JP5898444B2 - Welding start method of 2-wire welding - Google Patents

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 first 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
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,
A filler wire moving mechanism that automatically adjusts the distance between the welding wire and the filler wire by moving the insertion position of the filler wire in the front-rear direction of the welding direction;
The filler wire moving mechanism sets the inter-wire distance to a predetermined inter-wire distance for a start period, starts feeding the welding wire, generates the arc between the base material, and the arc The filler wire is fed after being delayed by a first predetermined period from the time of occurrence, and the inter-wire distance is measured by the filler wire moving mechanism when a second predetermined period has elapsed from the feeding start time of the filler wire. Is automatically adjusted to a predetermined stationary period inter-wire distance that is longer than the start period inter-wire distance,
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. 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 inter-wire distance between the welding wire and the filler wire is set to a predetermined inter-wire distance for the start period, and feeding the welding wire is started to generate an arc between the base material, The filler wire feed is started after a delay of the first predetermined period from the time when the arc is generated, and the inter-wire distance is set for the start period when the second predetermined period has elapsed from the feed start time of the filler wire. The distance is changed to a predetermined steady-state inter-wire distance that is longer than the inter-wire distance. In the present invention, during the start period, the distance between the wires is shorter than the steady period, so that the filler wire is melted, and the filler wire is inserted in a state where the size of the molten pool is smaller than that in the prior art. 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. It is a block diagram of welding power supply PS which comprises the welding apparatus mentioned above in FIG. 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. It is a figure which shows the welding part of the period of the time t6-t7 of FIG. 3 in a start period.

  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, a welding power source PS, a robot control device RC, and a robot (not shown) surrounded by a broken line. The welding torch WT includes a power feed tip 4a for feeding power to the welding wire 1a, a feed guide 4b for guiding the filler wire 1b to the insertion position, and a filler wire moving mechanism 6. The filler wire moving mechanism 6 receives a wire and an inter-distance setting signal Lwr, which will be described later, and moves the insertion position of the filler wire 1b in the front-rear direction of the welding direction according to the value of the setting signal Lwr to set the inter-wire distance Lw. It is a mechanism that includes a motor that automatically adjusts. Conventionally, a mechanism for converting the rotational motion of the motor into a linear motion by a slider crank mechanism, a mechanism for converting the rotational motion of the motor into a swinging motion by a crank and a swing rod, and the like are used. A shield gas (not shown) such as carbon dioxide, a mixed gas of carbon dioxide and argon gas is ejected from the tip of the welding torch WT. 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 at the filler wire feed speed Fs in the feed guide 4b by the rotation of the filler wire feed roll 5b coupled to the filler wire feed motor FM, and the latter half of the molten pool 2a. Inserted in contact with the. The welded part in the figure shows a state in a steady period. The welded part in the start period will be described later with reference to FIG.

  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. No voltage is applied between the filler wire 1b and the base material 2, and no current is applied. 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 out of the generating part of 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.

  A center line indicating the feeding direction of the welding wire 1a is indicated by a one-dot chain line, and a point where the center line intersects the surface of the base material 2 is a welding target position a. The insertion position of the filler wire 1b is the stationary period insertion position b. The stationary period insertion position b is set in a range behind the generating part of the consumable electrode arc 3a and ahead of the rear end of the molten pool 2a. The distance between the welding target position a and the stationary period insertion position b is the inter-wire distance Lw (mm). This inter-wire distance Lw is set by the inter-wire distance setting signal Lwr as described above.

  The welding power source PS 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 power supply tip 4a. From the welding power source PS, a welding wire feed control signal Wc is sent to the welding wire feed motor WM, the welding wire feed speed Ws is controlled, and a filler is fed to the filler wire feed motor FM. A wire feed control signal Fc is sent to control the filler wire feed speed Fs. Further, the welding power source PS outputs the inter-wire distance setting signal Lwr for setting the inter-wire distance Lw between the welding wire 1a and the filler wire 1b to the filler wire moving mechanism 6. When the welding voltage Vww is applied from the welding power source PS via the power feed tip 4a, the welding wire 1a is set to the + side. The welding power source PS 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 robot controller RC outputs an activation signal On to the welding power source PS, and an energization determination signal Cd is input from the welding power source PS. 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 supplying the welding current Iww. 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, the activation signal On is output to the welding power source PS. 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.

  FIG. 2 is a block diagram of a welding power source PS 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 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 feeding tip 4a by the rotation of the welding wire feeding roll 5a coupled to the welding wire feeding motor WM, and is consumable electrode arc 3a between the base metal 2 and the welding wire 1a. Will occur. The filler wire 1b is fed through the feed guide 4b by the rotation of the filler wire feed roll 5b coupled to the filler wire feed motor FM, and is inserted into the molten pool. The filler wire moving mechanism 6 adjusts the insertion position of the filler wire 1b. 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, an initial distance set signal Lss, which will be described later, and a start signal On 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). Is completed), 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. As a result, the welding power source PS starts outputting.

  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 determines an energization determination signal Cd that becomes a high level, which will be described later. Output to the feed switching circuit SW, the first on-delay circuit TD1 and the robot controller RC, which will be described later. The threshold value is set to about 5A, for example. Thereby, generation | occurrence | production of the consumable electrode arc 3a is discriminate | determined.

  The slowdown welding wire feed speed setting circuit WIR outputs a predetermined slowdown welding wire feed speed setting signal Wir. The steady period welding wire feed speed setting circuit WSR outputs a predetermined steady period welding wire feed speed setting signal Wsr. The feed switching circuit SW receives the slowdown welding wire feed rate setting signal Wir, the steady period welding wire feed rate setting signal Wsr, and the energization discrimination signal Cd as inputs. 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, an initial distance set signal Lss, which will be described later, and a start signal On from the robot controller RC, and receives the start signal On and the initial distance set signal Lss. When both are at the High level (start-up and completion of setting), 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 welding wire feed described above. Output to the feed motor WM.

  The first on-delay circuit TD1 receives the energization determination signal Cd as described above and delays the time when the energization determination signal Cd changes to a high level (energization) by a first predetermined period Td1 to generate a first 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 start period inter-wire distance setting circuit LIR outputs a predetermined start period inter-wire distance setting signal Lir. The stationary period inter-wire distance setting circuit LSR outputs a predetermined stationary period inter-wire distance setting signal Lsr. The distance switching circuit SL receives the start period inter-wire distance setting signal Lir, the stationary period inter-wire distance setting signal Lsr, and the second on-delay signal Tds2, and the second on-delay signal Tds2 is Low. When it is at the level, the inter-wire distance setting signal Lir for the start period is output to the filler wire moving mechanism 6 as the inter-wire distance setting signal Lwr, and when it is at the High level, the inter-wire distance setting signal Lsr for the steady period is output. The setting signal Lwr is output to the filler wire moving mechanism 6 described above.

  The start period filler wire feed speed setting circuit FIR outputs a predetermined start period filler wire feed speed setting signal Fir. The regular period filler wire feed speed setting circuit FSR outputs a predetermined steady period filler wire feed speed setting signal Fsr. The second feed switching circuit SW2 receives the start period filler wire feed speed setting signal Fir, the steady period filler wire feed speed setting signal Fsr, and the second on-delay signal Tds2 as inputs. When the 2-on delay signal Tds2 is at the Low level, the filler wire feed speed setting signal Fir for the start period is output as the filler wire feed speed setting signal Fr, and when it is at the High level, the filler wire feed speed setting signal for the steady period is output. Fsr is output as a filler wire feed speed setting signal Fr.

The filler wire feed control circuit FC receives the start signal On from the robot controller RC, the filler wire feed speed setting signal Fr and the first on-delay signal Tds1 as input, and performs the following processing to obtain an initial distance. A set signal Lss is output, and a 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 it is determined that the filler wire 1b is in contact with the base material 2 because the current value for energizing the filler wire feed motor FM is equal to or greater than the threshold value, the filler wire 1b is fed back for a predetermined reverse feed period. Then, a filler wire feed control signal Fc for stopping 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 start 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.

  In the above, contact determination is performed using the fact that when the filler wire 1b contacts the base material 2, the motor torque increases and the motor current value increases. In addition to this, there is a method in which a contact determination voltage is applied between the filler wire 1b and the base material 2 and contact is determined by energization of current or voltage drop. At this time, in order not to generate an arc in the filler wire 1b, the contact determination voltage value or the current value is set to a small value.

  FIG. 3 is a timing chart of each signal in FIGS. 1 to 2 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 the time change of the first on-delay signal Tds1, FIG. 11H shows the time change of the second on-delay signal Tds2, FIG. 11I shows the time change of the filler wire feed speed Fs, FIG. 6J shows the change over time in the inter-wire distance Lw. Hereinafter, a description will be given with reference to FIG. No voltage is applied to the filler wire 1b, and no current is applied. Therefore, no arc is generated in the filler wire 1b.

(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 start signal On changes to the high level, as shown in FIG. 5I, the filler wire feed speed Fs becomes a value determined by the positive start period filler wire feed speed setting signal Fir. Feeding of 1b is started. When it is determined by the above-described method that the filler wire 1b is in contact with the base material 2 at time t2, the filler wire feed speed Fs is a negative value for the start period filler wire feed as shown in FIG. The value is determined by the speed setting signal Fir, and the filler wire 1b starts reverse feeding. Then, at time t3 when a predetermined reverse feed period has elapsed from time t2, the filler wire feed speed Fs becomes 0, as shown in FIG. In response to this, the initial distance set signal Lss changes to the high level as shown in FIG. As shown in FIG. 6J, the inter-wire distance Lw is a value determined by the start period inter-wire distance setting signal Lir because the second on-delay signal Tds2 shown in FIG. ing. That is, the distance between the wires is shorter than the steady period. Thereby, the initial distance setting operation is completed. During the period from the time t1 to the time t3, since the output of the welding power source PS is in a stopped state, the energization determination signal Cd is at the low level as shown in FIG. In addition, the welding voltage Vww is 0 V, the welding wire feed speed Ws is 0 as shown in FIG. 5E, and the welding current Iww is 0 A as shown in FIG. During this period, the first on-delay signal Tds1 is at the low level as shown in FIG. 5G, and the second on-delay signal Tds2 is at the low level as shown in FIG. . Further, as shown in FIG. 5I, the filler wire feed speed Fs during the period from the time t3 to the time t5 is 0 because it is stopped.

(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. 5I, the filler wire feed speed Fs becomes a value determined by the start 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 1b is melted while maintaining the contact state by heat from the molten pool. As shown in FIG. 10J, the inter-wire distance Lw at this time is determined by the start period inter-wire distance setting signal Lir because the second on-delay signal Tds2 shown in FIG. It becomes a fixed value. That is, the value is shorter than the steady period. For this reason, since it approaches the consumable electrode arc 3a, melting of the filler wire 1b is promoted. 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 Td2 has elapsed from time t5 when the first on-delay signal Tds1 has changed to High level, as shown in FIG. Increases to a value determined by the wire interval setting signal Lsr for the steady period. In response to this, as shown in FIG. 4I, the filler wire feed speed Fs becomes a value determined by the filler wire feed speed setting signal Fsr for the steady period, and the feed speed becomes faster. As a result, the inter-wire distance Lw becomes a long value for the steady period, and welding in the 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.

  FIG. 4 is a diagram showing a welded part in the period from time t6 to t7 in FIG. 3 in the start period. This corresponds to the welded part during the steady period in FIG. 1 described above. Hereinafter, a description will be given with reference to FIG.

  During this period, the welding torch WT is moving in the welding direction. 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 at the filler wire feed speed Fs in the feed guide 4b by the rotation of the filler wire feed roll 5b coupled to the filler wire feed motor FM, and the start period insertion position c. Has been inserted. No voltage is applied between the filler wire 1b and the base material 2, and no current is passed through the filler wire 1b. The filler wire 1b is fed at a filler wire feeding speed Fs for the start period. The start period insertion position c is set at a position closer to the welding target position a than the steady period insertion position b (front position). The inter-wire distance Lw, which is the distance between the welding target position a and the insertion position of the filler wire 1b, is the distance between a and c during the start period and the distance between a and b during the steady period. Therefore, the inter-wire distance Lw is shorter during the start period than during the steady period. The start period insertion position c is set to approach the consumable electrode 3a. This is to promote melting of the filler wire 1b. For this reason, the front-end | tip of the filler wire 1b will be in a contact state and / or a non-contact state with the molten pool 2a. The biggest difference between the start period and the steady period is the distance between the wires Lw. The inter-wire distance Lw during the steady period is set to about 3 to 7 mm, for example, and the inter-wire distance Lw during the start period is set to be about 2 to 3 mm shorter than that.

  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. 3, the operation starts from time t3. In the welding apparatus, the filler wire feed control circuit FC of FIG. 2 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 inter-wire distance Lw is set to a value shorter than the steady period until the time t7 when the second predetermined period Td2 elapses after the filler wire feed is started. 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. By setting the inter-wire distance Lw to be short, the filler wire 1b approaches the consumable electrode arc 3a, so that melting is promoted, and the filler wire 1b is inserted in a state where the size of the molten pool is smaller than in the prior art. This is because 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. Time t7 is a timing at which the filler wire 1b can be melted by the heat from the molten pool even if the distance between the wires is increased for a steady period, and is the insertion timing of the filler wire 1b of the prior art. It can also be said. 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 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 10 to 20 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 distance between the welding wire and the filler wire is set to a predetermined distance between the wires for the start period, the feeding of the welding wire is started, and an arc is formed between the base material and the welding wire. The filler wire is fed after being delayed by a first predetermined period from the time when the arc is generated, and the inter-wire distance is set at the time when the second predetermined period has elapsed from the feeding start time of the filler wire. The distance is changed to a predetermined steady-period inter-wire distance that is longer than the start-period inter-wire distance. In the present embodiment, during the start period, the distance between the wires is shorter than the steady period, so that the filler wire is melted and the filler wire is inserted in a state where the size of the molten pool is smaller than that in the prior art. Even so, it can be sufficiently melted. 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 Feed tip 4b Feeding guide 5a Welding wire feeding roll 5b Filler wire feeding roll 6 Filler wire moving mechanism a Welding target position b For steady period Insertion position c Start position insertion position CD Energization determination circuit Cd Energization determination signal DV Drive circuit Dv Drive signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC Filler wire feed control circuit Fc Filler wire feed control signal FIR For start period Filler wire feed speed setting circuit Fir Start 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 Filler wire feed speed setting circuit for steady period Fsr Filler Y for stationary period Feed speed setting signal ID Current detection circuit Id Current detection signal Iww Welding current LIR Start interval wire distance setting circuit Lir Start interval wire distance setting signal LSR Steady period wire distance setting circuit Lsr Steady period wire distance Setting signal Lss Initial distance setting signal Lw Distance between wires Lwr Distance between wires setting signal On Activation signal PM Power supply main circuit PS Welding power supply RC Robot controller SL Distance switching circuit SW Feeding switching circuit SW2 Second 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 Vr welding voltage setting signal Vww welding voltage WC welding Y feed control circuit Wc Welding wire feed control signal WIR Welding wire feed speed setting circuit Wir Slow down welding wire feed speed setting signal WM Welding wire feed motor Wr Welding wire feed speed setting signal Ws Welding wire feed speed WSR Welding wire feed speed setting circuit Wsr for steady period Welding wire feed speed setting signal WT Welding torch for steady period

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,
A filler wire moving mechanism that automatically adjusts the distance between the welding wire and the filler wire by moving the insertion position of the filler wire in the front-rear direction of the welding direction;
The filler wire moving mechanism sets the inter-wire distance to a predetermined inter-wire distance for a start period, starts feeding the welding wire, generates the arc between the base material, and the arc The filler wire is fed after being delayed by a first predetermined period from the time of occurrence, and the inter-wire distance is measured by the filler wire moving mechanism when a second predetermined period has elapsed from the feeding start time of the filler wire. Is automatically adjusted to a predetermined stationary period inter-wire distance that is longer than the start period inter-wire distance,
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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