JP5706710B2 - 2-wire welding control method - Google Patents

Description

  The present invention relates to a two-wire welding control method in which an arc is generated between a consumable electrode and a base material to form a molten pool, and welding is performed while feeding a filler wire to the molten pool.

  A two-wire welding method in which an arc is generated between a consumable electrode (hereinafter referred to as a welding wire) and a base material to form a molten pool, and a filler wire is fed to the molten pool for welding (see Patent Document 1). ) Is conventionally known. In this two-wire welding method, since the molten metal of the filler wire is added to the molten metal of the welding wire, the amount of the molten metal is increased, and high-speed and high-efficiency welding is possible. In particular, when high-speed welding is performed by the two-wire welding method, it is important to feed the filler wire by short-circuiting it from the rear side of the consumable electrode arc to the molten pool in order to prevent a humping bead. This is because when the filler wire is fed into the consumable electrode arc and melted, the molten pool is hardly cooled and the swell of the latter half of the molten pool cannot be suppressed by the filler wire, thereby suppressing the humping bead. This is because there is no effect. On the other hand, if the filler wire is short-circuited to the rear part of the molten pool at the peripheral edge of the arc and fed and melted by the heat of the molten pool, the molten pool is cooled, and the latter part of the molten pool is filled by the filler wire. Is suppressed, and the formation of a humping bead can be suppressed. Therefore, in the two-wire welding method of the prior art, the molten pool is cooled by short-circuiting the filler wire in a cold state without passing a current through the filler wire.

  In the two-wire welding method, various consumable electrodes such as a carbon dioxide arc welding method, a mag welding method, a MIG welding method, a pulse arc welding method, and an AC arc welding method are used as a method for generating an arc between the welding wire and the base material. A type arc welding process can be used. Further, the filler wire basically has a wire tip short-circuited with the molten pool, and is melted by heat from the molten pool. Therefore, no arc is generated between the filler wire and the molten pool. In this invention, although the case where a pulse arc welding method is used as said consumable electrode type arc welding method is demonstrated, another welding method may be sufficient. Moreover, in the following description, the base material and the molten pool are used in substantially the same meaning.

  FIG. 3 is a current / voltage waveform diagram in the two-wire welding method using pulse arc welding. The figure (A) shows the time change of the welding current Iw which energizes a welding wire, the figure (B) shows the time change of the welding voltage Vw applied between a welding wire and a base material (molten pool), FIG. 5C shows the filler wire feeding speed Fw. Although the welding wire feeding speed is not shown, it is fed at a constant value at a constant speed. No voltage is applied between the filler wire and the molten pool, and no current is applied. As described above, the filler wire is fed in a state of being short-circuited with the molten pool. Even if the filler wire is separated from the molten pool, no voltage is applied, so no arc is generated between the filler wire and the molten pool. Hereinafter, a description will be given with reference to FIG.

  During the peak period Tp from time t1 to t2, a peak current Ip having a large current value equal to or higher than the critical value is energized to transfer droplets from the welding wire as shown in FIG. ), A peak voltage Vp proportional to the arc length is applied between the welding wire and the molten pool.

  During the base period Tb from time t2 to t3, as shown in FIG. 5A, the base current Ib having a small current value less than the critical value is energized in order to prevent the formation of droplets. ), The base voltage Vb is applied. Welding is performed by repeating the period from time t1 to t3 as one period (pulse period Tf).

  During the peak period Tp from time t3 to t4, the same operation as described above is repeated again. During the base period Tb from time t4 to t5, a short circuit between the welding wire and the molten pool occurs during that period. Since the arc is in the period from time t4 to t41, the base current Ib is energized and the base voltage Vb is applied as described above. During the short-circuit period Ts from time t41 to t42, the welding voltage Vw becomes a short-circuit voltage value of several V as shown in FIG. 5B, and the welding current Iw gradually increases as shown in FIG. Short circuit current Is. The reason why the welding current Iw is increased is that the short-circuit state is canceled early and the arc state is restored. In pulse arc welding, this short circuit occurs almost during the base period, and its frequency is about several times per second. In carbon dioxide arc welding, MIG welding, and mag welding, this short circuit occurs several tens of times per second. When the short-circuit state is released and the arc state is restored at time t42, the welding voltage Vw rapidly rises to the base voltage value Vb as shown in FIG. 5B, and welding is performed as shown in FIG. The current Iw shifts from the short-circuit current Is to the base current Ib with a slope. This state continues until time t5 when the next peak period Tp starts.

  On the other hand, as shown in FIG. 5C, the filler wire feed speed Fw is fed at a constant filler wire feed speed Fc in a short-circuited state with the molten pool. The filler wire feed speed Fw does not change at a constant speed even during the short-circuit period Ts. The steady filler wire feeding speed Fc is often set to a range of about 20 to 30% of the welding wire feeding speed in order to melt stably.

  By the way, in order to perform good pulse arc welding, it is important to maintain the arc length at an appropriate value. In order to maintain the arc length at an appropriate value, the following output control (arc length control) of the welding power source is performed. The arc length is substantially proportional to the welding voltage average value Vav indicated by a broken line in FIG. For this purpose, the welding voltage average value Vav is detected, and the output for changing the welding current average value Iav indicated by the broken line in FIG. 5A so that the detected value becomes equal to the welding voltage set value corresponding to the appropriate arc length. Take control. When the welding voltage average value Vav is larger than the welding voltage set value, the arc length is longer than the appropriate value. Therefore, the welding current average value Iav is decreased to reduce the wire melting rate and shorten the arc length. To do. On the other hand, when the welding voltage average value Vav is smaller than the welding voltage set value, the arc length is shorter than the appropriate value, so the welding current average value Iav is increased to increase the wire melting rate and the arc length is increased. Like that. As the welding voltage average value Vav, a value obtained by passing the welding voltage Vw through a low-pass filter (cutoff frequency of about 1 to 10 Hz) is generally used. Further, as an operation amount for changing the welding current average value Iav, changing at least one of the peak period Tp, the pulse period Tf, the peak current Ip, or the base current Ib is performed. For example, when feedback control is performed using the pulse period Tf as an operation amount, the peak period Tp, the peak current Ip, and the base current Ib are set to predetermined values (referred to as a frequency modulation control method). When feedback control is performed using the peak period (pulse width) Tp as an operation amount, the peak current Ip, the base current Ib, and the pulse period Tf are set to predetermined values (referred to as a pulse width modulation control method).

  In the two-wire welding method shown in Patent Document 2, one of the characteristics such as feeding speed, feeding resistance, and vibration generated by feeding the filler wire is detected, and the feeding speed of the filler wire or preheating applied to the filler wire is detected. Control the current. For this reason, it is possible to prevent filler wire unmelted welding defects caused by fluctuations in welding conditions due to disturbances or setting errors in welding conditions, while limiting the heat input to the base material, or maintaining the welding amount and leg length. It is described.

JP 2010-1647489 A JP 2002-28784 A

In the above-described conventional 2-wire welding method, the filler wire is fed in a state of being short-circuited with the molten pool, and the filler wire is melted by the heat of the molten pool. Therefore, the feeding speed of the filler wire is set so as to balance with the speed (melting speed) at which the filler wire is melted by the heat of the molten pool. When the generation state of the arc between the welding wire and the molten pool is stable, the melting of the filler wire is also stable, so that good welding can be performed.

  However, as described above with reference to FIG. 3, when a short circuit occurs between the welding wire and the base material, heating from the arc to the molten pool is lost during the short circuit period Ts, and the temperature of the molten pool decreases. When the short-circuit period Ts is short, the temperature of the molten pool decreases little, so there is almost no influence on the molten state of the filler wire. Therefore, in this case, there is almost no influence on the welding quality. On the other hand, when the short-circuit period Ts is increased, the temperature of the molten pool is greatly decreased, so that the influence on the melting of the filler wire is increased. That is, when the temperature of the molten pool is lowered, the filler wire fed at a constant speed cannot be stably melted. As a result, the filler wire is unstablely repeated from a state where it is stably melted in a short circuit with the molten pool, a state where it is pushed into the molten pool, or a state where it is separated from the molten pool due to its reaction. Deterioration of welding quality such as generation of filler and unmelted filler wire. Furthermore, if the short-circuit period becomes longer and the temperature of the molten pool decreases, the filler wire cannot be melted, and the tip of the filler wire may be welded to the bead and welding may not be continued. Patent Document 2 does not describe anything about the above-described problem caused by a short circuit between the welding wire and the molten pool.

  Therefore, an object of the present invention is to provide a two-wire welding control method that can maintain a stable molten state of a filler wire even if a short circuit between the welding wire and the base material occurs.

In order to solve the above-mentioned problems, the invention of claim 1 is directed to forming a molten pool by generating an arc between the consumable electrode and the base material, and performing welding while feeding a filler wire to the molten pool. In the wire welding control method,
When the consumable electrode and the molten pool are short-circuited and the short-circuit state continues for a predetermined initial period or longer, the filler wire feeding speed is determined in advance from a predetermined steady filler wire feeding speed. Decelerating to a reduced filler wire feed speed, and when the consumable electrode and the molten pool are in an arc state, the filler wire feed speed is returned to the filler wire steady feed speed,
This is a two-wire welding control method.

In the invention of claim 2, the deceleration filler wire feeding speed changes so that its value becomes smaller as time passes.
The two-wire welding control method according to claim 1.

  According to the present invention, the consumable electrode and the molten pool are short-circuited, and when this short-circuit state continues for an initial period or longer, the filler wire feeding speed is reduced to a predetermined deceleration filler wire feeding speed. Let Thereby, even if the temperature of a molten pool falls by a short circuit state, since the feeding speed of a filler wire is decelerated in response to it, the molten state of a filler wire can maintain a stable state. As a result, good welding quality can be obtained.

It is an electric current and voltage waveform diagram which shows the 2 wire welding control method which concerns on embodiment of this invention. It is a block diagram of the welding apparatus for enforcing the 2 wire welding control method concerning an embodiment of the invention. In a prior art, it is an electric current and a voltage waveform diagram in the 2 wire welding method using pulse arc welding.

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

  FIG. 1 is a current / voltage waveform diagram showing a two-wire welding control method according to an embodiment of the present invention. The figure (A) shows the time change of the welding current Iw which energizes a welding wire, the figure (B) shows the time change of the welding voltage Vw applied between a welding wire and a base material (molten pool), FIG. 5C shows the filler wire feeding speed Fw. Although the welding wire feeding speed is not shown, it is fed at a constant value at a constant speed. No voltage is applied between the filler wire and the molten pool, and no current is applied. As described above, the filler wire is fed in a state of being short-circuited with the molten pool. Even if the filler wire is separated from the molten pool, no voltage is applied, so no arc is generated between the filler wire and the molten pool. This figure corresponds to FIG. 3 described above, and is the same except for the operation during the short-circuit period Ts, and a description thereof will be omitted. Hereinafter, the short-circuit period Ts will be described with reference to FIG.

  When the welding wire and the molten pool are short-circuited at time t41, the welding voltage Vw becomes a short-circuit voltage value of several V and enters the short-circuit period Ts as shown in FIG. As shown in FIG. 5A, the welding current Iw becomes a short-circuit current Is that gradually increases when the short-circuit period Ts is entered. As shown in FIG. 5C, the filler wire feed speed Fw remains the steady filler wire feed speed Fc.

  When a predetermined initial period Ti elapses after entering the short-circuit period Ts at time t42, the welding voltage Vw remains the short-circuit voltage value as shown in FIG. Thus, the increase in the short circuit current Is becomes moderate. On the other hand, as shown in FIG. 5C, the filler wire feeding speed Fw is reduced to a predetermined deceleration filler wire feeding speed Fd. At time t43, when the short circuit between the welding wire and the molten pool is released due to the increase of the short circuit current Is and an arc is generated, the welding voltage Vw is a base voltage value of several tens of volts as shown in FIG. The current rapidly rises to Vb, and as shown in FIG. 5A, the welding current Iw decreases with a slope from the short-circuit current Is and shifts to the base current Ib. As shown in FIG. 5C, the filler wire feed speed Fw returns to the steady filler wire feed speed Fc. Thereafter, until the time t5 when the next peak period Tp starts, the welding voltage Vw maintains the base voltage value Vb as shown in FIG. 5B, and the welding current V as shown in FIG. Iw maintains the base current value Ib. As shown in FIG. 5C, the filler wire feed speed Fw also maintains the steady filler wire feed speed Fc.

  In the case of pulse arc welding, as described above, the short circuit occurs several times per second. However, when the arc state is stable, the short circuit is almost short and the filler wire is not melted very much. Does not affect. However, sometimes (about once every few seconds), a long short circuit occurs, affecting the molten state of the filler wire. Even if it is about once every several seconds, if the molten state of the filler wire becomes unstable at that time, the adverse effect on the welding quality is great. When the arc state is somewhat unstable, the proportion of long shorts increases. The initial period Ti is set in a range of about 2 to 7 MS, which is a time at which the temperature drop of the molten pool starts to be affected. This initial period Ti is set to an appropriate value by experiment according to the material of the base material, the welding speed, the joint shape and the like. The deceleration filler wire feed speed Fd is set in a range of about 30 to 70% of the steady filler wire feed speed Fc when it is a constant value. The deceleration filler wire feeding speed Fd is also set to an appropriate value by experiment according to the material of the base material, the welding speed, the joint shape, and the like. The deceleration filler wire feeding speed Fd may be changed so that its value gradually decreases with time.

  As described above, when the short-circuit period Ts continues beyond the initial period Ti, the filler wire feed speed Fw is decreased. Thereby, even if the temperature of a molten pool falls, balance with the feeding speed Fw of a filler wire can be maintained. For this reason, a stable welding state can be maintained. Further, if the deceleration filler wire feed speed Fd is decreased with the passage of time, the molten state of the filler wire can be further stabilized because it can be interlocked with the temperature drop of the molten pool.

  FIG. 2 is a block diagram of a welding apparatus for carrying out the above-described two-wire welding control method according to the embodiment of the present invention. This figure shows the case where the output control (arc length control) is the frequency modulation control described above. 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 a three-phase 200 V as input, performs output control by inverter control according to a drive signal Dv described later, and generates a welding voltage Vw and a welding current Iw for generating the arc 3. Is output. Although not shown, this power main circuit PM is a primary rectifier circuit that rectifies commercial power, a capacitor that smoothes the rectified direct current, and an inverter circuit that converts the smoothed direct current into high frequency alternating current according to the drive signal Dv. And a high-frequency transformer that steps down the high-frequency alternating current to an appropriate voltage value for generating the arc 3, 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 1 is fed through the welding torch 4 by the rotation of the welding wire feeding roll 5 coupled to the welding wire feeding motor WM, and is fed from the power source main circuit PM through a feeding chip (not shown). Electric power is supplied, and an arc 3 is generated between the base material (molten pool) 2. The filler wire 6 is fed through the filler wire guide 7 by the rotation of the filler wire feeding roll 8 coupled to the filler wire feeding motor FM, and is melted in a short-circuited state with the molten pool 2 formed by the arc 3. The In the drawing, the welding torch 4 and the filler wire guide 7 are shown as having different configurations, but two wires (welding wire 1 and filler wire 6) are fed from one welding torch. Anyway.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The voltage smoothing circuit VAV receives the voltage detection signal Vd as an input, averages it (passes through a low-pass filter having a cutoff frequency of about 1 to 10 Hz), and outputs a welding voltage average value signal Vav. The 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 welding voltage average value signal Vav, and outputs a voltage error amplification signal Ev.

  The voltage / frequency conversion circuit VF converts the signal into a signal having a frequency proportional to the value of the voltage error amplification signal Ev, and outputs a pulse period signal Tf having a high level for a short time at each frequency (pulse period). The frequency modulation control described above is performed by this voltage / frequency conversion circuit VF. The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr. The peak period timer circuit TP receives the pulse period signal Tf and the peak period setting signal Tpr as described above, and becomes the High level only for a period determined by the peak period setting signal Tpr from the time when the pulse period signal Tf changes to the High level. The peak period signal Tp is output. Therefore, the peak period signal Tp is a signal whose period is a pulse period, which is at a high level during the peak period and at a low level during the base period.

  The short circuit determination circuit SD receives the voltage detection signal Vd as described above, and outputs a short circuit determination signal Sd which is determined to be in a short circuit state when the value is equal to or less than a predetermined short circuit determination reference value and becomes High level. The initial period setting circuit TIR outputs a predetermined initial period setting signal Tir. The short-circuit late determination circuit SDD receives the short-circuit determination signal Sd and the initial period setting signal Tir, and outputs a short-circuit late determination signal Sdd in which the short-circuit determination signal Sd is on-delayed for a period determined by the initial period setting signal Tir. This short-circuit late determination signal Sdd is a signal that is at a high level only during a period in which the short-circuit period Ts is longer than the initial period Ti (period t42 to t43 in FIG. 1).

  The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr. The base current setting circuit IBR outputs a predetermined base current setting signal Ibr. The arc current setting switching circuit SIA receives the peak period signal Tp, the peak current setting signal Ipr and the base current setting signal Ibr as input, and when the peak period signal Tp is at a high level (peak period), the peak current The setting signal Ipr is output as the arc current setting signal Iar, and when the level is low (base period), the base current setting signal Ibr is output as the arc current setting signal Iar. The short-circuit current setting circuit ISR receives the above-described short-circuit determination signal Sd and outputs a short-circuit current setting signal Isr that gradually increases with the elapsed time from the time when the short-circuit determination signal Sd changes to the high level (short circuit). The current setting switching circuit SI receives the short circuit determination signal Sd, the arc current setting signal Iar, and the short circuit current setting signal Isr. When the short circuit determination signal Sd is at a low level (arc), the arc setting signal Iar is output as the current setting signal Ir, and when the level is High (short circuit), the short circuit current setting signal Isr is output as the current setting signal Ir. The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The current error amplification circuit EI amplifies an error between the current setting signal Ir and the current detection signal Id, and outputs a current error amplification signal Ei. The drive circuit DV receives the current error amplification signal Ei, performs PWM modulation control based on this signal, and based on the result, outputs a drive signal Dv for driving the inverter circuit in the power supply main circuit PM. Output.

  The welding wire feed speed setting circuit WR outputs a predetermined welding wire feed speed setting signal Wr. The welding wire feed control circuit WC supplies the welding wire feed control signal Wc for feeding the welding wire 1 at a feed speed corresponding to the value of the welding wire feed speed setting signal Wr. Output to motor WM. The steady filler wire feed speed setting circuit FCR outputs a predetermined steady filler wire feed speed setting signal Fcr. The deceleration filler wire feed speed setting circuit FDR outputs a predetermined deceleration filler wire feed speed setting signal Fdr. The filler wire feed speed setting switching circuit SF receives the above-described steady filler wire feed speed setting signal Fcr, the above-described deceleration filler wire feed speed setting signal Fdr, and the above-described short-circuit late-stage discrimination signal Sdd as inputs. When Sdd is High level, the deceleration filler wire feed speed setting signal Fdr is output as the filler wire feed speed setting signal Fr. When Sdd is Low level, the steady filler wire feed speed setting signal Fcr is set as the filler wire feed speed setting signal. Output as signal Fr. The filler wire feed control circuit FCT supplies the filler wire feed control signal Fct for feeding the filler wire 6 at a feed rate corresponding to the value of the filler wire feed rate setting signal Fr. Output to the motor FM.

  In the figure, the deceleration filler wire feed speed setting circuit FDR may be changed as follows in order to make the deceleration filler wire feed speed Fd gradually decrease with time. That is, the deceleration filler wire feed speed setting circuit FDR receives the deceleration short-term detection signal Sdd as an input, and the deceleration filler wire feed rate gradually decreases with the lapse of time from the time when the short-circuit late determination signal Sdd changes to the High level. A feed speed setting signal Fdr is output. The figure shows a case where the arc length control is performed by frequency modulation control, but other modulation control such as pulse width modulation control may be used.

  According to the above-described embodiment, when the welding wire and the molten pool are short-circuited and the short-circuit state continues for the initial period or longer, the filler wire feeding speed is reduced to the deceleration filler wire feeding speed. Let Thereby, even if the temperature of a molten pool falls by a short circuit state, since the feeding speed of a filler wire is decelerated in response to it, the molten state of a filler wire can maintain a stable state. As a result, good welding quality can be obtained.

  In the above-described embodiment, the case where the arc is generated by pulse arc welding has been described, but consumable electrode arc welding in general can be used. When the filler wire feeding speed is frequently reduced, the welding conditions (welding wire feeding speed, welding voltage set value, steady filler wire feeding speed, welding speed, filler wire insertion position, etc.) Since it is necessary to re-examine, an alarm may be issued in such a case.

1 Welding wire (consumable electrode)
2 Base material, molten pool 3 Arc 4 Welding torch 5 Welding wire feed roll 6 Filler wire 7 Filler wire guide 8 Filler wire feed roll 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 Steady filler wire feed speed FCR Steady filler wire feed speed setting circuit Fcr Steady filler wire feed speed setting signal FCT Filler wire feed control circuit Fct Filler wire feed control signal Fd Deceleration filler wire feed Feed speed FDR Deceleration filler wire feed speed setting circuit Fdr Deceleration filler wire feed speed setting signal FM Filler wire feed motor Fr Filler wire feed speed setting signal Fw Filler wire feed speed Iar Arc current setting signal Iav Welding current average Value Ib Base current IBR Base current setting circuit Ibr Base current setting signal ID Current detection circuit Id Current detection signal Ip Peak current IPR Peak current setting circuit Ipr Peak current setting signal Ir Current setting signal Is Short circuit current ISR Short circuit current setting circuit Isr Short circuit current setting signal Iw Welding current PM power supply main circuit SD short circuit determination circuit Sd short circuit determination signal SDD short circuit late determination circuit Sdd short circuit late determination signal SF filler wire feed speed setting switching circuit SI current setting switching circuit SIA arc current setting switching circuit Tb base period Tf pulse period (signal )
Ti initial period TIR initial period setting circuit Tir initial period setting signal TP peak period timer circuit Tp peak period (signal)
TPR Peak period setting circuit Tpr Peak period setting signal Ts Short circuit period VAV Voltage smoothing circuit Vav Welding voltage average value (signal)
Vb Base voltage VD Voltage detection circuit Vd Voltage detection signal VF Voltage / frequency conversion circuit Vp Peak voltage VR Voltage setting circuit Vr Welding voltage setting signal vw Welding voltage WC Welding wire feed control circuit Wc Welding wire feed control signal WM Welding wire feed Feed motor WR Welding wire feed speed setting circuit Wr Welding wire feed speed setting signal

Claims (2)

In a two-wire welding control method of generating an arc between a consumable electrode and a base material to form a molten pool and welding while feeding a filler wire to the molten pool,
When the consumable electrode and the molten pool are short-circuited and the short-circuit state continues for a predetermined initial period or longer, the filler wire feeding speed is determined in advance from a predetermined steady filler wire feeding speed. Decelerating to a reduced filler wire feeding speed, and when the consumable electrode and the molten pool are in an arc state, the feeding speed of the filler wire is returned to the steady filler wire feeding speed.
A two-wire welding control method characterized by the above. The deceleration filler wire feeding speed changes so as to decrease its value with the passage of time.
The two-wire welding control method according to claim 1.

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