KR20190134157A - Method for treating a surface of aluminum-silicon alloy material - Google Patents

Abstract

The present invention relates to a surface treatment method of an aluminum-silicon alloy. The surface treatment method of an aluminum-silicon alloy specimen may form an oxide film on a surface of the alloy specimen faster by plasma oxidation treatment. In addition, by polishing the surface of the alloy specimen and then plasma oxidation to form an oxide coating, not only the interface adhesion between the alloy specimen surface and the oxide coating can be improved, but also defects such as cracks can be prevented. Furthermore, when a heat treatment step is further performed after the oxide film is formed, pores, cracks, etc. in the oxide film may be sealed, thereby further improving wear resistance of the alloy specimen.

Description

Surface Treatment of Aluminum-Silicon Alloy Specimens {METHOD FOR TREATING A SURFACE OF ALUMINUM-SILICON ALLOY MATERIAL}

The present invention relates to a surface treatment method of an aluminum-silicon alloy specimen.

Among the refrigerant compressors, the scroll compressor has a simple structure that can be miniaturized compared to other compressors, and has been widely applied to a cooling / air conditioning system due to its low noise / vibration and excellent efficiency. Cast iron is mainly used as a material of the scroll compressor, but is now replaced by an aluminum alloy. For this reason, development of an aluminum alloy which is excellent in mechanical properties such as strength and wear resistance and is lightweight is required. Thus, methods for improving the mechanical properties by forming an oxide film on the surface of the aluminum alloy has been proposed.

Anodizing is one of the common methods of forming an oxide film on the surface of a metal material such as an aluminum alloy. The anodic oxidation method is a method of forming an oxide film on the surface of a material by positively polarizing a metal material in an acid and a basic electrolyte solution. The oxide film formed by the anodic oxidation treatment has a thickness of several micrometers, and serves to protect the surface of the metal material from corrosion, abrasion, external impact, and the like.

However, the anodic oxidation treatment method has a problem that the maximum applied voltage is low as 50 V, so that it takes a relatively long time to form an oxide film having a desired thickness on the surface of the metal material and thus the process efficiency is lowered. For example, in order to form an oxide film having a thickness of about 20 μm on the surface of the aluminum-silicon alloy, anodizing treatment should be performed for about 2 hours or more. In addition, when the anodization method is applied, there is a problem in that cracks occur when an oxide film is formed at a corner of a metal material.

Thus, various methods of treating metal surfaces in a faster and more efficient manner have been introduced. For example, Korean Patent No. 10-1214400 includes sodium silicate and sodium hydroxide, Na ₂ CrO ₇ H ₂ O, (NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O and 5 (NH _{4) 2} O · and using 12WO ₃ · 11H ₂ O was added to the electrolytic solution, etc. discloses a method of processing a surface of an aluminum-based metal. However, the above method uses an electrolyte solution containing an expensive sample, which is not economical.

Korea Patent Registration No. 10-1214400

Accordingly, it is an object of the present invention to provide a method for surface treatment of aluminum-silicon alloy specimens in which an oxidation treatment time is short, production efficiency is high, cost is more economical, and a crack-free oxide film can be formed on the surface. .

In order to achieve the above object, the present invention, (1) polishing the surface of the aluminum-silicon alloy specimen; And (2) provides a surface treatment method of the aluminum-silicon alloy specimen comprising the step of plasma oxidation treatment of the surface of the alloy specimen in the electrolyte.

The surface treatment method of the aluminum-silicon alloy specimen according to the present invention can form an oxide film on the surface of the alloy specimen faster by the plasma oxidation treatment method, thereby improving process time and efficiency. Furthermore, the cost can be reduced by using a compound that is cheaper than the electrolytes used in the prior art. In addition, by polishing the surface of the alloy specimen and then plasma oxidation to form an oxide film, not only the interface adhesion between the alloy specimen surface and the oxide film can be improved, but also defects such as cracks can be prevented. Furthermore, when the heat treatment step is further performed after the oxide film is formed, the pores, cracks, and the like in the oxide film may be sealed to further improve wear resistance of the alloy specimen.

1 is a flow chart of the surface treatment method of the aluminum-silicon alloy specimen according to the present invention.
2 is a photograph of the surface of the aluminum-silicon alloy specimens obtained in Example 4 and Comparative Example 4 by a runner electron microscope (SEM).

The present invention is not limited to the contents disclosed below, but may be modified in various forms as long as the gist of the present invention is not changed.

"Including" in the present specification means that it may further include other components unless otherwise specified. In addition, all numbers and expressions indicating amounts of components, reaction conditions, and the like described herein are to be understood as being modified in all instances by the term "about" unless otherwise specified.

Surface treatment method of the aluminum-silicon alloy specimen of the present invention, (1) polishing the surface of the aluminum-silicon alloy specimen; And (2) plasma oxidizing the surface of the alloy specimen in an electrolyte solution.

Step (1)

This step is to make a mirror surface by polishing the surface of the aluminum-silicon alloy. Specifically, a specimen of aluminum-silicon alloy may be prepared, and the surface of the alloy specimen may be polished to be 5 micron or less, 3 micron or less, 0.1 to 5 micron, or 0.1 to 3 micron. "micron" refers to a specification of a polishing pad used for polishing, and is a common unit commonly used in metal polishing processes in the art.

For example, when the alloy specimen is polished using a polishing pad of 3 microns and polished to about 3 microns, the surface of the alloy specimen may be a mirror-like mirror surface. In this case, the polishing pad may be used together with a diamond paste as necessary.

 When the alloy specimen has a surface roughness in the mirror state, the interfacial adhesion between the alloy specimen surface and the oxide film may be improved.

The aluminum-silicon alloy specimen may include components such as aluminum, silicon, copper, and magnesium. Specifically, the alloy may include 5 to 15% by weight, 7 to 15% by weight, 5 to 14% by weight, 9 to 15% by weight, or 7 to 14% by weight of silicon. In addition, the alloy may include 0.1 to 5% by weight, 0.1 to 3% by weight, 1 to 5% by weight or 1 to 3% by weight of copper. In addition, the alloy may comprise 0.1 to 1.5% by weight, or 0.1 to 1% by weight of magnesium. Furthermore, the alloy may further comprise 0.1 to 3% by weight, 0.1 to 2% by weight, or 0.1 to 1% by weight of nickel. In addition, the balance of the alloy specimen may be aluminum.

In the field of aluminum-silicon alloy, the silicon content is about 10% by weight, specifically, when it is 9% by weight or more, it is evaluated that silicon is included in a high content, and the aluminum-silicon alloy including the high content of silicon has the advantages of aluminum. It can have high strength while keeping them (eg light weight).

Step 2

In this step, the surface of the polished alloy specimen is subjected to plasma oxidation in an electrolyte solution. Specifically, after the alloy specimen is immersed in the electrolyte solution, plasma oxidation may be performed to form an oxide film on the surface of the alloy specimen.

The electrolyte solution may include at least one precursor selected from the group consisting of sodium hydroxide (NaOH) and sodium metasilicate (Na ₂ SiO ₃ ). Specifically, the electrolyte may include the precursor in 0.0001 M to 1 M, 0.001 M to 1 M, 0.001 M to 0.5 M, or 0.001 M to 0.05 M. More specifically, the electrolyte solution contains 0.001 M to 0.5 M or 0.001 M to 0.3 M sodium hydroxide, and 0.001 M to 1 M, 0.001 M to 0.5 M, 0.001 to 0.3 M, or 0.001 to 0.1 M sodium metasilicate can do.

In the plasma oxidation treatment, a plasma is generated on an alloy surface by applying a voltage of 350 V or more.

The plasma oxidation treatment is not limited as long as the oxidation treatment is performed under a condition of generating a plasma. Specifically, the plasma oxidation treatment may be performed by plasma electrolytic oxidation (PEO). The PEO method is also called Micro Arc Oxidation (MAO).

More specifically, in the plasma oxidation treatment, the applied voltage may be 350 to 500 V, 350 to 480 V, 380 to 500 V, 380 to 480 V, or 400 to 480 V, the treatment time is 5 to 15 minutes, 7 to 15 minutes, 5 to 13 minutes, or 7 to 13 minutes.

Through the plasma oxidation treatment of step (2), an oxide film having a thickness of 10 to 100 micron, 30 to 100 micron, 30 to 80 micron, or 50 to 80 micron may be formed on the surface of the alloy specimen.

In general, in the case of an oxide film oxidized under plasma generation, the oxide film is oxidized at a very high rate so that the oxide film is formed into a porous structure having a plurality of fine pores, and the oxide film of such a porous structure is cracked or lifted. Cause badness. In addition, the oxide film of the porous structure has a relatively large area that can be oxidized and can be easily corroded.

Therefore, after the oxide film is formed on the surface of the alloy specimen by plasma oxidation, sealing of the pores in the oxide film may be further performed.

That is, the surface treatment method of the aluminum-silicon alloy according to the present invention may further include, after step (2), (3) heat-treating the plasma oxidized alloy in water.

Step 3

This step is to heat-treat the alloy specimen having the oxide film in water.

The alloy specimen subjected to the plasma oxidation treatment in step (2) is immersed in water at 80 to 130 ° C., 80 to 120 ° C., or 90 to 110 ° C. to be heat-treated so that the oxide film can have a more dense structure. Specifically, when the heat treatment in water expands the volume of the pores in the oxide film is clogged pores.

In addition, the method of sealing by adding a sealing agent can also be used. For example, ethanol-based stearic acid (Stearic acid) can be used as a precursor sealing. When the material is added, the sealing effect may be partially increased, but in general, alcohols are volatilized during the heat treatment, so that the process cost increases. Therefore, the method of heat treatment in water is more preferable.

After the heat treatment step, the alloy specimen is dried.

As described above, the surface treatment method of the aluminum-silicon alloy specimen according to the present invention can form an oxide film on the surface of the alloy specimen faster by the plasma oxidation treatment method, it is possible to improve the process time and efficiency. Furthermore, the cost can be reduced by using a compound that is cheaper than the electrolytes used in the prior art.

In addition, by polishing the surface of the alloy specimen to control the surface roughness, and then plasma oxidation treatment to form an oxide coating, not only can the interface adhesion between the alloy specimen surface and the oxide coating be improved, but also defects such as cracks can be prevented. Can be.

Furthermore, when the heat treatment step is further performed after the oxide film is formed, the pores, cracks, and the like in the oxide film may be sealed to further improve wear resistance of the alloy specimen.

Therefore, the surface treatment method of the aluminum-silicon alloy specimen according to the present invention can be usefully used for the surface treatment of various components such as vehicles, aircraft, medical.

The above content is described in more detail by the following examples. However, the following examples are only for illustrating the present invention, and the scope of the examples is not limited thereto.

[ Example ]

Example  1: Surface Treatment of Aluminum-Silicon Alloy Specimen

An aluminum-silicon alloy comprising 12% by weight of silicon, 3% by weight of copper, 0.5% by weight of magnesium, 0.5% by weight of nickel, and the balance of aluminum was 50 mm × 30 mm × 5 mm (width × length × thickness). The specimen was prepared by cutting in), and the surface of the specimen was polished to 3 micron to be mirror surface.

Thereafter, an electrolyte solution in which 0.0018 M sodium hydroxide and 0.05 M sodium metasilicate was dissolved in deionized water was prepared, and the specimen was immersed in the electrolyte, and then the surface of the alloy specimen was plasma-oxidized by PEO.

Thereafter, the specimen was used as the cathode, the titanium mesh was used as the anode, the maximum allowable voltage was 400 V, the processing time was 5 minutes, and the voltage applied was a constant voltage (CV). The specimen was plasma oxidized using (AC).

Then, the plasma oxidized specimen was immersed in water at 100 ° C. for 30 minutes, taken out again, and dried completely at room temperature.

Examples 2 to 4 : surface treatment of aluminum-silicon alloy specimens

As described in Table 1, the surface treatment was performed in the same manner as in Example 1 except that the voltage and application time were different during the plasma oxidation treatment.

Comparative example  1 to 4: surface treatment of aluminum-silicon alloy specimens

The surface of the aluminum-silicon alloy specimens was treated with # 1000 SiC paper (DEERFOS).

[ Evaluation example ]

Evaluation example  1: wear resistance evaluation

The wear resistance was evaluated based on KS D 8314 for the aluminum-silicon alloy specimens surface treated in Examples 1 to 4 and Comparative Examples 1 to 4.

Voltage (V) Minutes Abrasion Resistance Evaluation Results Log (mm ² / kg) 400 5 Comparative Example 1 -5.63532 Example 1 -5.65979 400 15 Comparative Example 2 -5.61592 Example 2 -5.66189 500 5 Comparative Example 3 -5.56752 Example 3 -5.57609 500 15 Comparative Example 4 -5.30182 Example 4 -5.33034

Evaluation example  2: surface condition evaluation

The surface of the aluminum-silicon alloy surface-treated in Example 4 and Comparative Example 4 was photographed with a scanning electron microscope (SEM). The results are shown in FIG.

Referring to FIG. 2, the aluminum-silicon alloy specimens surface-treated in Example 4 had a densely formed oxide film, whereas the alloy specimens of Comparative Example 4 not only had an interface between the oxide film and the alloy surface but also were separated from each other. It was confirmed that a large number of pores in the structure were formed as compared with the oxide film.

Claims (10)

(1) polishing the surface of the aluminum-silicon alloy specimen; And
(2) plasma treatment of the surface of the alloy specimen in an electrolyte solution, the surface treatment method of the aluminum-silicon alloy specimen. The method of claim 1,
The aluminum-silicon alloy specimen comprises 5 to 15% by weight of silicon, 0.1 to 5% by weight of copper, and 0.1 to 1.5% by weight of magnesium, the silicon-silicon alloy specimen. The method of claim 2,
The aluminum-silicon alloy specimen further comprises 0.1 to 3% by weight of nickel, the surface treatment method of the aluminum-silicon alloy specimen. The method of claim 1,
In the step (1), the surface of the aluminum-silicon alloy specimen is polished to 0.1 to 5 micron, the surface treatment method of the aluminum-silicon alloy specimen. The method of claim 1,
In the step (2), the electrolytic solution comprises at least one precursor selected from the group consisting of sodium hydroxide (NaOH) and sodium metasilicate (Na ₂ SiO ₃ ), aluminum-silicon alloy specimen surface treatment method. The method of claim 5,
The electrolyte solution surface treatment method of the aluminum-silicon alloy specimen comprising 0.0001 M to 1 M. The method of claim 1,
In the plasma oxidation treatment, the applied voltage is 350 to 500 V, the treatment time is 5 to 15 minutes, the surface treatment method of the aluminum-silicon alloy specimens. The method of claim 1,
Method of surface treatment of aluminum-silicon alloy specimens to form an oxide film on the alloy specimen surface through the oxidation treatment of step (2). The method of claim 1,
After the step (2), (3) further comprising the step of heat-treating the plasma oxidized alloy specimen in water, the surface treatment method of the aluminum-silicon alloy specimen. The method of claim 9,
In the step (3), the plasma oxidized alloy specimen is immersed in water of 80 to 130 ℃ heat treatment, aluminum-silicon alloy specimen surface treatment method.

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