KR20180090620A - Method of eliminating pin pinhole generated during friction stir welding - Google Patents

Abstract

The present invention relates to a method and system for pinhole removal by friction stir welding that enables pinholes generated in friction stir welding to be removed using resistance welding. The method includes the steps of: The first electrode of the resistance welding device is disposed on one surface of the first member corresponding to the pinhole generated in the first member due to the performed friction stir welding and the first electrode of the resistance welding device is disposed on one surface of the second member corresponding to the first electrode An electrode disposing step of disposing a second electrode of the resistance welding apparatus; And a resistance welding step of performing resistance welding by applying electric power between the first electrode and the second electrode, wherein the material of the first electrode and the second electrode is a material of the first member and the first electrode And the contact resistance of the electrode is larger than the contact resistance between the second member and the second electrode.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and a system for removing pinholes by friction stir welding,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of removing pinholes by friction stir welding, and more particularly, to a method of removing pinholes generated by friction stir welding using resistance welding.

Friction stir welding tool is used to generate frictional heat between the material and the friction stir welding tool, and the material softened by the frictional heat is agitated by rotation of the welding tool to cause friction stir welding Welding is a welding method widely used in railway vehicles, ships, aircraft, automobiles, etc. due to the advantage that the blowholes and cracks do not occur and the deformation due to welding is less than the melting welding such as arc welding, laser welding and electron beam welding.

Korean Prior Art No. 0481784 (registered on March 30, 2005, entitled "Friction stir welding method") is a related prior art.

However, in the conventional friction stir welding, pinholes are inevitably generated in the space where the friction stir welding tool exits at the end of the welding, that is, the welding end point. Such a pinhole structurally acts as a critical weak point to the welding object, Not only cause cracking but also the surface is not smooth and not good in appearance. When the first member and the second member made of different materials are laminated vertically and joined together by friction stir welding, a problem of thermal balance occurs from the viewpoint of the contact resistance and the thermal conductivity, so that the interface between the first member and the second member There is a problem that an intermetallic compound grows at the joint portion to lower the joint strength.

It is an object of the present invention to solve such a conventional problem, and it is an object of the present invention to provide a method and apparatus for welding a pinhole, The defect rate can be greatly reduced and the shape of the electrode end of the resistance welding device can be formed into a spherical shape so that it can be applied to pinholes of various sizes and finally the shape of the resistance welding portion remaining in the product can be made smooth, And a method of removing pinholes by friction stir welding. It is another object of the present invention to provide a pinhole removing method capable of solving the problem of thermal balance inevitably caused by overlapping friction stir welding of dissimilar materials. However, these problems are exemplary and do not limit the scope of the present invention.

A method for removing pinholes by friction stir welding according to one aspect of the present invention for solving the above problems is provided. The method of removing pinholes by friction stir welding according to the present invention is characterized in that a first member and a second member having different materials are vertically stacked and friction stir welding is performed on one surface of the first member corresponding to a pinhole generated in the first member Disposing a first electrode of a resistance welding apparatus and disposing a second electrode of the resistance welding apparatus on one surface of the second member so as to correspond to the first electrode; And a resistance welding step of performing resistance welding by applying electric power between the first electrode and the second electrode, wherein the material of the first electrode and the second electrode is a material of the first member and the first electrode And the contact resistance of the electrode is larger than the contact resistance between the second member and the second electrode.

Wherein the first member comprises aluminum (Al), the second member comprises iron (Fe), and the first electrode is made of stainless steel (STS), and the material of the second electrode may include copper (Cu).

In the resistance welding of the pinhole removing method according to the friction stir welding, the first electrode and the second electrode may be made of a material such that the material around the pinhole is partially deformed during resistance welding, The pressing force of the first electrode and the second electrode can be pressed to a pressure equal to or higher than the minimum deformation pressure.

In the resistance welding step of the pinhole removing method by the friction stir welding, the electric power applied between the first electrode and the second electrode is controlled so that the heat generated during the resistance welding may be a temperature lower than the melting point of the material .

Wherein the diameter of the first electrode is larger than at least the diameter of the pinhole and the contact area with the pinhole is larger than the diameter of the pinhole of the pinhole regardless of the size of the pinhole, And may have a spherical surface having a radius of curvature that is at least partially larger than the radius of the pin hole.

The method of removing pinholes by friction stir welding is characterized in that before the electrode placement step, the first and second members having different materials are vertically stacked, and then the rotating friction stir welding tool is contacted with the first member And performing friction stir welding by performing friction stir welding.

A method of removing pinholes by friction stir welding according to another aspect of the present invention for solving the above problems is provided. The method for removing pinholes by friction stir welding is a friction stir welding method in which friction stir welding is performed from a starting point to an end point by contacting a rotating friction stir welding tool with the first member after the first member and the second member are vertically stacked Performing stirring welding; The first electrode of the resistance welding device is disposed on one surface of the first member corresponding to the pinhole generated at the end point of the first member due to the friction stir welding, An electrode disposing step of disposing a second electrode of the resistance welding apparatus on one surface; And a resistance welding step of performing resistance welding by applying electric power between the first electrode and the second electrode, wherein the material of the first electrode and the second electrode is a material of the first member and the first electrode And the contact resistance of the electrode is larger than the contact resistance between the second member and the second electrode.

According to another aspect of the present invention, there is provided a welding object for solving the above problems. The object to be welded includes an object to be welded, which is manufactured using the above-described pinhole removing method by friction stir welding.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart illustrating a method of pinhole removal by friction stir welding according to some embodiments of the present invention.
FIG. 2A is a cross-sectional view conceptually showing the step of performing friction stir welding of FIG. 1. FIG.
FIG. 2B is a perspective view conceptually showing the step of performing friction stir welding in FIG. 1. FIG.
3 is a cross-sectional view conceptually showing the electrode placement step of FIG.
4 is a cross-sectional view conceptually showing the step of performing the resistance welding of FIG.
Fig. 5 is a cross-sectional view showing a welding object after the resistance welding step of Fig. 1 is completed.

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

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the invention to those skilled in the art. In the drawings, the thickness and size of each layer are exaggerated for convenience and clarity of explanation.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include singular forms unless the context clearly dictates otherwise. Also, " comprise "and / or" comprising "when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

Hereinafter, embodiments of the present invention will be described with reference to the drawings schematically showing ideal embodiments of the present invention. In the figures, for example, variations in the shape shown may be expected, depending on manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present invention should not be construed as limited to the particular shapes of the regions shown herein, but should include, for example, changes in shape resulting from manufacturing.

In the method of removing pinholes by friction stir welding according to the technical idea of the present invention, removing the pinhole may mean not only completely removing the pinhole completely but also removing at least a part of the pinhole, It can be understood as a repair method of pin holes.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart illustrating a method of pinhole removal by friction stir welding according to some embodiments of the present invention.

As shown in FIG. 1, a method for removing pinholes by friction stir welding according to some embodiments of the present invention includes a friction stir welding performing step S1, an electrode placing step S2, Step S3 may be included. In this embodiment, the step of performing the friction stir welding (S1) may include the friction stir welding as well as the friction stir welding.

Hereinafter, the above-described steps S1, S2, and S3 will be described in more detail.

FIG. 2A is a cross-sectional view conceptually showing the step of performing friction stir welding in FIG. 1, and FIG. 2B is a perspective view conceptually showing a step of performing friction stir welding in FIG.

For example, as shown in Figs. 1, 2A, and 2B, the friction stir welding performing step S1 is performed by using the rotating friction stir welding tool 11 to rotate the first member 1 and the second member 3 may be performed by performing friction stir welding from the starting point P1 to the end point P2 of the object to be welded, which are stacked one over the other.

More specifically, for example, such a friction stir welding tool 11 can be used as the friction stir welding tool 11, in which the first member 1 and the second member 3 are stacked one on top of the other, P1 and the end point P2, and the material softened by the frictional heat is agitated by the rotation of the friction stir welding tool 11, 1) and the second member 3 can be performed.

The friction stir welding tool 11 including the starting point P1 and the end point P2 is in a straight line in FIGS. 1, 2A and 2B. However, the friction stir welding tool 11 ) May be formed in a wide variety of shapes such as circular, circular, zigzag, serpentine, and various other geometric shapes.

When the friction stir welding tool 11 exits from the welding object at the end point P2, the pinhole H necessarily occurs in the welding object in which the first member 1 and the second member 3 are stacked one above the other. For example, a pinhole H may be generated in the first member 1 of the object to be welded, and an opening of the pinhole H may be exposed on the surface of the first member 1.

The shape of the pinhole H and the friction stir welding tool 11 forming the pinhole H may be variously varied, and may be various, such as a cylindrical shape, a partial cone shape, and the like.

3 is a cross-sectional view conceptually showing an electrode arrangement step S2 of FIG.

1 and 3, the electrode disposing step S2 is performed in a first direction of the pinhole H formed at the end point P2, as shown in FIGS. 1 and 3, And placing the second electrode 22 of the resistance welding apparatus 20 in a second direction opposite to the first direction. In the cross-sectional view, the first direction includes a direction extending upward from the surface of the first member 1, and the second direction includes a direction extending from the surface of the second member 3 downward.

More specifically, for example, the resistance welding apparatus 20 may be a spot welding apparatus. However, the resistance welding apparatus 20 is not necessarily limited to the spot welding apparatuses, but may be provided with a resistance heat of current such as seam welding, projection welding, flash tasteless welding, upset butt welding, discharge shock welding, etc. capable of other lapping and butt welding All resistance welding apparatus of a wide variety of types can be applied. In this resistance welding apparatus 20, the most basic condition may be the magnitude of the current, the pressing force, and the energization time. It goes without saying that these welding conditions may be optimized depending on the required specification, the welding environment, or the type and shape of the welding object in which the first member 1 and the second member 3 are stacked one above the other .

The diameter D2 of the first electrode 21 is greater than the diameter D1 of the pinhole H in the electrode arrangement step S2, Has a spherical surface 21a having a radius of curvature R2 larger than the radius R1 of the pinhole H so as to be in contact with the entrance of the pinhole H irrespective of the size of the pinhole H Lt; / RTI >

That is, when the diameter D2 of the first electrode 21 is smaller than the diameter D1 of the pinhole H, the first electrode 21 is inserted into the pinhole H, If the curvature radius R2 of the spherical surface 21a is smaller than the radius R1 of the pinhole H, the spherical surface 21a is hard to be brought into contact with the entrance of the pinhole H evenly Because.

Therefore, the diameters of the first electrode 21 or the second electrode 22 and the radius of curvature of the spherical surface can be made sufficiently large as described above, whereby the pinholes H of various shapes and sizes can be formed. . ≪ / RTI >

However, if the diameter of the first electrode 21 or the second electrode 22 or the radius of curvature of the spherical surface is infinitely large, this is not economical. As a result of repeated experiments, Wherein the diameter D2 of the pinhole H is at least 1.5 times to 5 times the diameter D1 of the pinhole H and the contact area with the pinhole H is the diameter of the pinhole H, It may be desirable to have a spherical surface 21a with a radius of curvature R2 that is at least 2 times to 10 times the radius R1 of the pinhole H so as to be in contact with the inlet portion.

4 is a cross-sectional view conceptually showing a resistance welding performing step S3 of FIG.

Next, as shown in FIGS. 1 and 4, the resistance welding step S3 includes performing resistance welding by applying electric power between the first electrode 21 and the second electrode 22 Lt; / RTI >

More specifically, for example, in the resistance welding step S3, the first electrode 21 and the second electrode 22 are partially deformed in the vicinity of the pinhole H during resistance welding, The pressing force of the first electrode 21 and the second electrode 22 may be pressurized to a pressure of a minimum deformation pressure so as to be introduced into the pinhole H. [

Also, for example, the electric power applied between the first electrode 21 and the second electrode 22 can be controlled so that the heat generated during the resistance welding may be a temperature below the melting point of the work.

Therefore, the material around the pinhole H is pressurized to a pressure equal to or higher than the minimum deformation pressure, is sufficiently softened at a temperature not higher than the melting point so as to be melted and moved into the pinhole H by pressure, The pinhole H can be removed.

4, it is also possible that the nugget 4 is included in the internal structure of the object to be welded in which the first member 1 and the second member 3 are vertically stacked.

FIG. 5 is a cross-sectional view showing a welding object in which the first member 1 and the second member 3, which have been welded after the resistance welding step S3 of FIG. 1, are stacked one over the other.

A welding object in which the first member 1 and the second member 3 are stacked one over the other is stacked to form a friction welding portion 1a by friction welding and the end point P2 of the friction welding portion 1a is replaced with a pin hole A resistance welding portion 1b may be formed.

Therefore, as shown in FIG. 5, the material around the pinhole H can be filled with the pinhole H using resistance welding, so that the structure of the product can be structurally very robust, It is possible to greatly reduce the vulnerability incidence rate and the defective product rate and to form the shape of the ends of the first electrode 21 and the second electrode 22 of the resistance welding apparatus 20 in a spherical shape, And the shape of the resistance welding portion 1b remaining in the product finally becomes gentle, so that it can be aesthetically excellent.

In the above-described method, the friction stir welding is performed by contacting the rotating friction stir welding tool 11 with the first member 1 after the first member 1 and the second member 3 are stacked one over the other, Lt; / RTI > to an end point. The lap welding is distinguished from the butt welding in which the side surfaces of the first member and the side surfaces of the second member are arranged side by side without welding the first member and the second member.

In this lap welding, when the materials of the first member 1 and the second member 3 are different from each other, a problem of thermal balance caused by a difference in contact resistance and / or thermal conductivity must be solved. Further, the problem that the intermetallic compound is excessively grown at the joint portion 2 between the first member 1 and the second member 3, which are different from each other, and the bonding strength is lowered, must be solved.

The contact resistance between the first member 1 and the first electrode 21 is greater than the contact resistance between the second member 3 and the second electrode 22, High resistance heat is generated in the vicinity of the pinhole H to remove the pinhole H and suppress excessive growth of the intermetallic compound in the bonding portion 2 between the first member 1 and the second member 3. [

For example, when the material of the first member 1 includes aluminum (Al) and the material of the second member 3 includes iron (Fe), the material of the first electrode 21 is stainless steel (H) around the pinhole (H) by using a stainless steel electrode having a high contact resistance for the aluminum member on which the pinhole (H) is formed, by configuring the second electrode (22) The pinhole H can be removed by generating a high resistance heat in the aluminum member. Furthermore, by using the copper electrode for the iron member contacting the aluminum member, the problem of thermal balance of contact resistance and / or thermal conductivity is solved It is possible to suppress excessive growth of the intermetallic compound at the bonding portion 2 between the first member 1 and the second member 3. [

The configuration is such that the contact resistance between the first member 1 and the first electrode 21 is greater than the contact resistance between the second member 3 and the second electrode 22, It is assumed that the materials of the first member 1 and the second member 3 are different from each other. The contact resistance between the first member 1 and the first electrode 21 is greater than the contact resistance between the second member 3 and the second electrode 22, The configuration can be applied even when the materials of the first member 1 and the second member 3 are not different from each other.

1 to 5, a pinhole repair system by friction stir welding according to some embodiments of the present invention includes a first member 1 using a rotating friction stir welding tool 11, A friction stir welding apparatus 10 for performing friction stir welding from a starting point P1 to an end point P2 of the welding object in which the first member 3 and the second member 3 are stacked one on the other and the pinhole H A second electrode 22 disposed in a second direction opposite to the first direction and a second electrode 22 disposed between the first electrode 21 and the second electrode 22, And a power application device 23 for performing resistance welding by applying electric power between the resistance welding device 20 and the resistance welding device 20.

The diameter D2 of the first electrode 21 of the resistance welding apparatus 20 is larger than the diameter D1 of the pinhole H and the contact area with the pinhole H is larger than the diameter D1 of the pinhole H. [ H having a radius of curvature R2 larger than the radius R1 of the pinhole H so as to be in contact with the entrance of the pinhole H irrespective of the size of the pinhole H.

Therefore, the pin hole can be removed by resistance welding, the product can be structurally very rigid, the vulnerability rate and the defect rate of the product can be greatly reduced, and the electrode end portion of the resistance welding apparatus can be formed into a spherical shape, And the shape of the resistance welding portion remaining in the product finally becomes gentle, so that it can be aesthetically excellent.

On the other hand, in the pinhole repair system by the above-described friction stir welding, the friction stir welding performed when the welding object in which the first member 1 and the second member 3 are stacked one on top of the other is stacked and welded, 21 and the second electrode 22 are configured such that the contact resistance between the first member 1 and the first electrode 21 is greater than the contact resistance between the second member 3 and the second electrode 22 High resistance heat is generated around the pinhole H to remove the pinhole H and suppress excessive growth of the intermetallic compound in the bonding portion 2 between the first member 1 and the second member 3. [

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

1: first member
3: second member
P1: Starting point
P2: end point
10: Friction stir welding device
11: Friction stir welding tool
H: Pinhole
20: Resistance welding device
21: first electrode
22: second electrode
23: Power application device
S1: Performing friction stir welding step
S2: Electrode placement step
S3: Resistance welding step

Claims (8)

The first electrode of the resistance welding device is disposed on one surface of the first member corresponding to the pinhole generated in the first member due to friction stir welding performed by vertically overlapping the first member and the second member having different materials from each other And disposing a second electrode of the resistance welding device on one surface of the second member so as to correspond to the first electrode; And
And performing resistance welding by applying electric power between the first electrode and the second electrode,
Wherein the material of the first electrode and the second electrode is such that the contact resistance between the first member and the first electrode is larger than the contact resistance between the second member and the second electrode, Removal method. The method according to claim 1,
Wherein the material of the first member includes aluminum (Al), the material of the first electrode includes stainless steel (STS), the material of the second member includes iron (Fe) Wherein the material of the pinhole is copper (Cu). The method according to claim 1,
In the resistance welding step,
The pressing force of the first electrode and the second electrode is pressurized to a pressure equal to or higher than the minimum deformation pressure so that the material around the pinhole can be partially deformed and introduced into the pinhole when resistance welding is performed between the first electrode and the second electrode. Wherein the pinhole is removed by friction stir welding. The method according to claim 1,
In the resistance welding step,
Wherein the power applied between the first electrode and the second electrode is controlled so that heat generated during resistance welding may be at a temperature equal to or lower than a melting point of the material. The method according to claim 1,
In the electrode placement step,
Wherein a diameter of the first electrode is at least larger than a diameter of the pinhole and a contact portion with the pinhole is formed to have a radius of curvature larger than a radius of the pinhole partially so as to be in contact with an inlet portion of the pinhole, A method for removing pinholes by friction stir welding having spherical surfaces. The method according to claim 1,
Before the electrode placement step,
A friction stir welding step of performing friction stir welding by contacting the first friction stir welding tool with the first member after vertically overlapping the first member and the second member having different materials from each other;
Wherein the pinhole is formed by friction stir welding. Performing a friction stir welding operation in which friction stir welding is performed from a start point to an end point by contacting a rotating friction stir welding tool with the first member after vertically overlapping the first member and the second member;
The first electrode of the resistance welding device is disposed on one surface of the first member corresponding to the pinhole generated at the end point of the first member due to the friction stir welding, An electrode disposing step of disposing a second electrode of the resistance welding apparatus on one surface; And
And performing resistance welding by applying electric power between the first electrode and the second electrode,
Wherein the material of the first electrode and the second electrode is such that the contact resistance between the first member and the first electrode is larger than the contact resistance between the second member and the second electrode, Removal method. A welding object manufactured by the method of any one of claims 1 to 7 by using the pinhole removing method by the friction stir welding.

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