JP5483555B2 - Arc welding method - Google Patents

Description

  The present invention relates to an arc welding method using a stitch pulse welding method.

  FIG. 8 is a diagram illustrating an example of a conventional welding system. The welding system 91 in the figure performs welding using a so-called stitch pulse welding method. The stitch pulse welding method is a welding method in which the heat effect on the base metal is easily suppressed by controlling the heat input and cooling during welding. When this stitch pulse welding method is used, it is said that the welding appearance can be improved and the amount of welding distortion can be reduced as compared with conventional thin plate welding (see, for example, Patent Document 1).

  The manipulator 9M automatically performs arc welding on the workpiece 9W, and includes an upper arm 93, a lower arm 94, a wrist portion 95, and a plurality of servo motors (not shown) for rotationally driving them. It is configured.

  The arc welding torch 9T is attached to the tip of the wrist portion 95 of the manipulator 9M, and is used to guide the welding wire 97 having a diameter of about 1 mm wound around the wire reel 96 to the teaching welding position of the workpiece 9W. It is. The welding power source 9WP supplies a welding voltage between the arc welding torch 9T and the workpiece 9W. When welding the workpiece 9W, the welding wire 97 is protruded from the tip of the arc welding torch 9T by a desired protruding length.

  The coil liner 92 is for guiding the welding wire 97, and is connected to the arc welding torch 9T.

  The teach pendant 9TP as an operation means is a so-called portable operation panel, and is used to set conditions necessary for performing the operation of the manipulator 9M, stitch pulse welding, and the like.

  The robot controller 9RC is for causing the manipulator 9M to control the welding operation, and includes a main controller, an operation controller, a servo driver (all not shown), and the like. Then, based on a work program taught by the teach pendant 9TP, an operation control signal is output from the servo driver to each servo motor of the manipulator 9M, and a plurality of axes of the manipulator 9M are rotated. Since the robot controller 9RC recognizes the current position based on an output from an encoder (not shown) provided in the servo motor of the manipulator 9M, the robot controller 9RC can control the tip position of the arc welding torch 9T. In the welded portion, stitch pulse welding is performed while repeating the welding, movement, and cooling described below.

  FIG. 9 is a diagram for explaining a state when stitch pulse welding is performed. The welding wire 97 protrudes from the tip of the arc welding torch 9T. The shield gas G is always blown from the arc welding torch 9T at a constant flow rate from the start of welding to the end of welding. Hereinafter, each state at the time of stitch pulse welding will be described.

  FIG. 4A shows a state when an arc is generated. Based on the set welding current and welding voltage, an arc a is generated between the tip of the welding wire 97 and the workpiece 9W, and the welding wire 97 melts to form a molten pool Y in the workpiece 9W. After the arc a is generated, the arc a is stopped after the taught welding time has elapsed.

  FIG. 2B shows a state after the arc is stopped. After the arc is stopped, the state after welding is maintained until the set cooling time has elapsed. That is, since the manipulator 9M and the arc welding torch 9T are stopped in the same manner as the welding state, only the shielding gas G is blown out from the arc welding torch 9T. It cools and solidifies.

  FIG. 5C shows a state where the arc welding torch 9T is moved to the next welding position. After the elapse of the cooling time, the arc welding torch 9T is moved to an arc restart point that is a position separated by a preset movement pitch Mp in the welding progress direction. The moving speed at this time is the set moving speed. The moving pitch is a distance adjusted so that the welding wire 97 is positioned on the outer peripheral side of the welding mark Y ′ after the molten pool Y is solidified as shown in FIG.

  FIG. 4D shows how the arc a is regenerated at the arc restart point. The weld pool Y is newly formed at the front end portion of the welding mark Y ', and welding is performed. As described above, in the stitch pulse welding system 91, the state in which welding is performed by generating an arc and the state in which cooling and movement are performed are alternately repeated. And a welding bead is formed so that the scale which is a welding trace may overlap.

  FIG. 10 is a view for explaining a weld bead formed after welding. As shown in the figure, a welding mark Sc is formed at the first arc starting point P1, and a similar welding mark Sc is also formed at a re-arc starting point P2 that is separated by a moving pitch Mp toward the welding traveling direction Dr. . Further welding marks Sc are sequentially formed after the re-arc start point P3. As described above, the scale-shaped weld beads B are formed as a result of the scales being the welding marks Sc being overlapped.

  In the above-described method, as shown in FIGS. 9B and 9C, the process of stopping the arc a and then regenerating the arc a is repeated. Each time the arc a is regenerated, there is a problem that spatter occurs and the appearance of the weld bead B deteriorates. Therefore, as shown in FIG. 11, a welding method has been proposed in which the arc a is not stopped and the re-generation of the arc a is unnecessary (for example, see Patent Document 2).

  As clearly shown in FIGS. 11B and 11C, unlike the cases shown in FIGS. 9B and 9C, the arc a is stopped when the molten pool Y is cooled. The state where the arc a is generated is maintained. Since it is no longer necessary to regenerate arc a, it is possible to suppress the occurrence of spatter. In this case, for example, an AC pulse current is used when welding, and a weak DC current is used when cooling and moving. According to this method, a droplet is formed when the polarity of the welding wire 97 is −, and when the polarity of the welding wire 97 is +, a relatively strong electromagnetic pinch force acts, so that the droplet forms the workpiece 9W. There is a tendency to fall into. Further, when a direct current is passed, the polarity of the welding wire 97 is fixed to +.

  However, when switching from alternating current pulse current to direct current, if the polarity of the welding wire 97 is-, the switching is made to a weak direct current with a relatively large droplet formed at the tip of the welding wire 97. . With this weak DC current, the electromagnetic pinch force is insufficient and the droplets may not drop onto the workpiece 9W. Furthermore, since the arc a is generated while the direct current is flowing, the droplet at the tip of the welding wire 97 gradually grows. For this reason, when the period in which the direct current is passed and the period in which the alternating pulse current is passed again, an excessively large droplet may be formed at the tip of the welding wire 97 in some cases. When such an unduly large droplet falls on the workpiece 9W, there is a problem that spatter occurs or the weld bead is greatly disturbed.

JP-A-6-55268 Japanese Patent Laid-Open No. 11-267839

  The present invention has been conceived under the circumstances described above, and an object thereof is to provide an arc welding method capable of forming a cleaner bead.

  The arc welding method provided by the present invention includes a first step of transferring a droplet by generating an arc between a consumable electrode and a base material, and generating an arc between the consumable electrode and the base material. An arc welding method in which the second step of cooling the molten pool formed in the base material is alternately repeated, wherein the first step includes an EP period in which the polarity of the consumable electrode is + and the consumable electrode An AC pulse current that repeats a unit period consisting of an EN period in which the polarity is negative is performed between the consumable electrode and the base material, and the second step is performed so that the polarity of the consumable electrode becomes +. In addition, a DC current is passed between the consumable electrode and the base material, and the AC pulse current has a waveform having a peak value in the EP period, and the EP period reaches the peak value. And the first half period has a second half period after reaching the peak value, characterized in that the transition from the first step to the second step during the second half period.

  In a preferred embodiment of the present invention, in the first step, the standard output time of the AC pulse current can be set, and is included in a period around the unit period from the scheduled end time of the standard output time. The second process is shifted from the first process during the latter half period.

  In a preferred embodiment of the present invention, when shifting from the second step to the first step, the AC pulse current is started from the first half period.

  In a preferred embodiment of the present invention, the alternating-current pulse current has a decreasing interval in which the current value decreases from the peak value in the latter half period, and a constant interval in which the current value is constant after the decreasing interval. Have.

  In such a method, a droplet grows mainly at the tip of the consumable electrode during the EN period, and the droplet drops from the consumable electrode to the base material during the EP period. According to the arc welding method of the present invention, in the latter half period, the process shifts from the first process to the second process. Therefore, when switching from the first process to the second process, the consumable electrode changes to the base material. The drop of the above droplet has been completed. For this reason, it is possible to prevent an excessively large droplet from being formed on the consumable electrode at the start of the second step. Therefore, according to the arc welding method of the present invention, when the first step is resumed, it is possible to prevent the formation of unduly large droplets on the consumable electrode, thereby preventing the occurrence of spatter and disturbance of the weld bead. A beautiful weld bead can be formed.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a figure which shows the structure of an example of the welding system for performing the arc welding method concerning this invention. It is a figure which shows the internal structure of the welding system shown in FIG. It is a figure which shows the change state of the welding condition value of the welding system shown in FIG. It is a figure which shows the change state of the welding current at the time of transfering from the droplet transfer period to an arc continuation period in an example of the arc welding method concerning this invention. It is a figure which shows the change state of the welding current at the time of transfer to the droplet transfer period from the arc continuation period in an example of the arc welding method concerning this invention. It is a figure which shows the change state of the welding current at the time of adjusting the time which shifts from a droplet transfer period to an arc continuation period. It is a figure which shows the change state of the welding current at the time of adjusting the time which transfers to the arc continuation period from the droplet transfer period in another embodiment of the arc welding method concerning this invention. It is a figure which shows the structure of an example of the conventional welding system. It is a figure explaining a state when performing stitch pulse welding. It is a figure for demonstrating the weld bead formed after welding construction. It is a figure for demonstrating a state when performing stitch pulse welding.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an example of a welding system suitable for carrying out the arc welding method according to the present invention. A welding system A shown in FIG. 1 includes a welding robot 1, a robot control device 2, and a welding power source device 3. The welding robot 1 automatically performs, for example, arc welding on the welding base material W. The welding robot 1 includes a base member 11, a plurality of arms 12, a plurality of motors 13, a welding torch 14, a wire feeding device 16, and a coil liner 19.

  The base member 11 is fixed to an appropriate location such as a floor. Each arm 12 is connected to the base member 11 via a shaft.

  The welding torch 14 is provided at the distal end portion of the wrist portion 12 a provided on the most distal end side of the welding robot 1. The welding torch 14 guides a welding wire 15 having a diameter of, for example, about 1 mm as a consumable electrode to a predetermined position in the vicinity of the welding base material W. The welding torch 14 is provided with a shield gas nozzle (not shown) for supplying a shield gas such as Ar. The motor 13 is provided at both ends or one end of the arm 12 (partially omitted from illustration). The motor 13 is rotationally driven by the robot control device 2. By this rotational drive, the movement of the plurality of arms 12 is controlled, and the welding torch 14 can move freely up and down, front and rear, and left and right.

  The motor 13 is provided with an encoder (not shown). The output of this encoder is given to the robot controller 2. Based on this output value, the robot controller 2 recognizes the current position of the welding torch 14.

  The wire feeding device 16 is provided in the upper part of the welding robot 1. The wire feeding device 16 is for feeding the welding wire 15 to the welding torch 14. The wire feeding device 16 includes a feeding motor 161, a wire reel (not shown), and wire push means (not shown). Using the feed motor 161 as a drive source, the wire push means feeds the welding wire 15 wound around the wire reel to the welding torch 14.

  One end of the coil liner 19 is connected to the wire feeder 16 and the other end is connected to the welding torch 14. The coil liner 19 is formed in a tube shape, and a welding wire 15 is inserted through the coil liner 19. The coil liner 19 guides the welding wire 15 delivered from the wire feeding device 16 to the welding torch 14. The fed welding wire 15 protrudes outside from the welding torch 14 and functions as a consumable electrode.

  FIG. 2 is a diagram showing an internal configuration of welding system A shown in FIG.

  The robot control device 2 shown in FIGS. 1 and 2 is for controlling the operation of the welding robot 1. As shown in FIG. 2, the robot control device 2 includes an operation control circuit 21, an interface circuit 22, a calculation unit 23, and a teach pendant TP.

  The operation control circuit 21 has a microcomputer and a memory (not shown). The memory stores a work program in which various operations of the welding robot 1 are set. Further, the operation control circuit 21 sets a robot moving speed VR described later. The operation control circuit 21 gives an operation control signal Mc to the welding robot 1 based on the work program, the coordinate information from the encoder, the robot moving speed VR, and the like. By this operation control signal Mc, each motor 13 is rotationally driven, and the welding torch 14 is moved to a predetermined welding start position of the welding base material W or moved along the in-plane direction of the welding base material W.

  The teach pendant TP is connected to the operation control circuit 21 and the calculation unit 23. The teach pendant TP is for setting various operations by the user.

  A setting value input by the user in the teach pendant TP is sent from the teach pendant TP to the calculation unit 23. The calculation unit 23 calculates the set value and sends the result to the operation control circuit 21.

  The interface circuit 22 is for exchanging various signals with the welding power source device 3. The interface circuit 22 is supplied with a current setting signal Is, an output start signal On, and a feed speed setting signal Ws from the operation control circuit 21.

  The welding power supply device 3 is a device for applying a welding voltage Vw between the welding wire 15 and the welding base material W and flowing a welding current Iw, and for feeding the welding wire 15. is there. As shown in FIG. 2, the welding power source device 3 includes an output control circuit 31, a current detection circuit 32, a feed control circuit 34, an interface circuit 35, and a voltage detection circuit 36.

  The interface circuit 35 is for exchanging various signals with the robot control device 2. Specifically, the current setting signal Is, the output start signal On, and the feed speed setting signal Ws are sent from the interface circuit 22 to the interface circuit 35.

  The output control circuit 31 has an inverter control circuit composed of a plurality of transistor elements. The output control circuit 31 performs precise welding current waveform control with a high-speed response to a commercial power source (for example, three-phase 200 V) input from the outside by an inverter control circuit.

  The output of the output control circuit 31 has one end connected to the welding torch 14 and the other end connected to the welding base material W. The output control circuit 31 applies a welding voltage Vw between the welding wire 15 and the welding base material W via a contact tip provided at the tip of the welding torch 14 and causes a welding current Iw to flow. Thereby, an arc a is generated between the tip of the welding wire 15 and the welding base material W. The welding wire 15 is melted by the heat generated by the arc a. The welding base material W is welded.

  The output control circuit 31 is supplied with the current setting signal Is and the output start signal On from the operation control circuit 21 via the interface circuits 35 and 22.

  The current detection circuit 32 is for detecting the welding current Iw flowing through the welding wire 15. The current detection circuit 32 outputs a current detection signal Id corresponding to the welding current Iw to the output control circuit 31 and the operation control circuit 21.

  The voltage detection circuit 36 is for detecting a welding voltage Vw that is a voltage at the output terminal of the output control circuit 31. The voltage detection circuit 36 outputs a voltage detection signal Vd corresponding to the welding voltage Vw to the output control circuit 31.

  The feed control circuit 34 outputs a feed control signal Fc for feeding the welding wire 15 to the feed motor 161. The feed control signal Fc is a signal indicating the feed speed of the welding wire 15. In addition, an output start signal On and a feed speed setting signal Ws from the operation control circuit 21 are sent to the feed control circuit 34 via the interface circuits 35 and 22.

  Next, an arc welding method using the welding system A will be described. Below, the general method of stitch pulse welding is demonstrated first. Then, the arc welding method in which a cleaner scale-like bead is formed will be specifically described.

  First, a general welding method of stitch pulse welding will be described with reference to FIG. FIG. 4A shows a change state of the robot moving speed VR, FIG. 5B shows a change state of the time average value of the absolute value of the welding voltage Vw, and FIG. The change state of is shown. The robot moving speed VR is a moving speed of the welding torch 14 along a predetermined welding progress direction (corresponding to the welding progress direction Dr shown in FIG. 10) in the in-plane direction of the welding base material W.

  First, a transition welding start process is generally performed by inputting a welding start signal St (see FIG. 2) from the teach pendant TP. In the welding start process, the operation control circuit 21 outputs an output start signal On to the output control circuit 31 and the feed control circuit 34. The output control circuit 31 applies a welding voltage Vw between the welding wire 15 and the welding base material W. Thereby, the arc a is ignited. Then, as shown in FIG. 3, welding is performed by repeating a unit welding period Tα including a droplet transfer period T1 and an arc continuation period T2. In the droplet transfer period T1, the welding voltage Vw1 is applied and the welding current Iw1 is applied to cause the droplet transfer to form a molten pool. On the other hand, in the arc continuation period T2, the welding torch 14 is moved while applying the welding voltage Vw2 and flowing the welding current Iw2 with almost no droplet transfer and while maintaining the arc a. Details will be described below.

(1) Droplet transfer period T1 (time t1 to t2)
In the droplet transfer period T1, the process for forming the molten pool Y shown in FIGS. 9A and 11A in the description of the prior art is performed. The first step in the present invention is a step performed during the droplet transfer period T1. In the droplet transfer period T1, the robot moving speed VR is set to 0 as shown in FIG. Therefore, the welding torch 14 is stopped with respect to the welding base material W. As shown in FIG. 6B, a welding voltage Vw1 having a time average value of absolute values of a voltage value vw1 is applied as the welding voltage Vw. As shown in FIG. 5C, a welding current Iw1 that is an AC pulse current that swings between current values iw1p to iw1n flows as the welding current Iw. In the droplet transfer period T1, constant voltage control is performed. In the constant voltage control, the welding current Iw is determined by the feeding speed of the welding wire 15 if the welding conditions such as the material, diameter, protruding length of the welding wire 15 and electrode polarity are determined. That is, the welding current Iw1 is set by the feed speed setting signal Ws.

  4 and 5 show the change over time of the welding current Iw1 in detail. The time scale in FIGS. 4 and 5 is very small compared to the time scale in FIG. 4 and 5, the vertical axis indicating the welding current Iw indicates that the current that flows when the welding wire 15 becomes an anode is positive. FIG. 4 shows the end of the droplet transfer period T1, and FIG. 5 shows the start of the droplet transfer period T1.

  As shown in FIGS. 4 and 5, the welding current Iw1 repeats a unit period Te including an EP period Tep in which the polarity of the welding wire 15 is + and an EN period Ten in which the polarity of the welding wire 15 is −. In the EP period Tep, the welding current Iw1 becomes the electrode positive polarity current Iep. In the EN period Ten, the welding current Iw1 becomes the electrode negative polarity current Ien. The electrode negative polarity current Ien flows at a constant value iw1n. On the other hand, the electrode positive polarity current Iep increases or decreases so as to take the peak value iw1p.

  The EP period Tep includes a peak period Tp in which the electrode positive polarity current Iep takes a peak value iw1p, an increase period Tu that is the first half period before the peak period Tp, and a decrease period that is the second half period after the peak period Tp. Td and a predetermined period Tb. The increase period Tu starts when the electrode negative polarity current Ien is switched to the electrode positive polarity current Iep. During the increase period Tu, the welding current Iw1 increases. The increase period Tu ends when the current value of the welding current Iw1 reaches the peak value iw1p, and the peak period Tp starts. During the peak period Tp, the value of the welding current Iw1 remains at the peak value iw1p. After the end of the peak period Tp, the decrease period Td is started. During the decrease period Td, the welding current Iw1 decreases. When the current value of the welding current Iw1 decreases to a predetermined value iw1d, the decrease period Td ends, and a certain period Tb starts. During a certain period Tb, the current value of the welding current Iw1 flows at a constant value iw1d. After the fixed period Tb ends, switching from the electrode positive polarity current Iep to the electrode negative polarity current Ien is performed.

  The peak value iw1p, the values iw1n, iw1d, the peak period Tp, and the EN period Ten are set to predetermined values. During the certain period Tb, feedback control is performed so that the average value of the welding voltage Vw becomes equal to a predetermined welding voltage set value. By this control, the length of the arc a is controlled to an appropriate value.

In the EN period Ten, since the welding wire 15 is on the cathode side, droplets tend to grow at the tip of the welding wire 15. On the contrary, in the EP period Tep, the peak value iw1p is taken and a large electromagnetic pinch force acts on the welding wire 15, so that the droplets tend to fall. After the droplet falls, the EN period Ten is entered and the droplet grows again. Thus, one droplet moves from the welding wire 15 to the welding base material W during one unit period Te.

(2) Arc duration T2 (time t2 to t3)
In the arc continuation period T2 shown in FIG. 3, the process of cooling the molten pool Y shown in FIGS. 11B and 11C in the description of the prior art is performed while the arc a is continued. The second step in the present invention is a step performed during the arc continuation period T2.

  As shown in FIG. 3A, the robot moving speed VR is set to V2 at time t2 when the arc continuation period T2 starts. As a result, the welding torch 14 starts to move along a predetermined welding direction. As shown in FIG. 5B, a welding voltage Vw2 having a time average value of absolute value vw2 is applied as the welding voltage Vw. In the arc continuation period T2, unlike the droplet transfer period T1, constant current control is performed. As shown in FIG. 5C, a constant welding current Iw2 having a current average value iw2 flowing in the time average value of the absolute value flows as the welding current Iw. The current value iw2 is a small value such that droplet transfer is not easily performed. The welding current Iw2 is a so-called electrode positive polarity current that flows in a state where the welding wire 15 is an anode and the welding base material W is a cathode. The welding wire 15 is fed toward the welding base material W at a feeding speed smaller than the value in the droplet transfer period T1 (not shown).

  Thereafter, the droplet transfer period T1 starts again from time t3. In this way, the unit welding period Tα including the droplet transfer period T1 and the arc continuation period T2 is repeated.

  General stitch pulse welding is performed as described above. Next, an arc welding method for forming a more beautiful scale-like bead will be specifically described.

  The droplet transfer period T1 can be set in advance as a standard output time of AC pulse current, for example, and the time t2 that is the scheduled end time can also be specifically set. In the arc welding method of the present embodiment, the end time of the droplet transfer period T1 is adjusted based on the time t2.

  As shown in FIG. 4, when the welding current Iw1 is the decrease period Td or the constant period Tb at time t2, switching from the droplet transfer period T1 to the arc continuation period T2 is performed at time t2. As shown in FIG. 6, at time t2, when the welding current Iw1 is the EN period Ten, the increase period Tu, or the peak period Tp, the switching from the droplet transfer period T1 to the arc continuation period T2 is performed at time t2 ′. Do. The time t2 'is the end time of the decrease period Td that is later than the time t2 and within the unit period Te from the time t2.

  In this way, the situation at the time of transition from the welding current Iw1 to the welding current Iw2 is always similar to the situation at the time of transition from the decrease period Td to the fixed period Tb. For this reason, as shown in FIG. 4, it is estimated that the front-end | tip part of the welding wire 15 restrict | squeezed by the electromagnetic pinch force in the reduction | decrease period Td falls as a droplet before and after switching to the welding current Iw2. Accordingly, during the arc continuation period T2, unduly large droplets are not formed and dropped, and a more beautiful scale-like bead is formed.

  As shown in FIG. 7, the time t2 'may be the end time of the decrease period Td that is before the time t2 and within the unit period Te from the time t2.

  Further, in the present embodiment, the output control circuit 31 performs waveform control so that the welding current Iw1 is started from the increase period Tu when the arc continuation period T2 shifts to the droplet transfer period T1. For example, as shown in FIG. 5, when the welding current Iw2 is switched to the welding current Iw1 at time t3, the increase period Tu is started from time t3.

  Since the welding current Iw2 flows also during the arc continuation period T2, as shown in FIG. 5, the tip of the welding wire 15 is slightly melted before time t3. If the EN period Ten is started at time t3 in this state, an unreasonably large droplet is formed. Furthermore, as the EP period Tep elapses, the unduly large droplets drop onto the weld base material W, and the weld bead is greatly disturbed. On the other hand, when the increase period Tu is started from time t3, since the EN period Ten during which the droplets are likely to grow does not pass, the growth of the droplets is suppressed. For this reason, the droplet that falls in the first EP period Tep of the droplet transfer period T1 is relatively small. Therefore, according to the arc welding method of this embodiment, a more beautiful scale-shaped bead is formed.

  Moreover, according to such an arc welding method, since the polarity does not change at time t3, the transition from the welding current Iw2 to the welding current Iw1 can be performed more smoothly.

  The scope of the present invention is not limited to the embodiment described above. The specific configuration of each part of the welding system used in the present invention can be varied in design in various ways, and the details of the arc welding method according to the present invention can be changed as appropriate. For example, in the above embodiment, the current value gradually increases from the current value iw2 to the current value iw1p in the increase period Tu starting from time t3 shown in FIG. This may be changed so that the current value gradually increases from an arbitrary value between the current values iw2 to iw1p.

A welding system 1 welding robot 11 base member 12 arm 12a wrist 13 motor 14 welding torch 15 welding wire (consumable electrode)
16 Wire feeder 161 Feed motor 2 Robot controller 21 Operation control circuit 22 Interface circuit 23 Operation unit 3 Welding power supply device 31 Output control circuit 32 Current detection circuit 34 Feed control circuit 35 Interface circuit 36 Voltage detection circuit Fc Feed Control signal Iep electrode positive polarity current Ien electrode negative polarity current Is current setting signal Iw, Iw1, Iw2 welding current iw1n, iw1p, iw1d, iw2 current value Mc operation control signal On output start signal St welding start signal T1 droplet transfer period T2 Arc duration period Te Unit period Ten EN period Tep EP period Tu Increase period (first half period)
Tp peak period Td decrease period (second half period)
Tb Fixed period (second half period)
TP Teach pendant Tα Unit welding period VR Robot movement speed Vw, Vw1, Vw2 Welding voltage vw1, vw2 Voltage value W Welding base material (base material)
Ws Feeding speed setting signal

Claims (3)

A first step of transferring droplets by generating an arc between the consumable electrode and the base material; and a molten pool formed on the base material while generating an arc between the consumable electrode and the base material. An arc welding method that alternately repeats the second step of cooling,
In the first step, an AC pulse current that repeats a unit period consisting of an EP period in which the polarity of the consumable electrode is + and an EN period in which the polarity of the consumable electrode is − is generated between the consumable electrode and the base material. Done by flowing,
The second step is performed by passing a direct current between the consumable electrode and the base material so that the polarity of the consumable electrode becomes +,
The AC pulse current is a waveform having a peak value in the EP period,
The EP period has a first half period before reaching the peak value and a second half period after reaching the peak value,
In the first step, the standard output time of the AC pulse current can be set,
When the scheduled end time of the standard output time is included in the first half period, by changing the standard output time, during the latter half period included in a period that is around the unit period from the scheduled end time. An arc welding method, wherein the process proceeds from the first step to the second step. 2. The arc welding method according to claim 1 , wherein the alternating-current pulse current is started from the first half period when the second process is shifted to the first process. The AC pulse current is in the second half period, a decreasing segment where the current value decreases from the peak value, after this reduction period, and a predetermined section where the current value becomes constant, according to claim 1 or 2 The arc welding method described in 1.

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