JP2023062718A - Welding completion control method of pulse arc welding - Google Patents

Abstract

To reduce blow holes which are generated at a welding completion part, in pulse arc welding.SOLUTION: In a welding completion control method of pulse arc welding, in which when a welding completion signal On is inputted to a welding power source, welding currents Iw and welding voltages Vw are controlled so that welding is completed, in an anti-stick period of time Ta during which driving of a feeding motor is stopped and the feeding motor is transiently decelerated and then stopped and the welding is completed, when the welding completion signal On is inputted to the welding power source, the period of time is transferred to an arc-length oscillation period of time Ts during which an arc length is oscillated in a vertical direction, and thereafter the period of time is transferred to the anti-stick period of time Ta. In the arc-length oscillation period of time Ts, pulse currents formed of peak currents in a peak period of time and base currents in a base period of time are distributed and waveform parameters of the pulse currents are periodically switched so as to oscillate the arc length.SELECTED DRAWING: Figure 2

Description

The present invention relates to a welding end control method for pulsed arc welding for reducing blowholes that occur at the end of welding.

The welding wire is fed and the peak current during the peak period and the base current during the base period are alternately and repeatedly energized, and the arc length is cycled by varying the peak period and/or the peak current at the oscillation frequency. An arc length swing pulse arc welding method in which welding is performed by generally swinging in the vertical direction is commonly used (see, for example, Patent Document 1). In this welding method, when the oscillation frequency is set to a low frequency (approximately 20 to 50 Hz), the molten pool is agitated by changes in arc force accompanying oscillation of the arc length, resulting in blow holes and pits (hereinafter collectively referred to as blow holes) can be reduced.

JP 2010-142823 A

In arc length swing pulse arc welding of iron and steel, if the welding speed is increased, it is necessary to set the average arc length short in order to prevent bead appearance defects such as undercuts. If the average arc length is shortened, there is a problem that a short circuit occurs during a long period of low arc and a large amount of spatter is generated. For this reason, when the welding speed is faster than about 80 cm/min, arc length oscillation pulse arc welding is often not applied. On the other hand, when ordinary pulse arc welding is used, there is a problem that blowholes are likely to occur at the end of welding.

Therefore, the present invention provides a welding end control method for pulse arc welding that can reduce the occurrence of spatter during the steady welding period and reduce the blowholes that occur at the end of welding even if the welding speed is increased. intended to provide

In order to solve the above-mentioned problems, the invention of claim 1 is
When a welding end signal is input to the welding power source, the feed motor stops driving, and the welding current and welding current are maintained during the anti-stick period until the feed motor stops due to transient deceleration due to inertia and welding ends. In a pulse arc welding welding termination control method for controlling welding voltage to terminate welding,
When the welding end signal is input, the arc length swing period shifts to the arc length swinging direction, and then shifts to the anti-stick period.
A welding end control method for pulse arc welding characterized by:

The invention of claim 2 is
During the arc length fluctuation period, a pulse current formed from the peak current during the peak period and the base current during the base period is applied, and the arc length is oscillated by periodically switching the waveform parameters of the pulse current. ,
The welding end control method for pulse arc welding according to claim 1, characterized in that:

The invention of claim 3 is
wherein the waveform parameter is the peak period and/or the peak current;
The welding end control method for pulse arc welding according to claim 2, characterized in that:

The invention of claim 4 is
When a crater period is provided before the anti-stick period, the crater period is the arc length oscillation period,
The welding end control method for pulse arc welding according to any one of claims 1 to 3, characterized in that:

According to the welding end control method of pulse arc welding according to the present invention, even if the welding speed is increased, it is possible to reduce the occurrence of spatter during the steady welding period and reduce the blowholes generated at the welding end portion. can.

1 is a block diagram of a welding power source PS for implementing a welding end control method for pulse arc welding according to an embodiment of the present invention; FIG. 2 is a timing chart of each signal in the welding power source of FIG. 1, showing the welding end control method for pulse arc welding according to the embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a welding power supply PS for implementing a welding end control method for pulse arc welding according to an embodiment of the present invention. Each block will be described below with reference to FIG.

The power supply main circuit PM receives a commercial power supply (not shown) such as 3-phase 200 V, and performs output control such as inverter control according to a drive signal Dv described later to set the welding voltage Vw and welding current Iw suitable for arc welding. Output. Although not shown, the power supply main circuit PM is driven by a primary rectifier circuit that rectifies commercial power, a capacitor that smoothes the rectified direct current, and the drive signal Dv that converts the smoothed direct current into high-frequency alternating current. It has an inverter circuit, a high-frequency transformer that steps down high-frequency alternating current to a voltage value suitable for arc welding, a secondary rectifier circuit that rectifies the stepped-down high-frequency alternating current to direct current, and a reactor that smoothes the rectified direct current.

Welding wire 1 is fed through welding torch 4 by rotation of feed roll 5 coupled to feed motor M, and arc 3 is generated between work 2 and welding wire 1 . A welding voltage Vw is applied between the welding wire 1 and the workpiece 2, and a welding current Iw is applied. Shielding gas (not shown) is jetted out from the tip of the welding torch 4 . The shield gas is argon gas, a mixed gas of argon gas and carbon dioxide, a mixed gas of argon gas and oxygen, or the like. The shield gas is a gas containing at least an inert gas in order to transfer the droplets by energizing the pulse current.

The welding start/end circuit ON outputs a welding start/end signal On that becomes High level (welding start signal) when welding is started and becomes Low level (welding end signal) when welding is ended. This circuit is a switch attached to the welding torch 4 . Also, this circuit is built into the robot controller in the case of robot welding.

A welding current setting circuit IR outputs a predetermined welding current setting signal Ir.

A feeding speed setting circuit FR receives the welding current setting signal Ir and outputs a feeding speed setting signal Fr calculated by a predetermined current/feeding speed conversion function.

A feed control circuit FC receives the feed speed setting signal Fr and a switching control signal Sc, which will be described later. feeds the welding wire 1 at the feed speed Fw set by the feed speed setting signal Fr, and stops the feed motor M when the switching control signal Sc changes to 3 (anti-stick period Ta). It outputs a control signal Fc. In the anti-stick period Ta, the feeding speed Fw gradually decelerates and stops due to inertia.

The feeding motor M has its rotation speed controlled by the feeding control signal Fc, and feeds the welding wire 1 at the feeding speed Fw.

An arc length swing period setting circuit TSR outputs a predetermined arc length swing period setting signal Tsr.

The switching control circuit SC receives the welding start/end signal On and the arc length oscillation period setting signal Tsr, performs the following processing, and outputs a switching control signal Sc.
1) When the welding start/end signal On is at the High level (start of welding), it is the steady welding period Tc, and the switching control signal Sc=1 is output.
2) When the welding start/end signal On changes to Low level (welding end), the arc length oscillation period Ts set by the arc length oscillation period setting signal Tsr is entered, and the switching control signal Sc=2 is output. .
3) When the arc long swing period Ts ends, it shifts to the anti-stick period Ta and outputs the switching control signal Sc=3.

A voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. A voltage average value calculation circuit VAV calculates an average value (smoothed value) of the voltage detection signal Vd and outputs a voltage average value signal Vav. The voltage setting circuit VR outputs a predetermined voltage setting signal Vr. A voltage error amplification circuit EV amplifies an error between the voltage setting signal Vr and the voltage average value signal Vav, and outputs a voltage error amplification signal Ev.

A voltage/frequency conversion circuit VF receives the voltage error amplification signal Ev as an input and outputs a pulse cycle signal Tf having a frequency proportional to the value of this signal. That is, the pulse cycle signal Tf is a signal that goes high for a short period of time every pulse cycle.

The peak period setting circuit TPR receives the switching control signal Sc, performs the following processing, and outputs a peak period setting signal Tpr.
1) When the switching control signal Sc=1 (regular welding period Tc), the peak period setting signal Tpr for a predetermined stationary peak period is output.
2) When the switching control signal Sc=2 (arc length oscillation period Ts), a peak period setting signal Tpr is output which repeats a predetermined high peak period and a predetermined low peak period at a predetermined oscillation period. do.

The peak period timer circuit TP receives the peak period setting signal Tpr and the pulse period signal Tf, and keeps the pulse period signal Tf at High level for a period determined by the peak period setting signal Tpr after the pulse period signal Tf changes to High level for a short period of time. , and outputs a peak period signal Tp that is at Low level during other periods. Therefore, this peak period signal Tp is a signal that is at High level during the peak period and is at Low level during the base period.

The peak current setting circuit IPR receives the switching control signal Sc, performs the following processing, and outputs a peak current setting signal Ipr.
1) When the switching control signal Sc=1 (steady welding period Tc), the peak current setting signal Ipr that becomes a predetermined steady peak current is output.
2) When the switching control signal Sc=2 (arc length oscillation period Ts), output a peak current setting signal Ipr that repeats a predetermined high peak current and a predetermined low peak current at a predetermined oscillation period. do.

A base current setting circuit IBR outputs a predetermined base current setting signal Ibr.

The anti-stick current setting circuit IAR receives the switching control signal Sc as an input, changes the switching control signal Sc to 3, and shifts to the anti-stick period Ta. Outputs an anti-stick current setting signal Iar that repeats the peak current and a predetermined anti-stick base current during a predetermined anti-stick base period for a predetermined number of times as one cycle, and outputs a stop signal that goes high for a short time after the repetition is completed. Outputs Off.

The current control setting circuit ICR receives the peak period signal Tp, the peak current setting signal Ipr, the base current setting signal Ibr, the anti-stick current setting signal Iar, and the switching control signal Sc, and performs the following operations. and outputs the current control setting signal Icr.
1) When the switching control signal Sc=1 (steady welding period Tc) or 2 (arc length oscillation period Ts), when the peak period signal Tp becomes High level, it becomes the peak current setting signal Ipr, and when it becomes Low level, the base current It outputs a current control setting signal Icr that becomes the setting signal Ibr.
2) When the switching control signal Sc=3 (anti-stick period Ta), the anti-stick current setting signal Iar is output as the current control setting signal Icr.

A welding current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. A current error amplification circuit EI amplifies the error between the current control setting signal Icr and the welding current detection signal Id, and outputs a current error amplification signal Ei.

A drive circuit DV receives the welding start/end signal On, the stop signal Off, and the current error amplification signal Ei as inputs, and the stop signal Off is shorted from the time when the welding start/end signal On changes to High level. During the period until it changes to the high level, PWM modulation control is performed based on the current error amplification signal Ei, and the drive signal Dv is output. Therefore, the welding power source PS outputs the welding voltage Vw and the welding current Iw during the steady welding period Tc, the arc length oscillation period Ts, and the anti-stick period Ta.

FIG. 2 is a timing chart of each signal in the welding power source of FIG. 1 showing the welding end control method for pulse arc welding according to the embodiment of the present invention. (A) shows the change over time of the welding start/end signal On, (B) shows the change over time of the feed speed Fw, and (C) shows the change over time of the welding current Iw. (D) shows the time change of the welding voltage Vw, (E) shows the time change of the switching control signal Sc, and (F) shows the time change of the stop signal OFF. The operation of each signal will be described below with reference to FIG.

As shown in (E) of the same figure, the period before time t1 becomes the switching control signal Sc=1 and becomes the steady welding period Tc, and the period from time t1 to t2 becomes the switching control signal Sc=2 and becomes the arc length oscillation period Ts. , the period from time t2 to t3 becomes the switching control signal Sc=3 and becomes the anti-stick period Ta.

(1) Operation of the steady welding period Tc before time t1 As shown in (A) of the same figure, the welding start/end signal On is at a high level (start of welding), and as shown in (E) of the same figure, switching The control signal Sc becomes 1, and the steady welding period Tc is reached. As shown in FIG. 1B, the feeding speed Fw is a constant value set by the feeding speed setting signal Fr in FIG. As shown in (C) of the figure, the welding current Iw is a pulse current formed from the peak current during the peak period and the base current during the base period. The peak period is the stationary peak period set by the peak period setting signal Tpr in FIG. 1, and the peak current is the stationary peak current set by the peak current setting signal Ipr in FIG. The base current is set by the base current setting signal Ibr of FIG. The steady peak period and steady peak current are set so that one pulse period and one droplet transfer state occur. As shown in (D) of the figure, the welding voltage Vw becomes a peak voltage proportional to the arc length during the peak period, and becomes a base voltage proportional to the arc length during the base period. The pulse period is feedback-controlled so that the average value of the welding voltage Vw becomes equal to the value of the voltage setting signal Vr shown in FIG. 1, thereby maintaining the arc length at an appropriate value. As shown in (F) of the figure, the stop signal Off remains at the Low level. For example, steady peak period = 1.2 ms, steady peak current = 450 A, base current = 50 A, pulse period = about 5 ms.

(2) Operation of the arc length oscillation period Ts from time t1 to t2 As shown in (A) of the same figure, when the welding start/end signal On becomes Low level (end of welding), as shown in (E) of the same figure Then, the switching control signal Sc becomes 2 and the arc length oscillation period Ts. The arc length swing period Ts is set by the arc length swing period setting signal Tsr shown in FIG. As shown in FIG. 1B, the feeding speed Fw is a constant value set by the feeding speed setting signal Fr in FIG. This value may be set to a value different from the steady welding period Tc. Also, this value may be switched between a high feeding speed and a low feeding speed in accordance with the oscillation period. As shown in FIG. 4C, the welding current Iw is such that the waveform parameters of the pulse current are switched at a predetermined oscillation period formed from a predetermined high arc long period and a predetermined low arc long period. During the high arc long period, a pulse current formed from a predetermined high peak current during the predetermined high peak period and a predetermined base current during the base period is energized for a plurality of cycles. During the low arc long period, a pulse current formed from a predetermined low peak current during the predetermined low peak period and a predetermined base current during the base period is energized for a plurality of cycles. The high peak period and low peak period are set by the peak period setting signal Tpr of FIG. The high peak current and low peak current are set by the peak current setting signal Ipr of FIG. The base current is set by the base current setting signal Ibr of FIG. The high peak period and high peak current and the low peak period and low peak current are set to provide one pulse period and one droplet transfer state. As shown in (D) of the figure, the welding voltage Vw has a waveform proportional to the arc length similar to the welding current Iw. As in the steady welding period, the pulse period is feedback-controlled so that the average value of the welding voltage Vw becomes equal to the value of the voltage setting signal Vr in FIG. 1, thereby maintaining the arc length at an appropriate value. As shown in (F) of the figure, the stop signal Off remains at the Low level. The arc length oscillation period Ts is a period in which the molten pool is agitated with the arc length oscillation and the gas is released to the outside. ~50 Hz). For example, the ratio of high arc duration and low arc duration = 50%. Here, since the pulse period is about 5 ms, the high arc long period and the low arc long period include 2 to 5 periods. Also, high peak period=2.0ms, high peak current=500A, low peak period=1.2ms, low peak current=450A. The above is the case where the peak period and the peak current are changed as waveform parameters in order to fluctuate the arc length. Alternatively, at least one of the peak period, peak current, and pulse period may be changed.

(3) Operation during the anti-stick period Ta from time t2 to t3 When the arc length fluctuation period Ts ends at time t2, the switching control signal Sc becomes 3 as shown in FIG. Become. In response to this, the feeding motor M in FIG. 1 shifts to a stop operation, and as shown in FIG. As shown in FIG. 4C, the welding current Iw is formed from a predetermined anti-stick peak current during a predetermined anti-stick peak period and a predetermined anti-stick base current during a predetermined anti-stick base period. A predetermined number of times is repeated with the pulse current applied as one cycle. Each of these waveform parameters is set by the anti-stick current setting signal Iar in FIG. As shown in (D) of the figure, the welding voltage Iw has a waveform proportional to the arc length similar to the welding current Iw. Feedback control based on the welding voltage average value is not performed during the anti-stick period Ta, but feedback control may be performed. For example, anti-stick period=100 ms, anti-stick peak period=1.2 ms, anti-stick peak current=450 A, anti-stick base period=8 ms, anti-stick base current=40 A, predetermined number of times=10.

At time t3, when the application of the pulse current for a predetermined number of times is completed, the stop signal Off goes high for a short period of time as shown in FIG. In response to this, the welding power source stops outputting, so the welding current Iw becomes 0A as shown in FIG. 1C and the welding voltage Vw becomes 0V as shown in FIG. 1D. In the figure, the time t3 is just before the time t4 when the inertia period of the feeding speed Fw ends, but it may be just after the time t4. Time t3 is near time t4.

The effects of this embodiment will be described below.
According to the present embodiment described above, when the welding end signal is input, the arc length swing period is entered in which the arc length is swung in the vertical direction, and then the anti-stick period is entered. In the arc long swing period, a pulse current formed from the peak current during the peak period and the base current during the base period is applied, and the arc is formed by periodically switching the waveform parameters of the pulse current at a predetermined swing period. Oscillate length. Waveform parameters are peak duration and/or peak current. In the case of welding iron and steel by the conventional long arc oscillation pulse arc welding, there is a problem that when the welding speed is as high as 80 cm/min or more, the amount of spatter increases and the appearance of the bead tends to deteriorate. On the other hand, in ordinary pulse arc welding, although the amount of spatter generated is small and the bead appearance is good, there is a problem that blowholes are likely to occur at the end of welding. The above problem becomes significant when welding galvanized steel sheets. In contrast, in the present embodiment, an arc length swing period is provided before entering the anti-stick period. Since the arc length is oscillated during the arc length oscillation period, the molten pool is agitated. Due to this action, the gas inside the molten pool is released to the outside, so the occurrence of blowholes can be suppressed. As a result, it is possible to improve the welding quality of the welding end portion.

More preferably, according to the present embodiment, when a crater period is provided before the anti-stick period, the crater period is set as the arc long swing period. In this way, during the crater period, the crater treatment and arc long swing operation can be performed simultaneously. As a result, it is possible to suppress the occurrence of blowholes at the end of welding and shorten the tact time.

In the embodiment described above, pulse arc welding is performed during the steady welding period, but DC consumable electrode arc welding may be performed. Also in this case, the arc length fluctuation period may be provided before the anti-stick period.

1 Welding wire 2 Workpiece 3 Arc 4 Welding torch 5 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 Feed control circuit Fc Feed control signal FR feeding speed setting circuit Fr feeding speed setting signal Fw feeding speed IAR anti-stick current setting circuit Iar anti-stick current setting signal IBR base current setting circuit Ibr base current setting signal ID welding current detection circuit Id welding current detection signal IPR peak Current setting circuit Ipr Peak current setting signal IR Welding current setting circuit Ir Welding current setting signal Iw Welding current M Feed motor OFF Stop signal ON Welding start/end circuit ON Welding start/end signal PM Power supply main circuit PS Welding power source SC Switching control Circuit Sc Switching control signal Ta Anti-stick period Tc Steady welding period Tf Pulse period signal TP Peak period timer circuit Tp Peak period signal TPR Peak period setting circuit Tpr Peak period setting signal Ts Arc length swing period TSR Arc length swing period setting circuit Tsr Arc length oscillation period setting signal VAV Voltage average value calculation circuit Vav Voltage average value signal VD Voltage detection circuit Vd Voltage detection signal VF Voltage/frequency conversion circuit VR Voltage setting circuit Vr Voltage setting signal Vw Welding voltage

Claims (4)

When a welding end signal is input to the welding power source, the feed motor stops driving, and the welding current and welding current are maintained during the anti-stick period until the feed motor stops due to transient deceleration due to inertia and welding ends. In a pulse arc welding welding termination control method for controlling welding voltage to terminate welding,
When the welding end signal is input, the arc length swing period shifts to the arc length swinging direction, and then shifts to the anti-stick period.
A welding end control method for pulse arc welding, characterized by: During the arc length fluctuation period, a pulse current formed from the peak current during the peak period and the base current during the base period is applied, and the arc length is oscillated by periodically switching the waveform parameters of the pulse current. ,
The welding end control method for pulse arc welding according to claim 1, characterized in that: wherein the waveform parameter is the peak period and/or the peak current;
The welding end control method for pulse arc welding according to claim 2, characterized in that: When a crater period is provided before the anti-stick period, the crater period is the arc length oscillation period,
The welding end control method for pulse arc welding according to any one of claims 1 to 3, characterized in that:

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