Aluminum alloy

Abstract

The present invention provides an aluminum alloy which has excellent ductility as an aluminum alloy and which makes it possible to suppress seizure in a die-casting step.　Provided is an aluminum alloy for die-casting, said aluminum alloy being characterized by comprising 9.50-10.50 mass% of Si, 0.20-0.50 mass% of Mg, not more than 0.25 mass% of Cu, not more than 0.20 mass% of Zn, not more than 0.50 mass% of Fe, 0.40-0.80 mass% of Mn, 0.04-0.15 mass% of Ti, and 0.01-0.03 mass% of Sr with respect to 100 mass% of the total amount of the aluminum alloy, with the remainder being Al and unavoidable impurities, wherein the total amount of Fe and Mn in mass% satisfies Fe+Mn ≤ 1.05 mass%.

Description

aluminum alloy

[0001] The present invention relates to an aluminum alloy.

[0002] Aluminum alloys are used in various industrial fields, such as automobile parts and aircraft parts. When aluminum scrap is used as a raw material for aluminum alloys, various metals such as Fe and Mn are mixed in as so-called impurities. These impurities affect the properties of the aluminum alloy, and various proposals have been made regarding their content and the properties of the aluminum alloy. For example, Patent Document 1 discloses an aluminum alloy for die casting, which contains 0.01% to 0.7% by mass of Mn and 0.01% to 1.3% by mass of Fe, with a mass ratio of Fe to Mn (Fe / Mn) of 4.4 or less.

[0003] Japanese Patent Application Laid-Open No. 2023-054459

[0004] The Fe and Mn contained in an aluminum alloy affect the strength and ductility of the aluminum alloy, and the tendency for the aluminum alloy to seize on a die when used as a casting raw material. For example, an increase in the Fe or Mn content increases the strength of the aluminum alloy, but decreases its ductility. Therefore, it is desirable to find a suitable composition for an aluminum alloy containing Fe and Mn. The present invention has been made in view of the above circumstances, and aims to provide an aluminum alloy that has excellent ductility as an aluminum alloy and can suppress seizing during a die casting process.

[0005] This specification includes the entire contents of Japanese Patent Application No. 2024-037377, filed on March 11, 2024. In order to achieve the above object, the aluminum alloy according to the present invention is an aluminum alloy for die casting, which, when the total is taken as 100% by mass, contains 9.50% by mass to 10.50% by mass of Si, 0.20% by mass to 0.50% by mass of Mg, 0.25% by mass to 0.25% by mass of Cu, 0.20% by mass to 0.50% by mass of Zn, 0.50% by mass to 0.40% by mass to 0.80% by mass of Mn, 0.04% by mass to 0.15% by mass of Ti, and 0.01% by mass to 0.03% by mass of Sr, with the balance being Al and unavoidable impurities, and the total mass% of Fe and Mn is Fe + Mn ≦ 1.05% by mass.

[0006] According to the present invention, it is possible to provide an aluminum alloy that has excellent ductility as an aluminum alloy and can suppress seizure during a die casting process.

[0007] FIG. 1 is an SEM image of the aluminum alloy of Comparative Example 3.

[0008] The aluminum alloy according to this embodiment is an Al-Si alloy, which contains the second largest amount of Si after Al. The aluminum alloy according to this embodiment may be an alloy obtained from virgin aluminum, but recycled aluminum produced from aluminum scrap can also be used as the raw material. When recycled aluminum is used, the alloy contains impurities such as Mg, Cu, Zn, Fe, Mn, Ti, and Sr in addition to Si, and each component has various effects.

[0009] The effects of aluminum alloy components and their amounts are described below. In the following description, the unit of component content [%] is mass percent concentration. The die-casting process described below refers to, for example, GDC (Gravity Die Casting) or HPDC (High-Pressure Die Casting).

[0010] Si: 9.50% or more and 10.50% or less Si improves the fluidity of the molten metal during casting of the aluminum alloy. On the other hand, as the amount of Si increases, the ductility of the aluminum alloy decreases. For these reasons, the Si content is preferably 9.50% or more and 10.50% or less.

[0011] Mg: 0.20% to 0.50% Although the inclusion of Mg in an aluminum alloy has the effect of improving the tensile strength and yield strength of the aluminum alloy, the toughness tends to decrease as the amount of Mg increases. For these reasons, the Mg content is preferably 0.20% to 0.50%.

[0012] Cu: 0.25% or less Cu reduces the toughness and corrosion resistance of aluminum alloy castings. Therefore, the amount of Cu in the aluminum alloy is preferably 0.25% or less. The amount of Cu in the aluminum alloy is more preferably 0.20% or less.

[0013] Zn: 0.20% or less Zn is an impurity that impairs the corrosion resistance of aluminum alloys, so the amount of Zn is preferably 0.20% or less.

[0014] Mn: 0.40% or more and 0.80% or less. The inclusion of Mn in an aluminum alloy increases the strength of the aluminum alloy in high-temperature regions, thereby affecting the seizure resistance during the die-casting process. That is, if the frictional force between the aluminum alloy and the die exceeds the strength of the aluminum alloy during the die-casting process, the aluminum alloy may adhere to the die. This is an example of the seizure phenomenon in die-casting, in which the aluminum alloy adheres to the die. Mn increases the strength of the aluminum alloy in high-temperature regions, thereby suppressing seizure. The preferred amount of Mn to achieve this effect is 0.40% or more. On the other hand, an increase in the amount of Mn contained in the aluminum alloy generates coarse intermetallic compounds in the aluminum alloy, which increases the hardness of the aluminum alloy and reduces its ductility. Therefore, the Mn content is preferably 0.80% or less.

[0015] Fe: 0.50% or less Fe is known as an unavoidable impurity in recycled aluminum alloys. As the Fe content increases, the intermetallic compounds in the aluminum alloy tend to become larger. Aluminum alloys containing large intermetallic compounds have high strength but low ductility. Therefore, the higher the Fe content in an aluminum alloy, the lower the ductility of the aluminum alloy tends to be. For this reason, the Fe content is preferably 0.50% or less.

[0016] Fe + Mn: 1.05% or less As described above, the Fe and Mn contained in an aluminum alloy each affect the properties of the aluminum alloy. Furthermore, the inventors have discovered that the sum of the Fe and Mn contents, i.e., the amount of Fe + Mn, affects the ductility of the aluminum alloy. That is, as the amount of Fe + Mn increases, the strength of the aluminum alloy increases and the ductility of the aluminum alloy decreases. As described above, Mn has the effect of improving the seizure resistance of the aluminum alloy, but a high Fe + Mn content leads to an excessive decrease in the ductility of the aluminum alloy. This phenomenon may occur even when the amounts of Fe and Mn are within the respective preferred ranges described above. The inventors have found that the preferred range for the Fe + Mn content is Fe + Mn ≦ 1.05%.

[0017] There is no lower limit to the preferred range of the amount of Fe, and it is permissible for the amount of Fe to be 0%.

[0018] In addition to the elements described above, the aluminum alloy of the present invention may contain 0.04% to 0.15% Ti and 0.01% to 0.03% Sr. Ti and Sr have the effect of improving the structure of the aluminum alloy by refining the crystals generated in the aluminum alloy, thereby improving ductility. The preferred contents of Ti are 0.04% to 0.15% and Sr are 0.01% to 0.03% to obtain the effect of improving ductility.

[0019] Examples of the present invention will be described in detail below, but the present invention should not be construed as being limited by the description of these examples. In the following examples, aluminum alloys were produced and evaluated for Examples 1 and 2 to which the present invention was applied, and Comparative Examples 1 to 3 for comparison. To evaluate the produced aluminum alloys, hardness measurements were performed. For hardness measurements, a Rockwell hardness test was performed in accordance with JIS Z2245:2016, "Rockwell Hardness Test - Test Method." The scale used for the Rockwell hardness test was F. That is, the indenter was a hard ball with a diameter of 1.5875 mm, and the test load was 98.07 N. The hardness symbol indicating Rockwell hardness is HRF. The following Examples 1 and 2 and Comparative Examples 1 to 3 were evaluated by the Rockwell hardness test. Table 1 shows the content and HRF of each element contained in the aluminum alloys of Examples 1 and 2 and Comparative Examples 1 to 3. The content is expressed in mass percent.

[0020]

[0021] [Example 1] In Example 1, an aluminum alloy was melted and various elements were added to produce an aluminum alloy containing 10.0% Si, 0.26% Mg, 0.20% Cu, 0.01% Zn, 0.25% Fe, 0.48% Mn, 0.016% Sr, 0.09% Ti, with the balance being Al and unavoidable impurities. In Example 1, the total content of Fe and Mn was 0.73%. In Example 1, an HRF of 91.0 was obtained.

[0022] [Example 2] In Example 2, an aluminum alloy was melted and various elements were added to produce an aluminum alloy containing 10.0% Si, 0.28% Mg, 0.20% Cu, 0.16% Zn, 0.48% Fe, 0.49% Mn, 0.021% Sr, and 0.10% Ti, with the balance being Al and unavoidable impurities. In Example 2, the total content of Fe and Mn was 0.97%. In Example 2, an HRF of 90.3 was obtained.

[0023] [Comparative Example 1] In Comparative Example 1, an aluminum alloy was melted and various elements were added to produce an aluminum alloy containing 10.0% Si, 0.30% Mg, 0.20% Cu, 0.03% Zn, 0.50% Fe, 0.63% Mn, 0.017% Sr, 0.08% Ti, with the balance being Al and unavoidable impurities. In Comparative Example 1, the total content of Fe and Mn was 1.13%. In Comparative Example 1, an HRF of 91.2 was obtained.

[0024] [Comparative Example 2] In Comparative Example 2, an aluminum alloy was melted and various elements were added to produce an aluminum alloy containing 10.0% Si, 0.31% Mg, 0.21% Cu, 0.03% Zn, 0.50% Fe, 0.85% Mn, 0.018% Sr, 0.08% Ti, with the balance being Al and unavoidable impurities. In Comparative Example 2, the total content of Fe and Mn was 1.35%. In Comparative Example 2, an HRF of 92.1 was obtained.

[0025] [Comparative Example 3] In Comparative Example 3, an aluminum alloy was produced by melting an aluminum alloy and adding various elements to it, with the respective contents being 10.4% Si, 0.29% Mg, 0.21% Cu, 0.19% Zn, 0.76% Fe, 0.50% Mn, 0.018% Sr, 0.09% Ti, and the balance being Al and unavoidable impurities. In Comparative Example 3, the total content of Fe and Mn was 1.26%. In Comparative Example 3, an HRF of 90.6 was obtained. FIG. 1 shows an SEM image of the aluminum alloy of Comparative Example 3. A scanning electron microscope (SEM) image was obtained for Comparative Example 3. To evaluate Comparative Example 3, intermetallic compounds generated in the aluminum alloy were observed using the SEM image.

[0026] In Comparative Example 1, Mn was 0.63%, and in Comparative Example 2, Mn was 0.85%, and the HRF increased by 1.0 from Comparative Example 1 to Comparative Example 2. From this, it is expected that there is a Mn content at which the HRF changes between Comparative Example 1 and Comparative Example 2, which is 0.63% or more and 0.85% or less.

[0027] The HRF is an index of ductility. The higher the HRF, the harder the aluminum alloy, and the harder it is, the greater the strength. Therefore, it is expected that the higher the HRF, the lower the ductility of the aluminum alloy. For these reasons, it is preferable that the Mn content be 0.80% or less.

[0028] In Comparative Example 1, the Fe+Mn content is 1.13%, which does not satisfy the condition of Fe+Mn: 1.05% or less. In Comparative Example 2, the Fe+Mn content is 1.35%, which does not satisfy the condition of Fe+Mn: 1.05% or less. Compared to the HRFs in Examples 1 and 2, which satisfy the condition of Fe+Mn: 1.05% or less, the HRFs in Comparative Examples 1 and 2 are large. That is, the aluminum alloys in Comparative Examples 1 and 2 do not satisfy the condition of Fe+Mn: 1.05% or less, and therefore are expected to have reduced ductility. From the above, by setting the Fe+Mn content to 1.05% or less, excessive Fe and Mn are not contained, and excessive reduction in ductility in the aluminum alloy can be suppressed.

[0029] The Fe content increases in the order of Comparative Example 3, Example 2, and Example 1. In FIG. 1, coarse intermetallic compounds are observed at the tips of the arrows in the figure. Therefore, it is expected that the ductility decreases as the Fe content increases. For this reason, it is preferable to set the Fe content to 0.50% or less.

[0030] As described above, the aluminum alloy according to this embodiment is an aluminum alloy for die casting, and is characterized in that, when the whole is taken as 100% by mass, it contains 9.50% by mass or more and 10.50% by mass or less of Si, 0.20% by mass or more and 0.50% by mass or less of Mg, 0.20% by mass or less of Cu, 0.20% by mass or less of Zn, 0.50% by mass or less of Fe, 0.40% by mass or more and 0.80% by mass or less of Mn, 0.04% by mass or more and 0.15% by mass or less of Ti, and 0.01% by mass or more and 0.03% by mass or less of Sr, with the remainder consisting of Al and unavoidable impurities, and the total mass% of Fe and Mn satisfies Fe+Mn≦1.05% by mass.

[0031] This provides excellent ductility for an aluminum alloy and makes it possible to suppress seizure during the die casting process.

[0032] The above embodiment supports the following configurations.

[0033] (Configuration 1) An aluminum alloy for die casting, comprising, based on the total mass of the aluminum alloy, 9.50 to 10.50 mass% Si, 0.20 to 0.50 mass% Mg, 0.20 to 0.20 mass% Cu, 0.20 to 0.50 mass% Zn, 0.50 to 0.50 mass% Fe, 0.40 to 0.80 mass% Mn, 0.04 to 0.15 mass% Ti, and 0.01 to 0.03 mass% Sr, with the balance being Al and unavoidable impurities, wherein the total mass% of Fe and Mn is Fe + Mn ≤ 1.05 mass%, which provides excellent ductility as an aluminum alloy and is capable of suppressing seizure during the die casting process.

Claims

1. An aluminum alloy for die casting, comprising, when the whole is taken as 100% by mass, 9.50% by mass to 10.50% by mass of Si, 0.20% by mass to 0.50% by mass of Mg, 0.25% by mass to 0.25% by mass of Cu, 0.20% by mass to 0.50% by mass of Zn, 0.50% by mass to 0.40% by mass to 0.80% by mass of Mn, 0.04% by mass to 0.15% by mass of Ti, and 0.01% by mass to 0.03% by mass of Sr, with the remainder consisting of Al and unavoidable impurities, and the total mass percentage of Fe and Mn being Fe + Mn ≦ 1.05% by mass.

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