KR101984707B1 - Aluminum alloy for high strength die casting excellent in corrosion resistance and thermal conductivity and manufacturing method of aluminum alloy casting using the same - Google Patents

Abstract

The present invention relates to an aluminum alloy for high strength die casting with improved corrosion resistance and thermal conductivity, which comprises: 5.5-8 wt% of silicon (Si); 0.1-0.5 wt% of iron (Fe); 2.0-2.5 wt% of magnesium (Mg); 0.5-1.0 wt% of nickel (Ni); 0.3-0.5 wt% of titanium (Ti); and the remainder consisting of aluminum (AI).

Description

TECHNICAL FIELD The present invention relates to an aluminum alloy for high-strength die casting having excellent corrosion resistance and thermal conductivity, and a method for manufacturing an aluminum alloy casting using the same.

The present invention relates to an aluminum alloy for die casting, a method of manufacturing the same, and a method of manufacturing a casting using the same. More specifically, the present invention provides excellent corrosion resistance and heat dissipation, high thermal conductivity, tensile strength and yield strength, A1 The present invention relates to an aluminum alloy for high-strength die casting excellent in corrosion resistance and thermal conductivity, which is easy to manufacture for electronic devices and automobile parts, regardless of its structure, and a method for manufacturing the same and a method for manufacturing an aluminum alloy casting using the same.

There is usually a plastic working method in which an aluminum plate material is pressed into a desired shape by a method of manufacturing a product by aluminum and a die casting method in which aluminum melt is injected into a metal die machined into a product shape to manufacture the same casting die.

The products produced by the die casting method have advantages of accurate dimensions and are widely used in automobile or airplane parts, electronic devices, and optical devices requiring relatively complicated designs. As the products become more sophisticated, Corrosion resistance, abrasion resistance, high strength, thermal conductivity, and the like are required in addition to lightweight properties.

ALDC12, a typical aluminum-based alloy used for such a die casting alloy, and AZ91D, a magnesium-based alloy. The ALDC12 alloy has a yield strength of 165 MPa and a tensile strength of 331 MPa, while the AZ91D alloy has a lower yield strength of 150 MPa and a tensile strength of 230 MPa. These commercial die casting alloys are difficult to apply to slimmer products that require high strength, such as today's smartphone or tablet cases.

The ZA27 alloy, which is a zinc alloy, has a yield strength of 365 MPa and a tensile strength of 426 MPa, which is excellent in strength but has a specific gravity of 5 g / cc, which is heavier than aluminum alloys and has a light weight limit.

In recent years, Korean Patent Registration No. 1133103 (entitled "High Strength Aluminum Alloy for Die Casting") has been proposed to solve such a problem. The proposed aluminum alloy improves the strength by adding zinc (Zn), magnesium (Mg), copper (Cu), zirconium (Zr) and titanium (Ti) to the aluminum base. However, since the alloy needs aging treatment at 120 캜 for more than 24 hours, not only the productivity is lowered but also there is a problem that the alloy melt injected into the mold at a high speed is stuck to the inner wall of the mold.

As another example, Korean Patent Laid-Open Publication No. 2012-0129458 (entitled "High Strength Die Cast Aluminum Alloy for Thin-walled Products") is proposed. The proposed aluminum alloy is made by adding magnesium (Mg), silicon (Si), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn) and titanium The moldability is also improved by reducing the stickiness of melts and molds. However, the above alloy has a weak corrosion resistance and has a disadvantage that its surface is oxidized by moisture or moisture and corroded.

Korean Patent Registration No. 1133103 (entitled "High Strength Aluminum Alloy for Die Casting) Korean Patent Laid-Open Publication No. 2012-0129458 (Name of invention: high-strength die-cast aluminum alloy for thin-walled products)

Accordingly, it is an object of the present invention to provide a high strength aluminum alloy for high-strength die casting which has both high strength and high corrosion resistance and high thermal conductivity at the same time, And a method for manufacturing an aluminum alloy casting using the same.

In order to attain the above object, one aspect of the present invention relates to an aluminum alloy for high-strength die casting excellent in corrosion resistance and thermal conductivity, wherein the aluminum alloy according to the present invention comprises 5.5 to 8% by weight of silicon (Si) (Ni), 0.3 to 0.5% by weight based on the total weight of titanium (Ti), and the balance aluminum (Fe), 0.5 to 2.0 wt% (Al).

The aluminum alloy according to the present invention has a tensile strength of 340 to 360 MPa and a thermal conductivity of 170 to 190 W / mK.

Another aspect of the present invention relates to a method for producing an aluminum alloy for high-strength die casting having excellent corrosion resistance and thermal conductivity, which comprises 5.5 to 8 wt% of silicon (Si), 0.1 to 0.5 wt% of iron (Fe) (Mg), 0.5 to 1.0% by weight based on the total weight of nickel (Ni), 0.3 to 0.5% by weight based on the total weight of titanium (Ti) and the balance aluminum (Al) ; A second step of heating the prepared aluminum (Al) to 700-750 占 폚 and dissolving, and then raising the temperature to 800-850 占 폚; A third step of adding silicon (Si) to the melt of the second step and then raising the temperature to 900 to 1000 占 폚; A fourth step of adding iron (Fe), nickel (Ni), and titanium (Ti) to the mixture of the third step and heating the mixture for 4 to 5 hours; Heating the mixture in the fourth step to 700 to 750 ° C., and adding magnesium (Mg) to dissolve the mixture; And a sixth step of removing the impurities from the mixture of the fifth step and then tapping the mixture into an ingot to complete the alloy.

In this case, it is preferable that the second to sixth steps of the present invention further include a step of analyzing and calibrating components of the mixture.

In the sixth step of the present invention, it is preferable to inject argon or nitrogen gas into the lower part of the mixture to float impurities caused by bubbling and to remove impurities floating on the surface.

Further, in the sixth step of the present invention, it is preferable to further carry out a filtering process of filtering impurities into a tap outlet and a tapping channel during tapping of the mixture.

Another aspect of the present invention relates to a method of manufacturing an aluminum alloy casting for high-strength die casting excellent in corrosion resistance and thermal conductivity, which comprises 5.5 to 8 wt% silicon (Si), 0.1 to 0.5 wt% (Ti), and the balance aluminum (Al), in an amount of 0.5 to 1.0 wt.% Based on the total weight of the composition, 2.0 to 2.5 wt.% Of magnesium, Preparing an alloy; And dissolving the aluminum alloy, and injecting the melted alloy melt into a die casting mold to produce a casting.

The cast product manufactured by the present invention is preferably an electronic device part or an automobile part.

The castings produced by the present invention can be of the thin type with a thickness (T) of 0.36 mm or less.

It should be understood, however, that the terminology or words of the present specification and claims should not be construed in an ordinary sense or in a dictionary, and that the inventors shall not be limited to the concept of a term It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be properly defined. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It is to be understood that equivalents and modifications are possible.

As described above, the present invention provides the following effects.

First, the oxide layer on the surface is formed stably and densely and has excellent corrosion resistance in a brine environment and water or atmospheric conditions, thereby improving the service life of electronic products and automobile parts.

Second, since the heat conduction characteristic of 170 W / m · K or more is excellent, it is possible to ensure the safety and performance of the device by effectively solving the heat generation inside the electronic product.

Third, it can be widely used for automobile parts requiring high safety due to high strength and compactness of products due to its thinness, because it is possible to perform thin molding with a tensile strength of 340 MPa or more and 0.36 t or less.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 and Fig. 2 are flowcharts showing a process for producing an alloy according to the present invention.
3 is a reference diagram showing a melting furnace apparatus for producing an alloy according to the present invention.
4 is a photograph showing an apparatus for measuring the degree of corrosion of an alloy according to the present invention.
5 is a photograph showing a device for measuring electric conductivity of an alloy according to the present invention.

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

One aspect of the present invention relates to an aluminum alloy, which comprises at least one of silicon (Si), iron (Fe), magnesium (Mg), nickel (Ni), titanium (Ti), and the remainder aluminum (Al).

Silicon (Si) improves fluidity and strength, and is preferably contained in the range of 5.5 to 8.0 wt% based on the total weight of the alloy. That is, when the amount of silicon is more than 8.0 wt%, the heat treatment is weak and cracking occurs. When the amount of silicon is less than 5.5 wt%, the original purpose can not be achieved. Therefore, it is most preferable to include 6.75 wt% so as to improve both fluidity and strength and heat treatment.

Iron (Fe) is preferably contained within the range of 0.1 to 0.5% by weight based on the total weight of the alloy to prevent sticking and improve strength. That is, when the iron content exceeds 0.5% by weight, the corrosion resistance is lowered and the precipitate is generated. If the iron content is less than 0.1% by weight, the original purpose can not be achieved. Therefore, it is most preferable that iron is contained in an amount of 0.3% by weight so as to prevent stickiness, to improve strength, and to have corrosion resistance.

Magnesium (Mg) improves corrosion resistance, strength and elongation, and improves lighter weight and machinability, and is preferably contained in the range of 2.0 to 2.5% by weight based on the total weight of the alloy. Magnesium is closely related to the increase in strength. It is bound to silicon (Si) and precipitates into Mg ₂ Si due to aging, thereby determining mechanical properties. Residual silicon remaining after bonding with magnesium is precipitated singly to improve mechanical properties. That is, at least 2.0 wt% of magnesium should be added considering the increase in strength and the thermal conductivity. If the magnesium content exceeds 2.5% by weight, ignition may start and cause bubbles. To prevent this, other gases are used, which can be solved by adjusting the content. In particular, while a disadvantage in workability as in the case of an excess of silicon (Si) as well as the risk of low intensity, the moldability decreases and fall in productivity inhibit the employment of an extra Mg fails to form a Mg ₂ Si Mg ₂ Si So that the strength can be lowered.

At this time, magnesium (Mg) can rapidly form an oxide layer (MgO) on the surface of the product, and such an oxide layer (MgO) acts as a coating film on the surface to improve corrosion resistance.

Nickel (Ni) improves corrosion resistance and is preferably contained in the range of 0.5 to 1.0 wt% based on the total weight of the alloy. Here, even if nickel is contained in an amount exceeding 1.0% by weight, the corrosion resistance is not remarkably improved, and if it is less than 0.5% by weight, the original purpose can not be achieved. Therefore, if 0.75 wt% of nickel is included, corrosion resistance and harmfulness can be suitably satisfied.

Titanium (Ti) improves the formability, corrosion resistance and strength through refinement of crystal grains, and is preferably contained in the range of 0.3 to 0.5 wt% based on the total weight of the alloy. That is, when the amount of titanium exceeds 0.5% by weight, the flow of the molten metal is lowered to promote the defect, and if it is less than 0.3% by weight, the original purpose can not be achieved. Therefore, it is most appropriate to include 0.4 wt% of titanium so as to improve moldability, corrosion resistance and strength.

Aluminum alloys composed of these components and contents have a tensile strength of 340 to 360 MPa and a thermal conductivity of 170 to 190 W / mK, as well as high corrosion resistance.

Another aspect of the present invention is a method for manufacturing an aluminum alloy for high-strength die casting, which has excellent corrosion resistance and thermal conductivity through the first step (S10) to the sixth step (S60) as shown in FIG. (Si), 0.1 to 0.5 wt% of iron (Fe) based on the total weight, 2.0 to 2.5 wt% of magnesium (Mg) based on the total weight, 0.5 to 1.0 wt% of nickel (Ni), 0.3 to 0.5 wt% of titanium (Ti), and the balance of aluminum (Al) based on the total weight (first step S10).

(Si), 0.3 wt% iron (Fe), 2.25 wt% magnesium (Mg), 0.75 wt% nickel (Ni) based on the total weight, 0.4 wt% titanium (Ti) and the rest aluminum (Al).

Then, the prepared aluminum (Al) is melted by heating to 700 to 750 ° C., and then the temperature is raised to 800 to 850 ° C. (second step (S20)). Then, silicon (Si) is added to the melt of the second step Then, the temperature is raised to 900 to 1000 占 폚 (third step S30).

Next, iron (Fe), nickel (Ni) and titanium (Ti) are added to the mixture of the third step S30 and then heated for 4 to 5 hours (fourth step S40) ) Is heated to 700 to 750 ° C, and then magnesium (Mg) is added to dissolve the mixture (fifth step (S50)).

Finally, the impurities are removed from the mixture in the fifth step (S50), and then the alloy is subjected to a sixth step (S60) in which the ingot is spouted to complete the alloy. Impurities include oxides, carbides, intermetallic compounds, and are largely composed of hydrogen gas and sodium. Hydrogen gas causes deterioration of mechanical properties of the alloy, lowering of moldability and surface bonding such as corrosion or cracking, and sodium lowers fluidity and casting.

That is, as shown in FIG. 3, argon or nitrogen gas is injected into the lower part of the mixture to float impurities caused by bubbling and remove impurities floating on the surface. In addition, the mixture in which the impurities are removed is further subjected to a filtering process of filtering impurities at the tap outlet and the tap flow channel during the tapping process.

Meanwhile, as shown in FIG. 2, the second step (S20) to the sixth step (S60) may be performed by further analyzing and calibrating the components of the mixture. That is, silicon (Si), iron (Fe), nickel (Ni), titanium (Ti), and magnesium (Mg) are added to aluminum as a main component and dissolved Is added.

Another aspect of the present invention is a method for manufacturing a casting product using an aluminum alloy for die casting. (Si), 0.1 to 0.5 wt% of iron (Fe) based on the total weight, 2.0 to 2.5 wt% of magnesium (Mg) based on the total weight, 0.5 to 1.0 wt% of nickel (Ni), 0.3 to 0.5 wt% of titanium (Ti), and the balance of aluminum (Al) based on the total weight.

(Si), 0.3 wt% iron (Fe), 2.25 wt% magnesium (Mg), 0.75 wt% nickel (Ni) based on the total weight, An alloy composed of 0.4 wt% titanium (Ti) and the remaining aluminum (Al) is prepared.

Subsequently, the prepared aluminum alloy is melted and the molten alloy melt is heated to 680 to 750 ° C. and injected into a die casting mold at 75 MPa to complete the casting.

As the metal element is added to the aluminum alloy in the proper composition, the oxide layer of the surface is formed stably and densely so that it has excellent corrosion resistance in the brine environment, water and atmospheric conditions, and exhibits high tensile strength and yield strength. It is possible to manufacture a thin plate-shaped casting product having a thickness (T) of 0.36 mm or less because the molten alloy of the city alloy is not adhered to the inner wall of the mold and the mold filling property of the alloy melt is improved.

Hereinafter, it will be understood that the practical effect of the alloy of the present invention is effective by examining specific examples.

<Preparation of alloy>

The alloys of Examples 1 to 3 and the alloys of Comparative Examples 1 to 3, which are constituted by conventional contents, according to the present invention, are prepared as shown in Table 1 below.

division Al Si Fe Mg Ni Ti Example 1 Honey. 6.0 0.2 2.0 0.6 0.35 Example 2 Honey. 6.5 0.3 2.3 0.8 0.4 Example 3 Honey. 7.5 0.4 2.5 0.9 0.5 Comparative Example 1 Honey. 11 0.8 0.2 0.03 0.08 Comparative Example 2 Honey. 9 0.5 1.5 0.5 0.6 Comparative Example 3 Honey. 6.5 1.0 1.0 0.01 0.2

                                               (Unit: wt%)

<Sample Preparation>

The alloys prepared as shown in Table 1 were prepared as ASTM subsize specimens as shown in Table 2 below.

division Center
Street
(G) width
(w) thickness
(T) Shoulder part
radius
(R) Specimen
Jong Gil
(L) Parallel portion
Length
(A) Bottom
width
(C) Subsize (Plate) 25 6.25 3.05 6 100
More than 32 10

drawing

<Property Test>

The tensile strength and the yield strength of each specimen were measured by using a universal material tester (Instron 5982), and the thermal conductivity was measured according to ASTM E1461. The measurement results are shown in Table 3 below.

division The tensile strength
(MPa) Yield strength
(MPa) Thermal conductivity
(Wm 占)) Example 1 342 243 188 Example 2 354 255 176 Example 3 358 261 172 Comparative Example 1 252 170 101 Comparative Example 2 278 182 96 Comparative Example 3 233 158 123

As a result of the measurement, the alloys of the examples had a tensile strength of 342 to 358 MPa and were superior to the alloys of the comparative examples, and the alloys of the examples were also 172 to 188 Wm · K in terms of thermal conductivity as compared with 96 to 123 Wm · K of the alloys of the comparative examples Respectively.

<Corrosion resistance test>

The specimens of the above-described Examples and Comparative Examples 1 to 3 were sprayed on the surface in accordance with KS D 9502, a salt spray test method without surface treatment, under the following conditions.

- NaCl (Sodium Chloride): 99.5%

- Brine concentration: 5%

- Water: Deionized water and distilled water

- Test temperature: 35 ° C ± 1 ° C

- Spray pH (35 ° C): pH 6.5 to 7.2

- Spraying pressure: 0.07 ~ 0.17 MPa

- Spray method: continuous spray

- Spray time: 24h

As a result of observing the specimen under these conditions visually, it was confirmed that the alloy color of the example was clear and the surface was finer than the alloy of the comparative example. For the electrochemical experiment, the reference electrode was silver / silver chloride (Ag / AgCl) using a ZIVE: SP1 measuring instrument shown in FIG. 4 and the counter electrode was a high purity graphite electrode at a scanning rate of 2 mV The average corrosion potential, the average corrosion current density, and the average corrosion rate were measured for the specimens of Examples and Comparative Examples by performing V polarization based on the anode equilibrium potential. For the measurement of the electrical conductivity, ASTM E 1004 standard measurement was performed on the specimens of Examples and Comparative Examples using the Fischer: SMP-350 measuring instrument shown in FIG. 5 by a 60 kHz vortex method. The measurement results are shown in Table 4 below.

division Electrical conductivity
(% IACS) Corrosion potential
(Ecorr)
(Ag / AgCl) Current density
(Icorr)
(uA / cm ²⁾ Corrosion rate
(mpy) Example 1 35.2 -0.92 1.68 0.066 Example 2 33.1 -0.98 1.62 0.072 Example 3 30.5 -1.01 1.54 0.079 Comparative Example 1 22.3 -1.22 1.19 0.099 Comparative Example 2 18.2 -1.32 1.03 0.105 Comparative Example 2 25.3 -1.19 1.25 0.094

As a result of the measurement, it was confirmed that the examples were superior to the comparative examples in terms of the electric conductivity. However, the high electrical conductivity means that the resistance to corrosion was small, and the corrosion resistance of the examples was excellent as compared with the comparative examples. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. It is therefore intended that such variations and modifications fall within the scope of the appended claims.

Claims (9)

For high strength aluminum alloy for die casting with excellent corrosion resistance and thermal conductivity:
(Si), 0.1 to 0.5 wt% of iron (Fe) based on the total weight, 2.0 to 2.5 wt% of magnesium, 0.5 to 1.0 wt% of nickel (Ni) ), 0.3 to 0.5% by weight based on the total weight of titanium (Ti), and the balance aluminum (Al). The aluminum alloy according to claim 1, wherein the aluminum alloy has a tensile strength of 340 to 360 MPa and a thermal conductivity of 170 to 190 W / m.K. The aluminum alloy for high strength die casting has excellent corrosion resistance and thermal conductivity. delete delete delete delete A method for producing an aluminum alloy casting for high strength die casting excellent in corrosion resistance and thermal conductivity, comprising:
(Si), 0.1 to 0.5 wt% of iron (Fe) based on the total weight, 2.0 to 2.5 wt% of magnesium, 0.5 to 1.0 wt% of nickel (Ni) ), 0.3 to 0.5% by weight based on the total weight of titanium (Ti) and the balance aluminum (Al); And
And dissolving the aluminum alloy and injecting the melted alloy melt into a die casting mold to produce a casting product. The method of claim 1, wherein the casting is a high-strength die casting. 8. A method of manufacturing an aluminum alloy casting for high-strength die casting, wherein the casting produced by the method of claim 7 is an electronic device part or an automobile part, which is excellent in corrosion resistance and thermal conductivity. 9. The method of claim 8,
Wherein the cast product has a thickness (T) of 0.36 mm or less, and is excellent in corrosion resistance and thermal conductivity.

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