KR20190098113A - Plasma Electrolytic Polishing Method with Luster and Dimensional Stability - Google Patents

Abstract

The present invention relates to a plasma electrolytic polishing method with luster and dimensional stability. Specifically, according to an embodiment of the present invention, the plasma electrolytic polishing method with luster and dimensional stability includes: a step of preparing a subject; a step of installing an anode and cathode in an electrolyte and connecting the subject to the anode; a step of generating first plasma by applying voltage to the anode and cathode; a step of electrolytic-polishing the subject with the first plasma; a step of generating second plasma by applying a lower voltage than the voltage applied in the step of generating the first plasma; and a step of electrolytic-polishing the subject with the second plasma. The step of electrolytic-polishing the first plasma is performed in an area with a high voltage of 380 V or more. The step of electrolytic-polishing the second plasma is performed in an area with a low voltage of 370 V or less.

Description

Plasma Electrolytic Polishing Method with Luster and Dimensional Stability}

The present invention relates to a plasma electropolishing method capable of gloss and dimensional stability, and more particularly, to providing a technique in which a plasma electrolytic polishing method is constructed in two stages by a method of maintaining a product dimension at the same time as desired surface gloss. will be.

Most metal products are manufactured into final product shapes through machining, welding and forming processes, including heat treatment. After the shape is completed, the metal surface is modified to desired surface properties through various surface treatment methods such as painting and plating according to the purpose. Polishing is often applied to apply additional surface treatments such as the appearance of metal products, or plating. In general, the most widely used polishing method is electropolishing, which makes the surface smooth with surface gloss by electrochemical method.

Electropolishing is the reverse process of plating, and the recent development of industries that require cleanliness, such as semiconductor business, requires the precision and cleanliness of materials at the same time. There is a need for electropolishing, a new non-contact polishing method away from processing. Existing mechanical machining methods have left traces of micro-processing on the workpiece surface, resulting in a near clean surface.

In general, electropolishing is performed by applying a voltage between the anode and the cathode by using a metal product dissolved in an electrolyte as an anode and using an insoluble metal as a cathode. It is a method of polishing the surface of a metal product by melting (oxidizing) it. In order to polish a metal product using electrolytic polishing, an electrolytic solution is filled in an electrolytic cell, a product to be polished is installed as an anode, a cathode which is not dissolved in the electrolyte is installed, and a DC or pulse wave is formed between the anode and the cathode. Apply power. In electropolishing, when a current is applied even under conditions in which the metal product is not easily dissolved in the electrolyte, the metal product is forcibly dissolved little by little. As the electropolishing progresses, the convex portion concentrates the current more than the concave portion, so that dissolution occurs more quickly, and eventually the surface of the product is smoothed overall.

As described above, by selectively dissolving the micro-parts of the metal surface, the surface of the metal product can be smoothed (polishing) as well as the effect of gloss, appearance improvement, reflection and corrosion resistance, surface stress relaxation and scale removal according to the purpose. Can be.

However, the electropolishing method also causes a lot of losses in the material to be polished to achieve the desired surface smoothness. In this case, the surface state can be obtained at a desired level, but a change may occur in the dimensions and shape of the processed product due to material loss during polishing, which may cause a defect.

Another problem is that electropolishing uses toxic chemicals as the polishing liquid (electrolyte) used for smooth polishing. For example, the most commonly used chemicals for electropolishing are phosphoric acid (H ₃ PO ₄ ), which requires a lot of washing operations due to its viscous nature as well as its stability due to toxicity.

Accordingly, plasma electropolishing technology has been studied as a polishing method for solving these problems and maintaining surface gloss while maintaining dimensional stability due to material loss. The biggest difference between the plasma electropolishing and the conventional electropolishing is the range of applied voltage values. In the case of electropolishing, a voltage within 50V is generally applied. However, in the case of plasma electropolishing, a high voltage of at least 250V is applied to the electrolytic polishing. Generate a plasma.

Japanese Laid-Open Patent JP 2016-037622 A

The technical problem to be achieved by the present invention is to provide the effect of maintaining the dimensional stability without material loss by using a two-stage plasma electropolishing method to solve the problem of material loss when modifying the surface of the metal product by electropolishing in the prior art will be.

More specifically, the plasma electropolishing method is used in electrolytic polishing of metals and is composed of two stages with different voltage ranges.

The two-stage plasma electropolishing of the present invention ensures dimensional stability and at the same time reduces the surface roughness and obtains the surface gloss effect.

In addition, to solve the problem of environmental pollution by using a polishing liquid toxic in the case of conventional electropolishing using a polishing liquid that does not contain chemical toxicity.

The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

In order to achieve the above technical problem, an embodiment of the present invention provides a plasma electrolytic polishing method. The plasma electropolishing method includes the steps of preparing an object, installing an anode and a cathode in an electrolyte, and connecting the object to an anode, the anode and the cathode. Generating a first plasma by applying a voltage to the substrate, subjecting the object to the first plasma by electropolishing, and generating a second plasma by applying a voltage lower than that applied in the generating of the first plasma. And electrolytic polishing the object with the second plasma, wherein the first plasma electropolishing treatment is performed in a high voltage region of 380V or more, and the second plasma electropolishing treatment is 370V or less. It may be characterized in that performed in the low voltage region.

In addition, the object is characterized in that it comprises a stainless steel, Ni alloy, Cu alloy or Co-Cr alloy.

In addition, the electrolyte solution is characterized in that it comprises ammonium sulfate, potassium hydroxide or sodium hydroxide.

In addition, the pH of the electrolyte is characterized in that 4 to 8.

The molar concentration of ammonium sulfate, potassium hydroxide or sodium hydroxide in the electrolyte solution is characterized in that 0.01 M to 1 M.

In addition, the temperature of the electrolyte is characterized in that 20 ℃ to 90 ℃.

In addition, the high voltage region of the first plasma electropolishing is characterized in that the 380V to 500V.

In addition, the step of generating the first plasma is characterized in that performed for 20 seconds to 10 minutes.

In addition, the low voltage region of the second plasma electropolishing is characterized in that the 260V to 370V.

In addition, the step of generating the second plasma is characterized in that performed for 20 seconds to 5 minutes.

In order to achieve the above technical problem, another embodiment of the present invention provides a metal material prepared by electropolishing by the above-described plasma electropolishing method.

According to the embodiment of the present invention, it is possible to obtain the effect of solving the problem of wastewater generation and the environmental pollution of the washing operation due to the stability and viscosity from toxicity by using an electrolyte solution without toxicity and viscosity.

In addition, it is possible to obtain the effect of having the gloss and dimensional stability of the metal material at the same time through the plasma electropolishing composed of two stages.

In addition, the surface of the metal material through the plasma electropolishing can obtain an effect of high adhesion.

In addition, plasma electropolishing can provide an effect of providing corrosion resistance, heat resistance, and wear resistance of the surface of the metal material.

In addition, plasma electropolishing removes hydrogen which induces bacterial growth on the surface of the metal material, thereby reducing the surface loss.

The effects of the present invention are not limited to the above-described effects, but should be understood to include all the effects deduced from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a flowchart of a plasma electropolishing method.
2 is a diagram showing the degree of loss of raw materials during electrolytic polishing and plasma electropolishing.
3 is a graph showing a range of voltage values applied in electropolishing and plasma electropolishing.
4 is a photograph showing dimensional deformation generated during plasma electropolishing in a low voltage region.
5 is a photograph showing the degree of surface gloss obtained during plasma electropolishing in a high voltage region.
6 is a photograph showing the product quality obtained when the two-stage plasma electropolishing method is applied.

Hereinafter, with reference to the accompanying drawings will be described the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to be "connected (connected, contacted, coupled)" with another part, it is not only "directly connected" but also "indirectly connected" with another member in between. "Includes the case. In addition, when a part is said to "include" a certain component, this means that it may further include other components, without excluding the other components unless otherwise stated.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described on the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

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

1 is a flow chart showing a plasma electropolishing method according to an embodiment of the present invention.

Referring to FIG. 1, in the plasma electrolytic polishing method according to an embodiment of the present invention, preparing an object (S100), an anode and a cathode are installed in the electrolyte, and the object is placed on the anode. Connecting (S200), applying a voltage to the anode and the cathode to generate a first plasma (S300), and subjecting the object to the first plasma by electrolytic polishing (S400). And generating a second plasma by applying a voltage lower than that applied in the first plasma generating step (S500) and subjecting the object to the second plasma by electropolishing (S600). The first plasma electropolishing may be performed in a high voltage region of 380V or more, and the second plasma electropolishing process may be performed in a low voltage region of 370V or less.

First, prepare a target object (S100).

For example, the object may include stainless steel, Ni alloy, Cu alloy or Co—Cr alloy. However, the present invention is not limited thereto.

In addition, when the subject is not easily dissolved in the electrolyte and a current is applied, the subject may be forcibly dissolved little by little.

Next, an anode and a cathode are installed in the electrolyte and the object is connected to the anode (S200).

The electrolyte may be characterized by containing ammonium sulfate, potassium hydroxide or sodium hydroxide.

In addition, the pH of the electrolyte may be characterized in that 4 to 8.

The electrolyte solution may be configured to add an environmentally friendly electrolyte solution only by adding a small amount of salt to the conductivity of the electrolyte and stability of the generated plasma compared to the electrolyte used in the conventional electrolytic polishing.

In addition, it uses a toxic and viscous electrolyte in the prior art, there is a lot of loss of the liquid buried in the product produced by electropolishing, wastewater treatment costs as a large amount of pollutants such as chromic acid, sulfuric acid and phosphoric acid flow into the wastewater treatment plant Can provide the effect of solving the high disadvantage and environmental pollution problem.

In addition, since the acidity range and the neutral range electrolyte are used, the post-treatment process generated when acidic or basic is used can be shortened.

In addition, the molar concentration of the electrolyte may be characterized in that 0.01M to 1M.

If the molar concentration of the electrolyte is less than 0.01M can lose the role of the electrolyte to play the role of conductance to increase the threshold voltage, the discharge can occur, the greater than 1M is large and deep pores are formed on the surface of the object to increase the volume of pores Corrosion resistance may deteriorate.

In addition, the temperature of the electrolyte may be characterized in that 20 ℃ to 90 ℃.

When the temperature of the electrolyte is less than 20 ℃ reaction rate is lowered to suppress the electropolishing reaction, when the temperature exceeds 90 ℃ water starts to boil unstable plasma generation. Therefore, it may be appropriate to maintain the temperature of the electrolyte at 20 ° C to 90 ° C.

In addition, the object is connected to the anode, and a metal insoluble in the electrolyte is connected to the cathode.

The object may be connected to an anode to cause electrolysis at the surface of the object, thereby polishing the surface.

Next, a voltage is applied to the anode and the cathode to generate a first plasma (S300).

When the first plasma is generated, since the convex portion concentrates the current more than the concave portion, dissolution occurs more quickly, and the surface of the object is smoothed as a whole, so that the desired roughness can be obtained and the dimensional stability can be improved.

The high voltage region of the first plasma electropolishing may be 380V to 500V.

In the high voltage region 380V to 500V of the first plasma electropolishing, the plasma will be homogeneously formed, and thus the roughness can be reduced while maintaining the dimensional stability because the surface roughness is reduced by the formed plasma.

Next, the subject is subjected to electropolishing with the first plasma (S400).

Generating the first plasma may be performed in 20 seconds to 10 minutes.

If the time for generating the first plasma is less than 20 seconds, the roughness of the surface of the object cannot be sufficiently lowered, and if it exceeds 10 minutes, not only the dimensional change of the object is severe, but also the polishing is excessive, thereby increasing the surface roughness again. do.

Next, a second plasma is generated by applying a voltage lower than the voltage applied in the first plasma generation step (S500).

The low voltage region of the second plasma electropolishing may be 260V to 370V.

The roughness can be lowered while maintaining the dimensional stability by the electropolishing treatment by the first plasma, but there is a problem that the gloss effect is inferior.

On the other hand, the second plasma generated in the low voltage region of 260V to 370V is relatively less generated than the first plasma, so that the surface of the object is melted by the electrolyte and exhibits glossiness rather than reducing the roughness. Bigger

Therefore, when the second plasma treatment described later after lowering the illuminance while maintaining the dimensional stability by the first plasma treatment, there is an advantage that the gloss effect can be simultaneously obtained.

In addition, in the conventional electropolishing technique, a voltage is applied within 50V, but in the case of plasma electropolishing, since the minimum voltage required for plasma formation is 250V, plasma electropolishing may not occur at a voltage of less than 250V.

Next, the subject is subjected to electropolishing with the second plasma (S600).

Generating the second plasma may be performed in 20 seconds to 5 minutes.

 If the time for generating the second plasma is less than 20 seconds, the surface roughness of the object cannot be sufficiently lowered. If the second plasma is longer than 5 minutes, the surface roughness is increased again due to excessive dimensional change and excessive polishing. do.

Since the second plasma is generated in the low voltage region of 260V to 370V and is generated relatively less than the first plasma, the second plasma melts the surface of the target object by the electrolyte solution and exerts the gloss more than the effect of reducing the roughness. Big.

Therefore, using the two-stage plasma electropolishing method of the present invention including the first plasma electropolishing step (S400) and the second plasma electropolishing step (S600) of the present invention, it is possible to measure dimensions without material loss in the first plasma electropolishing step. It is possible to maintain stability and reduce roughness and to obtain gloss on the subject through the second plasma electropolishing step, thereby simultaneously reducing surface roughness, maintaining dimensional stability, and expressing gloss.

In addition, performing the second stage electrolytic polishing of the present invention through the reaction time range of 20 seconds to 10 minutes of the first plasma electrolytic polishing step (S400) and 20 seconds to 5 minutes of the second plasma electrolytic polishing step (S600). It can be seen that the shape of the film, the film thickness is proportional to the time to perform the electrolytic polishing, and the adhesion and the like affects all aspects such as surface roughness, surface hardness, wear resistance, corrosion resistance.

In addition, the surface loss due to bacteria can be reduced by removing hydrogen on the surface of the object through the two-stage plasma electropolishing of the present invention.

Therefore, the effect of two-stage plasma electropolishing reduces dimensional stability, roughness reduction effect, gloss, adhesion, corrosion resistance, heat resistance, abrasion resistance, and metal surface by removing hydrogen that induces bacterial growth, thereby reducing surface loss caused by bacteria. You can get it.

Production Example

1) The electrolytic cell was filled with ammonium sulfate (NH ₄ ) ₂ SO ₄ of 0.1 M of 40 ° C temperature electrolyte.

2) An anode and a cathode were installed in the electrolyte and stainless steel was connected to the anode.

3) The first plasma electropolishing was performed by applying a voltage of 380V to 500V.

4) A second plasma electropolishing was performed by applying a voltage of 260V to 370V.

5) Electrolytic polishing yielded stainless steel with gloss on the surface and dimensional stability.

2 is a diagram showing the degree of loss of raw materials during electrolytic polishing and plasma electropolishing.

Referring to FIG. 2, it can be seen that the conventional electropolishing has a large material loss in order to realize the smoothness of the surface while reducing the loss of the material and the surface roughness through plasma electropolishing.

3 is a graph showing a range of voltage values applied in electropolishing and plasma electropolishing.

Referring to FIG. 3, a voltage is generally applied within 50V of the conventional electropolishing, but it can be seen that plasma is generated in the electrolyte when operating by applying a voltage of at least 250V in the case of plasma electropolishing.

4 is a photograph showing dimensional deformation generated during plasma electropolishing in a low voltage region.

Referring to FIG. 4, when plasma electropolishing is performed in the low voltage region of 260V to 370V, the effect of glossing on the metal surface is greater than the polishing effect of decreasing roughness. In addition, it can be seen that the material loss is difficult to maintain the dimensional stability.

5 is a photograph showing the degree of surface gloss obtained during plasma electropolishing in a high voltage region.

Referring to FIG. 5, in the case of plasma electropolishing in the high voltage region of 280V to 500V of the present invention, the desired roughness is obtained in terms of roughness reduction and dimensional stability, and the dimensional stability is also high but the gloss effect is poor as shown in FIG. have.

6 is a photograph showing the product quality obtained when the two-stage plasma electropolishing method is applied.

Referring to FIG. 6, the surface to be obtained by obtaining the desired roughness in the first plasma electropolishing step of the present invention and the surface gloss in the second plasma electropolishing step is obtained through the two-stage plasma electropolishing of the present invention. It can be seen that the metal material embodied at the same time (roughness, gloss) and the dimensions of the manufactured product can be obtained.

Therefore, when comparing FIG. 4 and FIG. 5 with FIG. 6, it can be confirmed that different effects of the surface gloss effect of FIG. 4 and the high dimensional stability effect of FIG. 5 are simultaneously obtained.

According to the embodiment of the present invention, it is possible to obtain the effect of solving the problem of wastewater generation and the environmental pollution of the washing operation due to the stability and viscosity from toxicity by using an electrolyte solution without toxicity and viscosity.

In addition, it is possible to obtain the effect of having the gloss and dimensional stability of the metal material at the same time through the plasma electropolishing composed of two stages.

In addition, the surface of the metal material through the plasma electropolishing can obtain an effect of high adhesion.

In addition, plasma electropolishing can provide an effect of providing corrosion resistance, heat resistance, and wear resistance of the surface of the metal material.

In addition, plasma electropolishing removes hydrogen which induces bacterial growth on the surface of the metal material, thereby reducing the surface loss.

The effects of the present invention are not limited to the above-described effects, but should be understood to include all the effects deduced from the configuration of the invention described in the detailed description or claims of the present invention.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is represented by the following claims, and it should be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.

Claims (11)

Preparing a subject;
Installing an anode and a cathode in the electrolyte and connecting the object to the anode;
Applying a voltage to the anode and the cathode to generate a first plasma;
Electropolishing the object with the first plasma;
Generating a second plasma by applying a voltage lower than that applied in the first plasma generating step; And
Electrolytically polishing the object with the second plasma,
The first plasma electrolytic polishing step is performed in a high voltage region of 380V or more, and the second plasma electrolytic polishing process is performed in a low voltage region of 370V or less. The method of claim 1,
The object is plasma electropolishing method characterized in that the stainless steel, Ni alloy, Cu alloy or Co-Cr alloy. The method of claim 1,
The electrolytic solution is plasma electrolytic polishing method comprising ammonium sulfate, potassium hydroxide or sodium hydroxide. The method of claim 1,
PH of the electrolytic solution is a plasma electrolytic polishing method, characterized in that 4 to 8. The method of claim 3,
The molar concentration of ammonium sulfate, potassium hydroxide or sodium hydroxide in the electrolyte solution is 0.01 M to 1 M plasma electrolytic polishing method. The method of claim 1,
Plasma electrolytic polishing method, characterized in that the temperature of the electrolyte solution is 20 ℃ to 90 ℃. The method of claim 1,
The high voltage region of the first plasma electropolishing polishing is 380V to 500V. The method of claim 1,
The step of generating the first plasma electrolytic polishing method, characterized in that performed for 20 seconds to 10 minutes. The method of claim 1,
The low-voltage region of the second plasma electropolishing polishing method is characterized in that the 260V to 370V. The method of claim 1,
Generating the second plasma is electrolytic polishing method, characterized in that performed for 20 seconds to 5 minutes. A metal material produced by electropolishing by the electropolishing method of claim 1.

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