JP6923987B1 - Straight seam buried arc arc generator used for welded pipes - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a straight seam buried arc welded pipe arc generator which is highly efficient and easy to install. An embodiment of the present invention includes an arc generator, a cage roll device and a cutting device, the arc generator includes an arc generator tube, a jig and a thermocouple, and the jig is coaxial and arcs. When the generator pipe is tightened and welded, the arc generator pipe and the weld pipe are coaxial, the position of the weld pipe is adjusted by the cage roll device, and the weld pipe and the inclined port of the arc generator pipe overlap. , The tip of the welded pipe is in close contact with the end face of the nearest arc generating pipe, and three pairs of thermocouples are spot welded on both sides of the inclined port of the inner wall surface close to one end of the welded pipe in each arc generating pipe. Provided is an arc generator used for a straight seam buried arc weld pipe, which measures the weld seam temperature by a thermocouple to determine whether the weld arc is stable. [Selection diagram] Fig. 1

Description

The present invention relates to the field of tools for welding steel pipes, and more particularly to arc generators used in straight seam buried arc welded pipes.

In recent years, buried arc welding has played an increasingly important role in straight seam welding of steel pipes, but in the process of buried arc welding, the welding that occurred due to the unstable current at the stage of arc generation. Seams have relatively many quality problems. Then, in order to ensure the quality of welding, it is necessary to always install a welding seam arc generating plate at the tip of the welded joint before welding without using the welding seam until the welding arc becomes stable. .. In order to produce high quality straight seam buried arc welded pipe, the factory assembles two metal plates made of the same material as the raw pipe before welding, and before welding, first two metals. The plate was spot welded to one end of the weld seam to be welded, then an arc was generated on the two metal plates, and when the weld arc moved to the weld seam to be machined, the welding current, voltage and Since the welding arcs are all stable, the quality of the weld seams welded at this time is relatively good. When the welding was completed, the arc generating plate was cut out. However, since the conventional arc generator plate must be abandoned and processed even if it is used only once, the consumption of the material is increased and the resource is greatly wasted. In addition, when the welding is completed, the arc generating plate welded to the steel pipe must be cut, so that the cut port is extremely liable to collapse and the wall surface of the welded pipe is narrowed, which causes a serious problem in the quality of the welded pipe. Will end up. In addition, since it is necessary to spot-weld the arc generating plate to the wall surface at one end of the raw pipe before welding, spot welding always affects the structure of the wall surface at the tip of the welded pipe. Therefore, in order to ensure the quality of the welded pipe, the factory needs to cut the success of the welded pipe by a circle shear after welding, which has a serious influence on the yield rate of the welded pipe. ..

Since it is troublesome to install and cut the conventional arc generator plate and the production efficiency is low, it is possible to provide a straight seam buried arc welded pipe arc generator which is highly efficient and easy to install. , Has important significance in the reality of the process.

The present application can effectively improve the welding quality of a straight seam buried arc welded pipe, increase the yield rate of the welded pipe, and reduce the production cost for defects existing in the prior art. Provided is an arc generator used for an arc welded pipe.

Specifically, one aspect of the present invention provides an arc generator used in a straight seam buried arc welded pipe, including an arc generator, a cage roll device and a cutting device.

The arc generator includes a frame, a plurality of arc generators, a jig, a thermocouple, a guide rail, and a position limiting means, and each arc generator is fixed or moved by the jig, and the jig is supported. There are two crescent-shaped frames with legs, and the two crescent-shaped frames coaxially tighten the arc generating tube with bolts and springs, respectively.

One end of the guide rail is fixed to the frame, the jig can be moved to the guide rail, and the guide rail is provided with the position limiting means at the second end of the guide rail. Moves into contact with the position limiting means, the axes of the arc generating pipe and the welding pipe become the same, and the thermocouple is welded to both sides of the inclined port on the inner wall surface of the arc generating pipe.

The cage roll device includes a weld tube, a cage roll means and a side ring means, the weld tube being supported by a plurality of groups of cage roll means and two groups of cage rolls at one end of the weld tube. A side ring means is attached to the midpoint of the means, and the side ring means can be driven by the driving means so that the welded pipe and the inclined port of the arc generating pipe overlap with each other, and the cage. The roll means can be brought into close contact with the end face of the arc generation pipe closest to the end face of the weld pipe by driving the drive means. The arc generation pipe includes a main arc generation pipe and a sub arc generation pipe, and a plurality of arc generation pipes are installed in the axial direction of the welding pipe so as to be successfully connected, and the sub arc generation pipe is a welding pipe. It is installed near the first end.

The cutting device includes a traveling carriage, a control system, a turning arm, a first connecting arm, a second connecting arm and a cutting gun, the turning arm is attached to the traveling carriage, and the turning arm is a first. The connection arm, the second connection arm, and the cutting gun are sequentially connected, the first servomotor is installed in the direction change arm, the second servomotor is installed in the first connection arm, and the second servomotor is installed. A third servomotor is installed on the connection arm, and the first servomotor, the second servomotor, and the third servomotor are connected to the control system, respectively, and rotate in the forward and reverse directions under the control of the control system. Thereby, the turning arm, the first connecting arm and the second connecting arm are controlled to rotate respectively, the cutting gun is accurately positioned, and the arc generating pipe is directly connected to the end face of the welded pipe. By the action of the cage roll means, they are brought into close contact with each other.

Preferably, a guide rod is further installed on the frame, and the jig moves to the guide rail along the guide rod.

Preferably, a pair of rollers are installed on the support legs of each crescent-shaped frame, and a motor for driving the rollers is fixed to the inside of one of the crescent-shaped frame support legs.

Preferably, the arc generator is provided with an inner layer for preventing pinching on the inner surface of the crescent-shaped frame of the jig.

Preferably, three pairs of the thermocouples are spot-welded to both sides of the inclined port of the inner wall surface close to one end of the welded pipe in each of the arc generating pipes, and the thermocouples are wiring passage holes in the arc generating pipe. The temperature collecting means is connected to the end port of the temperature collecting means, and the temperature collecting means measures the temperature of the welding seam by a thermocouple to determine whether the welding arc is stable or not.

Preferably, the arc generating pipe includes a first arc generating pipe, a second arc generating pipe, a third arc generating pipe, a fourth arc generating pipe, a fifth arc generating pipe, and a sixth arc generating pipe in the welding direction of the welded pipe. The pipe, the seventh arc generation pipe, the eighth arc generation pipe, and the ninth arc generation pipe are included in this order, and the first arc generation pipe to the sixth arc generation pipe are regarded as the main arc generation pipe, and the seventh arc generation pipe is used. The ninth arc generating pipe is used as a sub arc generating pipe.

Preferably, the present invention provides a method of generating an arc in a straight seam buried arc welded pipe including the following steps.

Step S1, the arc generating pipe is attached, the driving means of the side ring means is locked by the side ring means so that the welded pipe and the inclined port of the arc generating pipe overlap, and the welded pipe and the arc generating pipe are locked by the cage roll means. The drive means of the cage roll means is locked after ensuring that the end faces of the cage roll means are in close contact with each other.
In step S2, after detecting the welding seam temperature of the arc generating pipe in real time by the temperature collecting means, the welding equipment is started so that the arc is generated from the first arc generating pipe, and the sixth arc generating pipe is used. When the temperature detected by the three pairs of thermocouples is stably in the range of 1500 0 ° C., the welding arc is considered to be stable, the seventh arc generating tube is suspended, and the motor of the corresponding jig is started. , Take out the 8th arc generating pipe and the 9th arc generating pipe, activate the driving means of the cage roll means, and make the cage roll so that the end face of the welded pipe and the end face of the end of the 7th arc generating pipe come into close contact with each other again. The drive motor of the means is locked, and the welding arc continuously runs stably on the weld pipe.

In step S3, when the welding is completed, the traveling carriage of the cutting device is activated, and the traveling carriage interlocks the cutting guns with the cutting device, and sequentially between the welding pipe, the arc generating pipe, and the plurality of arc generating pipes. When it runs to the seam, it activates the cutting gun and controls it to cool while cutting the weld seam.
In step S4, when the cutting is completed, the arc generating pipe is removed, the arc generating pipe is processed, and the arc generating pipe is rotated counterclockwise by 10 ° with respect to the welding seam, and the inclined port of the arc generating pipe is processed again. , Complete the preparation process. Further, steps S1-S4 are repeated.

Compared with the prior art, the present invention has the following advantages.

1. The present invention improves the arc generating plate used in the conventional straight seam buried arc welding pipe to an arc generating pipe having the same standard as the welding pipe. In the circumferential direction of the welded pipe, the arc generating pipe related to this device corresponds to the one in which multiple arc generating plates are successfully welded seamlessly, and the conventional arc generating plate is used only once. In some cases, it had to be abandoned and treated, while the improved arc generator tube could be used multiple times, improving material utilization. Further, in the axial direction of the welded pipe, the length of the conventional arc generating plate can be confirmed only by the experience of the individual operator, while the arc generating pipe related to this device is divided into a plurality of parts in the axial direction of the welded pipe. Therefore, the quality of the tip of the weld seam of the welded pipe can be ensured, and the length of the arc generating pipe is the shortest, so that the production cost is reduced.

2. In the present invention, as compared with the conventional arc generator, the arc generator according to the present invention is directly attached to the end face of the welded pipe, so that welding is not required before welding, and the end face of the welded pipe It does not affect the structure, and when welding is completed, it becomes easier to cut the arc generating pipe and the welded pipe, and the amount of work to polish the weld seam at the end of the welded pipe is greatly reduced. At the same time, the operation becomes simple and time and effort are saved.

This is an example of a top view of an embodiment of the present invention. It is an example of the front view of one Embodiment of this invention. This is an example of a schematic structural diagram of the cage roll device according to the present invention. This is an example of a schematic structural diagram of the arc generator according to the present invention. It is an example of the structural schematic diagram of the cutting apparatus which concerns on this invention. This is an example of a schematic diagram in which spot welding is performed on the arc generator according to the present invention using a thermocouple. This is an example of a schematic view of an inclined port of an arc generating pipe in the arc generating device according to the present invention.

In order to explain in more detail the technical contents, structural features, objectives and effects to be achieved according to the present invention, the following will be described in detail with reference to the drawings.
An object of the present invention is to provide an arc generator in which the welding quality of a straight seam buried arc welded pipe is effectively improved, and accordingly, the retention rate of the welded pipe is increased and the production cost is reduced. ..

The present invention provides an arc generator used for a straight seam buried arc welded pipe, and as shown in FIGS. 1 to 7, includes an arc generator 2, a cage roll device 1, and a cutting device 3 to generate an arc. The device 2 includes an arc generating tube 23, a jig 22, a thermoelectric pair 21, a motor 27, a guide rail 28, and a position limiting means 29, and each arc generating tube 23 is fixed or moved via the jig 22. , The jig 22 is formed into two crescent-shaped frames having supporting legs, and the arc generation tube 23 is coaxially tightened by both pairs of bolts and springs 24, and the jig 22 and the arc generation tube 23 correspond to each other. A pair of rollers are installed on the support legs of each crescent-shaped frame, and one of the crescent-shaped frames has a small motor 27 having a drive roller inside the support legs. It is fixed, and the jig 23 is moved to the guide rail 28 along the guide rod 26 by the drive of the motor 27, and the guide rail 28 and the guide rod 26 have one end fixed to the frame and the guide rail. A position limiting means 29 is provided at the second end of the 28 apart from the frame, and when the jig 22 is moved in contact with the position limiting means 29, the arc generating pipe 23 and the welding pipe 10 in the jig The axes are the same.

The cage roll device 1 includes a welding pipe 10, a cage roll means 12, and a side wheel means 11, and the side ring means 11 and the welding pipe 10 are controlled to rotate a servomotor, which is a driving means thereof, in the forward and reverse directions. The overlap with the inclined port of the arc generating pipe 23 is satisfied, and the cage roll means 12 controls the servomotor to rotate in the forward and reverse directions so that the welding start end of the welding pipe 10 and the arc at the closest distance to the welding start end are arced. It is satisfied that the end faces of the generation pipe 23 are in close contact with each other.

The cutting device 3 includes a traveling carriage 30, a control system 31, a turning arm 32 and a cutting gun 38, the turning arm 32 is attached to the traveling carriage 30, and the turning arm 32 is a first connecting arm 34, a first. (2) The connection arm 36 and the cutting gun 38 are connected in order, the first servomotor 33 is installed on the direction change arm 32, and the first servomotor 33 is attached to the traveling carriage 30. A second servomotor 35 is installed on the first connection arm 34, a three servomotor 37 is installed on the second connection arm 36, and the second servomotor includes the direction change arm 32 and the first connection arm 34. The third servomotor 37 is installed between the first connecting arm 34 and the second connecting arm 36. The first servomotor 33, the second servomotor 35, and the third servomotor 37 are connected to the control system, respectively, and the control system 31 causes the first servomotor 33, the second servomotor 35, and the third servomotor 37 to be connected to each other. The forward / reverse rotation is controlled, and the cutting gun 38 can be accurately positioned via the rotation of the direction changing arm 32, the first connecting arm 34, and the second connecting arm 36. The arc generating pipe 23 is directly connected to the end face of the welding pipe 10, and when welding is completed, the welding pipe 10 and the arc generating pipe 23 are connected by a welding seam. The arc generating pipe 23 and the welding pipe 10 according to the above do not need to be welded before welding, and only the welding seam needs to be cut after welding. Therefore, cutting the weld seam with the plasma cutting gun 38 can avoid defects caused by cutting by machine and cutting by flame, and when the arc generation tube 23 is cut and processed, it waits for recycling and use. ..

In this specific embodiment, the straight seam buried arc welded steel pipe of X80Φ762 × 19.1 mm has a single surface with a Y-shaped inclined opening, and is made by buried arc welding based on four welding wires, and the size of the inclined opening is large. The value is α = 70 °, d = 6.1 mm, and p = 2 mm.

Further, the length of the weld pipe 23 is 2400 mm and is supported by the cage roll means 12 which is a set of three in the cage roll device 1, and the distance between the two groups of cage roll means 12 in success is a = 1610 mm. The distance between the two groups of cage roll means 12 at the end of the weld pipe 23 is b = 450 mm, and one set is set at the midpoint of the two groups of cage roll means 12 at the tip of the weld pipe 10. The side wheel means 11 is provided, and the servomotors of the cage roll means 12 and the side wheel means 11 are controlled to rotate in the forward and reverse directions. And secure the welding pipe 10 and the end face of the arc generation pipe 23 at the shortest distance from the welded pipe 10 so as to be in close contact with each other by the cage roll means 12.

Specifically, the method for manufacturing the arc generation pipe 23 is as follows.

The raw pipe of the same standard is processed into the required Y-shaped inclined opening. The sloping port means the part where both sides of the steel sheet are joined when the steel sheet is processed through the forming process, that is, the part where the weld wire is melted and should be filled. The surface of the inclined mouth means the welded joint surface of the welded wire and the raw pipe, and the Y-shaped groove indicated by the red circle in the drawing is the cross section of the inclined mouth.

Pre-weld is performed and CO ₂ gas is used for pre-welding to protect the weld. After the pre-welding is completed, deburring is performed, and then the raw pipe is cut into a main arc generating pipe 231 having a length of 100 mm and a sub arc generating pipe 232 having a length of 150 mm by a pipe material cutting mechanism.

The arc generator 2 is composed of six main arc generating pipes 231 having a length of 100 mm and three sub arc generating pipes 232 having a length of 150 mm, and the total length is 1050 mm, which is close to the welded pipe 10. The three arc generation pipes 23 are the sub arc generation pipes 232, and the effect of stabilizing the arc on the arc generation pipe 23 is optimal. In the jig 22, the arc generation pipe 23 is coaxially tightened by the tightening bolt 25, and all of the arc generation pipe 23 are coaxial by the positioning pins and positioning holes provided in the jig 22 and the arc generation pipe 23. , It can be guaranteed that the inclined ports overlap, the jig 22 is attached to the guide rail 28, and the position limiting means 29 is attached to the end of the guide rail 28.

The arc generation pipes are, in order, in the welding direction of the welding pipe, the first arc generation pipe, the second arc generation pipe, the third arc generation pipe, the fourth arc generation pipe, the fifth arc generation pipe, the sixth arc generation pipe, The seventh arc generation pipe, the eighth arc generation pipe and the ninth arc generation pipe are included, and among them, the first arc generation pipe to the sixth arc generation pipe are regarded as the main arc generation pipe, and the seventh arc generation pipe to the ninth arc generation pipe are used. The arc generating pipe is referred to as a sub arc generating pipe. Three pairs of thermocouples 21 are spot-welded on both sides of the inclined port on the inner wall surface at one end close to the welded pipe 10 in each arc generating pipe 23, and the distance between the thermocouples 21 is 10 mm, and the welded pipe 10 The distance from the thermocouple 21 close to the end of the arc generation tube 23 is 15 mm, and the thermocouple 21 is connected to the end port of the temperature collecting means after passing through the wiring passage hole 20 in the arc generation tube 23, and the temperature is increased. The collecting means detects the welding seam temperature by the thermocouple 21 and determines whether or not the welding arc is stable.

Further, as compared with the conventional arc generating plate, in the present invention, the arc generating plate is improved to the arc generating pipe 23 and supported by the jig 22, and the contact area between the arc generating pipe 23 and the welding pipe 10 is large. Since the end face of the welding pipe 10 is in close contact with the end face of the arc generating pipe 23 by the action of the cage roll device 1, welding is not required and the structure of the end face of the welding pipe is not affected. It is possible to easily cut the arc generating pipe 23 and the welding pipe 10 after welding.

Further, in the present invention, the conventional arc generating plate is improved to the arc generating pipe 23, and 12 pairs of arc generating plates are successfully welded by the arc generating pipe 23 in the circumferential direction of the welding pipe 23. It is relative to the thing, and even if the conventional arc generator is used only once, it must be abandoned and processed. That is, if the arc generation tube 23 is produced on a conventional arc generation plate, it can be used only 12 times, but if the arc generation tube 23 according to the present invention is rotated by 10 °, it can be used repeatedly 36 times. The length of the conventional arc generating plate is three times that of the conventional arc generating plate, and the length of the conventional arc generating plate is determined only by experience in the axial direction of the weld pipe 10. If the arc generating plate is too long, the material is wasted. If it is too short, the effect of stabilizing the arc cannot be achieved. In the present invention, by referring to the gist of the finite element method, the arc generation plate is improved to a main arc generation pipe 231 of 100 mm and a sub arc generation pipe 232 of 150 mm, and the number of arc generation pipes 23 is adjusted. On the premise that the effect of stabilizing the arc can be achieved, the material can be omitted as much as possible and the production cost can be reduced.

The process flow of this specific embodiment is as follows.
First, the production and installation of the arc generating pipe 23 are completed, the side ring means 11 of the cage roll device 1 is activated, the welding pipe 10 and the inclined port of the arc generating pipe 23 are guaranteed to overlap, and the side ring means 11 The servo motor of the cage roll means 12 is activated, the welding pipe 10 and the end face of the arc generation pipe 23 are guaranteed to be in close contact with each other, the servo motor of the cage roll means 12 is locked, and the temperature collecting means is used. Is installed so that the sampling frequency of the temperature sensor is 50 Hz, the welding seam temperature of the arc generation pipe 23 is measured in real time, the welding equipment is started, and the welding voltage of the welding equipment is set to 30V and 33V in order. , 34V and 35V, and the welding currents are 450A, 420A, 415A and 410A, the welding speed is 300mm / min, the arc starts to be generated from the first arc generation pipe 23, and the sixth arc is generated. When the temperature detected by the three pairs of thermocouples 21 in the pipe 231 is stably within the range of 1500 50 ° C. (ideal welding temperature), the welding arc is considered to be stable, and the seventh arc generating pipe 232 is set. Hold, activate the motor 27 of the corresponding jig 22, remove the eighth arc generating tube and the ninth arc generating tube 232, lock the servomotor of the side wheel means 11 of the cage roll device 1, and lock the cage roll means 12 The servo motor is activated and the linear velocity is 1000 mm / min (in this process, it takes 3 seconds to detect the temperature with the thermocouple 21. In the process of temperature detection, the welding equipment moves forward by 15 mm to generate the 7th arc. It takes 30 seconds for the welding equipment to travel through the entire 7th arc generation pipe 232 after reaching the tip of the pipe 232, and it takes 6 seconds to remove the 8th arc generation pipe and the 9th arc generation pipe 232. It takes 18 seconds for 10 to move from the end of the 9th arc generation pipe 232 to the end of the 7th arc generation pipe 232, and when the end face of the welded pipe 10 comes into close contact with the end face of the end of the 7th arc generation pipe 232. The distance of the welding equipment to the end of the seventh arc generating pipe 232 is 30 mm), and the end face of the welding pipe 10 and the end face of the end of the seventh sub-arc generating pipe 232 are brought into close contact with each other again to bring the cage roll. The servo motor of the means 12 is locked, the welding arc is continuously running stably on the welding pipe 10, and when welding is completed, the traveling trolley 30 of the cutting device 3 is activated, and the traveling trolley is operated by the control system 31. 30 is controlled to interlock the cutting gun 38, and the welding pipe 10, the arc generation pipe 23, and a. It runs to the seam with the heat treatment pipe 23, activates the cutting gun 38, cools while cutting the weld seam, removes the arc generation pipe 23 when the cutting is completed, and removes burrs from the arc generation pipe 23. If necessary, heat treatment is performed, and the weld seam before that is rotated counterclockwise by 10 ° to reprocess the inclined port of the arc generation pipe to complete the preparation process. Moreover, the above steps are repeated.

Further, the arc generator according to the present invention may be used as an arc extinguishing device when attached to the end of the welding seam of the welding pipe 10.

The examples described above are for explaining preferred embodiments of the present invention, and do not limit the scope of the present invention. All modifications and amendments to the technical means of the present invention by those skilled in the art are included in the claims of the present invention, as long as they do not deviate from the gist of the present invention.

1 Cage roll device 10 Welding pipe 11 Side wheel means 12 Cage roll means 2 Arc generator 20 Wiring passage hole 21 Thermoelectric pair 22 Jig 23 Arc generator 231 Main arc generator 232 Secondary arc generator 24 Spring 25 Bolt 26 Guide rod 27 Motor 28 Guide rail 29 Position limiting means 3 Cutting device 30 Traveling trolley 31 Control system 32 Direction change arm 33 First servo motor 34 First connection arm 35 Second servo motor 36 Second connection arm 37 Third servo motor 38 Cutting gun

Claims (5)

Including arc generator, cage roll device, and cutting device
The arc generator includes a frame, a plurality of arc generators, a jig, a thermocouple, a guide rail, and a position limiting means, and each arc generator is fixed or moved by the jig. , Two crescent-shaped frames with support legs, the two crescent-shaped frames, respectively, coaxially tightening the arc generating tube with bolts and springs.
One end of the guide rail is fixed to the frame, the jig can be moved to the guide rail, and the guide rail is provided with the position limiting means at the second end, and the jig is installed. When the position limiting means is moved and contacted, the axes of the arc generating pipe and the welding pipe become the same line, and the thermocouple is welded to both sides of the inclined port on the inner wall surface of the arc generating pipe.
The cage roll device includes a weld tube, a cage roll means, and a side ring means, the weld tube being supported by a plurality of groups of cage roll means, of two groups at one end of the weld tube. A side ring means is attached to the midpoint of the cage roll means, and the side ring means can be made so that the welded pipe and the inclined port of the arc generating pipe overlap by the driving of the driving means. The cage roll means can be brought into close contact with the end face of the arc generation pipe closest to the end face of the welded pipe by driving the drive means.
The arc generation pipe includes a main arc generation pipe and a sub arc generation pipe, and a plurality of arc generation pipes are installed in the axial direction of the welding pipe so as to be successfully connected, and the sub arc generation pipe is a welding pipe. Installed near the first end,
The cutting device includes a traveling carriage, a control system, a turning arm, a first connecting arm, a second connecting arm and a cutting gun, the turning arm is attached to the traveling carriage, and the turning arm is a first. The connection arm, the second connection arm, and the cutting gun are sequentially connected, the first servomotor is installed in the direction change arm, and the second servomotor is installed in the first connection arm. A third servomotor is installed on the second connection arm, and the first servomotor, the second servomotor, and the third servomotor are respectively connected to the control system, and are forward and reverse under the control of the control system. By rotating, the direction changing arm, the first connecting arm and the second connecting arm are controlled to rotate respectively, the cutting gun is accurately positioned, and the arc generating pipe is directly connected to the end face of the welded pipe. An arc generator used in a straight seam buried arc welded pipe, characterized in that it is brought into close contact by the action of a cage roll means. The straight seam buried arc welded pipe according to claim 1, wherein a guide rod is further installed on the frame, and the jig moves to the guide rail along the guide rod. The arc generator used. A pair of rollers are installed on the support legs of each crescent-shaped frame, and a motor for driving the rollers is fixed to the inside of one of the crescent-shaped frame support legs. The arc generator used for the straight seam buried arc welded pipe according to claim 1. The arc generator used for a straight seam buried arc welded pipe according to claim 3, wherein the arc generator is provided with an inner layer for preventing pinching on the inner surface of the crescent-shaped frame of the jig. .. Three pairs of the thermocouples are spot-welded to both sides of the inclined port of the inner wall surface close to one end of the welded pipe in each of the arc generating pipes, and the thermocouples pass through a wiring passage hole in the arc generating pipe. The temperature collecting means is connected to the end port of the temperature collecting means, and the temperature collecting means measures the temperature of the weld seam by a thermocouple to determine whether or not the welding arc is stable. The arc generator used for the straight seam buried arc welded pipe according to 1.

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