KR20090034474A - Electrode wire for electric discharge machining and manufacturing method thereof - Google Patents

Abstract

An electrode wire for an electric discharge machining and a manufacturing method thereof are provided to prevent generation of dust, disconnection and copper sticking to workpiece by performing high accuracy electric-discharge machining with uniform spark discharge. An electrode wire for an electric discharge machining is composed of core wires made of metal material and a coating layer formed on the surface of the core wire. A manufacturing method of an electrode wire for an electric discharge machining comprises: a step washing the core wire(S10); a step electroplating the washed core wire(S20); a step pretreating the electroplated core wire for hot dipping(S30); a step performing the hot dipping to the core wire and forming a coating layer(S40); and a step drawing the core wire in which the coating layer is formed(S50).

Description

Electrode wire for electric discharge machining and manufacturing method thereof

The present invention relates to an electrode wire for electric discharge machining and a method for manufacturing the same, and more particularly, electroplating and hot-dip galvanizing on a core wire sequentially to form a variety of coating layer structure and then wire drawing to produce an electrode electrode for electric discharge machining, excellent discharge characteristics It is related with the electrode wire for electric discharge machining which is high in tensile strength and is outstanding in precision machining, and its manufacturing method.

In general, the electric discharge machining is to cut the workpiece by sparking or arc discharge, and to cut the workpiece while the wire-shaped electrode line is maintained at an interval where the discharge occurs next to the workpiece. That is, the spark or arc discharge is generated by the electric current acting between the workpiece and the electrode to cut while finely removing metal particles while melting the workpiece.

Since the workpiece is cut by the discharge between the electrode wire and the workpiece, the shape and the material of the electrode wire such as the composition, phase, and diameter of the electrode wire have a great influence on the discharge machining.

In general, since the core of the electrode wire is formed of a low melting point metal having a low evaporation temperature, a phase change occurs due to a diffusion reaction between the core wire and the metal constituting the coating layer, thereby forming various coating layers. Since these phases have different physical and chemical properties, the performance of the electrode wire may vary greatly depending on the thickness of the phase to which the phase is formed in the coating layer.

Therefore, efforts to improve the performance of the electrode line on this basis is continuously progressed. In particular, if the characteristics of the electrode wire is not good, there may be powder generation, disconnection, eastern adhesion phenomenon that the brass of the core wire is attached to the workpiece during discharge processing, which can cause fatal damage in the mold processing. In addition, in order to maintain the surface roughness in the precision processing, it is necessary to minimize the occurrence of powder by forming a coating layer uniform in the state of the coating layer and a strong adhesion to the base material. In addition, the development of electrode wires considering the tensile strength, electrical conductivity, and evaporation characteristics during spark discharge, which are required for electrode wires during discharge processing, is required.

Therefore, the present invention is to solve the above problems, by electroplating and hot-dip galvanizing on the core wire in order to form a variety of coating layer structure and then wire drawing to manufacture the electrode wire for electrical discharge processing excellent discharge characteristics, high tensile strength and precision An object of the present invention is to provide an electrode wire for electric discharge machining and a method of manufacturing the same.

The present invention is a core wire formed of a metal material; And a coating layer formed on the surface of the core in a gamma + ε phase, wherein the coating layer penetrates into the surface of the core in the form of a statue.

In addition, the core wire is preferably formed of a copper or zinc alloy containing 30 to 43% by weight of zinc.

In addition, the coating layer preferably contains 70 to 76% by weight of zinc.

The present invention also provides a washing step for washing the core wire; An electroplating step of electroplating the washed core wires; A plating pretreatment step of performing pretreatment for hot dip plating on the electroplated core wires; Hot-dip plating step of forming a coating layer by performing a hot plating on the core wire pre-plated; And it provides a manufacturing method of the electrode line for electric discharge machining, characterized in that it comprises a drawing step of drawing the core wire formed with the coating layer.

In addition, the coating layer formed in the hot dip plating step is a first layer surrounding the core wire and formed in a γ phase; A second layer formed on the first layer in a γ + ε phase; And a third layer formed on any one of ε phase, ε + η phase or η phase on the second layer.

The electrode wire for electric discharge machining according to the present invention is manufactured by a mixed coating process of electroplating and hot dip plating, and is surrounded by a core layer surrounded by a coating layer composed of γ + ε phase, and the particles constituting the coating layer penetrate into the core wire surface. It is an electrode wire with excellent discharge characteristics with high tensile strength and excellent adhesion.

Therefore, according to the present invention, a high precision electric discharge machining is possible by uniform spark discharge during electric discharge machining, and there is provided an electrode electrode for electric discharge machining that can reduce powder generation, disconnection, and phenomenon of adhesion to the workpiece.

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

1 is a flowchart showing a method of manufacturing an electrode wire for electric discharge machining according to the present invention.

Referring to FIG. 1, an electroplating step (S20) is performed after a washing step (S10) including a degreasing step (S11), a washing step (S12), a pickling step (S13), and a washing step (S14) is performed on the prepared core wire. Is performed. Thereafter, a plating pretreatment step S30 including a flux step S31, a drying step S32, and a preheating step S33 is performed, followed by a hot dip plating step S40, and a drawing step S50 and a stress removing step. (S60) follows.

First, degreasing step (S11) is a process of removing the contaminants on the surface of the prepared core wire. If any contaminants, especially oil, remain on the surface of the core wire, problems such as poor adhesion and poor plating may occur in the subsequent electroplating step (S20) or the hot dip step (S40). It is to remove it in the degreasing step (S11).

In the washing step (S12) to wash the core wire using hot water of 30 to 50 ℃, in each process to maintain a low impurity concentration in the bath.

Pickling step (S13) is performed to remove the fine oxide scale on the surface of the core and to activate the surface of the core. At this time, it is preferable to perform the pickling step using an acid having an appropriate concentration and temperature in consideration of the characteristics of the core wire.

In the washing step (S14) to wash the core wire using hot water of 30 to 50 ℃, so that the bath can maintain a low impurity concentration in each process.

A galvanized layer is formed in the electroplating step (S20) on the core wire which has undergone the washing step (S10) as described above. First, a plated layer of pure zinc is formed on the washed core wire by electroplating. When zinc ions or zinc-dissolved electrolytes are prepared in a bath and the core wire is bathed in the bath and then energized, zinc is deposited on the core wire surface to form a pure zinc plated layer. This electroplating forms a plating layer of pure zinc on the surface of the core wire, thereby enabling the formation of a coating layer having a high zinc concentration during subsequent hot dip plating. That is, the adhesion of the coating layer to the base material is increased by forming a coating layer of γ + ε phase having a higher ductility than the γ phase due to the diffusion barrier effect during the hot dip plating process.

Thereafter, the plating pretreatment step S30 including the flux step S31, the drying step S32, and the preheating step S33 is performed on the electroplated core wire.

In the flux step S31, a flux is applied to the core wire surface to prevent oxidation of the core wire surface and to activate the surface. The applied flux is removed the moment it is bathed in the metal melt in the hot dip step (S40).

In the drying step (S32) to completely remove the moisture remaining in the flux, serves to prevent the adverse effects that the moisture in the flux in the hot dip step (S40) may have a coating.

In the preheating step (S33), by heating the core wire before the hot-dip plating step (S40), the diffusion in the hot-dip plating step (S40) can be actively generated to facilitate the formation of the coating layer.

After the plating pretreatment step S30 is performed as described above, the hot dip plating step S40 is performed. Hot-dip plating step (S40) is a process of forming a coating layer on the core wire while bathing the core wire in a bath in which zinc ions or zinc is dissolved. At this time, the temperature of the bath should be stabilized and the coating must be carried out in a constant state.

In addition, the thickness of the coating layer formed on the core wire in the molten plating step (S20) can be adjusted depending on the coating conditions, that is, the temperature of the molten metal, the coating time, etc. It is preferable to form a thickness of about 5 ~ 10㎛. However, since the thickness of the coating layer may vary depending on the characteristics of the desired electrode line, the present invention is not limited to the thickness of the coating layer.

In the present invention, the electroplating and the hot dip mixing are performed to form an electrode wire having excellent discharge processing characteristics through the subsequent drawing step (S30) by forming a coating layer having a plurality of layers different from each other.

In the hot-dip plating step (S40), the molten zinc is heated and heated at a high temperature of 450 ° C to 470 ° C to prepare a molten metal in a bath, followed by cooling the core wire pre-plated with electroplating as described above. As a result, a new coating layer is formed while the zinc of the molten metal is diffused into the electroplated core wire by reacting with the electroplated and plated core wire.

The coating layer is formed to be formed in the core wire through the hot dip plating step (S40) will be described later with reference to FIG.

After the hot-dip galvanizing step (S40) is a drawing step (S50) for drawing a core wire with a coating layer is formed. The drawing step S50 consists of a process of cold drawing the center wire electrode line (the electrode line formed before the drawing) using a drawing die to generate a thin wire electrode line (the electrode line after the drawing). In this case, the middle line electrode line of about 0.9 mm may be drawn out as a thin line electrode line of 0.25 mm. However, of course, it can be drawn to the thin wire electrode wire of various sizes according to a desired dimension.

After the drawing step S50 is performed, a stress removing step S60 for removing residual stress generated in the cold drawing process is performed. As a result, the tensile strength of the electrode wire and the adhesion of the surface of the electrode wire can be improved.

2 is a view schematically showing a cross section of the middle wire electrode line with a coating layer formed through the hot dip plating step (S40) according to the present invention.

First, after the electroplating step (S20) is carried out, the core wire 10 and zinc ions in the bath react to form a η-phase plated layer of pure zinc, and after the hot-plating step (S22), electroplating and plating pretreatment The coating layer 20 generated by reacting with the core wire 10 is formed of a plurality of layers having different phases. The first layer 21 is formed of γ phase, the second layer 22 is formed of γ + ε phase, and the third layer 23 is formed of an alloying coating layer composed of ε phase, ε + η phase, or η phase. In this case, the surface of the coating layer is formed of irregular dense tissue.

Table 1 below shows a phase analysis table of the heavy wire electrode line formed through the hot dip plating step (S40).

layer Core First layer Second layer Third layer Phase α or α + β γ γ + ε ε, ε + η or η Zn content (% by weight) - 65-68 70-76 80 or more

As shown in Table 1, the coating layer 20 is composed of three layers on the surface of the core wire 10, it can be seen that the phase of each layer is different.

At this time, the core wire 10 is preferably formed of an α phase or an α + β phase with a copper zinc alloy containing 30 to 43 wt% of copper or zinc. In general, when the zinc content exceeds 40% by weight, the α + β phase has a dual structure, and the β phase is difficult to be cold worked and tends to cause cracking or disconnection in the drawing step (S50). However, according to the present invention, the zinc content of the core wire 10 exceeds 40% by weight, but problems such as cracks and disconnection as in the prior art do not occur. This is because the coating layer 20 formed by sequentially performing electroplating and molten plating is more strongly adhered to the core wire 10 in the drawing step (S50), thereby increasing the adhesive strength and increasing the tensile strength, thereby improving the discharge machining characteristics. The core 10 may have a diameter of 0.85 to 1.25 mm, but the present invention is not limited to the diameter of the core.

In addition, since zinc in the bath diffuses into the core wire 10 to form a coating layer, the content of zinc decreases as the core 10 gets closer, and the third layer 23, which is the surface layer, is directly contacted with zinc of the molten metal. It is formed into an ε phase, ε + η phase or η phase containing higher zinc content than the portion, which contains 80% by weight or more of zinc.

The second layer 22 of the coating layer 20 is formed as a γ + ε layer of 3 ~ 7㎛ after remaining after the wire drawing step (S50) as a coating layer of the thin wire electrode line, the surface of the core wire 10 in the form of a statue Penetrates into.

Hereinafter, the electrode line for electrical discharge machining according to the present invention through the embodiment will be described in more detail.

Example

The core wire 0.9 mm in diameter was washed and electroplated with zinc. Flux coating, drying and preheating were performed on the electroplated core wire to perform pre-plating and hot dip plating to prepare a middle wire electrode wire having a coating layer. This middle wire electrode wire was cold drawn out with the die | dye for drawing, and the thin wire electrode wire of 0.25 mm in diameter was manufactured. In addition, the stress relief annealing heat treatment was performed at 400 ~ 500 ℃ to remove the residual stress generated during the cold drawing process.

3 is an enlarged image 100 times the surface of the center line electrode line after the electroplating is performed according to an embodiment of the present invention. That is, the surface photograph observed with the electron microscope after electroplating the core wire of diameter 0.9mm shows that the surface structure was formed in the (eta) phase which is pure zinc.

4 is a magnified image of the center line electrode line subjected to electroplating and hot dip plating according to an embodiment of the present invention. That is, the surface texture photograph observed by electron microscopy after electroplating and hot-dip coating of a core wire having a diameter of 0.9 mm indicates that the surface texture contained 92.22% by weight of zinc and formed into ε + η.

5 is an enlarged image of 3000 times a cross section of a middle wire electrode line sequentially subjected to electroplating and hot dip plating according to an embodiment of the present invention. That is, it shows the cross-sectional structure observed by electron microscopy after electroplating and hot-dip coating the core wire of diameter 0.9mm. The second layer (22 in FIG. 2) in the coating layer (20 in FIG. 2) of the cross-sectional structure shows that it was formed into a γ + ε phase containing 70.79% by weight of zinc.

6 is an enlarged image 300 times the surface of the thin wire electrode wire drawn in the drawing step according to an embodiment of the present invention. That is, the surface structure is composed of γ + ε phase and the surface structure is composed of γ + ε, and the zinc wire contains 75.47% by weight after the electroplating and hot-dip coating of 0.9 mm diameter core wire is carried out through the drawing step. .

7 is an image of an enlarged cross section of a thin wire electrode line drawn in a drawing step at 3000 times according to an embodiment of the present invention. That is, the cross-sectional structure of the thin wire electrode wire manufactured by 0.25 mm in diameter through the drawing step after electroplating and hot-dipling the core wire having a diameter of 0.9 mm is composed of γ + ε phase. In addition, the content of zinc is 71.87% by weight, the coating layer at the interface between the core wire and the coating layer can be seen to penetrate the surface of the core wire in the form of a statue. This increases the adhesion between the core wire and the coating layer as the mother wire, which significantly reduces the generation of powder during discharge processing and increases the tensile strength.

In general, the wire containing more than 40% by weight of zinc has a problem that the cracking and disconnection occurs during cold working is not possible to draw the wire. However, when the coating layer consisting of a plurality of layers is formed by electroplating and hot-dip plating as in the present invention, the third layer, which is the surface layer, is removed during the drawing process, and the second layer, which is the intermediate coating diffusion layer, is naturally pushed into the core surface. It is separated into forms and penetrates the core. Accordingly, the adhesion between the coating layer and the core wire is increased and the tensile strength is increased. In this case, since the second layer of the coating layer is formed of a soft γ + ε phase with a high zinc content, it is more advantageous than the γ phase for improving the adhesive force with the bus bar and the evaporation temperature is low, thereby improving the discharge effect.

This improvement in adhesion has the effect of suppressing the generation of powder during electrical discharge machining and contributes to improving the tensile strength of the electrode wire.

Although the above has been illustrated and described with respect to preferred embodiments of the present invention, the present invention is not limited to the above-described specific embodiments, and those skilled in the art without departing from the gist of the present invention. Anyone can make various modifications, as well as such modifications or variations are within the scope of the appended claims.

1 is a flowchart showing a method of manufacturing an electrode wire for electric discharge machining according to the present invention.

2 is a view schematically showing a cross section of the center line electrode line with a coating layer according to the present invention.

3 is a magnified image of the surface of an electroplated middle wire electrode line 100 times according to an embodiment of the present invention.

4 is an image of an enlarged 100 times the surface of the center line electrode line is sequentially subjected to electroplating and hot dip plating according to an embodiment of the present invention.

5 is an enlarged image of 3000 times a cross section of a middle wire electrode line sequentially subjected to electroplating and hot dip plating according to an embodiment of the present invention.

6 is an enlarged image 300 times the surface of the thin wire electrode wire drawn in the drawing step according to an embodiment of the present invention.

7 is an image of an enlarged cross section of a thin wire electrode line drawn in a drawing step at 3000 times according to an embodiment of the present invention.

Claims (7)

Core wire formed of a metallic material; And A coating layer formed on the surface of the core wire in a γ + ε phase, The coating layer is an electrode wire for electrical discharge machining, characterized in that the penetration into the surface of the core wire in the form of a statue. The electrode wire for electrical discharge machining according to claim 1, wherein the core wire is formed of copper or a zinc alloy containing 30 to 43% by weight of zinc. The electrode line for electric discharge machining according to claim 1, wherein the coating layer contains 70 to 76% by weight of zinc. A washing step of washing the core wires; An electroplating step of electroplating the washed core wires; A plating pretreatment step of performing pretreatment for hot dip plating on the electroplated core wires; Hot-dip plating step of forming a coating layer by performing a hot plating on the core wire pre-plated; And And a drawing step of drawing the core wire in which the coating layer is formed. The method of claim 4, wherein The coating layer formed in the hot dip step A first layer surrounding the core wire and formed in a gamma phase; A second layer formed on the first layer in a γ + ε phase; And The manufacturing method of the electrode line for electrical discharge machining containing the 3rd layer formed in any one of the phase (epsilon), (epsilon) + (eta) phase, or (eta) phase on the said 2nd layer. The method of claim 4, wherein the core wire is formed of copper or a zinc alloy containing 30 to 43% by weight of zinc. The method according to claim 5, wherein the coating layer having a plurality of layers formed in the hot dip plating step is changed to a coating layer of γ + ε having a single layer in the drawing step, The changed coating layer is a manufacturing method of the electrode line for electrical discharge machining, characterized in that the penetration into the surface of the core wire in the form of a statue.

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