JPH09234573A - Production device of resistance welded tube and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce defective difference in level by making a flow pattern of induction current flowing in a metal strip. SOLUTION: A bent part 34 is formed to the part at the side of both butt faces 111, 112 of a coil wire 31 o a high frequency heating coil 3. By viewing the side of both butt face 111, 112, the bent part 34 is made projecting in the forwarding side of a metal strip 1 and is bent roughly symmetrical to the axial line of the metal strip bent cylindrical shape. This method prevents the induction current from concentrating to both butt faces 111, 112 so as to suppress softening of both butt faces. Accordingly, deformation of both butt faces is suppressed, defective difference in level is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing apparatus and a manufacturing method of an electric resistance welded tube manufactured by bending a flat metal strip into a cylindrical shape and welding its abutting surface.

[0002]

2. Description of the Related Art In an electric resistance welded tube, flat metal strips are sequentially curved and formed into a cylindrical shape by a group of forming rolls, and both ends of the curved metal strips are locally heated by a high frequency heating coil. It is a tube that is formed by melting and melting it, and then pressing it with a squeeze roll to join it.

By the way, in the electric resistance welded pipe, as described above, since both ends of the metal strip are heated and melted and pressure-bonded by squeeze rolls, there is a difference in a softened state between the abutting surfaces of both ends. Then, a step defect occurs in which a step is generated on the abutting surface due to the pressing force of the squeeze roll. As means for solving this step defect, there is one described in Japanese Patent Laid-Open No. 182076/1992 (see FIG. 5). Specifically, in the two-winding high-frequency heating coil 13, the abutting surface 111,
By crossing the winding 131 of the high-frequency heating coil 13 on the opposite side to 112, the flow direction of the current flowing through the windings on both the abutting surfaces 111, 112 is made symmetrical with respect to the abutting surfaces 111, 112. As a result, both abutting surfaces 11 of the metal strip are
The difference in the softened state between Nos. 1 and 112 is alleviated, and the occurrence of step defects is suppressed.

[0004]

Therefore, the inventors have
When an electric resistance welded pipe manufacturing apparatus as described in the above publication as shown in FIG. 5 was prototyped and tested, it was not possible to sufficiently suppress the occurrence of step defects. Then, as a result of further examination and examination, it became clear that the cause described below as the cause of the step defect is largely due to the above-mentioned cause (the difference in the softened state between the two abutting surfaces 111 and 112).

That is, the welding of the electric resistance welded pipe utilizes the heat generation (Joule heat) due to the induction current induced in the skin of the metal strip 11 by the high frequency heating coil 13.
Is softened, the part to be softened greatly depends on the flow of the induced current. The winding 131 of the high-frequency heating coil 13 has a cylindrical metal strip 11 as shown in FIG.
Since they are arranged at right angles to the axial direction of, the induced current is also induced in the skin of the metal strip 11 so as to be perpendicular to the axial direction of the metal strip 11 (parallel to the winding 131).

However, the abutting surfaces 111, 1 of the metal strip 11 corresponding to the portion where the high frequency heating coil 13 is arranged.
As shown in FIG. 5, a void is formed in 12, so that the induced current cannot flow in a circular shape around the axis of the cylindrical metal strip 11. Therefore, when a current flows in the high-frequency heating coil 13 as shown by the arrow in FIG. 5, for example, the induced current 18 is generated by the abutting surface 11 as shown in FIG.
In regions other than the vicinity of 1 and 112, it flows in an arc shape around the axis of the cylindrical metal strip 11, flows along the vicinity of the abutting surface 112, and joins the abutting surfaces 111 and 112 (hereinafter,
Call it a welding point. ) 17 and flows along the vicinity of the abutting surface 111, and again flows in an arc shape around the axis of the cylindrical metal strip 11. As a result, the vicinity of the welding point 17 and the abutting surfaces 111, 112 where the induced current 18 tends to concentrate (hatched portion in FIG. 6) heats and softens.

Of the portion where the induced current 18 concentrates and softens, the portion of the abutting surfaces 111 and 112 which is not supported by the supporting means such as the guide shoe 12 (the portion between the guide shoe 12 and the welding point 17). Squeeze roll 1
It is deformed by the pressing force of 4 and 15. Then, since both the abutting surfaces 111 and 112 are welded while being deformed,
It became clear that a step defect would occur.

By the way, as is clear from the above description, the occurrence of a step difference can be reduced by bringing the supporting portion of the metal strip 11 by the guide shoe 12 close to the welding point 17. However, when the supporting portion of the guide shoe 12 is brought close to the welding point 17, the guide shoe 12 interferes with the high-frequency heating coil 13, so that there is a limit in reducing the step defect.

Therefore, in order to sufficiently reduce the step defect, it is ideally desirable to concentrate the induced current only in the vicinity of the welding point 17. The present invention has been made in view of the above consideration by the inventors, and an object of the present invention is to reduce step defects by optimizing the flow of the induced current flowing in the metal strip.

[0010]

The present invention uses the following technical means in order to achieve the above object. Claim 1
In the invention described in 5, the power feeding portions (32, 33) are provided on both abutting surfaces (111, 112), and the high frequency heating coil (3) is provided.
A bent portion (34) is formed in a portion of the winding (31) on both sides of the abutting surfaces (111, 112). And
When viewed from both abutting surfaces (111, 112), the bent portion (3
4) is characterized in that the traveling direction side of the metal strip (1) is convex and is bent so as to be substantially symmetrical with respect to the axis of the cylindrical metal strip (1).

Since the bent portion (34) is formed, both abutting surfaces (111, 112) are formed, as will be described later.
Concentration of induced current in the vicinity is suppressed. Therefore, since the deformation of both abutting surfaces (111, 112) is suppressed, it is possible to reduce the occurrence of step defects. Also,
By providing the power feeding parts (32, 33) on both abutting surfaces (111, 112) side, the power feeding parts (32, 3) will be described later.
Compared to the case where 3) is not provided on both abutting surfaces (111, 112), the flow of the induced current in the vicinity of both abutting surfaces (111, 112) is substantially equal. Therefore, since the difference in the softened state between the two abutting surfaces (111, 112) is alleviated, the occurrence of step defects can be suppressed.

According to a second aspect of the present invention, in the electric resistance welded pipe manufacturing apparatus according to the first aspect, both abutting surfaces (111, 11).
When viewed from the 2) side, the apex (34a) of the bent portion (34) is
It is characterized in that the abutting surfaces (111, 112) are displaced on the supply side of the metal strip (1) with respect to the welding point (7) at which they join. Thereby, as will be described later, it is possible to effectively concentrate the induced current at the welding point (7).

According to a third aspect of the present invention, in the electric resistance welded pipe manufacturing apparatus according to the first or second aspect, the bent portion (34) is provided.
Is widened toward the supply side of the metal strip (1) so as to be wider than the angle (θ) formed by both abutting surfaces (111, 112). Thereby, as will be described later, it is possible to effectively concentrate the induced current at the welding point (7).

According to a fourth aspect of the present invention, in the electric resistance welded pipe manufacturing apparatus according to any one of the first to third aspects,
The high frequency heating coil (3) is wound twice, and the abutting surface (1
It is characterized in that the windings (31) intersect on the opposite side of (11, 112). As a result, both abutting surfaces (111, 1)
The flow of the current flowing through the winding (31) on the 12) side is symmetrical with respect to both abutting surfaces. Therefore, the difference in the softened state between the abutting surfaces (111, 112) of the metal strip (1) is alleviated, so that the occurrence of a step difference can be suppressed.

According to a fifth aspect of the invention, there is provided a method of manufacturing an electric resistance welded pipe using the electric resistance welded pipe manufacturing apparatus according to any one of the first to fourth aspects. In addition, the code | symbol in the parenthesis of each said means shows the correspondence with the concrete means of embodiment mentioned later.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; (First Embodiment) In the present invention, a flat metal strip is sequentially curved and formed into a cylindrical shape by a forming roll group, and the abutting surfaces of the metal strips that are abutted at the time of the bending are locally formed by a high frequency heating coil. The present invention relates to an electric resistance welded pipe (hereinafter, simply referred to as a tube) that is heated and softened to be welded and formed, and the present embodiment relates to an aluminum heat exchanger (for example, a condenser or an evaporator of an air conditioner). , Radiators for vehicles) are applied to the manufacture of tubes.

FIG. 1 is a schematic view showing the entire manufacturing process in the electric resistance welded pipe manufacturing apparatus according to this embodiment. A flat metal strip 1 which is a material of a tube is wound in a coil shape and stored. Has been done. Then, this coiled metal strip 1
Is gradually formed into a cylindrical shape while being guided by the first forming roll group 20. The metal strip 1 formed into a substantially cylindrical shape is heated by the high-frequency heating coil 3 arranged in the welded portion (the portion surrounded by the two-dot chain line in FIG. 1) 21, and is heated and softened. The end of strip 1
The squeeze rolls 4 and 5 are pressed against each other in a butt-contact state and welded. Next, after the beat of the butt-welded portion is cut and smoothed by the cutting tool 22, it is formed into a predetermined shape such as a flat shape by the second forming roller group 23.

Next, the welded portion 21 will be described with reference to FIG. FIG. 2 (A) shows an upper view of the welded portion 21, and 2 shows the metal strip 1 in contact with the abutting surfaces 111, 112 to which both ends of the metal strip 1 formed in a substantially cylindrical shape abut. Is a guide shoe that suppresses the positional deviation of the abutting surfaces 111 and 112. Numerals 4 and 5 further pressurize the metal strip 1 formed into a substantially cylindrical shape by the first forming roller group 20 to bend the metal strip 1 into a cylindrical shape having an axis parallel to the traveling direction of the metal strip 1. A squeeze roll that joins the abutting surfaces 111 and 112. The squeeze rolls 4 and 5 and the guide shoe 2 are made of non-metal such as ceramics that has excellent wear resistance and does not generate an induced current.

Then, close to the squeeze rolls 4 and 5,
Further, a high-frequency heating coil 3 is arranged on the supply side of the metal strip 1 with respect to the squeeze rolls 4 and 5, and the high-frequency heating coil 3 surrounds the outer peripheral portion of the metal strip 1 curved in a substantially cylindrical shape. Thus, the winding 31 is wound twice. A bent portion 34 that is bent in a V shape so that the traveling direction side of the metal strip 1 is convex is formed at a portion of the winding 31 on the abutting surfaces 111 and 112 side.
Is substantially symmetric with respect to the axis of the metal strip 1 curved in a cylindrical shape when viewed from both the abutting surfaces 111 and 112.

Further, the apex 34a of the bent portion 34 is displaced to the supply side of the metal strip 1 with respect to the welding point 7 where the two abutting surfaces 111 and 112 are joined, and the bending angle Θ of the bent portion 34
Is larger than the angle θ formed by the abutting surfaces 111 and 112 at the welding point 7. That is, the bent portion 34 is expanded so as to be wider than the angle θ formed by the abutting surfaces 111 and 112.
It extends toward the supply side of the metal strip 1.

On the other side of the abutting surfaces 111 and 112, the winding 31 intersects as shown in FIG. 2B, whereby the high frequency heating coil 3 on the abutting surfaces 111 and 112 side. The current flow inside is substantially symmetrical with respect to the axis of the metal strip 1 curved in a cylindrical shape. Incidentally, the winding 31 is a copper pipe, and cooling water circulates inside the winding 31.

Further, the bent portion 34 is the bent portion (3
4) vertex (34a) Further, the high frequency heating coil 3 is
A high-frequency current (frequency is about 200 kHz, voltage is about 200 to 300) from the external power source 6 via the power feeding units 32 and 33.
v), the power feeding portions 32 and 33 are provided on the abutting surfaces 111 and 112 sides. Next, the features of the welded portion 21 according to the present embodiment will be described.

When viewed from the two abutting surfaces 111 and 112, the bent portion 34 is substantially symmetrical with respect to the axis of the metal strip 1 curved in a cylindrical shape (hereinafter, simply referred to as the axis), and
Since the metal strip 1 is bent in a V shape so as to be convex on the traveling direction side, the induction current induced in the metal strip 1 curved in a cylindrical shape by the high-frequency heating coil 3 is shown in FIG. Like That is, the induced current 8 is applied to the abutting surface 11
In regions other than the vicinity of 1, 112, the flow flows in a substantially elliptical shape around the axis so as to incline with respect to the axis of the bent portion 34 of the high-frequency heating coil 3, and then passes through the welding point 7 and again. It flows in a substantially elliptical shape. Therefore, the induced current 8 is suppressed from concentrating in the vicinity of the abutting surfaces 111 and 112, and thus the softening of the vicinity of the abutting surfaces 111 and 112 by the induced current 8 is suppressed. Further, since the deformation of the abutting surfaces 111 and 112 is suppressed, it is possible to reduce the step defect.

The induced current 8 is applied to the abutting surfaces 111 and 112.
Concentration in the vicinity is suppressed, and since it concentrates in the vicinity of the welding point 7, the portion necessary for welding (the vicinity of the welding point 7-Fig. 3
Can be effectively heated.
Therefore, the power supplied from the external power supply 6 to the high frequency heating coil can be reduced. Further, the apex 34a of the bent portion 34 is displaced from the welding point 7 toward the supply side of the metal strip 1, and the bending angle Θ is greater than the angle θ formed by the two abutting surfaces 111 and 112 at the welding point 7. Since it is large, the induction current 8 induced by the high frequency heating coil 3 can be effectively concentrated at the welding point 7. Therefore, the vicinity of the welding point 7 can be effectively heated.

Further, since the high frequency heating coil 3 is wound twice and the winding 31 intersects on the opposite side of the abutting surfaces 111 and 112, the current flowing through the winding 31 on the abutting surfaces 111 and 112 side is reduced. The flow direction is symmetrical with respect to both abutting surfaces 111 and 112. Therefore, both abutting surfaces 11 of the metal strip 1
Since the difference in the softened state between Nos. 1 and 112 is alleviated, it is possible to suppress the occurrence of step defects.

By the way, in the current loop formed by the high frequency heating coil 3, the portion where the power feeding portions 32 and 33 are provided is not a complete closed loop. For this reason,
The induction current is less likely to flow in the portions of the metal strip 1 near the power feeding portions 32 and 33 which are the open portions, as compared with the other portions.
Therefore, suppose that the power feeding portions 32 and 33 are connected to the abutting surfaces 111,
When provided at a position displaced from the 112 side, the power feeding unit 3
The induced current flowing near the abutting surface closer to 2, 33 is smaller than the induced current flowing near the other abutting surface.
Therefore, a difference in the softened state between the abutting surfaces 111 and 112 of the metal strip 1 occurs, and a step defect is likely to occur.

On the other hand, according to this embodiment, since the feeding portions 32 and 33 are provided on the abutting surfaces 111 and 112 side, the difference in the flow of the induced current between the abutting surfaces 111 and 112 is different. It is alleviated, and the occurrence of step defects is suppressed. (Second Embodiment) As shown in FIG. 4, the high frequency heating coil 3 includes the power feeding portions 32 and 3 when viewed from the abutting surfaces 111 and 112.
The present invention can be practiced even if 3 is arranged so as to be symmetrical with respect to the axis.

By the way, the shape of the bent portion 34 is not limited to the V-shape, but may be trapezoidal, semicircular or U-shaped.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an entire electric resistance welded pipe manufacturing apparatus.

2A and 2B are views showing a welded portion of the electric resistance welded pipe manufacturing apparatus according to the present embodiment, where FIG. 2A is a top view and FIG. 2B is a side view.

FIG. 3 is an explanatory diagram showing how an induced current flows.

FIG. 4 is a top view showing a high-frequency heating coil according to a second embodiment.

FIG. 5 is a diagram showing a welded portion of an electric resistance welded pipe manufacturing apparatus according to a conventional technique, (A) is a top view and (B) is a side view.

FIG. 6 is an explanatory diagram showing how an induced current flows.

[Explanation of symbols]

1 ... Metal strip, 2 ... Guide shoe, 3 ... High frequency heating coil, 4, 5 ... Squeeze roll, 6 ... External power supply.

Claims (5)

[Claims] 1. A metal strip (1) in the form of a flat plate, which is supplied from the outside, is pressurized, and the metal strip is curved while having a cylindrical shape so as to have an axis parallel to the traveling direction of the metal strip (1). A squeeze roll (4, which joins both ends of the belt (1)
5) and the metal strip which is arranged in the vicinity of the squeeze rolls (4, 5) and on the supply side of the metal strip (1) from the squeeze rolls (4, 5) and which is curved in a cylindrical shape. Obi (1)
A high-frequency heating coil (3) surrounding the outer periphery of the metal strip (1) is provided on both abutting surfaces (111, 112) side where both ends of the metal strip (1) curved in a cylindrical shape abut, and an external power source (6) is provided. A pair of feeding parts (32, 33) for supplying the high-frequency current from the high-frequency heating coil (3) to the high-frequency heating coil (3). The bent portion (3
4) is formed, and when viewed from the abutting surfaces (111, 112) side, the bent portion (34) is convex on the traveling direction side of the metal strip (1) and curved in a cylindrical shape. An electric resistance welded pipe manufacturing apparatus, characterized in that the bent metal strip (1) is bent so as to be substantially symmetrical with respect to the axis. 2. The apex (34a) of the bent portion (34) is located at a welding point (7) where the abutting surfaces (111, 112) are joined as viewed from the abutting surfaces (111, 112) side. The electric resistance welded pipe manufacturing apparatus according to claim 1, wherein the metal strip (1) is offset on the supply side. 3. The bent portion (34) extends toward the supply side of the metal strip (1) so as to be wider than an angle (θ) formed by the abutting surfaces (111, 112). The electric resistance welded pipe manufacturing apparatus according to claim 1 or 2. 4. The high frequency heating coil (3) is a coil of two turns, and the winding (3) is provided on the opposite side of the abutting surface (111, 112).
4. The method according to claim 1, wherein 1) are crossed.
The electric resistance welded pipe manufacturing apparatus according to any one of 1. 5. A method for manufacturing an electric resistance welded pipe using the electric resistance welded pipe manufacturing apparatus according to claim 1, wherein a flat metal strip (1) is provided with the high frequency heating coil (1). 3)
And a butt surface (11) of the metal strip (1) by applying a high frequency current to the high frequency heating coil (3) of the electric resistance welded pipe manufacturing apparatus.
1, 112) and the both abutting surfaces (111, 1) that are heated and melted in the heating step.
12) A method of manufacturing an electric resistance welded pipe, which comprises a step of pressing and joining the squeeze rolls (4, 5).