KR20140034557A - Al-cu alloy having high thermal conductivity for die casting - Google Patents

Abstract

The present invention relates to an aluminum alloy for die casting which can obtain excellent thermal conductivity while simultaneously having a remarkable casting property and satisfactory mechanical characteristics, and thus can be applied to a product for various structures requiring heat dissipating characteristics. According to the present invention, the aluminum alloy for die casting comprises 0.8-2.5 wt% of copper (Cu), 0.5-1.5 wt% of magnesium (Mg), 0.5-1.0 wt% of iron (Fe), and the balance of aluminum (Al) and inevitable impurities.

Description

High Thermal Conductivity Alloy Die-Cu Alloy for Die Casting {Al-Cu ALLOY HAVING HIGH THERMAL CONDUCTIVITY FOR DIE CASTING}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high thermal conductivity aluminum alloy for die casting, and more particularly, to an aluminum alloy capable of obtaining excellent castability and at the same time excellent thermal conductivity.

Die casting is also called die casting. Die casting is a precision casting method in which molten metal is injected into a steel mold precisely machined to perfectly match the required casting shape, thereby obtaining the same casting as the mold. The product is called diecast casting. In addition to the advantages that die-casting castings are precisely dimensioned and hardly need to be trimmed, they are characterized by excellent mechanical properties and mass production.

The metal used in such die casting casting is generally an alloy of zinc, aluminum, tin, copper, magnesium and the like. These alloys are melted and made into a molten metal, and then they are cast through a press device such as air pressure, water pressure, And rapidly cooled and solidified.

Die casting castings produced through this process are used in various fields, particularly in automobile parts, and are widely used in the production of parts for electric devices, optical instruments, vehicles, textile machines, architectural instruments, and the like.

On the other hand, as the aluminum alloy for die casting, an Al-Si alloy and an Al-Mg alloy which are excellent in casting are mainly used. However, Al-Si alloy or Al-Mg alloy has excellent main composition but low thermal conductivity of 90 ~ 130 W / mK. Therefore, heat dissipation for electric, electronic, and automobile requiring high thermal conductivity of 160 W / mK or more The use of parts has been limited.

For heat dissipation parts requiring such a high thermal conductivity, a product made by die-casting pure aluminum with a very high thermal conductivity of 220 W / mK or more is partially used for electric and electronic products, and pure aluminum has excellent thermal conductivity However, since the tensile strength is low and the casting is poor, there is a limit to apply to structural parts requiring excellent mechanical properties along with thermal conductivity.

Accordingly, there is a great demand for the development of an aluminum alloy for die casting having excellent main composition and high thermal conductivity of 160 W / mK or more for use in heat dissipation parts for electric, electronic and automobile applications. However, until now, Al-Si-based alloys and Al-Mg-based alloys with thermal conductivity of 90 to 130 W / mK have been used as aluminum alloys for die casting, since aluminum alloys for die casting having a thermal conductivity of 160 W / mK or more have not been developed at the same time It is true.

The present invention has been made in order to solve the above problems by adding copper (Cu) as the main alloying elements and by controlling the content of magnesium (Mg) and iron (Fe), while having excellent castability and at the same time more than 160W / mK It is an object of the present invention to provide an aluminum alloy for die casting having thermal conductivity.

In order to solve the above problems, the present invention includes 0.8 to 2.5% by weight of copper (Cu), 0.5 to 1.5% by weight of magnesium (Mg) and 0.5 to 1.0% by weight of iron (Fe), with the remainder being aluminum (Al). It provides an aluminum alloy for die casting consisting of and inevitable impurities.

In addition, the aluminum alloy according to the present invention may have a thermal conductivity of 160 W / mK or more.

In addition, in the aluminum alloy according to the present invention, ΔT (T _L −T _S ), which is a difference between the liquidus temperature T _L and the solidus temperature T _S , which is an index indicating castability, may be 60 ° C. or less.

In addition, in the aluminum alloy according to the present invention, the heat of fusion H, which is another index indicating castability, may be 300 J / g or more.

In the aluminum alloy according to the present invention, the ratio H / ΔT of ΔT (T _L -T _S ), which is the difference between the heat of fusion (H), the liquidus temperature (T _L ) and the solidus temperature (T _S ), is 5.3J. / g ° C. or higher.

In addition, the aluminum alloy according to the present invention has a tensile strength of 120 MPa or more.

In addition, the aluminum alloy according to the present invention may include an Al—Cu compound and an Al—Fe compound dispersed in a microstructure.

In addition, in the aluminum alloy according to the present invention, the content of copper (Cu) may be 1.2 to 2.5% by weight.

In addition, the aluminum alloy according to the present invention, the thermal conductivity is 170W / mK or more, the tensile strength may be 145MPa or more.

In the aluminum alloy according to the present invention, by adding copper (Cu) as the main alloying element and controlling the composition of magnesium (Mg) and iron (Fe), the aluminum alloy ensures sufficient castability required for obtaining a sound casting in the die casting casting method. At the same time, having excellent thermal conductivity of 160W / mK and tensile strength of 120MPa or more, it can be suitably used for the manufacture of heat dissipating parts for electric, electronic and automotive which require high thermal conductivity and require a considerable level of mechanical strength.

Hereinafter, an aluminum alloy according to a preferred embodiment of the present invention will be described in detail, but the present invention is not limited to the following examples. Accordingly, it is obvious that those skilled in the art can variously change the present invention without departing from the technical idea of the present invention.

Furthermore, the singular forms used to describe the embodiments of the present invention are meant to include plural forms unless the phrases expressly have the opposite meaning.

The aluminum alloy according to the present invention is a high thermal conductivity aluminum alloy for die casting in which copper (Cu), magnesium (Mg), and iron (Fe) are alloyed, and 0.8 to 2.5% by weight of copper (Cu) and 0.5 to magnesium (Mg). 1.5 wt% and 0.5-1.0 wt% iron (Fe), the remainder is composed of aluminum (Al) and unavoidable impurities.

According to the present invention, the thermal conductivity of the alloy element which can improve the castability of aluminum and the alloy element which can be dissolved in the aluminum base metal to obtain a solid solution effect, and the solubility in the aluminum base metal are very low. It is a high thermal conductivity aluminum alloy for die casting which can exhibit excellent castability and tensile strength of 120 MPa or more, and exhibit good thermal conductivity of 160 W / mK or more by adding an alloying element which can minimize degradation.

The reasons for the addition and content of each alloy element are as follows.

Copper (Cu) is an alloying element that can be added as an alloying element to aluminum and decrease the thermal conductivity while depositing a solid solution strengthening effect and intermetallic compounds such as CuAl ₂ to increase the tensile strength. In the alloy according to the present invention, copper is added in an amount of 0.8 to 2.5% by weight, which means that when the copper content is less than 0.8% by weight, the tensile strength is lowered to obtain a tensile strength of 120 MPa or more, and when the copper content is greater than 2.5% by weight, This is because the thermal conductivity of the cast alloy is lowered and thermal conductivity of 160 W / mK or more cannot be obtained. The content of copper (Cu) is more preferably maintained at 1.2 to 2.5% by weight.

Magnesium (Mg) is an element that can be added as an alloying element to aluminum to improve castability and decrease thermal conductivity while increasing tensile strength according to solid solution strengthening effects. In the die-casting aluminum alloy according to the present invention, magnesium is added in an amount of 0.5 to 1.5% by weight. In the case where the magnesium content is less than 0.5% by weight, castability is lowered, so that some unmolded parts are produced when molding a product by die casting. This is because defects are likely to occur, and when the magnesium content exceeds 1.5% by weight, the thermal conductivity is lowered, and thermal conductivity of 160 W / mK or more cannot be obtained.

Iron (Fe) has a very low solubility in aluminum at normal temperature of 0.052% by weight, and after casting it is mainly crystallized as an intermetallic compound such as Al ₃ Fe. Therefore, it is added to aluminum to increase the strength while minimizing deterioration of thermal conductivity of aluminum And at the same time, it is an alloying element which can reduce mold seizure when molding an aluminum alloy product by die casting. In the die casting alloy according to the present invention, iron is added in an amount of 0.5 to 1.0% by weight. When the iron content is less than 0.5% by weight, the effect of preventing mold quenching is reduced. This occurs because the mechanical strength is not sufficient, and if the iron content exceeds 1.0% by weight, the Fe-rich phase (Fe-rich phase) is excessively crystallized in the cast alloy, thereby degrading the castability of the alloy.

The unavoidable impurity means an impurity unintentionally incorporated by the raw material or the manufacturing apparatus in the process of producing the alloy according to the present invention, and examples thereof include Ti, Cr, V, Mn, Li, and Zr. Each of these impurities is kept at 0.1 wt% or less, preferably 0.01 wt% or less, so as not to affect the alloy properties.

[Example]

A high thermal conductivity Al-Cu alloy for die casting according to an embodiment of the present invention will be described in detail with reference to Tables 1 to 3 below.

The inventors of the present invention prepared a test piece of the alloy having the composition shown in Table 1 to produce a high thermal conductivity Al-Cu alloy for die casting by a melt stirring aluminum alloy manufacturing method commonly used in the production of die casting alloy.

alloy Composition (% by weight) Cu Mg Fe Si Al Example One 1.01 0.52 0.59 - honey. 2 0.91 1.08 0.55 - honey. 3 1.37 0.51 0.62 - honey. 4 1.34 1.07 0.59 - honey. 5 1.90 0.56 0.62 - honey. 6 1.86 1.07 0.60 - honey. Comparative Example 7 0.92 0.21 0.97 10.20 honey. 8 2.6 0.5 0.7 - honey. 9 0.1 2.2 0.4 - honey. 10 0.4 1.0 0.7 - honey.

Specifically, a raw material for an aluminum alloy was prepared so as to have a composition as shown in Table 1, and then charged in an electric resistance type melting furnace to dissolve the raw materials in the atmosphere to prepare a molten metal. Thereafter, using a mold, (T _L -T _S ), which is the difference between the solidus temperature (T _L ) and the solidus temperature (T _S ), and the melting heat (H) A test piece was prepared.

With respect to the thermal conductivity, which is one of the main objects of the alloy according to the embodiment of the present invention, the conductivity of the specimen manufactured first is measured at room temperature by using a conductivity meter and then converted into a conversion formula of the following formula Thermal conductivity was obtained.

[Formula 1]

K = 5.02? T x 10 ^-9 + 0.03

(Where K is thermal conductivity, σ is conductivity, and T is absolute temperature)

In order to evaluate castability, which is indispensable for die casting casting, ΔT (T _L -T _S ), which is the difference between the liquidus temperature (T _L ) and the solidus temperature (T _S ), and the heat of fusion .

Table 2 shows the thermal conductivity of each alloy, the liquidus temperature (T _L ), the solidus temperature (T _S ), the difference between the liquidus temperature (T _L ) and solidus temperature (T _S ) ΔT (T _L -T _S ), melting It shows the result of evaluating the ratio H / ΔT of ΔT (T _L -T _S ), which is the difference between heat (H) and heat of fusion (H), liquidus temperature (T _L ), and solidus temperature (T _S ). .

alloy Thermal conductivity
(W / mK) Liquid temperature (T _L )
(℃) The solid-state temperature (T _s )
(℃) DELTA T (T _L -T _S )
(℃) Heat of fusion (H)
(J / g) H / △ T
(J / g ℃) Example One 186 657 620 37 332 8.97 2 175 655 612 43 322 7.49 3 179 657 612 45 326 7.24 4 171 656 601 55 300 5.45 5 179 654 602 52 317 6.10 6 167 650 590 60 322 5.37 Comparative Example 7 95 575 501 74 311 4.20 8 154 - - - - - 9 138 649 607 42 - - 10 180 652 582 70 - -

As can be seen from Table 2, the aluminum alloys according to the embodiments of the present invention all have a thermal conductivity of 160 W / mK or more and have a thermal conductivity as high as or higher than that required for various heat dissipation parts.

In addition, ΔT (T _L -T _S ) and the heat of fusion (H), which are the difference between the liquidus temperature (T _L ) and the solidus temperature (T _S ) of the aluminum alloy shown in Table 2, are a major factor for evaluating the castability of the alloy. As the index, ΔT (T _L -T _S ), which is the difference between the liquidus temperature (T _L ) and the solidus temperature (T _S ), means that the smaller the castability, the better the castability. The greater the ratio H / ΔT of ΔT (T _L -T _S ), which is the difference between the heat of fusion (H), the liquidus temperature (T _L ) and the solidus temperature (T _S ), the higher the castability. .

The following formula 2 represents the flow distance Lf which is an index for evaluating the casting composition during casting of the alloy. The flow distance Lf is inversely proportional to ΔT (T _L -T _S ), which is the difference between the liquidus temperature (T _L ) and the solidus temperature (T _S ), is proportional to the heat of fusion (H), and the heat of fusion (H) It can be seen that it is proportional to the ratio H / ΔT of ΔT (T _L -T _S ), which is a difference between the liquidus temperature T _L and the solid phase temperature T _S.

[Formula 2]

Where h is the heat transfer coefficient, T _L is the liquid phase temperature, and T _s is the solid phase temperature), where _L f is the fluid flow, ρ is the solid density, H is the heat of fusion, a is the solid diameter,

ΔT (T _L -T _S ), which is a difference between the liquidus temperature (T _L ) and the solidus temperature (T _S ) of the aluminum alloys according to an embodiment of the present invention, is 37 to 60 ° C., which is widely used as an aluminum alloy for die casting. It is a low level compared with ΔT (T _L -T _S ) 74 ° C., which is a difference between the liquidus temperature (T _L ) and the solidus temperature (T _S ) of Comparative Example Alloy 7, which is an Al-Si alloy (ADC 12).

In addition, the heat of fusion (H) of the aluminum alloys according to an embodiment of the present invention is 300 ~ 332 J / g, the heat of fusion of Comparative Example Alloy 7 which is Al-Si alloy (ADC 12) widely used as an aluminum alloy for die casting ( H) almost the same level compared to 311J / g.

In addition, the flow distance Lf, which is an index for evaluating castability, is H /, which is a ratio of ΔT (T _L -T _S ), which is a difference between the heat of melting (H), the liquidus temperature (T _L ), and the solidus temperature (T _S ). From the results of evaluating H / ΔT in proportion to ΔT, the H / ΔT of the aluminum alloys according to the embodiment of the present invention is 5.37 to 8.97 J / g ° C., which is widely used as an aluminum alloy for die casting. It is a high level compared with 4.20 J / g degreeC which is H / (DELTA) T of the comparative example alloy 7 which is an alloy (ADC12).

In other words, ΔT (T _L -T _S ), which is the difference between the heat of melting (H), the liquidus temperature (T _L ) and the solidus temperature (T _S ), which affects the flow distance Lf, which is an index for evaluating castability, and from the ratio of a result of evaluating the H / △ T of the heat of fusion (H) and the liquidus temperature (T _L) and the △ T (T _L -T _S) the difference between solidus temperature (T _S), the embodiment of the present invention Aluminum alloys according to the present invention have an equivalent level of castability as compared to Al-Si alloys widely used in conventional die casting.

Comparative Example 8 has a copper content of 2.6% by weight, which is higher than the embodiments of the present invention. As a result, the thermal conductivity is 154 W / mK, which is lower than the embodiments of the present invention.

Comparative Example 9 has a high magnesium content of 2.2% by weight compared to the embodiments of the present invention. As a result, the thermal conductivity is 138 W / mK, which is lower than the embodiments of the present invention.

Table 3 below shows the tensile test results of tensile specimens made from each alloy and each alloy according to the comparative example of the present invention.

Alloy (wt%) Cu Mg Fe Si Al The tensile strength
(MPa) Yield strength
(MPa) Elongation
(%) Example One 1.01 0.52 0.59 - honey. 120 93 7 2 0.91 1.08 0.55 - honey. 134 96 13 3 1.37 0.51 0.62 - honey. 146 98 14 4 1.34 1.07 0.59 - honey. 172 131 15 5 1.90 0.56 0.62 - honey. 149 113 10 6 1.86 1.07 0.60 - honey. 177 126 11 Comparative Example 7 0.92 0.21 0.97 10.20 honey. 134 120 3 8 2.6 0.5 0.7 - honey. 295 165 27 9 0.1 2.2 0.4 - honey. 195 90 25 10 0.4 1.0 0.7 - honey. 110 50 25

As confirmed in Table 3, the alloys according to Examples 1 to 6 of the present invention, the alloy of Example 1 compared to the conventional Al-Si alloy (ADC 12, Comparative Example 7) widely used as an aluminum alloy for die casting Except for the tensile strength of 134 ~ 177MPa equivalent or above.

Comparative Example 10 has a copper content of 0.4 wt% lower than that of the embodiments of the present invention. As a result, the thermal conductivity is 180 W / mK, which is higher than the embodiments of the present invention, but the tensile strength is 110 MPa. The tensile strength is lower than that of the

Accordingly, the aluminum alloy according to the embodiment of the present invention can be suitably used as a die-casting aluminum material for heat dissipation parts that require a certain level of mechanical strength and excellent thermal conductivity along with castability of die casting.

Claims (7)

Die-casting aluminum alloy containing 0.8-2.5% by weight of copper (Cu), 0.5-1.5% by weight of magnesium (Mg) and 0.5-1.0% by weight of iron (Fe), with the remainder being aluminum (Al) and unavoidable impurities. The method of claim 1,
Wherein the aluminum alloy has a thermal conductivity of 160 W / mK or more. The method of claim 1,
The tensile strength of the aluminum alloy is die casting aluminum alloy, characterized in that more than 120MPa. The method of claim 1,
The difference between the liquidus temperature (T _L ) and the solidus temperature (T _S ) of the aluminum alloy is 60 ℃ or less and the heat of fusion (H) is die casting aluminum alloy, characterized in that more than 300J / g. The method of claim 1,
The aluminum alloy has a H / ΔT ratio of ΔT (T _L -T _S ), which is a difference between the heat of fusion (H), the liquidus temperature (T _L ), and the solid phase temperature (T _S ), is 5.3 J / g ° C. or more. Die casting aluminum alloy, characterized in that. The method of claim 1,
The copper (Cu) is an aluminum alloy for die casting, characterized in that 1.2 to 2.5% by weight. The method of claim 1,
The thermal conductivity of the aluminum alloy is 170W / mK or more, the tensile strength is die casting aluminum alloy, characterized in that more than 145MPa.