KR102553711B1 - Aluminum die casting alloy having excellent formability, corrosion resistance, heat conductivity, strength - Google Patents

Abstract

The present invention is an aluminum alloy for die casting having formability, corrosion resistance, high thermal conductivity and strength. The aluminum die-casting alloy of the present invention has sufficient fluidity during molten metal, so it is easy to manufacture by die-casting. In addition, the die-casting product manufactured from the present invention has corrosion resistance and excellent strength as well as thermal conductivity, so it can be widely used as a material for electronic products or automobile parts that require resistance to salt water, load or stress, and heat dissipation characteristics. .

Description

Aluminum die casting alloy having excellent formability, corrosion resistance, heat conductivity, strength}

The present invention relates to an aluminum die-casting alloy, and more particularly, to an aluminum die-casting alloy having formability, corrosion resistance, high thermal conductivity and strength.

As the functions of various products such as eco-friendly cars, smart phones, and LED lighting fixtures are advanced, various performances of parts and materials used therein are required. Representatively, there are moldability that can be rapidly manufactured in large quantities, lightness that can further reduce product weight, strength that can withstand loads or external impacts, and corrosion resistance that does not corrode even in salt water environments.

Aluminum alloy is widely used as a material that satisfies these various performances. Aluminum is lightweight, easy to cast, well alloyed with other metals, easily processed at room temperature and high temperature, and has excellent electrical and thermal conductivity. In particular, in recent years, aluminum alloys in which aluminum is mixed with other metals have been widely used to improve fuel efficiency or reduce weight of automobiles and electronic products.

For example, Korean Patent Publication No. 10-2020-0072618 (aluminum alloy with excellent strength and abrasion resistance) and Patent Registration No. 10-1727852 (high thermal conductivity aluminum alloy with excellent castability) disclose these technologies, but these technologies are aluminum alloys. It only satisfies one or more physical properties such as strength, castability, and thermal conductivity.

On the other hand, die casting, a manufacturing method of aluminum alloy products, can produce products quickly and in large quantities without dimensional errors, and is widely used in automobile parts, electrical devices, optical devices, and measuring instruments that require precision and productivity, making aluminum alloy suitable for die casting. development is required.

Republic of Korea Patent Publication No. 10-2020-0072618 (aluminum alloy with excellent strength and wear resistance) Registered Patent Publication No. 10-1727852 (high thermal conductivity aluminum alloy with excellent castability)

Accordingly, an object of the present invention is to provide an aluminum die-casting alloy that has formability so that it can be formed by die-casting and can simultaneously realize excellent corrosion resistance, high strength, and thermal conductivity.

In order to solve the above technical problem, the present invention is an aluminum die-casting alloy containing silicon (Si), iron (Fe), magnesium (Mg), neodymium (Nd), boron (B) and aluminum (Al) provides

The aluminum die-casting alloy of the present invention contains 4 to 8 wt% silicon (Si), 0.2 to 0.7 wt% iron (Fe), 0.05 to 0.3 wt% magnesium (Mg), 0.05 to 0.3 wt% neodymium (Nd), 0.001 to 0.1 It is composed by mixing boron (B) by weight and aluminum (Al) as the remainder.

At this time, the yield strength of the aluminum die-casting alloy of the present invention is 90 to 105 Mpa, and the tensile strength is 145 to 210 Mpa.

In addition, the thermal conductivity after heat treatment of the aluminum die casting alloy of the present invention is higher than the thermal conductivity before heat treatment by 8 to 9%, and the thermal conductivity after heat treatment is 175 to 185 W/m-k.

At this time, the aluminum die-casting alloy of the present invention is heat treated by heating at 300 ° C. for 3 hours.

The aluminum die-casting alloy according to the present invention has sufficient fluidity during molten metal, so it is easy to manufacture by die-casting, and the die-casting product manufactured therefrom has corrosion resistance and excellent strength as well as thermal conductivity characteristics, so that it has resistance to salt water, load or stress. It can be widely used as a material for electronic products or automobile parts where heat dissipation characteristics are required.

1 is a view showing a spiral mold for measuring the fluidity of molten aluminum alloy in Examples according to the present invention and Comparative Examples.
2 is a photograph showing test pieces manufactured by die-casting aluminum alloys of Examples according to the present invention and Comparative Examples.
3 (a) and (b) are pictures of the surface of the test piece and SEM pictures of FIG. 2 sprayed with salt water.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

This embodiment is provided to more completely explain the present invention to those with average knowledge in the art, and the shape of elements in the drawings, the size of elements, the spacing between elements, etc. are emphasized for clearer explanation. It can be exaggerated or reduced to express.

In addition, when it is determined that the technical features of the present invention may be unnecessarily obscured as matters already obvious to those skilled in the art, such as known functions or known configurations related to the embodiments in principle, the detailed I will omit the explanation.

The present invention is an aluminum alloy for die casting containing silicon (Si), iron (Fe), magnesium (Mg), neodymium (Nd), boron (B) and the remainder aluminum (Al), which has strength, high thermal conductivity and die casting molding It is composed of the above-mentioned 6-membered alloy to satisfy all the properties, and each metal element added will be described in detail below.

First, silicon (Si) is added to improve the formability and strength of the alloy. 4% by weight or more relative to the total weight of the alloy should be added, but if it exceeds 8% by weight, cracking occurs due to heat treatment, so it is reduced to 6% by weight. It is preferable to add

Iron (Fe) is added to prevent stickiness of the alloy and improve strength. Iron (Fe) should be added in an amount of 0.2% by weight or more relative to the total weight of the alloy, but if it exceeds 0.7% by weight, corrosion resistance is lowered and deposits are generated, so it is preferably added in an amount of 0.5% by weight.

Magnesium (Mg) is added to rapidly grow a dense surface oxide layer (MgO) to prevent internal corrosion and improve strength. Excessive addition reduces fluidity and makes it difficult to mold complex-shaped products, so the total weight is 0.05 to 0.5 Added in weight percent.

Neodymium (Nd) is a rare earth metal element that is added to improve the strength of alloys. When added in excess, it combines with magnesium to form a large amount of compound, making the structure coarse, which can impair formability and corrosion resistance. , 0.05 to 0.3% by weight.

Boron (B) is added to promote the precipitation of intermetallic compounds added in the heat treatment step of the aluminum alloy manufacturing process to suppress coarsening of crystal grains to improve the strength of the aluminum alloy and to suppress the decrease in electrical conductivity. . The added boron (B) is added in the range of 0.001 to 0.1% by weight. If the content of boron (B) exceeds 0.1% by weight and is added in excess, intermetallic compounds are excessively generated, and the electrical conductivity of the aluminum alloy is rather deteriorated. can

An aluminum die-casting alloy is produced by heating the metal element composed of the above mixing ratio at 700 to 1,200 ° C. for 4 to 8 hours to completely melt it, and then injecting it into a mold and cooling it. The aluminum die-casting alloy prepared in this way has a yield strength in the range of 90 to 105 Mpa, a tensile strength in the range of 145 to 210 Mpa, and a thermal conductivity in the range of 170 to 185 W/m-k, with excellent strength and high thermal conductivity. are also expressed together. In addition, the manufactured aluminum alloy has an elongation in the range of 7 to 8% and has excellent formability capable of die casting.

Specific examples of the aluminum die-casting alloy prepared according to the present invention will be described below.

<Composition of aluminum alloy molten metal>

With the composition shown in Table 1 below, an aluminum alloy molten metal in which metal elements were mixed and heated to completely melt was prepared.

<Measurement of fluidity of aluminum alloy molten metal>

The fluidity of the aluminum alloy molten metal prepared in Examples and Comparative Examples was measured. To this end, a spiral mold 100 as shown in FIG. 1 was fabricated, and each molten metal was gravity cast to compare the length of flow into the mold until solidification. At this time, the molten metal temperature, amount, and mold preheating temperature were set the same , three or more experiments were conducted for each of the alloys. The fluidity length is the average value of the values obtained in these experiments, and the fluidity length of ALDC12, a commercial aluminum alloy, was calculated as 100, and the relative values of the Examples and Comparative Examples were converted into percentages.

Table 2 below shows the fluidity of the molten metal measured in this way.

As shown in Table 2 above, Examples 1 to 3 and Comparative Examples 2 to 4 all have a fluidity of 80% or more, and there is no significant difference compared to commercial aluminum alloys, whereas Comparative Example 1 has a fluidity of 66% , it was confirmed that the formability was not good. This is presumed to be due to the small amount of silicon (Si) compared to the other examples.

<Manufacture of aluminum alloy die-casting test piece>

Test pieces having a thickness of 3.05 mm, a width of 6.25 mm, and a length of 52 mm as shown in FIG. 2 were produced using the aluminum alloy prepared in Examples and Comparative Examples using a TOYO125 die-casting facility.

<Measurement of corrosion resistance>

For each test piece prepared in Examples and Comparative Examples, corrosion resistance was measured as follows according to KS D 9502, a salt spray test method, without surface treatment.

- Nacl (Sodium Chloride): 99.5%, Samchun Pure Chemical Co., Ltd.

- Saline concentration: 5%

- Water: deionized water and distilled water

- Test temperature: 35℃ ± 1℃

- Spray pH (35℃): pH6.5~7.2

- Spray pressure: 0.07~0.17 MPa

- Spray method: continuous spray

- Spray volume: 1.5 ± 0.5 ml/hr

- Measurement method: 24 hours after spraying, the surface state of 250 μm and the state of the oxide film of 5 μm were observed using a scanning electron microscope along with visual observation, and the results are shown in FIGS. 3 (a) and (b), respectively.

Figure 3 (a) is a photograph of the appearance of the Example and Comparative Example, and 3 (b) is a SEM photograph of the Example and Comparative Example, respectively. While the surface was smooth and not corroded, it was confirmed that the surfaces of Comparative Examples 3 and 4 were corroded. In particular, Comparative Example 4 showed severe corrosion, resulting in increased iron (Fe), neodymium (Nd), and boron ( B) is assumed to be affected.

<Strength measurement>

And, for each test piece prepared in Examples and Comparative Examples, yield, tensile strength, and elongation were measured using a universal testing machine (Instron 5982), respectively. The measured results are shown in Table 3 below.

As shown in Table 3 above, Examples 1 to 3 and Comparative Examples 3 and 4 were all excellent at yield strength of 90 Mpa or more and tensile strength of 145 Mpa or more, but Comparative Examples 1 and 2 had yield strengths of 82,6 and 75.4 Mpa, respectively. , the tensile strength was measured as low as 136.1 and 113.4 Mpa. It is assumed that neodymium (Nd) was not added (Comparative Example 1) and low content of iron (Fe) (Comparative Example 2) affected.

<Measurement of thermal conductivity>

In addition, the thermal conductivity of the specimens of Examples and Comparative Examples was measured before heat treatment and after heating at 300 ° C for 3 hours according to the laser flash method (ASTM E1461) using Netzsch LFA 467 equipment, and the results are shown in Table 4 below. .

As shown in Table 4 above, it can be confirmed that the thermal conductivity of Examples 1 to 3 was 162 to 169 W/m-k before heat treatment, but the thermal conductivity after heating at 300° C. for 3 hours significantly increased to 175 to 185 W/m-k. could In contrast, Comparative Examples 1 and 4 had higher thermal conductivity than Example before heat treatment, but after heating at 300 ° C. for 3 hours, the thermal conductivity was measured as 183 and 179 W / m-k, respectively, and the increase was not greater than that of Example was able to confirm And, Comparative Examples 2 and 3 were not as high as 153 and 155 W/m-k even before heat treatment, and were not as high as 161 and 166 W/m-k even after heating at 300° C. for 3 hours.

As examined through the above tests, it was confirmed that the fluidity of the molten metals of Examples 1 to 3 was not significantly different from that of commercially available aluminum alloys, and thus had sufficient formability to be cast sufficiently during die casting. In addition, the products prepared in Examples 1 to 3 have corrosion resistance that is not corroded even in salt water, high yield strength (90 to 105 Mpa) and tensile strength (145 to 210 Mpa), and especially excellent thermal conductivity after heat treatment (175 to 185 Mpa). W/m-k) was confirmed to be expressed.

As such, the present invention having various physical properties has sufficient fluidity when molten metal is used, so it is easy to manufacture by die casting. In addition, the die-casting product manufactured from the present invention has corrosion resistance and excellent strength as well as thermal conductivity, so it can be widely used as a material for electronic products or automobile parts that require resistance to salt water, load or stress, and heat dissipation characteristics. .

The present invention described above is not limited to the described embodiments, and it is obvious to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, such variations or modifications should fall within the scope of the claims of the present invention.

Claims (6)

Based on the total weight, 4 to 8 wt% silicon (Si), 0.2 to 0.7 wt% iron (Fe), 0.05 to 0.3 wt% magnesium (Mg), 0.05 to 0.3 wt% neodymium (Nd), 0.001 to 0.1 wt% boron (B) and the remainder aluminum (Al) are mixed and composed,
The yield strength before heat treatment is 90 to 105 Mpa, the tensile strength before heat treatment is 145 to 210 Mpa,
The thermal conductivity after the heat treatment is 8 to 9% higher than the thermal conductivity before the heat treatment,
The heat treatment is an aluminum die-casting alloy, characterized in that heating at 300 ℃ for 3 hours. delete delete delete According to claim 1,
The aluminum die-casting alloy, characterized in that the thermal conductivity after heat treatment of the aluminum die-casting alloy is 175 ~ 185 W / mk. delete

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