Consumable electrode pulse arc welding control method

Abstract

To suppress a welding quality from deteriorating even if an arc-interruption occurs due to arc blow, in consumable electrode pulse arc welding.SOLUTION: In a consumable electrode pulse arc welding control method, in which a welding wire is fed at regular feeding speed and rising transition currents that rise from base currents to peak currents are distributed during a rising period of time, the peak currents are distributed during a peak period of time, falling transition currents that fall from the peak currents to the base currents are distributed during a falling period of time, the base currents are distributed during the base period of time, and welding currents Iw described above are repeatedly distributed in a first pulse period to perform welding, feeding speed Fw in an arc-interruption period of time at times of T13-t2 is set to be higher than the regular feeding speed at times of t1-t13.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a consumable electrode pulse arc welding control method. [Background technology]

[0002] Consumable electrode pulsed arc welding (CPAW) is used for welding steel and other materials. In this consumable electrode pulsed arc welding process, a welding wire is fed, and a rising transition current (rising from a base current to a peak current) is applied during the rise period, the peak current is applied during the peak period, a falling transition current (declining from the peak current to a base current) is applied during the fall period, and the base current is applied during the base period. These welding currents are repeated as one pulse cycle to perform welding. Furthermore, the arc length is maintained at an appropriate value by feedback-controlling the peak current, peak period, or pulse period so that the average welding voltage is equal to the welding voltage setting. In pulsed arc welding, one droplet is transferred per pulse period, resulting in stable droplet transfer, which minimizes spatter and produces a beautiful bead.

[0003] In consumable electrode pulsed arc welding, a magnetic field is formed around the arc due to the welding current flowing through the arc and base metal, and the arc may be deflected by the force of this magnetic field. This condition is generally referred to as magnetic arc blow. In consumable electrode pulsed arc welding, the base current is small, so the arc is easily deflected when it receives a biased force from the magnetic field, easily causing magnetic arc blow. Therefore, in consumable electrode pulsed arc welding, arc deflection due to magnetic arc blow is likely to occur during the base period. When magnetic arc blow occurs, the arc deflects, resulting in poor welding quality. Furthermore, if the arc deflection becomes too large, arc interruption may occur, resulting in welding defects. Therefore, measures to prevent magnetic arc blow are important for achieving good welding quality.

[0004] Various countermeasures against magnetic arc blow have been proposed in consumable electrode pulsed arc welding. A typical example is a method in which, when magnetic arc blow is detected, the base current is increased to strengthen the arc rigidity, thereby suppressing arc deflection (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4319432 Summary of the Invention [Problem to be solved by the invention]

[0006] Even if conventional countermeasures against magnetic arc blow are implemented, it is not possible to completely prevent arc interruption caused by magnetic arc blow. When arc interruption occurs, problems such as bead breakage occur, resulting in poor welding quality.

[0007] Therefore, an object of the present invention is to provide a consumable electrode pulse arc welding control method that can prevent deterioration of welding quality even when arc interruption due to magnetic blow occurs, for example. [Means for solving the problem]

[0008] A first aspect of the present invention provides a consumable electrode pulse arc welding control method for welding by feeding a welding wire at a steady feed rate, and supplying an increasing transition current that increases from a base current to a peak current during a rise period, supplying the peak current during the peak period, supplying a decreasing transition current that decreases from the peak current to the base current during a fall period, and supplying the base current during the base period, repeating these welding currents as one pulse period, characterized in that the feed rate is made faster than the steady feed rate during an arc interruption period.

[0009] As an example, the consumable electrode pulse arc welding control method of the present invention is characterized in that the feed rate is made faster than the steady feed rate with a delay from the start of the arc interruption period.

[0010] As an example, the consumable electrode pulsed arc welding control method of the present invention is characterized in that when the occurrence of magnetic arc blow is detected based on an increase in welding voltage during the base period, the value of the base current is increased.

[0011] As an example, the consumable electrode pulse arc welding control method of the present invention is characterized in that when the welding wire comes into contact with the base metal during the arc interruption period, the start period shifts to the rise period.

[0012] As an example, the consumable electrode pulse arc welding control method of the present invention is characterized in that when the welding wire comes into contact with the base metal during the arc interruption period, the rise period is shortened and transition is made to the rise period. [Effects of the Invention]

[0013] According to the above configuration, for example, in the consumable electrode pulse arc welding control method, it is possible to suppress deterioration of welding quality even when arc interruption due to magnetic blow occurs. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a block diagram of a welding apparatus for carrying out a consumable electrode pulse arc welding control method according to an embodiment of the present invention; [Figure 2] 2 is a timing chart of each signal in the welding device of FIG. 1, illustrating a consumable electrode pulse arc welding control method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] 1 is a block diagram of a welding apparatus for carrying out a consumable electrode pulse arc welding control method according to an embodiment of the present invention. The welding apparatus mainly includes a welding power source PS, a robot control device RC, a robot (not shown), and the like, all of which are enclosed by dashed lines. Each block will be described below with reference to the diagram.

[0017] The welding power source PS is composed of the following blocks: The main power supply circuit MC receives input from a commercial AC power source (not shown), such as a three-phase 200V power source, performs output control such as inverter control in accordance with a drive signal Dv (described later), and outputs a welding voltage Vw and welding current Iw suitable for welding. Although not shown, the main power supply circuit MC also includes a primary rectifier circuit that rectifies the commercial AC power source, a capacitor that smooths the rectified DC, an inverter circuit that converts the smoothed DC into high-frequency AC in accordance with the drive signal Dv, an inverter transformer that steps down the high-frequency AC to a voltage suitable for welding, and a secondary rectifier circuit that rectifies the stepped-down high-frequency AC.

[0018] The reactor WL is inserted between the positive output of the main power supply circuit MC and the welding torch 4, and smoothes the output of the main power supply circuit MC.

[0019] The feed motor WM is rotationally driven by a feed control signal Fc, which will be described later. The welding wire 1 is fed at a feed speed Fw through the welding torch 4 by the rotation of a feed roll 5 coupled to the feed motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. The feed motor WM and the welding torch 4 are mounted on a robot. A welding voltage Vw is applied between a power feed tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw flows between the power feed tip and the base material 2.

[0020] The welding voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The welding voltage averaging circuit VAV averages the welding voltage detection signal Vd (by passing it through a low-pass filter) and outputs a welding 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 the error between the welding voltage setting signal Vr(+) and the welding voltage average value signal Vav(-) and outputs a voltage error amplification signal Ev.

[0021] The peak current modulation circuit IPC receives the voltage error amplified signal Ev, performs current modulation control based on the voltage error amplified signal Ev, and outputs the peak current setting signal Ipr. This circuit feedback controls the peak current setting signal Ipr so that the value of the welding voltage average value signal Vav is equal to the value of the welding voltage setting signal Vr.

[0022] The base current setting circuit IBR receives the magnetic blow detection signal Ad (described later) as input, and outputs a base current setting signal Ibr that is a steady base current value when the magnetic blow detection signal Ad is at a low level, and an increased base current value when the magnetic blow detection signal Ad is at a high level, where the steady base current value is less than the increased base current value.

[0023] The rise period setting circuit TUR receives an arc interruption determination signal Bd (described later) as input, outputs a predetermined steady rise period value as the rise period setting signal Tur, and outputs a value of the decreasing rise period value as the rise period setting signal Tur only once the arc interruption determination signal Bd changes from a high level to a low level. Here, the steady rise period is greater than the decreasing rise period. Therefore, when the arc interruption determination signal Bd changes from a high level to a low level (when the welding wire comes into contact with the base metal during the arc interruption period), the rise period is set shorter than the steady rise period.

[0024] The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr.

[0025] The falling period setting circuit TKR outputs a predetermined falling period setting signal Tkr.

[0026] The base period setting circuit TBR outputs a predetermined base period setting signal Tbr.

[0027] The welding current setting circuit IR receives the rise period setting signal Tur, the peak period setting signal Tpr, the fall period setting signal Tkr, the base period setting signal Tbr, the peak current setting signal Ipr, the base current setting signal Ibr, and an arc interruption determination signal Bd (described later) as inputs, performs the following processing, and outputs a welding current setting signal Ir. 1) During the period determined by the rise period setting signal Tur, the welding current setting signal Ir is output, which rises from the value of the base current setting signal Ibr to the value of the peak current setting signal Ipr. 2) Subsequently, during the period determined by the peak period setting signal Tpr, the peak current setting signal Ipr is output as the welding current setting signal Ir. 3) Subsequently, during the period determined by the falling period setting signal Tkr, the welding current setting signal Ir is output, which decreases from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr. 4) Subsequently, during the period determined by the base period setting signal Tbr, the base current setting signal Ibr is output as the welding current setting signal Ir. 5) When the period determined by the base period setting signal Tbr ends while the arc interruption detection signal Bd is not at a high level, or when the arc interruption detection signal Bd changes from a high level to a low level, the process transitions to 1) above.

[0028] The magnetic blow detection circuit AD receives the welding voltage detection signal Vd and determines that a magnetic blow has occurred while the value of the welding voltage detection signal Vd is equal to or greater than a predetermined reference voltage value Vt, and outputs a magnetic blow detection signal Ad that goes high. The occurrence of a magnetic blow may also be determined when the rate of increase of the welding voltage detection signal Vd reaches a reference value or greater.

[0029] The arc interruption determination circuit BD receives the welding voltage detection signal Vd as input, determines that an arc interruption has occurred during the period when the value of the welding voltage detection signal Vd is equal to or greater than a predetermined arc interruption determination value, and outputs an arc interruption determination signal Bd that goes to a high level.

[0030] The welding current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The current error amplifier circuit EI amplifies the error between the welding current setting signal Ir(+) and the welding current detection signal Id(-) and outputs a current error amplification signal Ei. The drive circuit DV receives the current error amplification signal Ei and an activation signal On from the robot control device RC (described later), and performs pulse width modulation control based on the current error amplification signal Ei when the activation signal On is high (welding starts) and outputs a drive signal Dv for driving the inverter circuit in the main power supply circuit MC, but does not output the drive signal Dv when the activation signal On is low (welding stops).

[0031] The steady feed speed setting circuit FCR outputs a predetermined steady feed speed setting signal Fcr.

[0032] The feed speed setting circuit FR receives as input the steady-state feed speed setting signal Fcr and the arc interruption determination signal Bd, and outputs a feed speed setting signal Fr that has the value of the steady-state feed speed setting signal Fcr when the arc interruption determination signal Bd is at a low level, and that has a value obtained by adding a predetermined increase value to the value of the steady-state feed speed setting signal Fcr during the high level period, with a delay from the time when the arc interruption determination signal Bd changes to a high level.

[0033] The feed control circuit FC receives as input the feed speed setting signal Fr and a start signal On from the robot control device RC described later, and outputs a feed control signal Fc to the feed motor WM for feeding the welding wire 1 at the value of the feed speed setting signal Fr when the start signal On is at a high level (welding start), and outputs a feed control signal Fc to the feed motor WM for stopping feeding when the start signal On is at a low level.

[0034] The robot control device RC moves a robot (not shown) in accordance with a pre-taught work program, and outputs a start signal On to command the start or stop of welding.

[0035] 2 is a timing chart of each signal in the welding apparatus of FIG. 1, illustrating a consumable electrode pulse arc welding control method according to an embodiment of the present invention. (A) in FIG. 2 shows the change over time in welding current Iw, (B) in FIG. 2 shows the change over time in welding voltage Vw, (C) in FIG. 2 shows the change over time in magnetic blow detection signal Ad, (D) in FIG. 2 shows the change over time in welding wire feed speed Fw, and (E) in FIG. 2 shows the change over time in arc interruption detection signal Bd. The operation of each signal will be explained below with reference to the diagram.

[0036] In the pulse period Tf from time t1 to t2, during the rise period Tu, as shown in FIG. 1A, an upward transition current Iu is passed, which rises from a base current Ib to a peak current Ip, and as shown in FIG. 1B, an upward transition voltage is applied between the welding wire and the base metal, which rises from a base voltage Vb to a peak voltage Vp. During the subsequent peak period Tp, as shown in FIG. 1A, a peak current Ip having a large current value equal to or greater than a critical value is passed to transfer a droplet from the welding wire, and as shown in FIG. 1B, a peak voltage Vp proportional to the arc length is applied. During the subsequent fall period Tk, as shown in FIG. 1A, a downward transition current Ik is passed, which falls from the peak current Ip to a base current Ib, and as shown in FIG. 1B, a downward transition voltage is applied, which falls from the peak voltage Vp to a base voltage Vb. During the subsequent base period Tb, as shown in Figure 1(A), a base current Ib of a small value below the critical value is applied to prevent droplet formation, and as shown in Figure 1(B), a base voltage Vb proportional to the arc length is applied. The arc length increases during the peak period Tp and decreases during the base period Tb.

[0037] The peak current Ip is feedback-controlled (current modulation-controlled) so that the value of the welding voltage average value signal Vav of FIG. 1 is equal to the predetermined value of the welding voltage setting signal Vr of FIG. 1. To achieve this, the rise period Tu determined by the rise period setting signal Tur of FIG. 1, the peak period Tp determined by the peak period setting signal Tpr of FIG. 1, the fall period Tk determined by the fall period setting signal Tkr of FIG. 1, the base period Tb determined by the base period setting signal Tbr of FIG. 1, and the base current Ib determined by the base current setting signal Ibr of FIG. 1 are all set to predetermined values. The peak current Ip is controlled by the peak current setting signal Ipr of FIG. 1, and is determined by feedback control so that the average value of the welding voltage Vw is equal to the predetermined welding voltage setting value. For example, Tu = 1 ms, Tp = 1.2 ms, Tk = 1 ms, Tb = 3 ms, and Ib = 50 A. Ip is not a predetermined value, but varies within a range of approximately 400 to 550 A.

[0038] At time t11 during the base period Tb, a magnetic blow occurs, deflecting the arc and lengthening the arc length. As a result, the base voltage Vb rises from its normal value, as shown in Figure 1B. Then, at time t12, the base voltage Vb exceeds a predetermined reference voltage Vt (approximately 50 V), indicated by the dashed line. When it is determined that the base voltage Vb has exceeded the reference voltage Vt, the magnetic blow detection signal Ad changes to a high level, as shown in Figure 1C. In response, the base current Ib increases from a steady base current value (approximately 50 A) to an increased base current value (approximately 200 A), as shown in Figure 1A. This increases the arc's rigidity and suppresses arc deflection due to magnetic blow.

[0039] The arc length increases further due to magnetic arc blow, making it impossible to maintain the arc generation state, resulting in arc interruption at time t13. When arc interruption occurs, the welding current Iw drops to 0 A, as shown in FIG. 1(A), and the welding voltage Vw drops to the no-load voltage (approximately 80 V), which is the maximum output voltage, as shown in FIG. 1(B). Because the welding voltage Vw exceeds the arc interruption threshold (approximately 60 V), the arc interruption detection signal Bd changes to a high level, as shown in FIG. 1(E). In response, starting from a delay (approximately 1 ms) from time 13, the feed speed Fw is accelerated to a value obtained by adding an incremental value to the steady-state feed speed determined by the steady-state feed speed setting signal Fcr in FIG. 1, as shown in FIG. 1(D). For example, the steady-state feed speed is in the range of 3 to 10 m / min, and the incremental value is approximately 10 to 20 m / min.

[0040] At time t2, when the tip of the welding wire comes into contact with the base metal, a welding current Iw is applied, generating an arc. As shown in FIG. 1A, the welding current Iw begins with a rising period Tu, causing an ascending transition current Iu to flow, rising from a base current Ib to a peak current Ip. As shown in FIG. 1B, the welding voltage Vw reaches an arc voltage value of approximately 20 to 40 V. Because the welding voltage Vw falls below the reference voltage Vt, the magnetic arc blow detection signal Ad returns to a low level, as shown in FIG. 1C. In response, the base current Ib returns to its steady-state base current value. At the same time, because the welding voltage Vw falls below the arc interruption detection value, the arc interruption detection signal Bd returns to a low level, as shown in FIG. 1E. In response, the feed speed Fw returns to the value of the steady-state feed speed setting signal Fcr, as shown in FIG. 1D. Since the rise period Tu is a decreasing rise period (about 0.5 ms) that is shorter than the steady rise period (1 ms), the rate of increase of the welding current Iw immediately after the tip of the welding wire comes into contact with the base metal becomes large, resulting in good re-ignition of the arc.

[0041] The effects of this embodiment are described below. According to this embodiment, a consumable electrode pulse arc welding control method performs welding by feeding a welding wire at a steady feed rate, and passing an increasing transition current that increases from a base current to a peak current during a rise period, passing the peak current during a peak period, passing a decreasing transition current that decreases from the peak current to a base current during a fall period, and passing the base current during a base period, repeating these welding currents as one pulse period. In this method, the feed rate is increased above the steady feed rate during an arc interruption period. When a magnetic arc blow occurs, the arc length increases, and it becomes impossible to maintain an arc generation state, arc interruption occurs. For example, assume that the arc length when arc interruption occurs is 3 mm. If the steady feed rate is 6 m / min, it takes 30 ms to feed 3 mm. Increasing the feed rate to 18 m / min shortens this time to 10 ms. Therefore, by making the feed speed faster than the steady feed speed during the arc interruption period, the period of arc interruption can be shortened, and therefore deterioration of welding quality can be suppressed even if arc interruption occurs due to magnetic blow.

[0042] More preferably, according to this embodiment, the feed speed is made faster than the steady-state feed speed with a delay from the start of the arc interruption period. Even if an arc interruption occurs, an arc may re-start immediately afterwards due to irregular movement of the molten pool, etc. For this reason, in consideration of the instantaneous re-ignition of an arc, the feed speed is made faster than the steady-state feed speed with a delay from the start of the arc interruption period. In this way, the feed speed does not change when an arc re-starts, thereby improving the welding quality.

[0043] More preferably, according to this embodiment, when the occurrence of magnetic arc blow is detected based on an increase in welding voltage during the base period, the value of the base current is increased. When the value of the base current increases, the rigidity of the arc increases, making it possible to suppress arc deflection due to magnetic arc blow. This reduces the frequency of arc interruption due to magnetic arc blow.

[0044] More preferably, according to this embodiment, when the welding wire comes into contact with the base metal during the arc interruption period, the period transitions to the rise period, whereby the welding current can be increased sharply immediately after the tip of the welding wire comes into contact with the base metal, thereby improving the condition for re-igniting the arc.

[0045] More preferably, according to this embodiment, when the welding wire comes into contact with the base metal during the arc interruption period, the rise period is shortened and the start of the rise period is initiated. By shortening the rise period, the rise of the welding current can be made steeper, thereby improving the condition for re-igniting the arc. [Explanation of symbols]

[0046] 1: welding wire, 2: base material, 3: arc, 4: welding torch, 5: feed roll, AD: magnetic blow detection circuit, Ad: magnetic blow detection signal, BD: arc interruption detection circuit, Bd: arc interruption detection signal, DV: drive circuit, Dv: drive signal, EI: current error amplifier circuit, Ei: current error amplification signal, EV: voltage error amplifier circuit, Ev: voltage error amplification signal, FC: feed control circuit, Fc: feed control signal, FCR: steady-state feed speed setting circuit, Fcr: steady-state feed speed setting signal, FR: feed speed setting circuit, Fr: feed speed setting signal, Fw: feed speed, Ib: base current, IBR: base current setting circuit, Ibr: base current setting signal, ID: welding current detection circuit, Id: welding current detection signal, Ik: falling transition current, Ip: peak current, IPC Peak current modulation circuit, Ipr: Peak current setting signal, IR: Welding current setting circuit, Ir: Welding current setting signal, Iu: Rising transition current, Iw: Welding current, MC: Main power supply circuit, On: Start signal, PS: Welding power source, RC: Robot controller, Tb: Base period, TBR: Base period setting circuit, Tbr: Base period setting signal, Tk: Falling period, TKR: Falling period setting circuit, Tkr: Falling period setting signal, Tp: Peak period, TPR: Peak period setting circuit, Tpr: Peak period setting signal, Tu: Rising period, TUR: Rising period setting circuit, Tur: Rising period setting signal, VAV: Welding voltage averaging circuit, Vav: Welding voltage average value signal, Vb: Base voltage, VD: Welding voltage detection circuit, Vd: Welding voltage detection signal, Vp: Peak voltage, VR: Welding voltage setting circuit, Vr: Welding voltage setting signal, Vt: Reference voltage value, Vw: Welding voltage, WL: Reactor, WM: Feed motor

Claims

1. 1. A consumable electrode pulse arc welding control method for welding by feeding a welding wire at a steady feed rate, and supplying an increasing transition current that increases from a base current to a peak current during a rise period, supplying the peak current during the peak period, supplying a decreasing transition current that decreases from the peak current to the base current during a fall period, and supplying the base current during the base period, the supplying of these welding currents forming one pulse period, a feed rate during an arc interruption period that is faster than the steady feed rate;

2. 2. The consumable electrode pulse arc welding control method according to claim 1, wherein the feed rate is made faster than the steady feed rate with a delay from the start of the arc interruption period.

3. 3. The consumable electrode pulse arc welding control method according to claim 1, wherein when the occurrence of magnetic arc blow is detected based on an increase in welding voltage during the base period, the value of the base current is increased.

4. 3. The consumable electrode pulse arc welding control method according to claim 1, wherein the start-up period is initiated when the welding wire comes into contact with the base metal during the arc interruption period.

5. 3. The consumable electrode pulse arc welding control method according to claim 1, wherein when the welding wire comes into contact with the base metal during the arc interruption period, the rise period is shortened and transition is made to the rise period.

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