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

Abstract

An aluminum alloy for die casting and a method for producing an aluminum alloy cast product are disclosed. The aluminum alloy may comprise silicon (Si) in an amount of approximately 7.5 to 9.5 wt.%; magnesium (Mg) in an amount of approximately 2.5 to 3.5 wt.%; iron (Fe) in an amount of approximately 0.5 to 1.0 wt.%; manganese (Mn) in an amount of approximately 0.1 to 0.6 wt.%; and aluminum (Al) constituting the remainder of the aluminum alloy, wherein all wt.% are based on the total weight of the aluminum alloy.

Description

TECHNICAL AREA

[0001] The present invention relates to an aluminum alloy for die casting and a method for producing an aluminum alloy casting using the same. The aluminum alloy for die casting can exhibit excellent thermal conductivity and corrosion resistance. BACKGROUND OF THE INVENTION

[0002] Aluminum (Al) is generally easy to cast, well alloyed 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.

[0003] An aluminum alloy is an alloy containing aluminum (Al) as the main component and one or two or more of silicon (Si), copper (Su), magnesium (Mg), zinc (Zn), iron (Fe), manganese (Mn), nickel (Ni), and the like, which are additionally added. In addition to good plastic workability, high electrical and thermal conductivity, and an attractive appearance, the physical properties of such an aluminum alloy, such as strength, heat resistance, castability, and the like, can be improved with various types of added elements.

[0004] Such aluminum alloys can be divided into annealing alloys and casting alloys. The annealing alloy is an alloy used in an extrusion process, a rolling process, a forging process, a pressing process, and the like, and the casting alloy is an alloy used in a sand casting mold, a cellular mold, a die casting mold, and the like.

[0005] Specifically, the alloy for casting can be divided into an alloy for general casting used in sand casting and cellular molding, and an alloy for die casting used in pressure die casting. Al-Cu-based alloys, Al-Cu-Si-based alloys, Al-Si-based alloys, Al-Mg-based alloys, a heat-resistant alloy, 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.

[0006] For example, Al-Si-based alloys and Al-Mg-based alloys have been mainly used as aluminum alloys for industrial die casting. Al-Si-based alloys are widely used because of their good castability, suitability for casting molds with complex shapes, and excellent mechanical strength at room temperature. However, when Al-Si-based alloys contain a large amount of silicon (e.g., approximately 10 wt%) to maintain good castability, the thermal conductivity, which is one of the key advantages of aluminum alloys, is not high due to the addition of a large amount of silicon. It is known that Al-Si-based alloys generally have a thermal conductivity property of about 90 to 140 W / m K.

[0007] On the other hand, the Al-Mg-based alloy is an alloy with improved corrosion resistance, and although it has improved corrosion resistance and thermal conductivity compared to the Al-Si-based alloy, it has a disadvantage. For example, this alloy cannot be used to manufacture a product with a complicated shape because its castability is inferior to that of the Al-Si-based alloy.

[0008] The foregoing as the prior art is intended only to provide a better understanding of the background of the present invention and should not be construed as an affirmation that the present invention falls within the scope of the prior art already known to those skilled in the art. SUMMARY OF THE INVENTION

[0009] In preferred aspects, the present invention provides an aluminum alloy for die casting and a method for producing an aluminum alloy casting using the same. Accordingly, an aluminum alloy with thermal conductivity and corrosion resistance, as well as improved castability, is provided. Furthermore, an aluminum alloy for die casting with improved strength and elongation for increased durability is provided.

[0010] In one aspect, an aluminum alloy for die casting is provided that includes 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 0.5 to 1.0 wt.%; manganese (Mn) in an amount of about 0.1 to 0.6 wt.%; and aluminum (Al) constituting the remainder of the aluminum alloy. All wt.% are based on the total weight of the aluminum alloy.

[0011] The term "aluminum alloy" as used herein refers, for example, to a material containing aluminum as a major component, wherein the proportion of aluminum is more than about 90 wt.%, more than about 91 wt.%, more than about 92 wt.%, more than about 93 wt.%, more than about 94 wt.%, more than about 95 wt.%, more than about 96 wt.%, more than about 97 wt.%, more than about 98 wt.%, or more than about 99 wt.% based on the total weight of the aluminum alloy.

[0012] The aluminum alloy may further contain beryllium (Be) in an amount of about 0.015 wt% or less, but more than 0 wt%.

[0013] The aluminum alloy cannot contain copper (Cu), zinc (Zn) or nickel (Ni).

[0014] The aluminum alloy may suitably have a thermal conductivity of approximately 135 W / m·K or greater.

[0015] 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.

[0016] In another aspect, a method for producing an aluminum alloy cast product is provided. The method may comprise i) preparing 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 pouring the molten aluminum alloy into the aluminum alloy cast product.

[0017] The method may further comprise preheating the mold to a temperature of approximately 200 to 250°C prior to performing the injection.

[0018] The molten aluminum alloy may contain silicon (Si) in an amount of approximately 7.5 to 9.5 wt.%; magnesium (Mg) in an amount of approximately 2.5 to 3.5 wt.%; iron (Fe) in an amount of approximately 0.5 to 1.0 wt.%; manganese (Mn) in an amount of approximately 0.1 to 0.6 wt.%; and aluminum (Al), which forms the remainder of the molten aluminum alloy. All wt.% are based on the total weight of the molten aluminum alloy.

[0019] The molten aluminum alloy may further contain beryllium (Be) in an amount of about 0.015 wt% or less, but more than 0 wt%.

[0020] The molten aluminum alloy cannot contain copper (Cu), zinc (Zn) or nickel (Ni).

[0021] The aluminum alloy product may have a thermal conductivity of approximately 135 W / m·K or more.

[0022] The aluminum alloy casting product may suitably have a yield strength of 260 MPa or more. The aluminum alloy product may suitably have a tensile strength of 320 MPa or more. The aluminum alloy product may suitably have an elongation of 3% or more.

[0023] Further, a vehicle is provided comprising the aluminum alloy as described herein.

[0024] Further provided is a die-cast product comprising the aluminum alloy as described herein. Character list

[0025] The above and other objects, features and advantages of the present invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings in which: Fig.1 shows a comparison of the results over time after spraying salt water (5% NaCl) on samples in Comparative Examples and Example 3 according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0026] The 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 is further understood that the terms "comprising," "including," "having," etc., when used in this specification, specify the presence of stated features, ranges, integers, steps, acts, elements, and / or components, but do not preclude the presence or addition of one or more other features, ranges, integers, steps, acts, elements, components, and / or combinations thereof.

[0027] It is understood that the term "vehicle" or "vehicular" or other similar terms, as used herein, generally encompasses motor vehicles, such as passenger cars, including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft, including a variety of boats and ships, aircraft, and the like, as well as 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 noted herein, a hybrid vehicle is a vehicle that has two or more power sources, for example, both gasoline-powered and electric-powered vehicles.

[0028] Furthermore, unless specifically stated or obvious from the context, the term "about" as used herein is to be understood as within a range of normal tolerance in the art, for example, within 2 standard deviations of the mean. "Approximately" may be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise apparent from the context, all numerical values ​​provided herein are modified by the term "about."

[0029] 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 can be implemented in a variety of forms. These embodiments are provided merely to complete the invention of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0030] An aluminum alloy for die casting may contain silicon (Si) in an amount of approximately 7.5 to 9.5 wt.%; magnesium (Mg) in an amount of approximately 2.5 to 3.5 wt.%; iron (Fe) in an amount of approximately 0.5 to 1.0 wt.%; manganese (Mn) in an amount of approximately 0.1 to 0.6 wt.%; and aluminum (Al), which forms the balance of the aluminum alloy. All wt.% are based on the total weight of the aluminum alloy. In addition, the aluminum alloy may further contain beryllium (Be) in an amount of approximately 0.015 wt.% or less, but more than 0 wt.%.

[0031] The reason for limiting 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 approximately 7.5 to 9.5 wt%:

[0032] Silicon (Si), as used herein, can improve castability and abrasion resistance, and affect thermal conductivity and strength. If the silicon content is less than about 7.5 wt%, the effect of improving castability, abrasion resistance, and strength may be insignificant. If silicon is added in an amount greater than about 9.5 wt%, properties related to casting processability, such as machinability, may be reduced, and the aluminum alloy may be weakened by heat treatment. For this reason, the silicon content may range from about 7.5 to 9.5 wt%. Magnesium (Mg) in an amount of approximately 2.5 to 3.5 wt%:

[0033] Magnesium (Mg), as used herein, may be a Mg 2Form a Si compound, which, together with silicon (Si), acts as a dispersion strengthening material to improve strength. Furthermore, Mg can improve corrosion resistance and elongation, thereby improving the machinability of the casting.

[0034] At this time, if the magnesium (Mg) content is less than about 2.5 wt%, the improving effect on corrosion resistance, elongation, and strength is negligible. If the magnesium content is more than about 3.5 wt%, the fluidity of the melt may be reduced during casting, and the oxidation tendency of the melt may also be increased, leading to increased dross. For this reason, the magnesium content can be in the range of about 2.5 to 3.5 wt%. Iron (Fe) in an amount of approximately 0.5 to 1.0 wt%:

[0035] Iron (Fe), as used herein, can contribute to solid solution strengthening and dispersion strengthening. When the iron content is less than about 0.5 wt%, the effect of improving strength may be insignificant, and when the iron content is more than about 1.0 wt%, there is a disadvantage that thermal conductivity and castability deteriorate. For this reason, the iron (Fe) content can be in the range of about 0.5 to 1.0 wt%. Manganese (Mn) in an amount of approximately 0.1 to 0.6 wt%:

[0036] Manganese (Mn), as used herein, together with iron (Fe), can contribute to the formation of a solid solution and improve the strength of the casting. However, as the manganese content is increased, castability and machinability may be reduced, and thermal conductivity may be decreased. For this reason, the manganese content can be in the range of approximately 0.1 to 0.6 wt%. Beryllium (Be) in an amount of approximately 0.015 wt% or less, but more than 0 wt%:

[0037] Beryllium (Be), as used herein, can prevent the oxidation of magnesium (Mg) to suppress the formation of dross during a casting process and improve corrosion resistance. However, if beryllium is added in an amount greater than about 0.015 wt%, the corrosion resistance of the aluminum alloy may deteriorate, and thus the beryllium content may be less than about 0.015 wt%. The beryllium (Be) content may suitably be in the range of about 0.002 to 0.015 wt%.

[0038] Preferably, the aluminum alloy does not contain copper (Cu), zinc (Zn), or nickel (Ni), as these can lead to corrosion of the aluminum alloy. Accordingly, the corrosion resistance of the casting to be produced can be increased to minimize the occurrence of corrosion.

[0039] A method for producing an aluminum alloy cast product may include a manufacturing process for producing a molten aluminum alloy having the composition described above, a casting process for injecting the produced molten aluminum alloy into a mold, and a casting process for pouring the molten aluminum alloy into the aluminum alloy cast product.

[0040] At this time, the method may further include a preheating process of preheating a mold to a temperature of approximately 200 to 250°C prior to the casting process.

[0041] For example, the mold may be preheated to a sufficiently high temperature of approximately 200 to 250°C to avoid the occurrence of cracks and casting defects when pouring the molten aluminum alloy prepared as described above to produce the aluminum alloy casting.

[0042] Meanwhile, if the mold is preheated to a temperature lower than about 200°C, the preheating effect of the mold may not be insignificant, and further filling ability in the mold may also be reduced due to deterioration of the fluidity of the molten aluminum alloy, thereby causing casting defects. Furthermore, if the mold is preheated to a temperature higher than about 250°C, preheating costs may increase, crystal grain coarsening of the aluminum alloy casting to be produced later may be caused, or a crack may be induced during a cooling process. For this reason, the preheating temperature for the mold may be within an approximate range. Preferably, in the casting step, the aluminum alloy produced as described above may be poured into the preheated mold under a pressure of about 75 MPa. EXAMPLE

[0043] In the following, embodiments of the present invention will be described in detail. However, the following examples are merely exemplary of the present invention, and the present invention is not limited to the following examples.

[0044] The composition of various examples of the present invention and comparative examples are shown in Table 1 below. Table 1 Classification Al Si Mg Fe Mn Be Cu Zn No Sn Pb Ti Example 1 rest 7,5 2,5 0,5 0,1 - - - - - - - Example 2 rest 8,0 3,5 0,7 0,3 - - - - - - - Example 3 rest 8,0 3,0 0,7 0,3 0,005 - - - - - - Comparative example 1 (ALDC5) rest 0,2 6,0 0,8 0,1 - 0,1 0,05 0,05 0,05 0,05 0,1 Comparative example 2 (ALDC12) rest 12 0,2 0,8 0,1 - 3,0 0,7 0,3 0,1 0,1 0,1 Comparison example 3 rest 5,32 2,73 0,49 0,14 - - - - - - - Comparison example 4 rest 5,42 2,81 0,51 0,14 - - - - - - - Comparison example 5 rest 12,45 2,84 0,50 0,14 - - - - - - - Comparison example 6 rest 12,43 2,85 0,52 0,14 - - - - - - - Comparison example 7 rest 8,32 1,73 0,49 0,14 - - - - - - - Comparative example 8 rest 8,42 1,71 0,51 0,14 - - - - - - - Comparison example 9 rest 8,45 4,54 0,50 0,14 - - - - - - - Comparison example 10 rest 8,43 4,55 0,52 0,14 - - - - - - -

[0045] 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.

[0046] 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 radius of curvature (R) of 6.0 mm; a longitudinal length (L) of 100 mm or more; a parallel portion length (A) of 32 mm; and a grip portion width (C) of 10 mm) for the examples and comparative examples in Table 1 were prepared, and a tensile test (KS B 0802) was conducted for the above-mentioned test specimens. A test specimen with the dimension of 10 mm x 10 mm x 2 t was prepared, and a thermal conductivity test (ASTM E 1461) was conducted 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 Classification Thermal conductivity (W / m·K) Tensile strength (MPa) Yield strength (MPa) Elongation (%) Example 1 150 320 260 4,0 Example 2 135 350 285 3,0 Example 3 140 330 280 3,0 Comparison example 1 96 280 180 2,0 Comparison example 2 96 300 150 3,0 Comparison example 3 148 321 198 6,5 Comparison 135 325 197 6,8 example 4 Comparison example 5 102 317 254 5,3 Comparison example 6 103 345 251 3,0

[0047] As shown in Tables 1 and 2, according to the examples of the present invention, the aluminum alloy for die casting can be manufactured to have excellent physical properties including a thermal conductivity of 135 W / m K or more, a yield strength of 260 MPa or more, a tensile strength of 320 MPa or more, and an elongation of 3% or more.

[0048] In particular, compared with conventional aluminum alloys for die casting, it can be seen that the aluminum alloys of the present invention not only improved thermal conductivity by more than 40%, but also improved tensile strength by more than 6%, improved yield strength by more than 44%, and secured elongation to the same extent or more. Accordingly, a cast product with excellent durability can be produced compared with conventional casting.

[0049] In particular, as shown in Examples 1 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 in causing a reduction in yield strength, and when the silicon (Si) content was more than 9.5 wt%, the thermal conductivity rapidly decreased due to the increase in alloying elements. For this reason, it is preferable to limit the silicon content to the range of approximately 7.5 wt% to 9.5 wt%.

[0050] Accordingly, when vehicle electric parts are manufactured using the aluminum alloy according to the embodiment of the present invention, since, compared with a conventional aluminum alloy, the aluminum alloy of the present invention can have excellent thermal conductivity and can improve heat dissipation performance, the present invention can offer the advantage that the performance and durability of the product can be improved.

[0051] In Fig. 1 is a photograph showing Comparative Examples and an Example after 24 hours, after 48 hours, and after 72 hours after salt water (5% NaCl) was sprayed onto Comparative Example 2 and 7 to 10 and Example 3 according to the exemplary embodiments of the present invention.

[0052] At this time, a salt water spray test (KS D 9502) was performed using salt water containing 5% NaCl after the preparation of ASTM SUBSIZE test specimens.

[0053] Out of Fig. 1, it can be seen that although the corrosion of Comparative Example 2 (ALDC12), which is one of the commercially available Al-Si-based alloys, had significantly progressed 24 hours after the spraying of salt water, Example 3 of the present invention was maintained in an initial state in which corrosion hardly occurred even after the lapse of 48 hours.

[0054] 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 significantly, causing significant corrosion, and when the content of magnesium (Mg) was more than 3.5 wt%, the corrosion resistance deteriorated again, causing corrosion.

[0055] Therefore, when vehicle electrical parts that remain under the external environment such as high temperature and high humidity condition, seawater, rainwater and the like are manufactured using the aluminum alloy according to various exemplary embodiments of the present invention, the life and durability of manufactured vehicle electrical parts can be increased, and the manufacturing cost can be reduced because no separate rust prevention treatment is required.

[0056] According to various embodiments of the present invention, a variety of castings required for excellent thermal conductivity and corrosion resistance can be manufactured by improving the thermal conductivity and corrosion resistance compared to a conventional aluminum alloy for die casting while ensuring castability.

[0057] Furthermore, 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 with excellent durability can be produced.

[0058] Although the present invention has been described with reference to the accompanying drawings and the preferred embodiments described above, the present invention is not limited thereto, but is defined by the following claims. Accordingly, those skilled in the art may modify and alter the present invention without departing from the technical spirit of the following claims.

Claims

[1] Aluminium alloy for a die-cast part, comprising Silicon (Si) in an amount of approximately 7.5 to 9.5 wt%; Magnesium (Mg) in an amount of approximately 2.5 to 3.5 wt%; Iron (Fe) in an amount of approximately 0.5 to 1.0 wt%; Manganese (Mn) in an amount of 0.1 to 0.6 wt%; and Aluminium (Al), which forms the rest of the aluminium alloy, where all weight percentages refer to the total weight of the aluminum alloy. [2] The aluminum alloy of claim 1, further comprising beryllium (Be) in an amount of about 0.015 wt% or less but more than 0 wt%. [3] The aluminum alloy of claim 1, wherein the aluminum alloy does not comprise copper (Cu), zinc (Zn) or nickel (Ni). [4] The aluminum alloy of claim 2, wherein the aluminum alloy does not comprise copper (Cu), zinc (Zn) or nickel (Ni). [5] The aluminum alloy of claim 1, wherein the aluminum alloy has a thermal conductivity of about 135 W / m·K or above. [6] The aluminum alloy of claim 1, wherein the aluminum alloy has a yield strength of about 260 MPa or above. [7] The aluminum alloy of claim 1, wherein the aluminum alloy has a tensile strength of about 320 MPa or above. [8] The aluminum alloy according to claim 1, wherein the aluminum alloy has an elongation of 3% or more. [9] 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 Pouring the molten aluminum alloy into the aluminum alloy casting product. [10] The method of claim 9, further comprising preheating the mold to a temperature of about 200 to 250°C prior to injecting. [11] The method of claim 9, wherein the molten aluminum alloy comprises 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 0.5 to 1.0 wt%; manganese (Mn) in an amount of about 0.1 to 0.6 wt%; and aluminum (Al) forming the remainder of the molten alloy, all wt% being based on the total weight of the molten aluminum alloy. [12] The method of claim 11, wherein the molten aluminum alloy further comprises beryllium (Be) in an amount of about 0.015 wt% or less, but more than 0 wt%. [13] The method of claim 11, wherein the molten aluminum alloy does not comprise copper (Cu), zinc (Zn) or nickel (Ni). [14] The method of claim 12, wherein the molten aluminum alloy does not comprise copper (Cu), zinc (Zn) or nickel (Ni). [15] The method of claim 11, wherein the aluminum alloy cast product has a thermal conductivity of about 135 W / m·K or above. [16] The method of claim 11, wherein the aluminum alloy casting product has a yield strength of about 260 MPa or above. [17] The method according to claim 11, wherein the aluminum alloy cast product has a tensile strength of 320 MPa or above. [18] The method according to claim 11, wherein the aluminum alloy cast product has an elongation of 3% or more. [19] A vehicle comprising an aluminum alloy according to claim 1. [20] A die-cast product comprising an aluminum alloy according to claim 1.