KR101616889B1 - Surface treatment method for magnesium or magnesium alloy - Google Patents

Abstract

Disclosed are a surface treatment method for magnesium or magnesium alloy, which uses a brucite crystal film as a lubrication film for forming by forming the brucite crystal film and can remove the film to be clean after the forming. According to an embodiment of the present invention, the surface treatment method for magnesium or magnesium alloy includes: a step of preparing magnesium or magnesium alloy; a step of forming the brucite crystal film on the surface of the magnesium or the magnesium alloy; a step of forming the magnesium or the magnesium alloy on which the brucite crystal film is formed; and a step of removing a crystal film existing on the surface of the formed magnesium or the magnesium alloy. The step of removing the crystal film existing on the formed magnesium or the magnesium alloy uses the denitration method.

Description

TECHNICAL FIELD [0001] The present invention relates to a surface treatment method of magnesium or magnesium alloy,

One embodiment of the present invention relates to a method for surface treatment of magnesium or a magnesium alloy.

Generally, magnesium or magnesium alloy is one of the new materials used in the manufacture of electronic parts such as automobile parts and computers and mobile phones because it is lighter than aluminum, has high mechanical strength, has high dimensional stability and good mechanical properties.

In addition, magnesium or magnesium alloy can be lightened, has high impact resistance, is excellent in vibration absorbing property and electromagnetic wave shielding property and can be widely used in household electric appliances.

However, such magnesium has a low corrosion resistance because it has a standard electrode potential of -2.363 V with respect to the hydrogen electrode at 25 DEG C, and has a disadvantage of increasing the corrosion rate when contacting other electrically positive elements.

Therefore, many studies have been made to improve the corrosion resistance of magnesium alloys.

As a method for improving the corrosion resistance of a magnesium alloy, there is known a method of improving the corrosion resistance of a magnesium alloy by adding an alloying element or improving a corrosion resistance by performing a surface treatment process.

Examples of methods for improving the corrosion resistance of a magnesium alloy through a surface treatment process include anodizing and chromate treatment.

The anodizing treatment is a surface treatment method of improving the corrosion resistance, abrasion resistance and electrical resistance by forming a magnesium oxide layer on the surface of a material by using an electrochemical method. This method has the advantages of low manufacturing cost, simple process and easy management, but it is disadvantageous in that the process efficiency is not good and it takes time.

The chromate treatment is a method of chemical conversion by using a chemical reaction between a treatment liquid and aluminum without using an electrical method, which enables a simple treatment at a relatively low cost, and is excellent in corrosion resistance and uniform appearance. However, since the chromate treatment uses a heavy metal such as chromium, there is a problem that the environment is contaminated.

Another method for surface treatment of magnesium alloys is to mechanically polish the surface of the magnesium alloy or to paint the surface of the alloy by pretreating the coating. However, the surface of the magnesium alloy treated with such a method is always There is a surface layer due to the oxidation of magnesium and the surface layer is not densified and the coating adhesion is low, so there is a limit to improve the corrosion resistance.

Therefore, in order to improve the corrosion resistance, which is an important disadvantage of the magnesium alloy, development of a new surface treatment method such as making the oxide film on the surface of the alloy to be dense is required.

One embodiment of the present invention is a method for forming a brucite crystal film by humidification heat treatment (HHT) of various magnesium alloys AZ31, AZ61, Ca material (Ca-added AZ31 flame retardant) And a surface treatment method of a magnesium or magnesium alloy capable of removing a coating film cleanly after the molding.

One embodiment of the present invention provides a method of manufacturing a semiconductor device, comprising: preparing a magnesium or magnesium alloy; Forming a brucite crystal coating on the surface of the magnesium or magnesium alloy; Molding the magnesium or magnesium alloy in which the bariumite crystal coating is formed; And removing the crystal coating existing on the surface of the molded magnesium or magnesium alloy, wherein removing the crystal coating existing on the surface of the formed magnesium or magnesium alloy comprises using a nitric acid treatment method , A magnesium or magnesium alloy.

The nitric acid treatment may be performed by an acid mixture comprising nitric acid (HNO ₃ ) or nitric acid (HNO ₃ ).

The nitric acid (HNO ₃ ) comprises an aqueous nitric acid solution, and the concentration of the nitric acid aqueous solution may be 1 to 5% by volume.

The nitric acid treatment may be performed for 15 to 240 seconds.

The nitric acid treatment may be performed for 30 to 180 seconds.

Treating the formed magnesium or magnesium alloy with nitric acid to remove the coating; Thereafter, a step of chemically treating the surface of the magnesium or magnesium alloy from which the coating is removed may be further included.

The step of forming a brucite crystal coating on the surface of the magnesium or magnesium alloy may be performed by Humidification Heat Treatment (HHT) at a temperature of 75 to 100 ° C. and a humidity of 85 to 100 RH% .

The humidification heat treatment may be performed at 75 to 100 DEG C for 120 hours or more.

The step of forming a brucite crystal coating on the surface of the magnesium or magnesium alloy may be performed by Humidification Heat Treatment (HHT) at a temperature of 100 ° C to 160 ° C and a humidity of 50 to 100RH% have.

The humidification heat treatment may be performed at 100 ° C to 160 ° C for 2 hours or less.

The magnesium alloy may be at least one selected from the group consisting of AZ31, AZ61, AZ31 flame retardant including Ca, and AM60.

According to one embodiment of the present invention, by forming a brucite crystal film by humidification heat treatment (HHT) of various magnesium alloys AZ31, AZ61, Ca material (Ca-added AZ31 flame retardant) And a surface treatment method of a magnesium or magnesium alloy capable of removing a coating film after the molding is cleanly provided.

At this time, the coating has an excellent effect on corrosion resistance, heat radiation, lubricity, moldability, releasability and the like.

Further, there is an effect that a film can be cleanly removed so as not to affect the final surface treatment step after the molding.

Fig. 1 shows the removal tendency of the coating when the coated AZ31B plate was acid-treated with nitric acid.
Fig. 2 shows the removal tendency of the coating when the coated AZ31B plate was acid-treated with glycolic acid + magnesium nitrate + nitric acid.
FIG. 3 shows the removal tendency of the coating when the coated AZ31B plate was acid-treated with phosphoric acid.
FIG. 4 shows the removal tendency of the coating when the coated AZ31B plate was acid-treated with acetic acid + sodium nitrate.
FIG. 5 shows the tendency of AZ31 magnesium film to be removed by nitric acid concentration and treatment time.
6 is a graphical representation of the film thickness of the AZ31, AM60 magnesium plate removed through acid treatment using the weight change after nitric acid treatment.
FIG. 7 shows a surface image of the coating of the AZ31 magnesium plate after nitric acid treatment for 90 seconds using nitric acid at a concentration of 1.47 vol.%.
8 shows a surface image of the coating of the AZ31 magnesium plate after nitric acid treatment for 120 seconds using nitric acid at a concentration of 1.47 vol%.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Throughout the specification, when an element is referred to as " comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

One embodiment of the present invention provides a method of manufacturing a semiconductor device, comprising: preparing a magnesium or magnesium alloy; Forming a brucite crystal coating on the surface of the magnesium or magnesium alloy; Molding the magnesium or magnesium alloy in which the bariumite crystal coating is formed; And removing the crystal coating existing on the surface of the molded magnesium or magnesium alloy, wherein removing the crystal coating existing on the surface of the formed magnesium or magnesium alloy comprises using a nitric acid treatment method , A magnesium or magnesium alloy.

One embodiment of the present invention is a magnesium plate, a molding material, an extruded material and a three-dimensional molded article (kitchen container, Mg PCB, automobile parts) including magnesium, AZ31, AZ61, Ca material (AZ31 flame retardant added with Ca) Various magnesium alloys can be used.

The surface treatment method of magnesium or magnesium alloy according to an embodiment of the present invention is a method of surface treatment of magnesium or magnesium alloy by performing humidification heat treatment (HHT) on various magnesium alloys AZ31, AZ61, Ca material (Ca-added AZ31 flame retardant) It is an object of the present invention to provide a lubricant film for forming by forming a film and to cleanly remove the film after the molding.

Such a coating imparts not only corrosion resistance but also releasability.

Magnesium or magnesium alloy which is warm-formed causes problems due to the transition of magnesium particles to the mold during molding without lubricant treatment. This not only damages the mold, but also migrates to the surface of the magnesium or magnesium alloy, causing reliability problems in the surface treatment.

Therefore, a lubricant is essential for molding magnesium or a magnesium alloy. Lubricants that can be used are liquid, solid lubricants. The use of liquid lubricant at a high temperature of 250 ° C causes fumes, which can affect the safety of workers. Solid lubricants such as graphite have good lubrication performance, but they require a very concentrated concentration of acid to remove the carbon from the surface. Such a long period of pickling has a big problem, such as a change in the initial design thickness. Therefore, selection of a lubricant is not easy. On the other hand, if a lubricant is not used, it can not be released due to a galling phenomenon in the mold during warm molding.

In order to solve this problem, a method of forming a brucite crystal film on the surface of a magnesium or magnesium alloy and using the brucite crystal film as an lubricating film for molding, thereby minimizing the friction characteristic and imparting releasability and corrosion resistance, can be used without using a lubricant .

However, when the brucite crystal film is used as a lubricant film for molding, it is necessary to clean the film so as not to affect in the final surface treatment process, since the film may be worn out.

Accordingly, the magnesium or magnesium alloy surface treatment method according to an embodiment of the present invention allows the bursite crystal coating to be cleanly removed after the molding is completed, when the bursite crystal coating is used as the lubricating coating for molding, So as to prevent the problems caused by the partial remnant of the coating film when the surface treatment is performed.

Hereinafter, the surface treatment method of the magnesium alloy in the embodiment of the present invention will be described.

Hereinafter, the magnesium alloy refers to a magnesium alloy plate, rod, pipe or the like including magnesium.

A method for surface treatment of a magnesium alloy according to an embodiment of the present invention comprises the steps of forming a brucite crystal film on the surface of a magnesium alloy, molding the brucite crystal film, and then nitriding the magnesium alloy to remove the film.

First, a process of forming a brucite crystal film on a magnesium alloy will be described.

The humidification heat treatment of the magnesium alloy is heat-treated in a humidified atmosphere to form a brucite crystal film of Mg (OH) ₂ on the surface of the magnesium alloy.

By such a humidifying heat treatment, a coating having high corrosion resistance can be formed on the surface of the magnesium alloy. At this time, various magnesium alloys such as Pure Mg and AZ31, AZ61, AZ91D, and AM60 have a considerable difference in the thickness of the coating at the same temperature and humidity, but coincide with the point that the blackening progresses and corrosion resistance appears.

In one embodiment of the present invention, the temperature of the humidifying heat treatment is 75 to 160 ° C. The humidifying atmosphere is 85 to 100% RH at a low temperature of 100 ° C or lower, and 50 to 100% RH at a high temperature of 100 ° C or higher. In this case, the humidification heat treatment should be performed for 120 hours or more at a temperature of 100 ° C or lower, and the magnesium base material can be protected for 48 hours or more in a salt spray test produced by a humidified heat treatment film produced even at a temperature of 100 ° C or higher and a short time of 2 hours or less. In addition, at a low temperature of less than 75 캜, the thickness of the humidified heat treated film is thinned, and at a high temperature exceeding 160 캜, the humidified heat treated film becomes bulky and crumbles.

Then, the magnesium alloy subjected to the humidification heat treatment can be molded.

After the molding is completed, the coating is cleanly removed so as not to affect the final surface treatment process.

More specifically, in one embodiment of the present invention, the surface of the magnesium or magnesium alloy is nitric acid treated to remove the coating.

The nitric acid treatment may be performed by nitric acid (HNO ₃ ) or by an acid mixture containing nitric acid (HNO ₃ ).

The nitric acid (HNO ₃ ) comprises an aqueous nitric acid solution, and the concentration of the nitric acid aqueous solution may be 1 to 5% by volume. The nitric acid treatment may be carried out for 15 to 240 seconds, more specifically 30 to 180 seconds. When the nitric acid treatment having the above-described concentration range is carried out for the above-mentioned range of time, it is possible to cleanly remove the coating film which has been broken by molding, so that the subsequent surface treatment may not be affected.

Alternatively, in the method for surface treatment of a magnesium alloy according to an embodiment of the present invention, the surface of the magnesium or magnesium alloy from which the coating is removed may be subjected to a conversion treatment after the coating is removed.

More specifically, the chemical treatment may include a phosphate treatment, a black salt treatment, a chromate treatment, and the like, and the detailed processes therefor are omitted because they are well known in the related art.

Hereinafter, examples of the present invention will be described. However, the following examples are only illustrative of the present invention and are not intended to limit the scope of the present invention.

After forming a 5 탆 brucite film on an AZ31B plate, pickling treatment was carried out using various acid treatment methods.

Figs. 1 to 4 show the removal tendency of the film when the coated AZ31B plate was acid-treated with nitric acid, glycolic acid + magnesium nitrate + nitric acid, phosphoric acid, and acetic acid + sodium nitrate respectively.

Referring to FIGS. 1 to 4, it can be seen that it is easy to remove the film only in the case of acid treatment in an atmosphere containing nitric acid.

In order to limit the concentration of nitric acid and the treatment time, the AZ31 and AM60 magnesium plates were subjected to a humidification heat treatment at 150 ° C and 95% RH for 1 hour to prepare a 3.30 μm brucite film. Lt; / RTI > for 240 seconds.

FIG. 5 shows the tendency of AZ31 magnesium film to be removed by nitric acid concentration and treatment time.

6 is a graphical representation of the film thickness of the AZ31, AM60 magnesium plate removed through acid treatment using the weight change after nitric acid treatment.

Referring to FIGS. 5 and 6, although there is a difference between the alloys, it can be seen that the higher the concentration, the shorter the removal time.

5 and 6, the nitric acid treatment may be performed in a range of 15 to 240 seconds, and more specifically, when the nitric acid treatment is performed for 30 to 180 seconds, There is an advantage that can be removed.

FIG. 7 shows a surface image of the coating of the AZ31 magnesium plate after nitric acid treatment for 90 seconds using nitric acid at a concentration of 1.47 vol.%.

8 shows a surface image of the coating of the AZ31 magnesium plate after nitric acid treatment for 120 seconds using nitric acid at a concentration of 1.47 vol%.

Referring to FIGS. 7 and 8, it can be seen that the nitrate-weak sites are first removed rather than the brucite coating is removed in the thickness direction. However, if the treatment time is increased to 120 seconds, it can be confirmed that the brucite film is no longer present on the surface.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (11)

Preparing a magnesium or magnesium alloy;
Forming a brucite crystal coating on the surface of the magnesium or magnesium alloy;
Molding the magnesium or magnesium alloy in which the bariumite crystal coating is formed; And
And removing the crystalline coating existing on the surface of the magnesium or magnesium alloy,
Removing the crystalline film existing on the surface of the formed magnesium or magnesium alloy,
A method for surface treatment of magnesium or a magnesium alloy, wherein a nitric acid treatment method is used.
The method according to claim 1,
In the nitric acid treatment,
Nitric acid (HNO _3), or nitrate method for surface treatment of the magnesium or magnesium alloy will (HNO ₃₎ is carried out by an acid mixture containing.
3. The method of claim 2,
The nitric acid (HNO ₃₎ comprises a nitric acid solution,
Wherein the concentration of the nitric acid aqueous solution is 1 to 5% by volume.
The method of claim 3,
In the nitric acid treatment,
Wherein the surface treatment is performed for 15 to 240 seconds.
5. The method of claim 4,
In the nitric acid treatment,
Wherein the magnesium or magnesium alloy is subjected to a surface treatment for 30 to 180 seconds.
The method according to claim 1,
Removing the crystal coating existing on the surface of the magnesium or magnesium alloy; Since the,
Further comprising the step of chemically treating the surface of the magnesium or magnesium alloy from which the coating has been removed.
The method according to claim 1,
Forming a brucite crystal coating on the surface of the magnesium or magnesium alloy,
Wherein the heat treatment is carried out by Humidification Heat Treatment (HHT) at a temperature of 75 to 100 DEG C and a humidity of 85 to 100 RH%.
8. The method of claim 7,
The humidification heat treatment may include:
And at a temperature of 75 to 100 DEG C for 120 hours or more.
The method according to claim 1,
Forming a brucite crystal coating on the surface of the magnesium or magnesium alloy,
Wherein the heat treatment is performed by Humidification Heat Treatment (HHT) at a temperature of 100 to 160 DEG C and a humidity of 50 to 100 RH%.
10. The method of claim 9,
The humidification heat treatment may include:
Wherein the polishing is carried out at 100 to 160 캜 for 2 hours or less.
The method according to claim 1,
Wherein the magnesium alloy is at least one selected from the group consisting of an AZ31 flame retardant including AZ31, AZ61, Ca, and AM60, or a magnesium or magnesium alloy.

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