Pulse arc welding control method

Abstract

To achieve an excellent welding quality by regularly maintaining a one-pulse period one droplet transfer state even when a welding state varies, in consumable electrode pulse-arc welding.SOLUTION: In a pulse-arc welding control method, in which a welding wire is fed, peak rising currents Iu that rise from a value of base currents Ib to a value of peak currents Ip are passed during peak rising period of time Tu, the peak currents Ip are passed during a peak period of time Tp, peak falling currents Ik that fall from the value of the peak currents Ip to the value of the base currents Ib are passed during a peak falling period of time Tk, the base currents Ib are passed during a base period of time Tb and the currents are repeatedly passed in one pulse period of time to perform welding, changing from a backward-feeding peak value Wr to a forward feeding peak value Ws is started at a start time point of the peak rising period of time Tu and changing from the forward feeding peak value Ws to the backward feeding peak value Wr is started at a start time point of the peak falling period of time Tk, at feeding speed Fw of the welding wire.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a pulsed arc welding control method for feeding and welding a welding wire.

Background Art

[0002] Pulsed arc welding for feeding and welding a welding wire is widely used for welding steel and the like. In this pulsed arc welding, a welding wire is fed, a peak rising current that rises from the value of the base current to the value of the peak current is energized during the peak rising period, the peak current is energized during the peak period, a peak falling current that falls from the value of the peak current to the value of the base current is energized during the peak falling period, and the base current is energized during the base period. These energizations are repeated as one pulse cycle to perform welding. In pulsed arc welding, by making one droplet transfer state per pulse cycle, generation of spatter is reduced and a beautiful bead appearance can be obtained.

[0003] In the invention of Patent Document 1, during a predetermined period from a first point in time during the peak period to a second point in time during the base period, the feeding speed of the welding wire is made lower than the feeding speed at the rising point of the peak current, or reverse feeding in which the welding wire is fed in a direction away from the welding object is performed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In pulsed arc welding, it is important to always maintain a droplet transfer state per pulse cycle in order to obtain good welding quality. However, in conventional pulsed arc welding, there is a problem that the droplet transfer state deviates from the state of one droplet transfer per pulse cycle due to fluctuations in the welding state, resulting in poor welding quality.

[0006] Therefore, an object of the present invention is to provide a pulsed arc welding control method capable of always maintaining a droplet transfer state per pulse cycle and obtaining good welding quality even when the welding state fluctuates.

Means for Solving the Problems

[0007] In order to solve the above-described problems, the invention according to claim 1 is feeding a welding wire, In a pulsed arc welding control method of repeatedly performing the above energizations as one pulse cycle and welding, during a peak rising period, energizing a peak rising current that rises from a base current value to a peak current value, during a peak period, energizing the peak current, during a peak falling period, energizing a peak falling current that falls from the peak current value to the base current value, and during a base period, energizing the base current, the welding wire repeatedly performs forward feeding and reverse feeding, and at least during the base period, performs the reverse feeding, which is a pulsed arc welding control method characterized by this.

[0008] The invention according to claim 2 is the feeding speed of the welding wire starts changing from a reverse feeding peak value to a forward feeding peak value at the start of the peak rising period, and starts changing from the forward feeding peak value to the reverse feeding peak value at the start of the peak falling period, which is the pulsed arc welding control method according to claim 1, characterized by this.

[0009] The invention according to claim 3 is the period of change from the forward feeding peak value to the reverse feeding peak value is equal to or less than the peak falling period, The pulsed arc welding control method according to claim 2, characterized in that.

[0010] The invention of claim 4 is Arc length control is performed by modulating and controlling at least the peak current. The pulsed arc welding control method according to any one of claims 1 to 3, characterized in that.

Advantages of the Invention

[0011] According to the pulsed arc welding control method of the present invention, even if the welding state fluctuates, a good welding quality can be obtained by always maintaining a droplet transfer state per pulse cycle.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a block diagram of a welding apparatus for carrying out the pulsed arc welding control method according to an embodiment of the present invention. The welding apparatus mainly includes a welding power source PS surrounded by a broken line, a robot control device RC, a robot (not shown), etc. Hereinafter, each block will be described with reference to the same figure.

[0015] The welding power source PS is composed of the following blocks.

[0016] The power control circuit MC takes an AC commercial power supply (not shown) such as three-phase 200V as input, performs output control such as inverter control according to the drive signal Dv described later, and outputs a welding voltage Vw and a welding current Iw suitable for welding. Although not shown, this power control circuit MC includes a primary rectification circuit that rectifies the AC commercial power supply, a capacitor that smoothes the rectified DC, an inverter circuit that converts the smoothed DC into high-frequency AC according to the drive signal Dv, an inverter transformer that steps down the high-frequency AC to a voltage value suitable for welding, and a secondary rectification circuit that rectifies the stepped-down high-frequency AC.

[0017] The reactor WL is inserted between the + side output of the above power control circuit MC and the welding torch 4, and smoothes the output of the power control circuit MC.

[0018] The feed motor WM is rotationally driven by a feed control signal Fc described later. The welding wire 1 is fed forward and backward at a feed speed Fw through the inside of the welding torch 4 by the rotation of the feed roll 5 coupled to the above feed motor WM, and an arc 3 is generated between 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 the power supply tip (not shown) inside the welding torch 4 and the base material 2, and a welding current Iw is energized.

[0019] The welding voltage detection circuit VD detects the above welding voltage Vw and outputs a welding voltage detection signal Vd. The welding voltage averaging circuit VAV averages (passes through a low-pass filter) this welding voltage detection signal Vd 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 above welding voltage setting signal Vr(+) and the above welding voltage average value signal Vav(-) and outputs a voltage error amplification signal Ev.

[0020] The current modulation circuit IC takes the above voltage error amplification signal Ev as an input, performs PI (Proportional-Integral) control or PID (Proportional-Integral-Derivative) control, and outputs a peak current setting signal Ipr and a base current setting signal Ibr. The peak current setting signal Ipr and the base current setting signal Ibr are current modulation controlled by this circuit so that the welding voltage average value signal Vav becomes equal to the welding voltage setting signal Vr. As a result, arc length control is performed so that the arc length is maintained at an appropriate value. It is also possible to perform current modulation control only on the peak current setting signal Ipr and set the base current setting signal Ibr to a predetermined value.

[0021] The peak rise period setting circuit TUR outputs a predetermined peak rise period setting signal Tur. The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr. The peak fall period setting circuit TKR outputs a predetermined peak fall period setting signal Tkr. The base period setting circuit TBR outputs a predetermined base period setting signal Tbr.

[0022] The welding current setting circuit IR takes the above peak rise period setting signal Tur, the above peak period setting signal Tpr, the above peak fall setting signal Tkr, the above base period setting signal Tbr, the above peak current setting signal Ipr, and the above base current setting signal Ibr as inputs, performs the following processing, and outputs a welding current setting signal Ir and a timer signal Tm. 1) During the peak rise period Tu determined by the peak rise period setting signal Tur, the timer signal Tm = 1 is output, and a peak rise current Iu that rises from the value of the base current setting signal Ibr to the value of the peak current setting signal Ipr is output as the welding current setting signal Ir. 2) Subsequently, during the peak period Tp determined by the peak period setting signal Tpr, the timer signal Tm = 2 is output, and the peak current setting signal Ipr is output as the welding current setting signal Ir. 3) Subsequently, during the peak fall period Tk determined by the peak fall period setting signal Tkr, the timer signal Tm = 3 is output, and a peak fall current Ik that falls from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr is output as the welding current setting signal Ir. 4) Subsequently, during the base period Tb determined by the base period setting signal Tbr, a timer signal Tm = 4 is output, and the base current setting signal Ibr is output as the welding current setting signal Ir. 5) Repeat the above 1) to 4).

[0023] The forward feed peak value setting circuit WSR outputs a forward feed peak value setting signal Wsr with a predetermined positive value. The reverse feed peak value setting circuit WRR outputs a reverse feed peak value setting signal Wrr with a predetermined negative value.

[0024] The welding current detection circuit ID detects the above welding current Iw and outputs a welding current detection signal Id. The current error amplification circuit EI amplifies the error between the above welding current setting signal Ir(+) and the above welding current detection signal Id(-) and outputs a current error amplification signal Ei. The drive circuit DV takes this current error amplification signal Ei and a start signal On from a robot control device RC (described later) as inputs. When the start signal On is at the High level (welding start), PWM modulation control is performed based on the current error amplification signal Ei, and a drive signal Dv for driving the inverter circuit in the above power control circuit MC is output. When the start signal On is at the Low level (welding stop), the drive signal Dv is not output.

[0025] The rising change period setting circuit TFUR outputs a rising change period setting signal Tfur with a predetermined value. The value of the rising change period setting signal Tfur is set to be equal to or less than the value of the above peak rising period setting signal Tur. The falling change period setting circuit TFKR outputs a falling change period setting signal Tfkr with a predetermined value. The value of the falling change period setting signal Tfkr is set to be equal to or less than the value of the above peak falling period setting signal Tkr.

[0026] The feed speed setting circuit FR takes the above forward feed peak value setting signal Wsr, the above reverse feed peak value setting signal Wrr, the above timer signal Tm, the above rising change period setting signal Tfur, and the above falling change period setting signal Tfkr as inputs, performs the following processing, and outputs a feed speed setting signal Fr. 1) During the rising change period Tfu determined by the rising change period setting signal Tfur from the start point of the peak rising period Tu of the timer signal Tm = 1, an output feed speed setting signal Fr that changes from the value of the reverse feed peak value setting signal Wrr to the value of the forward feed peak value setting signal Wsr is output. 2) Subsequently, the forward feed peak value setting signal Wsr is output as the feed speed setting signal Fr. 3) Subsequently, during the falling change period Tfk determined by the falling change period setting signal Tfkr from the start point of the peak falling period Tk of the timer signal Tm = 3, an output feed speed setting signal Fr that changes from the value of the forward feed peak value setting signal Wsr to the value of the reverse feed peak value setting signal Wrr is output. 4) Subsequently, the reverse feed peak value setting signal Wrr is output as the feed speed setting signal Fr. 5) Repeat the above 1) to 4).

[0027] The feed control circuit FC takes the above feed speed setting signal Fr and the start signal On from the robot control device RC described later as inputs. When the start signal On is at the High level (welding start), a feed control signal Fc for feeding the welding wire 1 at the value of the feed speed setting signal Fr is output to the above feed motor WM. When the start signal On is at the Low level, a feed control signal Fc for stopping the feed is output to the above feed motor WM.

[0028] The robot control device RC moves a robot (not shown) according to a pre - taught work program and outputs a start signal On for instructing welding start or stop.

[0029] Figure 2 is a timing chart of each signal in the welding apparatus of Figure 1 showing the pulse arc welding control method according to an embodiment of the present invention. In the figure, (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, and (C) shows the time change of the feed speed Fw of the welding wire. Hereinafter, with reference to this figure, the operations of each signal will be described.

[0030] The feeding speed Fw shown in Fig. (C) is in the forward feeding state where it advances in the direction approaching the base material when it is a positive value above 0, and is in the reverse feeding state where it retreats in the direction away from the base material when it is a negative value below 0.

[0031] During the predetermined peak rising period Tu from time t1 to t2, as shown in Fig. (A), a peak rising current Iu that rises from the base current Ib controlled by current modulation to the peak current Ip controlled by current modulation is energized, and as shown in Fig. (B), a peak rising voltage that rises from the base voltage Vb to the peak voltage Vp is applied between the welding wire and the base material. During the predetermined rising change period Tfu from time t1 to t11, as shown in Fig. (C), the feeding speed Fw changes from the value of the reverse feeding peak value Wr to the value of the forward feeding peak value Ws. The start point of the rising change period Tfu is synchronized with the start point of the peak rising period Tu. The rising change period Tfu is a period equal to or less than the peak rising period Tu. The above-mentioned peak rising period Tu is set by the peak rising period setting signal Tur in Fig. 1. The above-mentioned base current Ib is set by the base current setting signal Ibr in Fig. 1. The above-mentioned peak current Ip is set by the peak current setting signal Ipr in Fig. 1. The above-mentioned rising change period Tfu is set by the rising change period setting signal Tfur in Fig. 1. The above-mentioned reverse feeding peak value Wr is set by the reverse feeding peak value setting signal Wrr in Fig. 1. The above-mentioned forward feeding peak value Ws is set by the forward feeding peak value setting signal Wsr in Fig. 1.

[0032] During the predetermined peak period Tp from time t2 to t3, as shown in Fig. (A), the peak current Ip controlled by current modulation is energized, and as shown in Fig. (B), the peak voltage Vp is applied between the welding wire and the base material. During the period from time t11 to t3, as shown in Fig. (C), the feeding speed Fw becomes the value of the forward feeding peak value Ws. The above-mentioned peak period Tp is set by the peak period setting signal Tpr in Fig. 1.

[0033] During a predetermined peak decline period Tk from time t3 to t4, as shown in Fig. (A), a peak decline current Ik that descends from a peak current Ip controlled by current modulation to a base current Ib controlled by current modulation is energized. As shown in Fig. (B), a peak decline voltage that descends from a peak voltage Vp to a base voltage Vb is applied between the welding wire and the base material. During a predetermined decline change period Tfk from time t3 to t31, as shown in Fig. (C), the feeding speed Fw changes from the value of the forward feeding peak value Ws to the value of the reverse feeding peak value Wr. The start point of the decline change period Tfk is synchronized with the start point of the peak decline period Tk. The decline change period Tfk is a period equal to or less than the peak decline period Tk. The above-mentioned peak decline period Tk is set by the peak decline period setting signal Tkr in Fig. 1. The above-mentioned decline change period Tfk is set by the decline change period setting signal Tfkr in Fig. 1

[0034] During a predetermined base period Tb from time t4 to t5, as shown in Fig. (A), a base current Ib controlled by current modulation is energized. As shown in Fig. (B), a base voltage Vb is applied between the welding wire and the base material. During the period from time t31 to t5, as shown in Fig. (C), the feeding speed Fw becomes the value of the reverse feeding peak value Wr. Therefore, at least during the base period Tb, the welding wire is fed reversely. The above-mentioned base period Tb is set by the base period setting signal Tbr in Fig. 1

[0035] Numerical examples of the above parameters are shown below Tu = 1ms, Tp = 1ms, Tk = 1ms, Tb = 3ms Ip = 350 - 450A, Ib = 50 - 150A Tfu = 0.5 - 1ms, Tfk = 0.5 - 1ms Ws = 50m / min, Wr = -30m / min

[0036] The operation and effects of the present embodiment will be described below According to this embodiment, in a pulsed arc welding control method in which a welding wire is fed, a peak rising current that rises from the value of the base current to the value of the peak current is passed during the peak rising period, the peak current is passed during the peak period, a peak falling current that falls from the value of the peak current to the value of the base current is passed during the peak falling period, and the base current is passed during the base period, and these energizations are repeated as one pulse cycle for welding, the welding wire repeats forward feeding and reverse feeding, and at least during the base period, it is fed in reverse. By passing the peak current during the peak period, a molten droplet is formed at the tip of the welding wire. During the subsequent base period, by feeding the welding wire in reverse, an upward force can be continuously applied to the molten droplet during the base period, so that the molten droplet can be surely transferred to the molten pool. As a result, even if the welding state fluctuates, a state of transferring one molten droplet per pulse cycle can always be maintained, so that good welding quality can be obtained.

[0037] More preferably, according to this embodiment, the feeding speed of the welding wire starts to change from the reverse feeding peak value to the forward feeding peak value at the start of the peak rising period, and starts to change from the forward feeding peak value to the reverse feeding peak value at the start of the peak falling period. By synchronizing the start time of the peak rising period and the start time of the change from the reverse feeding peak value to the forward feeding peak value, a molten droplet of an appropriate size can be surely formed during the peak period. Further, by synchronizing the start time of the peak falling period and the start time of the change from the forward feeding peak value to the reverse feeding peak value, a strong upward force can be applied to the molten droplet, so that the molten droplet can be surely detached and transferred to the molten pool.

[0038] More preferably, according to this embodiment, the period of change from the forward feeding peak value to the reverse feeding peak value is equal to or less than the peak falling period. By doing so, the upward force acting on the molten droplet can be further strengthened, so that the molten droplet can be more surely detached and transferred to the molten pool.

[0039] More preferably, according to the present embodiment, arc length control is performed by modulating and controlling at least the peak current. By doing so, since the pulse period becomes a predetermined value, the average value of the feeding speed can be set to a predetermined value. As a result, it is possible to suppress fluctuations in the average value of the feeding speed and fluctuations in the bead appearance and penetration shape.

Explanation of Signs

[0040] 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feeding roll DV Driving circuit Dv Driving signal EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC Feeding control circuit Fc Feeding control signal FR Feeding speed setting circuit Fr Feeding speed setting signal Fw Feeding speed Ib Base current Ibr Base current setting signal IC Current modulation circuit ID Welding current detection circuit Id Welding current detection signal Ik Peak falling current Ip Peak current Ipr Peak current setting signal IR Welding current setting circuit Ir Welding current setting signal Iu Peak rising current Iw Welding current MC Power control circuit On Start signal PS Welding power source RC Robot control device Tb Base period TBR Base period setting circuit Tbr Base period setting signal Tfk Falling Transition Period TFKR Falling Transition Period Setting Circuit Tfkr Falling Transition Period Setting Signal Tfu Rising Transition Period TFUR Rising Transition Period Setting Circuit Tfur Rising Transition Period Setting Signal Tk Peak Falling Period TKR Peak Falling Period Setting Circuit Tkr Peak Falling Period Setting Signal Tp Peak Period TPR Peak Period Setting Circuit Tpr Peak Period Setting Signal Tu Peak Rising Period TUR Peak Rising Period Setting Circuit Tur Peak 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 Vw Welding Voltage WL Reactor WM Feeding Motor Wr Reverse Feed Peak Value WRR Reverse Feed Peak Value Setting Circuit Wrr Reverse Feed Peak Value Setting Signal Ws Forward Feed Peak Value WSR Forward Feed Peak Value Setting Circuit Wsr Forward Feed Peak Value Setting Signal

Claims

1. feeding a welding wire, during a peak rising period, passing a peak rising current that rises from the value of a base current to the value of a peak current; during a peak period, passing the peak current; during a peak falling period, passing a peak falling current that falls from the value of the peak current to the value of the base current; during a base period, passing the base current; and repeating these energizations as one pulse cycle to perform welding. In the pulse arc welding control method, the welding wire repeats forward feeding and reverse feeding, and performs reverse feeding at least during the base period, characterized in that it is a pulse arc welding control method.

2. The feeding speed of the welding wire starts changing from a reverse feeding peak value to a forward feeding peak value at the start of the peak rising period, and starts changing from the forward feeding peak value to the reverse feeding peak value at the start of the peak falling period. The pulse arc welding control method according to claim 1, characterized in that.

3. The change period from the forward feeding peak value to the reverse feeding peak value is equal to or less than the peak falling period. The pulse arc welding control method according to claim 2, characterized in that.

4. Performing arc length control by modulating at least the peak current. The pulse arc welding control method according to any one of claims 1 to 3, characterized in that.

Images