KR102264501B1 - Aluminium alloy for die-casting capable of forming high quality oxide film by anodizing treatment - Google Patents

Abstract

The present invention relates to an aluminum alloy for die casting which can be anodized to manufacture a product having an excellent surface shape. The aluminum alloy for die casting according to the present invention includes 2.5 to 7 wt% of manganese (Mn), and 1 to 3 wt% of zinc (Zn), 0.3 to 2 wt% of zirconium (Zr), 0.1 to 2 wt% of iron (Fe), 0.05 to 0.5 wt% of strontium (Sr), 0.05 to 0.5 wt% of titanium (Ti), and the balance aluminum (Al) and unavoidable impurities.

Description

Aluminum alloy for die-casting capable of anodizing {Aluminum alloy for die-casting capable of forming high quality oxide film by anodizing treatment}

The present invention relates to an aluminum alloy for die casting capable of producing a product having an excellent surface appearance by anodizing.

Aluminum alloy is a highly durable material with light weight and excellent strength, and is widely used as a material for manufacturing automobile parts and cases of electronic products.

In general, aluminum alloys can be classified into alloys for casting and alloys for processing according to the manufacturing method of the product, and alloys for casting are formed by sand casting, mold casting, high pressure casting, die casting, special casting, etc., and aluminum for processing The alloy is formed by methods such as rolling, extrusion, forging, and pressing, and an anodizing film is formed on the surface of the molded product through anodizing treatment, so that it is not damaged even after long-term use. manufactured and used.

Recently, die casting using aluminum alloys for die casting such as Al-Si alloys such as ALDC 3 types, ALDC 10 types, and ALDC 12 types, and Al-Mg alloys such as ALDC 5 types or ALDC 6 types with excellent castability. It manufactures products by this method, and the work to improve the commercial value through anodizing (electro-oxidation film treatment) process for surface modification and treatment of various colors is emerging as a big issue recently.

Specifically, the anodizing process of aluminum alloy proceeds through anodization to form an oxide film with high adhesion to the base metal by oxygen generated from the anode, and the oxide film has corrosion resistance, abrasion resistance, adhesion to the base metal, long-term durability Due to the advantage of being able to obtain a beautiful decorative appearance through a low-cost coloring process that encapsulates and seals a dye in the characteristic porous layer of the excellent oxide film, it is particularly useful in relation to aluminum and its alloys. usage is increasing.

However, when an anodizing process is applied to a product formed by die casting to manufacture a product, flow marks, cracks, etc. occur due to changes in alloy composition, resulting in deterioration in appearance quality, and other problems such as breaking strength, etc. There is a problem in that it is difficult to mass-produce as an actual product due to the deterioration of characteristics, and various studies are being conducted on methods to compensate for this problem.

For example, Document 1, Korean Patent No. 10-1743234, is an aluminum alloy for die casting that enables film formation by anodizing, copper (Cu) 0.03 to 0.8 wt%, zinc (Zn) 0.7 to 4.5 wt% , nickel (Ni) 0.1 to 3.5 wt%, iron (Fe) 0.3 to 5.5 wt%, manganese (Mn) 1.5 to 5.5 wt%, titanium (Ti) 0.02 to 3.0 wt%, zirconium (Zr) 0.3 to 4.5 wt% , magnesium (Mg) 0.4 to 1.3 wt%, cadmium (Cd) 0.3 to 1.7 wt%, beryllium (Br) 0.5 to 3.0 wt%, tin (Sn) 0.03 to 3.5 wt%, lead (Pb) 0.03 to 3.5 wt% , boron (B) 0.1 to 4.0 wt%, cobalt (Co) 0.3 to 3.5 wt%, iridium (Ir) 0.05 to 3.0 wt%, chromium (Cr) 0.07 to 3.0 wt%, palladium (Pd) 0.03 to 0.9 wt% , and 0.1 to 3.0 wt% of silicon (Si); The content of the aluminum alloy for die casting in which the balance is composed of a component ratio of aluminum (Al) has been disclosed.

However, the aluminum alloy disclosed in Document 1 has a problem that its use is limited as it essentially contains harmful elements such as nickel, lead, beryllium, cobalt, and cadmium.

As another example, Korean Patent Registration No. 10-2015-0040631, which is document 2, relates to an aluminum alloy for die-casting, a metal case of a portable electric device, and a method for manufacturing the same, Mn 1.95 to 4.10 wt%, Zn 0.1 to 2.0 wt. %, Zr 0.3 to 0.8% by weight, Ti 0.03 to 0.09% by weight, unavoidable impurities, and the content of the aluminum alloy for die-casting, characterized in that it contains the remainder aluminum has been disclosed.

However, the aluminum alloy as disclosed in Document 2 has the advantage of being able to secure fluidity for die casting without adding silicon, but there is a risk of burning (burning) phenomenon in which the aluminum alloy sticks to the inside of the mold in the production mold, There is a disadvantage that the appearance quality is low due to the uneven thickness of the oxide film produced by anodizing, so it is necessary to study a method to compensate for this.

Korean Patent Registration No. 10-1743234 (Announcement Date: 2017.06.02) Korea Patent Publication No. 10-2015-0040631 (published date: 2015.04.15) Korea Patent Publication No. 10-2011-0038357 (published on: April 14, 2011) Korean Patent Publication No. 10-1997-0065754 (published on October 13, 1997)

The present invention has been devised to solve the problems of the prior art as described above, and contains a high content of manganese (Mn) of 2.5 wt% or more to greatly improve the fluidity of the alloy to facilitate the die-casting casting process and prevent burning It is an object of the present invention to provide technical content regarding an aluminum alloy for die-casting, which not only prevents it, but also forms a thick oxide film having a uniform thickness and excellent appearance quality by anodizing.

In addition, in the present invention, silicon (Si) and copper (Cu) are intentionally included, except when they are included as unavoidable impurities and harmful elements such as nickel (Ni), lead (Pb), beryllium (Br), and cobalt (Co). This is to provide technical details about an aluminum alloy for die casting having a surface with excellent gloss by anodizing.

The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned are clearly understood by those of ordinary skill in the art to which the present invention belongs from the following description it could be

In order to achieve the technical problem as described above, the present invention is manganese (Mn) 2.5 to 7% by weight, zinc (Zn) 1 to 3% by weight, zirconium (Zr) 0.3 to 2% by weight, iron (Fe) 0.1 to It provides an aluminum alloy for die casting capable of anodizing including 2 wt%, strontium (Sr) 0.05 to 0.5 wt%, titanium (Ti) 0.05 to 0.5 wt%, the remainder aluminum (Al), and unavoidable impurities.

According to a preferred embodiment of the present invention, the aluminum alloy for die casting capable of anodizing further includes at least one selected from the group consisting of chromium (Cr), magnesium (Mg), tin (Sn) and calcium (Ca). can do.

According to a preferred embodiment of the present invention, in the aluminum alloy for die casting capable of anodizing, the impurity may be included in an amount of 0.01 to 0.2 wt% based on the total weight of the entire alloy.

According to a preferred embodiment of the present invention, the aluminum alloy for die casting capable of anodizing is manganese (Mn) 3.7 wt%, zinc (Zn) 2.0 wt%, zirconium (Zr) 0.8 wt%, iron (Fe) 0.3 wt%, 0.1 wt% of strontium (Sr), 0.1 wt% of titanium (Ti), and the balance aluminum (Al) may be included.

According to a preferred embodiment of the present invention, the aluminum alloy for die casting capable of anodizing is manganese (Mn) 3.7 wt%, zinc (Zn) 2.0 wt%, zirconium (Zr) 0.8 wt%, iron (Fe) 0.3 wt%, 0.1 wt% of strontium (Sr), 0.1 wt% of titanium (Ti), 0.02 wt% of calcium (Ca), and the balance aluminum (Al) may be included.

The aluminum alloy for die casting according to the present invention contains manganese (Mn) in a high content of 2.5 wt% or more to greatly improve the fluidity of the alloy, thereby facilitating the die-casting casting process and preventing sintering, as well as preventing the occurrence of sintering by anodizing It is possible to form a uniform and thick oxide film, so that a product with excellent appearance quality can be manufactured.

In addition, the aluminum alloy for die casting according to the present invention does not contain harmful elements such as nickel (Ni), lead (Pb), beryllium (Br), cobalt (Co), etc., except when it is included as an unavoidable impurity, silicon (Si ) and copper (Cu) are not intentionally included, so a product with excellent surface glossiness can be manufactured by anodizing.

1 is a process diagram illustrating a method of manufacturing an aluminum alloy for die casting using an aluminum alloy for die casting according to an embodiment.
2 is a conceptual diagram showing the structure of an aluminum alloy die-cast product manufactured from an aluminum alloy for die-casting according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, since the description of the present invention is merely an embodiment for structural or functional description, the scope of the present invention should not be construed as being limited by the embodiment described in the text. That is, since the embodiment may have various changes and may have various forms, it should be understood that the scope of the present invention includes equivalents capable of realizing the technical idea. In addition, since the object or effect presented in the present invention does not mean that a specific embodiment should include all of them or only such effects, it should not be understood that the scope of the present invention is limited thereby.

The meaning of the terms described in the present invention should be understood as follows.

Terms such as “first” and “second” are for distinguishing one component from another, and the scope of rights should not be limited by these terms. For example, a first component may be termed a second component, and similarly, a second component may also be termed a first component. When a component is referred to as being “connected” to another component, it may be directly connected to the other component, but it should be understood that other components may exist in between. On the other hand, when it is mentioned that a certain element is "directly connected" to another element, it should be understood that the other element does not exist in the middle. Meanwhile, other expressions describing the relationship between elements, that is, “between” and “immediately between” or “neighboring to” and “directly adjacent to”, etc., should be interpreted similarly.

The singular expression is to be understood as including the plural expression unless the context clearly dictates otherwise, and terms such as "comprises" or "have" refer to the described feature, number, step, action, component, part or these It is intended to indicate that a combination exists, and it should be understood that it does not preclude the possibility of the existence or addition of one or more other features or numbers, steps, operations, components, parts, or combinations thereof.

All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Terms defined in the dictionary should be interpreted as being consistent with the meaning of the context of the related art, and cannot be interpreted as having an ideal or excessively formal meaning unless explicitly defined in the present invention.

Hereinafter, the present invention will be described in detail.

The aluminum alloy according to the present invention contains 2.5 to 7% by weight of manganese (Mn), 1 to 3% by weight of zinc (Zn), 0.3 to 2% by weight of zirconium (Zr), 0.1 to 2% by weight of iron (Fe), and strontium (Sr) ) 0.05 to 0.5% by weight, titanium (Ti) 0.05 to 0.5% by weight, the balance aluminum (Al) and unavoidable impurities.

Specifically, since the aluminum alloy for die casting according to the present invention does not intentionally contain silicon (Si) and copper (Cu), a product with excellent gloss can be manufactured through anodizing treatment, and manganese (Mn) is 2.5 Containing a high content of more than % by weight, it improves the fluidity of the alloy and prevents the formation of air bubbles inside the mold, thereby facilitating the die-casting casting process and manufacturing a product with excellent appearance quality, and coarse rod-shaped intermetallic By suppressing the formation of compounds, the strength is excellent, and properties such as crack resistance are excellent.

In addition, if the molded article is manufactured by molding by the die-casting method and then the molded article is anodized, an oxide film is well formed on the surface to produce a product with a uniform color, and the oxide film can implement excellent abrasion resistance. can be manufactured.

For reference, silicon (Si) improves castability during die casting of an aluminum alloy, but has problems in reducing elongation properties and reducing gloss by generating stains on the product surface, and copper (Cu) stress corrosion cracking. It plays a role in increasing the resistance, but there is a problem in that it reduces the glossiness by generating stains on the surface of the product.

Looking at each composition included in the aluminum alloy according to the present invention in detail, manganese (Mn) is added during the dissolution process of the aluminum ingot (INGOT) to increase the refinement of the structure, and _{to precipitate the Mn-Al 6} phase to strengthen the solid solution. and dispersion of fine precipitates to improve the mechanical properties of the aluminum alloy, suppress recrystallization to maintain high properties even after homogenization, and improve the fluidity of the alloy during molten metal to facilitate the die-casting casting process, It is an element introduced to prevent discoloration during anodizing.

In the aluminum alloy for die casting according to the present invention, manganese (Mn) may be included in an amount of 2.5 to 7% by weight based on the total weight of the entire alloy product, and when manganese is included in less than 2.5% by weight, the effect of improving the fluidity and strength of the alloy is When it is insignificant and exceeds 7 parts by weight, not only sintering occurs, but also manganese is not completely dissolved in the alloy structure to form a coarse intermetallic compound, and intermetallic compound is generated at the grain boundary to prevent deterioration of aesthetic quality due to selective corrosion. There is a risk of causing a defect, and there is a possibility that it may cause defects by lowering the strength and glossiness.

Zinc (Zn) acts as a reinforcing element in the aluminum alloy for die casting, giving a strengthening effect when added within the solid solution range to improve strength, and is used in an amount of 1 to 3% by weight based on the total weight of the entire alloy product. may be added.

When the content of zinc (Zn) is less than 1% by weight, it is difficult to achieve a sufficient strength improvement effect, and when it exceeds 3% by weight, it is a factor of segregation and a problem that a uniform appearance cannot be obtained may occur.

Zirconium (Zr) is an element that enables anodization in an aluminum alloy for die casting and undergoes a chemical reaction during anodizing. All of the dissolved Al-Zr or the crystallized zirconium (Zr) have an anodization reaction at the same level as aluminum (Al). to form a uniform porous layer. In particular, since it is dissolved as a very small fine element in the matrix during solid solution, it serves to improve the mechanical properties by promoting grain refinement, and may be added in an amount of 0.3 to 2 wt% based on the total weight of the entire alloy product.

When the content of zirconium (Zr) is less than 0.3% by weight, it is difficult to form an oxide film by anodization and it is difficult to expect a sufficient effect of improving mechanical properties. There is a fear that a hard spot may be generated, and there is a fear that a decrease in elongation among tensile properties may occur.

Iron (Fe) can increase the strength while minimizing the deterioration of the thermal conductivity of aluminum, and reduce the adhesion in the die in the die-casting aluminum alloy to improve the burning phenomenon in which the aluminum alloy sticks to the inside of the mold and improve the mold It plays a role in reducing the erosion of In addition, since iron (Fe), a major alloying element, _{generates various intermetallic compounds such as α-Fe intermetallic compound, β phase, and Al 6} (Mn,Fe) phase, physical properties can be improved by controlling the precipitation phase. Since iron (Fe) exhibiting the above properties has a low solubility in aluminum at room temperature in an aluminum alloy, most of _{it is crystallized as an intermetallic compound such as Al 3} Fe after casting, so it is 0.1 to 2 weight by weight based on the total weight of the entire alloy. % may be added.

If the content of iron (Fe) is less than 0.1% by weight, demolding is lowered and there is a risk that the aluminum alloy may be sintered in the mold, and if it exceeds 2% by weight, the Fe-rich phase (Fe-rich phase) is excessively crystallized. There is a possibility that the castability of the alloy is reduced, and the appearance quality and corrosion resistance are deteriorated due to rapid oxidation during anodizing.

Strontium (Sr) serves to prevent segregation by improving strength and uniform composition distribution within the product structure, and is a coarse rod-shaped intermetallic compound even when manganese is contained in a high content of 2.5 wt% or more. It is possible to inhibit the formation to prevent a decrease in strength, and may be added in an amount of 0.05 to 0.5% by weight based on the total weight of the entire alloy.

When the content of strontium (Sr) is less than 0.05% by weight, it is difficult to realize compositional uniformity, and when the content of strontium (Sr) is more than 0.5% by weight, there is a fear that the ductility of the aluminum alloy is reduced.

Titanium (Ti) plays a role in preventing hot cracks by refining crystal grains and improving glossiness, and as an element with very little solid solution with aluminum (Al), it is used as a nucleation site by the capture reaction, and the physical properties of the product , in particular, can improve hardness, and may be added in an amount of 0.05 to 0.5 wt% based on the total weight of the entire alloy.

When the content of titanium (Ti) is less than 0.05% by weight, it is difficult to realize the effect of refining the grains, and when it exceeds 0.5% by weight, it is difficult to expect additional physical property improvement.

On the other hand, the aluminum alloy according to the present invention includes aluminum (Al) as a main element, and 1 selected from the group consisting of chromium (Cr), magnesium (Mg), tin (Sn) and calcium (Ca) to improve physical properties. It may be configured to further include more than one species of element.

Specifically, chromium (Cr) prevents stress corrosion cracking in aluminum alloys, plays a role in improving corrosion resistance, and is precipitated as a fine compound during heat treatment to suppress grain growth, but when it is contained in excess, the strength decreases It is preferable to limit it to be included in an amount of 0.001 to 0.03% by weight based on the total weight of the entire alloy because there is a risk of deterioration.

Magnesium (Mg) improves strength degradation due to the use of manganese, enables the manufacture of alloys with uniform surface gloss, and can be added to increase corrosion resistance, strength, and ductility. It plays a role in increasing the strength of the aluminum alloy by creating a phase, but when the content is excessive, the heat conduction decreases and there is a lot of oxide formation in the casting, which affects the casting quality and the elongation decreases due to heat treatment, and when the content is insufficient, the strength decreases Therefore, in order to secure strength and elongation, it is preferable to limit it to be included in an amount of 0.001 to 0.01 wt% based on the total weight of the entire alloy.

Tin (Sn) can be added to improve the formability of the aluminum alloy through the addition of a trace amount, but when the content is excessive, the fraction of tin particles increases, which may cause a sharp decrease in the strength and hardness of the aluminum alloy. It is preferable to limit it to be included in an amount of 0.001 to 0.5% by weight based on the total weight of the.

In addition, the aluminum alloy for die casting according to the present invention may be configured to further include calcium (Ca), and calcium (Ca) is used for phase refinement and spheroidization of iron (Fe)-based intermetallic compounds such as _{Al 3 Fe.} Induced to improve abrasion resistance and yield strength, it is possible to prevent deterioration of tensile properties such as tensile strength and elongation even when iron (Fe) is included. To improve the durability of the aluminum alloy for die casting by inducing the formation of an oxide film layer with a uniform and dense, thick structure. Calcium (Ca) as described above may introduce a compound containing calcium, calcium oxide (CaO), calcium cyanide (Ca(CN) ₂ ), calcium carbide (CaC ₂ ), calcium hydroxide (Ca(OH) ₂ ) , calcium carbonate (CaCO ₃ ) or a calcium compound containing a mixture thereof may be used, and may be added in an amount of 0.01 to 0.1 wt% based on the total weight of the entire alloy.

When the content of calcium (Ca) is less than 0.01% by weight, it is difficult to expect improvement in physical properties, and when it exceeds 0.1% by weight, there is a risk of deterioration of appearance quality due to rapid oxidation during anodizing. Such calcium (Ca) is introduced through a method of preparing a molten metal by dissolving an aluminum base material and then adding a calcium compound to the molten metal, heating the molten metal to a temperature of 800 to 950 ° C. After removing the impurities, the molten metal can be die-cast to manufacture a molded product.

When anodizing a molded article made of an aluminum alloy having the composition as described above, an oxide film having a thickness of 5 to 50 μm is formed on the surface of the aluminum alloy by the anodizing treatment, and the oxide film has a diameter of several tens of nanometers (nm). A large number of fine holes are formed in the vertical direction, and the vertical holes can form a porous structure with one side open. Such an oxide film has high transparency and does not lose metal texture even when colored, so aluminum for die casting has excellent decorative properties. alloys can be formed.

On the other hand, the aluminum alloy according to the present invention may contain impurities that are unavoidably present in the structure, the impurities being silicon (Si), copper (Cu), nickel (Ni), lead (Pb), beryllium (Br), Cadmium (Cd) and the like may be included, but is not limited thereto.

Such impurities are preferably limited to 0.01 to 0.2 wt% or less based on the total weight of the total alloy of the aluminum alloy.

According to a preferred embodiment of the present invention, the aluminum alloy for die casting capable of anodizing is manganese (Mn) 3.7 wt%, zinc (Zn) 2.0 wt%, zirconium (Zr) 0.8 wt%, iron (Fe) 0.3 wt%, 0.1 wt% of strontium (Sr), 0.1 wt% of titanium (Ti), and the balance aluminum (Al) may be included.

In addition, according to a preferred embodiment of the present invention, the aluminum alloy is manganese (Mn) 3.7 wt%, zinc (Zn) 2.0 wt%, zirconium (Zr) 0.8 wt%, iron (Fe) 0.3 wt%, strontium (Sr) ) 0.1% by weight, titanium (Ti) 0.1% by weight, calcium (Ca) 0.02% by weight, and the balance may include aluminum (Al).

The aluminum alloy for die casting according to the present invention as described above contains manganese (Mn) in a high content of 2.5 wt % or more to greatly improve the fluidity of the alloy, thereby facilitating the die casting casting process and preventing seizures from occurring, By anodizing, a uniform and thick oxide film can be formed, so that a product with excellent appearance quality can be manufactured.

In addition, when manufacturing a product using the die casting method, a uniform and thick oxide film can be formed by anodizing on the surface of the product, so that the oxide film is well formed through anodizing to obtain a uniform color, and excellent abrasion resistance can be realized. Excellent appearance quality and product durability.

In addition, the aluminum alloy for die casting according to the present invention does not contain harmful elements such as nickel (Ni), lead (Pb), beryllium (Br), cobalt (Co), etc., except when it is included as an unavoidable impurity, silicon (Si ) and copper (Cu) are not intentionally included, so a product with excellent surface glossiness can be manufactured by anodizing.

On the other hand, the aluminum alloy for die casting according to the present invention can be manufactured as an aluminum alloy die-cast product by the following method.

1, the aluminum alloy for die casting of the present invention, manganese (Mn) 2.5 to 7 wt%, zinc (Zn) 1 to 3 wt%, zirconium (Zr) 0.3 to 2 wt%, iron (Fe) 0.1 to 2% by weight, strontium (Sr) 0.05 to 0.5% by weight, titanium (Ti) 0.05 to 0.5% by weight, the remainder aluminum (Al), and preparing an ingot containing unavoidable impurities, by dissolving the ingot Preparing a molten metal, supplying the molten metal to a die casting mold to produce an aluminum alloy molded article, post-processing the aluminum alloy molded article, anodizing the post-processed aluminum alloy molded article to form an oxide film, an oxide film is formed It can be manufactured by a method comprising the step of coloring the aluminum alloy molded article, sealing the colored aluminum alloy molded article to manufacture an aluminum alloy die-cast product.

First, an ingot having the composition as described above is prepared, and then heated to 700 to 1200° C. to sufficiently dissolve the ingot to prepare molten metal. After dissolving the ingot, the molten metal is degassed, molten metal cleaner, and fine particles as necessary. It is also possible to proceed concurrently with topic processing.

Preferably, in this step, a molten metal is prepared by dissolving an aluminum base material by heating to a temperature of 700 to 800° C., and then manganese (Mn), zinc (Zn), zirconium (Zr), iron (Fe), strontium (Sr) ), titanium (Ti) is mixed to prepare a mixed molten metal, and then a calcium compound is introduced into the mixed molten metal, heated to a temperature of 800 to 950 ℃ to mix calcium, and impurities contained in the calcium compound are removed, and then the molten metal is die-casting. molded products can be manufactured.

Specifically, in this step, the molten alloy is heated to a temperature of 700 to 800° C. to dissolve each component to prepare a molten metal. When a calcium compound is mixed, a calcium compound is introduced into the mixed molten metal, and 800 to 950 Calcium is mixed by heating to a temperature of °C, impurities contained in the calcium compound are removed, and then the molten metal is die-casting to manufacture a molded article. When the temperature of the molten metal is less than 800 °C, it is difficult to increase the calcium content in the molten metal to 0.01 wt% or more, and when it exceeds 950 °C, it is difficult to additionally increase the high calcium content.

More preferably, aluminum (Al), manganese (Mn), zinc (Zn), zirconium (Zr), iron (Fe), strontium (Sr), titanium (Ti) is dissolved at a temperature of 700 to 750 ° C. A molten alloy can be prepared, and when calcium (Ca) is added, aluminum (Al), manganese (Mn), zinc (Zn), zirconium (Zr), iron (Fe), strontium ( Sr) and titanium (Ti) may be dissolved to prepare an aluminum alloy molten metal, and then the prepared molten metal may be heated to a temperature of 800 to 950° C. to increase the calcium content to 0.01 to 0.1 wt %.

At this time, when the temperature of the molten metal is less than 800 ℃, there is a problem that the content of calcium (Ca) is difficult to contain 0.01% by weight or more, when it exceeds 950 ℃, it is difficult to expect an additional increase in the content. Preferably, the content of calcium (Ca) may be adjusted to be 0.01 to 0.1 wt%.

Next, the molten metal may be cast in a die casting mold and formed to manufacture an aluminum alloy molded article. In the die casting process, it is preferable to maintain the temperature of the mold to be 300 to 500 ℃ and to maintain the temperature of the molten metal to be 600 to 950 ℃. Through this die casting process, it is excellent in the degree of freedom of processing and dimensional accuracy. It is also possible to form thin-walled products and has an advantage in mass production. The aluminum alloy molded article manufactured through die casting can be post-processed uniformly through a chemical polishing process such as a physical polishing method through a sanding process or a buffing process, or a chemical polishing process such as a barrel process immersing in a chemical, if necessary. It is not limited thereto.

Next, anodizing treatment of forming an oxide film on the surface of the molded article by flowing an electric current in a state in which the aluminum alloy molded article is immersed in an aqueous solution can be carried out with oxalic acid, sulfuric acid, chromic acid, or By immersing the aluminum alloy molded article in an aqueous solution containing a mixture thereof, and allowing an electric current to flow through the aqueous solution, a porous hard oxide film is formed on the surface of the aluminum alloy molded article to improve the corrosion resistance and decorativeness, appearance, etc. of the aluminum alloy molded article. and is not limited to the specific operating conditions of the anodizing process, and can be anodized using various operating conditions.

Then, the aluminum alloy molded article formed with an oxide film through anodizing is immersed in a coloring tank in which a dye, a pigment, a coloring liquid, or a mixture thereof is supported, and a coloring process of adsorbing the required color to the small pores formed on the surface can be performed. Also, the surface of the product can be colored through organic dyes, inorganic dyes, electrolytic coloring, pigment precipitation, or a combination of organic dyes and electrolytic coloring.

Next, a sealing process is performed to block the micro-holes formed on the surface of the aluminum alloy molded article that has been subjected to the coloring process. In the sealing process, the structure of the oxide film may be physically damaged by the porous oxide film layer adsorbing foreign substances, chemicals, etc. This is done to strengthen the corrosion resistance of the anode film, to improve the discoloration of dyes or fading by sunlight, and to improve the dirtiness of the finished product, and this purpose can be achieved by forming an organic film on the surface. The sealing treatment may be performed using deionized water, distilled water, or the like, and may be performed at 90 to 100° C., and may be performed for 1 to 5 minutes per μm according to the thickness of the oxide film.

Thereafter, an organic film can be additionally formed by applying a film treatment agent to the surface of the aluminum alloy molded article that has been sealed, and this film process is performed to improve corrosion resistance and wear resistance on the surface of the aluminum alloy molded article after the sealing process. can do. The coating agent may include a nonionic compound, and coating treatment may be performed at 80 to 90° C. for 5 to 10 minutes.

Accordingly, as shown in FIG. 2, the aluminum alloy die-cast product manufactured with the aluminum alloy for die casting according to the present invention is colored by coloring the porous oxide film layer generated after anodizing to adsorb the coloring solution to the micro-holes, and to the sealing process. It can be applied to a variety of products such as automobile parts, electronic products, and electronic device cases, as various decorative expressions are possible by blocking micro-holes by making use of the characteristics of the existing aluminum alloy.

Hereinafter, the present invention will be described in more detail by way of examples.

The presented examples are only specific examples of the present invention, and are not intended to limit the scope of the present invention.

<Examples and Comparative Examples>

After preparing an aluminum alloy ingot with a composition as shown in Tables 1 to 3 below, each ingot was melted in a melting furnace at 750 ° C. to prepare a molten metal, and the prepared molten metal was supplied to a die casting mold and then cast to prepare an aluminum alloy specimen. prepared. For each ingot, impurities adjusted to be less than 0.2 wt% based on the total weight of the entire alloy product were used.

In addition, the molten metal containing calcium was prepared by preparing an aluminum alloy ingot, then dissolving each ingot in a melting furnace at 750 ° C. to prepare a molten metal, and then adding calcium oxide while heating to a temperature of 750 to 950 ° C. It was prepared by stirring. .

The surface of the prepared aluminum alloy specimen was degreased by immersion in a degreasing solution, followed by immersion cleaning in an aqueous alkali solution, chemical polishing, and pretreatment by immersion cleaning in a desmut solution. As the degreasing solution, an aqueous solution containing 100 g/L of NaOH, 80 g/L of sodium carbonate, and 3 mL/L of nonylphenol ethoxylate was used, and the aqueous alkali solution was an aqueous sodium hydroxide solution containing 110 g/L of NaOH, It was immersed in a desmut solution containing nitric acid and hydrofluoric acid at a temperature of 30° C. for 5 minutes.

The pretreated aluminum alloy specimen was immersed in an electrolyte solution, and an oxide film was formed on the surface of the specimen through anodizing treatment in ^{which a voltage was applied to 18 V, flowed at a current density of 20 mA/cm 2 , and anodized for 20 minutes.} As the electrolyte, a mixed solution containing 15% by weight of sulfuric acid, 5% by weight of oxalic acid, 5% by weight of borate, and the remainder of distilled water was used.

The specimen on which the oxide film was formed was immersed in a colorant (Black MLW) and then immersed at 70° C. for 20 minutes to color it, and the colored specimen was immersed in a treatment solution to seal it, washed with water and dried to prepare an aluminum alloy specimen product did. As the treatment solution, a mixed solution containing 3 wt% of butyl carbitol, 2 wt% of tetrachloroethylene, 5 wt% of butyl Cellusolve, 2 wt% of lactic acid and the remainder of distilled water was used for sealing.

<Experimental example>

(1) Flowability and crack sensitivity evaluation

Fluidity is measured by injecting molten aluminum alloy having the composition according to Examples and Comparative Examples into a fluidity test mold maintained at a temperature of 200 ° C., and measuring the solidified length (unit: mm) after the molten alloy flows a certain distance. was evaluated, and the results are shown in Table 4 below. Fluidity was evaluated by preparing a specimen having a width of 10 mm, a thickness of 4 mm, and a maximum length of 1200 mm.

In addition, the molten aluminum alloy having the composition according to Examples and Comparative Examples was injected into a crack test mold maintained at a temperature of 200 ° C. After the molten alloy was solidified, the crack sensitivity was evaluated using Equation 1 below, and the results are shown below. It is shown in Tables 4 to 6 (however, in Equation 1 below, HTS denotes crack sensitivity, W _crack denotes crack width factor, f _length denotes crack length factor, and f _location denotes crack location factor).

[Equation 1]

HTS = ∑(W _crack f _length f _location )

(2) Glossiness evaluation

The surface glossiness of aluminum alloys having compositions according to Examples and Comparative Examples was evaluated, and the results are shown in Tables 4 to 6. Glossiness is a quantitative expression of gloss, and was measured using a 60° glossmeter according to ISO 7668 standards.

(3) Evaluation of mechanical properties

Using a universal testing machine (Instron 5982), the mechanical properties of specimens of ASTM Subsize standards of aluminum alloys having compositions according to Examples and Comparative Examples were evaluated, and the results are shown in Tables 4 to 6. Mechanical properties were evaluated by measuring the yield strength (YTS, unit: MPa), tensile strength (UTS, unit: MPa), and elongation (El, unit: %) of the aluminum alloy specimen.

(4) Evaluation of oxide film thickness and appearance

After anodic oxidation of aluminum alloy specimens having compositions according to Examples and Comparative Examples, the thickness (unit: μm) of the oxide film was evaluated, and the results are shown in Tables 4 to 6. The thickness and thickness imbalance of the oxide film were measured using a field emission electron microscope (FE-SEM).

As shown in Tables 4 to 6, as a result of evaluating the fluidity and crack sensitivity, it was confirmed that the fluidity was affected by the content of manganese (Mn) and also affected by the amount of strontium (Sr) added. In the case of crack sensitivity, it was confirmed that the fluidity was affected by the manganese content and also affected by the amount of titanium (Ti) added.

In addition, as a result of evaluating the glossiness, it was confirmed that the glossiness is greatly affected by the content of zinc (Zn), and it is also affected by the content of manganese (Mn), iron (Fe), etc. As a result of the evaluation, it can be confirmed that it is affected by the content of manganese (Mn) and iron (Fe), and as a result of evaluating the film thickness, iron (Fe) with electrical conductivity and zinc (Zn) with low conductivity, titanium ( It was confirmed that the effect was also affected by the amount of Ti) added.

Through the results as described above, the aluminum alloy having the composition according to Examples 1-2 and 1-3 has the best fluidity due to the introduction of manganese (Mn) and titanium (Ti), and has excellent crack sensitivity due to its low crack sensitivity. As it has castability, it was confirmed that various products can be manufactured through the die casting method.

In addition, in the case of glossiness, the effect is improved depending on the amount of zinc added, but in consideration of mechanical properties, it was determined that the aluminum alloy for die casting having the composition according to Examples 1-2 and 1-3 was most suitable. .

And, as a result of evaluating the film properties, it was confirmed that a film of 14.8 to 16.5 μm was formed, and it was confirmed that the deviation between the maximum film thickness and the minimum film thickness was ± 1.7 to 2.5 µm, resulting in a somewhat non-uniform film. was able to confirm

On the other hand, it was confirmed that the film thickness was significantly increased under the same conditions by the addition of calcium, and the thickness deviation of the film was lowered to ± 0.5 to ± 0.9 μm to form an oxide film of uniform thickness, resulting in excellent appearance quality. It was confirmed that not only could the aluminum alloy be manufactured, but a dense film was formed. In particular, since the oxide film has insulating properties, it was determined that excellent corrosion resistance could be provided by suppressing the flow of corrosion current in the electrochemical corrosion process, thereby forming a film with excellent durability such as abrasion resistance. It was judged that the durability of the alloy was excellent.

(5) Evaluation of calcium (Ca) content according to the temperature of the molten metal

At a temperature of 750 ℃, aluminum (Al) 93.2 kg, manganese (Mn) 3.5 kg, zinc (Zn) 2.0 kg, zirconium (Zr) 0.8 kg, iron (Fe) 0.3 kg, strontium (Sr) 0.1 kg, titanium (Ti) ) by dissolving 0.1 kg to prepare a molten aluminum alloy having the same composition as in Example 1-2, and then adjusting the temperature (unit: °C) of the molten aluminum alloy as shown in Table 7 below to obtain calcium oxide (CaO) of the molten metal. Mixed so as to be 0.3 kg relative to the total weight, and die-casting to prepare an aluminum alloy molded article.

The content (unit: weight %) of calcium (Ca) contained in the aluminum alloy molded article manufactured by using an inductively coupled plasma mass spectrometer was evaluated, and the results are shown in Table 7 below.

As shown in Table 7, at a temperature of less than 850 ° C, it was confirmed that the high amount of calcium was insignificant about 10%, but at a temperature between 800 ° C and 950 ° C, the solid solution of calcium increased, so that for the addition of calcium (Ca) The temperature of the suitable molten metal was confirmed.

Through the results as described above, aluminum (Al), manganese (Mn), zinc (Zn), zirconium (Zr), iron (Fe), strontium (Sr), titanium (Ti) at a temperature of 700 to 750 ° C. It is preferable to add calcium (Ca) by heating the prepared molten metal to a temperature of 800 to 950 ℃ after preparing a molten alloy upon melting, and 830 ℃ is considered to be the most ideal in consideration of economic feasibility.

The detailed description of the preferred embodiments of the present invention disclosed as described above is provided to enable any person skilled in the art to make and practice the present invention. Although the above has been described with reference to preferred embodiments of the present invention, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the scope of the present invention. For example, a person skilled in the art may use each configuration described in the above-described embodiments in a way that is combined with each other. Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The present invention may be embodied in other specific forms without departing from the spirit and essential characteristics of the present invention. Accordingly, the above detailed description should not be construed as restrictive in all respects but as exemplary. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are included in the scope of the present invention. The present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. In addition, claims that are not explicitly cited in the claims may be combined to form an embodiment or may be included as a new claim by amendment after filing.

Claims (5)

2.5 to 7 wt% of manganese (Mn), 1 to 3 wt% of zinc (Zn), 0.3 to 2 wt% of zirconium (Zr), 0.1 to 2 wt% of iron (Fe), 0.05 to 0.5 wt% of strontium (Sr), Titanium (Ti) 0.05 to 0.5% by weight, calcium (Ca) 0.01 to 0.1% by weight, the remainder aluminum (Al) and anodizing aluminum alloy for die casting including inevitable impurities. delete According to claim 1,
The aluminum alloy for anodizing possible die casting, characterized in that the impurity is included in an amount of 0.01 to 0.2% by weight based on the total weight of the total alloy. delete According to claim 1,
Manganese (Mn) 3.7 wt%, zinc (Zn) 2.0 wt%, zirconium (Zr) 0.8 wt%, iron (Fe) 0.3 wt%, strontium (Sr) 0.1 wt%, titanium (Ti) 0.1 wt%, calcium ( Ca) 0.02 wt%, the remainder aluminum (Al) and anodizing aluminum alloy for die casting, characterized in that it contains unavoidable impurities.

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