JP7238545B2 - Method for manufacturing aluminum alloy and cast parts - Google Patents

Description

The present invention relates to aluminum alloys and cast parts formed therefrom.

For example, in the mechanical field of automobiles and the like, aluminum alloys are used for the purpose of reducing the weight of various parts. For example, Japanese Patent Application Laid-Open No. 2015-107492 (Patent Document 1) discloses a cast component formed by pouring a molten aluminum alloy having a predetermined composition into a casting mold. The aluminum alloy contains 1-3 wt% Si, 4-6 wt% Mg, 1 wt% or less Fe, 1 wt% or less Mn, and 0.1-0.2 wt% Ti. and at least one of 0.0015 to 0.003% by weight of Be, and 0.5% by weight or less of Cu.

JP 2015-107492 A

Patent Document 1 does not clarify the technical significance of setting the upper limit of the Cu content in the aluminum alloy, and in addition, "0.5% by weight or less" is the only thing. Not disclosed. However, according to the studies of the present inventors, even if the Cu content is 0.5% by weight or less as specified in Patent Document 1, when a cast part is formed using the aluminum alloy, However, it was found that sufficient corrosion resistance could not be obtained in some cases. It is also a general requirement for cast parts that the heat treatment time should be as short as possible.

Realization of an aluminum alloy capable of improving corrosion resistance and shortening the heat treatment time is desired.

The aluminum alloy according to the present disclosure is
1-3 wt% Si, 4-6 wt% Mg, 1.1 wt% or less Fe, 1.1 wt% or less Mn, and 0.1-0.2 wt% Ti , 0.001-0.005% by weight of Be, 0.05-0.15% by weight of Cu, and the balance being Al and unavoidable impurities.

According to the studies of the present inventors, it is possible to reduce the time to peak aging when forming cast parts using the aluminum alloy by including 0.05% by weight or more of Cu in the aluminum alloy. It was revealed. Further, according to the studies of the present inventors, it has become clear that when the Cu content is gradually increased to exceed 0.15% by weight, the corrosion resistance of cast parts obtained from the aluminum alloy deteriorates. rice field. That is, it was found that the corrosion resistance of cast parts can be improved by suppressing the Cu content to 0.15% by weight or less. From the above, 1 to 3 wt% Si, 4 to 6 wt% Mg, 1.1 wt% or less Fe, 1.1 wt% or less Mn, and 0.1 to 0.2 wt% In an aluminum alloy containing Ti, 0.001 to 0.005% by weight of Be, and Cu, the balance being Al and unavoidable impurities, the Cu content is 0.05 to 0.15% by weight By doing so, it is possible to achieve both an improvement in corrosion resistance and a reduction in heat treatment time.

Further features and advantages of the technology according to the present disclosure will become clearer from the following description of exemplary and non-limiting embodiments described with reference to the drawings.

Graph showing the relationship between heat treatment time and hardness Cross-sectional photograph of a cast part obtained from the aluminum alloy of Test Example 1 Cross-sectional photograph of a cast part obtained from the aluminum alloy of Test Example 2 Cross-sectional photograph of a cast part obtained from the aluminum alloy of Test Example 3 Graph showing relationship between Cu content and corrosiveness Schematic diagram showing the valve body

An embodiment of an aluminum alloy will be described with reference to the drawings.

In the following explanations, unless otherwise specified, the numerical range indicated by connecting two numerical values (lower limit and upper limit) with "~" means "(lower limit value) or more (upper limit value) or less". shall be shown. In addition, "%" indicates "% by weight" unless otherwise specified. For example, "0.05 to 0.15%" represents "0.05% by weight or more and 0.15% by weight or less".

The aluminum alloy of the present embodiment contains Si (silicon), Mg (magnesium), Fe (iron), Mn (manganese), Ti (titanium), Be (beryllium), and Cu (copper). contains. The balance excluding these components is Al (aluminum), which may contain trace amounts of unavoidable impurities.

Aluminum alloys contain 1-3% Si and 4-6% Mg. An aluminum alloy containing Si and Mg forms a eutectic of the α-Al phase and the Mg ₂ Si phase. It is considered to be excellent in castability. Since Si forms an Mg ₂ Si phase with Mg, Si is appropriately blended according to the content of Mg, which will be described later.

When the Mg content of the aluminum alloy is less than 4%, Mg ₂ Si is not crystallized so much, and the refinement of the eutectic is limited. On the other hand, if the Mg content exceeds 6%, the possibility of the oxide remaining in the alloy increases, and the oxide impairs castability, or the shape processing (for example, cutting) after casting, the tool may damage the By setting the Mg content to 4 to 6%, the eutectic can be made fine without causing problems during processing. Although the content ratio of Si and Mg is not particularly limited, it is preferably about Si:Mg=1:2 to 1:3, more preferably Si:Mg=2:5.

The aluminum alloy contains less than 1.1% Fe. Also, the aluminum alloy contains 1.1% or less of Mn. Fe and Mn are contained to prevent seizure during casting by pouring molten metal into a mold. The ratio of the content of Fe and Mn is not particularly limited, but the content of Mn is preferably higher than the content of Fe, and more preferably the content of Mn is at least twice the content of Fe. preferable. Moreover, when the amount of Fe and Mn increases, the primary crystal Al ₁₅ (Fe, Mn) ₃ Si ₂ phase is crystallized as the primary crystal. As the primary crystal, α-Al is convenient for ensuring toughness, so the primary crystal Al ₁₅ (Fe, Mn) ₃ Si ₂ phase should not be crystallized. Therefore, it is desirable to keep the Mn content low. However, since Mn is also an element that prevents seizure, a certain amount is required. Therefore, the Mn content is preferably about 0.6%, and overall, the Fe content is preferably less than 0.25%.

Aluminum alloys contain Ti. Ti is contained to refine the primary crystal α-Al phase. In order to efficiently obtain the effect of refining the primary crystal α-Al phase, the appropriate Ti content is 0.1 to 0.2%.

Aluminum alloys contain Be. About 0.001 to 0.005% of Be must be added as a sacrificial oxidation element. About 0.003% of Be is desirable. Also, it is desirable to add a small amount of Al-2.5% Be master alloy, for example, every hour in the molten state. Be is also expected to have a eutectic refinement effect.

Aluminum alloys contain 0.05-0.15% Cu. Cu is included to improve mechanical properties. If the Cu content is less than 0.05%, the time to peak aging will be significantly longer, and if the Cu content is more than 0.15%, the resulting casting will be difficult due to the large potential difference between Cu and Al. Corrosion resistance of parts deteriorates. By setting the Cu content to 0.05 to 0.15%, both improvement in corrosion resistance and reduction in heat treatment time can be achieved.

Unavoidable impurities are impurities contained in raw materials or impurities mixed in during manufacturing for technical or cost reasons (e.g., it is technically impossible to remove, or It is a component that is difficult to remove due to reasons such as high economic expenditure and time required). Examples of unavoidable impurities include Cr (chromium), Ni (nickel), Zn (zinc), and P (phosphorus). They are preferably restricted to a low content since they can have an unfavorable effect on castability. In particular, it is preferable that the content of P is suppressed to 0.001% or less. By setting the P content to 0.001% or less, the crystal can be made finer.

The aluminum alloy of the present embodiment is made of, for example, graphite, high alumina (for example, containing 90% or more of Al ₂ O ₃ and using alumina cement as a binder), quartz, ceramic, metal, or the like. It can be obtained by putting raw materials (for example, high-purity ingots or other alloys) of each component element into a crucible and melting the raw materials in the crucible. In addition, castings (cast parts) manufactured using the aluminum alloy described above are obtained by pouring the aluminum alloy (molten metal) melted as described above into a mold such as a sand mold or a mold and solidifying it. be able to.

The resulting casting (cast part) exhibits sufficient yield strength without heat treatment, but heat treatment is preferably applied to prevent permanent growth occurring in the casting. This heat treatment can be carried out by maintaining a temperature of 160-200° C. for 3-7 hours.

Hereinafter, the aluminum alloy of this embodiment will be described in more detail while showing the results of a plurality of test examples.

A material having each composition shown in Table 1 below was heated and melted at 720° C. in an uncoated graphite crucible to prepare a molten metal for casting. In order to suppress oxidation, the substitution method with an inert element using Ar gas or N ₂ gas is preferable to the atmospheric method. A molten metal of 700° C. was poured into a mold preheated to 150° C. After 5 minutes, the casting was removed from the mold and allowed to cool naturally. After that, heat treatment was performed in an atmospheric electric furnace. The temperature was raised from normal temperature to 180° C. over 10 minutes and maintained at 180° C. for a predetermined time (5 hours to 20 hours). Corrosion resistance was confirmed by spraying a 4% NaCl aqueous solution at room temperature for 72 hours using a salt spray tester, and determining corrosion weight loss after derusting. In the tensile test, a test piece taken from a position 10 mm from the bottom of the mold was processed into a proportional test piece shape defined in JIS14A, and the speed of the load cell was set to 0.1 mm/min until final breakage.

FIG. 1 shows the relationship between the heat treatment time and hardness for each test piece of Test Examples 1 and 2. As shown in FIG. From the graph shown in this figure (graph showing the relationship between heat treatment time and hardness), the test piece of Test Example 2 containing 0.1% Cu is the test piece of Test Example 1 that does not substantially contain Cu. It can be seen that the time to peak aging is significantly shorter than that of .

2 to 4 show electron micrographs of cross sections of the test pieces of Test Examples 1 to 3. FIG. As shown in FIG. 2, in Test Example 1, which does not substantially contain Cu, naturally, precipitation of Al ₂ Cu, which causes corrosion, is not observed. As shown in FIG. 3, even in the test piece of Test Example 2 with a Cu content of 0.1%, precipitation of Al ₂ Cu was not observed. On the other hand, as shown in FIG. 4, it was confirmed that some Al ₂ Cu precipitated in the test piece of Test Example 3 in which the Cu content was increased to 0.2%.

In order to examine the effect of Cu content on corrosiveness (corrosion resistance) in more detail, further tests were conducted using materials of each composition shown in Table 2 below.

FIG. 5 shows the relationship between Cu content and corrosiveness. The vertical axis represents weight loss due to corrosion, and the smaller the value, the higher the corrosion resistance. From the graph shown in this figure (graph showing the relationship between the Cu content and corrosiveness), the corrosion resistance is maintained at least when the Cu content is less than 0.2%, and when the Cu content is about 0.2%, the corrosion resistance is maintained. It can be seen that the corrosion resistance begins to deteriorate a little, and that the corrosion resistance deteriorates significantly at least when the Cu content is 0.5% or more.

This, together with the results of FIG. 1 and the results of FIGS. 2 to 4, demonstrates that the inclusion of 0.1% Cu can both improve corrosion resistance and shorten the heat treatment time. ing. Here, the effect of shortening the heat treatment time by containing Cu is sufficiently achieved even if the Cu content is 0.05%, considering that the horizontal axis of the graph in FIG. 1 is a logarithmic scale. (See also the results of Test Example 4). Also, when the Cu content is 0.2%, although Al ₂ Cu starts to precipitate (see FIG. 4), it cannot be said that the corrosion resistance deteriorates (see FIG. 5). This suggests that there is a critical point near the Cu content of 0.2%, and there is a high possibility that the corrosion resistance will rapidly deteriorate around the critical point.

Conversely, the results of each of the above tests show that the aluminum alloy of the present embodiment improves both corrosion resistance and shortens the heat treatment time by containing 0.05 to 0.15% Cu. It can be said that it suggests that there will be qualitatively remarkable effects that cannot be predicted from technology.

The aluminum alloy of the present embodiment can be used, for example, in transportation equipment (automobiles, ships, railway vehicles, airplanes, etc.), industrial equipment (equipment equipment, production line systems, etc.), or consumer equipment (household appliances, electronic equipment, communication equipment, etc.), etc. can be used for As an example of a more specific application, for example, structural parts for engines (cylinder block, cylinder head, etc.) and automobile-related parts such as case members (transmission case, pump body (see FIG. 6), pump cover, valve body, etc.) Parts are exemplified.

[Outline of embodiment]
To summarize the above, the aluminum alloy according to the present disclosure preferably has the following configurations.

an aluminum alloy,
1-3 wt% Si, 4-6 wt% Mg, 1.1 wt% or less Fe, 1.1 wt% or less Mn, and 0.1-0.2 wt% Ti , 0.001-0.005% by weight of Be, 0.05-0.15% by weight of Cu, and the balance being Al and unavoidable impurities.

According to the studies of the present inventors, it is possible to reduce the time to peak aging when forming cast parts using the aluminum alloy by including 0.05% by weight or more of Cu in the aluminum alloy. It was revealed. Further, according to the studies of the present inventors, it has become clear that when the Cu content is gradually increased to exceed 0.15% by weight, the corrosion resistance of cast parts obtained from the aluminum alloy deteriorates. rice field. That is, it was found that the corrosion resistance of cast parts can be improved by suppressing the Cu content to 0.15% by weight or less. From the above, 1 to 3 wt% Si, 4 to 6 wt% Mg, 1.1 wt% or less Fe, 1.1 wt% or less Mn, and 0.1 to 0.2 wt% In an aluminum alloy containing Ti, 0.001 to 0.005% by weight of Be, and Cu, the balance being Al and unavoidable impurities, the Cu content is 0.05 to 0.15% by weight By doing so, it is possible to achieve both an improvement in corrosion resistance and a reduction in heat treatment time.

As one aspect,
When P is contained as one of the unavoidable impurities, the P content is preferably 0.0010% by weight or less.

According to this configuration, the crystals of the aluminum alloy can be finely refined.

As one aspect,
It is preferable that the content of Mn is higher than the content of Fe.

According to this configuration, it is possible to satisfactorily prevent seizure when pouring a molten aluminum alloy into a mold for casting.

Also, the cast component according to the present disclosure preferably has the following configuration.

Cast parts formed using the aluminum alloys having the above configurations,
After pouring the molten metal into the mold and casting, the resulting casting is maintained at 160-200° C. for 3-7 hours.

According to this configuration, by using the aluminum alloy described above and taking advantage of the characteristic that the time until peak aging is short, a cast part with excellent corrosion resistance can be efficiently obtained by heat treatment for a relatively short time of 3 to 7 hours. can be done.

The aluminum alloy and cast part according to the present disclosure only need to exhibit at least one of the effects described above.

Claims (4)

1-3 wt% Si, 4-6 wt% Mg, 1.1 wt% or less Fe, 1.1 wt% or less Mn, and 0.1-0.2 wt% Ti , 0.001-0.005% by weight of Be, 0.05-0.15% by weight of Cu, the balance being Al and unavoidable impurities. The aluminum alloy according to claim 1 , wherein the content of Mn is higher than the content of Fe. Si, Mg, Fe, Mn, Ti, Be, Cu, and Al, containing 1 to 3% by weight of Si, 4 to 6% by weight of Mg, 1.1% by weight or less of Fe, and 1.1% by weight of Mn Below, Ti is 0.1 to 0.2% by weight, Be is 0.001 to 0.005% by weight, Cu is 0.05 to 0.15% by weight, and the balance is Al and unavoidable impurities. A step of putting it in and heating it to obtain a molten metal;
A step of pouring the molten metal into a mold and casting to obtain a casting;
A method of manufacturing a cast part , comprising : 4. The method of manufacturing a cast component according to claim 3, further comprising maintaining the casting at 160-200° C. for 3-7 hours.

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