JP5879087B2 - Circumferential welding method of fixed pipe and consumable electrode type gas shielded arc automatic welding equipment - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a fixed pipe circumferential welding method and a consumable electrode type gas shielded arc automatic welding apparatus applied when welding butt ends of pipelines (horizontal fixed pipes) of, for example, oil or natural gas. .

  Consumable electrode type gas shielded arc welding may be used in circumferential butt welding of ends of steel pipes (horizontal fixed pipes) when laying a pipeline. In this welding, an annular traveling rail constituting an automatic welding apparatus is attached along the outer periphery of the butt end of two fixed pipes, and welding is performed while moving the welding head along the traveling rail.

  The welding head includes a carriage that moves on the traveling rail and a torch mounted on the carriage, and the welding wire fed to the torch is melted by the heat generated by the arc discharge, so that the fixed pipe Weld the butt ends. The fixed pipe is processed by machining or gas cutting so that the outer surface of the steel pipe is widened, and this processed surface is generally called a groove. The torch is swung (weaved) to sufficiently melt the groove (wall). In addition, the automatic welding device includes a control device (control panel) for controlling the moving direction and moving speed of the carriage of the welding head, the weaving conditions of the torch, the feeding speed of the welding wire to the torch, A wire feeder that supplies a welding wire to the torch, a welding power source for generating arc discharge, a gas cylinder for sending shield gas, a gas supply mechanism, and the like are provided.

  When circumferentially welding the butt end of a fixed pipe using such an automatic welding apparatus, the thickness of the weld bead obtained by one run of the welding head cannot be made too thick from the viewpoint of preventing the occurrence of welding defects. When welding thick fixed pipes, multi-layer welding is performed in which welding heads are moved to the same portion a plurality of times along the circumferential direction for welding.

  As an effective technique for efficiently performing multi-layer welding, an automatic welding apparatus equipped with a dual torch type welding head in which two torches are mounted on one welding head is known in Patent Document 1 and the like. This automatic welding apparatus is provided with a leading torch and a trailing torch at a predetermined interval in the welding direction along the circumference of one welding head, and by moving the welding head at a predetermined speed in the welding direction. While forming a bead with a leading torch, a bead with a trailing torch is stacked on the bead at a predetermined interval, and welding is performed at an efficiency about twice that of a single torch welding head. Is possible.

  In welding with two torches, a leading torch and a trailing torch, magnetic interference (arc interference) occurs between the electrodes, so welding must be performed under such welding conditions that the arc state is stable when the two torches are fired simultaneously. Although it is difficult to set the welding conditions, the trailing torch can be welded before the temperature of the welding bead formed by the preceding torch drops, so it achieves deep penetration with a small current. As compared with the case of welding with a single torch, there is an advantage that welding can be performed with the welding current lowered.

  By the way, in the case of the automatic welding apparatus provided with the conventional dual torch type welding head described in Patent Document 1, a welding sequence is performed while moving the welding head in one direction along the circumference of the fixed pipe. Therefore, for example, the circumferential position of the horizontal fixed pipe is expressed by the clock position, the highest point position is 12 o'clock position, the lowest point position is 6 o'clock position, and one of the intermediate points between 12 o'clock and 6 o'clock When the position on the side is 3 o'clock and the position on the other side is 9 o'clock, if the 3 o'clock position is downward welding toward the lower side, the 9 o'clock position is upward welding toward the upper side End up. That is, there is a problem that the total welding speed cannot be increased because the welding proceeds upward in any region of the circuit.

In view of this, a dual head / dual torch type automatic welding apparatus is known in Patent Document 2 and the like as a solution to the problem.
FIG. 3 shows an entire system of an example of a dual head / dual torch type automatic welding apparatus. This system includes steel pipes 21 and 22, a clamp 23 equipped with a copper backing for forming a back wave, a guide rail 24, two welding heads 25 each equipped with a leading torch and a trailing torch (not shown), and a welding head control. A panel 26, a wire feeder 27 for supplying a welding wire to the welding head 25, a welding power source 28, and a shield gas supply system 29 are configured. The steel pipes 21 and 22 are fixed by a clamp 23 equipped with a copper backing for forming a back wave. The welding head 25 is welded while moving at a predetermined speed on the guide rail 24 attached on the steel pipes 21 and 22.

  As described above, in the automatic welding apparatus equipped with the two welding heads 25, in order to improve the welding efficiency, that is, the welding speed, the downward split welding is usually performed using the two welding heads 25. That is, the welding is divided by the two welding heads 25 from the 12 o'clock position to the 3 o'clock direction and the 12 o'clock position to the 9 o'clock direction, and welding is performed at the 6 o'clock position. Welding sequence is performed. At that time, a pre-welding process in which welding is performed by moving the preceding welding head downward from the 12 o'clock position through the 3 o'clock position to the 6 o'clock position, and from the 12 o'clock position through the 9 o'clock position, 6 The subsequent welding process in which the welding head on the subsequent side is moved downward to the hour position and welding is performed in this order with a predetermined time difference.

JP 2011-11248 A JP 2011-20130 A

  However, when the downward vibration welding is performed, it is necessary to connect the weld beads at the 6 o'clock position of the fixed pipe, which causes another problem that a weld defect is likely to occur at the joint portion of the beads.

  For example, in general, at the welding end portion, in order to prevent bead dents and cracking of the crater, the arc and welding wire supply is held for several seconds with the welding head carriage stopped, so-called “crater processing”. However, in the case of the welding head concerned, since two torches are mounted on one welding head, in order to insert a crater, it is preceded at the time of welding by the welding head on the preceding side (3 o'clock side). It is necessary to stop the torch and the trailing torch at the same time. When the leading torch and the trailing torch are stopped at the same time, the weld bead between the leading torch and the trailing torch (between the poles) becomes a weld bead welded only with the leading torch. Welding with the welding head on the side). In that case, it has been found that the following problems occur depending on the method of proceeding the welding process with the welding head on the subsequent side. In this section, we will discuss the details of the two ways of proceeding.

First, the welding method of the first study example will be described with reference to FIGS. 4 and 5, and then the welding method of the second study example will be described with reference to FIGS. 6 and 7.
4 to 7, reference numeral 1 denotes a steel pipe (horizontal fixed pipe), 11A denotes a leading welding head, 11B denotes a trailing welding head, 9 and 10 denote leading torches mounted on the welding heads 11A and 11B, and It is a trailing torch. Further, 2 is a weld bead formed by the leading torch 9 of the preceding welding head 11A, 3 is a welding bead formed by the trailing torch 10 of the preceding welding head 11A, and 4 is the welding bead of the subsequent welding head 11B. A weld bead formed by the preceding torch 9, 5 is a weld bead formed by the trailing torch 10 of the succeeding welding head 11 </ b> B, and 6 is a welding end portion capable of crater treatment (also referred to as a crater-treated weld end portion). ), 7 is a welding end portion (also referred to as an untreated crater portion) that cannot be cratered, and 8 is a single-layer weld bead welded only to the leading torch 9 of the preceding welding head 11A. This is a portion (referred to as a “single-layer bead portion 8” for convenience) that is melted by the torch (either the leading torch 9 or the trailing torch 10) of the head 11B.

  FIG. 4 is a process explanatory view showing a first examination example of how to connect the weld bead at the 6 o'clock position of the fixed pipe, and FIG. 5 is a structure of the joint portion of the bead at 6 o'clock position obtained in the process. FIG.

  In the welding method of the first examination example, as shown in FIG. 4 (a), the leading side (3 o'clock side) welding head 11A is moved in the direction of arrow A (clockwise) at the 6 o'clock position. When finishing the welding, the leading torch 9 and the trailing torch 10 are simultaneously cratered to finish the welding. Therefore, the welding end portion 6 subjected to the crater treatment is formed at the end point of the welding by the leading torch 9 and the trailing torch 10. Next, as shown in FIG. 4B, when the succeeding side (9 o'clock side) welding head 11B is moved in the direction of arrow B (counterclockwise) to reach the 6 o'clock position, the leading torch 9 wraps the end of the weld bead 2 formed by the preceding torch 9 mounted on the preceding (3 o'clock) welding head about several millimeters and finishes the welding. At this time, the welding of the succeeding torch 10 is continued, and the leading torch 9 ends the welding without the crater process. Therefore, the crater unprocessed portion 7 left at the end point of the welding by the preceding torch 9 may have a dent. Next, as shown in FIG. 4C, crater processing is performed by the trailing torch 10 at the welding end stage of the trailing torch 10 that continues welding.

  In this case, as shown in FIGS. 4C and 5, the single-layer bead portion indicated by reference numeral 8 (the bead portion welded only by the preceding torch 9 of the preceding welding head 11 </ b> A) is The bead is piled up by the trailing torch 10 of the welding head 11B. However, in this portion, since the low heat input welding is performed on the bead 2 which has been cooled, defects such as poor fusion occur. The possibility increases.

  That is, the single-layer bead portion indicated by reference numeral 8 must be welded with a single torch (the trailing torch 10 of the succeeding side welding head 11B) in order to match the total stacking height. Since the welding of the row torch 10 is insufficient, the current is insufficient, and the influence of magnetic interference is suddenly eliminated, so that the arc becomes somewhat unstable, and as a result, there is a high possibility that a welding defect (fusion failure) will occur.

  In addition, a measure for increasing the current immediately after the trailing torch 10 becomes a single arc at the position can be considered. However, in order to sufficiently melt the single-layer bead portion 8 formed by the preceding torch 9 of the preceding welding head 11A and having a lowered temperature, it is necessary to increase the current greatly. Increasing the amount raises the new problem of increasing the possibility of hot cracking.

Next, the welding method of the second study example will be described.
FIG. 6 is a process explanatory view showing a second examination example of how to connect the weld beads at the 6 o'clock position of the fixed pipe, and FIG. 7 is the structure of the connection portion of the 6 o'clock bead obtained in the process. FIG.

  In the welding method of the second examination example, as shown in FIG. 6A, the leading side (3 o'clock side) welding head 11A is moved in the direction of arrow A (clockwise) at the 6 o'clock position. When finishing the welding, the leading torch 9 and the trailing torch 10 are simultaneously cratered to finish the welding. Therefore, the welding end portion 6 subjected to the crater treatment is formed at the end point of the welding by the leading torch 9 and the trailing torch 10. Next, as shown in FIG. 6B, when the succeeding side (9 o'clock side) welding head 11B is moved in the direction of arrow B (counterclockwise) to reach the 6 o'clock position, the leading torch 9 and the succeeding torch 10 are simultaneously subjected to crater treatment to complete the welding. Thus, since it is possible to put a crater process in all the welding termination | terminus parts, the dent and crater crack in a termination | terminus part do not generate | occur | produce. Further, a single-layer bead portion 8 (same layer as the bead 2) formed only by the preceding torch 9 of the preceding welding head 11A is beaded by the preceding torch 9 of the succeeding welding head 11B having a high heat input. 4 are stacked, the boundary portions of the beads 2 and 4 are sufficiently fused.

  However, in this portion, the bead cross-sectional depth position in the welded portion changes abruptly because the bead 4 of the leading torch 9 of the succeeding welding head 11B is superimposed on the single-layer bead portion 8. As a result, the groove widens rapidly, so that the weaving width (amplitude) of the leading torch 9 of the welding head 11B on the subsequent side becomes insufficient, and there is a possibility that poor fusion occurs between the groove wall and the bead. Come.

  As described above, there is a problem that it is difficult to completely prevent the occurrence of welding defects (fusion defects) when the welding method of any of the examination examples is performed.

  In consideration of the above circumstances, the present invention provides a circumferential welding method for a fixed pipe and a consumable electrode type gas shielded arc automatic welding apparatus that can almost completely eliminate welding defects that tend to occur in the joint portion of the bead. With the goal.

In order to solve the above-mentioned problem, the circumferential welding method of the fixed pipe of the invention of claim 1 is arranged in the circumferential direction along the butt end portion of the horizontal fixed pipe and spaced apart from each other in the circumferential direction. In the method of circumferential welding of a fixed pipe using a consumable electrode type gas shielded arc automatic welding apparatus that arc welds the butt end with the plurality of torches by moving a welding head having a plurality of torches, the horizontal fixing The position of the pipe in the circumferential direction is expressed as a clock position, the highest point position is 12 o'clock, the lowest point position is 6 o'clock, and the position on one side of the midpoint between 12 o'clock and 6 o'clock is 3 o'clock When the position on the other side is the 9 o'clock position, the welding head is divided into the 3 o'clock direction from the 12 o'clock position and the 9 o'clock direction from the 12 o'clock position to proceed welding, Downward split welding is performed to connect the beads at the position. In particular, a pre-welding process in which welding is performed by moving the welding head downward from the 12 o'clock position to the 6 o'clock position via the 3 o'clock or 9 o'clock position, and the 9 o'clock or 3 o'clock position from the 12 o'clock position. And a subsequent welding process in which welding is performed by moving the welding head downward to the 6 o'clock position in this order with a predetermined time difference, and the welding end positions of the plurality of torches in the preceding welding process are the same position. And the welding end position of each of the plurality of torches in the subsequent welding process is set to the same position to complete one round of welding, and the plurality of torches in the preceding welding process and the subsequent welding process Each has a leading torch and a trailing torch, and the trailing torch removes the dent generated in the crater untreated portion of the leading torch by cutting the arc at the welding end position of the leading torch. And wherein the filling by the crater treatment with welding end position.
Two welding heads may be provided, one of which may be used for a preceding welding process and the other may be used for a subsequent welding process.

A consumable electrode type gas shielded arc automatic welding apparatus according to a third aspect of the present invention comprises a carriage that moves on a traveling rail disposed in a circumferential direction along a butt end portion of a horizontal fixed pipe, and the carriage along the circumference. A welding head having a plurality of torches arranged apart from each other in the welding direction, and moving the carriage of the welding head in a circumferential direction along a running rail, while the butt end portion is moved by the plurality of torches. The consumable electrode type gas shielded arc automatic welding apparatus for arc welding includes two welding heads and welding control means for controlling the operations of the two welding heads. The position of the horizontal fixed pipe in the circumferential direction is expressed by the clock position, the highest point position is 12 o'clock position, the lowest point position is 6 o'clock position, and the middle position between 12 o'clock and 6 o'clock. Is set to the 3 o'clock position and the other side position is set to the 9 o'clock position, the two welding heads respectively change the position from 12 o'clock to 3 o'clock and 12 o'clock to 9 o'clock. Welding is carried out in a distributed manner, and the downward split welding is performed in which the beads are joined at the 6 o'clock position. From the 12 o'clock position through the 3 o'clock or 9 o'clock position, the welding on the leading side Pre-welding process in which welding is performed by moving the head downward, and subsequent welding in which welding is performed by moving the subsequent welding head downward from 6 o'clock through 9 o'clock or 3 o'clock to 6 o'clock. And the processes are executed in this order with a predetermined time difference, the welding end positions of the plurality of torches in the preceding welding process are set to the same position, and the welding end positions of the plurality of torches in the subsequent welding process All the same And it is set to the position control is performed to terminate the welding of one rotation, a plurality of torches in the prior welding process and the subsequent welding process is provided with the respective preceding torch and the trailing torch the carriage, said previous torch By cutting the arc at the welding end position, the dent generated in the crater untreated portion of the preceding torch is filled by performing crater processing at the welding end position of the subsequent torch .
The “same position” as used in claims 1 and 3 refers to a range in which the molten metal spreads when the welding object and the torch are welded to each other, and specifically, the tip of the torch of the welding object. An area that is within a range of 15 mm in the front-rear direction with the opposite part as the center.

According to the first and third aspects of the invention, since the welding end position by each of the plurality of torches arranged on the welding head is set to the same position, it is preceded by the crater process by the last torch of the welding head. The weld defect of the untreated crater due to the torch can be melted, and can be removed by filling the dent or remelting the crater crack. This can be said in the same manner in the two welding heads that perform downward vibration welding, so that the welding defects at the joint portion of the beads can be almost completely eliminated.
Further, since the welding end positions of the plurality of torches in the preceding welding process and the welding end positions of the plurality of torches in the subsequent welding process are set to the same position, the bead welded only by the preceding torch of the welding head in the preceding welding process Thus, there is no portion (the above-described single-layer bead portion (the portion indicated by reference numeral 8 in FIGS. 5 and 7)) that needs to be melted by the torch of the welding head in the subsequent welding step, and the subsequent welding step Problems caused by laminating beads with the torch of the welding head can be avoided.

It is process explanatory drawing of the welding method of embodiment of this invention, (a) is a figure which shows the state of the welding end time by the preceding torch of a preceding welding head, (b) is by the following torch of the preceding welding head. The figure which shows the state at the time of completion | finish of welding, (c) is a figure which shows the state at the time of the welding end by the preceding torch of the subsequent welding head, (d) is the state at the time of the completion of welding by the subsequent torch of the subsequent welding head FIG. It is a figure which shows the structure of the connection part of the bead of the 6 o'clock position obtained by implementation of all the processes of FIG. It is a figure which shows the whole system of an example of a dual head dual torch type automatic welding apparatus. BRIEF DESCRIPTION OF THE DRAWINGS It is process explanatory drawing of the welding method of the 1st examination example prior to this invention, (a) is a figure which shows the state at the time of the completion | finish of welding by the preceding torch and the succeeding torch of a preceding welding head, (b) is a succeeding side. The figure which shows the state at the time of the completion | finish of welding by the preceding torch of the welding head of FIG. It is a figure which shows the structure of the connection part of the bead of the 6 o'clock position obtained by all the processes of FIG. It is process explanatory drawing of the welding method of the 2nd examination example prior to this invention, (a) is a figure which shows the state at the time of completion | finish of welding by the preceding torch and the succeeding torch of a preceding welding head, (b) is a succeeding side. It is a figure which shows the state at the time of completion | finish of welding by the preceding torch of a welding head, and a succeeding torch. It is a figure which shows the structure of the connection part of the bead of the 6 o'clock position obtained by all the processes of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The cylindrical tube circumferential welding apparatus of this embodiment is a consumable electrode type gas shielded arc automatic welding apparatus, and the entire system has a configuration substantially similar to that shown in FIG. That is, the apparatus includes two welding heads that move along the traveling rail, a welding control device that controls the operations of the two welding heads, a wire feeder that supplies a welding wire to the welding head, and the like. Each welding head is arranged with a carriage moving on a traveling rail (guide rail) arranged in the circumferential direction along the butt end of the horizontal fixed pipe, and spaced apart in the welding direction along the circumference. Each of these components has a leading torch and a trailing torch, and these components are arranged around the rail of the welding head along the traveling rail by a control command issued from a welding control means (welding head control panel). While moving in the direction, the butt end is operated by arc welding according to a predetermined welding sequence by the leading torch and the trailing torch.

Next, the welding sequence (that is, the welding method) will be described in detail.
FIG. 1 is a process explanatory diagram of the welding method of the embodiment, (a) is a diagram showing a state at the end of welding by a preceding torch of a preceding welding head, and (b) is a trailing torch of the preceding welding head. The figure which shows the state at the time of completion | finish of welding, (c) is a figure which shows the state at the time of the welding end by the preceding torch of the subsequent welding head, (d) is the state at the time of the completion of welding by the subsequent torch of the subsequent welding head FIG. FIG. 2 is a view showing the structure of the connecting portion of the bead at the 6 o'clock position obtained by performing all the steps in FIG.

  1 and 2, reference numeral 1 is a steel pipe (horizontal fixed pipe), 11A is a leading welding head, 11B is a trailing welding head, 9 and 10 are leading torches and rear mounted on the welding heads 11A and 11B, respectively. Is a line torch. Further, 2 is a weld bead formed by the leading torch 9 of the preceding welding head 11A, 3 is a welding bead formed by the trailing torch 10 of the preceding welding head 11A, and 4 is the welding bead of the subsequent welding head 11B. A weld bead formed by the preceding torch 9, 5 is a weld bead formed by the trailing torch 10 of the succeeding welding head 11 </ b> B, and 6 is a welding end portion capable of crater treatment (also referred to as a crater-treated weld end portion). ), 7 is a welding end portion (also referred to as a crater untreated portion) incapable of crater treatment.

  Here, the circumferential position of the steel pipe (horizontal fixed pipe) 1 is expressed by a clock position, the highest point position is 12 o'clock position, the lowest point position is 6 o'clock position, and the middle of 12 o'clock and 6 o'clock. The position on one side of the point is the 3 o'clock position, and the position on the other side is the 9 o'clock position. Then, the welding is performed by the two welding heads 11A and 11B, respectively, from the 12 o'clock position to the 3 o'clock direction and the 12 o'clock position to the 9 o'clock direction, and welding is performed, and the bead connection is performed at the 6 o'clock position. The downward swing welding is performed. Also, a preceding welding process in which welding is performed by moving the preceding welding head downward from the 12 o'clock position through the 3 o'clock position to the 6 o'clock position, and from the 12 o'clock position through the 9 o'clock position to 6 o'clock. And the subsequent welding step in which the welding head on the subsequent side is moved downward to the position of the welding position in this order is executed with a predetermined time difference in this order.

  In the welding method of this embodiment, as shown in FIGS. 1 (a) and 1 (b), the welding head 11A on the preceding side (3 o'clock side) is moved in the direction of arrow A (clockwise) to the 6 o'clock position. When the preceding welding process is ended, the welding end position by the preceding torch 9 and the welding end position by the subsequent torch 10 are set to the same position. That is, when the welding of the leading torch 9 reaches the target welding end position, the arc of the leading torch 9 is turned off and welding of only the trailing torch 10 is continued, and the welding ending position and the trailing torch by the leading torch 9 are continued. The welding end position by 10 is set to the same position. In this case, when the welding of the leading torch 9 is finished, the trailing torch 10 is being welded, so the leading torch 9 is not subjected to crater treatment, and a dent or a crater crack occurs in the crater untreated portion 7 of the leading torch 9. However, by performing crater treatment at the time when the welding of the succeeding torch 10 is completed, it is possible to fill the dent generated in the crater untreated portion 7 of the preceding torch 9 or to remelt and remove the crater crack. .

  Further, when the subsequent welding process is finished at the 6 o'clock position by moving the subsequent side (9 o'clock side) welding head 11B in the direction of arrow B (counterclockwise), The welding end position by the trailing torch 10 is set to the same position as the welding end position of the leading torch 9 and the trailing torch 10 of the preceding welding head 11A. The “same position” described here refers to a range in which the molten metal spreads when the welding object and the torch are fixed to each other, and specifically, the center of the portion of the welding object facing the torch tip. As an area within a radius of 15 mm. When the welding point by the leading torch 9 of the succeeding side welding head 11B reaches the welding end position of the leading torch 9 of the leading side welding head 11A, the arc by the leading torch 9 is cut and welding of only the trailing torch 10 is performed. , And when the welding point of the succeeding torch 10 of the succeeding side welding head 11B reaches the welding end position of the succeeding torch 10 of the preceding side welding head 11A, the succeeding torch while performing the crater process 10 welding is completed. Thereby, welding for one round can be completed.

  Also in this case, when the welding of the preceding torch 9 of the succeeding welding head 11B is finished, the succeeding torch 10 is being welded, so the leading torch 9 is not subjected to crater processing, and the crater unprocessed portion of the leading torch 9 7 may have a dent or crack in the crater, but the crater treatment is performed at the end of the welding of the subsequent torch 10 to fill the dent generated in the crater untreated portion 7 of the preceding torch 9 or the crater crack. Can be remelted and removed. Further, in this method, since there is no single-layer bead portion 8 (see FIGS. 4 to 7) which has been a problem in the first and second study examples, a good weld bead can be obtained.

  As described above, by performing the welding sequence (welding method) of the present embodiment, the joint portion of the bead at the 6 o'clock position can be finished in a good state free of welding defects.

As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The change of the structure of the range which does not deviate from the summary of this invention, etc. are included.
For example, in the above-described embodiment, the present invention has been described by taking a dual head including two welding heads as an example. However, the present invention is not limited thereto, and only one welding head is provided, and the welding head is used for a preceding welding process. The present invention is also applicable to those used for both the welding process and the subsequent welding process.
Moreover, in the said embodiment, although the welding head is provided with the two torches of the preceding torch 9 and the succeeding torch 10, it is not restricted to this, The circumferential direction of the fixed pipe which is a welding object is not limited to this. The present invention can also be applied to an apparatus having three or more torches spaced apart from each other.

  In the above embodiment, the welding process in which welding is performed by moving the preceding welding head downward from the 12 o'clock position through the 3 o'clock position to the 6 o'clock position is referred to as the preceding welding process. The welding process in which welding is performed by moving the subsequent welding head downward to the 6 o'clock position through the 9 o'clock position is the subsequent welding process, but the preceding welding process and the subsequent welding process are reversed, that is, The welding process in which welding is performed by moving the preceding welding head downward from the 12 o'clock position to the 6 o'clock position to the 6 o'clock position is referred to as the pre-welding process, and from the 12 o'clock position to the 6 o'clock position, 6 The present invention can also be applied to a welding process in which a welding process in which welding is performed by moving the welding head on the subsequent side downward at the time position is a subsequent welding process.

1 Steel pipe (horizontal fixed pipe)
2 weld bead formed by the preceding torch of the preceding welding head 3 weld bead formed by the following torch of the preceding welding head 4 weld bead formed by the preceding torch of the succeeding welding head 5 A weld bead formed by a trailing torch of the welding head 6 Welding end part capable of crater treatment 7 Welding end part impossible of crater treatment (uncratered part)
9 Leading torch 10 Trailing torch 11A Leading side welding head 11B Trailing side welding head

Claims (3)

By moving a welding head provided with a plurality of torches spaced apart from each other in the circumferential direction along the butt end of the horizontal fixed tube, the butt end is moved by the plurality of torches. In the circumferential welding method of a fixed pipe using a consumable electrode type gas shielded arc automatic welding device for arc welding,
The position of the horizontal fixed pipe in the circumferential direction is expressed as a clock position, the highest point position is 12 o'clock position, the lowest point position is 6 o'clock position, and the middle position between 12 o'clock and 6 o'clock Is 3 o'clock and the other side is 9 o'clock,
The welding head is divided into a direction from 3 o'clock to 3 o'clock and a direction from 12 o'clock to 9 o'clock, and the welding is advanced, and the downward split welding is performed to connect the beads at the 6 o'clock position. As
A pre-welding process in which welding is performed by moving the welding head downward from the 12 o'clock position to the 6 o'clock position through the 3 o'clock or 9 o'clock position, and the 9 o'clock or 3 o'clock position from the 12 o'clock position to 6 A subsequent welding process in which welding is performed by moving the welding head downward to the hour position, in this order with a predetermined time difference,
The welding end positions of the plurality of torches in the preceding welding process are set to the same position, and the welding terminal positions of the plurality of torches in the subsequent welding process are set to the same position, thereby completing one round of welding. it can be,
The plurality of torches in the preceding welding process and the subsequent welding process each include a preceding torch and a trailing torch,
The fixed pipe circle is characterized in that the arc generated at the welding end position of the preceding torch fills the dent generated in the crater untreated part of the preceding torch by cratering at the welding termination position of the subsequent torch. Circumferential welding method. The circumferential welding of a fixed pipe according to claim 1 , wherein two welding heads are provided, one of which is used for a preceding welding process and the other is used for a subsequent welding process. Method. Welding having a carriage moving on a traveling rail arranged in the circumferential direction along the butt end of the horizontal fixed pipe, and a plurality of torches arranged on the carriage apart from each other in the welding direction along the circumference In a consumable electrode type gas shielded arc automatic welding apparatus comprising a head and arc welding the butt end by the plurality of torches while moving a carriage of the welding head in a circumferential direction along a traveling rail,
It has two welding heads and a welding control means for controlling the operation of these two welding heads.
The welding control means,
The position of the horizontal fixed pipe in the circumferential direction is expressed as a clock position, the highest point position is 12 o'clock position, the lowest point position is 6 o'clock position, and the middle position between 12 o'clock and 6 o'clock Is 3 o'clock and the other side is 9 o'clock,
The two welding heads distribute the welding from the 12 o'clock position to the 3 o'clock direction and the 12 o'clock position to the 9 o'clock direction, respectively, and proceed with welding, and the bead is connected at the 6 o'clock position. As performing minute welding,
A pre-welding process in which welding is performed by moving the preceding welding head downward from the 12 o'clock position to the 6 o'clock position through the 3 o'clock or 9 o'clock position, and the 9 o'clock or 3 o'clock position from the 12 o'clock position And a subsequent welding step of performing welding by moving the subsequent welding head downward to the 6 o'clock position in this order with a predetermined time difference,
The welding end positions of the plurality of torches in the preceding welding process are set to the same position, and the welding terminal positions of the plurality of torches in the subsequent welding process are set to the same position, thereby completing one round of welding. and to perform the control of,
The plurality of torches in the preceding welding process and the subsequent welding process are each provided with a preceding torch and a trailing torch in the cart,
Consumable electrode type characterized in that the arc generated at the welding end position of the preceding torch fills the dent generated in the crater untreated portion of the preceding torch by cratering at the welding end position of the subsequent torch. Gas shield arc automatic welding equipment.

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