JP2024069805A - Pulse arc welding/short-circuit transfer arc welding switching control method - Google Patents

Abstract

To provide a pulse arc welding/short-circuit transfer arc welding switching control method which performs welding while switching between pulse arc welding and short-circuit transfer arc welding alternately, and which can smoothly switch welding methods.SOLUTION: A pulse arc welding/short-circuit transfer arc welding switching control method, which performs welding while switching between a period of time during which a welding wire is fed at a first feeding speed to perform pulse arc welding at times t1-t2 and a period of time during which the welding wire is fed at a second feeding speed lower than the first feeding speed to perform short-circuit transfer arc-welding at times t2-t3, alternately, feeds (Fw) the welding wire at a pulse initial feeding speed lower than the first feeding speed, in a pulse initial period of time at times t1-t11, after a time point at which the period of time for the pulse arc welding starts at the time t1.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pulse arc welding/short circuit transfer arc welding switching control method that alternates between a period of pulse arc welding and a period of short circuit transfer arc welding.

A welding method is used in which the welding wire is fed and a period of pulse arc welding and a period of short circuit transfer arc welding are alternately switched (see, for example, Patent Document 1). The switching frequency in this case is about 0.1 to 10 Hz. This welding method can form beautiful scale-like beads. Furthermore, this welding method can control the heat input to the base material by adjusting the ratio of the period of pulse arc welding and the period of short circuit transfer arc welding.

JP 2019-93403 A

In conventional technology, when switching between pulsed arc welding and short-circuit transfer arc welding, the droplet transfer mode changes from spray transfer to short-circuit transfer, resulting in an unstable welding state.

The present invention aims to provide a pulse arc welding/short circuit transfer arc welding switching control method that allows smooth switching between pulse arc welding and short circuit transfer arc welding.

In order to solve the above-mentioned problems, the invention of claim 1 comprises:
1. A pulse arc welding/short circuit transfer arc welding switching control method for welding by alternately switching between a period in which a welding wire is fed at a first feed speed and pulse arc welding is performed, and a period in which the welding wire is fed at a second feed speed that is smaller than the first feed speed and short circuit transfer arc welding is performed,
During a pulse initial period from a point in time when the pulse arc welding period starts, the welding wire is fed at a pulse initial feed speed that is smaller than the first feed speed.
The present invention relates to a pulse arc welding/short circuit transfer arc welding switching control method.

The invention of claim 2 is as follows:
The initial pulse feed rate is equal to or lower than the second feed rate.
2. The pulse arc welding/short circuit transfer arc welding switching control method according to claim 1, wherein:

The invention of claim 3 is as follows:
Switching from the pulse initial feed rate to the first feed rate with a slope;
3. The pulse arc welding/short circuit transfer arc welding switching control method according to claim 1 or 2.

The present invention allows smooth switching between pulse arc welding and short circuit transfer arc welding.

1 is a block diagram of a welding power source for implementing a pulse arc welding/short circuit transfer arc welding switching control method 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 , illustrating a pulse arc welding/short circuit transfer arc welding switching control method according to an embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings.

Figure 1 is a block diagram of a welding power source for implementing a pulse arc welding/short circuit transfer arc welding switching control method according to an embodiment of the present invention. Each block will be described below with reference to the figure.

The main power supply circuit MC receives a three-phase 200V or other commercial AC power supply (not shown), performs output control by inverter control according to a drive signal Dv described below, and outputs a welding current Iw and a welding voltage Vw. Although not shown, the main power supply circuit MC includes a primary rectifier circuit that rectifies the AC commercial power supply, a capacitor that smoothes the rectified DC, an inverter circuit that converts the smoothed DC to high-frequency AC according to the drive signal Dv, a high-frequency transformer that steps down the high-frequency AC to a voltage value suitable for arc welding, a secondary rectifier circuit that rectifies the stepped-down high-frequency AC, and a reactor that smoothes the rectified DC.

The welding wire 1 is fed through the welding torch 4 by the rotation of the feed roll 5 connected to the feed motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the welding wire 1 and the base material 2, and a welding current Iw flows.

The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The average voltage detection circuit VAD receives the voltage detection signal Vd and outputs an average voltage detection signal Vad. The average voltage detection signal Vad is calculated by passing the voltage detection signal Vd through a low-pass filter. The voltage error amplifier circuit EV amplifies the error between the voltage detection signal Vd and a welding voltage setting signal Vr (described later) and outputs a voltage error amplifier signal Ev.

The average voltage error amplifier circuit EVA amplifies the error between the welding voltage setting signal Vr (described later) and the average voltage detection signal Vad, and outputs the average voltage error amplifier signal Eva. The pulse period timer circuit TFC receives the average voltage error amplifier signal Eva, performs voltage/frequency conversion on the average voltage error amplifier signal Eva, and outputs a pulse period signal Tf that becomes a high level for a short time every pulse period. The peak period timer circuit TPP receives the pulse period signal Tf, and outputs a peak period signal Tpp that becomes a high level during a predetermined peak period every time the pulse period signal Tf changes to a high level for a short time and then becomes a low level. When the peak period signal Tpp is at a high level, it is a peak period, and when it is at a low level, it is a base period.

The pulse arc welding period setting circuit T1R outputs a predetermined pulse arc welding period setting signal T1r. The first feed rate setting circuit F1R outputs a first feed rate setting signal F1r for setting the feed rate during the pulse arc welding period. The first welding voltage setting circuit V1R outputs a first welding voltage setting signal V1r for setting the welding voltage Vw during the pulse arc welding period.

The short circuit transfer arc welding period setting circuit T2R outputs a predetermined short circuit transfer arc welding period setting signal T2r. The second feed rate setting circuit F2R outputs a second feed rate setting signal F2r for setting the feed rate during the short circuit transfer arc welding period. Here, F2r < F1r. The second welding voltage setting circuit V2R outputs a second welding voltage setting signal V2r for setting the welding voltage Vw during the short circuit transfer arc welding period.

The short circuit determination circuit SD receives the voltage detection signal Vd as input, and when this value is less than a predetermined short circuit determination value (approximately 10 V), it determines that the short circuit is occurring and outputs a high-level short circuit determination signal Sd, and when this value is equal to or greater than this, it determines that the arc is occurring and outputs a low-level short circuit determination signal Sd.

The timer circuit TM receives the pulse arc welding period setting signal T1r and the short circuit transfer arc welding period setting signal T2r as inputs, performs the following processing, and outputs a timer signal Tm.
1) During the pulse arc welding period determined by the pulse arc welding period setting signal T1r, a timer signal Tm=1 is output.
2) Subsequently, during the short-circuit transfer arc welding period determined by the short-circuit transfer arc welding period setting signal T2r, a timer signal Tm=2 is output.
3) Repeat the above steps 1) and 2).

The pulse initial period timer circuit TPC receives the timer signal Tm as input and outputs a pulse initial period signal Tpc that is at a high level for a predetermined pulse initial period from the time the timer signal Tm changes to 1 (pulse arc welding period).

The pulse initial feed rate setting circuit FPR outputs a predetermined pulse initial feed rate setting signal Fpr, where Fpr<F1r. Alternatively, Fpr≦F2r may be satisfied.

The short circuit initial period timer circuit TDC receives the timer signal Tm and the short circuit determination signal Sd, performs the following process 1) or 2), and outputs a short circuit initial period signal Tdc.
1) A short circuit initial period signal Tdc that is at a high level during a predetermined short circuit initial period from the time when the timer signal changes to Tm=2 (short circuit transfer arc welding period) is output.
2) A short circuit initial period signal Tdc that is at a high level is output during the initial short circuit period from the time when the timer signal Tm changes to 2 (short circuit transfer arc welding period) until the short circuit determination signal Sd first changes to a high level (short circuit period).

The short circuit initial feed speed setting circuit FDR outputs a predetermined short circuit initial feed speed setting signal Fdr. Here, Fdr>F2r. Alternatively, Fdr<F1r, Fdr=F1r, or Fdr>F1r may be satisfied.

The feed speed setting circuit FR receives as input the first feed speed setting signal F1r, the second feed speed setting signal F2r, the pulse initial feed speed setting signal Fpr, the short circuit initial feed speed setting signal Fdr, the timer signal Tm, the pulse initial period signal Tpc, and the short circuit initial period signal Tdc, performs the following processing, and outputs the feed speed setting signal Fr.
1) When the timer signal Tm changes to 1 (pulse arc welding period), the feed speed setting signal Fr having the value of the pulse initial feed speed setting signal Fpr is output.
2) When the pulse initial period signal Tpc changes from a high level to a low level and the pulse initial period ends, the feed speed setting signal Fr changes with a slope from the value of the pulse initial feed speed setting signal Fpr, and when it reaches the value of the first feed speed setting signal F1r, it outputs the feed speed setting signal Fr which maintains that value.
3) When the timer signal Tm changes to 2 (short circuit transfer arc welding period), the feed speed setting signal Fr having the value of the short circuit initial feed speed setting signal Fdr is output.
4) When the short circuit initial period signal Tdc changes from a high level to a low level and the short circuit initial period ends, the feed speed setting signal Fr changes with a slope from the value of the short circuit initial feed speed setting signal Fdr to reach the value of the second feed speed setting signal F2r and maintains that value, and is output.

The feed control circuit FC receives the feed speed setting signal Fr and outputs a feed control signal Fc to the feed motor WM to feed the welding wire 1 at a feed speed Fw determined by the feed speed setting signal Fr. The feed motor WM feeds the welding wire 1 according to the feed control signal Fc.

The welding voltage setting circuit VR receives the first welding voltage setting signal V1r, the second welding voltage setting signal V2r, and the timer signal Tm as inputs, performs the following processing, and outputs the welding voltage setting signal Vr.
1) When the timer signal Tm changes to 1 (pulse arc welding period), a welding voltage setting signal Vr is output, which changes from the value of the second voltage setting signal V2r to the value of the first voltage setting signal V1r with a slope.
2) When the timer signal Tm changes to 2 (short-circuit transfer arc welding period), a welding voltage setting signal Vr is output, which changes from the value of the first voltage setting signal V1r to the value of the second voltage setting signal V2r having a slope.

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 current control setting circuit ICR receives the peak current setting signal Ipr, the base current setting signal Ibr, and the peak period signal Tpp as inputs, and outputs the peak current setting signal Ipr as the current control setting signal Icr when the peak period signal Tpp is at a high level (peak period), and outputs the base current setting signal Ibr as the current control setting signal Icr when the peak period signal Tpp is at a low level.

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

The welding method switching circuit SM receives the current error amplification signal Ei, the voltage error amplification signal Ev, and the timer signal Tm as inputs, and outputs the current error amplification signal Ei as the error amplification signal Ea when the timer signal Tm = 1 (pulse arc welding period), and outputs the voltage error amplification signal Ev as the error amplification signal Ea when the timer signal Tm = 2 (short circuit transfer arc welding period). Therefore, the welding power source is constant current controlled during the pulse arc welding period, and constant voltage controlled during the short circuit transfer arc welding period.

The drive circuit DV performs pulse width modulation control based on the error amplified signal Ea and outputs a drive signal Dv to drive the inverter circuit of the main power supply circuit MC.

Figure 2 is a timing chart of each signal in the welding power source of Figure 1, which shows a pulse arc welding/short circuit transfer arc welding switching control method according to an embodiment of the present invention. Figure (A) shows the time change of the feed speed Fw, Figure (B) shows the time change of the short circuit discrimination signal Sd, Figure (C) shows the time change of the welding current Iw, Figure (D) shows the time change of the welding voltage Vw, Figure (E) shows the time change of the short circuit initial period signal Tdc, and Figure (F) shows the time change of the pulse initial period signal Tpc. The operation of each signal will be explained below with reference to the figure.

The period from time t1 to t2 is a predetermined pulse arc welding period, and the period from time t2 to t3 is a predetermined short circuit transfer arc welding period. The period from time t1 to t11 is a pulse initial period. The period from time t2 to t21 is a short circuit initial period. The pulse arc welding period and the short circuit transfer arc welding period are repeated alternately. The pulse initial period is set as a predetermined period from the time when the period changes to the pulse arc welding period by the pulse initial period timer circuit TPC of FIG. 1. The predetermined period is set to about 50 to 150 ms at which the arc length becomes longer and no short circuit occurs. The short circuit initial period is set as either period 1) or 2) below by the short circuit initial period timer circuit TDC of FIG. 1. In the figure, the case 2) will be explained.
1) A predetermined period from the time when the welding period changes to the short circuit transfer arc welding period is set as the short circuit initial period. The predetermined period is set to about 50 to 150 ms, which is the period during which a short circuit first occurs.
2) The period from when the welding period changes to the short circuit transfer arc welding period to when the first short circuit occurs is set as the short circuit initial period. In this method, the short circuit initial period is not a predetermined value, but is about 100 ms.

(1) Operation of the pulse arc welding period from time t1 to t2 When the pulse arc welding period starts at time t1, as shown in FIG. 1F, the pulse initial period signal Tpc becomes high level, and the pulse initial period starts. As shown in FIG. 1A, the feed speed Fw is the value of the pulse initial feed speed setting signal Fpr in FIG. 1 during the pulse initial period from time t1 to t11. Thereafter, during the period from time t11 to t2, the feed speed Fw accelerates from the value of the pulse initial feed speed setting signal Fpr to the value of the first feed speed setting signal F1r in FIG. 1 with a slope. During this pulse arc welding period, as shown in FIG. 1C, the peak current and base current of multiple pulse periods are applied, and as shown in FIG. 1D, the peak voltage and base voltage are applied. The pulse period is controlled so that the average value of the welding voltage Vw is equal to the value of the first welding voltage setting signal V1r in FIG. 1. The peak current is set to, for example, 450A. The base current is set to, for example, 50 A. Since almost no short circuit occurs during this period, the short circuit determination signal Sd remains at a low level (arcing period) as shown in FIG.

(2) Operation during the short circuit transition arc welding period from time t2 to t3 When the short circuit transition arc welding period starts at time t2, the short circuit initial period signal Tdc goes to high level as shown in FIG. 1(E), and the short circuit initial period starts. As shown in FIG. 1(A), the feed speed Fw is the value of the short circuit initial feed speed setting signal Fdr in FIG. 1 during the short circuit initial period from time t2 to t21. Thereafter, during the period from time t21 to t3, the feed speed Fw is decelerated from the value of the short circuit initial feed speed setting signal Fdr to the value of the second feed speed setting signal F2r in FIG. 1 with a slope. Since the first short circuit occurred after the short circuit transition arc welding period started at time t21, the short circuit determination signal Sd goes to high level as shown in FIG. 1(B). In response to this, the short circuit initial period signal Tdc goes to low level as shown in FIG. 1(E), and the short circuit initial period ends. The welding voltage setting signal Vr in Fig. 1 becomes the second welding voltage setting signal V2r in Fig. 1. As shown in Fig. 1(C), the welding current Iw increases during the short circuit period and decreases during the arc period. As shown in Fig. 1(D), the welding voltage Vw has a short circuit voltage value of several volts during the short circuit period and an arc voltage value of several tens of volts during the arc period. As shown in Fig. 1(B), the short circuit determination signal Sd becomes a high level during the short circuit period. The welding voltage Vw is constant voltage controlled so as to be equal to the value of the second welding voltage setting signal V2r in Fig. 1.

Numerical examples of the above-mentioned parameters are shown below.
Welding wire: Mild steel solid wire, diameter 1.2 mm
Shielding gas: 20% argon gas + 80% carbon dioxide gas Pulse arc welding conditions: First feed speed 8 m/min (welding current 200 A), welding voltage 27 V, initial pulse feed speed 3 m/min
Conditions for short circuit transfer arc welding: second feed speed 4 m/min (welding current 100 A), second welding voltage 17 V, short circuit initial feed speed 7 m/min
Pulse arc welding period 500ms, short circuit transfer arc welding period 500ms
Pulse initial period 100 ms, short circuit initial period 100 ms
Each slope period of the feed rate is 50 ns

The effects of this embodiment will be described below.
According to this embodiment, the welding wire is fed at a pulse initial feed speed smaller than the first feed speed during the pulse initial period from the start of the pulse arc welding period. If the feed speed is switched to the first feed speed at the start of the pulse arc welding period, the wire melting speed cannot keep up with the feed speed, resulting in frequent short circuits. In this state, the welding state becomes unstable and the bead appearance deteriorates. Therefore, as in this embodiment, the feed speed is switched to a pulse initial feed speed smaller than the first feed speed from the start of the pulse arc welding period to the pulse initial period, thereby slowing down the feed speed and preventing the occurrence of short circuits. For this reason, in this embodiment, it is possible to smoothly switch between short circuit transfer arc welding and pulse arc welding.

More preferably, according to this embodiment, the initial pulse feed speed is set to a value equal to or lower than the second feed speed. In this way, the feed speed becomes even slower, so that the occurrence of a short circuit can be more reliably prevented.

More preferably, according to this embodiment, the pulse initial feed speed is switched to the first feed speed with a slope. In this way, the transition of the welding state from the pulse initial period becomes smoother.

According to this embodiment, the welding wire is fed at an initial short circuit feed speed greater than the second feed speed from the start of the short circuit transfer arc welding period until the initial short circuit period. If the feed speed is switched to the second feed speed at the start of the short circuit transfer arc welding period, the short circuit does not occur easily and the arc generation state continues for a long time. In this state, the welding state becomes unstable and the bead appearance deteriorates. Therefore, as in this embodiment, the feed speed is switched to an initial short circuit feed speed greater than the second feed speed from the start of the short circuit transfer arc welding period until the initial short circuit period, thereby encouraging the short circuit to occur early. For this reason, in this embodiment, it is possible to smoothly switch between pulse arc welding and short circuit transfer arc welding.

More preferably, according to this embodiment, the initial short circuit period is the period until the first short circuit occurs. In this way, the occurrence of the first short circuit can be more reliably promoted.

More preferably, according to this embodiment, the short circuit initial feed speed is set to the same value as the first feed speed. In this way, there is no need to set the short circuit initial feed speed, making it easier to set the feed speed parameters.

More preferably, according to this embodiment, the feed speed is switched from the initial short circuit feed speed to the second feed speed with a slope. In this way, the transition of the welding state from the initial short circuit period becomes smoother.

1 welding wire 2 base material 3 arc 4 welding torch 5 feed roll DV drive circuit Dv drive signal Ea error amplification signal EI current error amplification circuit Ei current error amplification signal EV voltage error amplification circuit Ev voltage error amplification signal EVA average voltage error amplification circuit Eva average voltage error amplification signal F1R first feed speed setting circuit F1r first feed speed setting signal F2R second feed speed setting circuit F2r second feed speed setting signal FC feed control circuit Fc feed control signal FDR short circuit initial feed speed setting circuit Fdr short circuit initial feed speed setting signal FPR pulse initial feed speed setting circuit Fpr pulse initial feed speed setting signal FR feed speed setting circuit Fr feed speed setting signal Fw feed speed IBR base current setting circuit Ibr base current setting signal ICR current control setting circuit Icr current control setting signal ID current detection circuit Id current detection signal IPR peak current setting circuit Ipr Peak current setting signal Iw Welding current MC Power supply main circuit SD Short circuit determination circuit Sd Short circuit determination signal SM Welding method switching circuit T1R Pulse arc welding period setting circuit T1r Pulse arc welding period setting signal T2R Short circuit transition arc welding period setting circuit T2r Short circuit transition arc welding period setting signal TDC Short circuit initial period timer circuit Tdc Short circuit initial period signal TFC Pulse period timer circuit Tf Pulse period signal TM Timer circuit Tm Timer signal TPC Pulse initial period timer circuit Tpc Pulse initial period signal TPP Peak period timer circuit Tpp Peak period signal V1R First welding voltage setting circuit V1r First welding voltage setting signal V2R Second welding voltage setting circuit V2r Second welding voltage setting signal VAD Average voltage detection circuit Vad Average voltage detection signal VD Voltage detection circuit Vd Voltage detection signal VR Welding voltage setting circuit Vr Welding voltage setting signal Vw Welding voltage WM Feeder motor

Claims (3)

1. A pulse arc welding/short circuit transfer arc welding switching control method for welding by alternately switching between a period in which a welding wire is fed at a first feed speed and pulse arc welding is performed, and a period in which the welding wire is fed at a second feed speed that is smaller than the first feed speed and short circuit transfer arc welding is performed,
During a pulse initial period from a point in time when the pulse arc welding period starts, the welding wire is fed at a pulse initial feed speed that is smaller than the first feed speed.
A pulse arc welding/short circuit transfer arc welding switching control method comprising: The initial pulse feed rate is equal to or lower than the second feed rate.
2. The pulse arc welding/short circuit transfer arc welding switching control method according to claim 1 . Switching from the pulse initial feed rate to the first feed rate with a slope;
3. The pulse arc welding/short circuit transfer arc welding switching control method according to claim 1 or 2.

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