JP4848036B2 - Arc welding method - Google Patents

Description

  The present invention relates to an arc welding method.

  FIG. 13 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. 14 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. 15 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 method described above, as shown in FIG. 14B, FIG. 14C, etc., 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. 16, a welding method has been proposed in which the arc a is not stopped and the re-generation of the arc a is not required (for example, see Patent Document 2).

  As clearly shown in FIGS. 16B and 16C, unlike the cases shown in FIGS. 14B and 14C, 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. Thus, research and development of stitch pulse welding that can form a cleaner bead has been conventionally performed.

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 first aspect of the present invention includes a first step of transferring a droplet by generating an arc between a consumable electrode and a base material, and between the consumable electrode and the base material. A unit welding step including a second step of cooling the molten pool formed on the base material while generating an arc, and repeating the unit welding step, wherein the unit welding step is defined in each unit welding step. And a step of changing the one or more types of welding condition values reflected in the molten state of the consumable electrode or the molten state of the base material step by step for each unit welding step. in is one of the welding condition value decreases monotonically time of performing the first step, in the step of the change, always, the consumable electrode and the base material in the first step In the step of keeping the average value of the absolute value of the welding current flowing between the constant current and changing the welding current, the welding voltage applied between the consumable electrode and the base material is always applied in the first step. of the average value of the absolute value, and remain constant, the step of the change, Ru is performed for a predetermined period of time from the start arc welding.

An arc welding method provided by the second aspect of the present invention includes a first step of transferring a droplet by generating an arc between a consumable electrode and a base material, and between the consumable electrode and the base material. A unit welding step including a second step of cooling the molten pool formed on the base material while generating an arc, and repeating the unit welding step, wherein the unit welding step is defined in each unit welding step. And a step of changing one or more types of welding condition values reflected in the molten state of the consumable electrode or the molten state of the base material step by step for each unit welding step, the second step In the step of moving the consumable electrode relative to the base material along the in-plane direction of the base material at the consumable electrode moving speed and changing the same, the welding condition value is one of the welding condition values. 2 The moving distance of the consumable electrode with respect to the base material in the in-plane direction during each of the second steps in the step of monotonously decreasing and changing the consumable electrode moving speed is about the same, and In the changing step, the time for performing the second step is increased stepwise, and the changing step is executed for a predetermined period from the middle of arc welding.

  In a preferred embodiment of the present invention, the consumable electrode moving speed is kept constant during each of the second steps in the changing step.

  In a preferred embodiment of the present invention, in the changing step, the absolute value of the absolute value of the welding current flowing between the consumable electrode and the base material in the first step is always maintained constant. In the step of changing, the step of always changing the average value of the absolute value of the welding voltage applied between the consumable electrode and the base material in the first step is kept constant. In, the time for performing the first step is always kept constant.

  According to such a configuration, the optimum welding condition value is determined even if the thickness of the base material, the gap width between the base materials, the angle between the base materials, and the temperature of the base material change. be able to. Thereby, the molten state of the consumable electrode or the molten state of the base material can be optimized. As a result, the formed bead can be made cleaner.

  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 showing composition of an example of a welding system concerning a 1st embodiment of the present 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 concerning 1st Embodiment. It is a figure which shows the change state of the welding current in a droplet transfer period. It is a figure which shows the change state of the welding condition value in 1st Embodiment. It is a figure which shows transition of the length of the droplet transfer period in 1st Embodiment. It is a figure which shows the change state of the welding condition value in 2nd Embodiment. It is a figure which shows the change state of the robot moving speed in 2nd Embodiment. It is a figure which shows the change state of the welding condition value in a 1st reference example . It is a figure which shows the change state of the value of the welding voltage in the 1st reference example, and the value of welding current. It is a figure which shows the change state of the welding condition value in a 2nd reference example . It is a figure which shows the change state of the welding condition value in a 3rd reference example . 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.

<First Embodiment>
FIG. 1 is a diagram illustrating a configuration of an example of a welding system according to a first embodiment of 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, movement of the plurality of arms 12 is controlled so that the welding torch 14 can freely move up and down, front and rear, and right and left.

  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. 15) 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 processing for forming the molten pool Y shown in FIGS. 14A and 16A in the description of the prior art is performed. 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 having an average absolute value of a current value iw1 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.

  FIG. 4 is a diagram showing in detail the time change of the welding current Iw1. As shown in the figure, the welding current Iw1 is an AC pulse current. The current value iw1 in FIG. 4 matches the current value iw1 in FIG. The time scale in FIG. 4 is very small compared to the time scale in FIG. In FIG. 4, the vertical axis indicating the welding current Iw is positive for the current that flows when the welding wire 15 becomes the anode.

  As understood from this figure, the welding current Iw1 takes the electrode positive polarity current Iep and the electrode negative polarity current Ien once in the pulse period Te. The electrode positive polarity current Iep is a current that flows when the welding wire 15 is an anode and the welding base material W is a cathode. The welding current Iw1 is the electrode positive polarity current Iep during the periods Tu, Tp, Td, Tb. The electrode negative polarity current Ien is a current that flows when the welding wire 15 is a cathode and the welding base material W is an anode. It is during the period Tn that the welding current Iw1 is the electrode negative polarity current Ien. The welding current Iw1 increases during the period Tu. The welding current Iw1 flows at a constant value Iepp during the period Tp. The welding current Iw1 decreases during the period Td. The welding current Iw1 flows at a constant value Iepb during the period Tb. The welding current Iw1 flows at a constant value Ienp during the period Tn. The value obtained by dividing the absolute value of the welding current Iw1 in the period Tn by time integration (area Sen) by the absolute value of the welding current Iw1 in one pulse cycle Te by time integration (area Sep + area Sen) is the EN ratio. It is called. By adjusting the EN ratio, the melting rate of the welding wire 15 and the heat input to the welding base material W can be controlled with the same welding current.

  Values Iepp, Iepb, Ienp, and periods Tp, Tn are set to predetermined values. During the period Tb, feedback control is performed so that the average value of the welding voltage Vw becomes equal to a predetermined welding voltage setting value. By this control, the length of the arc a is controlled to an appropriate value. A value obtained by time averaging the absolute value of the welding current Iw1 matches the current value iw1.

(2) Arc duration T2 (time t2 to t3)
In the arc continuation period T2 shown in FIG. 3, the process for cooling the molten pool Y shown in FIGS. 16B and 16C in the description of the prior art is performed while the arc a is continued.

  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-shaped bead will be described in detail with reference to FIGS.

  Hereinafter, for simplification, unless otherwise specified, the value iw1 obtained by averaging the welding current Iw in the droplet transfer period T1 is referred to as the value of the welding current Iw. Similarly, a value vw1 obtained by averaging the welding voltage Vw in the droplet transfer period T1 is referred to as a value of the welding voltage Vw. Similarly, the EN ratio of the welding current Iw in the droplet transfer period T1 is simply referred to as the EN ratio of the welding current Iw. Similarly, the robot movement speed VR in the arc continuation period T2 is simply referred to as the robot movement speed VR.

  In the present embodiment, the following welding condition values are changed during welding. In this specification, the welding condition value is a value that is defined in each unit welding period Tα and reflected in the molten state of the welding wire 15 or the molten state of the welding base material W. Such welding condition values are, for example, the length of the droplet transfer period T1, the robot moving speed VR, the EN ratio of the welding current Iw, the value of the welding current Iw, or the value of the welding voltage Vw.

  The welding condition values that must be specified with specific numerical values before the start of welding are the length of the droplet transfer period T1, the value of the welding current Iw, and the robot moving speed VR. The welding condition values already stored in the database in the operation control circuit 21 before the start of welding are the value of the welding voltage Vw and the EN ratio of the welding current Iw. In order to obtain a cleaner bead, the value of the welding voltage Vw or the EN ratio of the welding current Iw can be finely adjusted. In the following, both specifying the welding condition value specifically and fine-tuning the welding condition value are referred to as inputting the welding condition value.

  The case where a welding condition value is changed for a predetermined period from the time of starting arc welding is demonstrated using FIG. 5A shows a change state of the robot moving speed VR, FIG. 5B shows a change state of the EN ratio of the welding current Iw, and FIG. 5C shows a change of the length of the droplet transfer period T1. The state (d) shows a change state of the welding voltage Vw, and the figure (e) shows a change state of the welding current Iw. The horizontal axis in FIG. 5 is the distance from the point where arc welding is started. The further to the right in FIG. 5, the farther from the point where arc welding starts. As shown in FIG. 5C, the welding condition value to be changed in the present embodiment is the length of the droplet transfer period T1.

  First, before starting welding, a welding condition value at the point a1, that is, a welding condition value at the time of starting welding and a welding condition value from the point a2 are input from, for example, the teach pendant TP in FIG. Then, the calculating part 23 calculates the welding condition value in the period (transition period TT1) from point a1 to point a2 as a value between the welding condition value at point a1 and the welding condition value at point a2. The calculating part 23 calculates the welding condition value in the period from a1 point to a2 point as a value which decreases monotonously in the said period. FIG. 5 schematically shows the welding condition values, but actually, the length of the droplet transfer period T1 for each unit welding process in the transfer period TT1 shows a change state as shown in FIG. Further, as the a2 point, a position that can be said that the welding base material W is sufficiently heated may be adopted. The distance from point a1 to point a2 is, for example, 15 to 20 mm.

  Next, the arc a is ignited and welding is started. The welding base material W is hardly heated at the start of welding. In order to heat input with such a weld base material W, the length of the droplet transfer period T1, which is one of the welding condition values, is set relatively long at the point a1 at the start of welding.

  Next, the length of the droplet transfer period T1 is shortened step by step from the point a1 to the point a2. After the welding at point a2, the length of the droplet transfer period T1 is kept constant.

  In such a configuration, at the start of welding, the length of the droplet transfer period T1 is set to be relatively long. Therefore, the time which must be welded in the state where the temperature of the welding base material W is low can be shortened. Thereby, the width of the bead to be formed and the shape of the bead can be made constant.

  In addition, after the start of welding, the length of the droplet transfer period T1 is shortened step by step. Therefore, as the temperature of the welding base material W rises, the heat given to the welding base material W can be gradually reduced. Further, by reducing the heat applied to the welding base material W, it is possible to suppress excessive application of heat to the welding base material W when the temperature of the welding base material W is sufficiently increased. The suppression of excessive heat input to the weld base material W contributes to preventing the weld base material W from being excessively melted in a state where the temperature of the weld base material W is sufficiently increased.

  In the present embodiment, in order to adjust the heat input to the welding base material W, only the length of the droplet transfer period T1 is changed without changing the values of the welding current Iw and the welding voltage Vw. When the values of the welding current Iw and the welding voltage Vw are changed, the arc a tends to become unstable. However, in this embodiment, the values of the welding current Iw and the welding voltage Vw are not changed. Therefore, according to this embodiment, it is difficult to cause inconvenience that the arc a becomes unstable.

  In order to adjust the heat input to the welding base material W, it is preferable to change the length of the droplet transfer period T1, but the present invention is not limited to this, and other welding condition values may be changed. The heat input to the welding base material W can be adjusted. For example, in the present embodiment, the EN ratio may be increased from point a1 to point a2. Further, for example, in the present embodiment, the value of the welding voltage Vw may be decreased from the point a1 to the point a2. Further, for example, in the present embodiment, the value of the welding current Iw may be decreased from the point a1 to the point a2.

  Hereinafter, another embodiment of the present invention will be described. In these drawings, the same or similar elements as those in the above embodiment are denoted by the same reference numerals as those in the above embodiment, and description thereof will be omitted as appropriate.

Second Embodiment
A case where the welding condition value is changed for a predetermined period from the middle of arc welding will be described as a second embodiment of the present invention with reference to FIGS. FIG. 7 shows a change state of each welding condition value as in FIG. FIG. 7A shows a change state of the robot moving speed VR, FIG. 7B shows a change state of the EN ratio of the welding current Iw, and FIG. 7C shows a change of the length of the droplet transfer period T1. The state (d) shows a change state of the welding voltage Vw, and the figure (e) shows a change state of the welding current Iw. The horizontal axis in FIG. 7 is the distance from the point where arc welding starts. The further to the right in FIG. 7, the farther from the point where arc welding starts. As shown in FIG. 5A, the welding condition value to be changed in the present embodiment is the value of the robot moving speed VR.

  First, before starting welding, a welding condition value up to the point b1 and a welding condition value from the point b2 are input from the teach pendant TP shown in FIG. 2, for example. Then, the calculating part 23 makes the welding condition value in the period (transition period TT2) from the b1 point to the b2 point as a value between the welding condition value up to the b1 point and the welding condition value from the b2 point. calculate. The calculating part 23 calculates the welding condition value in the period from b1 point to b2 point as a value which decreases monotonously in the said period. FIG. 7 schematically shows the welding condition values. Actually, however, the value of the robot movement speed VR for each unit welding process in the transition period TT2 varies for each unit welding process as shown in FIG. And in each unit welding process, it is constant.

  Next, the arc a is ignited and welding is started. The temperature of the welding base material W is gradually increased by the application of heat until reaching the point b1. In order to cool the molten pool for a longer period from the time of welding at the point b1 to the time of welding at the point b2, the value of the robot moving speed VR is decreased stepwise. After the welding at the point b2, the value of the robot moving speed VR is kept constant.

  In such a configuration, the value of the robot movement speed VR is decreased stepwise from the time of welding at the point b1 to the time of welding at the point b2. Accordingly, since the distance traveled during the arc duration T2 is constant, the length of the arc duration T2 gradually increases. Therefore, the molten pool formed in the weld base material W can be cooled for a longer time. Thereby, the outline of each shape of the scale formed in each droplet transfer period T1 can be clarified. Thus, according to this embodiment, the bead formed in the weld base material W can be made cleaner.

  In the present embodiment, only the robot moving speed VR is changed without changing the value of the welding current Iw, the value of the welding voltage Vw, and the length of the droplet transfer period T1. When the value of the welding current Iw, the value of the welding voltage Vw, or the length of the droplet transfer period T1 is changed, the amount of the molten metal changes. Therefore, the size of the scale in the formed bead is different for each scale. However, in this embodiment, the value of the welding current Iw, the value of the welding voltage Vw, and the length of the droplet transfer period T1 are not changed. Therefore, according to this embodiment, it is hard to produce the problem that the scale differs for every scale. This is suitable for forming a cleaner bead.

  In order to form a clean bead by facilitating solidification of the molten pool, it is preferable to change the robot moving speed VR. However, the present invention is not limited to this, and other welding condition values may be changed. . For example, in the present embodiment, the EN ratio may be decreased from the b1 point to the b2 point. Further, for example, in the present embodiment, the length of the droplet transfer period T1 may be decreased from the b1 point to the b2 point. Further, for example, in the present embodiment, the value of the welding voltage Vw may be decreased from the b1 point to the b2 point. Further, for example, in the present embodiment, the value of the welding current Iw may be decreased from the b1 point to the b2 point.

< First Reference Example >
9 and 10, as a first reference example of the present invention, an example in which the welding condition value is changed when the thickness of the welding base material W gradually changes during welding will be described. FIG. 9 shows a change state of each welding condition value, similarly to FIGS. 5 and 7. 9A shows a change state of the robot movement speed VR, FIG. 9B shows a change state of the EN ratio of the welding current Iw, and FIG. 9C shows a change of the length of the droplet transfer period T1. The state (d) shows a change state of the welding voltage Vw, and the figure (e) shows a change state of the welding current Iw. The horizontal axis in FIG. 9 is the distance from the point where arc welding starts. The further to the right in FIG. 9, the farther from the point where arc welding starts. As shown in FIG. 4D and FIG. 4E, the welding condition values to be changed in this reference example are the value of the welding voltage Vw and the value of the welding current Iw. As shown in FIG. 9, the thickness of the welding base material W gradually increases from the point c1 to the point c2.

  First, before starting welding, a welding condition value up to the point c1 and a welding condition value from the point c2 are input from the teach pendant TP shown in FIG. Then, the calculation unit 23 sets the welding condition value in the period from the c1 point to the c2 point (transition period TT3) as a value between the welding condition value up to the c1 point and the welding condition value from the c2 point. calculate. The calculation unit 23 calculates the welding condition value during the period from the point c1 to the point c2 as a value that monotonously increases during the period. FIG. 9 schematically shows the welding condition values. Actually, the welding voltage Vw and the welding current Iw for each unit welding process in the transition period TT3 are as shown in FIG. And is constant in each unit welding process.

  Next, the arc a is ignited and welding is started. Until the point c1, the thickness of the weld base material W is constant. Until reaching the point c1, welding is performed while maintaining each welding condition value at a constant value. From the point c1 to the point c2, the thickness of the weld base material W increases. When the thickness of the weld base material W is increased, it is necessary to further input heat to the weld base material W in order to perform appropriate welding. Therefore, the value of the welding current Iw and the value of the welding voltage Vw are increased stepwise from the time of welding at the point c1 to the time of welding at the point c2. After welding at the point c2, the value of the welding current Iw and the value of the welding voltage Vw are kept constant.

  In such a configuration, the value of the welding current Iw and the value of the welding voltage Vw are increased stepwise from the time of welding at the point c1 to the time of welding at the point c2. Therefore, the amount of heat input to the welding base material W can be gradually increased. Thereby, even if the welding base material W becomes thick, a beautiful bead can be formed.

Further, in order to increase the amount of heat input to the welding base material W, the robot movement speed VR may be decreased from the point c1 to the point c2. However, when the robot moving speed VR is decreased, the time required for welding becomes longer. On the other hand, in this reference example , since the robot moving speed VR is not decreased, the time required for welding does not increase.

In order to change the amount of heat input to the welding base material W from the point c1 to the point c2, it is preferable to change the value of the welding current Iw and the value of the welding voltage Vw. However, the present invention is not limited to this, and other The welding condition value may be changed. For example, in this reference example , the robot moving speed VR may be decreased from the point c1 to the point c2. For example, in this reference example , the EN ratio may be increased from the c1 point to the c2 point. For example, in this reference example , the length of the droplet transfer period T1 may be increased from the point c1 to the point c2.

< Second Reference Example >
Using FIG. 11, as a second reference example of the present invention, an example in which the welding condition value is changed when the gap between the welding base materials W gradually changes during welding will be described. FIG. 11 shows the change state of each welding condition value as in FIGS. 5, 7, and 9. 11A shows a change state of the robot moving speed VR, FIG. 11B shows a change state of the EN ratio of the welding current Iw, and FIG. 11C shows a change of the length of the droplet transfer period T1. The state (d) shows a change state of the welding voltage Vw, and the figure (e) shows a change state of the welding current Iw. The horizontal axis in FIG. 11 is the distance from the point where arc welding is started. The further to the right in FIG. 11, the farther from the point where arc welding is started. As shown in FIG. 4B, the welding condition value to be changed in this reference example is the EN ratio of the welding current Iw. As shown in FIG. 11, the gap between the welding base materials W gradually increases from the point d1 to the point d2.

  First, before starting welding, a welding condition value up to the point d1 and a welding condition value from the point d2 are input from the teach pendant TP shown in FIG. 2, for example. Then, the calculation part 23 sets the welding condition value in the period (transition period TT4) from the d1 point to the d2 point as a value between the welding condition value until the d1 point and the welding condition value from the d2 point. calculate. The calculation unit 23 calculates the welding condition value in the period from the point d1 to the point d2 as a value that monotonously increases in the period. Although FIG. 11 schematically shows the welding condition values, in actuality, as described above, the value of the EN ratio of the welding current Iw for each unit welding process in the transition period TT4 is determined for each unit welding process. And is constant in each unit welding process.

  Next, the arc a is ignited and welding is started. Until reaching the point d1, the gap of the welding base material W is constant. Until reaching the point d1, welding is performed while maintaining each welding condition value constant. From the point d1 to the point d2, the gap of the weld base material W increases. If the gap of the welding base material W becomes large, it is necessary to melt more welding wires 15 in order to perform appropriate welding. Therefore, the EN ratio of the welding current Iw is increased stepwise from the time of welding at the point d1 to the time of welding at the point d2. After the welding at the point d2, the EN ratio of the welding current Iw is kept constant.

  In such a configuration, the EN ratio of the welding current Iw in the droplet transfer period T1 is increased in stages from the time of welding at the point d1 to the time of welding at the point d2. Therefore, the welding wire 15 is easily melted gradually. Thereby, a clean bead can be formed even if the gap of the welding base material W becomes large.

In this reference example , the welding current Iw value and the welding voltage Vw are not changed in order to promote melting of the welding wire 15. When the value of the welding current Iw and the value of the welding voltage Vw are changed, the heat input amount to the welding base material W may change. If the amount of heat input to the weld base material W changes, the bead width and bead shape formed on the weld base material W may change. However, in this reference example , the value of the welding current Iw and the value of the welding voltage Vw are not changed in order to change the melting amount of the welding wire 15, and only the EN ratio of the welding current Iw is changed. is there. Therefore, according to this reference example , it is possible to increase the melting amount of the welding wire 15 in a state where the change in the heat input amount to the welding base material W is small. Thereby, a more beautiful bead can be formed.

In order to change the melting amount of the welding wire 15 from the point d1 to the point d2, it is preferable to change the EN ratio of the welding current Iw. However, the present invention is not limited to this, and other welding condition values are changed. May be. For example, in this reference example , the length of the droplet transfer period T1 may be increased from the point d1 to the point d2. When the length of the droplet transfer period T1 is increased, the robot moving speed VR may be decreased from the point d1 to the point d2. For example, in this reference example , the value of the welding current Iw may be increased from the point d1 to the point d2. Further, for example, in this reference example , the value of the welding voltage Vw may be increased from the point d1 to the point d2.

< Third reference example >
A case where the welding condition value is changed when the angle between the welding base materials W gradually changes during welding will be described as a third reference example of the present invention with reference to FIG. FIG. 12 shows a change state of each welding condition value as in FIGS. 5, 7, 9, and 11. 12A shows a change state of the robot moving speed VR, FIG. 12B shows a change state of the EN ratio of the welding current Iw, and FIG. 12C shows a change of the length of the droplet transfer period T1. The state (d) shows a change state of the welding voltage Vw, and the figure (e) shows a change state of the welding current Iw. The horizontal axis in FIG. 12 is the distance from the point where arc welding is started. The further to the right in FIG. 12, the farther from the point where arc welding starts. As shown in FIG. 4D, the welding condition value changed in the present reference example is the value of the welding voltage Vw. As shown in FIG. 12, the angle between the weld base materials W gradually increases from the e1 point to the e2 point.

First, before starting welding, a welding condition value up to the point e1 and a welding condition value from the point e2 are input from, for example, the teach pendant TP shown in FIG. Then, the calculation unit 23 calculates the welding condition value in the period from the e1 point to the e2 point (transition period TT5) between the input welding condition value up to the e1 point and the welding condition value from the e2 point. Calculated as the value of. The calculation unit 23 also calculates the welding condition value in the period from the e1 point to the e2 point as a value that monotonously increases in the period. Figure 12 is in fact are shown welding conditions values schematically, similarly to the above-described reference example, the value of the welding voltage Vw in the transition period TT5 varies for each unit welding process, and each unit It is constant in the welding process.

  Next, the arc a is ignited and welding is started. The angle between the welded base materials W is constant until reaching the point e1. Until reaching the e1 point, welding is performed while maintaining each welding condition value constant. From the e1 point to the e2 point, the angle between the welding base materials W increases. When the angle between the weld base materials W increases, the heating state of the welding wire 15 by the molten pool formed in the weld base material W changes. For this reason, the amount of energy required for melting the welding wire 15 changes. Therefore, the value of the welding voltage Vw is increased step by step from the time of welding at the point e1 to the time of welding at the point e2. After welding at the point e2, the value of the welding voltage Vw is kept constant.

  In such a configuration, the value of the welding voltage Vw is increased step by step from the time of welding at the point e1 to the time of welding at the point e2. Therefore, the welding wire 15 can be appropriately melted. Thereby, even if the angle between the welding base materials W becomes large, a beautiful bead can be formed.

In this reference example , only the value of the welding voltage Vw is changed so that the welding wire 15 can be appropriately melted from the point e1 to the point e2. If not only the value of the welding voltage Vw but also the value of the welding current Iw is changed from the e1 point to the e2 point, the length of the droplet transfer period T1 is also changed in order to maintain the molten metal amount. There must be. On the other hand, in this reference example , the value of the welding current Iw is not changed in order to maintain the melting amount of the welding wire 15, and it is not necessary to change the length of the droplet transfer period T1, and the time required for welding is long. The inconvenience that it becomes becomes difficult to occur.

In order to appropriately melt the welding wire 15 from the point e1 to the point e2, it is preferable to change the value of the welding current Vw. However, the present invention is not limited to this, and other welding condition values may be changed. Good. For example, in this reference example , the robot moving speed VR may be decreased from the e1 point to the e2 point. For example, in this reference example , the length of the droplet transfer period T1 may be increased from the e1 point to the e2 point. For example, in this reference example , the value of the welding current Iw may be increased from the e1 point to the e2 point.

  The scope of the present invention is not limited to the embodiment described above. The specific configuration of each part of the present invention can be changed in various ways. When performing welding once, for example, any of the welding methods shown in the first embodiment and the second embodiment may be used.

A (arc) 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 (Arc welding) Robot controller 21 Operation control circuit 22 Interface circuit 23 Arithmetic 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 current Ien Electrode negative current Is Is Current setting signal Iw, Iw1, Iw2 Welding current iw1, iw2 Current value Mc Operation control signal On Output start signal St Weld start signal T1 Droplet transition period ( (First period)
T2 Arc duration (second period)
Te Pulse period Tu, Tp, Td, Tb, Tn Period TP Teach pendant Tα Unit welding period VR Robot moving speed Vw, Vw1, Vw2 Welding voltage vw1, vw2 Voltage value W Welding base material (base material)
Ws Feeding speed setting signal

Claims (4)

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 comprising a unit welding step including a second step of cooling, and repeating the unit welding step,
A step of changing one or more types of welding condition values, which are defined in each unit welding step and reflected in the molten state of the consumable electrode or the molten state of the base material, step by step for each unit welding step; In addition,
In the changing step, the time for performing the first step, which is one of the welding condition values , is monotonously reduced ,
In the changing step, the absolute value of the welding current flowing between the consumable electrode and the base material in the first step is always kept constant,
In the changing step, the absolute value of the welding voltage applied between the consumable electrode and the base material in the first step is always kept constant ,
Step of the change, Ru is performed for a predetermined period of time from the start arc welding, arc welding method. 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 comprising a unit welding step including a second step of cooling, and repeating the unit welding step,
A step of changing one or more types of welding condition values, which are defined in each unit welding step and reflected in the molten state of the consumable electrode or the molten state of the base material, step by step for each unit welding step; In addition,
In the second step, the consumable electrode is moved relative to the base material at a consumable electrode moving speed along the in-plane direction of the base material,
In the changing step, the consumable electrode moving speed in the second step, which is one of the welding condition values, is monotonously decreased,
The moving distance of the consumable electrode with respect to the base material in the in-plane direction during each of the second steps in the changing step is the same as each other,
In the step of changing, the time for performing the second step is increased stepwise,
The step of changing is an arc welding method executed for a predetermined period from the middle of arc welding. The arc welding method according to claim 2, wherein the consumable electrode moving speed is maintained constant during each of the second steps in the changing step . In the changing step , the absolute value of the welding current flowing between the consumable electrode and the base material in the first step is always kept constant,
In the changing step, the absolute value of the welding voltage applied between the consumable electrode and the base material in the first step is always kept constant,
In the step of the change, always the time for performing the first step, it remains constant, the arc welding method according to claim 3.