Aluminum alloys and aluminum alloy die castings

Abstract

This invention provides an aluminum alloy for die casting that can reduce the copper content while ensuring the creep properties required for parts subjected to thermal loads, and a die casting made from this aluminum alloy. [Solution] An aluminum alloy comprising silicon, copper, and magnesium, with the remainder being aluminum and impurities, wherein the silicon content is greater than 9.5% by weight and 12.5% ​​by weight or less, the copper content is greater than 0.6% by weight and 1.8% by weight or less, and the magnesium content is 0.4% by weight or more and 0.5% by weight or less.

Description

Technical Field

[0001] The present invention relates to a die-casting aluminum alloy excellent in recyclability and creep properties, and an aluminum alloy die-cast article made of the alloy.

Background Art

[0002] Aluminum alloys are widely used in the automobile industry, home appliance industry, and aerospace field due to their excellent recyclability, specific strength, and mass productivity.

[0003] As aluminum alloy die-casting materials, ADC12 specified in JIS H 5302 is widely used. Since ADC12 contains large amounts of 9.6 wt% to 12.0 wt% of silicon (Si) and 1.5 wt% to 3.5 wt% of copper (Cu), the contained Si provides excellent castability, and the contained Cu provides excellent tensile properties and creep properties, so it is also widely used in parts subjected to thermal loads such as crankcases and cylinders.

Summary of Invention

Problems to be Solved by the Invention

[0004] As shown in an example in Table 1, when producing the ADC12 material AD12.1 (JIS H 2118), since a plurality of aluminum alloy scrap raw materials are mixed, the Cu content is insufficient relative to the material standard, so an additional Cu scrap raw material is added. In addition, since magnesium (Mg) exceeds the standard 0.3 wt%, a Mg removal treatment is performed to intentionally lower the Mg content. This Cu is a depletable resource, and from the viewpoint of Cu recycling, reduction in the usage amount of Cu scrap raw material is desired, but securing high-temperature creep properties is a problem. In addition, since the Mg removal separates Mg in the molten aluminum alloy as Mg chloride using chlorine gas or a chlorine-based flux, dioxins may be generated in the exhaust gas.

[0005] [Table 1]

[0006] This application aims to solve the above-mentioned problems by providing an aluminum alloy for die casting and a die casting made from this aluminum alloy that can secure the creep characteristics required for parts subjected to thermal loads while reducing the Cu content. Furthermore, it contributes to preventing environmental pollution by reducing the amount of Mg removed. [Means for solving the problem]

[0007] [1] An aluminum alloy containing Si, Cu, and Mg, with the remainder being aluminum and impurities. The Si content is greater than 9.5% by weight and less than or equal to 12.5% ​​by weight. The Cu content is greater than 0.6% by weight and less than or equal to 1.8% by weight. An aluminum alloy having a Mg content of 0.4% by weight or more and 0.5% by weight or less.

[0008] According to the above embodiment, while reducing the Cu content, it exhibits superior creep characteristics compared to ADC12, and its tensile properties are equivalent to those of ADC12. Furthermore, since the Cu and Mg content is obtained from a single or multiple aluminum scrap raw materials, the Cu addition / demagnetization process is unnecessary.

[0009] [2] The impurities may include one or more selected from zinc (Zn), iron (Fe), manganese (Mn), nickel (Ni), titanium (Ti), lead (Pb), and tin (Sn). The Zn content is 2.5% by weight or less. The Fe content is 1.3% by weight or less. The Mn content is 0.5% by weight or less. The Ni content is 0.5% by weight or less. The Ti content is 0.3% by weight or less. The Pb content is 0.2% by weight or less. The aluminum alloy according to [1], wherein the Sn content is 0.2% by weight or less.

[0010] According to the above embodiment, an aluminum alloy is obtained that has equivalent tensile properties (0.2% yield strength and tensile strength) to ADC12 and superior creep properties to ADC12.

[0011] Aluminum alloy die-cast, made from the aluminum alloy described in [3][1] or [2].

[0012] According to the above embodiment, while reducing the Cu content, the resulting aluminum alloy die-cast has superior creep characteristics compared to a die-cast made of ADC12, and tensile properties equivalent to those of a die-cast made of ADC12. [Effects of the Invention]

[0013] According to the present invention, as shown in Table 2 for formulation examples, production can be carried out using the same scrap raw materials as in the production of AD12.1 without the need to adjust Cu and Mg.

[0014] [Table 2] [Modes for carrying out the invention]

[0015] The following describes an aluminum alloy according to one embodiment of the present invention, and an aluminum alloy die-cast using the same alloy.

[0016] [Aluminum alloy] The aluminum alloy of this embodiment is an aluminum alloy containing Si, Cu, and Mg, with the remainder being aluminum and impurities, wherein the Si content is greater than 9.5% by weight and 12.5% ​​by weight or less, the Cu content is greater than 0.6% by weight and 1.8% by weight or less, and the Mg content is 0.4% by weight or more and 0.5% by weight or less. The reasons for limiting the chemical composition of the aluminum alloy in this embodiment will be explained.

[0017] Si is an element important for ensuring castability, as it affects the fluidity of the molten aluminum alloy during die casting and the solidification start temperature. The Si content is preferably more than 9.5 wt% and 12.5 wt% or less. If the content is less than or equal to the aforementioned lower limit, it is difficult to ensure castability equivalent to that of ADC12, and if the content is greater than or equal to the aforementioned upper limit, the solidification start temperature begins to rise, which hinders the molding of large-sized parts and simultaneous molding of multiple parts. In particular, when subjected to thermal load, the Si content is preferably set to more than 9.5 wt% and 10.5 wt% or less.

[0018] Cu is an important element for improving the tensile properties of aluminum alloys. The Cu content is preferably more than 0.6 wt% and 1.8 wt% or less. If the content is less than or equal to the aforementioned lower limit, it is necessary to add an aluminum scrap raw material with low Cu content or pure aluminum in order to reduce the Cu content contained in the molten aluminum alloy obtained by melting a plurality of aluminum scrap raw materials. If the content is greater than or equal to the aforementioned upper limit, it is necessary to add Cu scrap to increase the Cu content, which degrades recyclability.

[0019] Mg content is an element important for obtaining tensile properties and creep properties in the present invention. The Mg content is preferably 0.4 wt% or more and 0.5 wt% or less. If the Mg content is less than or equal to the aforementioned lower limit, tensile properties equivalent to those of ADC12 cannot be obtained, and in addition, the types and usage amounts of aluminum scrap raw materials containing a large amount of Mg that can be used are limited. Alternatively, intentionally adding excess Mg and then performing a demagnesization step may cause adverse effects on the environment. If the content is greater than or equal to the aforementioned upper limit, the castability is adversely affected, so the content is limited to 0.5 wt% in the present invention.

[0020] The ratio of Cu content to Mg content (Cu / Mg ratio), expressed as a mass ratio, is preferably 1 to 6, more preferably 1.5 to 5.4, and even more preferably 1.8 to 5.0. When the Cu / Mg ratio is within the above range, the tensile properties and creep characteristics are excellent.

[0021] Conventionally, aluminum alloy raw materials contain copper (Cu), but in the production of AD12.1, additional Cu was added, while the magnesium (Mg) component was removed in a demagnesia process. In this invention, by finding the usefulness of magnesium without adding Cu, it is possible to reduce the additional addition of Cu, which is difficult to separate once dissolved in aluminum, and to reduce the demagnesia process, which has a high environmental impact.

[0022] By adjusting the content of Cu, Si, and Mg according to the above-mentioned content, an aluminum die-cast alloy with recyclability and excellent creep properties can be obtained. Furthermore, it was discovered as a new finding that within the scope of the present invention, the effect of Cu on creep characteristics is small, and that Mg improves creep characteristics.

[0023] The above chemical elements are the basic components contained in the aluminum alloy of this embodiment, and the chemical composition containing these elements, with the remainder being aluminum and impurities, is the basic composition of the aluminum alloy of this embodiment. Here, impurities refer to components that become mixed into aluminum during the industrial production of aluminum alloys, either from raw materials such as ore and scrap, or due to various factors in the manufacturing process.

[0024] In addition to the elements mentioned above, the mixture may also contain either Fe and Ti, or both. The Fe content is preferably 0.6% by weight or more and 1.3% by weight or less. If it is below the lower limit, the castability will decrease due to seizing during molding. Ti has the effect of refining crystal grains and is generally said to be an element that can suppress casting cracks and improve mechanical properties, especially elongation. The Ti content relative to the total weight of the aluminum alloy is preferably within the range of 0.3% by weight or less. If the Ti content exceeds 0.3% by weight, it becomes difficult to dissolve at the typical melting temperature of aluminum alloys, potentially resulting in undissolved residue.

[0025] In this embodiment, it is preferable that the amount of Fe + 2 × Mn + 3 × Cr relative to the total amount (100 wt%) of the aluminum alloy is 1.8 wt% or less. If it exceeds the above upper limit, intermetallic compounds will form in the aluminum alloy, resulting in hard spots when mixed into the aluminum alloy die casting.

[0026] The aluminum alloy of this embodiment is suitable for parts that require heat resistance and are constantly subjected to loads, and is therefore suitable for crankcases, various covers, cylinders, wheel hubs of motorcycles, motor cases and transmission cases of electric vehicles, etc.

[0027] [Manufacturing method for aluminum alloy] The aluminum alloy of this embodiment can be obtained, for example, by a manufacturing method that includes the following melting step. Prepare one or more aluminum scrap raw materials. Melt these raw materials in a melting furnace to obtain molten aluminum alloy. Add metal silicon and other elements as needed to this molten aluminum alloy to obtain an aluminum alloy containing the various elements mentioned above. Perform inclusion removal and dehydrogenation treatment on this molten metal as needed, and pour it into a mold to obtain an aluminum alloy ingot.

[0028] [Aluminum alloy die casting] The aluminum alloy die-cast of this embodiment is made of the aluminum alloy of this embodiment. The shape of the aluminum alloy die-cast of this embodiment is not particularly limited and can be any shape. [Examples]

[0029] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0030] [Examples], [Comparative Examples] The components of the examples and comparative examples are in the amounts shown in Table 3. The measurements were performed using a solid-state emission spectrometer. Tensile properties (specifically tensile strength and 0.2% yield stress) and creep properties were measured by forming the material into a plate shape using a conventional die-casting machine and then machining various test specimens.

[0031] [Table 3]

[0032] [evaluation] "Measurement of tensile properties" The tensile properties of the aluminum alloys in the examples and comparative examples were measured. The tensile properties were measured in accordance with JIS Z 2241. The 0.2% proof stress was measured using the offset method. The results are shown in Table 4.

[0033] "Measuring the creep limit" The creep limits were measured for the aluminum alloys in the examples and comparative examples. The creep test method conformed to JIS Z 2271. The creep test temperature was set at 200°C, and the creep limit was defined as 0.10% / 100 hours for secondary creep (steady-state creep). The results are shown in Table 4.

[0034] [Table 4]

[0035] The results shown in Table 4 indicate that, as seen in Example 1, Comparative Example 1, and Comparative Example 3 (lower limit components for ADC12), a Si content of more than 9.5% by weight and a Mg content of 0.4% by weight or more are necessary to obtain tensile properties equivalent to or better than those of ADC12. As shown in Comparative Examples 2 and 4, no difference in the creep limit was observed in the Si content range of 8.5% by weight to 10.5% by weight. Based on the results of Comparative Examples 2 and 4 described above, and the fact that no improvement in the creep limit was observed with Cu content of 0.8% by weight and 1.6% by weight within the scope of the present invention as shown in Examples 1 and 2, and that Examples 1 and 2 obtained a better creep limit than Comparative Examples 2 and 4, it can be seen that within the scope of the present invention, the Cu content does not have an effect, and excellent creep characteristics can be obtained by increasing the Mg content to 0.4% by weight or more. Furthermore, as shown in Examples 2 and 3, a decrease in creep properties is observed when the Si content exceeds 10.5% by weight, but within the range of up to 12% by weight Si, superior creep properties compared to ADC12 can be obtained.

[0036] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims.

Claims

1. An aluminum alloy containing silicon, copper, and magnesium, with the remainder being aluminum and impurities. The silicon content is greater than 9.5% by weight and less than or equal to 12.5% ​​by weight. The copper content is greater than 0.6% by weight and less than or equal to 1.8% by weight. An aluminum alloy having a magnesium content of 0.4% by weight or more and 0.5% by weight or less.

2. The aforementioned impurities may include one or more selected from zinc, iron, manganese, nickel, titanium, lead, and tin. The zinc content is 2.5% by weight or less. The iron content is 1.3% by weight or less. The manganese content is 0.5% by weight or less. The nickel content is 0.5% by weight or less. The titanium content is 0.3% by weight or less. The lead content is 0.2% by weight or less. The aluminum alloy according to claim 1, wherein the tin content is 0.2% by weight or less.

3. An aluminum alloy die-cast, comprising the aluminum alloy described in claim 1 or 2.

Images