Aluminum cast alloy deformed structure and method of manufacturing the same

Abstract

The present invention provides an aluminum alloy cast body having improved formability through local remelting and a method for manufacturing the same. A method for manufacturing an aluminum alloy cast body according to one embodiment of the present invention comprises: a casting step of forming an aluminum alloy cast material by casting a molten metal formed by melting alloying elements of an aluminum alloy; a local remelting step of locally remelting a forming target area of ​​the aluminum alloy cast material; a solution treatment step of solution treating the locally remelted aluminum alloy cast material; an aging treatment step of aging the solution-treated aluminum alloy cast material; and a forming step of forming a forming target area of ​​the aging-treated aluminum alloy cast material.

Description

Technology Field

[0001] The technical concept of the present invention relates to aluminum alloys, and more specifically, to an aluminum alloy cast body having improved formability by local remelting and a method for manufacturing the same. Background Technology

[0002] Recently, driven by a global trend to improve fuel efficiency through the lightweighting of transportation equipment components, the demand for lightweight and high-strength materials is increasing. Among these, the use of aluminum alloys is rapidly rising due to their excellent castability, processability, mechanical properties, durability limits, and recyclability.

[0003] Automotive suspension components have traditionally been manufactured primarily using aluminum forgings; however, there has recently been an increasing trend toward using aluminum castings to reduce manufacturing costs and carbon emissions. Nevertheless, compared to aluminum forgings, aluminum castings are brittle and have low elongation, making plastic deformation processes such as swaging difficult and thus limiting their application. Therefore, microstructural control, such as grain refinement, is required to improve the formability of aluminum alloy castings. The problem to be solved

[0004] The technical problem that the technical concept of the present invention aims to solve is to provide an aluminum alloy cast body having improved formability through local remelting and a method for manufacturing the same.

[0005] However, these tasks are exemplary, and the technical concept of the present invention is not limited thereto. means of solving the problem

[0006] According to one embodiment of the present invention, a method for manufacturing an aluminum alloy casting body may include: a casting step of forming an aluminum alloy casting material by casting a molten metal formed by melting alloying elements of an aluminum alloy; a local remelting step of locally remelting a molding target area of ​​the aluminum alloy casting material; a solution treatment step of solution treating the locally remelted aluminum alloy casting material; an aging treatment step of aging the solution-treated aluminum alloy casting material; and a molding step of molding a molding target area of ​​the aging-treated aluminum alloy casting material.

[0007] According to one embodiment of the present invention, in the local remelting step, the molding target area may be heated to a range of 600°C to 800°C.

[0008] According to one embodiment of the present invention, in the local remelting step, the molding exclusion area may be maintained at a temperature in the range of 20°C to 200°C.

[0009] According to one embodiment of the present invention, the local remelting step may be performed by laser beam irradiation, metal inert gas (MIG) welding, tungsten inert gas (TIG) welding, or a combination thereof.

[0010] According to one embodiment of the present invention, the solution treatment step may be performed for 30 minutes to 8 hours at a temperature in the range of 420℃ to 540℃.

[0011] According to one embodiment of the present invention, the aging treatment step may be performed for 5 to 30 hours at a temperature in the range of 100°C to 200°C.

[0012] According to one embodiment of the present invention, the molding step may be performed by performing swaging molding on the molding target area.

[0013] According to one embodiment of the present invention, the swaging forming can be performed at a rotational speed of a swaging tool of 800 RPM to 1200 RPM, a pressure holding time in the range of 0.1 seconds to 1 second, and a lowering speed of a swaging tool in the range of 0.4 mm / second to 0.8 mm / second.

[0014] According to one embodiment of the present invention, the aluminum alloy molded body may include at least one of AC1B alloy, AC2A alloy, AC2B alloy, AC3A alloy, AC4A alloy, AC4C alloy, AC4CH alloy, AC4B alloy, AC4D alloy, AC7A alloy, AC8A alloy, AC8B alloy, AC8C alloy, AC9A alloy, and AC9B alloy.

[0015] According to one embodiment of the present invention, the aluminum alloy molded body may comprise 6 weight% to 10 weight% silicon (Si), 0.2 weight% to 0.5 weight% magnesium (Mg), and the remainder being aluminum (Al) and other unavoidable impurities.

[0016] According to one embodiment of the present invention, the aluminum alloy molded body may further include at least one of copper (Cu) in an amount greater than 0 wt% to 0.2 wt%, zinc (Zn) in an amount greater than 0 wt% to 0.3 wt%, iron (Fe) in an amount greater than 0 wt% to 0.5 wt%, manganese (Mn) in an amount greater than 0 wt% to 0.6 wt%, titanium (Ti) in an amount greater than 0 wt% to 0.2 wt%, and chromium (Cr) in an amount greater than 0 wt% to 0.05 wt%.

[0017] According to one embodiment of the present invention, an aluminum alloy cast molded body manufactured by the above-described manufacturing method can be provided.

[0018] According to one embodiment of the present invention, the aluminum alloy cast molded body may have an average secondary dendritic spacing of less than 20 μm in the remelted area.

[0019] According to one embodiment of the present invention, the aluminum alloy casting molded body may include process silicon with an average particle size of less than 4 μm to 8 μm in the remelted area.

[0020] According to one embodiment of the present invention, the aluminum alloy cast body may have a hardness in the range of 100 HB to 120 HB in the remelted area.

[0021] According to one embodiment of the present invention, the aluminum alloy cast body may satisfy a yield strength (YS): 220 MPa or more, a tensile strength (UTS): 300 MPa or more, and an elongation (EL): 6% or more. Effects of the invention

[0022] According to the technical concept of the present invention, a method for manufacturing an aluminum alloy cast body can increase swaging formability by remelting the molding target area of ​​the aluminum alloy cast body, followed by solution treatment and aging treatment. Accordingly, as grain refinement is achieved through such remelting, the brittleness of the aluminum matrix is ​​reduced, thereby improving the ductility of the aluminum alloy cast body. The aluminum alloy cast body can be applied to automotive parts, such as compression arms, rear lower arms, etc.

[0023] The effects of the present invention described above are illustrative and the scope of the present invention is not limited by these effects. Brief explanation of the drawing

[0024] FIG. 1 is a process flowchart schematically illustrating a method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a local remelting process applied to a method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a swaging forming process applied to a method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating a method of forming an aluminum alloy cast body by a swaging forming process applied to a method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention. FIG. 5 is a photograph of the upper exterior of an aluminum alloy casting molded body manufactured by a method for manufacturing an aluminum alloy casting molded body according to an embodiment of the present invention. FIG. 6 is an optical microscope image showing a molded area of ​​an aluminum alloy cast body manufactured by a method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention. FIG. 7 is an optical microscope image showing the microstructure of the molded region of an aluminum alloy cast body manufactured by the method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention. Specific details for implementing the invention

[0025] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The embodiments of the present invention are provided to more fully explain the technical concept of the present invention to those skilled in the art, and the following embodiments may be modified in various different forms, and the scope of the technical concept of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to make the present disclosure more faithful and complete and to fully convey the technical concept of the present invention to those skilled in the art. In this specification, the same reference numerals denote the same elements throughout. Furthermore, various elements and areas in the drawings are depicted schematically. Accordingly, the technical concept of the present invention is not limited by the relative sizes or spacing depicted in the attached drawings.

[0026] Hereinafter, an aluminum alloy cast molded body, which is one aspect of the present invention, will be described.

[0027] Aluminum alloy cast molded body

[0028] An aluminum alloy casting molded body, which is one aspect of the present invention, may include various aluminum alloys for casting. For example, the aluminum alloy casting molded body comprises AC1B alloy (Al-Cu-Mg alloy), AC2A alloy (Al-Cu-Si alloy), AC2B alloy (Al-Cu-Si alloy), AC3A alloy (Al-Si alloy), AC4A alloy (Al-Si-Mg alloy), AC4C alloy (Al-Si-Mg alloy), AC4CH alloy (Al-Si-Mg alloy), AC4B alloy (Al-Si-Cu alloy), AC4D alloy (Al-Si-Cu-Mg alloy), AC7A alloy (Al-Mg alloy), AC8A alloy (Al-Si-Ni-Cu-Mg alloy), AC8B alloy (Al-Si-Ni-Cu-Mg alloy), AC8C alloy (Al-Si-Ni-Cu-Mg alloy), AC9A alloy (Al-Si-Cu-Mg-Ni alloy), and AC9B alloy It may include at least one of (Al-Si-Cu-Mg-Ni alloys).

[0029] In the following, we will describe by example the case where the above-mentioned aluminum alloy cast body is the AC4C alloy, which is the Al-Si-Mg-based alloy.

[0030] The above aluminum alloy cast body may contain 6 to 10 weight percent silicon (Si), 0.2 to 0.5 weight percent magnesium (Mg), and the remainder being aluminum (Al) and other unavoidable impurities.

[0031] In addition, the aluminum alloy cast body may further include at least one of copper (Cu) in an amount greater than 0 wt% to 0.2 wt%, zinc (Zn) in an amount greater than 0 wt% to 0.3 wt%, iron (Fe) in an amount greater than 0 wt% to 0.5 wt%, manganese (Mn) in an amount greater than 0 wt% to 0.6 wt%, titanium (Ti) in an amount greater than 0 wt% to 0.2 wt%, and chromium (Cr) in an amount greater than 0 wt% to 0.05 wt%.

[0032] The role and content of each component included in the aluminum alloy cast body according to the present invention are described below.

[0033] Silicon (Si): 6 wt% to 10 wt%

[0034] Silicon is an element that improves the fluidity, castability, and tensile strength of aluminum alloy cast bodies. If the silicon content is less than 6 weight%, castability may be reduced and it may be difficult to secure strength. If the silicon content exceeds 10 weight%, the content of process silicon that propagates cracks increases, which may degrade mechanical properties. Therefore, it is preferable to add silicon in an amount of 6 weight% to 10 weight% of the total weight of the aluminum alloy cast body.

[0035] Magnesium (Mg): 0.2 wt% ~ 0.5 wt%

[0036] Magnesium is a solid solution strengthening element that is dissolved in the matrix to improve strength and formability. If the magnesium content is less than 0.2 weight%, it may be difficult to secure strength and improve formability. If the magnesium content exceeds 0.5 weight%, the elongation is significantly reduced, which may cause cracking. Therefore, it is preferable to add magnesium in an amount of 0.2 weight% to 0.5 weight% of the total weight of the aluminum alloy cast body.

[0037] Copper (Cu): 0.2 wt% or less

[0038] Copper is an element that improves the strength and corrosion resistance of aluminum alloy cast bodies. If the copper content exceeds 0.2 weight%, cracks may form due to segregation during casting. Therefore, copper can be added in an amount of 0.2 weight% or less of the total weight of the aluminum alloy cast body, and it is preferable to add it in an amount greater than 0 weight% and less than or equal to 0.2 weight%.

[0039] Zinc (Zn): 0.3 wt% or less

[0040] Zinc is an element that improves the castability and strength of aluminum alloy cast bodies. If the zinc content exceeds 0.3 weight%, the fluidity of the molten metal decreases, which may result in poor castability, and segregation may occur in the center of the manufactured alloy, which may degrade mechanical properties. Therefore, zinc can be added in an amount of 0.3 weight% or less of the total weight of the aluminum alloy cast body, and it is preferable to add it in an amount greater than 0 weight% and less than or equal to 0.3 weight%.

[0041] Iron (Fe): 0.5 wt% or less

[0042] Since iron precipitates as an intermetallic compound, it is an element that increases strength while minimizing the decrease in thermal conductivity of aluminum alloy cast bodies. If the iron content exceeds 0.5 weight%, segregation may occur in the center of the manufactured alloy, which can degrade mechanical properties. Therefore, iron can be added in an amount of 0.5 weight% or less of the total weight of the aluminum alloy cast body, and it is preferable to add it in an amount greater than 0 weight% and less than or equal to 0.5 weight%.

[0043] Manganese (Mn): 0.6 wt% or less

[0044] Manganese (Mn) can increase the elastic modulus by forming intermetallic compounds on the AlMnSi phase. If the manganese content exceeds 0.6 wt%, the intermetallic compounds become coarsenous, which lowers castability and degrades mechanical properties; in particular, brittleness may increase due to a decrease in elongation, and primary silicon may also become coarsenous. Therefore, manganese can be added in an amount of 0.6 wt% or less of the total weight of the aluminum alloy cast body, and it is preferable to add it in an amount greater than 0 wt% to 0.6 wt%.

[0045] Titanium (Ti): 0.2 wt% or less

[0046] Titanium is an element that can improve mechanical properties and corrosion resistance by precipitating in the aluminum matrix metal as intermetallic compounds such as Al3Ti, enable grain refinement of the aluminum alloy, and prevent cracking in the casting. If the titanium content exceeds 0.2 weight%, coarse intermetallic compounds may be formed, which may reduce ductility. Therefore, titanium may be added in an amount of 0.2 weight% or less of the total weight of the aluminum alloy casting, and it is preferable to add it in an amount greater than 0 weight% to 0.2 weight%.

[0047] Chromium (Cr): 0.05 wt% or less

[0048] Chromium has the effect of suppressing recrystallization and refining the grain size. If the chromium content exceeds 0.05 weight%, coarse intermetallic compounds may be formed, which may reduce ductility. Therefore, chromium can be added in an amount of 0.05 weight% or less of the total weight of the aluminum alloy cast body, and it is preferable to add it in an amount greater than 0 weight% to 0.05 weight%.

[0049] The remaining component of the above aluminum alloy cast body is aluminum (Al). However, since unintended impurities from raw materials or the surrounding environment may inevitably be incorporated during the normal manufacturing process, they cannot be excluded. As these impurities are known to any skilled person in the normal manufacturing process, all details thereof are not specifically mentioned in this specification.

[0050] The above aluminum alloy cast body can be manufactured using the following manufacturing method.

[0051] The above aluminum alloy cast body may have a remelting region in which local remelting is performed and microstructure refinement is achieved, and an untreated region in which local remelting is not performed.

[0052] The aluminum alloy cast molded body may have an average secondary dendritic spacing of, for example, less than 20 μm in the remelting region, which is the remelted region. The aluminum alloy cast molded body may have an average secondary dendritic spacing in the range of, for example, 10 μm to less than 20 μm in the remelting region. On the other hand, in the untreated region, which is the unremelted region, it may have an average secondary dendritic spacing in the range of, for example, 20 μm to 35 μm.

[0053] The above aluminum alloy cast body may include eutectic silicon with an average particle size in the range of, for example, 4 μm to less than 8 μm in the remelted region, which is the remelted region. On the other hand, in the above untreated region, which is the unremelted region, it may include eutectic silicon with an average particle size in the range of, for example, 8 μm to 12 μm.

[0054] The above aluminum alloy cast body may have a hardness in the remelting region, for example, in the range of 100 HB to 120 HB. On the other hand, in the untreated region, for example, in the unremelted region, it may have a hardness in the range of 50 HB to 70 HB. Here, "HB" refers to Brinell hardness.

[0055] The above aluminum alloy cast body may satisfy, for example, a yield strength (YS): 220 MPa or more, a tensile strength (UTS): 300 MPa or more, and an elongation (EL): 6% or more, and may satisfy, for example, a yield strength (YS): 220 MPa to 300 MPa, a tensile strength (UTS): 300 MPa to 400 MPa, and an elongation (EL): 6% to 12%.

[0056] Method for manufacturing an aluminum alloy cast molded body

[0057] The following describes in detail the method for manufacturing an aluminum alloy cast body.

[0058] FIG. 1 is a process flowchart schematically showing a method (S200) for manufacturing an aluminum alloy cast body according to an embodiment of the present invention.

[0059] Referring to FIG. 1, the method for manufacturing the aluminum alloy cast body (S200) includes a casting step (S210), a local remelting step (S220), a solution treatment step (S230), an aging treatment step (S240), and a forming step (S250).

[0060] The above casting step (S210) is a step of casting after forming a molten metal by melting the alloy elements constituting the aluminum alloy casting molded body.

[0061] In the casting step (S210), for example, a molten metal may be formed by melting alloying elements of an aluminum alloy comprising 6 wt% to 10 wt% silicon (Si), 0.2 wt% to 0.5 wt% magnesium (Mg), and the remainder being aluminum (Al) and other unavoidable impurities. Additionally, the molten metal may further include, as the alloying elements, at least one of copper (Cu) in greater than 0 wt% to 0.2 wt%, zinc (Zn) in greater than 0 wt% to 0.3 wt%, iron (Fe) in greater than 0 wt% to 0.5 wt%, manganese (Mn) in greater than 0 wt% to 0.6 wt%, titanium (Ti) in greater than 0 wt% to 0.2 wt%, and chromium (Cr) in greater than 0 wt% to 0.05 wt%.

[0062] The above alloying elements can be melted in a graphite crucible using a high-frequency induction melting furnace or an electric resistance furnace at a temperature at which the alloying elements are completely melted. This can be done by adding the alloying elements individually, or by adding all or part of the alloying elements in the form of a master alloy. For example, silicon can be added to the molten aluminum in a pure elemental state, or in the form of an aluminum-silicon master alloy with a high silicon content. This method can also be applied to other additive elements such as magnesium and copper.

[0063] An aluminum alloy casting can be formed by casting the above molten metal by methods such as injecting it into a cavity within a mold and solidifying it. The aluminum alloy casting can be produced by gravity casting, low-pressure casting, or differential pressure casting. However, this is exemplary, and the technical concept of the present invention is not limited thereto.

[0064] After performing the casting step (S210), the aluminum alloy casting material may be cooled to room temperature, for example, to a temperature in the range of 0°C to 40°C. The cooling may be performed by various methods such as water quenching, air cooling, furnace cooling, etc.

[0065] In the above local remelting step (S220), remelting is performed to remelt the molding target area of ​​the aluminum alloy casting. In the above local remelting step (S220), the molding target area may be melted by various heat sources and heated only to a level that maintains the external shape. In the above local remelting step (S220), the molding target area may be heated to a temperature in the range of, for example, 600°C to 800°C. The aluminum matrix structure heated by the above local remelting step (S220) may be softened, and the spheroidization of eutectic silicon may be optimized. The above local remelting step (S220) may be performed by providing a heat source by laser beam irradiation, metal inert gas (MIG) welding, tungsten inert gas (TIG) welding, or a combination thereof.

[0066] In the above local remelting step (S220), the molding exclusion area, which is not the molding target area, can be maintained at a temperature where the remelting effect does not occur, for example, at a temperature in the range of 20°C to 200°C.

[0067] After performing the above-mentioned local remelting, the aluminum alloy casting can be cooled to room temperature, for example, to a temperature in the range of 0°C to 40°C. The cooling can be performed by various methods such as water quenching, air cooling, furnace cooling, etc.

[0068] In the solution treatment step (S230), the locally remelted aluminum alloy casting is solution treated. The solution treatment step (S230) may be performed by heating the aluminum alloy casting and maintaining it at a temperature in the range of, for example, 420°C to 540°C for 30 minutes to 8 hours, or at, for example, 470°C for 1 hour. The compositional uniformity of the aluminum matrix of the aluminum alloy casting may be improved by the solution treatment.

[0069] After performing the solution treatment step (S230), the aluminum alloy casting can be cooled to room temperature, for example, to a temperature in the range of 0°C to 40°C. The cooling can be performed by various methods such as water quenching, air cooling, furnace cooling, etc.

[0070] In the aging treatment step (S240), the solution-treated aluminum alloy casting is aged. The aging treatment step (S240) can be performed by heating the aluminum alloy casting and maintaining it at a temperature in the range of, for example, 100°C to 200°C for 5 to 30 hours, or at, for example, 160°C for 12 hours. Through the aging treatment, solute elements may be extracted from the supersaturated solid solution to form an aged precipitate phase.

[0071] After performing the aging treatment step (S240), the aluminum alloy casting may be cooled to room temperature, for example, to a temperature in the range of 0°C to 40°C. The cooling may be performed by various methods such as water quenching, air cooling, furnace cooling, etc.

[0072] The solution treatment step (S230) and the aging treatment step (S240) may be performed sequentially. Alternatively, only the solution treatment step (S230) may be performed, or only the aging treatment step (S240) may be performed.

[0073] The above forming step (S250) forms a forming target area of ​​the aluminum alloy casting. The above forming step (S250) may be performed by swaging forming. The swaging forming may be performed with a rotational speed of a swaging tool of 800 RPM to 1200 RPM, a pressure holding time in the range of 0.1 seconds to 1 second, and a lowering speed of a swaging tool in the range of 0.4 mm / second to 0.8 mm / second. However, this is exemplary and the technical concept of the present invention is not limited thereto.

[0074] An aluminum alloy cast body can be manufactured by the method for manufacturing an aluminum alloy cast body described above.

[0075] FIG. 2 is a schematic diagram illustrating a local remelting process applied to a method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention.

[0076] Referring to FIG. 2, an aluminum alloy casting (100) is loaded into a local remelting device (90). The local remelting device (90) may have a heat source section (92) positioned on the upper side and a cooling section (94) positioned on the lower side. The molding target area (110) of the aluminum alloy casting (100) may be locally heated and remelted by the heat source provided by the heat source section (92). On the other hand, the molding exclusion area (120) of the aluminum alloy casting (100) may be cooled by the cooling section (94) and maintained at room temperature or at a temperature lower than that of the molding target area (110). Alternatively, the cooling section (94) may be omitted, and the molding exclusion area (120) may be cooled as it is exposed to the outside. The configuration of the heat source section (92) and the cooling section (94) may be implemented in various forms. The heat source (92) may be composed of a laser device that irradiates a laser beam, or a fusion welding device that performs metal inert gas (MIG) welding or tungsten inert gas (TIG) welding.

[0077] FIG. 3 is a schematic diagram illustrating a swaging forming process applied to a method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention.

[0078] FIG. 4 is a schematic diagram illustrating a method of forming an aluminum alloy cast body by a swaging forming process applied to a method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention.

[0079] Referring to FIGS. 3 and 4, an aluminum alloy casting (100) is mounted on a lower jig (32), and after covering it with a cap (34), a swaging tool (36) is placed on the upper side. Subsequently, the swaging tool (36) is rotated and pressed to swage-form the forming target area (110) of the aluminum alloy casting (100). For example, by pressing and bending the protrusion of the forming target area (100) in the inner diameter direction, it can be formed into a shape that interlocks with the cap (34).

[0080] Experimental Example

[0081] Hereinafter, experimental examples regarding an aluminum alloy cast body according to the technical concept of the present invention will be described in detail. The following experimental examples are provided as illustrations to explain the technical concept of the present invention, and the present invention is not limited to the experimental examples described below.

[0082] AC4C alloy was prepared as the raw material for an aluminum alloy cast body. The composition and components of the aluminum alloy cast body included 8 wt% silicon (Si), 0.4 wt% magnesium (Mg), and the remainder being aluminum (Al) and other unavoidable impurities.

[0083] An aluminum alloy casting was manufactured by casting the above aluminum alloy.

[0084] Next, the forming target area of ​​the aluminum alloy casting was heated by irradiating it with a laser beam to remelt it. The temperature at which the forming target area was remelted was approximately 630°C.

[0085] Next, the above aluminum alloy casting was cooled to room temperature.

[0086] Next, the remelted aluminum alloy casting was heated and solution treated at approximately 470°C for about 1 hour, and then water-cooled. Then, it was heated again and aged at approximately 120°C for about 12 hours, that is, the aluminum alloy casting was T6 heat-treated.

[0087] Next, the aluminum alloy casting was swaged to form an aluminum alloy casting body. The swaging was performed at a swaging tool rotation speed of about 1000 RPM, a pressure holding time of about 0.5 seconds, and a swaging tool lowering speed of about 0.6 mm / second.

[0088] Table 1 is a table showing the process conditions of an aluminum alloy cast body manufactured by the method for manufacturing an aluminum alloy cast body according to one embodiment of the present invention, compared with a comparative example.

[0089] process Quantity (pieces) Remelting Solution treatment statute of limitations processing Swaging temperature Comparative Example 1 3 × ○ × 20℃ Comparative Example 2 3 × ○ × 20℃ Comparative Example 3 3 ○ ○ × 20℃ Examples 3 ○ ○ ○ 20℃

[0090] Referring to Table 1, Comparative Example 1 is a case where solution treatment was performed but remelting and aging treatments were not performed. Comparative Examples 1 and 2 are cases where solution treatment was performed under the same conditions as the Example but remelting and aging treatments were not performed. Comparative Example 3 is a case where remelting and solution treatment were performed under the same conditions as the Example but aging treatments were not performed. The Example is a case where remelting, solution treatment, and aging treatments were all performed. Both the Comparative Example and the Example performed swaging molding at room temperature (20°C).

[0091] FIG. 5 is a photograph of the upper exterior of an aluminum alloy casting molded body manufactured by a method for manufacturing an aluminum alloy casting molded body according to an embodiment of the present invention.

[0092] Referring to FIG. 5, surface peeling occurred in Comparative Example 1 and Comparative Example 2. Surface peeling and cracking occurred in Comparative Example 3. On the other hand, no surface peeling or cracking was observed in the Example.

[0093] FIG. 6 is an optical microscope image showing a molded area of ​​an aluminum alloy cast body manufactured by a method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention.

[0094] Referring to FIG. 6, optical microscope images of regions "A", "B", and "C" are shown as formed areas of an aluminum alloy cast body. In the case of Comparative Example 1, surface delamination appeared in region "B". In the case of Comparative Example 2, surface delamination appeared in region "C". On the other hand, such surface delamination was not observed in the example.

[0095] FIG. 7 is an optical microscope image showing the microstructure of the molded region of an aluminum alloy cast body manufactured by the method for manufacturing an aluminum alloy cast body according to an embodiment of the present invention.

[0096] Referring to FIG. 7, optical microscope images of regions "D" and "E" are shown as formed areas of an aluminum alloy cast body. In the case of Comparative Example 1, a crack was found at the interface of the process silicon in region "E". This indicates that if the solution treatment is performed excessively to disrupt the process silicon network, cracks may occur due to the coarsening of the process silicon. In the case of Comparative Example 2, no defects in the microstructure other than surface peeling were found. No defects in the microstructure were found in the Examples.

[0097] Table 2 is a table showing the characteristics of an aluminum alloy cast body manufactured by the method for manufacturing an aluminum alloy cast body according to one embodiment of the present invention, compared with a comparative example.

[0098] classification Internal cracks (number) Central crack (number) Central detachment (individual) SDAS(μm) Average particle size of process silicon (μm) Hardness (HB) Comparative Example 1 0 2 1 36 17 50 Comparative Example 2 0 3 1 33 13 64 Comparative Example 3 0 49 0 - - - Examples 0 0 0 14 6 116

[0099] Referring to Table 2, neither the comparative examples nor the embodiments developed internal cracks in region "A" of FIG. 6. However, in the comparative examples, central cracks developed in region "B" of FIG. 6, and central delamination also occurred. In particular, Comparative Example 3, which did not undergo aging treatment after remelting, developed a very large number of central cracks.

[0100] The average secondary dendritic spacing (SDAS) was 14 μm in the remelted region of the example, which was very low compared to the comparative example. In the non-remelted region of the example, the average secondary dendritic spacing was 33 μm, which is similar to that of the comparative example.

[0101] The average particle size of the process silicon was 6 μm in the remelted region of the example, which was very small compared to the comparative example. In the region not remelted in the example, the average particle size of the process silicon was 12 μm, which is similar to that of the comparative example. Therefore, since it is desirable for the average particle size of the process silicon to be small to suppress crack initiation and propagation, it may be in the range of 5 μm to 12 μm.

[0102] The hardness of the example was 116 HB, which is very high compared to the comparative example.

[0103] It will be obvious to those skilled in the art that the technical concept of the present invention described above is not limited to the aforementioned embodiments and attached drawings, and that various substitutions, modifications, and changes are possible within the scope of the technical concept of the present invention.

Claims

Claim 1 The method comprises: a casting step of forming an aluminum alloy casting by casting a molten metal formed by melting alloying elements of an aluminum alloy; a local remelting step of locally remelting a forming target area of ​​the aluminum alloy casting; a solution treatment step of solution treating the locally remelted aluminum alloy casting; an aging treatment step of aging the solution-treated aluminum alloy casting; and a forming step of forming a forming target area of ​​the aged aluminum alloy casting, wherein in the local remelting step, the forming target area is 600 o C to 800 o Heated to a C range, and the molding exclusion area is 20 o C to 200 o A method for manufacturing an aluminum alloy casting molded body maintained at a temperature in the range of C, wherein the aluminum alloy casting molded body manufactured by the method for manufacturing the aluminum alloy casting molded body has an average secondary dendritic spacing of less than 20 μm in the remelted region and comprises process silicon with an average particle size of less than 8 μm. Claim 2 delete Claim 3 delete Claim 4 A method for manufacturing an aluminum alloy cast body, wherein the local remelting step is performed by laser beam irradiation, metal inert gas (MIG) welding, tungsten inert gas (TIG) welding, or a mixture thereof. Claim 5 A method for manufacturing an aluminum alloy cast molded body according to claim 1, wherein the solution treatment step is performed at a temperature in the range of 420℃ to 540℃ for 30 minutes to 8 hours. Claim 6 A method for manufacturing an aluminum alloy cast molded body according to claim 1, wherein the aging treatment step is performed for 5 to 30 hours at a temperature in the range of 100℃ to 200℃. Claim 7 A method for manufacturing an aluminum alloy cast body, wherein, in claim 1, the forming step is performed by performing swaging forming on the forming target area. Claim 8 A method for manufacturing an aluminum alloy cast body according to claim 7, wherein the swaging forming is performed at a rotational speed of a swaging tool of 800 RPM to 1200 RPM, a pressure holding time in the range of 0.1 second to 1 second, and a lowering speed of a swaging tool in the range of 0.4 mm / second to 0.8 mm / second. Claim 9 A method for manufacturing an aluminum alloy casting molded body according to claim 1, wherein the aluminum alloy casting molded body comprises at least one of AC1B alloy, AC2A alloy, AC2B alloy, AC3A alloy, AC4A alloy, AC4C alloy, AC4CH alloy, AC4B alloy, AC4D alloy, AC7A alloy, AC8A alloy, AC8B alloy, AC8C alloy, AC9A alloy, and AC9B alloy. Claim 10 A method for manufacturing an aluminum alloy cast body according to claim 1, wherein the aluminum alloy cast body comprises 6 weight% to 10 weight% silicon (Si), 0.2 weight% to 0.5 weight% magnesium (Mg), and the remainder being aluminum (Al) and other unavoidable impurities. Claim 11 A method for manufacturing an aluminum alloy cast body according to claim 10, wherein the aluminum alloy cast body further comprises at least one of copper (Cu) in an amount greater than 0 wt% to 0.2 wt%, zinc (Zn) in an amount greater than 0 wt% to 0.3 wt%, iron (Fe) in an amount greater than 0 wt% to 0.5 wt%, manganese (Mn) in an amount greater than 0 wt% to 0.6 wt%, titanium (Ti) in an amount greater than 0 wt% to 0.2 wt%, and chromium (Cr) in an amount greater than 0 wt% to 0.05 wt%. Claim 12 An aluminum alloy cast body manufactured by the manufacturing method of any one of claims 1, and 4 to 11. Claim 13 delete Claim 14 delete Claim 15 In claim 12, the aluminum alloy cast body is an aluminum alloy cast body having a hardness in the range of 100 HB to 120 HB in the remelted area. Claim 16 In claim 12, the aluminum alloy cast body satisfies a yield strength (YS): 220 MPa or more, a tensile strength (UTS): 300 MPa or more, and an elongation (EL): 6% or more.

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