ALUMINUM ALLOY FOR DIE CASTING AND METHOD FOR PRODUCING ALUMINUM ALLOY CASTINGS USING THE SAME

Abstract

An aluminum alloy for a die-cast part, comprising silicon (Si) in an amount of 7.5 to 9.5 wt.%; magnesium (Mg) in an amount of 2.5 to 3.5 wt.%; iron (Fe) in an amount of more than 0.65 to 1.0 wt.%; manganese (Mn) in an amount of 0.1 to 0.6 wt.%; and aluminum (Al) forming the remainder of the aluminum alloy, all wt.% being based on the total weight of the aluminum alloy.

Description

TECHNICAL FIELDThe present invention relates to an aluminum alloy for die casting and a method for manufacturing an aluminum alloy casting using the same. The aluminum alloy for die casting may have excellent thermal conductivity and corrosion resistance.BACKGROUND OF THE INVENTIONAluminum (Al) is usually easy to cast, alloyed well with other metals, has excellent corrosion resistance in the atmosphere, and has excellent electrical and thermal conductivity, and thus aluminum is widely used in industry.An aluminum alloy is an alloy containing aluminum (Al) as a main component and one or two or more of silicon (Si), copper (Cu), magnesium (Mg), zinc (Zn), iron (Fe), manganese (Mn), nickel (Ni), and the like, which are additionally added. Besides good plastic workability, high electric and thermal conductivity and pleasing appearance, the physical properties of such an aluminum alloy, such as strength, heat resistance, castability and the like, can be improved with various kinds of added elements.Such aluminum alloys can be divided into alloys for annealing and alloys for casting. The alloy for annealing is an alloy used in an extrusion method, a rolling method, a forging method, a pressing method, and the like, and the alloy for casting is an alloy used for a sand casting mold, a cell mold, a die casting mold, and the like.Specifically, the alloy for casting may be divided into an alloy for general casting used in a sand casting mold and a cell mold and an alloy for die casting used in a die casting mold. Al-Cu based alloys, Al-Cu-Si based alloys, Al-Si based alloys, Al-Mg based alloys, a heat resistant alloy and a bearing alloy and the like are used as the alloy for general casting, and Al-Si based alloys, Al-Si-Mg based alloys, Al-Mg based alloys and Al-Si-Cu based alloys are used as the alloy for die casting.For example, the Al-Si-based alloy and the Al-Mg-based alloy have been mainly used as aluminum alloy that is industrially applied to die casting. The Al-Si based alloys are used for many purposes because they are excellent in castability, are suitable for a mold having a complicated shape, and have excellent mechanical strength at room temperature. However, when the Al-Si based alloy contains silicon in a large amount (e.g., about 10 wt %) to maintain good castability, thermal conductivity, which is one of the essential advantages of the aluminum alloy, is not high due to addition of the large amount of silicon. It is known that the Al-Si-based alloy generally has a thermal conductivity property of about 90 to 140 W / m·K.On the other hand, the Al-Mg-based alloy is an alloy having improved corrosion resistance and has a drawback in that it has improved corrosion resistance and thermal conductivity as compared with the Al-Si-based alloy. For example, this alloy cannot be used for producing a product having a complicated shape because its castability is inferior to that of the Al-Si-based alloy.US 2012 / 0 148 444 A1 and JP 2017-71 840 A disclose cast aluminum alloys and methods for their production. EP 0 933 441 A1 describes a method for producing a component made of an aluminum alloy by die casting.The above as the related art is merely intended to better understand the background of the present invention and should not be understood as a confirmation that the present invention falls within the scope of the related art already known to those skilled in the art.SUMMARY OF THE INVENTIONThe present invention provides an aluminum alloy for die casting and a method for manufacturing an aluminum alloy casting using the same. Accordingly, an aluminum alloy having thermal conductivity and corrosion resistance and improved castability is provided. Further, an aluminum alloy for die casting having improved strength and elongation for enhancing durability is provided.In one aspect, there is provided an aluminum alloy for die casting, including silicon (Si) in an amount of about 7.5 to 9.5 wt %; magnesium (Mg) in an amount of about 2.5 to 3.5 wt %; iron (Fe) in an amount of about more than 0.65 to 1.0 wt %; manganese (Mn) in an amount of about 0.1 to 0.6 wt %; and aluminum (Al) constituting the remaining balance of the aluminum alloy. All % by weight data relate to the total weight of the aluminum alloy.The aluminum alloy may further contain beryllium (Be) in an amount of about 0.015 wt % or less but more than 0 wt %.The aluminum alloy may not contain copper (Cu), zinc (Zn), or nickel (Ni).The aluminum alloy may suitably have a thermal conductivity of about 135 W / m·K or greater.The aluminum alloy may suitably have a yield strength of about 260 MPa or above. The aluminum alloy may suitably have a tensile strength of 320 MPa or above. The aluminum alloy may suitably have an elongation of 3% or above.In another aspect, a method of making an aluminum alloy casting product is provided. The method includes preparing a molten aluminum alloy including silicon (Si), magnesium (Mg), iron (Fe), manganese (Mn), and aluminum (Al); injecting the molten aluminum alloy into a mold; and casting the molten aluminum alloy into the aluminum alloy casting product.The method may further include preheating the mold to a temperature of about 200 to 250° C. prior to performing the injecting.The molten aluminum alloy contains silicon (Si) in an amount of about 7.5 to 9.5 wt %; magnesium (Mg) in an amount of 2.5 to 3.5 wt %; iron (Fe) in an amount of about more than 0.65 to 1.0 wt %; manganese (Mn) in an amount of about 0.1 to 0.6 wt %; and aluminum (Al) constituting the rest of the molten aluminum alloy. All % by weight data are based on the total weight of the molten aluminum alloy.The molten aluminum alloy may further contain beryllium (Be) in an amount of about 0.015 wt % or less but more than 0 wt %.The molten aluminum alloy may not contain copper (Cu), zinc (Zn), or nickel (Ni).The aluminum alloy product may have a thermal conductivity of about 135 W / m·K or more.The aluminum alloy casting product may suitably have a yield strength of 260 MPa or above. The aluminum alloy product may suitably have a tensile strength of 320 MPa or above. The aluminium alloy product may suitably have an elongation of 3% or above.Further provided is a vehicle comprising the aluminum alloy as described herein.Further provided is a die cast product comprising the aluminum alloy as described herein.BRIEF DESCRIPTION OF THE DRAWINGSThe above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: FIG. 1 shows a comparison of the results over time after salt water (5% NaCl) is sprayed on samples in Comparative Examples and Example 3 according to an exemplary embodiment of the present invention.DETAILED DESCRIPTIONThe terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprise," "include," "have," etc., when used in this specification, specify the presence of stated features, ranges, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, ranges, integers, steps, operations, elements, components, and / or combinations thereof.It should be understood that the term "vehicle" or "vehicular" or other similar term as used herein generally includes motor vehicles such as passenger cars including sports utility vehicles (SUVs), buses, trucks, various utility vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel motor vehicles (e.g. fuels derived from resources other than petroleum). As mentioned herein, a hybrid vehicle is a vehicle having two or more sources of power, for example both gasoline-powered and electric-powered vehicles.Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below, but is implemented in various forms. The embodiments are intended merely to complete the invention of the present invention and fully convey the scope of the invention to those skilled in the art.The aluminum alloy for die casting contains silicon (Si) in an amount of about 7.5 to 9.5 wt %; magnesium (Mg) in an amount of about 2.5 to 3.5 wt %; iron (Fe) in an amount of about more than 0.65 to 1.0 wt %; manganese (Mn) in an amount of about 0.1 to 0.6 wt %; and aluminum (Al) constituting the rest of the aluminum alloy. All % by weight data relate to the total weight of the aluminum alloy. In addition, the aluminum alloy may further contain beryllium (Be) in an amount of about 0.015 wt % or less but more than 0 wt %.The reason for restricting the composition of the alloy in the aluminum alloy for die casting according to exemplary embodiments of the present invention will be described in detail.Silicon (Si) in an amount of about 7.5 to 9.5 wt%:Silicon (Si) as used herein may improve castability and abrasion resistance and affect thermal conductivity and strength. When the content of silicon is less than about 7.5 wt %, the effect of improving castability, abrasion resistance and strength may be insignificant, and when silicon is added in an amount of more than about 9.5 wt %, properties for cast workability, for example, workability, may be reduced and the aluminum alloy may be weakened by heat treatment. For this reason, the content of silicon is in the range of about 7.5 to 9.5 wt %.Magnesium (Mg) in an amount of about 2.5 to 3.5 wt%:Magnesium (Mg) as used herein may form a Mg 2 Si compound serving as a dispersion strengthening material together with silicon (Si) to improve strength. Further, Mg can improve corrosion resistance and elongation, thereby improving workability of casting.At this time, when the content of magnesium (Mg) is less than about 2.5 wt %, an improving effect of corrosion resistance, elongation and strength is insignificant, and when the content of magnesium is more than about 3.5 wt %, the melt fluidity during casting may be reduced, the tendency of the melt to oxidize may also be increased to increase the crumb. For this reason, the content of magnesium is in the range of about 2.5 to 3.5 wt%.Iron (Fe) in an amount of about 0.5 to 1.0 wt%:Iron (Fe) as used herein may help form solid solution strengthening and dispersion strengthening. If the content of iron is less than about 0.5 wt %, the effect of improving the strength may be insignificant, and if the content of iron is more than about 1.0 wt %, there occurs a disadvantage that the thermal conductivity and the castability are deteriorated. For this reason, the content of iron (Fe) may be in the range of about 0.5 to 1.0 wt %. According to the invention, the content of iron is in the range of more than 0.65 to 1.0 wt%.Manganese (Mn) in an amount of about 0.1 to 0.6 wt%:Manganese (Mn) as used herein may contribute to solid solution formation and improvement in casting strength together with iron (Fe). However, since the content of manganese is increased, castability and workability can be reduced and thermal conductivity can be reduced. For this reason, the content of manganese is in the range of about 0.1 to 0.6 wt%.Beryllium (Be) in an amount of about 0.015 wt% or less but more than 0 wt%:Beryllium (Be) as used herein can prevent the oxidation of magnesium (Mg) to suppress the formation of crumb during a casting process and improve corrosion resistance. However, when beryllium is added in an amount of more than about 0.015 wt %, the corrosion resistance of the aluminum alloy may deteriorate, and thus the content of beryllium may be less than about 0.015 wt %. The content of beryllium (Be) may suitably be in the range of about 0.002 to 0.015% by weight.Preferably, the aluminum alloy may not contain copper (Cu), zinc (Zn) or nickel (Ni), since these may lead to corrosion of the aluminum alloy. Accordingly, the corrosion resistance of the casting to be produced can be increased in order to minimize occurrence of corrosion.The method for manufacturing an aluminum alloy cast product includes a manufacturing process for manufacturing a molten aluminum alloy having the composition described above, a casting process for injecting the manufactured molten aluminum alloy into a mold, and a casting process for casting the molten aluminum alloy into the aluminum alloy cast product.At this time, the method may further include a pre-heating process of pre-heating a mold to a temperature of about 200 to 250° C. prior to the casting process.For example, the mold may be preheated to a sufficiently high temperature of about 200 to 250° C. to prevent the occurrence of cracks and casting defects when the molten aluminum alloy produced as described above is cast to produce the aluminum alloy casting.At this time, when the mold is preheated to a temperature of less than about 200° C., a preheating effect of the mold may not be insignificant, and further, the further filling ability in the mold may also be reduced due to the deterioration of the fluidity of the molten aluminum alloy, thereby causing casting defects. Further, when the mold is preheated to a temperature higher than about 250° C., the preheating cost may increase, crystal grain coarsener of the aluminum alloy casting to be produced later may be caused, or a crack may be caused during a cooling process. For this reason, the preheating temperature for the mold may be in an approximate range. Preferably, in the casting step, the aluminum alloy prepared as described above may be cast into the preheated mold under a pressure of about 75 MPa.EXAMPLEHereinafter, embodiments of the present invention will be described in detail. However, the following examples are merely examples of the present invention, and the present invention is not limited to the following examples.The compositions of various examples of the present invention and comparative examples are shown in Table 1 below. At this time, Comparative Examples 1 and 2 were conventional aluminum alloys for die casting, Comparative Example 1 was ALDC5 which is one of Al-Mg-based alloys, and Comparative Example 2 was ALDC12 which is one of commercially available Al-Si-based alloys.ASTM SUBSIZE test specimens (a gauge length (G) of 25 mm; a width of 6.25 mm; a thickness (T) of 3.05 mm; a rounding radius (R) of 6.0 mm; a longitudinal length (L) of 100 mm or above; a length of the parallel section (A) of 32 mm; A width of the grip portion (C) of 10 mm) for the examples and comparative examples in Table 1 was prepared, and a tensile test (KS B 0802) for the above-mentioned test specimens was performed, and a test specimen having the dimension of 10 mm x 10 mm x 2 t was prepared, and a thermal conductivity measurement test (ASTM E 1461) was performed for the test specimen to measure the physical properties for each of the examples and comparative examples. The measured values of the physical properties are shown in Table 2 below. Table 2 Table 2Reference Example 11503202604,0Example 21353502853,0Example 31403302803,0Comparative Example 1962801802,0Comparative Example 2963001503,0Comparative Example 31483211986,5Comparative Example 41353251976,8Comparative Example 51023172545,3Comparative Example 61033452513,0As shown in Tables 1 and 2, according to the examples of the present invention, the aluminum alloy for die casting can be produced to have excellent physical properties including a thermal conductivity of 135 W / m·K or above, a yield strength of 260 MPa or above, a tensile strength of 320 MPa or above, and an elongation of 3% or above.Particularly, as compared with the conventional aluminum alloys for die casting, it can be found that in the aluminum alloys of the present invention, not only the thermal conductivity was improved by more than 40 % but also the tensile strength was improved by more than 6 %, the yield strength was improved by more than 44 %, and the elongation was secured to the same extent or more. Accordingly, compared with a conventional casting, a cast product having excellent durability can be produced.In particular, as shown in Reference Example 1, Examples 2 to 3 of the present invention, and Comparative Examples 3 to 6, when the content of silicon (Si) in the present invention was less than 7.5 wt %, the formation of the Mg 2 Si compound was insignificant to cause a decrease in yield strength, and when the content of silicon (Si) was more than 9.5 wt %, the thermal conductivity rapidly reduced due to the increase in alloying elements. For this reason, it is preferable to limit the content of silicon to the range of about 7.5 wt % to 9.5 wt %.Accordingly, when vehicle electrical parts are manufactured using the aluminum alloy according to the embodiment of the present invention, since the aluminum alloy of the present invention is excellent in thermal conductivity and can improve heat dissipation performance as compared with a conventional aluminum alloy, the present invention can provide an advantage that the performance and durability of the product can be improved.In FIG. 1, a photograph showing comparative examples and an example after 24 hours, after 48 hours, and after 72 hours after salt water (5% NaCl) is sprayed on comparative examples 2 and 7 to 10 and example 3 according to the exemplary embodiments of the present invention is shown.At this time, a salt water spray test (KS D 9502) using salt water of 5% NaCl was performed after the preparation of ASTM SUBSIZE specimens.It can be seen from FIG. 1 that although corrosion on Comparative Example 2 (ALDC12) which is one of commercially available Al-Si-based alloys has significantly advanced 24 hours after salt water was sprayed on, Example 3 of the present invention was maintained in an initial state in which corrosion hardly occurs even after 48 hours elapsed.In particular, as shown in Comparative Examples 7 to 10, when the content of magnesium (Mg) was less than 2.5 wt %, the corrosion resistance deteriorated remarkably, causing significant corrosion, and when the content of magnesium (Mg) was more than 3.5 wt %, the corrosion resistance deteriorated again, causing corrosion.Therefore, when electric vehicle parts remaining under the external environment such as high temperature and high humidity state, seawater, rainwater, and the like are manufactured using the aluminum alloy according to various exemplary embodiments of the present invention, the durability and durability of manufactured electric parts of a vehicle may increase, and the manufacturing cost may decrease because separate rust prevention treatment is not required.According to various embodiments of the present invention, a plurality of castings required for excellent thermal conductivity and corrosion resistance may be produced by improving thermal conductivity and corrosion resistance compared to a conventional aluminum alloy for die casting while securing castability.In addition, as compared with a conventional aluminum alloy for die casting, the aluminum alloy according to the present invention can have excellent strength and elongation, and thus a cast product having excellent durability can be produced.Although the present invention has been described with reference to the accompanying drawings and the above-described preferred embodiments, the present invention is not limited thereto, but is limited by the following claims. Accordingly, those skilled in the art can modify and modify the present invention without departing from the technical spirit of the following claims.

Claims

An aluminum alloy for a die casting, comprising silicon (Si) in an amount of 7.5 to 9.5 wt%; magnesium (Mg) in an amount of 2.5 to 3.5 wt%; iron (Fe) in an amount of more than 0.65 to 1.0 wt%; manganese (Mn) in an amount of 0.1 to 0.6 wt%; and aluminum (Al) constituting the balance of the aluminum alloy, wherein all wt% data are based on the total weight of the aluminum alloy.The aluminum alloy according to claim 1, further comprising beryllium (Be) in an amount of 0.015 wt% or less but more than 0 wt%.The aluminum alloy according to claim 1 or 2, wherein the aluminum alloy does not comprise copper (Cu), zinc (Zn) or nickel (Ni).The aluminum alloy according to claim 1, wherein the aluminum alloy has a thermal conductivity of 135 W / m·K or above.The aluminum alloy of claim 1, wherein the aluminum alloy has a yield strength of 260 MPa or above.The aluminum alloy of claim 1, wherein the aluminum alloy has a tensile strength of 320 MPa or above.The aluminum alloy of claim 1, wherein the aluminum alloy has an elongation of 3% or above.A method for producing an aluminum alloy casting product, comprising: producing a molten aluminum alloy comprising silicon (Si), magnesium (Mg), iron (Fe), manganese (Mn), and aluminum (Al); injecting the molten aluminum alloy into a mold; and casting the molten aluminum alloy into the aluminum alloy casting product, wherein the molten aluminum alloy comprises silicon (Si) in an amount of 7.5 to 9.5 wt%; magnesium (Mg) in an amount of 2.5 to 3.5 wt%; iron (Fe) in an amount of more than 0.65 to 1.0 wt%; manganese (Mn) in an amount of 0.1 to 0.6 wt%; and aluminum (Al) constituting the remainder of the molten alloy, wherein all the % by weight are based on the total weight of the molten aluminum alloy.The method of claim 8, further comprising preheating the mold to a temperature of 200 to 250°C prior to injecting.The method according to claim 8, wherein the molten aluminum alloy further comprises beryllium (Be) in an amount of 0.015 wt% or less but more than 0 wt%.The method according to any one of claims 8 to 10, wherein the molten aluminum alloy does not comprise copper (Cu), zinc (Zn) or nickel (Ni).The method of claim 8, wherein the aluminum alloy casting product has a thermal conductivity of 135 W / m·K or above.The method of claim 8, wherein the aluminum alloy casting product has a yield strength of 260 MPa or above.The method of claim 8, wherein the aluminum alloy casting product has a tensile strength of 320 MPa or greater.The method of claim 8, wherein the aluminum alloy casting product has an elongation of 3% or greater.A vehicle comprising an aluminium alloy according to claim 1.A die cast product comprising an aluminium alloy according to claim 1.

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