaries is 3.0 μm or less.

[0004] Japanese Patent Publication No. 2024-086591

[0005] Currently, reducing emissions of greenhouse gases (GHGs), such as carbon dioxide, which cause global warming, is a major challenge. Therefore, there is a demand for reducing greenhouse gas emissions from aluminum alloy forged products as well.

[0006] This invention has been made in view of the above problems, and aims to provide a method for manufacturing aluminum alloy forgings that can reduce greenhouse gas emissions.

[0007] The inventors of this invention have diligently investigated the origins of greenhouse gases emitted by aluminum alloy forgings in order to reduce greenhouse gas emissions from aluminum alloy forgings. As a result, it was found that although greenhouse gas emissions include those derived from the fuel and electricity used in the manufacture of aluminum alloy forgings, the proportion derived from the raw materials is very large.

[0008] One of the greenhouse gas emissions originating from the raw materials of aluminum alloy forgings is the emissions from the aluminum ingots contained in the raw materials. Aluminum ingots are obtained by electrolysis, a process called electrolytic refining, which is carried out on alumina, which is produced from minerals. The electrolytic refining of alumina in the manufacturing process of aluminum ingots consumes a large amount of electricity. Therefore, the greenhouse gas emissions from aluminum ingots are very high.

[0009] Based on these considerations, one possible method to reduce greenhouse gas emissions from aluminum alloy forgings is to replace a portion of the aluminum ingot used as raw material for aluminum alloy forgings with aluminum scrap instead of new aluminum ingots. However, aluminum alloy forgings manufactured using raw materials containing aluminum scrap sometimes failed to achieve the desired properties. Specifically, the inclusion of aluminum scrap in the raw material sometimes resulted in insufficient notch fatigue and / or stress corrosion cracking resistance.

[0010] Therefore, the inventors investigated the reasons why incorporating aluminum scrap into the raw material of aluminum alloy forgings results in insufficient notch fatigue and / or stress corrosion cracking resistance. As a result, they found that when aluminum scrap is incorporated into the raw material, many β-AlFeSi compounds may crystallize in the cross-sectional microstructure of the aluminum alloy forging.

[0011] This is presumed to be due to the following reasons. Specifically, aluminum scrap materials include various types such as can scrap, aluminum sash scrap, and manufacturing process scrap. The alloy composition of these aluminum scrap materials is not uniform but differs for each type. Therefore, when aluminum scrap is included in the raw material, the Fe and Si content in the raw material may become excessive due to the Fe and Si originating from the aluminum scrap. It is then presumed that the excess Fe and Si in the raw material derived from the aluminum scrap, together with Al, caused a large amount of β-AlFeSi compounds to crystallize in the aluminum alloy forging.

[0012] Therefore, the inventors focused on Mn, which has a strong interaction with Fe and Si and crystallizes α-Al(Fe,Mn)Si compounds together with Fe and Si, and investigated its relationship with the amount of AlFeSi compounds crystallized in aluminum alloy forgings. As a result, it was found that when aluminum scrap material is included in the raw material so that the Fe and Si content in the raw material is within a specific range, the amount of β-AlFeSi compounds crystallized in aluminum alloy forgings can be suppressed by sufficiently increasing the Mn content in the raw material. This is presumed to be because some of the Fe and Si in the raw material did not become AlFeSi compounds, but instead became α-Al(Fe,Mn)Si compounds through interaction with Mn.

[0013] Furthermore, based on the above findings, the inventors have repeatedly investigated the components and types of aluminum scrap material to be included in the raw material, and the range of the amount of aluminum scrap material in the raw material, so that the Fe content, Si content, and Mn content in the raw material are within specific ranges. As a result, they have confirmed that by melting a raw material containing specific aluminum scrap material in specific amounts to obtain an aluminum alloy molten metal having a specific aluminum alloy composition, and casting this to obtain an aluminum alloy forged product, the crystallization of β-AlFeSi compounds can be suppressed and an aluminum alloy forged product with reduced greenhouse gas emissions can be produced, leading to the invention of this invention. The present invention provides the following means.

[0014] [1] A process comprising: a molten metal forming step of melting raw materials to obtain molten aluminum alloy; a casting step of solidifying the molten aluminum alloy to obtain an aluminum alloy casting; and a forging step of forging the aluminum alloy casting to obtain a forged product, wherein the raw materials contain aluminum scrap material consisting of one or more types selected from can scrap material in the range of 0.1% by mass or more and 40% by mass or less; aluminum sash scrap material in the range of 0.1% by mass or more and 30% by mass or less; and manufacturing process scrap material in the range of 0.1% by mass or more and 80% by mass or less, the total content of the aluminum scrap material in the raw materials is in the range of 0.1% by mass or more and 90% by mass or less, and the molten aluminum alloy contains Cu in the range of 0.25% by mass or more and 0.55% by mass or less, Mg in the range of 0.55% by mass or more and 1.30% by mass or less, and Si in the range of 0.80% by mass or more and 1.24% by mass or less. A method for manufacturing aluminum alloy forgings, having an aluminum alloy composition containing Mn in the range of 0.45% by mass or more and 0.76% by mass or less, Fe in the range of 0.40% by mass or more and 0.55% by mass or less, Zn in the range of 0.250% by mass or less, Cr in the range of 0.050% by mass or more and 0.25% by mass or less, Ti in the range of 0.005% by mass or more and 0.1% by mass or less, B in the range of 0.0010% by mass or more and 0.030% by mass or less, and Zr in the range of 0.0010% by mass or more and 0.050% by mass or less, with the remainder being Al and unavoidable impurities.

[0015] [2] The method for manufacturing an aluminum alloy forged product according to [1], wherein the ratio of the Fe content to the Mn content, Fe / Mn, is in the range of 0.3 or more and 1.3 or less by mass ratio.

[0016] [3] The method for manufacturing an aluminum alloy forged product according to [1] or [2], wherein the total content of the aluminum scrap material in the raw materials is 0.3% by mass or more.

[0017] [4] A method for manufacturing an aluminum alloy forging according to any one of [1] to [3], comprising: a solution treatment step of performing a solution treatment on the aluminum alloy forging after the forging process; a quenching step of quenching the aluminum alloy forging after the solution treatment; and an aging step of performing an aging treatment on the aluminum alloy forging after the quenching step.

[0018] In the present invention's method for manufacturing aluminum alloy forgings, in the molten metal forming step, raw materials in which the total content of can scrap material, aluminum sash scrap material, and manufacturing process scrap material is within the range of 0.1% by mass to 90% by mass are melted to obtain molten aluminum alloy having a specific aluminum alloy composition. Therefore, greenhouse gas emissions can be reduced while ensuring the properties of the aluminum alloy forgings.

[0019] This is a cross-sectional view showing an example of the area near the mold of a horizontal continuous casting apparatus that can be used in the manufacturing method of aluminum alloy forgings according to one embodiment of the present invention. This is an enlarged cross-sectional view of the main part near the cooling water cavity of the horizontal continuous casting apparatus shown in Figure 1. This is an explanatory diagram illustrating the heat flux of the cooling wall portion of the horizontal continuous casting apparatus. This is a perspective view showing an example of an aluminum alloy forging manufactured using the manufacturing method of aluminum alloy forgings according to one embodiment of the present invention. This is a plan view showing another example of an aluminum alloy forging manufactured using the manufacturing method of aluminum alloy forgings according to one embodiment of the present invention. This is a perspective view showing yet another example of an aluminum alloy forging manufactured using the manufacturing method of aluminum alloy forgings according to one embodiment of the present invention.

[0020] The method for manufacturing aluminum alloy forged products according to this embodiment will be described in detail below, with reference to the drawings as appropriate. In the drawings used in the following description, characteristic parts may be enlarged for convenience in order to make the features of this embodiment easier to understand, and the dimensional ratios of each component may differ from those in reality. The materials, dimensions, etc. exemplified in the following description are examples only, and the present invention is not limited to them, and can be implemented with appropriate modifications without changing the essence of the invention.

[0021] [Method for Manufacturing Aluminum Alloy Forged Products] The method for manufacturing aluminum alloy forged products according to this embodiment includes, for example, a molten metal forming step, a casting step, a homogenization heat treatment step, a forging step, a solution treatment step, a quenching step, and an aging treatment step. Of these manufacturing steps, the homogenization heat treatment step, the solution treatment step, the quenching step, and the aging treatment step may be performed as needed and are not essential steps.

[0022] (Molten Metal Forming Process) The molten metal forming process is a process of melting raw materials to obtain molten aluminum alloy having the aluminum alloy composition shown below. In the method for manufacturing aluminum alloy forgings of this embodiment, in the molten metal forming process, raw materials containing aluminum scrap material, which will be described later, are melted to obtain molten aluminum alloy having the aluminum alloy composition shown below. This makes it possible to reduce greenhouse gas emissions from aluminum alloy forgings manufactured by the manufacturing method of this embodiment, suppress the excessive crystallization of β-AlFeSi compounds in the aluminum alloy forgings, and produce Al-Mg-Si based aluminum alloy forgings that have excellent mechanical properties such as notch fatigue and / or stress corrosion cracking resistance.

[0023] [Aluminum Alloy Composition] The molten aluminum alloy in this embodiment has an aluminum alloy composition containing Cu in the range of 0.25% to 0.55% by mass, Mg in the range of 0.55% to 1.30% by mass, Si in the range of 0.80% to 1.24% by mass, Mn in the range of 0.45% to 0.76% by mass, Fe in the range of 0.40% to 0.55% by mass, Zn in the range of 0.250% by mass, Cr in the range of 0.050% to 0.25% by mass, Ti in the range of 0.005% to 0.1% by mass, B in the range of 0.0010% to 0.030% by mass, and Zr in the range of 0.0010% to 0.050% by mass, with the remainder being Al and unavoidable impurities.

[0024] The aluminum alloy composition in this embodiment corresponds to the alloy composition of a 6000 series aluminum alloy containing Mg and Si. The aluminum alloy composition of the molten aluminum alloy in this embodiment can be considered to be the same as the alloy composition of an aluminum alloy forging produced by the manufacturing method of this embodiment, which involves casting the molten aluminum alloy of this embodiment and then performing a specific heat treatment on the forging.

[0025] (Cu: 0.25% by mass or more and 0.55% by mass or less) Cu has the effect of finely dispersing Mg-Si compounds in aluminum alloys and improving the tensile strength of aluminum alloys by precipitating as Al-Cu-Mg-Si compounds, including the Q phase. By having a Cu content within the above range, the mechanical properties of aluminum alloy forged products at room temperature can be improved.

[0026] (Mg: 0.55% by mass or more and 1.30% by mass or less) Mg has the effect of improving the tensile strength of aluminum alloys. Mg is dissolved in the aluminum matrix, or Mg-Si compounds (Mg ２ It contributes to strengthening aluminum alloys by precipitating as Si, or as Al-Cu-Mg-Si compounds (AlCuMgSi), including the Q phase. ２ Si is in the aluminum alloy CuAl ２It has the effect of suppressing phase formation. CuAl ２ By suppressing phase formation, the corrosion resistance of aluminum alloy forgings is improved. Maintaining an Mg content within the above range improves the mechanical properties and corrosion resistance of aluminum alloy forgings at room temperature.

[0027] (Si: 0.80% by mass or more and 1.24% by mass or less) Like Mg, Si has the effect of improving the mechanical properties and corrosion resistance of aluminum alloy forged products at room temperature. However, if the aluminum alloy contains an excess of Si, the crystallization of coarse primary Si grains may occur, which may reduce the tensile strength of the aluminum alloy. By keeping the Si content within the above range, it is possible to improve the mechanical properties and corrosion resistance of aluminum alloy forged products at room temperature while suppressing the crystallization of primary Si.

[0028] (Mn: 0.45% by mass or more and 0.76% by mass or less) Mn improves the tensile strength of aluminum alloys by forming fine granular precipitates containing intermetallic compounds such as Al-Mn-Fe-Si and Al-Mn-Cr-Fe-Si in the aluminum alloy. In addition, Mn, together with Fe and Si, causes α-Al(Fe,Mn)Si compounds to crystallize, suppressing the amount of β-AlFeSi compounds crystallized in aluminum alloy forgings and improving notch fatigue and / or stress corrosion cracking resistance. Therefore, by having a Mn content within the above range, the mechanical properties of aluminum alloy forgings can be improved. Furthermore, since the Mn content is 0.76% by mass or less, the crystallization of coarse intermetallic compounds is suppressed, preventing a deterioration in the properties of aluminum alloy forgings.

[0029] (Fe: 0.40% by mass or more and 0.55% by mass or less) Fe crystallizes in aluminum alloys as fine precipitates containing intermetallic compounds such as Al-Mn-Fe-Si, Al-Mn-Cr-Fe-Si, Al-Fe-Si, Al-Cu-Fe, and Al-Mn-Fe, thereby improving the tensile strength of aluminum alloys. By having an Fe content within the above range, the mechanical properties of aluminum alloy forged products at room temperature can be improved.

[0030] (Ratio of Fe content to Mn content: Fe / Mn) The ratio of Fe content to Mn content, Fe / Mn, is preferably within the range of 0.3 to 1.3 by mass ratio. When Fe / Mn is 0.3 or higher, it becomes easier to sufficiently incorporate aluminum scrap materials with a high Fe content, such as aluminum sash scrap, into the raw material. Furthermore, when Fe / Mn is 1.3 or lower, Mn crystallizes α-Al(Fe,Mn)Si compounds together with Fe and Si, which significantly suppresses the crystallization of β-AlFeSi compounds in aluminum alloy forgings. As a result, the mechanical properties of aluminum alloy forgings can be improved. It is more preferable that Fe / Mn be 1.0 or lower.

[0031] (Zn: 0.250 mass% or less) The Zn content should be 0.250 mass% or less. If the Zn content is 0.250 mass% or less, MgZn ２ This prevents the formation of Zn, which precipitates from the aluminum matrix at grain boundaries, causing intergranular corrosion and thus reducing the corrosion resistance of aluminum alloy forgings. For this reason, the Zn content should be 0.250% by mass or less, and preferably no Zn is present at all.

[0032] (Cr: 0.050% by mass or more and 0.25% by mass or less) Cr improves the tensile strength of aluminum alloys by forming fine granular precipitates containing intermetallic compounds such as Al-Mn-Cr-Fe-Si and Al-Fe-Cr in the aluminum alloy. By having a Cr content within the above range, the mechanical properties of aluminum alloy forgings at room temperature can be improved.

[0033] (Ti: 0.005% by mass or more and 0.1% by mass or less) Ti has the effect of refining the crystal grains of the aluminum alloy and improving the drawing processability. Since the Ti content is 0.005% by mass or more, the effect of refining the crystal grains of the aluminum alloy can be sufficiently obtained. Also, since the Ti content is 0.1% by mass or less, it is possible to prevent the formation of coarse precipitates and the reduction of drawing processability. In addition, when a large amount of coarse precipitates containing Ti is mixed into the forged product made of aluminum alloy, the toughness may decrease. Therefore, the Ti content is preferably 0.012% by mass or more and 0.035% by mass or less, and more preferably 0.015% by mass or more and 0.050% by mass or less.

[0034] (B: 0.0010% by mass or more and 0.030% by mass or less) B has the effect of refining the crystal grains of the aluminum alloy and improving the drawing processability. By adding B to the aluminum alloy together with the above-mentioned Ti, the effect of refining the crystal grains is improved. Since the B content is 0.0010% by mass or more, the effect of refining the crystal grains can be sufficiently obtained. Also, since the B content is 0.030% by mass or less, it is possible to prevent the formation of coarse precipitates and their inclusion in the forged product made of aluminum alloy. In addition, when a large amount of coarse precipitates containing B is included in the forged product made of aluminum alloy, the toughness may decrease. Therefore, the B content is 0.0010% by mass or more and 0.030% by mass or less. The B content is preferably 0.0050% by mass or more and 0.025% by mass or less.

[0035] (Zr: 0.0010% by mass or more and 0.050% by mass or less) Zr ３ precipitates as Zr and Al-(Ti,Zr), and contributes to the improvement of the strength of the forged product made of aluminum alloy by the recrystallization suppression effect and precipitation strengthening. When the Zr content is 0.050% by mass or less, it is possible to prevent the reduction of the corrosion resistance of the forged product made of aluminum alloy due to the crystallization of coarse Zr compounds. Therefore, the Zr content is 0.050% by mass or less. Also, in order to obtain the effect of improving the strength of the forged product made of aluminum alloy by the above-mentioned recrystallization suppression effect and precipitation strengthening, the Zr content is 0.0010% by mass or more.

[0036] (Inevitable impurities) Inevitable impurities are impurities that inevitably mix into the aluminum alloy from raw materials or during the manufacturing process. Examples of inevitable impurities include Ni, Sn, Be, etc. The content rate of these inevitable impurities preferably does not exceed 0.1% by mass, and the lower the better.

[0037] [Aluminum scrap material] In the manufacturing method of the present embodiment, in the molten metal forming step, a raw material containing an aluminum scrap material is melted to obtain an aluminum alloy molten metal. In the present embodiment, as the aluminum scrap material, an aluminum scrap material composed of any one or two or more selected from a can scrap material, an aluminum sash scrap material, and a manufacturing process scrap material is used.

[0038] These aluminum scrap materials are preferable because they have a higher purity of aluminum and stable quality compared to engine part scrap materials, etc. Also, these aluminum scrap materials are recycled from aluminum sashes and are preferable because they have a larger quantity of aluminum scrap materials and are easily available compared to A sash scrap materials that do not contain materials other than the aluminum alloy forming the sash such as screws and handles.

[0039] (Can scrap material) The can scrap material is an aluminum scrap material recycled from aluminum cans. When a can scrap material is included as the aluminum scrap material, at least Fe, Si, Mg, and Mn are added as elements other than Al derived from the can scrap material in the raw material.

[0040] The content of Fe contained in the can scrap material is, for example, within the range of 0% by mass or more and 0.8% by mass or less. The content of Si contained in the can scrap material is, for example, within the range of 0% by mass or more and 0.6% by mass or less. The content of Mg contained in the can scrap material is, for example, within the range of 0.8% by mass or more and 1.3% by mass or less. The content of Mn contained in the can scrap material is, for example, within the range of 0.8% by mass or more and 1.5% by mass or less.

[0041] If the raw material contains can scrap, the can scrap content in the raw material shall be within the range of 0.1% by mass or more and 40% by mass or less. If the can scrap content in the raw material is 0.1% by mass or more, the greenhouse gas emission reduction effect due to the inclusion of can scrap in the raw material is sufficiently obtained. Preferably, the can scrap content in the raw material is 10% by mass or more.

[0042] Furthermore, if the can scrap material content in the raw materials is 40% by mass or less, it is possible to prevent the properties of the aluminum alloy forging from being impaired by elements other than Al, such as Fe, Si, Mg, and Mn, derived from the can scrap material. Preferably, the can scrap material content in the raw materials is 30% by mass or less.

[0043] (Aluminum sash scrap material) The aluminum sash scrap material used in this embodiment is aluminum scrap material recycled from aluminum sashes with screws, handles, etc., attached. Therefore, the components of the aluminum sash scrap material include not only the components of the aluminum alloy used in the manufacture of the aluminum sash, but also components contained in the screws, handles, etc.

[0044] When aluminum sash scrap is included as aluminum scrap material, at least Fe, Si, and Mg are added to the raw material as elements other than Al derived from the aluminum sash scrap material. The Fe content in the aluminum sash scrap material is, for example, in the range of 0.2% by mass or more and 0.7% by mass or less. The Si content in the aluminum sash scrap material is, for example, in the range of 0.2% by mass or more and 0.7% by mass or less. The Mg content in the aluminum sash scrap material is, for example, in the range of 0.3% by mass or more and 1.2% by mass or less.

[0045] If aluminum sash scrap material is included in the raw material, the content of aluminum sash scrap material in the raw material shall be within the range of 0.1% by mass or more and 30% by mass or less. If the content of aluminum sash scrap material in the raw material is 0.1% by mass or more, the greenhouse gas emission reduction effect due to the inclusion of aluminum sash scrap material in the raw material can be sufficiently obtained. Preferably, the content of aluminum sash scrap material in the raw material is 10% by mass or more.

[0046] Furthermore, if the content of aluminum sash scrap material in the raw material is 30% by mass or less, it is possible to prevent the properties of the aluminum alloy forged product from being impaired by elements other than Al, such as Fe, Si, and Mg, derived from the aluminum sash scrap material. Preferably, the content of aluminum sash scrap material in the raw material is 20% by mass or less.

[0047] Aluminum sash scrap material has a higher Fe content compared to can scrap material and manufacturing process scrap material. Therefore, when aluminum sash scrap material is included as aluminum scrap material, the amount of β-AlFeSi compound crystallization in aluminum alloy forgings tends to be higher compared to when can scrap material and / or manufacturing process scrap material is included. For this reason, the upper limit for the content of aluminum sash scrap material in the raw material was set to be lower than the upper limit for the content of can scrap material and manufacturing process scrap material.

[0048] Furthermore, if the raw materials contain can scrap and / or manufacturing process scrap along with aluminum sash scrap, it is preferable that the content of aluminum sash scrap is less than the content of can scrap and manufacturing process scrap. This is because it is possible to suppress the amount of β-AlFeSi compounds crystallized in the aluminum alloy forging.

[0049] (Manufacturing Process Scrap) Manufacturing process scrap is scrap generated during the process of manufacturing aluminum alloy forgings. Specifically, this includes waste molten metal and waste material generated when casting molten aluminum alloy to be used for aluminum alloy forgings, and chips and burrs generated when processing molten aluminum alloy into a predetermined shape. Even if manufacturing process scrap is included in the aluminum scrap material, the influence of elements other than Al derived from the manufacturing process scrap on the aluminum alloy composition used to manufacture aluminum alloy forgings is minimal. For this reason, the upper limit for the content of manufacturing process scrap in the raw materials was set to exceed the upper limit for the content of can scrap and aluminum sash scrap.

[0050] In other words, if the raw material contains manufacturing process scrap, the amount of manufacturing process scrap in the raw material should be within the range of 0.1% by mass or more and 80% by mass or less. If the amount of manufacturing process scrap in the raw material is 0.1% by mass or more, the effect of reducing greenhouse gas emissions due to the inclusion of manufacturing process scrap in the raw material can be sufficiently obtained. Preferably, the amount of manufacturing process scrap in the raw material should be 20% by mass or more.

[0051] Furthermore, if the content of manufacturing process scrap material in the raw material is 80% by mass or less, it is possible to prevent elements other than Al derived from the manufacturing process scrap material from impairing the properties of the aluminum alloy forging. Preferably, the content of manufacturing process scrap material in the raw material is 50% by mass or less.

[0052] In the manufacturing method of this embodiment, the total content of aluminum scrap material in the raw materials (total content of can scrap material, aluminum sash scrap material, and manufacturing process scrap material) is within the range of 0.1% by mass or more and 90% by mass or less. Since the total content of aluminum scrap material in the raw materials is 0.1% by mass or more, greenhouse gas emissions can be reduced. The total content of aluminum scrap material in the raw materials is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 50% by mass or more, in order to reduce greenhouse gas emissions more effectively.

[0053] Furthermore, in this embodiment, the total content of aluminum scrap material in the raw materials is 90% by mass or less. Therefore, it is possible to suppress the content of elements other than Al derived from the aluminum scrap material contained in the raw materials. As a result, the properties of the aluminum alloy forged product manufactured using the manufacturing method of this embodiment can be ensured. From the viewpoint of easily ensuring the properties of the aluminum alloy forged product, the total content of aluminum scrap material in the raw materials is preferably 80% by mass or less, and more preferably 70% by mass or less.

[0054] In the molten metal forming process of this embodiment, raw materials including, for example, a new aluminum ingot, individual elements included in the above-mentioned aluminum alloy composition and / or a compound containing two or more of the above-mentioned elements included in the above-mentioned aluminum alloy composition, and aluminum scrap material are heated and melted by a known method. This makes it possible to obtain molten aluminum alloy having the above-mentioned aluminum alloy composition.

[0055] (Casting Process) In the casting process, molten aluminum alloy (liquid phase) is cooled and solidified into a solid (solid phase) to obtain an aluminum alloy casting. In the casting process of this embodiment, for example, a horizontal continuous casting method can be used.

[0056] Here, with reference to Figures 1 and 2, a horizontal continuous casting apparatus that can be used in the manufacturing method of aluminum alloy castings according to this embodiment will be described. Figure 1 is a cross-sectional view showing an example of the area near the mold of the horizontal continuous casting apparatus. Figure 2 is an enlarged cross-sectional view of the main part near the cooling water cavity of the horizontal continuous casting apparatus shown in Figure 1.

[0057] The horizontal continuous casting apparatus 10 shown in Figures 1 and 2 includes a molten metal receiving section (tundish) 11, a hollow cylindrical mold 12, and a refractory plate-like body (insulating member) 13 positioned between one end 12a of the mold 12 and the molten metal receiving section 11. The molten metal receiving section 11 consists of a molten metal inlet 11a for receiving the molten aluminum alloy M obtained in the molten metal forming process, a molten metal holding section 11b, and an outlet 11c for outflow to the hollow section 21 of the mold 12.

[0058] The molten metal receiving section 11 maintains the upper liquid level of the molten aluminum alloy M at a position higher than the upper surface of the hollow section 21 of the mold 12. When performing multi-casting, the molten metal receiving section 11 stably distributes the molten aluminum alloy M to each mold 12. The molten aluminum alloy M held in the molten metal holding section 11b within the molten metal receiving section 11 is poured into the hollow section 21 of the mold 12 through the pouring passage 13a provided in the refractory plate-like body 13. The molten aluminum alloy M supplied into the hollow section 21 is then cooled and solidified by the cooling device 23 (described later), and is pulled out from the other end 12b of the mold 12 as a solidified ingot, an aluminum alloy rod Z.

[0059] An extraction drive device (not shown) for extracting the cast aluminum alloy rod Z at a constant speed is installed at the other end 12b of the mold 12. It is also preferable that a synchronized cutting machine (not shown) for cutting the continuously extracted aluminum alloy rod Z to a desired length is installed at the other end 12b of the mold 12.

[0060] The refractory plate-like body 13 is a member that blocks heat transfer between the molten metal receiving section 11 and the mold 12. The refractory plate-like body 13 may be made of materials such as calcium silicate, alumina, silica, a mixture of alumina and silica, silicon nitride, silicon carbide, or graphite. Such a refractory plate-like body 13 can also be made up of multiple layers of different constituent materials.

[0061] In this embodiment, the mold 12 is a hollow cylindrical member. The mold 12 is formed from one or more materials selected from, for example, aluminum, copper, or alloys thereof. The materials for the mold 12 should be selected in an optimal combination in terms of thermal conductivity, heat resistance, and mechanical strength. The hollow portion 21 of the mold 12 is formed in a circular cross-section in order to cast the aluminum alloy rod Z into a cylindrical shape. The mold 12 is held such that the mold central axis (central axis) C, which passes through the center of the hollow portion 21, is aligned in a substantially horizontal direction.

[0062] The inner circumferential surface 21a of the hollow portion 21 of the mold 12 is formed at an elevation angle of 0° to 3° (more preferably 0° to 1°) with respect to the mold's central axis C, in the casting direction of the aluminum alloy rod Z (see Figure 1). In other words, the inner circumferential surface 21a is configured in a tapered shape that opens in a cone shape toward the casting direction. The angle formed by this taper is the elevation angle.

[0063] If the elevation angle is less than 0°, casting may become difficult because the aluminum alloy rod Z encounters resistance at the other end 12b, which is the mold exit, when it is pulled out of the mold 12. On the other hand, if the elevation angle exceeds 3°, the contact between the inner circumferential surface 21a and the molten aluminum alloy M becomes insufficient. This reduces the heat dissipation effect from the molten aluminum alloy M and the solidified shell formed by the cooling and solidification of the molten aluminum alloy M to the mold 12, which may result in insufficient solidification of the molten aluminum alloy M. As a result, a remelted surface may form on the surface of the aluminum alloy rod Z, or unsolidified molten aluminum alloy M may spurt out from the end of the aluminum alloy rod Z, which is undesirable as it may lead to casting problems.

[0064] Furthermore, the cross-sectional shape of the hollow portion 21 of the mold 12 (the planar shape when the hollow portion 21 of the mold 12 is viewed from the other end 12b) can be selected according to the shape of the aluminum alloy rod to be cast, in addition to the circular shape of this embodiment. For example, it can be a polygonal shape such as a triangle or rectangle, or a shape with an irregular cross-sectional shape that does not have an axis of symmetry and / or plane of symmetry, such as a semicircle or ellipse.

[0065] A fluid supply pipe 22 is located at one end 12a of the mold 12 to supply lubricating fluid into the hollow portion 21 of the mold 12. The lubricating fluid supplied from the fluid supply pipe 22 can be one or more types of lubricating fluid selected from gaseous lubricants and liquid lubricants. When supplying both gaseous and liquid lubricants, it is preferable to provide separate fluid supply pipes for each. The pressurized lubricating fluid supplied from the fluid supply pipe 22 is supplied into the hollow portion 21 of the mold 12 through an annular lubricant supply port 22a.

[0066] In this embodiment, the pressurized lubricating fluid is supplied to the inner circumferential surface 21a of the mold 12 from the lubricant supply port 22a. Alternatively, the liquid lubricant may be heated and decomposed into a gas before being supplied to the inner circumferential surface 21a of the mold 12. Alternatively, a porous material may be placed at the lubricant supply port 22a, allowing the lubricating fluid to seep out onto the inner circumferential surface 21a of the mold 12 through this porous material.

[0067] A cooling device 23 is formed inside the mold 12. The cooling device 23 is a cooling means for cooling and solidifying the molten aluminum alloy M. In this embodiment, the cooling device 23 has a cooling water cavity 24 that contains cooling water W for cooling the inner circumferential surface 21a of the hollow portion 21 of the mold 12, and a cooling water injection passage 25 that connects the cooling water cavity 24 and the hollow portion 21 of the mold 12.

[0068] The cooling water cavity 24 is formed in an annular shape inside the mold 12, outside the inner circumferential surface 21a of the hollow portion 21, and surrounding the hollow portion 21. Cooling water W is supplied to the cooling water cavity 24 via the cooling water supply pipe 26. The inner circumferential surface 21a of the mold 12 is cooled by the cooling water W contained in the cooling water cavity 24. This removes heat from the molten aluminum alloy M filling the hollow portion 21 of the mold 12 from the surface in contact with the inner circumferential surface 21a of the mold 12, causing a solidification shell to form on the surface of the molten aluminum alloy M.

[0069] The cooling water injection passage 25 directs cooling water W directly onto the aluminum alloy rod Z at the other end 12b of the mold 12 from the shower opening 25a facing the hollow portion 21, thereby cooling the aluminum alloy rod Z. The longitudinal cross-sectional shape of the cooling water injection passage 25 may be other than the circular shape of this embodiment, for example, a semicircle, a pear shape, or a horseshoe shape.

[0070] In this embodiment, the cooling water W supplied via the cooling water supply pipe 26 is first contained in the cooling water cavity 24 to cool the inner circumferential surface 21a of the hollow portion 21 of the mold 12, and then the cooling water W from the cooling water cavity 24 is injected from the cooling water injection passage 25 toward the aluminum alloy rod Z. However, it is also possible to configure the system so that these are supplied by separate cooling water supply pipes.

[0071] In this embodiment, the length from the position where the extension line of the central axis of the shower opening 25a of the cooling water injection passage 25 hits the surface of the cast aluminum alloy rod Z to the contact surface between the mold 12 and the refractory plate-like body 13 is referred to as the effective mold length L. The effective mold length L is preferably, for example, 10 mm or more and 40 mm or less. If the effective mold length L is less than 10 mm, casting becomes impossible because a good film cannot be formed. If the effective mold length L exceeds 40 mm, the effect of forced cooling becomes low, solidification by the mold wall becomes dominant, and the contact resistance between the mold 12 and the molten aluminum alloy M or between the mold 12 and the aluminum alloy rod Z increases, which may cause cracks on the casting surface or breakage inside the mold, etc., making the casting unstable, so it is not preferable.

[0072] It is preferable that the supply of the cooling water W to the cooling water cavity 24 and the injection of the cooling water W from the shower opening 25a of the cooling water injection passage 25 can be respectively controlled by a control signal from a control device (not shown).

[0073] As shown in FIG. 2, the cooling water cavity 24 is formed such that the inner bottom surface 24a near the hollow portion 21 of the mold 12 is parallel to the inner peripheral surface 21a of the hollow portion 21 of the mold 12. Here, the so-called parallel includes the case where the inner peripheral surface 21a of the hollow portion 21 of the mold 12 is formed at an elevation angle of 0° to 3° with respect to the inner bottom surface 24a of the cooling water cavity 24, that is, the case where the inner bottom surface 24a is inclined with respect to the inner peripheral surface 21a by more than 0° and up to 3°.

[0074] As shown in FIGS. 1 and 2, the cooling wall portion 27 of the mold 12, which is the portion where the inner bottom surface 24a of the cooling water cavity 24 and the inner peripheral surface 21a of the hollow portion 21 of the mold 12 face each other, has a heat flux value per unit area from the molten aluminum alloy M in the hollow portion 21 toward the cooling water W in the cooling water cavity 24 of 10×10 ５ W / m ２ or more and 50×10 ５ W / m ２ or less.

[0075] The thickness t of the cooling wall portion 27 of the mold 12 shown in Figure 2, that is, the distance between the inner bottom surface 24a of the cooling water cavity 24 and the inner circumferential surface 21a of the hollow portion 21 of the mold 12, is preferably formed to be in the range of 0.5 mm to 3.0 mm, and more preferably in the range of 0.5 mm to 2.5 mm, in order to make the cooling wall portion 27 of the mold 12 within the range of the above-mentioned heat flux value. Furthermore, it is preferable that the forming material for at least the cooling wall portion 27 of the mold 12 is selected such that, for example, the thermal conductivity is in the range of 100 W / m·K to 400 W / m·K, in order to make the cooling wall portion 27 of the mold 12 within the range of the above-mentioned heat flux value.

[0076] In Figure 1, the molten aluminum alloy M in the molten metal receiving section 11 is supplied from one end 12a of the mold 12, which is held so that the mold central axis C is approximately horizontal, via a refractory plate-like body 13, and is forcibly cooled at the other end 12b of the mold 12 to form an aluminum alloy rod Z. The aluminum alloy rod Z is drawn out at a constant speed by a drawing drive device (not shown) installed near the other end 12b of the mold 12. As a result, long aluminum alloy rods Z are continuously cast. The drawn-out aluminum alloy rod Z is then cut to a desired length, for example, by a synchronized cutting machine (not shown).

[0077] The composition ratio of the cast aluminum alloy rod Z can be confirmed, for example, by a photoelectric emission spectrometer as described in "JIS H 1305".

[0078] The difference in height between the liquid level of the molten aluminum alloy M stored in the molten metal receiving section 11 and the upper inner circumferential surface 21a of the mold 12 is preferably within the range of 0 mm to 250 mm, and more preferably within the range of 50 mm to 170 mm. By setting the height within this range, the pressure of the molten aluminum alloy M supplied into the mold 12 and the lubricating oil and the gas produced by the vaporization of the lubricating oil are suitably balanced, resulting in stable castability.

[0079] The liquid lubricant can be a vegetable oil, which acts as a lubricant. Examples of vegetable oils include rapeseed oil, castor oil, and salad oil. These are preferred because they have little adverse impact on the environment. The lubricant supply rate is preferably 0.05 mL / min to 5 mL / min, and more preferably 0.1 mL / min to 1 mL / min. If the lubricant supply rate is insufficient, the molten aluminum alloy M that will become the aluminum alloy rod Z may not solidify due to insufficient lubrication and may leak from the mold 12. If the lubricant supply rate is excessive, the excess may mix into the aluminum alloy rod Z and cause internal defects.

[0080] The casting speed, which is the speed at which the aluminum alloy rod Z is drawn out of the mold 12, is preferably 200 mm / min or more and 1500 mm / min or less, and more preferably 400 mm / min or more and 1000 mm / min or less. The reason for this is that within this range of casting speeds, the network structure of the precipitates in the aluminum alloy casting formed by casting becomes uniform and fine, increasing the resistance to deformation of the aluminum material at high temperatures and improving the high-temperature mechanical strength.

[0081] The amount of cooling water sprayed from the shower opening 25a of the cooling water injection passage 25 is preferably in the range of 10 L / min to 50 L / min per mold, and more preferably in the range of 25 L / min to 40 L / min. If the amount of cooling water is 10 L / min or more, the molten aluminum alloy M will not leak from the mold 12 without solidifying. Also, the surface of the cast aluminum alloy rod Z will not remelt and form an uneven structure, which is preferable as it will not remain as an internal defect. Furthermore, if the amount of cooling water is 50 L / min or less, the heat dissipation from the mold 12 will not be too large, which is preferable as it will not solidify prematurely.

[0082] The average temperature of the molten aluminum alloy M flowing from the molten metal receiving section 11 into the mold 12 is preferably, for example, 650°C to 750°C, and more preferably 680°C to 720°C. If the temperature of the molten aluminum alloy M is too low, coarse crystals may form in and in front of the mold 12, and these may be incorporated into the aluminum alloy rod Z as internal defects. On the other hand, if the temperature of the molten aluminum alloy M is too high, a large amount of hydrogen gas is easily incorporated into the molten aluminum alloy M. As a result, hydrogen gas may be incorporated into the aluminum alloy rod Z as porosity, and cavities may be formed inside.

[0083] The cooling wall 27 of the mold 12 receives heat from the molten aluminum alloy M, and this heat is cooled by the cooling water W contained in the cooling water cavity 24, thereby performing heat exchange. The state of heat exchange in the cooling wall 27 of the mold 12 was examined by focusing on the heat flux per unit area. Figure 3 is an explanatory diagram illustrating the heat flux of the cooling wall 27 of the horizontal continuous casting apparatus.

[0084] The heat flux per unit area is expressed by Fourier's law as follows: Q = -k × (T1 - T2) / L ... (1) Q: Heat flux k: Thermal conductivity (W / m·K) of the location through which heat passes (cooling wall portion 27 of the mold 12 in this embodiment) T1: Low-temperature side temperature of the location through which heat passes (cooling water contact temperature of the mold: inner bottom surface 24a of the cooling water cavity 24 in this embodiment) T2: High-temperature side temperature of the location through which heat passes (molten metal contact temperature of the mold: inner circumferential surface 21a of the hollow portion 21 of the mold 12 in this embodiment) L: Section length (mm) of the location through which heat passes (thickness of the mold wall: thickness t of the cooling wall portion 27 of the mold 12 in this embodiment)

[0085] Based on the mold material, thickness, and temperature measurement data, which yielded good results even with reduced lubrication oil during casting, the heat flux value per unit area was 10 × 10 ５ W / m ２By configuring the cooling wall portion 27 of the mold 12 as described above, seizing of the cast aluminum alloy rod Z can be prevented. Furthermore, the heat flux value per unit area is set to 50 × 10 to avoid casting problems where the molten aluminum alloy M solidifies in the mold 12 and the aluminum alloy rod Z becomes difficult to remove from the mold 12. ５ W / m ２ The following is preferable.

[0086] In this embodiment, when manufacturing the aluminum alloy rod Z, the molten aluminum alloy M stored in the molten metal receiving section 11 is continuously supplied to the hollow section 21 from one end 12a of the mold 12 using the horizontal continuous casting apparatus 10 described above. Cooling water W is supplied to the cooling water cavity 24, and lubricating fluid, such as lubricating oil, is supplied from the fluid supply pipe 22.

[0087] Then, the molten aluminum alloy M supplied into the hollow section 21 is cooled by the cooling wall section 27, where the heat flux value per unit area is 10 × 10 ５ W / m ２ The aluminum alloy rod Z is cast by cooling and solidifying under the above conditions. When casting the aluminum alloy rod Z, it is preferable that the wall temperature of the cooling wall portion 27 of the mold 12, which is cooled by the cooling water W, is 100°C or lower.

[0088] The aluminum alloy rod Z obtained in this way has a heat flux value per unit area of ​​10 × 10 in the cooling wall portion 27. ５ W / m ２ By cooling and solidifying under the above conditions, the adhesion of reaction products, such as carbides, resulting from contact between the lubricating oil gas and the molten aluminum alloy M is suppressed. As a result, there is no need to cut off carbides and other materials from the surface of the aluminum alloy rod Z, and the aluminum alloy rod Z can be manufactured in high yield.

[0089] The casting process for obtaining an aluminum alloy casting from molten aluminum alloy M having the above-described aluminum alloy composition obtained in the molten metal formation process is not limited to the horizontal continuous casting method described above. For example, known continuous casting methods such as vertical continuous casting can be used instead of horizontal continuous casting. Vertical continuous casting methods are classified into float method, hot top method, etc., depending on the method of supplying molten aluminum alloy M to the mold (casting mold 12). The case using the hot top method will be described below.

[0090] The casting apparatus used in the hot top method includes a mold, a molten metal receiving container (header), etc. The molten metal supplied to the receiving container passes through a spout and then through the header, where its flow rate is adjusted. It then enters a cylindrical mold that is installed almost horizontally, where it is forcibly cooled and a solidified shell forms on the outer surface of the molten metal.

[0091] Furthermore, cooling water is directly sprayed onto the casting as it is removed from the mold, allowing the metal to solidify inside the casting as it is continuously removed. Generally, metal components with good thermal conductivity are used for the mold. The mold has a hollow structure for introducing a coolant into it. The coolant used can be appropriately selected from those available industrially. Water is preferred as the coolant from the standpoint of ease of use.

[0092] The mold used in this embodiment can be appropriately selected from metals such as copper and aluminum, or graphite, from the viewpoint of heat transfer performance and durability at the contact area with the molten metal. The header is generally made of refractory material and is installed on top of the mold. The material and size of the header can be appropriately selected according to the composition range of the alloy to be cast and the dimensions of the casting, and are not particularly restricted.

[0093] The average cooling rate during casting can be appropriately selected from a generally recommended range, such as 10°C / sec to 300°C / sec. The casting speed can be appropriately selected from a range common in horizontal continuous casting, such as 100 mm / min to 600 mm / min.

[0094] (Homogenization Heat Treatment Process) In the homogenization heat treatment process, the aluminum alloy casting obtained in the casting process is subjected to homogenization heat treatment. This homogenizes the microsegregation that occurs when the molten aluminum alloy M solidifies, precipitates supersaturated solid solution elements, and changes the metastable phase to the equilibrium phase. The homogenization heat treatment process can be performed as needed, and the process can proceed directly to the forging process after the casting process.

[0095] In this embodiment, for example, it is preferable to perform a homogenization heat treatment on the aluminum alloy casting obtained in the casting process, holding it at a temperature of 370°C to 560°C for 2 to 10 hours. By performing the homogenization heat treatment within this temperature range, the aluminum alloy casting is sufficiently homogenized and solute atoms are sufficiently dissolved, and sufficient strength required can be obtained through subsequent aging treatment.

[0096] (Forging Process) In the forging process, the aluminum alloy casting, after casting or after the homogenization heat treatment process, is heated to a predetermined temperature and forged by applying pressure with a press to form a die. In this embodiment, the forging material obtained by shaping the aluminum alloy casting, after casting or after the homogenization heat treatment process, to a predetermined size is forged at a temperature of 450°C to 560°C. Since the forging temperature (starting temperature) is 450°C or higher, the deformation resistance is sufficiently low, and the forging process can be carried out effectively. Furthermore, since the forging temperature is 560°C or lower, the occurrence of defects such as forging cracks and / or eutectic melting can be suppressed.

[0097] In this embodiment, the aluminum alloy forged product undergoes a solution treatment process, a quenching process, and an aging process after forging. The solution treatment process, quenching process, and aging process may be performed as needed.

[0098] (Solution Treatment Process) In the solution treatment process, the aluminum alloy forged product after forging is subjected to solution treatment to alleviate the strain introduced by the forging process and to achieve solid solution of solute elements. In this embodiment, the aluminum alloy forged product after forging is subjected to solution treatment by holding it at a heating temperature of 530°C to 560°C for 0.3 hours to 3 hours. Since the heating temperature is 530°C or higher and the holding time at the heating temperature is 0.3 hours or longer, the solute elements can be sufficiently dissolved, and high strength can be achieved through age precipitation. Furthermore, since the heating temperature is 560°C or lower and the holding time at the heating temperature is 3 hours or less, eutectic melting and recrystallization can be prevented.

[0099] Furthermore, in the solution treatment process, the heating rate when raising the aluminum alloy forged product to the heating temperature after forging is preferably 5.0°C / min or higher. When the heating rate is 5.0°C / min or higher, coarse Mg ２ This prevents silicon from precipitation.

[0100] (Quenching Process) In the quenching process, the aluminum alloy forging in a solid solution state obtained in the solution treatment process is rapidly cooled to form a supersaturated solid solution. In this embodiment, within a time range of 5 seconds to 60 seconds after the completion of the solution treatment, the aluminum alloy forging after the solution treatment is immersed in a water tank containing quenching water, so that the entire surface of the aluminum alloy forging comes into contact with the quenching water, and is held for 1 minute to 30 minutes.

[0101] In this embodiment, the timing for immersing the aluminum alloy forging after solution treatment in a water tank is set to a range of 5 seconds to 60 seconds after the completion of the solution treatment, and the entire surface of the aluminum alloy forging is brought into contact with the quenching water and held for 1 minute or more, so that the aluminum alloy forging in a solid solution state can be rapidly cooled. The temperature of the water in the water tank into which the aluminum alloy forging after solution treatment is immersed is preferably between 20°C and 60°C.

[0102] (Aging Treatment Process) In the aging treatment process, the aluminum alloy forged product after the quenching treatment process is heated and held at a relatively low temperature to precipitate supersaturated dissolved elements, thereby imparting appropriate hardness to the aluminum alloy forged product.

[0103] In this embodiment, an aluminum alloy forging after the quenching process is subjected to an aging treatment in which it is held at a temperature of 170°C to 210°C for 0.5 hours to 7 hours. Since the aging treatment temperature is 170°C or higher and the holding time is 0.5 hours or longer, Mg ２ Si-based precipitates can be sufficiently grown, improving the tensile strength of aluminum alloy forgings. Moreover, since the aging treatment temperature is 210°C or lower and the holding time is 7 hours or lower, Mg ２ This method can suppress the formation of excessively coarse Si precipitates, thereby significantly improving the tensile strength of aluminum alloy forged products.

[0104] [Aluminum Alloy Forged Products] Next, an example of an aluminum alloy forged product manufactured using the manufacturing method for aluminum alloy forged products of the present invention will be described. Figure 4 is a perspective view showing an example of an aluminum alloy forged product manufactured using the manufacturing method for aluminum alloy forged products according to one embodiment of the present invention.

[0105] The aluminum alloy forged product 1a shown in Figure 4 has a long section 2 and connecting sections 4a and 4b connected to both ends of the long section 2 in the longitudinal direction, respectively. The long section 2 has a rectangular cross-section. The aluminum alloy forged product 1a shown in Figure 4 can be used, for example, as an I-shaped suspension arm.

[0106] The aluminum alloy forged product 1a of this embodiment has the above-described aluminum alloy composition, making it less prone to recrystallization during the manufacturing process and less likely to produce excessively coarse crystal grains. Moreover, the manufacturing method for the aluminum alloy forged product of this embodiment uses raw materials in which the total content of can scrap material, aluminum sash scrap material, and manufacturing process scrap material is within the range of 0.1% by mass to 90% by mass. Therefore, the aluminum alloy forged product 1a manufactured using the manufacturing method for the aluminum alloy forged product of this embodiment is an Al-Mg-Si type aluminum alloy forged product 1a that has low greenhouse gas emissions, is lightweight, and has excellent mechanical properties such as tensile properties, fatigue properties, toughness, and impact resistance, making it advantageous for use as a suspension arm in vehicles such as automobiles.

[0107] In the aluminum alloy forged product 1a shown in Figure 4, one of the two connecting parts 4a and 4b is cylindrical with a relatively small diameter, and the other connecting part 4b is cylindrical with a relatively large diameter, and the elongated part 2 has a shape in which the width widens from the end side of the one connecting part 4a to the end side of the other connecting part 4b. However, the aluminum alloy forged product manufactured using the manufacturing method of the aluminum alloy forged product of the present invention is not limited to the aluminum alloy forged product 1a shown in Figure 4. For example, one connecting part 4a and the other connecting part 4b of the aluminum alloy forged product 1a shown in Figure 4 may have the same shape. Also, the width of the elongated part 2 may be constant. Also, the elongated part 2 may have a curved shape. Three or more connecting parts may be formed.

[0108] Figure 5 is a plan view showing another example of an aluminum alloy forged product manufactured using a method for manufacturing aluminum alloy forged products according to one embodiment of the present invention. The aluminum alloy forged product 1b shown in Figure 5 has three connecting parts 4c, 4d, and 4e. Connecting parts 4c and 4d are connected by a long part 2. Connecting parts 4d and 4e are connected by a short part 5 that is relatively shorter than the long part 2. The aluminum alloy forged product 1b shown in Figure 5 can be used, for example, as an L-shaped suspension arm.

[0109] Figure 6 is a perspective view showing yet another example of an aluminum alloy forged product manufactured using a method for manufacturing aluminum alloy forged products according to one embodiment of the present invention. The aluminum alloy forged product 1c shown in Figure 6 has three connecting parts 4f, 4g, and 4h. Connecting parts 4f and 4g, and connecting parts 4f and 4h are connected by elongated parts 2. The aluminum alloy forged product 1c shown in Figure 6 can be used, for example, as an A-type suspension arm.

[0110] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims.

[0111] Examples 1 to 6, Comparative Examples 1 to 4: Can scrap material, aluminum sash scrap material, and manufacturing process scrap material were prepared, each having the aluminum alloy composition shown in Table 1. The aluminum alloy composition of these aluminum scrap materials was measured using an emission spectrometer.

[0112] The raw materials, consisting of can scrap material, aluminum sash scrap material, and manufacturing process scrap material in the proportions shown in Table 2, with the remainder being a new aluminum ingot, the elements shown below in their elemental form, and the compounds shown below, were melted at a temperature of 780°C or higher to obtain molten aluminum alloys for Examples 1 to 6 and Comparative Examples 1 to 4, having the aluminum alloy compositions shown in Table 3 (molten metal formation process).

[0113] The elemental elements used in the raw materials were Si, Cu, and Mg. The master alloys used in the raw materials were Al-Mn, Al-Fe, Al-Cr, and Al-Ti-B. The Zr and B content in the can scrap material, aluminum sash scrap material, and manufacturing process scrap material was not measured. Furthermore, the Zr contained in the aluminum alloy compositions of Examples 1 to 6 and Comparative Examples 2 to 4 shown in Table 3 originates from either the can scrap material, the aluminum sash scrap material, or the manufacturing process scrap material. In addition, the Zr contained in the aluminum alloy composition of Comparative Example 1, which does not contain aluminum scrap material, originates from the manufacturing process scrap material.

[0114] The aluminum alloy composition of the molten aluminum alloy shown in Table 3 was measured using an emission spectrometer. Table 2 shows the total content of aluminum scrap material in the raw materials (total content of can scrap, aluminum sash scrap, and manufacturing process scrap).

[0115]

[0116]

[0117]

[0118] The molten aluminum alloys of Examples 1 to 6 and Comparative Examples 1 to 4 obtained in this manner were solidified using the horizontal continuous casting apparatus shown in Figures 1 and 2 to obtain aluminum alloy castings having a cylindrical rod shape with a diameter of 80 mm (casting process). For the cylindrical aluminum alloy castings of Examples 1 to 6 and Comparative Examples 1 to 4, the amount of AlFeSi compound precipitated was calculated using the method described below. The results are shown in Table 2.

[0119] [Method for Calculating AlFeSi Compound Precipitation Amount] For cylindrical aluminum alloy castings, the phase fractions of each compound were calculated using thermodynamic calculations. Using these results, the amount of AlFeSi compound precipitated was determined by simulation. Specifically, the phase fractions of precipitates contained in the aluminum alloy castings were identified using a computational equilibrium phase diagram based on the CALPHAD (Calculation of PHA Diagrams, Computer Coupling of Phase Diagrams and Thermochemistry) method. The CALPHAD method is a technique for calculating phase diagrams from Gibbs energy, which represents the thermodynamic properties of the alloy.

[0120] Furthermore, for the cylindrical aluminum alloy castings of Examples 1 to 6 and Comparative Examples 1 to 4, greenhouse gas emissions were calculated and greenhouse gas reduction rates were determined using the methods described below. The results are shown in Table 2.

[0121] [Method for Calculating Greenhouse Gas Reduction Rate] Greenhouse gas emissions were calculated using the following formula (I), and the greenhouse gas reduction rate was determined using the following formula (II). Greenhouse gas emissions = {New aluminum ingot × New aluminum ingot GHG} + {(Can scrap material + Aluminum sash scrap material) × New aluminum ingot GHG × (1 / 30)} + {Manufacturing process scrap material × Manufacturing process scrap material GHG} (I) Greenhouse gas reduction rate (%) = 1 - {Greenhouse gas emissions / New aluminum ingot GHG} × 100 (II)

[0122] In formula (I), "new aluminum ingot" refers to the proportion (mass%) of new aluminum ingot contained in the raw materials of the aluminum alloy casting. "can scrap" refers to the proportion (mass%) of can scrap contained in the raw materials of the aluminum alloy casting. "aluminum sash scrap" refers to the proportion (mass%) of aluminum sash scrap contained in the raw materials of the aluminum alloy casting. "manufacturing process scrap" refers to the proportion (mass%) of manufacturing process scrap contained in the raw materials of the aluminum alloy casting.

[0123] In equations (I) and (II), "Aluminum Ingot GHG" represents the greenhouse gas (GHG) emission factor of aluminum ingots. In equation (I), the greenhouse gas (GHG) emission factors of can scrap and aluminum sash scrap were assumed to be 1 / 30 of that of aluminum ingot GHG. "Manufacturing Process Scrap GHG" represents the greenhouse gas (GHG) emission factor of manufacturing process scrap, which was assumed to be zero.

[0124] As shown in Table 2, the aluminum alloy forged products of Examples 1 to 6 had lower greenhouse gas emissions and a higher greenhouse gas reduction rate compared to the aluminum alloy forged product of Comparative Example 1. Furthermore, as shown in Table 2, the aluminum alloy forged products of Examples 1 to 6 had less AlFeSi compound precipitation compared to the aluminum alloy forged products of Comparative Examples 2 to 4. From this, it can be inferred that the aluminum alloy forged products of Examples 1 to 6 have better properties such as notch fatigue and stress corrosion cracking resistance compared to the aluminum alloy forged products of Comparative Examples 2 to 4.

[0125] 1a, 1b, 1c...Forged aluminum alloy parts 2...Long section 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h...Connecting section 5...Short section 10...Horizontal continuous casting apparatus 11...Molten metal receiving section (tundish) 11a...Molten metal inlet section 11b...Molten metal holding section 11c...Outlet section 12...Mold 12a...One end 12b...Other end 13...Refractory plate-shaped body (insulating member) 13a...Pouring passage 21...Hollow section 21a...Inner circumferential surface 22...Fluid supply pipe 22a...Lubricant supply port 23...Cooling device 24...Cooling water cavity 24a...Inner bottom surface 25...Cooling water injection passage 25a...Shower opening 26...Cooling water supply pipe 27...Cooling wall section M...Molten aluminum alloy W...Cooling water Z... Aluminum alloy rod

Claims

1. The process includes: a molten metal forming step of melting raw materials to obtain molten aluminum alloy; a casting step of solidifying the molten aluminum alloy to obtain an aluminum alloy casting; and a forging step of forging the aluminum alloy casting to obtain a forged product, wherein the raw materials contain aluminum scrap material consisting of one or more types selected from can scrap material in the range of 0.1% by mass or more and 40% by mass or less; aluminum sash scrap material in the range of 0.1% by mass or more and 30% by mass or less; and manufacturing process scrap material in the range of 0.1% by mass or more and 80% by mass or less, the total content of the aluminum scrap material in the raw materials is in the range of 0.1% by mass or more and 90% by mass or less, and the molten aluminum alloy contains Cu in the range of 0.25% by mass or more and 0.55% by mass or less, Mg in the range of 0.55% by mass or more and 1.30% by mass or less, and Si in the range of 0.80% by mass or more and 1.24% by mass or less. A method for manufacturing aluminum alloy forgings, having an aluminum alloy composition containing Mn in the range of 0.45% by mass or more and 0.76% by mass or less, Fe in the range of 0.40% by mass or more and 0.55% by mass or less, Zn in the range of 0.250% by mass or less, Cr in the range of 0.050% by mass or more and 0.25% by mass or less, Ti in the range of 0.005% by mass or more and 0.1% by mass or less, B in the range of 0.0010% by mass or more and 0.030% by mass or less, and Zr in the range of 0.0010% by mass or more and 0.050% by mass or less, with the remainder being Al and unavoidable impurities.

2. The method for manufacturing an aluminum alloy forged product according to claim 1, wherein the ratio of Fe content to Mn content, Fe / Mn, is within the range of 0.3 or more and 1.3 or less by mass ratio.

3. The method for manufacturing an aluminum alloy forged product according to claim 1 or claim 2, wherein the total content of the aluminum scrap material in the raw materials is 0.3% by mass or more.

4. A method for manufacturing an aluminum alloy forged product according to claim 1 or claim 2, comprising: a solution treatment step of performing a solution treatment on the aluminum alloy forged product after forging; a quenching step of performing a hardening treatment on the aluminum alloy forged product after the solution treatment; and an aging treatment step of performing an aging treatment on the aluminum alloy forged product after the hardening treatment.

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