JP2910335B2 - High frequency ERW pipe welding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency electric resistance welded tube welding apparatus for forming a tube having a V-shaped gap by bending a tube material and continuously welding the V-shaped gap with a high-frequency current.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional welding apparatus for a high-frequency electric resistance welded pipe manufacturing line. Reference numeral 1 denotes a tube material, which is formed into a tube having a V-seam 2 by a multi-stage forming roll (not shown), and is transferred in the direction of the arrow in the figure. A high-frequency current (welding current) I is applied to the V seam 2 by the power source 3 and the contacts 4a, 4b to heat the facing edges 2a, 2b of the V seam 2, and then pressurized from both sides by squeeze rolls 5a, 5b. Thus, welding was continuously performed at the joint point 10.

FIG. 6 shows how the edges are joined. In this figure, the portions to be heated are hatched. As shown in FIG. 7A, it is preferable that the tip of the edge is heated flat. In this type of apparatus, the welding current I is set to a high frequency and the proximity effect of the current between the opposing edges is enhanced. Therefore, the edge effect of the current is also remarkable.

Therefore, especially in the case of a thick-walled tube having a large wall thickness t, as shown in FIG. 1B, the edge effect is strongly exerted and the current I flows more concentratedly at the corners of the edge. The outer and inner corners are heated more strongly than the center. In this state, when the edges are pressed against each other by the squeeze roll, the corners are overheated and melted as shown in FIG. (C), and the molten metal is scattered or spattered by the electromagnetic force due to the electromagnetic force, or is overheated. Since the metal at the corners remains without being discharged, entrapment of metal oxides and generation of pinholes occur, thereby impairing welding quality.

Conventionally, therefore, especially in the case of an apparatus for producing a thick-walled pipe, a preheating section 7 for preheating the edge portion is provided in front of the seam welded section 6 having the above-mentioned structure as shown in FIG. See Japanese Patent Application No. 2-139244). This preheating section 7
For example, an inductor 8 and a power supply 9 for supplying medium-frequency or low-frequency power to the inductor 8 are provided. The inductor 8
Iron core 8 located inside and outside of tube material 1 so as to sandwich tube material 1
a. Power of a relatively low frequency is supplied to the inductor 8 from a power supply 9 to heat portions of the edges 2a and 2b that overlap the core 8a. By thus preheating the edges 2a and 2b evenly to as high a temperature as possible with low frequency power having a relatively small edge effect, the width of temperature rise in the seam welded portion 6 is reduced, and the corners of the edges and The welding was performed by reducing the temperature difference in the central part.

[0006]

However, in the above conventional apparatus, although the welding quality is improved, the edge is heated at a relatively low frequency in order to preheat the edge uniformly to a high temperature in the thickness direction. Therefore, there is a problem that power consumption increases and running costs increase. Further, in order to perform such preheating, a power source having a relatively low frequency and a large output is required as the power source 9 for preheating, which has caused problems such as complicated equipment and increased equipment cost.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention improves the current distribution at the edge to uniformly heat the edge in the high-frequency electric resistance welded pipe welding apparatus, and eliminates the need for measures such as preheating of the edge. It is intended to be.

[0008]

SUMMARY OF THE INVENTION The present invention provides
In order to achieve the above object, a tube material to be transferred is curved to form a tube having a V-shaped gap, and a high-frequency current (welding current) is applied to a pair of opposite edges of the V-shaped gap. In the device that performs continuous electric welding
A conductive member is arranged in the V-shaped gap. The conductive member has a pair of side surfaces having a width smaller than the thickness of the edge portion which is close to and opposed to the pair of edge portions of the V-shaped gap.
The side surface of the conductive member is disposed substantially at the center in the thickness direction of the edge portion and opposed to the edge portion. When a welding current is applied to a pair of edges of the V-shaped gap, the current generates an alternating magnetic field in the V-shaped gap. A circulating current is generated in the conductive member by the magnetic flux of the alternating magnetic field. A proximity effect acts between the circulating current and the welding current, and the circulating current flows through a pair of side surface layers of the conductive member. This proximity effect also acts on the welding current, which leads to a uniform distribution of the welding current at the edges and to a more uniform heating of the edges.

Further, instead of disposing a conductive member in the V-shaped gap, an ionizing gas may be injected into the V-shaped gap by gas injection means, and the ionizing gas may be used in place of the conductive member. is there. In the same manner as described above, the ionizing gas injected into the V-shaped gap causes a circulating current to flow by an alternating magnetic field, and is sealed along a pair of edges of the V-shaped gap by Lorentz force. The proximity effect due to the circulating current of the ionizing gas acts on the welding current, and the uniformity of the distribution of the welding current is improved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a main part of a welding apparatus for a high-frequency electric resistance welded pipe manufacturing line according to a first embodiment of the present invention. As shown in this figure, in the first embodiment, a conductive piece 10 is arranged in a V-shaped gap 2. The conductive piece 10 is a wedge-shaped member having a thickness smaller than the plate thickness of the tube material 1.
1 is supported at a predetermined position. That is, the conductive piece 10 has a pair of side surfaces 10a and 10b which are close to and opposed to a pair of edges 2a and 2b of the V-shaped gap 2, and the side surfaces 10a and 10b are edges 2 of the V-shaped gap 2.
It is supported at a position facing a substantially central portion in the thickness direction of a and 2b (see FIG. 2A). As a material of the conductive piece 10, a metal having high conductivity such as copper is used.

When a high-frequency welding current I flows through the edges 2a and 2b of the V-shaped gap 2, an alternating magnetic field is generated in the V-shaped gap 2. Since the magnetic flux of the alternating magnetic field crosses the conductive piece 10, an induced current i circulating in the conductive piece 10 is generated. This is shown in FIG. Since the proximity effect works between the induced current i and the welding current I, the induced current i
It flows on the surface layers 0a and 10b. Further, the welding current I also changes its current distribution due to the proximity effect, and the side surface 1 of the conductive piece 10 is changed.
The current distribution at the central portion of the edges 2a, 2b facing 0a, 10b increases, and the current at the corners of the edges 2a, 2b deviating from the side surfaces 10a, 10b decreases. As a result, the current distribution in the thickness direction of the edges 2a, 2b is made uniform, and the uniformity of the heating of the edges 2a, 2b is improved. Therefore, good welding quality can be obtained without taking measures such as preheating the edges 2a and 2b with relatively low frequency power.

Further, since the conductive piece 10 is formed of a metal such as copper having a low electric resistance as described above, the heat generation of the conductive piece 10 due to the induced current i can be small, but the conductive piece 10 melts red due to heat storage. It is desirable to provide a cooling means so as not to be damaged. As the cooling means, for example, a cooling medium circulation pipe is provided inside the conductive piece 10, and a cooling medium supply pipe and a discharge pipe are used as the support member 11, and the cooling medium is circulated through the cooling medium circulation pipe to perform cooling. Configuration can be taken. In this case, the cooling medium may be either a gas or a liquid, but an inert medium or a reducing medium is used so that the conductive piece 10 does not corrode.

FIG. 3 shows a main part of a high-frequency electric resistance welded pipe manufacturing line according to a second embodiment of the present invention. As shown in this figure, in the second embodiment, a nozzle 12 for injecting an ionizing gas is used.
Are provided near the V-shaped gap 2. As the ionizing gas, a gas combustion flame or a non-transferring plasma gas can be used. When the ionizing gas is injected into the V-shaped gap 2 by the nozzle 12 during welding, an induced current i is generated in the ionizing gas by the magnetic flux of the alternating magnetic field due to the welding current I, as in the first embodiment. This is shown in FIG. The ionizing gas is supplied to the pair of edges 2a, 2a of the V-shaped gap 2 by Lorentz force acting between the ionizing gas and the welding current I.
b. The proximity effect acts on the welding current I by the induced current i circulating in the contained ionized gas, and the current distribution of the welding current I is improved as in the first embodiment.

When a gas combustion flame or a non-transferring plasma gas is used as the ionizing gas, the gas temperature is increased, so that there is an advantage that heating of the edges 2a and 2b can be compensated. Especially in the case of plasma gas, gas combustion flame temperature (about 2300 ° K)
The temperature is several times higher than the above, which is advantageous in terms of heating compensation. Note that an inert or reducing gas is used as the plasma gas so as not to generate a metal oxide in the welded portion.

[0016]

As described above, according to the present invention,
A circulating current is generated in the conductive member or the injected ionizing gas disposed in the V-shaped gap, and the uniformity of the distribution of the welding current can be improved by the proximity effect with the circulating current. Therefore, the uniformity of the heating of the pair of edges of the V-shaped gap is enhanced, and good welding quality can be obtained. This is particularly effective for welding a thick-walled pipe. Therefore, there is no need to take measures such as preheating the pair of edges of the V-shaped gap, and there is an advantage that the facility can be simplified and the running cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing a main part of a high-frequency electric resistance welded pipe welding apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an induced current flowing through a conductive piece.

FIG. 3 is a plan view showing a main part of a high-frequency electric resistance welded pipe manufacturing line according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an induced current flowing in an ionizing gas.

FIG. 5 is a perspective view showing the concept of a conventional high-frequency electric resistance welded pipe welding apparatus.

FIG. 6 is an explanatory view showing a state of joining of edges in electric resistance welded pipe welding.

FIG. 7 is a perspective view showing a main part of a conventional electric resistance welded pipe welding machine for thick-walled pipes.

[Explanation of symbols]

 2 V-shaped gap 10 Conductive piece 1 Tube material 11 Support member 2a, 2b A pair of edges 10a, 10b A pair of side surfaces 12 Ionizing gas injection nozzle

Claims (2)

(57) [Claims] 1. A tube material to be transferred is curved to form a tube having a V-shaped gap, and a high-frequency current is applied to a pair of opposite edges of the V-shaped gap to continuously perform electric welding. In the apparatus, a conductive member is disposed in the V-shaped gap, and the conductive member has a pair of side surfaces that are close to and opposed to a pair of edges of the V-shaped gap, and the width of the pair of side surfaces is Is smaller than the thickness of the pair of edges, and the pair of side surfaces are located substantially at the center in the thickness direction of the pair of edges , and are generated in the V-shaped gap by the high-frequency current.
Circulating in this conductive member by the magnetic flux of the alternating magnetic field
An electromotive current is generated, and the vicinity of the induced current and the high-frequency current is generated.
Due to the contact effect, the center of the edge facing the side of the conductive member
Current on the edge of the conductive member
To reduce the current portion at the
A high-frequency electric resistance welded pipe welding apparatus characterized in that the current distribution in the vertical direction is made uniform . 2. The high-frequency electric resistance welded welding apparatus according to claim 1, further comprising gas injection means for injecting an ionizing gas into said V-shaped gap, instead of said conductive member, wherein said V-shaped by said high-frequency current. An alternating magnetic field generated in the gap generates an induced current in the ionizable gas,
The gas is subjected to the Lorentz force acting between it and the high-frequency current.
Therefore, it is sealed along a pair of edges of the V-shaped gap.
The induced current circulating in the enclosed ionizable gas.
The proximity effect on the high-frequency current to reduce the edge current distribution.
A high-frequency electric resistance welded pipe welding device characterized by being made uniform .