JP2013071145A - Method for starting welding in two-wire welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the bead quality of a welding start part in two-wire welding.SOLUTION: A method for starting welding in two-wire welding carried out by generating arc to a welding wire and feeding a filler wire in contact with the latter half of a molten pool, includes: starting the feed Ws of the welding wire (time t3); generating arc to the welding wire (time t4); starting the feed Fs of the filler wire (time t5) with a delay of a first predetermined period Td1 from the time of generating the arc; energizing a predetermined filler wire welding current Iwf when the filler wire contacts the molten pool (time t6); and stopping the energization of the filler wire welding current Iwf at a point of time t7 when a second predetermined period Td2 has elapsed from the filler wire feed starting time. The first predetermined period Td1 can thereby be set shorter than the prior art, and in consequence, the bead quality of the welding start part can be improved.

Description

  The present invention relates to a welding start method of two-wire welding for improving the bead of a welding start portion in two-wire welding performed by feeding a filler wire while contacting a molten pool of a consumable electrode arc.

  The two-wire welding method in which the filler wire is fed while being brought into contact with the molten pool formed by the consumable electrode arc is a high-speed weldability because two wires of the consumable electrode arc and the filler wire are used. And excellent weldability. In particular, when high-speed welding is performed by the two-wire welding method, it is important to feed the filler wire in contact with the molten pool from behind the consumable electrode arc in order to prevent a humping bead. This is because when the filler wire is fed into the consumable electrode arc and melted, the cooling effect of the molten pool is reduced, and the rise of the latter half of the molten pool cannot be suppressed by the filler wire. This is because there is almost no suppression effect. On the other hand, if the filler wire is fed in contact with the second half of the molten pool at the peripheral edge of the arc and melted by the heat of the molten pool, the molten pool is efficiently cooled and melted by the filler wire. The latter half of the pond is suppressed and the formation of the humping bead can be suppressed. In the following description, the wire of the consumable electrode arc is described as a welding wire and is distinguished from the filler wire. As a welding method for generating a consumable electrode arc, a carbon dioxide arc welding method, a mag welding method, a MIG welding method, a pulse mag welding method, a pulse MIG welding method, a consumable electrode AC pulse arc welding method, or the like is used.

  The welding start method for two-wire welding is generally performed as follows. When an activation signal is input from the outside to the welding device, feeding of the welding wire is started and a welding voltage is applied between the welding wire and the base material. When the welding wire comes into contact with the base material, a welding current is passed to generate a consumable electrode arc. When the consumable electrode arc is generated, the welding torch starts moving in the welding direction. Also, after a consumable electrode arc is generated, the filler wire is fed after a delay of a first predetermined period. During this predetermined period, the molten pool is gradually enlarged by the consumable electrode arc. When the filler wire comes into contact with the molten pool, the tip of the filler wire is melted by the heat from the molten pool, the contact state is maintained, and the state shifts to the steady welding state. No current is passed through the filler wire. In the first predetermined period, the molten pool formed by the consumable electrode arc grows to a size including the insertion position of the filler wire, and the temperature of the molten pool reaches a value at which the filler wire can be melted. It is a period. In the first predetermined period, the appropriate value varies depending on the joint shape, the thickness of the base material, the material of the base material, and the like, and is about 0.4 to 0.6 seconds, for example.

  The distance between the tip of the filler wire and the base material before the filler wire starts feeding (hereinafter referred to as the initial distance) is controlled to be a substantially constant value at the end of the previous welding. However, there is some variation in the initial distance of the filler wire. When the initial distance fluctuates, the period from the start of feeding the filler wire after the first predetermined period has elapsed until the contact with the molten pool (hereinafter referred to as the initial distance feeding period) fluctuates. The period from when the consumable electrode arc is generated to when the filler wire contacts the molten pool varies. If the period from the occurrence of the consumable electrode arc to the contact of the filler wire can be controlled so as not to fluctuate, the filler wire is transferred to the molten pool in a timely manner at the moment when the molten pool is in the proper state described above. Can be contacted. In patent document 1, in order to suppress the fluctuation | variation of this initial distance, before starting feeding of a welding wire, the step which feeds a filler wire until it contacts with a base material is added. In this way, the initial distance is 0 mm, and the period from the occurrence of the consumable electrode arc until the filler wire comes into contact and is fed is equal to the first predetermined period. Moreover, in patent document 2, before starting feeding of a welding wire, the step which feeds a filler wire until it contacts with a base material, and feeds it in the reverse direction only for the predetermined distance after that is added. In this way, the initial distance is always equal to the predetermined distance. The operation for controlling the initial distance to a predetermined value is hereinafter referred to as an initial distance setting operation.

  In the above-described welding start method of two-wire welding, the filler wire is not fed during the first predetermined period, so that the bead is formed only by the consumable electrode arc. For this reason, the surplus height of the bead at the welding start portion becomes lower than the steady period, the bead appearance is deteriorated, and the strength is also lowered. In order to improve this problem, it is conceivable to shorten the first predetermined period and to advance the filler wire feeding start timing. However, if feeding of the filler wire is started before the molten pool grows until the filler wire can be smoothly melted by the heat from the molten pool, the filler wire may be melted poorly and become a welding defect. is there. In order to solve this problem, in Patent Document 3, a consumable electrode arc is generated between the welding wire and the base material at the start of welding, and a filler wire arc is generated between the filler wire and the base material. When the first predetermined period elapses, the filler wire arc is extinguished and shifted to a state of being fed in contact. That is, during the first predetermined period from the start of welding, an arc is also generated in the filler wire so that it is melted by the heat from its own arc. If it does in this way, the surplus height of the bead of a welding start part will become substantially equal to a steady period. However, since two arcs are generated close to each other at the welding start portion, the arcs interfere with each other, resulting in a new problem that an increase in the amount of spatter and arc breakage are likely to occur.

JP 2009-106984 A JP 2009-106985 A JP 2009-72809 A

  As described above, in the prior art including Patent Document 1 and Patent Document 2, a period in which the beads are formed only by the consumable electrode arc by the welding wire is required, and therefore, the surplus height of the beads at the welding start portion is steady. There exists a subject that it becomes lower than a welding part and the quality of a bead worsens.

  In Patent Document 3, a bead is formed by two arcs of a consumable electrode arc by a welding wire and an arc by a filler wire during a first predetermined period from the start of welding. For this reason, the surplus height of the bead at the welding start portion is substantially the same as that of the steady welding portion. However, the interference between the two arcs tends to increase the amount of spatter generated and cause arc breakage.

  Accordingly, an object of the present invention is to provide a welding start method for two-wire welding that improves the quality of the bead at the welding start portion and does not cause an increase in the amount of spatter generated or arc breakage.

In order to solve the above-described problems, the invention of claim 1 is configured to generate an arc between the welding wire and the base metal and feed the filler wire while contacting the latter half of the molten pool formed by the arc. In the welding start method of 2-wire welding performed by feeding,
The feeding of the welding wire is started, the arc is generated between the welding wire and the base material, and the feeding of the filler wire is delayed by a first predetermined period from the time when the arc is generated. When the filler wire comes into contact with the molten pool formed by the arc, a predetermined filler wire welding current is energized, and when the second predetermined period has elapsed from the start of feeding the filler wire, the filler Stop energizing the wire welding current,
This is a welding start method for two-wire welding.

The invention of claim 2 sets the feeding speed of the filler wire at a lower speed before the second predetermined period has elapsed than after the second predetermined period has elapsed.
The welding start method for two-wire welding according to claim 1, wherein:

The invention of claim 3 adds a step of feeding until the filler wire comes into contact with the base material before starting feeding of the welding wire.
The welding start method for two-wire welding according to claim 1 or 2, characterized by the above.

According to a fourth aspect of the present invention, before the feeding of the welding wire is started, the filler wire is fed until it comes into contact with the base material, and after the contact, the feeding direction is reversed so that the tip of the filler wire is moved. Adding a step of stopping feeding by separating from the base material by a predetermined distance;
The welding start method for two-wire welding according to claim 1 or 2, characterized by the above.

  According to the present invention, the feeding of the filler wire is started with a delay of the first predetermined period from the time when the arc is generated between the welding wire and the base material, and the filler wire comes into contact with the molten pool formed by the arc. Then, a predetermined filler wire welding current is applied, and the supply of the filler wire welding current is stopped when the second predetermined period has elapsed from the start of filler wire feeding. In the present invention, since current is supplied to the filler wire to assist melting, even if the filler wire is inserted in a state where the size of the molten pool is smaller than that in the prior art, the filler wire can be sufficiently melted. For this reason, the first predetermined period can be set shorter than in the prior art. Therefore, in the present invention, since the first predetermined period from when the arc is generated to when the filler wire is started to be fed can be shortened, the quality of the bead at the welding start portion can be improved. Furthermore, in the present invention, since there is no influence on the arc, the arc state such as an increase in the amount of spatter generated and arc breakage does not become unstable.

It is a block diagram of the welding apparatus for enforcing the welding start method of 2 wire welding which concerns on embodiment of this invention. FIG. 2 is a block diagram of a welding wire welding power source PSW that constitutes the welding apparatus described above in FIG. 1. FIG. 2 is a block diagram of a filler wire welding power source PSF constituting the welding apparatus described above in FIG. 1. It is a timing chart of each signal in Drawing 1 for explaining a welding start method of 2 wire welding concerning an embodiment of the invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram of a welding apparatus for carrying out a welding start method for two-wire welding according to an embodiment of the present invention. Hereinafter, each component will be described with reference to FIG.

  This welding apparatus includes a welding torch WT surrounded by a broken line, a welding wire welding power source PSW, a filler wire welding power source PSF, a robot control device RC, and a robot (not shown). The welding torch WT includes carbon dioxide gas and carbon dioxide gas from the tip of the welding torch WT provided with a welding wire power supply tip 4a for supplying power to the welding wire 1a and a filler wire power supply tip 4b for supplying power to the filler wire 1b. A shielding gas (not shown) such as a mixed gas of oxygen and argon gas is ejected. The welding torch WT is held by a robot (not shown) and moved along the weld line according to a work program stored in the robot controller RC.

  The welding wire 1a is fed to the inside of the welding torch WT at the welding wire feeding speed Ws by the rotation of the welding wire feeding roll 5a coupled to the welding wire feeding motor WM. A consumable electrode arc 3a is generated. The filler wire 1b is fed through the welding torch WT at the filler wire feed speed Fs by the rotation of the filler wire feed roll 5b coupled to the filler wire feed motor FM, and is fed to the latter half of the molten pool 2a. Inserted in contact. The welded portion in the figure shows a state in a steady period, in which no current is passed through the filler wire 1b, and the welding torch WT moves at the welding speed.

  A welding voltage Vww is applied between the welding wire 1a and the base material 2, and a welding current Iww is conducted in the consumable electrode arc 3a. In the figure, the welding direction is the left direction. A molten pool 2a is formed by the preceding consumable electrode arc 3a. A filler wire welding voltage Vwf is applied between the filler wire 1b and the base material 2, and a filler wire welding current Iwf is applied. During the steady period, since the output of the filler wire welding power source PSF is stopped, Vwf = 0V and Iwf = 0A. The filler wire 1b is inserted in contact with the latter half of the molten pool 2a, and is melted by heat from the molten pool 2a. The filler wire 1b is fed outside the consumable electrode arc 3a. This is to prevent the filler wire 1b from being directly melted by the consumable electrode arc 3a as described above. The advancing angle of the welding wire 1a is in the range of about 0 to 30 °, and in the same figure, it is a case of a straightness (0 °). The advance angle of the filler wire 1b is in the range of 20 to 50 °. That is, the filler wire 1b is inserted diagonally forward.

  The welding wire welding power source PSW is a power source for energizing the welding current Iww by applying the welding voltage Vww between the welding wire 1a and the base material 2 via the welding wire power supply tip 4a. From the welding wire welding power source PSW, a welding wire feeding control signal Wc is sent to the welding wire feeding motor WM, and the welding wire feeding speed Ws is controlled. When the welding voltage Vww is applied from the welding wire power supply PSW via the welding wire power supply tip 4a, the welding wire 1a is set to the + side. The welding power source PSW for welding wire is a power source having constant voltage characteristics as usual. Therefore, the value of the welding current Iww is determined by the welding wire feed speed Ws.

  The filler wire welding power source PSF applies a filler wire welding current Iwf by applying a filler wire welding voltage Vwf between the filler wire 1b and the base material 2 via the filler wire power supply tip 4b. It is a power supply. A filler wire feed control signal Fc is sent from the filler wire welding power source PSF to the filler wire feed motor FM to control the filler wire feed speed Fs. When the filler wire welding voltage Vwf is applied from the filler wire welding power source PSF via the filler wire power supply tip 4b, the filler wire 1b is set to the + side. The filler wire welding power source PSF is a power source having a constant current characteristic in order to control the value of the filler wire welding current Iwf to a predetermined value.

  The robot controller RC outputs the activation signal On and the initial distance set signal Lss to the welding wire welding power source PSW, and the energization determination signal Cd is input from the welding wire welding power source PSW. Further, the robot controller RC outputs the activation signal On and the energization determination signal Cd to the filler wire welding power source PSF, and the initial distance set signal Lss is input from the filler wire welding power source PSF. The initial distance set signal Lss is generated inside the filler wire welding power source PSF and sent to the welding wire welding power source PSW via the robot controller RC. The energization determination signal cd is a signal for determining that the consumable electrode arc 3a is generated between the welding wire 1a and the base material 2 by the energization of the welding current Iww, and is generated inside the welding wire welding power source PSW. Then, the robot controller RC is sent to the filler wire welding power source PSF. The robot controller RC moves the welding torch WT mounted on the robot to the welding start position according to the stored work program and stops. Then, an activation signal On is output to both power sources PSW and PSF. When the energization determination signal Cd becomes High level, the welding torch WT is moved along the weld line. Details of these signals will be described later with reference to FIGS. A timing chart of each signal at the start of welding will be described later with reference to FIG.

  FIG. 2 is a block diagram of a welding wire welding power source PSW that constitutes the welding apparatus described above with reference to FIG. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200 V, performs output control such as inverter control according to a drive signal Dv described later, and outputs a welding voltage Vww and a welding current Iww. Although not shown, the power supply main circuit PM includes a primary rectifier circuit that rectifies commercial power, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current into high frequency alternating current, and high frequency alternating current An inverter transformer that steps down the voltage to a voltage value suitable for arc welding, a secondary rectifier circuit that rectifies the stepped-down high-frequency alternating current, and a reactor that smoothes the rectified direct current. The welding wire 1a is fed while being fed through the welding wire feeding tip 4a by the rotation of the welding wire feeding roll 5a coupled to the welding wire feeding motor WM, and is consumed between the base metal 2 and the welding wire 1a. An electrode arc 3a is generated. The structure of the welding torch is as shown in FIG. 1 described above, but is shown here in a simplified manner.

  The voltage detection circuit VD detects the welding voltage Vww and outputs a voltage detection signal Vd. The voltage average value calculation circuit VAV averages (smooths) the voltage detection signal Vd by passing it through a low-pass filter (cutoff frequency of about 1 to 10 Hz), and outputs a voltage average value signal Vav.

  The welding voltage setting circuit VR outputs a predetermined welding voltage setting signal Vr. The voltage error amplification circuit EV amplifies an error between the welding voltage setting signal Vr and the voltage average value signal Vav, and outputs a voltage error amplification signal Ev. With this circuit, the welding power source becomes a power source having a constant voltage characteristic. The drive circuit DV receives the voltage error amplification signal Ev, the start signal On and the initial distance set signal Lss from the robot controller RC, and both the start signal On and the initial distance set signal Lss are at a high level (start and set completion) When it is, pulse width modulation control is performed based on the voltage error amplification signal Ev, and a drive signal Dv for driving the inverter circuit in the power supply main circuit is output. Thereby, welding power supply PSW for welding wires starts an output.

  The current detection circuit ID detects the welding current Iww and outputs a current detection signal Id. The energization determination circuit CD receives the current detection signal Id and, when the value is equal to or greater than a predetermined threshold value, determines that the welding current Iww is energized and controls the energization determination signal Cd which becomes a high level by robot control. Output to the device RC. The threshold value is set to about 5A, for example.

  The steady period welding wire feed speed setting circuit WSR outputs a predetermined steady period welding wire feed speed setting signal Wsr. The slowdown welding wire feed speed setting circuit WIR outputs a predetermined slowdown welding wire feed speed setting signal Wir. The feed switching circuit SW receives the above-described steady period welding wire feed speed setting signal Wsr, the above-described slowdown welding wire feed speed setting signal Wir, and the above-described energization judgment signal Cd. When the level is low (non-energized), the welding wire feed speed setting signal Wir for slowdown is output as the welding wire feed speed setting signal Wr. When the level is high (energized), the welding wire feed speed setting for the steady period is set. The signal Wsr is output as the welding wire feed speed setting signal Wr. The welding wire feed control circuit WC receives the welding wire feed speed setting signal Wr, the start signal On and the initial distance set signal Lss from the robot controller RC, and both the start signal On and the initial distance set signal Lss are High. At the level (startup and setting completion), the welding wire feed control signal Wc for feeding the welding wire 1a at the feed speed determined by the welding wire feed speed setting signal Wr is sent to the above-described welding wire feed motor. Output to WM.

  FIG. 3 is a block diagram of a filler wire welding power source PSF constituting the welding apparatus described above with reference to FIG. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM inputs a commercial power supply (not shown) such as a three-phase 200V, performs output control such as inverter control according to a drive signal Dv described later, and outputs a filler wire welding voltage Vwf and a filler wire welding current Iwf. To do. Although not shown, the power supply main circuit PM includes a primary rectifier circuit that rectifies commercial power, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current into high frequency alternating current, and high frequency alternating current An inverter transformer that steps down the voltage to a voltage value suitable for arc welding, a secondary rectifier circuit that rectifies the stepped-down high-frequency alternating current, and a reactor that smoothes the rectified direct current. The filler wire 1b is fed so as to come into contact with the molten pool while being fed through the filler wire feeding chip 4b by the rotation of the filler wire feeding roll 5b coupled to the filler wire feeding motor FM. During the steady period, the filler wire 1b is fed in contact with the molten pool in a state where the filler wire welding voltage Vwf = 0V and the filler wire welding current Iwf = 0A. The time change of the filler wire welding voltage Vwf and the filler wire welding current Iwf at the start of welding will be described later with reference to FIG. The structure of the welding torch is as shown in FIG. 1 described above, but is shown here in a simplified manner.

  The first on-delay circuit TD1 receives the energization determination signal Cd from the robot controller RC as an input, delays the time when the energization determination signal Cd changes to the high level (energization) by a first predetermined period Td1, The on-delay signal Tds1 is output. The first on-delay signal Tds1 changes from the Low level to the High level when the first predetermined period Td1 elapses from the time when the consumable electrode arc 3a is generated. The second on-delay circuit TD2 receives the first on-delay signal Tds1 as an input, and on-delays the time point when the first on-delay signal Tds1 changes to the high level by the second predetermined period Td2 to obtain the second on-delay signal. Outputs Tds2. The second on-delay signal Tds2 changes from the Low level to the High level when the second predetermined period Td2 elapses from the time when the filler wire 1b starts feeding for welding.

  The current detection circuit ID detects the filler wire welding current Iwf and outputs a current detection signal Id. The contact determination circuit SD determines that the filler wire 1b and the base material 2 are in contact with each other when the current detection signal Id is equal to or greater than a threshold value, and outputs a contact determination signal Sd that is at a high level. This threshold value is set to a value that can determine the energization of 0.1 A. The contact determination current setting circuit IIR outputs a predetermined contact determination current setting signal Iir. The value of the contact determination current setting signal Iir may be a value that can determine that the filler wire 1b is in contact with the base material 2, and is set to a value that does not melt the filler wire 1b. For example, it is set to about 0.1A. The initial period filler wire welding current setting circuit ISR outputs a predetermined initial period filler wire welding current setting signal Isr. The current switching circuit SI receives the contact determination current setting signal Iir, the initial period filler wire welding current setting signal Isr, and the first on-delay signal Tds1, and the first on-delay signal Tds1 is at a low level. At this time, the contact determination current setting signal Iir is output as the filler wire welding current setting signal Ifr. When the level is High, the initial period filler wire welding current setting signal Isr is output as the filler wire welding current setting signal Ifr. The first on-delay signal Tds1 changes from the Low level to the High level when the first predetermined period Td1 has elapsed since the occurrence of the consumable electrode arc 3a. The current error amplification circuit EI amplifies an error between the filler wire welding current setting signal Ifr and the current detection signal Id, and outputs a current error amplification signal Ei. With this circuit, the welding power source becomes a power source with constant current characteristics. However, in order to prevent an arc from being generated between the filler wire 1b and the base material 2 (molten pool 2a), the welding power source is set so that the maximum value of the filler wire welding voltage Vwf is as low as about 5V. The output is limited to. The drive circuit DV receives the current error amplification signal Ei, the activation signal On from the robot controller RC, and the second on-delay signal Tds2 as an input, and the second time from when the activation signal On changes to the high level (activation). During the period until the on-delay signal Tds2 changes to the high level, the pulse width modulation control is performed based on the current error amplification signal Ei, and the drive signal Dv for driving the inverter circuit in the power supply main circuit is output. To do. Thereby, the filler wire welding power source PSF is output during a certain period at the start of welding, and the output is stopped during a steady period.

  The regular period filler wire feed speed setting circuit FSR outputs a predetermined steady period filler wire feed speed setting signal Fsr. The initial period filler wire feed speed setting circuit FIR outputs a predetermined initial period filler wire feed speed setting signal Fir. The feed switching circuit SW receives the above-mentioned steady period filler wire feed speed setting signal Fsr, the above initial period filler wire feed speed setting signal Fir, and the above-mentioned second on-delay signal Tds2 as inputs. When the delay signal Tds2 is at the Low level, the initial period filler wire feed speed setting signal Fir is output as the filler wire feed speed setting signal Fr. When the delay signal Tds2 is at the High level, the steady period filler wire feed speed setting signal Fsr is output. The filler wire feed speed setting signal Fr is output.

The filler wire feed control circuit FC receives the activation signal On from the robot controller RC, the contact determination signal Sd, the filler wire feed speed setting signal Fr, and the first on-delay signal Tds1 as follows. The initial distance set signal Lss is output to the robot controller RC, and the filler wire feed control signal Fc is output to the filler wire feed motor FM.
1) When the activation signal On changes to the high level (activation), the operation shifts to the initial distance setting operation, and the feeding of the filler wire 1b is started. When the contact determination signal Sd changes to a high level (contact), a filler wire feed control signal Fc for sending back and stopping the filler wire 1b for a predetermined reverse feed period is output. When this operation is completed, the initial distance set signal Lss is set to High level and output. The value of the filler wire feed speed setting signal Fr during the initial distance setting operation is a value determined by the initial period filler wire feed speed setting signal Fir. Since the filler wire 1b is reversely fed at a constant feeding speed for a certain period (reverse feeding period), the expected distance after the feeding stops is a predetermined distance.
2) When the first on-delay signal Tds1 changes to the High level, the filler wire feed control signal Fc for feeding the filler wire 1b according to the value of the filler wire feed speed setting signal Fr is output.

  FIG. 4 is a timing chart of each signal in FIGS. 1 to 3 for explaining a welding start method of two-wire welding according to the embodiment of the present invention. (A) shows the time change of the activation signal On, (B) shows the time change of the energization determination signal Cd, (C) shows the time change of the initial distance set signal Lss, (D) shows the change over time of the welding voltage Vww, (E) shows the change over time of the welding wire feed speed Ws, (F) shows the change over time of the welding current Iww, (G) ) Shows a time change of the contact determination signal Sd, FIG. 11H shows a time change of the first on-delay signal Tds1, FIG. 11I shows a time change of the second on-delay signal Tds2, and FIG. (J) shows the change over time of the filler wire welding voltage Vwf, (K) shows the change over time of the filler wire feed speed Fs, and (L) shows the change over time of the filler wire welding current Iwf. Hereinafter, a description will be given with reference to FIG.

(1) Initial distance setting operation at times t1 to t3 At time t1, as shown in FIG. 5A, when the activation signal On changes to a high level, the operation proceeds to the initial distance setting operation described above. When the activation signal On changes to the high level, as shown in FIG. 5K, the filler wire feed speed Fs becomes a value determined by the positive filler wire feed speed setting signal Fir for the initial period, and the filler wire Feeding of 1b is started. At the same time, as shown in FIG. 6J, the filler wire welding voltage Vwf has a low voltage value of about 5V, for example. When filler wire 1b comes into contact with base material 2 at time t2, as shown in FIG. 6J, filler wire welding voltage Vwf decreases to near 0V, and immediately after that, filler wire 1b is separated from base material 2 by reverse feeding. So it rises and returns to around 5V. Further, as shown in FIG. 9L, the filler wire welding current Iwf becomes a value (for example, about 0.1 A) determined by the contact determination current setting signal Iir when the voltage is reduced, and the filler wire 1b is removed from the base material 2. When the voltage rises away, it becomes 0A. At time t2, as shown in FIG. 5G, the contact determination signal Sd becomes High level for a short time. In response to this, as shown in FIG. 4K, the filler wire feed speed Fs becomes a value determined by the negative period filler wire feed speed setting signal Fir, and the filler wire 1b is fed backward. Start. Then, at time t3 when a predetermined reverse feed period has elapsed from time t2, as shown in FIG. 4K, the filler wire feed speed Fs becomes 0 and feed is stopped. In response to this, the initial distance set signal Lss changes to the high level as shown in FIG. Thereby, the initial distance setting operation is completed. As described above, the filler wire welding voltage Vwf is limited to a low value so as not to generate an arc between the filler wire 1b and the base material 2. During the period from the time t1 to the time t3, the welding wire welding power source PSW is in an output and feed stop state, so that the energization determination signal Cd is at the low level as shown in FIG. As shown in (D), the welding voltage Vww is 0 V, as shown in (E), the welding wire feed speed Ws is 0, and as shown in (F), the welding current Iww. Is 0A. During this period, the first on-delay signal Tds1 is at the low level as shown in FIG. 11H, and the second on-delay signal Tds2 is at the low level as shown in FIG. .

(2) Slow-down period from time t3 to t4 At time t3, when the initial distance set signal Lss changes to the high level as shown in FIG. 10C, the welding voltage Vww is applied as shown in FIG. Is a no-load voltage value of about 80 V, and as shown in FIG. 5E, the welding wire feed speed Ws is a value determined by the slow-down welding wire feed speed setting signal Wir. It is fed at a slow feeding speed of about min. As shown in FIG. 9F, the welding current Iww is 0A because it is in a no-load state.

(3) First predetermined period Td1 from time t4 to t5
When the welding wire 1a comes into contact with the base material 2 at time t4 and the consumable electrode arc 3a is generated, the welding voltage Vww decreases to near 0V for a short time as shown in FIG. It becomes a voltage value. At the same time, the welding current Iww is energized as shown in FIG. 5F, and the energization determination signal Cd is changed to the high level as shown in FIG. In response to this, as shown in FIG. 5E, the welding wire feed speed Ws becomes a value determined by the welding wire feed speed setting signal Wsr for the steady period, and the feed speed is increased. When the energization determination signal Cd changes to the high level, the welding torch starts moving in the welding direction by the robot.

(4) Second predetermined period Td2 from time t5 to t7
At time t5 when the first predetermined period Td1 has elapsed from time t4 when the energization determination signal Cd has changed to high level, the first on-delay signal Tds1 changes to high level as shown in FIG. In response to this, as shown in FIG. 5K, the filler wire feed speed Fs becomes a value determined by the initial period filler wire feed speed setting signal Fir, and the filler wire 1b is fed again. When the filler wire 1b comes into contact with the molten pool at time t6, the filler wire welding current Iwf becomes a value determined by the initial period filler wire welding current setting signal Isr, as shown in FIG. As shown in FIG. 6J, the filler wire welding voltage Vwf decreases from about 5V to near 0V because the filler wire 1b contacts the molten pool at time t6. The period from time t5 to t6 is the initial distance feeding period, which is about 0.05 seconds, for example.

(5) Steady period after time t7 At time t7 when the second predetermined period has elapsed from time t5 when the first on-delay signal Tds1 has changed to high level, as shown in FIG. Becomes 0A, and energization is stopped. At the same time, the filler wire welding voltage Vwf becomes 0V as shown in FIG. Further, as shown in FIG. 4K, the filler wire feed speed Fs is a value determined by the steady-state filler wire feed speed setting signal Fsr, and the feed speed is increased. Thus, welding in a steady period is performed by the consumable electrode arc 3a and the filler wire 1b fed in contact with the latter half of the molten pool.

  Next, the operation will be described. The period from time t1 to t3 is an operation for setting the initial distance to a constant value, as in the prior art. The filler wire 1b is once brought into contact with the base material 2, and the filler wire 1b is fed backward by a predetermined distance therefrom. Since the initial distance is a constant value, the initial distance feeding period from time t5 to t6 is a constant value. As a result, the period from time t4 to t6 can be set to a predetermined value. That is, the time when the filler wire 1b is fed at the time t6 after the consumable electrode arc 3a is generated at the time t4 can be set to a predetermined value. Therefore, the filler wire 1b can be inserted into the molten pool at the moment when the growth of the size of the molten pool becomes the most suitable state for inserting the filler wire 1b. The predetermined distance is, for example, about 2 to 5 mm. This predetermined distance may be set to 0 mm. In this case, the tip of the filler wire 1b is in contact with the base material 2. Further, in the present embodiment, this initial distance setting operation may be omitted. As described above, the initial distance is controlled to be a constant value by the previous welding end control, but has some variation. This fluctuation range is about 10 to 30%. When the fluctuation of the initial distance does not greatly affect the bead quality at the welding start portion, it is not necessary to perform the initial distance setting operation which takes time. In this case, in FIG. 4, the operation is started from time t3. In the welding apparatus, the filler wire feed control circuit FC of FIG. 3 may output the initial distance set signal Lss from the beginning at the High level without performing the initial distance setting operation described in the section 1).

  Unlike the prior art, the filler wire welding current Iwf is supplied to the filler wire 1b during the second predetermined period Td2 from time t5 to t7. As a result, the first predetermined period Td1 between times t4 and t5 can be set shorter than that in the prior art. The reason for this is as follows. This is because melting is assisted by energizing the filler wire 1b, so that even if the filler wire 1b is inserted in a state where the size of the molten pool is smaller than that in the prior art, it can be sufficiently melted. . In the prior art, the first predetermined period Td1 was set to about 0.4 to 0.6 seconds, but in the present embodiment, the first predetermined period Td1 is reduced to about 0.1 to 0.3 seconds by about 0.3 seconds. be able to. The time t7 is a timing at which the filler wire 1b can be melted by the heat from the molten pool without applying a current to the filler wire 1b, and can be said to be the insertion timing of the conventional filler wire 1b. Therefore, the second predetermined period Td2 is set to about 0.3 seconds. It can be said that the sum period of the first predetermined period Td1 and the second predetermined period Td2 is the first predetermined period Td1 in the prior art. Thus, in this embodiment, since the period from the occurrence of the consumable electrode arc 3a to the start of feeding of the filler wire 1b can be shortened, the bead quality at the welding start portion can be improved. Can do. Even if the first predetermined period Td1 is shortened, there is no influence on the consumable electrode arc 3a, so that the arc state such as an increase in the amount of spatter generation and arc breakage does not become unstable. The current value (the value of the initial period filler wire welding current setting signal Isr) that flows through the filler wire 1b varies depending on the material, diameter, and the like of the filler wire 1b, but is set in the range of, for example, about 50 to 150A. The filler wire feeding speed before time t7 is set to be lower than the subsequent value. This is to make it easier to melt the filler wire 1b during the second predetermined period Td2. The same value may be used without changing around time t7. The welding wire feed speed Ws during the steady period is set in a range of about 20 to 30 m / min. The filler wire feed speed Fs during the steady period is set to about 10 to 30% of the welding wire feed speed Ws.

  According to the above-described embodiment, the filler wire is fed by delaying the first predetermined period from the time when the arc is generated between the welding wire and the base metal, and the filler wire is formed by the arc. When contacted with the pond, a predetermined filler wire welding current is supplied, and the supply of the filler wire welding current is stopped when the second predetermined period has elapsed from the start of feeding the filler wire. In this embodiment, since current is supplied to the filler wire to assist melting, melting can be sufficiently melted even if the filler wire is inserted in a state where the size of the molten pool is smaller than in the prior art. it can. For this reason, the first predetermined period can be set shorter than in the prior art. Therefore, in the present embodiment, since the first predetermined period from when the arc is generated to when the filler wire is started to be fed can be shortened, the quality of the bead at the welding start portion can be improved. Further, in this embodiment, since there is no influence on the arc, the arc state such as an increase in the amount of spatter generated and arc breakage does not become unstable.

DESCRIPTION OF SYMBOLS 1a Welding wire 1b Filler wire 2 Base material 2a Molten pool 3a Consumable electrode arc 4a Welding wire feeding tip 4b Filling wire feeding tip 5a Welding wire feeding roll 5b Filler wire feeding roll CD Energization discrimination circuit cd Energization discrimination signal DV drive circuit Dv drive signal EI current error amplification circuit Ei current error amplification signal EV voltage error amplification circuit Ev voltage error amplification signal FC filler wire feed control circuit Fc filler wire feed control signal FIR filler wire feed speed setting for initial period Circuit Fir Initial period filler wire feed speed setting signal FM Filler wire feed motor Fr Filler wire feed speed setting signal Fs Filler wire feed speed FSR Steady period filler wire feed speed setting circuit Fsr Filler wire for steady period Feeding speed setting signal ID Flow detection circuit Id Current detection signal Ifr Filler wire welding current setting signal IIR Contact determination current setting circuit Iir Contact determination current setting signal ISR Filler wire welding current setting circuit Isr for initial period Filler wire welding current setting signal Iwf for initial period Current Iww Welding current Lss Initial distance set signal On Start signal PM Power supply main circuit PSF Welding power source PSW for filler wire Welding power source RC for welding wire Robot controller SD Contact discrimination circuit Sd Contact discrimination signal SI Current switching circuit SW Feeding switching circuit TD1 First on-delay circuit Td1 First predetermined period TD2 Second on-delay circuit Td2 Second predetermined period Tds1 First on-delay signal Tds2 Second on-delay signal VAV Voltage average value calculation circuit Vav Voltage average value signal VD Voltage detection circuit Vd Voltage Detection signal VR Welding voltage setting circuit r Welding voltage setting signal Vwf Filler wire welding voltage Vww Welding voltage WC Welding wire feed control circuit Wc Welding wire feed control signal WIR Slowdown welding wire feed rate setting circuit Wir Slowdown welding wire feed rate setting signal WM Welding wire feeding motor Wr Welding wire feeding speed setting signal Ws Welding wire feeding speed WSR Welding wire feeding speed setting circuit Wsr for steady period Welding wire feeding speed setting signal WT Welding torch

Claims (4)

In the welding start method of two-wire welding, in which an arc is generated between the welding wire and the base material and the filler wire is fed in contact with the latter half of the molten pool formed by the arc,
The feeding of the welding wire is started, the arc is generated between the welding wire and the base material, and the feeding of the filler wire is delayed by a first predetermined period from the time when the arc is generated. When the filler wire comes into contact with the molten pool formed by the arc, a predetermined filler wire welding current is energized, and when the second predetermined period has elapsed from the start of feeding the filler wire, the filler Stop energizing the wire welding current,
A welding start method of two-wire welding characterized by the above. The feeding speed of the filler wire is set to a lower speed before the second predetermined period has elapsed than after the second predetermined period has elapsed,
The welding start method for two-wire welding according to claim 1. Adding a step of feeding until the filler wire comes into contact with the base material before starting feeding the welding wire;
The welding start method for two-wire welding according to claim 1 or 2, wherein the welding is started. Before starting the feeding of the welding wire, the filler wire is fed until it comes into contact with the base material. After the contact, the feeding direction is reversed so that the tip of the filler wire is separated from the base material by a predetermined distance. Add a step to stop feeding by separating
The welding start method for two-wire welding according to claim 1 or 2, wherein the welding is started.

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