WO2016166779A1 - Aluminum alloy for die casting, and die-cast aluminum alloy using same - Google Patents

Abstract

Provided is an aluminum alloy for die casting, which despite containing Cu in a proportion such that improved mechanical strength is achieved, experiences no appreciable loss of corrosion resistance, and is suitable for critical safety components of automobiles and the like, and a die cast aluminum alloy die-cast from this alloy. Specifically, the present invention provides an aluminum alloy for die casting, characterized by containing, in wt%, 0.03% < Cu ≤ 0.7%, 6.0% < Si ≤ 11.0%, 0.15% ≤ Mg ≤ 0.50%, 0.05% ≤ Fe ≤ 0.6%, 0.05% ≤ Ti ≤ 0.25%, Mn ≤ 0.8%, and 0.10% ≤ Cr ≤ 0.40%, the remainder being Al and unavoidable impurities.

Description

Aluminum alloy for die casting and aluminum alloy die casting using the same

The present invention relates to an aluminum alloy for die casting excellent in mechanical properties and corrosion resistance, and an aluminum alloy die casting using the alloy.

Aluminum alloys are widely used as component materials in automobiles, industrial machines, aircraft, home appliances, and various other fields because they are lightweight and excellent in formability and mass productivity.
Among these, in automotive applications, the application of aluminum alloy die castings to bodies and underbody parts has been expanded for the purpose of reducing the weight of the car body and the fuel consumption associated therewith. Thus, in recent years, many parts using aluminum alloy have been adopted, while many of these parts are important safety parts, so they have not only mechanical properties such as resistance and ductility. And corrosion resistance that can endure long-term use from the viewpoint of the required service life and the use environment. For this reason, in the case of existing alloys, although the mechanical properties required for such parts can be satisfied, it is beginning to occur that the corrosion resistance can not be satisfied.

Therefore, as one of the techniques for solving such a problem, for example, as a material suitable for a safety component such as a wheel of a car, Patent Document 1 below has a weight of 9.5 to 11.5. % Silicon, 0.1 to 0.5% by weight magnesium, 0.5 to 0.8% by weight manganese, up to 0.15% by weight iron, up to 0.03% by weight copper, up to 0.10 A die-casting aluminum alloy is disclosed which comprises by weight zinc, up to 0.15% by weight titanium, the balance being aluminum and 30 to 300 ppm strontium as a permanent atomizing agent.
According to this technology, since the content of Cu which corrodes the aluminum alloy by the battery action is suppressed to 0.03% by weight at the maximum, the die-casting aluminum alloy having high corrosion resistance can be provided.

Patent No. 3255560

However, if the content of Cu is limited as described above in order to improve the corrosion resistance, it is practically impossible to use scrap raw materials, and it becomes impossible not only to be able to economically manufacture aluminum alloys but also to promote a recycling society. It becomes rate-limiting in construction. Also, Cu has an effect of improving mechanical properties such as tensile strength and 0.2% proof stress with respect to aluminum alloy, but if the content ratio of Cu is limited to 0.03% by weight or less, Such effects can not be expected either.
Therefore, the main object of the present invention is that although Cu is contained in a proportion capable of exhibiting the effect of improving mechanical properties, the corrosion resistance is not significantly deteriorated and it is suitable for important safety parts of automobiles and the like. An object of the present invention is to provide an aluminum alloy for die casting and an aluminum alloy die cast from the alloy.

The first invention in the present invention is “by weight%, 0.03% <Cu ≦ 0.7%, 6.0% <Si ≦ 11.0%, 0.15% ≦ Mg ≦ 0.50%, 0.05% ≦ Fe ≦ 0.6%, 0.05% ≦ Ti ≦ 0.25%, Mn ≦ 0.8%, 0.10% ≦ Cr ≦ 0.40%, and the balance is Al It is an aluminum alloy for die-casting characterized by consisting of an unavoidable impurity.
In this invention, since Cu can be contained in the range of more than 0.03 wt% to 0.7 wt% or less, in addition to enabling the use of recycled raw materials, particularly tensile strength and 0.2% It is possible to improve mechanical properties such as proof stress. Further, since Cr is contained in an amount of 0.10% by weight or more and 0.40% by weight or less in combination with the content of Cu within the above range, the deterioration of the corrosion resistance can be prevented.
As described above, in the present invention, an aluminum alloy for die-casting which is excellent not only in castability and mechanical properties but also in corrosion resistance by the mutual action of the seven types of elemental components only by containing the predetermined proportions. Can be safely and conveniently manufactured.

In the aluminum alloy for die casting of the present invention, it is preferable to add 30 to 200 ppm of at least one selected from Na, Sr and Ca and to add 0.05 to 0.20% by weight of Sb. By so doing, particles of eutectic Si can be made finer, and the toughness and strength of the aluminum alloy can be further improved.
It is also preferable to add 1 to 50 ppm of B. By so doing, the crystal grains of the aluminum alloy can be made finer even if the amount of Si is small or the casting method with a slow cooling rate is used, and as a result, the elongation of the aluminum alloy is improved. Can.

A second invention according to the present invention is an aluminum alloy die cast made by die casting using the aluminum alloy for die casting according to the first invention.
The aluminum alloy die cast by the die casting aluminum alloy of the present invention can be mass-produced with good castability, and is excellent not only in mechanical properties such as tensile strength and hardness but also in corrosion resistance. Ideal for applications such as

According to the present invention, although containing Cu in a proportion capable of exhibiting the effect of improving mechanical properties, the aluminum alloy for die casting suitable for important safety parts of automobiles, etc., does not significantly deteriorate the corrosion resistance. And an aluminum alloy die cast from the alloy.

It is a graph which shows the relationship between the content rate of Cu and the mechanical property in the aluminum alloy for die casting. It is a graph which shows the relationship between the content rate of Cu and Cr in the aluminum alloy for die casting, and corrosion resistance. It is a graph which shows the relationship of the content rate of Ti and mechanical property in aluminum alloys for die-casts.

Hereinafter, embodiments of the present invention will be described in detail by way of specific examples.
The aluminum alloy for die casting of the present invention (hereinafter, also simply referred to as “aluminum alloy”) is, by weight, 0.03% <Cu (copper) ≦ 0.7%, 6.0% <Si (silicon) ≦ 11.0%, 0.15% ≦ Mg (magnesium) ≦ 0.50%, 0.05% ≦ Fe (iron) ≦ 0.6%, 0.05% ≦ Ti (titanium) ≦ 0.25%, It contains Mn (manganese) ≦ 0.8%, 0.1% ≦ Cr (chromium) ≦ 0.4%, and the balance is roughly constituted of Al (aluminum) and unavoidable impurities. The characteristics of each element will be described below.

Cu (copper) is an important element for improving the wear resistance, mechanical strength and hardness of aluminum alloys.
The content ratio of Cu to the weight of the entire aluminum alloy is preferably in the range of more than 0.03% by weight and 0.7% by weight or less as described above. If the content ratio of Cu is 0.03 wt% or less, the above-mentioned mechanical property improvement effect can not be obtained, conversely, if the content ratio of Cu exceeds 0.7 wt%, the corrosion resistance Problems such as a significant decrease in growth, a decrease in growth, an increase in specific gravity, and an increase in raw material costs.
When a particularly high corrosion resistance is required for the obtained aluminum alloy, the content of Cu is preferably in the range of more than 0.03% by weight and 0.2% by weight or less.

Si (silicon) is an important element which secures the fluidity at the time of aluminum alloy melting and improves the castability.
It is preferable that the content ratio of Si with respect to the weight of the entire aluminum alloy is in the range of 6.0 wt% or more and 11.0 wt% or less as described above. When the content of Si is less than 6.0% by weight, it is difficult to secure the fluidity of the molten metal, and in the case of forming by a general die-cast generally used widely, application to large parts On the other hand, if the content of Si exceeds 11.0% by weight, the elongation of the alloy will be reduced.

Mg (magnesium) mainly exists in the form of a solid solution in an Al base material in an aluminum alloy or as Mg ₂ Si and imparts yield strength and tensile strength to the aluminum alloy, while containing castable or corrosion resistant due to inclusion of an excessive amount. Is a component that adversely affects
It is preferable that the content ratio of Mg with respect to the weight of the entire aluminum alloy is in the range of 0.15 wt% or more and 0.5 wt% or less as described above. If the content ratio of Mg is less than 0.15% by weight, the above-mentioned effects can not be sufficiently obtained, and conversely, if the content ratio of Mg exceeds 0.5% by weight, the elongation of the alloy And corrosion resistance will be reduced.

Fe (iron) is known to have a seizure prevention effect at the time of die casting. However, this Fe crystallizes needle-like crystals consisting of Al-Si-Fe, and reduces the toughness of the aluminum alloy, and when added in large amounts, makes it difficult to melt at an appropriate temperature.
The content of Fe based on the weight of the entire aluminum alloy is preferably in the range of 0.05 to 0.6% by weight as described above. If the Fe content ratio is less than 0.05% by weight, the seizure prevention effect at the time of die casting is not sufficient. Conversely, if the Fe content ratio is more than 0.6% by weight, the above seizure occurs. Although the prevention effect is sufficient, the toughness of the alloy is lowered and the melting temperature is raised to deteriorate the castability.

Ti (titanium) has the effect of refining crystal grains, and is generally said to be an element capable of improving elongation, among the suppression of casting cracks and mechanical properties.
The content of Ti relative to the weight of the entire aluminum alloy is preferably in the range of 0.05% by weight or more and 0.25% by weight or less. If the content ratio of Ti is less than 0.05% by weight, it is difficult to refine the crystal grains in the aluminum alloy, and conversely, if the content ratio of Ti exceeds 0.25% by weight, This is because the melting of the aluminum alloy becomes difficult, and the possibility of the occurrence of the unmelted part will arise.
In addition, in the aluminum alloy of the present invention component, as described later, due to the interaction of the component compositions, the content ratio of Ti is approximately 0.25% by weight or less as the content ratio of Ti increases. While the tensile strength and 0.2% proof stress of the aluminum alloy were improved, it was found as a new finding that the elongation was hardly affected.

Mn (manganese) is mainly for preventing seizing between the aluminum alloy and the mold at the time of die casting, similarly to Fe described above. Like Fe, too much content of Mn makes it difficult to melt at an appropriate temperature. Therefore, in the present invention, the content of Mn with respect to the weight of the entire aluminum alloy is suppressed to 0.8% by weight or less.
The lower limit of the content of Mn is not particularly limited, but in order to exert the above-mentioned anti-seizure effect remarkably, it is preferable to contain Mn in an amount of 0.2% by weight or more.

Cr (chromium) is an element having an effect of improving the corrosion resistance of the alloy in addition to preventing the seizure between the aluminum alloy and the die at the time of die casting, similarly to Fe and Mn described above.
The content of Cr relative to the weight of the entire aluminum alloy is preferably in the range of 0.1 wt% or more and 0.4 wt% or less as described above. If the content ratio of Cr is less than 0.1% by weight, the above-mentioned effects can not be sufficiently obtained, and conversely, if the content ratio of Cr exceeds 0.4% by weight, further addition is made Even if the amount is increased, the addition effect can not be improved.

If the content ratio of Cu, Si, Mg, Fe, Ti, Mn and Cr is adjusted according to the above content ratio, not only castability and mechanical properties but also corrosion resistance can be achieved even though it is a safe recipe with high safety. Excellent die-casting aluminum alloy ingots can be obtained.

In addition to the above-described respective element components, at least one selected from Na (sodium), Sr (strontium), Ca (calcium) and Sb (antimony) may be added as the improvement treatment material. By adding such an improvement treatment material, particles of eutectic Si can be made finer, and the toughness and strength of the aluminum alloy can be further improved.
Here, the addition ratio of the improved material to the total weight of the aluminum alloy is 30 to 200 ppm when the improved material is Na, Sr and Ca, and 0.05 to 0.20% by weight when Sb is used. It is preferable that it is a range. If the addition ratio of the improvement treatment material is less than 30 ppm (0.05% by weight in the case of Sb), it becomes difficult to refine the particles of eutectic Si in the aluminum alloy, conversely, the improvement treatment material In the case where the addition ratio of is greater than 200 ppm (0.20% by weight in the case of Sb), the particles of eutectic Si in the aluminum alloy are sufficiently finely divided, and addition is possible even if the addition amount is further increased It is because the effect does not rise.

Further, B (boron) may be added instead of the above-mentioned improved treatment material or together with the improvement treatment material. By adding B in this manner, the crystal grains of the aluminum alloy can be refined, and the elongation of the alloy can be improved. Such an effect is particularly remarkable when the amount of Si is small or when a casting method with a slow cooling rate is used.
The proportion of B added to the total weight of the aluminum alloy is preferably in the range of 1 to 50 ppm. When the addition ratio of B is less than 1 ppm, it is difficult to refine the crystal grains in the aluminum alloy, and conversely, when the addition ratio of B is more than 50 ppm, the crystal grains in the aluminum alloy are sufficient. The effect of addition is not improved even if the amount of addition is further increased.

In the case of producing the aluminum alloy for die casting of the present invention, first, the raw materials contained such that the respective elemental components of Al, Cu, Si, Mg, Fe, Ti, Mn and Cr become the above-mentioned predetermined ratio are Prepare (If necessary, add the above-mentioned improved materials etc.). Subsequently, the raw material is put into a melting furnace such as a forging furnace-containing melting furnace or a closed melting furnace to melt these materials. The molten raw material thus melted, that is, the molten metal of the aluminum alloy, is subjected to a purification treatment such as dehydrogenation treatment and removal treatment, if necessary. Then, the refined molten metal is poured into a predetermined mold or the like and solidified to form a molten metal of an aluminum alloy into an alloy base metal ingot or the like.

In addition, after casting an aluminum alloy die cast using the aluminum alloy for die casting of the present invention, solution treatment, aging treatment and the like are performed as needed. Thus, the mechanical properties of the aluminum alloy casting can be improved by subjecting the aluminum alloy die cast to solution treatment, aging treatment and the like.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the examples.
The mechanical properties (specifically, tensile strength, elongation, 0.2% proof stress) in the following various alloys were measured by the following methods. That is, using an ordinary die casting machine with a clamping force of 135 tons (DC 135EL manufactured by Toshiba Machine Co., Ltd.), die casting is performed at an injection speed of 1.0 m / s and a casting pressure of 60 MPa. ASTM (American Society for Testing and Material) Round bar test piece conforming to the standard was prepared. The tensile strength, elongation and 0.2% proof stress of the as-cast round bar test pieces were measured using a universal tester (AG-IS 100 kN) manufactured by Shimadzu Corporation.
In addition, alloy components of various alloys were measured using a solid-state emission spectrometer (Thermo Scientific ARL 4460 manufactured by Thermo Fisher Scientific Co., Ltd.).
Furthermore, the corrosion resistance was evaluated by a (neutral) salt spray test in accordance with Japanese Industrial Standard JIS Z2371. At that time, the test was carried out using a Cass tester CASSER-ISO-3 manufactured by Suga Test Instruments Co., Ltd.

Influence of Cu on Aluminum Alloy Physical Properties Table 1 shows that an alloy component other than Cu is adjusted to be a certain ratio within the range of the present invention, and an aluminum alloy for die casting manufactured by changing the content ratio of Cu. It shows the component composition and each mechanical property (tensile strength, elongation, 0.2% proof stress).

As Table 1 shows, when the content ratio of Cu is approximately 1.0% by weight or less, as the content ratio of Cu increases, the tensile strength of the aluminum alloy (see FIG. 1-1) and It can be seen that the 0.2% proof stress (see Figure 1-2) improves.
On the other hand, the elongation of the aluminum alloy tends to decrease as the Cu content exceeds 0.7% by weight.
Alloys 3 to 11 in Table 1 have alloy compositions within the scope of the present invention, that is, Example alloys.

Corrosion resistance improvement effect by inclusion of Cr Table 2 is a table showing the relationship between the corrosion resistance and the composition of each aluminum alloy according to the casting method.
Here, the die-cast ones in Table 2 were cast by the same method as the sample used for the above-mentioned mechanical property measurement. On the other hand, for gravity casting in Table 2, the aluminum alloy adjusted to predetermined components is poured into a mold and gravity casting is performed, and thereafter a sample for salt water spray test in accordance with JIS Z 2371 similar to die casting (corrosion resistance They were processed into evaluation test pieces and subjected to a salt spray test.

As Table 2 shows, in a cast product obtained by die casting, when the content ratio of Cu is constant at 0.10% by weight, the corrosion loss decreases when the content ratio of Cr becomes 0.10% by weight or more. The corrosion resistance can be improved (see Figure 2-1).
Further, in a cast product obtained by die casting, when the content ratio of Cr is constant at 0.20% by weight, corrosion is accompanied by increasing the content ratio of Cu from 0.10% by weight to 0.73% by weight. Weight loss also increased, indicating a tendency for corrosion resistance to deteriorate (see Figure 2-3).
In addition, even in a cast product obtained by gravity casting, the corrosion resistance of the alloy deteriorates with an increase in the content of Cu, but by containing 0.20% by weight of Cr, the corrosion loss is remarkably reduced and the corrosion resistance is It has become clear that it can be improved (see Figure 2-2).
The alloys 15 to 20, 26 and 27 in Table 2 have alloy compositions within the scope of the present invention, ie, example alloys.

Influence of Ti on Aluminum Alloy Physical Properties Table 3 shows that aluminum alloy components for die-casting manufactured by adjusting the alloy components other than Ti to a certain ratio within the scope of the present invention and changing the content ratio of Ti It shows the component composition and each mechanical property (tensile strength, elongation, 0.2% proof stress).

As Table 3 shows, when the content ratio of Ti is approximately 0.25% by weight or less, as the content ratio of Ti increases, the tensile strength of the aluminum alloy (see FIG. 3-1) and 0 It can be seen that the 2% proof stress (see Figure 3-2) is improved.
On the other hand, no significant difference was observed in the elongation of the aluminum alloy with the content ratio of Ti within the range where the content ratio of Ti is approximately 0.25% by weight or less (FIG. 3-3).
The alloys 30 to 32 in Table 3 have alloy compositions within the scope of the present invention, ie, example alloys.

Claims (5)

In% by weight, 0.03% <Cu ≦ 0.7%, 6.0% <Si ≦ 11.0%, 0.15% ≦ Mg ≦ 0.50%, 0.05% ≦ Fe ≦ 0.6 %, 0.05% ≦ Ti ≦ 0.25%, Mn ≦ 0.8%, 0.10% ≦ Cr ≦ 0.40%, and the balance is made of Al and unavoidable impurities. Aluminum alloy for die casting. The aluminum alloy for die casting according to claim 1, wherein 30 to 200 ppm of at least one selected from Na, Sr and Ca is added. The die-casting aluminum alloy according to claim 1 or 2, wherein 0.05 to 0.20% by weight of Sb is added. The aluminum alloy for die casting according to any one of claims 1 to 4, wherein 1 to 50 ppm of B is added. An aluminum alloy die cast made of the die casting aluminum alloy according to any one of claims 1 to 4.

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