Submerged arc welding system

Abstract

To provide a submerged arc welding system that can reduce loads on an operator and properly execute running start.SOLUTION: A welding system A1 is provided with: an electrode 8a that generates arc on an object W to be welded to perform welding; an electrode 8b that arrives at a welded portion to be welded, following the electrode 8a and generates arc to perform welding; a carrier 4 loaded with the electrode 8a and the electrode 8b, which runs along a welding wire; and a control device 1 that controls the carrier 4. The control device 1 is provided with: a speed setting part 12 that sets running speed of the carrier 4; a distance setting part 11 that sets a separation distance between a tip of the electrode 8a and a tip of the electrode 8b; and a time calculating part 13 that calculates a delay time T1 on the basis of the running speed and the separation distance, which when starting welding, makes the electrode 8a start generating arc, makes the carrier 4 start running and then makes the electrode 8b start generating arc, after the delay time T1 has elapsed after the carriage 4 started running.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a submerged arc welding system for performing submerged arc welding. [Background technology]

[0002] Submerged arc welding has been known in the past. In submerged arc welding, granular flux is dispersed on the workpiece, a welding wire is fed into the flux, and an arc is generated between the tip of the welding wire (electrode) and the workpiece to perform welding. In submerged arc welding, welding is performed while moving the welding point, for example, by running a carriage along the welding line. In submerged arc welding, a large current is passed through a large-diameter welding wire, allowing thick plates to be welded with high efficiency. Also known is a submerged arc welding method in which multiple electrodes are used to generate an arc at each electrode. Patent Document 1 discloses a submerged arc welding method using multiple electrodes.

[0003] In submerged arc welding using multiple electrodes, a so-called running start is known at the start of welding. In a running start, the leading electrode first starts generating an arc, and immediately thereafter, the carriage carrying each electrode starts moving. The trailing electrode then starts generating an arc when it reaches the molten pool formed on the workpiece by the arc of the leading electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-309471 Summary of the Invention [Problem to be solved by the invention]

[0005] In the running start method, the operator visually confirms that the trailing electrode has reached the weld pool and initiates arc generation at the trailing electrode. In this case, the quality of the bead deteriorates if the timing of the arc generation at the trailing electrode is not properly synchronized, so the operator must be highly skilled. To enable even less skilled operators to properly perform a running start, one method involves presetting a delay time to offset the timing of the arc generation between the leading electrode and the trailing electrode. However, determining the appropriate delay time requires multiple actual welding trials, which is time-consuming and burdensome for the operator. Furthermore, changing the travel speed of the cart also changes the appropriate delay time, so the delay time must be re-determined.

[0006] The present invention has been devised in light of the above circumstances, and an object of the present invention is to provide a submerged arc welding system that reduces the burden on the operator and allows a running start to be performed appropriately. [Means for solving the problem]

[0007] The submerged arc welding system provided by the present invention is a submerged arc welding system for performing submerged arc welding, comprising: a first electrode that generates an arc on a workpiece to perform welding; a second electrode that arrives at a welding point on the workpiece later than the first electrode and generates an arc to perform welding; a carriage that carries the first electrode and the second electrode and travels along a weld line; and a control device that controls the carriage, wherein the control device comprises: a speed setting unit that sets the traveling speed of the carriage; a distance setting unit that sets the separation distance between the tip of the first electrode and the tip of the second electrode; and a time calculation unit that calculates a delay time based on the traveling speed and the separation distance, and when welding starts, starts generating an arc at the first electrode and starts traveling the carriage, and starts generating an arc at the second electrode after the delay time has elapsed since the carriage started traveling.

[0008] In a preferred embodiment of the present invention, the time calculation unit calculates the delay time by dividing the separation distance by the traveling speed.

[0009] In a preferred embodiment of the present invention, the vehicle further comprises an acceleration setting unit that sets an acceleration of the carriage, and the time calculation unit also uses the acceleration to calculate the delay time.

[0010] In a preferred embodiment of the present invention, the vehicle further includes a third electrode that arrives at the welding point later than the second electrode and generates an arc to perform welding, the distance setting unit further sets a second separation distance between the tip of the first electrode and the tip of the third electrode, the time calculation unit calculates a second delay time based on the traveling speed and the second separation distance, and the control device starts generating an arc at the third electrode after the second delay time has elapsed since the bogie started traveling.

[0011] In a preferred embodiment of the present invention, the carriage further includes a spraying device mounted on the carriage for spraying flux, wherein the distance setting unit further sets a first distance between the welding start point and a flux spraying port of the spraying device in the direction of travel of the carriage, the time calculation unit further calculates a first time based on the traveling speed and the first distance, and the control device causes the spraying device to start spraying the flux when the first time has elapsed since the carriage started traveling, and causes the control device to start generating an arc at the second electrode when the delay time has elapsed since the arc was generated at the first electrode.

[0012] In a preferred embodiment of the present invention, the system further includes a recovery device that moves together with the carriage and recovers the flux, wherein the distance setting unit further sets a second distance between the second electrode and a flux recovery port of the recovery device in the traveling direction of the carriage, the time calculation unit further calculates a second time based on the traveling speed and the second distance, and the control device causes the recovery device to start recovering the flux when the second time has elapsed since the arc occurred at the second electrode. [Effects of the Invention]

[0013] According to the present invention, the time calculation unit calculates the delay time based on the distance between the tip of the first electrode and the tip of the second electrode and the traveling speed of the carriage. Because the delay time is calculated automatically, the worker does not need to repeatedly try the welding work to determine the delay time, reducing the burden on the worker. Furthermore, the control device starts the generation of an arc at the second electrode after the delay time has elapsed since the carriage started traveling. As a result, the second electrode starts the generation of an arc when it reaches the position where the first electrode started the generation of the arc. Therefore, the submerged arc welding system according to the present invention can properly perform a running start. [Brief explanation of the drawings]

[0014] [Figure 1] 1A and 1B are diagrams for explaining a welding system according to a first embodiment, in which FIG. 1A is a block diagram showing the overall configuration of the welding system, and FIG. 1B is a block diagram showing the internal configuration of a control device and a plurality of welding power sources. [Figure 2] 10 is an example of a flowchart showing a welding start process performed by a control device. [Figure 3] 4 is a timing chart showing each state in the welding start process. [Figure 4] FIG. 4 is a block diagram showing an internal configuration of a modified example of the control device of the welding system according to the first embodiment. [Figure 5] 10A and 10B are diagrams for explaining a welding system according to a second embodiment, in which FIG. 10A is a block diagram showing the overall configuration of the welding system, and FIG. 10B is a block diagram showing the internal configuration of a control device and a plurality of welding power sources. [Figure 6] 10A and 10B are diagrams for explaining a welding system according to a third embodiment, in which (a) is a schematic diagram of a carriage of the welding system, and (b) is a block diagram showing the internal configuration of a control device. [Figure 7] 10 is an example of a flowchart showing a welding start process according to a third embodiment. [Figure 8]10 is a timing chart showing each state in a welding start process according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0016] [First embodiment] FIG. 1 is a diagram illustrating a welding system A1 according to a first embodiment. FIG. 1(a) is a block diagram showing the overall configuration of the welding system A1. FIG. 1(b) is a block diagram showing the internal configuration of a control device and multiple welding power supplies. Note that in FIG. 1(b), the internal configuration of one of the welding power supplies is omitted.

[0017] Welding system A1 is a welding system for performing submerged arc welding. As shown in FIG. 1(a), welding system A1 includes a control device 1, a carriage 4, a sprayer 7, and a plurality of welding power supplies 2, welding torches 3, wire feeders 5, wire reels 6, and electrodes 8. While traveling along a weld line of workpieces W, welding system A1 causes the sprayer 7 mounted on carriage 4 to spray granular flux 79 and the wire feeder 5 to feed welding wire into the flux 79. The welding wire is supplied from wire reel 6. Welding power supply 2 converts AC power supplied from commercial power source P into power suitable for welding and outputs it. An arc is generated within the flux 79 between electrode 8, which is the tip of the welding wire, and workpieces W. Heat from the arc causes welding. This results in welding along the weld line of workpieces W.

[0018] Welding torch 3 guides the welding wire fed by wire feeder 5 to the welding point. The tip of the welding wire becomes electrode 8, which protrudes from the tip of welding torch 3. Welding torch 3 has a contact tip (not shown) located at the tip and connected to welding power supply 2. Welding power supply 2 applies a welding current to the welding wire that contacts the contact tip. Welding torch 3 is mounted on carriage 4 and moves as carriage 4 moves. Therefore, electrode 8 is also mounted on carriage 4 and moves as carriage 4 moves. Welding torch 3 may be fixed directly to carriage 4 or indirectly via an arm or the like.

[0019] In this embodiment, welding system A1 includes two welding power supplies 2, welding torches 3, wire feeders 5, wire reels 6, and electrodes 8. Welding system A1 performs so-called tandem welding, in which two electrodes 8 pass the same welding location at different times and each electrode 8 generates an arc, enabling highly efficient, high-speed welding. Two welding torches 3 are arranged side by side in the traveling direction of carriage 4. Therefore, as carriage 4 travels along the weld line of workpieces W, one electrode 8 passes a welding location, and then the other electrode 8 passes the welding location later than the first electrode 8. Hereinafter, the leading electrode 8 that passes the welding location first may be referred to as electrode 8a, and the trailing electrode 8 that passes the welding location later than electrode 8a may be referred to as electrode 8b. Additionally, welding torch 3 that guides welding wire to be electrode 8a may be referred to as welding torch 3a, and welding power supply 2 that supplies power to electrode 8a may be referred to as welding power supply 2a. Additionally, welding torch 3 that guides welding wire to be electrode 8b may be referred to as welding torch 3b, and welding power supply 2 that supplies power to electrode 8b may be referred to as welding power supply 2b.

[0020] Welding power supply 2 converts AC power supplied from commercial power supply P into power suitable for welding and supplies it to welding torch 3 (electrode 8). In this embodiment, as shown in FIG. 1(a), welding power supply 2a supplies power to welding torch 3a (electrode 8a), and welding power supply 2b supplies power to welding torch 3b (electrode 8b). As shown in FIG. 1(b), welding power supply 2 includes rectifying and smoothing circuit 21, inverter circuit 22, transformer 23, rectifying and smoothing circuit 24, inverter circuit 25, current sensor 26, voltage sensor 27, communication unit 29, and control circuit 28.

[0021] The rectifying and smoothing circuit 21 converts AC power input from the commercial power source P into DC power and outputs it. The inverter circuit 22 converts the DC power input from the rectifying and smoothing circuit 21 into high-frequency power and outputs it by switching the switching elements in response to an output control drive signal input from the control circuit 28. The transformer 23 transforms the high-frequency voltage output by the inverter circuit 22 and outputs it to the rectifying and smoothing circuit 24. The rectifying and smoothing circuit 24 converts the high-frequency power input from the transformer 23 into DC power and outputs it.

[0022] Inverter circuit 25 converts the DC power input from rectifying and smoothing circuit 24 into AC power and outputs it by switching the switching elements in response to a switching drive signal input from control circuit 28. Inverter circuit 25 switches between positive polarity, in which the potential of output terminal a (connected to workpiece W) is higher than the potential of output terminal b (connected to the contact tip of welding torch 3), and reverse polarity, in which the potential of output terminal a is lower than the potential of output terminal b. Note that welding power supply 2 may be a DC-only power supply that does not include inverter circuit 25.

[0023] Current sensor 26 detects the output current of welding power supply 2, and in this embodiment is disposed on a connection line connecting one output terminal of inverter circuit 25 with output terminal a. The output current of welding power supply 2 detected by current sensor 26 is substantially equal to the current flowing through electrode 8. There are no limitations on the location where current sensor 26 is disposed. Current sensor 26 detects a current detection signal (analog signal) corresponding to the output current of welding power supply 2, and outputs the signal to control circuit 28.

[0024] Voltage sensor 27 detects the output voltage of welding power supply 2, and in this embodiment, detects the voltage between output terminal a and output terminal b. This voltage is approximately equal to the voltage applied between workpiece W and the tip of electrode 8. Voltage sensor 27 detects a voltage detection signal (analog signal) corresponding to the output voltage of welding power supply 2 and outputs it to control circuit 28. Note that voltage sensor 27 may also detect the voltage between a lead wire conductively connected to the contact tip of welding torch 3 and a lead wire conductively connected to workpiece W.

[0025] The communication unit 29 communicates with a communication unit 16 (described later) of the control device 1 via a communication line 9. The communication unit 16 and the communication unit 29 perform digital communication, and in this embodiment, the communication is performed in accordance with the CAN (Controller Area Network) communication standard. The communication standard between the communication unit 16 and the communication unit 29 is not limited, and may be, for example, field bus communication or Ethernet communication. The communication unit 16 and the communication unit 29 may perform analog communication. The communication between the communication unit 16 and the communication unit 29 may be wireless communication that does not use the communication line 9. The communication unit 29 receives a power output start command and an output stop command from the control device 1 (communication unit 16) and inputs them to the control circuit 28. The information that the communication unit 29 receives from the control device 1 (communication unit 16) is not limited. The communication unit 29 transmits the output current value and the output voltage value detected by the control circuit 28 to the control device 1 (communication unit 16), as described later. The information that the communication unit 29 transmits to the control device 1 (communication unit 16) is not limited.

[0026] Control circuit 28 is a circuit for controlling welding power supply 2 and is realized by, for example, a microcomputer. Control circuit 28 controls the driving and stopping of inverter circuits 22, 25 based on an output start command and an output stop command received from control device 1 (communication unit 16) via communication unit 29. Specifically, control circuit 28 starts outputting a driving signal to inverter circuits 22, 25 when it receives an output start command, and stops outputting the driving signal when it receives an output stop command.

[0027] Control circuit 28 detects the output current value, which is a digital signal, based on the current detection signal input from current sensor 26. The output current value is the instantaneous value of the output current obtained by converting the current detection signal (analog signal) into a digital signal. The output current value may be the absolute value of the instantaneous value of the output current, or may be the effective value or average value. Control circuit 28 also detects the output voltage value, which is a digital signal, based on the voltage detection signal input from voltage sensor 27. The output voltage value is the instantaneous value of the output voltage obtained by converting the voltage detection signal (analog signal) into a digital signal. The output voltage value may be the absolute value of the instantaneous value of the output voltage, or may be the effective value or average value. Control circuit 28 transmits the detected output current value and output voltage value to control device 1 via communication unit 29.

[0028] Control circuit 28 generates an output control drive signal to be output to inverter circuit 22 and a switching drive signal to be output to inverter circuit 25 according to the detected output current value, output voltage value, various setting values, etc. The configuration of welding power supply 2 is not limited.

[0029] The control device 1 performs various controls of the welding system A1. The control device 1 includes a control board equipped with a microcomputer, a communication module, etc., an operation panel for operation, and a display panel for display. The control device 1 may be mounted on the carriage 4 or may be located separately from the carriage 4 (for example, adjacent to the welding power supply 2). The control device 1 may also be a general-purpose computer having installed thereon a program for performing various controls of the welding system A1. The control device 1 causes the carriage 4 to travel at a predetermined traveling speed. The traveling speed is set depending on the material and thickness of the workpiece W. The control device 1 instructs the spraying device 7 to start and stop spraying the flux 79. Note that the spraying of the flux 79 by the spraying device 7 may be started and stopped manually. The control device 1 instructs each wire feeder 5 to start and stop feeding the welding wire and to set the welding wire feeding speed. The feeding speed is set depending on the set welding current, etc.

[0030] Control device 1 also communicates with and controls each welding power supply 2. Control device 1 commands each welding power supply 2 to start and stop power output. As shown in FIG. 1(b), control device 1 includes distance setting unit 11, speed setting unit 12, time calculation unit 13, carriage control unit 14, welding command unit 15, and communication unit 16. Note that control device 1 also includes other components, but these are not shown in FIG. 1 and will not be described in detail.

[0031] Communication unit 16 communicates with communication unit 29 of each welding power supply 2 via communication line 9. Communication unit 16 transmits a command to start and stop power output to each welding power supply 2 (communication unit 29). The information that communication unit 16 transmits to each welding power supply 2 (communication unit 29) is not limited. Communication unit 16 receives output current values, output voltage values, etc. from each welding power supply 2 (communication unit 29). The information that communication unit 16 receives from each welding power supply 2 (communication unit 29) is not limited.

[0032] Distance setting unit 11 sets the separation distance between the tip of electrode 8a and the tip of electrode 8b. The separation distance is set in advance in distance setting unit 11. If the mounting positions of welding torches 3a and 3b can be changed, an operator may set the actually measured separation distance in distance setting unit 11 by operating an operation panel. Alternatively, distance setting unit 11 may automatically set the separation distance based on the mounting positions of welding torches 3a and 3b. Distance setting unit 11 outputs the separation distance to time calculation unit 13.

[0033] The speed setting unit 12 sets the traveling speed of the carriage 4. The traveling speed is preset in the speed setting unit 12 by an operator operating an operation panel. The speed setting unit 12 may also automatically set the traveling speed based on the material and thickness of the workpieces W. The speed setting unit 12 outputs the traveling speed to the carriage control unit 14 and the time calculation unit 13.

[0034] Time calculation unit 13 calculates a delay time, which is the time from when carriage 4 starts traveling until electrode 8b reaches the position where electrode 8a starts generating an arc. Time calculation unit 13 calculates the delay time by dividing the separation distance input from distance setting unit 11 by the traveling speed input from speed setting unit 12. Time calculation unit 13 outputs the delay time to welding command unit 15.

[0035] The bogie control unit 14 controls the traveling of the bogie 4. The bogie control unit 14 controls the start and stop of traveling of the bogie 4. The bogie control unit 14 also causes the bogie 4 to travel at the traveling speed input from the speed setting unit 12. The bogie control unit 14 causes the bogie 4 to start traveling by issuing a traveling start command and a traveling speed command to the bogie 4. The bogie control unit 14 also stops the traveling of the bogie 4 by outputting a traveling stop command to the bogie 4. The bogie 4 travels at the commanded traveling speed by driving a motor (not shown) at a rotation speed corresponding to the commanded traveling speed. Note that the method of causing the bogie 4 to travel at the traveling speed is not limited. For example, the bogie control unit 14 may feedback control the traveling speed of the bogie 4.

[0036] Welding command unit 15 issues a command to start generating an arc between electrodes 8a and 8b. When starting welding, welding command unit 15 first starts generating an arc at electrode 8a. Specifically, welding command unit 15 sends an output start command to welding power supply 2a via communication unit 16. Upon receiving the output start command, welding power supply 2a starts outputting power and generates an arc between electrode 8a and workpiece W. The method of generating an arc is not limited. For example, welding power supply 2a may generate an arc between the tip of electrode 8 and workpiece W by applying a high DC current as a start current while electrode 8a is short-circuited to workpiece W, causing electrode 8 to burn. Alternatively, welding command unit 15 may generate an arc by causing wire feeder 5 to feed the welding wire that will become electrode 8a and then retracting it after the short circuit. After an arc is generated at electrode 8a, welding command unit 15 starts generating an arc at electrode 8b after a delay time has elapsed since carriage 4 started traveling. Specifically, welding command unit 15 transmits a command to start outputting power to welding power supply 2b via communication unit 16. Upon receiving the command to start outputting power, welding power supply 2b starts outputting power and generates an arc between electrode 8b and workpiece W. The method for generating the arc is not limited.

[0037] Next, the welding start process performed by the control device 1 will be described.

[0038] 2 is an example of a flowchart showing the welding start process performed by the control device 1. The welding start process is started, for example, when an operation button for starting welding is pressed.

[0039] First, the separation distance is acquired (S1), the traveling speed is acquired (S2), and the delay time T1 is calculated (S3). Specifically, the time calculation unit 13 calculates the delay time T1 by dividing the separation distance acquired from the distance setting unit 11 by the traveling speed acquired from the speed setting unit 12.

[0040] Next, flux 79 is sprayed on the welding start point of the workpieces W and the surrounding area (S4). Specifically, control device 1 commands sprayer 7 to start spraying flux 79. Sprayer 7 sprays a preset appropriate amount of flux 79. Next, an arc is started at leading electrode 8a (S5). Specifically, welding command unit 15 sends an output start command to welding power supply 2a, causing welding power supply 2a to start outputting power, and an arc is generated between electrode 8a and workpieces W. After the arc is generated at electrode 8a, carriage 4 starts traveling (S6). Specifically, carriage control unit 14 commands carriage 4 to start traveling and to specify the traveling speed.

[0041] Next, timing of the time from when the carriage 4 started traveling is started (S7), and it is determined whether the time T is equal to or greater than the delay time T1 (S8). If the time T is less than the delay time T1 (S8: NO), the process returns to step S8 and the determination is repeated. If the time T is equal to or greater than the delay time T1 (S8: YES), an arc is generated at the trailing electrode 8b (S9), and the welding start process is terminated. Specifically, welding command unit 15 sends an output start command to welding power supply 2b, causing welding power supply 2b to start outputting power and generate an arc between electrode 8b and workpiece W. When the time T from when the carriage 4 started traveling reaches delay time T1, carriage 4 has moved the distance between the tip of electrode 8a and the tip of electrode 8b. By starting the arc at electrode 8b at this timing, electrode 8b can start generating an arc at the position where electrode 8a started generating an arc.

[0042] The process shown in the flowchart of FIG. 2 is an example, and the welding start process performed by the control device 1 is not limited to the above.

[0043] FIG. 3 is a timing chart showing each state during the welding start process. (a) shows the time change in the dispersion state of the flux 79. The ON signal is ON when the flux 79 is being dispersed. (b) shows the time change in the actual traveling speed of the carriage 4. (c) shows the time change in the arc state of the leading electrode 8a. The ON signal is ON when an arc is generated. (d) shows the time change in the measured time T from the start of traveling of the carriage 4. (e) shows the time change in the arc state of the trailing electrode 8b. The ON signal is ON when an arc is generated. Note that the vertical and horizontal axes of the timing chart shown in FIG. 3 have been appropriately enlarged or reduced for ease of understanding, and the waveforms shown have been simplified, exaggerated, or emphasized for ease of understanding. This also applies to FIG. 8, which will be described later.

[0044] At time t1, the operation button for starting welding is pressed, thereby starting the welding start process. At this time, the dispersion of flux 79 begins, arc generation begins at the leading electrode 8a, and the carriage 4 starts traveling. Thereafter, the measured time T increases according to the elapsed time. Then, at time t2, the measured time T reaches the delay time T1, thereby starting arc generation at the trailing electrode 8b. The integral value of the actual traveling speed of the carriage 4 (the area of ​​the hatched portion in FIG. 3(b)) corresponds to the traveling distance of the carriage 4. The traveling distance at time t2 approximately matches the distance between the tip of electrode 8a and the tip of electrode 8b.

[0045] Next, the operation and effects of the welding system A1 according to this embodiment will be described.

[0046] In this embodiment, time calculation unit 13 calculates delay time T1 by dividing the separation distance acquired from distance setting unit 11 by the traveling speed acquired from speed setting unit 12. Because delay time T1 is automatically calculated, the operator does not need to repeatedly try the welding work to determine delay time T1, thereby reducing the burden on the operator. Furthermore, after starting the generation of an arc at electrode 8a, welding command unit 15 starts the generation of an arc at electrode 8b after delay time T1 has elapsed since the carriage 4 started traveling. As a result, electrode 8b starts the generation of an arc when electrode 8a reaches the position where the arc started to be generated by electrode 8a. Therefore, welding system A1 can properly perform a running start.

[0047] Furthermore, according to this embodiment, when the traveling speed of the carriage 4 is changed, the time calculation unit 13 calculates the delay time T1 using the changed traveling speed set in the speed setting unit 12. Therefore, the welding system A1 can automatically respond to the change in the traveling speed of the carriage 4.

[0048] Furthermore, according to this embodiment, the time calculation unit 13 calculates the delay time T1 by dividing the separation distance by the traveling speed, which reduces the calculation processing load on the control device 1 compared to when the delay time T1 is calculated using complex calculations.

[0049] Furthermore, when communication unit 16 and communication unit 29 perform digital communication via communication line 9, welding system A1 can suppress communication failures caused by noise even in a noisy welding site.

[0050] In this embodiment, the case where welding power supply 2 controls output using inverter circuit 22 has been described, but this is not limiting. Welding power supply 2 may also be configured to control output using a configuration other than an inverter circuit, such as a thyristor-controlled power supply or a moving-iron-core power supply.

[0051] In the present embodiment, welding system A1 has been described as a case in which wire feeder 5 feeds a welding wire and the tip portion of the welding wire protruding from the tip of welding torch 3 serves as electrode 8, but this is not limited to this. Welding system A1 may use an electrode made of non-melting material such as tungsten as electrode 8.

[0052] [Modification] FIG. 4 is a block diagram showing the internal configuration of a modified control device 1 of the welding system A1 according to the first embodiment. As shown in FIG. 3(b), the actual traveling speed of the carriage 4 does not immediately reach the traveling speed set by the speed setting unit 12 after starting traveling. Instead, it increases from "0" to the set traveling speed over a very short acceleration time. The control device 1 according to the modified embodiment calculates the delay time T1 taking into account the speed change during the acceleration time. In this modified embodiment, the control device 1 further includes an acceleration setting unit 17. The acceleration setting unit 17 sets the acceleration of the carriage 4 at the start of traveling. The time calculation unit 13 according to this modified embodiment calculates the delay time T1 using the acceleration input from the acceleration setting unit 17. Specifically, the time calculation unit 13 calculates the delay time T1 based on the following equation (1), where L is the separation distance input from the distance setting unit 11, v is the traveling speed input from the speed setting unit 12, and a is the acceleration input from the acceleration setting unit 17. According to this modification, the start position of arc generation at electrode 8b more precisely coincides with the start position of arc generation at electrode 8a, so that a running start can be more appropriately performed. T1=(v / 2a)+(L / v) (1)

[0053] Second Embodiment FIG. 5 is a diagram illustrating a welding system A2 according to a second embodiment. FIG. 5(a) is a block diagram showing the overall configuration of the welding system A2. FIG. 5(b) is a block diagram showing the internal configuration of the control device 1 and multiple welding power supplies 2. Note that FIG. 5(b) omits the internal configuration of each welding power supply 2. In FIG. 5, elements that are the same as or similar to those in the first embodiment are assigned the same reference numerals as those in the first embodiment. The welding system A2 according to this embodiment differs from the welding system A1 according to the first embodiment in that it includes three electrodes 8.

[0054] In this embodiment, welding system A2 includes three welding power supplies 2, welding torches 3, wire feeders 5, wire reels 6, and electrodes 8. Hereinafter, the welding power supplies 2, welding torches 3, and electrodes 8 added to welding system A1 may be referred to as welding power supplies 2c, welding torches 3c, and electrodes 8c, respectively. Welding torch 3c is positioned alongside welding torches 3a and 3b, on the opposite side of welding torch 3b from welding torch 3a in the traveling direction of carriage 4. Welding torch 3c guides the welding wire that becomes electrode 8c. Therefore, due to the traveling of carriage 4, electrode 8c passes the welding point later than electrode 8b. Welding power supply 2c supplies power to electrode 8c. Communication unit 29 of welding power supply 2c communicates with communication unit 16 of control device 1 via communication line 9.

[0055] Furthermore, in control device 1 according to this embodiment, distance setting unit 11 further sets a second separation distance between the tip of electrode 8a and the tip of electrode 8c, and time calculation unit 13 calculates a second delay time based on the traveling speed and the second separation distance. Welding command unit 15 starts generating an arc at electrode 8c after the second delay time has elapsed since carriage 4 started traveling.

[0056] In this embodiment, time calculation unit 13 also calculates delay time T1 by dividing the separation distance acquired from distance setting unit 11 by the traveling speed acquired from speed setting unit 12. Because delay time T1 is automatically calculated, the burden on the worker is reduced. Furthermore, welding command unit 15 starts generating an arc at electrode 8b after delay time T1 has elapsed since carriage 4 started traveling. As a result, electrode 8b starts generating an arc when it reaches the position where electrode 8a started generating the arc. Therefore, welding system A2 can properly perform a running start.

[0057] Furthermore, according to this embodiment, time calculation unit 13 calculates a second delay time based on the traveling speed and the second separation distance acquired from distance setting unit 11. Furthermore, welding command unit 15 starts generating an arc at electrode 8c after the second delay time has elapsed since carriage 4 started traveling. This causes electrode 8c to start generating an arc when electrode 8a reaches the position where electrode 8a started generating the arc. Therefore, welding system A2 can appropriately perform a running start for the three electrodes 8. Furthermore, welding system A2 according to this embodiment has a configuration in common with welding system A1, and thus achieves the same effects as welding system A1.

[0058] In this embodiment, the control device 1 uses the second delay time calculated based on the second separation distance between the tip of electrode 8a and the tip of electrode 8c, but this is not limiting. For example, the control device 1 may use a third delay time calculated based on a third separation distance between the tip of electrode 8b and the tip of electrode 8c. In this case, the control device 1 may start the generation of an arc at electrode 8c after the third delay time has elapsed since the start of the generation of an arc at electrode 8b.

[0059] In the first embodiment, a case where two electrodes 8 are provided has been described, and in the second embodiment, a case where three electrodes 8 are provided has been described. As can be understood from these descriptions, the submerged arc welding system according to the present invention may be provided with four or more electrodes 8. Even in this case, a running start can be properly performed by starting the generation of an arc at each electrode 8 according to each delay time calculated from each separation distance.

[0060] Third Embodiment 6 to 8 are diagrams for explaining a welding system A3 according to a third embodiment. FIG. 6(a) is a schematic diagram of a carriage 4 of the welding system A3. FIG. 6(b) is a block diagram showing the internal configuration of the control device 1. In FIG. 6, elements that are the same as or similar to those of the first embodiment are given the same reference numerals as those of the first embodiment. Note that a block diagram showing the overall configuration of the welding system A3 is omitted because it is substantially the same as that of the welding system A1 (see FIG. 1(a)). FIG. 7 is an example of a flowchart showing the welding start process performed by the control device 1. FIG. 8 is a timing chart showing each state in the welding start process. The welding system A3 according to this embodiment differs from the welding system A1 according to the first embodiment in the welding start process.

[0061] The welding system A3 according to this embodiment further includes a recovery device 75. The recovery device 75 moves together with the carriage 4 and recovers by sucking unmelted flux remaining on the solidified slag among the flux scattered during welding. The recovery device 75 may be mounted on the carriage 4 or may be towed by the carriage 4. The recovery device 75 may also be configured to return the recovered flux directly to the hopper of the scattering device 7.

[0062] In this embodiment, as shown in FIG. 6( a), the carriage 4 starts moving from a position away from the welding start point S. The control device 1 causes the sprayer 7 to start spraying flux 79 when the flux spray port of the sprayer 7 reaches the welding start point S. The control device 1 also causes the electrode 8a to start generating an arc when the electrode 8a reaches the welding start point S, and causes the electrode 8b to start generating an arc when the electrode 8b reaches the welding start point S. The control device 1 also causes the recovery device 75 to start collecting the flux 79 when the flux collection port of the collection device 75 reaches the welding start point S.

[0063] In the control device 1 according to this embodiment, the distance setting unit 11 sets the distance L1 between the welding start point S and the flux spraying port of the spraying device 7, the distance L2 between the flux spraying port and the electrode 8a, the distance L3 between the electrodes 8a and 8b, and the distance L4 between the electrode 8b and the flux recovery port of the recovery device 75 in the traveling direction of the carriage 4. The distance L3 corresponds to the separation distance according to the first embodiment. The time calculation unit 13 calculates the time T L1 ~T L4 The time calculation unit 13 calculates the time T by dividing the distance L1 input from the distance setting unit 11 by the traveling speed input from the speed setting unit 12. L1 Similarly, the time calculation unit 13 calculates the time T by dividing the distance L2 by the traveling speed. L2 The distance L3 is calculated by dividing it by the running speed to obtain the time T L3 The distance L4 is calculated by dividing it by the running speed to obtain the time T L4 Calculate the time T L3 corresponds to the delay time T1 in the first embodiment. L2 and time T L3 to the welding command unit 15. The time calculation unit 13 also outputs the time T L1 and time T L4 is output to the flux control unit 18, which will be described later.

[0064] The control device 1 according to this embodiment further includes a flux control unit 18. The flux control unit 18 controls the spraying device 7 and the recovery device 75. The flux control unit 18 controls the start and stop of the spraying of flux by the spraying device 7, and the start and stop of the recovery of flux by the recovery device 75. In this embodiment, the flux control unit 18 controls the start and stop of the recovery of flux by the recovery device 75 from the time T L1 After the time T has elapsed since the welding command unit 15 started generating an arc at the electrode 8b, the flux control unit 18 controls the flux spraying device 7 to start spraying the flux. L4 In this embodiment, the welding command unit 15 causes the recovery device 75 to start recovering the flux when the time T L2 The welding command unit 15 starts generating an arc at the electrode 8a when the time T L3 When this time has elapsed, an arc is initiated at electrode 8b.

[0065] As shown in the flowchart of FIG. 7, in the welding start process according to the third embodiment, first, the distances L1 to L4 are acquired (S11), the traveling speed is acquired (S12), and the time T L1 ~T L4 is calculated (S13). Next, the carriage 4 starts traveling (S14). Next, measurement of the time from the start of traveling of the carriage 4 starts (S15), and the measured time T is calculated as time T L1 It is determined whether the measured time T is equal to or greater than the time T (S16). L1 If the count time T is less than the time T (S16: NO), the process returns to step S16 and the determination is repeated. L1 If the above is true (S16: YES), the dispersion of flux is started (S17).

[0066] Next, the time measurement from the start of flux spraying is started (S18), and the measured time T is time T L2 It is determined whether the measured time T is equal to or greater than the time T (S19). L2If the count time T is less than the time T (S19: NO), the process returns to step S19 and the determination is repeated. L2 In the above case (S19: YES), arc generation starts at the leading electrode 8a (S20).

[0067] Next, timing of the time from the start of arc generation at the electrode 8a is started (S21), and the time T is reached. L3 It is determined whether the measured time T is equal to or greater than the time T (S22). L3 If the count time T is less than the time T (S22: NO), the process returns to step S22 and the determination is repeated. L3 In the above case (S22: YES), arc generation is started at the trailing electrode 8b (S23).

[0068] Next, timing of the time from the start of arc generation at electrode 8b is started (S24), and the time T is measured. L4 It is determined whether the measured time T is equal to or greater than the time T (S25). L4 If the count time T is less than the time T (S25: NO), the process returns to step S25 and the determination is repeated. L4 In the above case (S25: YES), collection of flux is started (S26), and the welding start process is ended. Note that the process shown in the flowchart of Fig. 7 is an example, and the welding start process performed by the control device 1 is not limited to the above.

[0069] In the timing chart shown in Fig. 8, similar to the timing chart shown in Fig. 3, (a) shows the change over time in the spray state of flux 79, and (b) shows the change over time in the actual traveling speed of the carriage 4. Also, (c) shows the change over time in the arc state of the leading electrode 8a, (d) shows the change over time in the measured time T, and (e) shows the change over time in the arc state of the trailing electrode 8b. Fig. 8(f) shows the change over time in the recovery state of flux 79, and is ON when recovery of flux 79 is being performed.

[0070] At time t11, the operation button for starting welding is pressed, and the welding start process is started. At this time, the carriage 4 starts traveling. After that, the measured time T increases according to the elapsed time. Then, at time t12, the measured time T reaches time T L1 The dispersion of flux 79 begins. After that, the measured time T returns to "0" and increases according to the elapsed time. At time t13, the time T L2 , arc generation begins at the leading electrode 8a. After that, the counted time T returns to "0" and increases according to the elapsed time. At time t14, the counted time T L3 As a result, arc generation begins at the trailing electrode 8b. After that, the counted time T returns to "0" and increases according to the elapsed time. At time t15, the counted time T L4 As a result, the spraying of Flux 79 has begun.

[0071] According to this embodiment, the time calculation unit 13 divides the distance L3 (corresponding to the separation distance) acquired from the distance setting unit 11 by the traveling speed acquired from the speed setting unit 12, thereby calculating the time T L3 (corresponding to delay time T1) is calculated. L3 Since the welding command unit 15 automatically calculates the time T L3 When the time has elapsed, electrode 8b starts generating an arc. As a result, electrode 8b starts generating an arc when electrode 8a reaches the position where electrode 8a started generating the arc. Therefore, welding system A3 can appropriately perform a running start. Furthermore, welding system A3 according to this embodiment has a configuration in common with welding system A1, and thereby achieves the same effects as welding system A1.

[0072] Furthermore, according to this embodiment, the time calculation unit 13 calculates the time T based on the running speed and the distance L1 acquired from the distance setting unit 11. L1 Furthermore, the flux control unit 18 calculates the time T L1The welding system A3 then causes the flux spraying device 7 to start spraying the flux when the flux spraying port of the spraying device 7 reaches the welding start point S. In addition, according to this embodiment, the time calculation unit 13 calculates the time T based on the travel speed and the distance L4 acquired from the distance setting unit 11. L4 Furthermore, flux control unit 18 calculates the time T L4 When the time has elapsed, the recovery device 75 is caused to start recovering the flux. This allows the welding system A3 to start recovering the flux 79 when the flux recovery port of the recovery device 75 comes to the welding start point S.

[0073] In this embodiment, the control device 1 calculates the time T L1 ~T L4 In the above description, the case where the flux spraying time is used has been described, but the present invention is not limited to this. For example, the control device 1 may use times calculated based on the distances from the welding start point S to the flux spraying port of the spraying device 7, the electrodes 8a and 8b, and the flux collection port of the collection device 75. In this case, the control device 1 may start the spraying of flux, the generation of an arc at the electrode 8a, the generation of an arc at the electrode 8b, and the collection of flux after the respective times have elapsed since the carriage 4 started traveling.

[0074] The submerged arc welding system according to the present invention is not limited to the above-described embodiment, and the specific configuration of each part of the submerged arc welding system according to the present invention can be freely designed and modified in various ways. [Explanation of symbols]

[0075] A1 to A2: welding system, 1: control device, 11: distance setting unit, 12: speed setting unit, 13: time calculation unit, 17: acceleration setting unit, 2, 2a, 2b, 2c: welding power supply unit, 4: cart, 7: spraying device, 75: recovery device, 8, 8a, 8b, 8c: electrodes, W: workpiece

Claims

1. 1. A submerged arc welding system for performing submerged arc welding, comprising: a first electrode that generates an arc on the workpiece to perform welding; a second electrode that arrives at the welding point of the workpiece later than the first electrode and generates an arc to perform welding; a carriage on which the first electrode and the second electrode are mounted and which travels along a welding line; a control device for controlling the carriage; Equipped with The control device a speed setting unit that sets a traveling speed of the carriage; a distance setting unit that sets a separation distance between a tip of the first electrode and a tip of the second electrode; a time calculation unit that calculates a delay time based on the traveling speed and the separation distance; Equipped with At the start of welding, generation of an arc at the first electrode is started, and travel of the carriage is started, and after the delay time has elapsed since the start of travel of the carriage, generation of an arc at the second electrode is started. Submerged arc welding system.

2. The time calculation unit calculates the delay time by dividing the separation distance by the traveling speed. The submerged arc welding system of claim 1 .

3. An acceleration setting unit that sets the acceleration of the carriage, The time calculation unit calculates the delay time using the acceleration. The submerged arc welding system of claim 1 .

4. a third electrode that arrives at the welding point later than the second electrode and generates an arc to perform welding; the distance setting unit further sets a second separation distance between a tip of the first electrode and a tip of the third electrode; the time calculation unit further calculates a second delay time based on the traveling speed and the second separation distance; the control device starts generation of an arc at the third electrode after the second delay time has elapsed since the carriage started traveling.

4. A submerged arc welding system according to claim 1.

5. Further, a spraying device is mounted on the carriage and sprays flux, The distance setting unit further sets a first distance between a welding start point and a flux spraying port of the spraying device in a traveling direction of the carriage, the time calculation unit further calculates a first time based on the traveling speed and the first distance; The control device When the first time period has elapsed since the carriage started traveling, the spraying device is caused to start spraying the flux; generating an arc at the second electrode when the delay time has elapsed since the arc was generated at the first electrode; The submerged arc welding system of claim 1 .

6. a recovery device that moves together with the carriage and recovers the flux; the distance setting unit further sets a second distance between the second electrode and a flux collection port of the collection device in the traveling direction of the carriage; the time calculation unit further calculates a second time based on the traveling speed and the second distance; the control device causes the recovery device to start recovering the flux when the second time has elapsed since the arc was generated at the second electrode.

6. The submerged arc welding system of claim 5.

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