KR101910470B1 - Aluminum alloy for high strength die casting excellent in corrosion resistance and thermal conductivity, method for manufacturing the same - Google Patents

Abstract

One aspect of the present invention relates to an aluminum alloy for high-strength die casting with excellent corrosion resistance and thermal conductivity, comprising, based on the total weight, 5-7 wt% of silicon (Si); 0.1-1.0 wt% of iron (Fe); 1.5-2.5 wt% of magnesium (Mg); 0.1-1.0 wt% of nickel (Ni); 0.15-0.45 wt% of titanium (Ti); and the remaining amount of aluminum (Al).

Description

TECHNICAL FIELD [0001] 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 the aluminum alloy.

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 is pressed and formed into a desired shape by a method of manufacturing a product with aluminum, and a die casting method in which aluminum casting is injected into a die machined into a product shape to produce the same casting.

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 limitation in weight reduction.

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 one aspect of the present invention, there is provided an aluminum alloy for high-strength die casting excellent in corrosion resistance and thermal conductivity, comprising 5 to 7% by weight of silicon (Si), 0.1 to 1.0% (Mg), 0.1 to 1.0 wt% of nickel (Ni), 0.15 to 0.45 wt% of titanium (Ti), and the balance of aluminum (Al) based on the total weight, preferably 1.5 to 2.5 wt% Do.

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The aluminum alloy according to the present invention has a tensile strength of 300 to 320 MPa and a thermal conductivity of 140 to 160 W / m.K.

Another aspect of the present invention relates to a method for producing an aluminum alloy for high-strength die casting excellent in corrosion resistance and thermal conductivity, which comprises 5 to 7 wt% of silicon (Si), 0.1 to 1.0 wt% of iron (Fe) (Ni), 0.15 to 0.45% by weight of titanium (Ti), and the balance aluminum (Al) are prepared in an amount of 1.5 to 2.5% by weight based on the total weight, ; 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 to 7 wt% silicon (Si), 0.1 to 1.0 wt% (Ti), and the balance aluminum (Al), in an amount of 0.1 to 1.0 wt% based on the total weight, 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 cast product produced by the present invention has a thickness (T) of 0.38 mm or less and can be of a thin type.

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.

Secondly, since the heat conduction characteristic of 140 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, because it is possible to form thinner than 0.38t while having a tensile strength of 300MPa or more, it can be widely used in automobile parts requiring safety by high strength and compactness of product by thin type.

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 may be included in the range of 5.0 wt.% To 7.0 wt.% Based on the total weight of the alloy. That is, when the amount of silicon exceeds 7.0 weight%, the heat treatment is weak and cracking occurs. When the amount of silicon is less than 5.0 weight%, the original purpose can not be achieved. Therefore, it is most preferable to include 6.0 wt% so as to improve both fluidity and strength and heat treatment.

Iron (Fe) is preferably contained within the range of 0.1 wt% to 1.0 wt% with respect to the total weight of the alloy to prevent sticking and improve strength. That is, when the iron content exceeds 1.0% by weight, the corrosion resistance is lowered and the precipitates are formed. If the iron content is less than 0.01% by weight, the original purpose can not be achieved. Therefore, it is most preferable that iron is contained in an amount of 0.5% by weight so as to prevent stickiness, to improve strength and corrosion resistance.

Magnesium (Mg) improves corrosion resistance, strength and elongation, and improves lighter weight and machinability. It is preferably contained in the range of 1.5 wt% to 2.5 wt% 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, which determines mechanical properties. Residual silicon remaining after magnesium bonding is precipitated singly to improve mechanical properties. That is, if the magnesium content is less than 2.0 wt%, the effect of increasing the strength is insufficient. Since the thermal conductivity must be considered at the same time, a tensile strength of 300 MPa or more can be achieved at least 1.5 wt%.

Conversely, if the magnesium content exceeds 2.5% by weight, ignition may start and cause bubbles. To prevent this, another gas is 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 the corrosion resistance and is preferably contained in the range of 0.1 wt% 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 0.1% by weight, the original purpose can not be achieved. Therefore, if the nickel content is 0.5% by weight, corrosion resistance and harmfulness can be suitably satisfied.

Titanium (Ti) improves moldability, corrosion resistance and strength through refinement of crystal grains and is preferably contained in the range of 0.15 wt% to 0.45 wt% based on the total weight of the alloy. That is, when the amount of titanium exceeds 0.45 wt%, the flow of the molten metal is lowered to promote the failure, and if it is less than 0.15 wt%, the original purpose can not be achieved. Therefore, it is most appropriate to include 0.15% by weight of titanium so as to improve moldability, corrosion resistance and strength.

Aluminum alloys composed of these components and contents have a tensile strength of 300 to 320 MPa and a thermal conductivity of 140 to 160 W / m.K, 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 1.0 wt% of iron (Fe) based on the total weight, 1.5 to 2.5 wt% of magnesium (Mg) based on the total weight, 0.1 to 1.0 wt% of nickel (Ni), 0.15 to 0.45 wt% titanium (Ti), and the balance aluminum (Al), based on the total weight.

(Si), 0.5 wt% iron (Fe), 1.5 wt% magnesium (Mg), 0.5 wt% nickel (Ni), based on the total weight, Prepare materials consisting of 0.15 wt% titanium (Ti) and the balance aluminum (Al).

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

(Fe), nickel (Ni) and titanium (Ti) are added to the mixture of the third step S30 and then the fourth step S40 of heating the mixture for 4 to 5 hours. In the fourth step S40, Is heated to 700 to 750 DEG C, and then magnesium (Mg) is added to dissolve the mixture (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 1.0 wt% of iron (Fe) based on the total weight, 1.5 to 2.5 wt% of magnesium (Mg) based on the total weight, 0.1 to 1.0 wt% of nickel (Ni), 0.15 to 0.45 wt% of titanium (Ti) and the balance aluminum (Al) based on the total weight.

(Si), 0.5 wt% iron (Fe), 1.5 wt% magnesium (Mg), 0.5 wt% nickel (Ni), based on the total weight, An alloy composed of 0.15 wt% titanium (Ti) and the balance 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 0.38 mm or less by improving the mold filling property of the molten alloy without being adhered to the inner wall of the mold.

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 Example 1 and Comparative Example 1 (ADC12.1) and Comparative Example 2 (S33N), which are constituted by conventional contents, are prepared as shown in Table 1 below.

division Al Si Fe Mg Ni Ti Example 1 Honey. 6 0.5 1.5 0.5 0.15 Comparative Example 1 Honey. 11 0.8 0.2 0.03 0.08 Comparative Example 2 Honey. 6.5 0.2 1.4 0.08 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 1 320 233 140 Comparative Example 1 200 160 96 Comparative Example 2 320 230 124

As a result of measurement, it was found that the tensile strengths of Examples 1 and 2 were 300 MPa or more, respectively, but the thermal conductivity of Example 1 was significantly higher than that of Comparative Example 2 having 140 Wm · K and 124 Wm · K I can see that.

<Corrosion resistance test>

First, the prepared specimens were sprayed on the surface under the following conditions according to KS D 9502, a salt spray test method, without surface treatment.

- 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

The specimens under these conditions were visually observed as shown in Table 4 below. And electrochemical experimental test piece, and the electrical conductivity experimental test piece base material ² after 9cm area was washed after the polishing and then subjected to mounting to SiC abrasives # 2000 times with distilled water exposure was used as a dry test piece. Using the ZIVE: SP1 measurement equipment shown in FIG. 4, the reference electrode was silver / silver chloride (Ag / AgCl), the counter electrode was a high purity graphite electrode, and V The average corrosion potential, average corrosion current density and average corrosion rate were measured by polarizing. Using the Fischer: SMP-350 measuring instrument shown in FIG. 5, the electrical conductivity was measured by ASTM E 1004 standard measurement on the exposed surface of the material by a 60 kHz vortex method. The measurement results are shown in Table 5 below.

Example 1 Comparative Example 1 Comparative Example 2

As a result of observation, it can be confirmed that the hue of Example 1 is clear and the surface is dense as compared with Comparative Example 1 or Comparative Example 2. [

division Electrical conductivity
(% IACS) Corrosion potential
(Ecorr)
(Ag / AgCl) Current density
(Icorr)
(uA / cm ²⁾ Corrosion rate
(mpy) Example 1 30 -1.01 1.51 0.072 Comparative Example 1 22.1 -1.69 1.47 0.22 Comparative Example 2 25.2 -1.09 1.17 0.08

As a result of the measurement, it can be seen that the corrosion rates of Examples 1 and 2 are similar but the electric conductivity is significantly better than that of Comparative Example 2, which is 30 to 25.2 in terms of electric conductivity. That is, the fact that the electrical conductivity is high means that the resistance due to corrosion is small, and the fact that the embodiment is high as compared with the comparative example is a disadvantage that the corrosion resistance is excellent.

&Lt; Magnesium component ratio test &

Magnesium (Mg) influences the corrosion resistance, strength and elongation enhancement. Especially, it is an important element which binds with silicon (Si) in relation to increase in strength and determines mechanical properties. The tensile strength, yield strength and thermal conductivity of the specimens were measured by adjusting only the composition ratio of magnesium (Mg). The electrical conductivity, corrosion potential, current density and corrosion rate were also measured as shown in Table 7 below.

division The tensile strength
(MPa) Yield strength
(MPa) Thermal conductivity
(Wm 占)) Example 1
Mg (1.5%) 320 233 140 Example 2
Mg (2.5%) 318 237 125 Example 3
Mg (3.5%) 315 244 120

As a result, the tensile strength and the thermal conductivity were improved as the weight ratio of magnesium (Mg) was decreased, but the yield strength was lowered. Conversely, the higher the weight ratio, the lower the tensile strength and thermal conductivity and the higher the yield strength.

division Electrical conductivity
(% IACS) Corrosion potential
(Ecorr)
(Ag / AgCl) Current density
(Icorr)
(uA / cm ²⁾ Corrosion rate
(mpy) Example 1
Mg (1.5%) 30 -1.01 1.51 0.072 Example 2
Mg (2.5%) 24.5 -1.04 1.83 0.087 Example 3
Mg (3.5%) 24.5 -1.01 1.82 0.068

As a result of the measurement, the lower the weight ratio of magnesium (Mg), the lower the corrosion rate and the higher the electric conduction, and the higher the weight ratio, the higher the corrosion rate and the lower the electric conductivity.

<Experimental Investigation>

As a result, referring to Table 6 and Table 7, it can be confirmed that magnesium (Mg) is an important factor for simultaneously realizing the high strength, high corrosion resistance and high thermal conductivity of the present invention. That is, when the weight ratio of titanium (Ti) is 1.5 wt% or less, the tensile strength is lowered. When the weight ratio is 2.5% or more, the thermal conductivity is lowered. Is 1.5 to 2.5% by weight, preferably 1.5% by weight.

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 as defined by the appended claims. It is therefore intended that such variations and modifications fall within the scope of the appended claims.

Claims (15)

For high strength aluminum alloy for die casting with excellent corrosion resistance and thermal conductivity:
(Si), 0.1 to 1.0 wt% of iron (Fe), 1.5 to 2.5 wt% of magnesium (Mg), 0.1 to 1.0 wt% of nickel (Ni) based on the total weight, ) Having a tensile strength of 300 to 320 MPa and a thermal conductivity of 140 to 160 W / mK, which is composed of 0.15 to 0.45% by weight of titanium (Ti) and the balance of aluminum (Al) Aluminum alloy for. delete A method of manufacturing an aluminum alloy for high-strength die casting excellent in corrosion resistance and thermal conductivity, comprising:
(Si), 0.1 to 1.0 wt% of iron (Fe), 1.5 to 2.5 wt% of magnesium (Mg), 0.1 to 1.0 wt% of nickel (Ni) based on the total weight, ), 0.15 to 0.45% 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
And a sixth step of removing the impurities from the mixture in the fifth step and then adding the ingot to an ingot to complete the alloy. [Claim 6] The method of claim 1, wherein the aluminum alloy has a high corrosion resistance and a high thermal conductivity. The method of claim 3,
Wherein the second to sixth steps further include a step of analyzing and calibrating components of the mixture, respectively. The method of claim 3,
The sixth step is a method for manufacturing an aluminum alloy for high strength die casting having excellent corrosion resistance and thermal conductivity, characterized by injecting argon or nitrogen gas into the lower part of the mixture to float impurities caused by bubbling and removing impurities floating on the surface . The method of claim 3,
Wherein the sixth step further comprises a filtering step of filtering impurities in the tap outlet and the tapping channel during tapping of the mixture. delete delete delete delete delete delete delete delete delete

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