KR101109745B1 - Method for treating surface of workpiece with microwave - Google Patents

Abstract

The present invention discloses a method for surface treatment of a workpiece using microwaves for treating the surface of the workpiece using electric charge induced by a microwave to a target having electrical conductivity. The present invention prepares a workpiece, and provides a target having electrical conductivity on the surface of the workpiece. The target is irradiated with microwaves, and heat and sparks are generated from the target by irradiation of microwaves to form fine bends on the surface of the workpiece. According to the present invention, heat can be generated only in the local area of the workpiece by using electric charges induced by the microwave to the target having electrical conductivity to induce a small change on the surface, thereby efficiently performing the surface treatment of the workpiece. Can be. In addition, by forming a layer having a high electrical conductivity on a part of the surface of the workpiece to reduce the electrical contact resistance, there is an effect that can control the surface roughness by minimizing damage to the workpiece.

Description

Surface treatment method of workpiece using microwaves {METHOD FOR TREATING SURFACE OF WORKPIECE WITH MICROWAVE}

The present invention relates to a method for treating a surface of a workpiece using microwaves, and more particularly, to a workpiece (using a charge induced in a target having electrical conductivity by microwaves). The present invention relates to a surface treatment method of a workpiece using a microwave for treating the surface of the workpiece.

In various fields, such as automobiles, ships, aircrafts, construction, and the like, mechanical bonding such as bolting and riveting, adhesion, welding, and the like are widely used. Bonding is advantageous in that the bonding portion of the material is thin and the load is widely distributed compared to the mechanical bonding. Therefore, the adhesive is used in the field where it is difficult to apply a mechanical coupling method such as aircraft, ships.

Since the adhesion performance varies greatly depending on the surface precision of the material, surface treatment of the material is performed before adhesion. Surface treatment of materials for adhesion is divided into mechanical and chemical surface treatment methods. The mechanical method removes the surface layer of the material by sandpaper and sand blasting or adjusts the roughness. Chemical surface treatment method is to treat the surface of the material by chemicals such as acid (Acid), primer (Primer).

The purpose of this surface treatment is to remove foreign substances on the surface of the material and to control the surface roughness to increase the adhesion area on the micro scale and to have a mechanical interlocking structure. Another purpose of surface treatment is to reduce the electrical contact resistance between two objects. At the point of contact between two objects acting as a passage through which electricity flows, such as an electric switch, the contact form at a small scale becomes an important factor in determining the electrical contact resistance. When the electrical contact resistance is high, spark and heat are generated when two objects are contacted, which damages the material and consumes electrical energy, thereby decreasing efficiency. Therefore, surface treatment of objects is very important even when there are electrical contacts. A widely used method is to coat a gold film with a relatively low resistance against corrosion and to achieve a suitable level of surface roughness by mechanical methods.

As described above, the mechanical and chemical surface treatment methods used in the process for lowering the adhesion and the electrical contact resistance have a disadvantage in that it takes a long time. In particular, the mechanical surface treatment method is not suitable for thin materials or materials that are susceptible to deformation, since the surface of the material is greatly damaged or causes deformation. The chemical surface treatment method has a disadvantage in that workability is lowered because it uses a dangerous substance such as an acid. The thin film coating used to lower the electrical contact resistance between two objects is expensive because expensive metal such as gold is used, and the electrical contact resistance is greatly increased when the coating is damaged.

The present invention has been made to solve the above problems, and an object of the present invention is to generate heat only on the local area of a workpiece by using electric charges induced by a microwave to a target having electrical conductivity. The present invention provides a method for surface treatment of a workpiece using microwaves to induce a change.

Another object of the present invention is to provide a method for surface treatment of a workpiece using microwaves which can reduce the electrical contact resistance by forming a layer having a high electrical conductivity on a part of the surface of the workpiece.

Still another object of the present invention is to provide a method for treating a surface of a workpiece using microwaves which can minimize surface damage to control surface roughness.

A feature of the present invention for achieving the above object comprises the steps of preparing a workpiece; Providing a target having electrical conductivity on the surface of the workpiece; Irradiating the target with microwaves; The present invention relates to a method for surface treatment of a workpiece using microwaves, which generates heat and sparks from a target by irradiation of microwaves to form fine bends on the surface of the workpiece.

Another feature of the present invention is to prepare a workpiece; Providing a target composed of carbon powder on the surface of the workpiece, the target having electrical conductivity; Irradiating the target with microwaves; Workpieces using microwaves comprising the step of generating heat and sparks from the target by irradiation of microwaves to form fine bends on the surface of the workpiece and at the same time forming an oxide layer which can lower the electrical contact resistance on the surface of the workpiece. In the surface treatment method.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments with reference to the accompanying drawings.

Hereinafter, preferred embodiments of the surface treatment method of the workpiece using the microwave according to the present invention will be described in detail with reference to the accompanying drawings.

First, referring to FIG. 1, the surface treatment method of the workpiece using the microwave according to the present invention may include the surface 32 of the workpiece 30 by the microwave generator 10 and the target 20 having electrical conductivity. ). The microwave generator 10 has a chamber 12. A magnetron 14 generating microwaves 2 is installed at one side of the chamber 12, and a table 16 on which the target 20 and the workpiece 30 can be placed in the chamber 12. Is installed. The microwave 2 is distributed in the chamber 12 by the operation of the stirrer 18 and irradiated to the target 20. The target 20 may be formed of, for example, metal, carbon, or the like.

The microwaves 2 generated by the operation of the magnetron 14 form a microwave field in the chamber 12. The microwave 2 for heating the workpiece 30 has a frequency of 2.45 GHz and an intensity of 1 kW or more. When the target 20 having electrical conductivity is placed in the microwave field, electric charge is induced inside the target 20 to raise the temperature. In addition, when the target 20 reaches a potential at which ions can be reduced by irradiation of the microwaves 2, sparks are generated from the target 20. In particular, when the target 20 is composed of particles having a small size of powder (Power), that is, metal powder or carbon powder, heat and sparks are independently generated around each of the particles.

2 and 3, the target 120 is made of a powder having electrical conductivity or ceramic materials in which powders are mixed. The target 120 of the powder or ceramic material may be formed in a plate type or a pin type by various methods such as compression molding and sintering. The target 120 may be in close contact with the surface 32 of the workpiece 30 by applying a pressing force. The target 120 may be disposed to generate static electricity in the workpiece 30 and to stick to the surface 32 of the workpiece 30. In addition, the target 120 may be spaced from the surface 32 of the workpiece 30.

The microwaves 2 are irradiated onto the targets 120 by the operation of the microwave generator 20 shown in FIG. 1 with the targets 120 disposed on the surface 32 of the workpiece 30. In this case, the target 120 has a potential by induction of charge. As a result, the temperature of the target 120 is increased, and the spark 4 is generated from the target 120. The spark 4 is generated in each powder particle of the target 120, and is also generated by the space | interval of the agglomerated powder particle. At this time, the foreign matter 6 contaminated on the surface 32 of the workpiece 30 by the high temperature of the spark (4) is evaporated or burned into fine particles (8) to be removed.

In addition, a fine curve 34 is formed on the surface 32 of the workpiece 30 due to the high temperature of the spark 4 to control the surface roughness. In the case of a composite material whose surface of the workpiece 30 is made of a polymer, the surface of the polymer is locally burned finely to form a bend. When the workpiece 30 is made of metal, the metal is melted to control the surface roughness. Oxidation layer on the metal surface has the effect of heat treatment at high temperature. The electrically conductive material generally has a heat dissipation function by high thermal conductivity. The internal temperature of the electrically conductive material is prevented from reaching a high temperature upon irradiation of the microwave 2 by its heat radiation function. Therefore, the target 120 and the workpiece 30 are prevented from being damaged by the heat of the spark 4.

On the other hand, in the workpiece 30 of the metal, since the charge is induced by the reflection of the microwave 2 or the high electrical conductivity, sparks may be generated in addition to the portion of the surface treatment and damage may occur. The surface treatment method of the workpiece using the microwave according to the present invention is a material containing a liquid such as moisture, for example, moisture absorbing material that can absorb microwaves 2 or electric charges in a part of the metal during surface treatment of the metal. Is pressed against a portion of the metal. This absorber absorbs microwaves 2 or charges and prevents damage to the metal, ie workpiece 30, by charge concentration. Therefore, the surface treatment of the to-be-processed object 30 by the irradiation of the microwave 2 can be performed efficiently.

4, the surface treatment of the glass fiber composite material (Fiberglass composite: 130) as an example of the workpiece by the surface treatment method of the workpiece using the microwave according to the present invention. The glass fiber composite material 130 is impregnated with glass fibers in a matrix of a thermosetting resin such as a phenol resin, an epoxy resin, and a polyester resin, and then cured. It is made of a layer or sheet. In an embodiment of the present invention, the glass fiber may be made of conductive polymers such as carbon fibers having electrical conductivity and Kevlar fiber (trade name of DuPont, USA). The target 220 is made of carbon black. Carbon black is carbon powder whose particle size is several nm-several micrometers, and is a high molecular material. Carbon black is formed into a plate by compression molding.

The target 220 is pressed against one surface of the glass fiber composite material 130 by the operation of the microwave generator 10 shown in FIG. 1 on the target 220 and the glass fiber composite material 130. Irradiating the microwave 2 at 2.45 GHz and 1.2 kw for about 5 seconds generates a large number of bends 134 on the surface 132 of the glass fiber composite material 130. Therefore, the surface roughness of the glass fiber composite material 130 may be controlled by the surface treatment method of the workpiece using the microwave according to the present invention.

Figure 5a is a photomicrograph of the surface of the glass fiber composite material before the surface treatment by the surface treatment method of the workpiece using the microwave according to the present invention, Figure 5b is a microwave using a microwave according to the present invention Photomicrograph of the surface of the glass fiber composite material after surface treatment by the surface treatment method of the workpiece. Looking at the photos of the glass fiber composite material of Figures 5a and 5b, it can be seen that more bends 134 are formed on the surface of the glass fiber composite material subjected to the surface treatment than before the surface treatment. In addition, it can be confirmed that the locally burned oxide layer, that is, the burned carbon black particles 136, remains on the surface of the glass fiber composite material subjected to the surface treatment. Electrical contact resistance is lowered by the carbon black particles 136 remaining on the surface of the glass fiber composite material.

Referring to FIG. 6, a carbon fiber composite material 230 was treated as another example of the workpiece by the surface treatment method of the workpiece using the microwave according to the present invention. Carbon fiber composite material 230 is impregnated with carbon fibers in a matrix, and then cured to produce a layer or sheet. Carbon fiber of the carbon fiber composite material 230 has a high electrical conductivity, the matrix is a non-conductor.

The carbon fiber composite material 230 is composed of, for example, a bipolar plate 240 of a fuel cell. Separator 240 is composed of a waveform. The target 120 is made of carbon black. When the microwaves 2 are irradiated by the operation of the microwave generator 10 shown in FIG. 1 while the target 120 is in close contact with the surface 242 of the separating plate 240, the target 120 is applied. Many bends 244 are generated on the surface 242 of the contact plate 240 in close contact, and foreign substances contaminated on the surface 242 are removed. In addition, locally finely burned carbon black particles 246 remain on the surface 242 of the separator 240. The matrix of the carbon fiber composite material 230 is exposed to high temperature heat by sparks generated from the target 120. However, if the irradiation time of the microwave 2 is shortened, a heat radiation effect due to the high thermal conductivity of the target 120 is achieved. Damage to large areas of the matrix is prevented.

As shown in FIG. 7, when two separation plates 240 and 240 'surface-treated by the surface treatment method of the workpiece according to the present invention are bonded, the separation plates 240 and 240' are bonded. The burned carbon black particles 246 are interposed at the junction of these. The higher the volume fraction of the matrix at the junction where the surfaces 242 of the two separation plates 240, 240 ′ abut, the higher the electrical contact resistance and the lower the efficiency of the fuel cell. The electrical contact resistance between the separators 240 and 240 'is lowered by the carbon black particles 246.

Referring to Figure 8, according to the surface treatment method of the workpiece using the microwave according to the present invention was subjected to the surface treatment of the metal 330 as another example of the workpiece. The metal 330 is composed of an aluminum plate 340. The target 120 is comprised by carbon black in plate shape.

In order to prevent the aluminum plate 340 from being damaged by the spark 4 on the back surface of the aluminum plate 340, a paper 42 containing water is attached as an example of the absorber 40. When the microwaves 2 are irradiated by the operation of the microwave generator 10 shown in FIG. 1 while the target 120 is in close contact with the surface 342 of the aluminum plate 340, the aluminum plate ( Fine bends 344 are formed in the surface 342 of 340.

Figure 9a is a photomicrograph of the surface of the aluminum plate before the surface treatment by the surface treatment method of the workpiece using the microwave according to the invention, Figure 9b is a workpiece of the workpiece using the microwave according to the present invention It is the photograph which photographed the surface of the aluminum plate after surface treatment by the surface treatment method. Looking at the photos of the glass fiber composite material of Figures 9a and 9b, it can be seen that more bends are formed on the surface of the aluminum plate subjected to the surface treatment than before the surface treatment. In addition, it can be seen that the carbon black particles 346 locally finely burned remain on the surface of the aluminum plate subjected to the surface treatment. The electrical contact resistance is lowered by the carbon black particles 346 remaining on the surface of the aluminum plate.

The embodiments described above are merely to describe preferred embodiments of the present invention, the scope of the present invention is not limited to the described embodiments, those skilled in the art within the spirit and claims of the present invention It will be understood that various changes, modifications, or substitutions may be made thereto, and such embodiments are to be understood as being within the scope of the present invention.

As described above, according to the surface treatment method of the workpiece using the microwave according to the present invention, the surface is generated by generating heat only in the local area of the workpiece by using the electric charge induced by the microwave to the target having electrical conductivity. By inducing microscopic changes, the surface treatment of the workpiece can be efficiently performed. In addition, by forming a layer having a high electrical conductivity on a part of the surface of the workpiece to reduce the electrical contact resistance, there is an effect that can control the surface roughness by minimizing damage to the workpiece.

1 is a cross-sectional view showing an example of the microwave generating apparatus applied to the surface treatment method of the workpiece using the microwave according to the present invention,

Figure 2 is a cross-sectional view for explaining the surface treatment of the workpiece by the target composed of powder as an example of the target in the surface treatment method of the workpiece using the microwave according to the present invention,

Figure 3 is a partially enlarged cross-sectional view for explaining the surface treatment of the workpiece by the target consisting of powder in the surface treatment method of the workpiece using the microwave according to the present invention,

4 is a cross-sectional view showing the surface treatment of a glass fiber composite material as an example of the workpiece in the surface treatment method of the workpiece using the microwave according to the present invention;

5a and 5b are photographs before and after the surface treatment of the glass fiber composite material in the surface treatment method of the workpiece using the microwave according to the present invention,

6 is a cross-sectional view for explaining the surface treatment of the carbon fiber composite material as another example of the workpiece in the surface treatment method of the workpiece using the microwave according to the present invention;

7 is a cross-sectional view showing a state in which two separation plates surface-treated by the method for treating a workpiece using microwaves;

8 is a cross-sectional view illustrating another example of the workpiece in the surface treatment method of the workpiece using the microwave according to the present invention for explaining the surface treatment of the metal,

9A and 9B are photographs before and after the surface treatment of the aluminum plate in the surface treatment method of the workpiece using the microwave according to the present invention.

♣ Explanation of symbols for the main parts of the drawing

2: microwave 4: spark

10: microwave generator 20, 120, 220: target

30: Workpiece 32: Surface

40: absorber 130: glass fiber composite material

132: surface 134: bend

230: Carbon fiber composite material 240, 240 ': Separator

242: surface 244: bending

246: carbon black particles 330: metal

340: aluminum plate 342: surface

344: bend 346: carbon black particles

Claims (16)

Preparing a work piece; Providing a target having electrical conductivity on a surface of the workpiece; Irradiating microwaves to the target; And generating fine bends on the surface of the workpiece by generating heat and sparks from the target by irradiation of the microwaves. The surface treatment method according to claim 1, wherein the target is made of a powder of any one of metal and carbon. 3. The method of claim 2, wherein the powder is mixed with a ceramic material and molded. The surface treatment method according to claim 1, wherein the target is in close contact with the workpiece in the step of providing the target. The method of claim 4, wherein the workpiece is made of any one of a glass fiber composite material, a carbon fiber composite material, and a metal. 5. The method of claim 4, wherein an oxide layer is formed on the surface of the workpiece by generating heat and sparks from the target to reduce electrical contact resistance. 7. The method of claim 6, wherein the oxide layer is made of carbon black particles. 2. The method of claim 1, further comprising providing an absorber on the back surface of the workpiece to absorb the microwaves. The surface treatment method according to claim 8, wherein the absorber is made of paper containing water. Preparing a work piece; Providing a target composed of carbon powder on the surface of the workpiece having electrical conductivity; Irradiating microwaves to the target; Microwave comprising the step of generating heat and sparks from the target by the irradiation of the microwave to form fine bends on the surface of the workpiece and to form an oxide layer that can lower the electrical contact resistance on the surface of the workpiece Surface treatment method of the workpiece. The method of claim 10, wherein the carbon powder is mixed with a ceramic material and molded. The surface treatment method according to claim 10, wherein the target is in close contact with the workpiece in the step of providing the target. 13. The method of claim 12, wherein the workpiece is made of any one of a glass fiber composite material, a carbon fiber composite material, and a metal. The method of claim 10, wherein the oxide layer is made of carbon black particles. The surface treatment method according to claim 10, further comprising providing an absorber on the back surface of the workpiece to absorb the microwaves. The surface treatment method according to claim 15, wherein the absorbent body is made of paper containing water.

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