WO2020122620A1 - Electrode tip for spot welding, and method for manufacturing same - Google Patents

Abstract

Disclosed is a method for manufacturing an electrode tip for spot welding, the method comprising: an arrangement step for arranging the tip of a rod-shaped copper alloy material and the tip of a rod-shaped tungsten alloy material so as to contact each other; a first insertion step for pressing the tungsten alloy material toward the copper alloy material while rotating the copper alloy material; and a second insertion step for pressing the tungsten alloy material toward the copper alloy material while the rotation of the copper alloy material is stopped.

Description

Electrode tip for spot welding and its manufacturing method

The present invention relates to an electrode tip for spot welding and a method for manufacturing the same. More specifically, the present invention relates to an electrode tip for spot welding and a method of manufacturing the same, which can improve the electrode life by bonding a copper alloy material and a tungsten alloy material using rotational friction bonding.

In spot welding of a plated steel sheet, the life of the electrode is rapidly reduced, which incurs a lot of cost from the manufacturer's point of view.

For this reason, many companies and research institutes at home and abroad continue research and development to prolong the life of the electrode tip, but there are no breakthrough reports yet.

In the conventional case, the sintered particles of tungsten powder were 3 μm or less, and the thermal conductivity of the electrodes was 60 W/mK or more. This method has the feature that the particles of tungsten powder are made small and an appropriate sintering process is applied to increase the thermal conductivity, but it has to undergo various processing processes and has a disadvantage in that the powder price is high.

In addition, there is a technique to apply a coating process to the tip of the electrode to form a coating layer on the Cu surface of the electrode material, and to apply methods to suppress the alloy reaction with the metal to be joined. This method is intended to extend the life of the electrode by forming a barrier on the surface of the electrode through coating to protect the electrode material, Cu. The electrode manufacturing through such a coating process has a disadvantage in that it is difficult to significantly extend the life of the electrode because the life of the coating layer immediately reaches its limit.

Provided is an electrode tip for spot welding that can improve electrode life by bonding copper alloy materials and tungsten alloy materials using rotational friction bonding, and a method for manufacturing the same.

A method of manufacturing an electrode tip for spot welding according to an embodiment of the present invention includes an arrangement step of disposing a tip of a rod-shaped copper alloy material and a tip of a rod-shaped tungsten alloy material in contact with each other; A first insertion step of pressing the tungsten alloy material toward the copper alloy material while rotating the copper alloy material; And a second inserting step of pressing the tungsten alloy material toward the copper alloy material while the rotation of the copper alloy material is stopped.

In the arranging step, the cross-sectional area of the copper alloy material is larger than that of the tungsten alloy material, and the front end of the copper alloy material may be positioned at the center of the front end of the copper alloy material.

In the first insertion step, the speed for rotating the copper alloy material may be 1000 to 1500rpm.

In the first insertion step, the temperature at the tip of the copper alloy material and the tip of the tungsten alloy material may be increased to 700 to 900°C by rotation of the copper alloy material.

In the first insertion step, the pressure when the tungsten alloy material is pressed toward the copper alloy material may be 0.4 to 0.8 PSI.

In the second insertion step, the pressure when the tungsten alloy material is pressed toward the copper alloy material may be 1.0 to 1.4 PSI.

In the first insertion step and the second insertion step, the length in which the tungsten alloy material is inserted into the copper alloy material may be 2 to 6 mm.

A cutting step of cutting a portion of the tungsten alloy material that is not inserted into the copper alloy material after the second inserting step; And a processing step of surface-processing a portion in which the copper alloy material and the tungsten alloy material are joined.

An electrode tip for spot welding according to an embodiment of the present invention includes an electrode body portion made of a copper alloy material; And an electrode tip portion made of a tungsten alloy material inserted into an end portion of the electrode body portion, wherein one surface of the outer surface of the electrode tip portion is in contact with a tip of the electrode body portion to form a bonding interface, and the other surface of the outer surface of the electrode tip portion is It is exposed outside.

The length of the electrode tip portion inserted into the electrode body portion may be 2 to 6 mm.

The electrode body portion may contain 3% by weight or less of chromium (Cr), the remaining copper (Cu), and unavoidable impurities with respect to 100% by weight.

The electrode tip portion may include at least one of tungsten (W), tungsten carbide (WC), and carbide (W-Co).

According to the electrode tip for spot welding according to an embodiment of the present invention and a method of manufacturing the same, it may be possible to improve the life of the electrode by 10 times or more compared to the existing electrode life. Since it is manufactured by applying a rotational friction welding process, the cost may be low.

In addition, there is an advantage that it can be manufactured only with copper electrodes (CrCu) and general tungsten rods (W Rods), which are general-purpose electrodes.

1 is a schematic view showing a method of manufacturing an electrode tip for spot welding according to an embodiment of the present invention.

2 is a view showing a state in which a tungsten alloy material is inserted into a copper alloy material in the method of manufacturing an electrode tip for spot welding according to an embodiment of the present invention.

FIG. 3 is an enlarged photograph showing a bonding interface between a copper alloy material and a tungsten alloy material according to a method of manufacturing an electrode tip for spot welding according to an embodiment of the present invention.

4 is a view showing an electrode tip for spot welding, which is surface-treated by side dressing after cutting of a tungsten alloy material according to a method of manufacturing an electrode tip for spot welding according to an embodiment of the present invention.

5 is a graph showing a result of measuring an appropriate current range according to the Estimation of electrode life method.

6 is a graph showing the results of measuring the life of an electrode manufactured using an electrode tip for spot welding prepared according to an embodiment of the present invention according to ISO 18278-2 regulations.

Terms such as first, second and third are used to describe various parts, components, regions, layers and/or sections, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first portion, component, region, layer or section described below may be referred to as a second portion, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is only to refer to a specific embodiment and is not intended to limit the invention. The singular forms used herein also include plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of “comprising” embodies a particular property, region, integer, step, action, element, and/or component, and the presence or presence of other properties, regions, integers, steps, action, element, and/or component. It does not exclude addition.

When referring to a part being "on" or "on" another part, it may be directly on or on the other part, or another part may be involved therebetween. In contrast, if one part is referred to as being “just above” another part, no other part is interposed therebetween.

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains.

Commonly used dictionary-defined terms are further interpreted as having meanings consistent with related technical documents and currently disclosed contents, and are not interpreted as ideal or very formal meanings unless defined.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

Method for manufacturing electrode tips for spot welding

When described with reference to Figure 1, the electrode tip manufacturing method for spot welding according to an embodiment of the present invention is a placement step of placing the tip of the rod-shaped copper alloy material and the tip of the rod-shaped tungsten alloy material in contact with each other, copper A first inserting step of pressing the tungsten alloy material to the copper alloy material side while rotating the alloy material and a second inserting step of pressing the tungsten alloy material to the copper alloy material side while stopping the rotation of the copper alloy material.

After the second insertion step, a cutting step of cutting a portion of the tungsten alloy material that is not inserted into the copper alloy material and a processing step of surface-processing a portion where the copper alloy material and the tungsten alloy material are joined may be further included.

First, in the arrangement step, a rod-shaped copper alloy material tip and a rod-shaped tungsten alloy material tip are provided, and the copper alloy material tip and the tungsten alloy material tip are arranged to contact each other.

The rod-shaped copper alloy material may be made of a copper alloy material containing chromium (Cr). Specifically, the copper alloy material may contain 3% by weight or less of chromium (Cr), balance copper (Cu), and unavoidable impurities based on 100% by weight. The tensile strength of the copper alloy material may be 450 MPa or more, the yield strength may be 350 MPa or more, and the hardness may be 70 HRB or more. The conductivity may be 75%IACS or higher.

The rod-shaped tungsten alloy material may be formed of a material containing at least one of tungsten (W), tungsten carbide (WC), and cemented carbide (W-Co). The tungsten alloy material can be similar to the conductivity of the copper alloy material.

The cross-sectional area of the rod-shaped copper alloy material may be larger than that of the rod-shaped tungsten alloy material. The copper alloy material and the tungsten alloy material may be disposed in a form in which the copper alloy material tip is positioned at the center of the copper alloy material tip.

Next, in the first insertion step, the tungsten alloy material is pressed toward the copper alloy material in a state in which the copper alloy material is rotated. At this time, the speed of rotating the copper alloy material may be 1000 to 1500rpm.

When the rotational speed is less than 1000 rpm, the temperature of frictional heat due to friction between the tip of the copper alloy material and the tip of the tungsten alloy material is relatively low, so the tungsten alloy material may be broken or the tungsten alloy material may not be inserted smoothly.

On the other hand, when the rotational speed exceeds 1500 rpm, high-temperature frictional heat is generated, and thus the copper alloy material tip is crushed or the plastic flow is severe, so that deformation may occur.

The rotation of the copper alloy material may increase the temperature at the copper alloy material tip and the tungsten alloy material tip to 700 to 900°C by friction between the copper alloy material tip and the tungsten alloy material tip.

Meanwhile, the pressure when the tungsten alloy material is pressed toward the copper alloy material may be 0.4 to 0.8 PSI.

When the pressure is less than 0.4PSI, the insertion of the tungsten alloy material may not be sufficiently achieved, whereas when the pressure is greater than 0.8PSI, the tip of the copper alloy material may be crushed or the plastic flow may become severe, resulting in deformation. .

Next, in the second insertion step, the tungsten alloy material is pressed toward the copper alloy material while the rotation of the copper alloy material is stopped. After stopping the rotation of the copper alloy material, the tungsten alloy material is pressed to the copper alloy material side, but may be pressed with a force greater than the pressure in the first insertion step.

Specifically, the pressure when the tungsten alloy material is pressed toward the copper alloy material may be 1.0 to 1.4 PSI.

When the pressure is less than 1.0PSI, the insertion of the tungsten alloy material may not be sufficiently achieved, whereas when the pressure is greater than 1.4PSI, the tip of the copper alloy material may be crushed or the plastic flow may become severe, resulting in deformation. .

As in FIG. 2, through the first insertion step and the second insertion step, the length of the tungsten alloy material inserted into the copper alloy material may be 2 to 6 mm.

As shown in FIG. 3, when observing the cross section of the joint between the tungsten alloy material and the copper alloy material, no cracks or fractures were observed at the bonding interface where the tungsten alloy material and the copper alloy material contacted, and that the tungsten alloy material and the copper alloy material were well joined. Able to know.

Next, in the cutting step, a portion of the tungsten alloy material that is not inserted into the copper alloy material may be cut. The tungsten alloy material can be cut using a general wheel cutter.

Next, in the processing step, a portion where the copper alloy material and the tungsten alloy material are bonded may be surface-processed. At this time, a side dressing may be performed to perform a surface processing treatment according to the original electrode type (Dome Round electrode). The electrode tip for spot welding completed up to the processing is shown in FIG. 4.

Electrode tip for spot welding

An electrode tip for spot welding according to an embodiment of the present invention includes an electrode body portion of a copper alloy material and an electrode tip portion of a tungsten alloy material inserted at an end portion of the electrode body portion, and one surface of the outer surface of the electrode tip portion is a tip of the electrode body portion It forms a joint interface in contact with, and the other surface of the outer surface of the electrode tip portion is formed in a form exposed to the outside.

According to a method of manufacturing an electrode tip for spot welding according to an embodiment of the present invention, the copper alloy material tip and the tungsten alloy material tip are arranged to be in contact with each other, and the tungsten alloy material is a copper alloy material while rotating the copper alloy material. After pressurizing to the side, the tungsten alloy material is inserted into the copper alloy material by pressing the tungsten alloy material to the copper alloy material in a state where the rotation of the copper alloy material is stopped. have.

Thereafter, a part of the tungsten alloy material that is not inserted into the copper alloy material is cut and the joint is surface-processed, so that the copper alloy material part corresponds to the electrode body part in the electrode tip for spot welding, and the tungsten alloy material part is applied to the electrode tip part Can be countered.

Accordingly, the length of the electrode tip portion inserted into the electrode body portion may be 2 to 6 mm. Therefore, one surface and a side surface of the electrode tip portion are surrounded by the electrode body portion and are connected in contact with each other, and the other surface of the electrode tip portion is formed in a shape exposed to the outside, and when spot welding is performed on the steel plate, it may be a portion in contact with the steel plate.

A junction interface formed by one surface of the outer surface of the electrode tip portion in direct contact with the tip of the electrode body portion may be formed in a form deformed by frictional heat. This is a method of pressing the electrode tip into a hole drilled in the electrode body, a method of inserting the electrode tip into the electrode body through a brazing material, a method of heating expansion to embed the electrode tip in the surrounding material, and casting the electrode tip to cold the electrode body. Unlike when connected by a forging method or the like, as shown in FIG. 3, a junction interface may be formed, and cracks and fractures may not be formed at the junction interface.

Hereinafter, preferred examples and test examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited to the following examples.

Example

Using the electrode tip for spot welding prepared according to an embodiment of the present invention, electric resistance spot welding was performed under the welding conditions of Table 1 below. For steel, PosMAC 1.5, a highly corrosion-resistant galvanized steel sheet commercially available as an automotive steel sheet, was applied. The thickness of the steel sheet was 1.0 mmt, the plating amount was 120 g/m ² on both sides, and the plating thickness was about 10 μm or less.

The welding machine is an AC welding machine (60Hz) that is commonly used by automobile manufacturers, and the welding conditions are based on the thickness and plating amount of the steel sheet.

Steel	Thickness(mm)	Electrode type	Electrode (mm)	Pressing force (kN)	Pulse count	Welding time (Cy)	Cooling time (Cy)	Holding time (Cy)	Standard button diameter(mm)
CoatedDDQ	1.0	DR	6	2.7	One	14	0	14	4

The battering experiment was conducted according to the ISO 18278-2 Estimation of electrode life method. First, an appropriate current range was measured according to regulations, and the results are shown in FIG. 5.

The plug diameter of the spot weld becomes the reference diameter in proportion to the thickness of the steel sheet, which is usually 4√t. Since the thickness of the steel sheet is 1 mm, the reference diameter is 4 mm. As shown in FIG. 5, the welding expulsion occurred at a current of 11 kA or more.

Therefore, the appropriate current range was 9.2 kA to 11 kA, and the current value in the continuous run experiment was 10.5 kA.

6 is an electrode manufactured by using an electrode tip for spot welding prepared according to an embodiment of the present invention, and shows the result of measuring the lifespan according to ISO 18278-2. At about 2,900 RBI, the plug diameter reached the reference diameter of 4 mm.

Therefore, when applied as a high corrosion-resistant plated steel sheet PosMAC 1.5 steel sheet, the life of the electrode produced by using the electrode tip for spot welding prepared by an embodiment of the present invention is about 2900 strokes.

The electrode photograph in the graph in FIG. 6 shows the upper/lower electrode surface after 2900 strokes. It can be seen that the result is about 10 times as compared with 200 to 300 strokes, which are the lifespan of the conventional general electrode.

The present invention is not limited to the above embodiments and/or embodiments, but may be manufactured in various different forms, and those skilled in the art to which the present invention pertains may change the technical spirit or essential features of the present invention. It will be understood that it may be practiced in other specific forms without. Therefore, it should be understood that the above-described embodiments and/or embodiments are illustrative in all respects and not restrictive.

Claims (12)

1. A disposing step of disposing the tip of the rod-shaped copper alloy material and the tip of the rod-shaped tungsten alloy material in contact with each other;

   A first insertion step of pressing the tungsten alloy material toward the copper alloy material while rotating the copper alloy material; And

   And a second inserting step of pressing the tungsten alloy material toward the copper alloy material while the rotation of the copper alloy material is stopped.
2. According to claim 1,

   In the above arrangement step,

   The cross-sectional area of the copper alloy material is larger than the cross-sectional area of the tungsten alloy material, a method of manufacturing an electrode tip for spot welding in which the tip of the copper alloy material is positioned at the center of the tip of the copper alloy material.
3. According to claim 1,

   In the first insertion step,

   The copper alloy material is rotated at a speed of 1000 to 1500 rpm.
4. According to claim 1,

   In the first insertion step,

   A method of manufacturing an electrode tip for spot welding that increases the temperature at the tip of the copper alloy material and the tip of the tungsten alloy material by rotating the copper alloy material to 700 to 900°C.
5. According to claim 1,

   In the first insertion step,

   A method of manufacturing an electrode tip for spot welding, wherein the pressure when the tungsten alloy material is pressed toward the copper alloy material is 0.4 to 0.8 PSI.
6. According to claim 1,

   In the second insertion step,

   The pressure when the tungsten alloy material is pressed toward the copper alloy material is 1.0 to 1.4 PSI.
7. According to claim 1,

   In the first insertion step and the second insertion step,

   The tungsten alloy material is inserted into the copper alloy material length is 2 to 6mm electrode welding method for spot welding.
8. According to claim 1,

   After the second insertion step,

   A cutting step of cutting a portion of the tungsten alloy material that is not inserted into the copper alloy material; And

   A method of manufacturing an electrode tip for spot welding further comprising; a processing step of surface-processing a portion in which the copper alloy material and the tungsten alloy material are joined.
9. An electrode body part made of a copper alloy material; And

   Includes; the electrode tip portion of a tungsten alloy material inserted into the end of the electrode body portion,

   One side of the outer surface of the electrode tip portion is in contact with the tip of the electrode body portion to form a bonding interface, the other side of the outer surface of the electrode tip portion is an electrode tip for spot welding exposed to the outside.
10. The method of claim 9,

    The electrode tip portion is inserted into the electrode body portion length is 2 to 6mm electrode tip for welding.
11. The method of claim 9,

    The electrode body portion,

    An electrode tip for spot welding containing 3% by weight or less of chromium (Cr), residual copper (Cu), and unavoidable impurities, based on 100% by weight.
12. The method of claim 9,

    The electrode tip portion,

    An electrode tip for spot welding comprising at least one of tungsten (W), tungsten carbide (WC) and cemented carbide (W-Co).

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