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 peak rising currents that rise from a value of base currents Ib to a value of peak currents Ip are passed during a peak rising period of time Tu, the peak currents Ip are passed during a peak period of time Tp, peak falling currents 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 Tf to perform welding, a forward feeding peak value Ws and a backward feeding peak value Wr are repeated at feeding speed Fw of a welding wire, where the backward feeding peak value Wr is set at least during the base period of time Tb and the forward feeding peak value Ws and / or the backward feeding peak value Wr is subjected to variable speed control so that average values of the feeding speed Fw become constant.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Pulse arc welding for feeding and welding a welding wire is widely used for welding steel and the like. In this pulse arc welding, a welding wire is fed, and during the peak rise period, 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 period, the peak current is energized, during the peak fall period, a peak falling current that falls from the value of the peak current to the value of the base current is energized, and during the base period, the base current is energized. These energizations are repeated as one pulse cycle, and the arc length is controlled by modulating the pulse cycle to perform welding. In pulse 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 is performed in which the welding wire is fed in a direction away from the welding object.

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 single droplet transfer state per pulse cycle in order to obtain good welding quality. However, in conventional pulsed arc welding, there is a problem in that, due to fluctuations in the welding state, the droplet transfer state deviates from the single droplet transfer state per pulse cycle, 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 single 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 feeds a welding wire, during the peak rise period, passes a peak rising current that rises from the value of the base current to the value of the peak current, during the peak period, passes the peak current, during the peak fall period, passes a peak falling current that falls from the value of the peak current to the value of the base current, and during the base period, passes the base current, and repeats these energizations as a single pulse cycle, in a pulsed arc welding control method for controlling the arc length by modulating and controlling the pulse cycle and performing welding, the feeding speed of the welding wire repeats a forward feeding peak value and a reverse feeding peak value, and is at least the reverse feeding peak value during the base period, wherein the forward feeding peak value and / or the reverse feeding peak value are variably speed-controlled so that the average value of the feeding speed becomes constant, which is a pulsed arc welding control method characterized by this.

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

[0009] The invention according to claim 3 is characterized in that a period of change from the forward peak value to the reverse peak value is equal to or less than the peak fall period in the pulse arc welding control method according to claim 2

[0010] The invention according to claim 4 is characterized in that a period of change from the reverse peak value to the forward peak value is equal to or less than the peak rise period in the pulse arc welding control method according to claim 2 or 3

Advantages of the Invention

[0011] According to the pulse 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 implementing a pulse 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 figure

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

[0016] The power control circuit MC takes an AC commercial power source such as 3-phase 200V (not shown) 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 for rectifying the AC commercial power source, a capacitor for smoothing the rectified DC, an inverter circuit for converting the smoothed DC into high-frequency AC according to the drive signal Dv, an inverter transformer for stepping down the high-frequency AC to a voltage value suitable for welding, and a secondary rectification circuit for rectifying 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 to smooth the output of the power control circuit MC.

[0018] The feeding motor WM is rotationally driven by a feeding control signal Fc described later. The welding wire 1 is fed forward and backward at a feeding speed Fw through the inside of the welding torch 4 by the rotation of the feeding roll 5 coupled to the above feeding motor WM, and an arc 3 is generated between the base material 2. The feeding 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 this welding voltage detection signal Vd (passes 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 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 pulse period modulation control circuit VF takes the above voltage error amplification signal Ev as an input, performs voltage / frequency conversion based on the voltage error amplification signal Ev, and outputs a pulse period signal Tf that becomes a high level for a short time for each pulse period.

[0021] The peak rising period setting circuit TUR outputs a predetermined peak rising period setting signal Tur. The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr. The peak falling period setting circuit TKR outputs a predetermined peak falling period setting signal Tkr.

[0022] 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.

[0023] The welding current setting circuit IR takes the above pulse period signal Tf, the above peak rising period setting signal Tur, the above peak period setting signal Tpr, the above peak falling setting signal Tkr, the above peak current setting signal Ipr, and the above base current setting signal Ibr as inputs. Each time the pulse period signal Tf changes to a high level for a short time, it performs the following processing and outputs a welding current setting signal Ir and a timer signal Tm. 1) During the peak rising period Tu determined by the peak rising period setting signal Tur, the timer signal Tm = 1 is output, and a welding current setting signal Ir that rises from the value of the base current setting signal Ibr to the value of the peak current setting signal Ipr is output. 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 falling period Tk determined by the peak falling period setting signal Tkr, the timer signal Tm = 3 is output, and a welding current setting signal Ir that falls from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr is output. 4) Subsequently, during the base period Tb until the pulse period signal Tf becomes High level again for a short time, a timer signal Tm = 4 is output, and a base current setting signal Ibr is output as a welding current setting signal Ir.

[0024] The average feed speed setting circuit FAR outputs a predetermined average feed speed setting signal Far. The feed speed error amplification circuit EF amplifies the error between the above average feed speed setting signal Far(+) and an average feed speed detection signal Fad(-) described later, and outputs a feed speed error amplification signal Ef.

[0025] The forward feed peak value setting circuit WSR uses the above feed speed error amplification signal Ef as an input, performs variable speed control so that the value of the average feed speed detection signal Fad becomes equal to the value of the average feed speed setting signal Far, and outputs a positive forward feed peak value setting signal Wsr. The reverse feed peak value setting circuit WRR uses the above feed speed error amplification signal Ef as an input, performs variable speed control so that the value of the average feed speed detection signal Fad becomes equal to the value of the average feed speed setting signal Far, and outputs a negative reverse feed peak value setting signal Wrr. It is also possible to perform variable speed control on only one of the forward feed peak value setting signal Wsr or the reverse feed peak value setting signal Wrr.

[0026] 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 High level (welding start), it performs PWM modulation control based on the current error amplification signal Ei and outputs a drive signal Dv for driving the inverter circuit in the above power control circuit MC. When the start signal On is at Low level (welding stop), it does not output the drive signal Dv.

[0027] The rising change period setting circuit TFUR outputs a preset rising change period setting signal Tfur. The value of the rising change period setting signal Tfur is set to be equal to or less than the value of the above-mentioned peak rising period setting signal Tur. The falling change period setting circuit TFKR outputs a preset falling change period setting signal Tfkr. The value of the falling change period setting signal Tfkr is set to be equal to or less than the value of the above-mentioned peak falling period setting signal Tkr.

[0028] The feed speed setting circuit FR takes the above-mentioned forward feed peak value setting signal Wsr, the above-mentioned reverse feed peak value setting signal Wrr, the above-mentioned timer signal Tm, the above-mentioned rising change period setting signal Tfur, and the above-mentioned 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 when the timer signal Tm = 1, a 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 when the timer signal Tm = 3, a 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).

[0029] The feed control circuit FC takes the above-mentioned feed speed setting signal Fr 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), 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-mentioned 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-mentioned feed motor WM.

[0030] The average feed speed detection circuit FAD takes the above feed speed setting signal Fr as an input, detects the average value of the feed speed setting signal Fr, and outputs an average feed speed detection signal Fad.

[0031] 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 welding stop.

[0032] FIG. 2 is a timing chart of each signal in the welding apparatus shown in FIG. 1, which shows a pulse arc welding control method according to an embodiment of the present invention. FIG. (A) shows the time change of the welding current Iw, FIG. (B) shows the time change of the welding voltage Vw, and FIG. (C) shows the time change of the feeding speed Fw of the welding wire. Hereinafter, with reference to this figure, the operation of each signal will be described.

[0033] The feeding speed Fw shown in FIG. (C) is in a forward feeding state where it advances in a direction approaching the base material when it is a positive value above 0, and in a reverse feeding state where it retreats in a direction away from the base material when it is a negative value below 0.

[0034] During a predetermined peak rising period Tu from time t1 to t2, as shown in Fig. (A), a peak rising current Iu that rises from a predetermined base current Ib to a predetermined peak current Ip is energized, and as shown in Fig. (B), a peak rising voltage that rises from a base voltage Vb to a peak voltage Vp is applied between the welding wire and the base material. During a 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.

[0035] During a predetermined peak period Tp from time t2 to t3, as shown in Fig. (A), a predetermined peak current Ip is energized, and as shown in Fig. (B), a 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.

[0036] During a predetermined peak-down period Tk from time t3 to t4, as shown in Fig. (A), a peak-down current Ik that descends from a predetermined peak current Ip to a predetermined base current Ib is energized, and as shown in Fig. (B), a peak-down 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 down-change period Tfk from time t3 to t31, as shown in Fig. (C), the feeding speed Fw changes from the value of the forward-feed peak value Ws to the value of the reverse-feed peak value Wr. The start point of the down-change period Tfk is synchronized with the start point of the peak-down period Tk. The down-change period Tfk is a period equal to or less than the peak-down period Tk. The above-mentioned peak-down period Tk is set by the peak-down period setting signal Tkr in Fig. 1. The above-mentioned down-change period Tfk is set by the down-change period setting signal Tfkr in Fig. 1

[0037] During a base period Tb determined by pulse-period modulation control from time t4 to t5, as shown in Fig. (A), a predetermined base current Ib is energized, and 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-feed peak value Wr

[0038] The pulse period Tf from time t1 to t5 is modulation-controlled by the pulse-period modulation control circuit VF in Fig. 1 so that the value of the average welding voltage signal Vav in Fig. 1 becomes equal to the value of the welding voltage setting signal Vr in Fig. 1, and the arc length is controlled to an appropriate value. Further, by the forward-feed peak value setting circuit WSR and the reverse-feed peak value setting circuit WRR in Fig. 1, the forward-feed peak value setting signal Wsr and the reverse-feed peak value setting signal Wrr are variably speed-controlled so that the value of the average feeding speed detection signal Fad in Fig. 1 becomes equal to the value of the average feeding speed setting signal Far in Fig. 1. Therefore, the feeding speed Fw of the welding wire repeats the forward-feed peak value Ws and the reverse-feed peak value Wr, and becomes the reverse-feed peak value Wr at least during the base period Tb. Even if the pulse period Tf changes moment by moment due to the above-described arc length control, since the forward-feed peak value Ws and / or the reverse-feed peak value Wr are variably speed-controlled, the average value of the feeding speed Fw becomes constant

[0039] Numerical examples of the above parameters are shown below. Tu = 1 ms, Tp = 1 ms, Tk = 1 ms, Tf = 4 to 10 ms (Tb = 1 to 7 ms) Ip = 400 A, Ib = 100 A Tfu = 0.5 to 1 ms, Tfk = 0.5 to 1 ms Ws = 50 m / min, Wr = -30 m / min

[0040] Next, the effects of this embodiment will be described. 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 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, and these energizations are repeated with one pulse period as a cycle, and the arc length is controlled by modulating the pulse period for welding. The feeding speed of the welding wire repeats a forward feeding peak value and a reverse feeding peak value, and is at least the reverse feeding peak value during the base period, and the forward feeding peak value and / or the reverse feeding peak value are variably speed-controlled so that the average value of the feeding speed becomes constant. By energizing the peak current during the peak period, a droplet is formed at the tip of the welding wire. During the subsequent base period, by setting the feeding speed to the reverse feeding peak value, an upward force can be continuously applied to the droplet during the base period, so that the droplet can be surely transferred to the molten pool. As a result, even if the welding state fluctuates, a droplet transfer state of one droplet per pulse period can always be maintained. Further, even if the pulse period changes moment by moment due to arc length control, since the forward feeding peak value and / or the reverse feeding peak value are variably speed-controlled, the average value of the feeding speed becomes a constant value during welding, and the welding quality can be maintained well.

[0041] More preferably, according to the present 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 of the peak rising period with the start of the change from the reverse feeding peak value to the forward feeding peak value, droplets of an appropriate size can be reliably formed during the peak period. Further, by synchronizing the start of the peak falling period with the start of the change from the forward feeding peak value to the reverse feeding peak value, a strong upward force can be applied to the droplet, so that the droplet can be reliably detached and transferred to the molten pool.

[0042] More preferably, according to the present embodiment, the period of change from the forward feeding peak value to the reverse feeding peak value is less than or equal to the peak falling period. By doing so, the upward force acting on the droplet can be further increased, so that the droplet can be more reliably detached and transferred to the molten pool.

[0043] More preferably, according to the present embodiment, the period of change from the reverse feeding peak value to the forward feeding peak value is less than or equal to the peak rising period. By doing so, droplets of an appropriate size can be reliably formed during the peak period, so that the one-droplet transfer state per pulse period can be more reliably maintained.

Explanation of Reference Numerals

[0044] 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feeding roll DV drive circuit Dv drive signal EF feeding speed error amplification circuit Ef feeding speed error amplification signal EI current error amplification circuit Ei current error amplification signal EV voltage error amplification circuit Ev voltage error amplification signal FAD average feeding speed detection circuit Fad average feed speed detection signal FAR average feed speed setting circuit Far average feed speed setting signal FC feed control circuit Fc feed control 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 peak downward current Ip peak current IPR peak current setting circuit Ipr peak current setting signal IR welding current setting circuit Ir welding current setting signal Iu peak upward current Iw welding current MC power control circuit On start signal PS welding power source RC robot control device Tb base period Tf pulse period (signal) Tfk downward change period TFKR downward change period setting circuit Tfkr downward change period setting signal Tfu upward change period TFUR upward change period setting circuit Tfur upward change period setting signal Tk peak downward period TKR peak downward period setting circuit Tkr peak downward period setting signal Tp peak period TPR peak period setting circuit Tpr peak period setting signal Tu peak upward period TUR Peak Rise Period Setting Circuit Tur Peak Rise 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 VF Pulse Period Modulation Control Circuit Vp Peak Voltage VR Welding Voltage Setting Circuit Vr Welding Voltage Setting Signal Vw Welding Voltage WL Reactor WM Feed 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, passing a peak rising current that rises from the value of the base current to the value of the peak current during the peak rising period, passing the peak current during the peak period, passing a peak falling current that falls from the value of the peak current to the value of the base current during the peak falling period, and passing the base current during the base period, and repeating these energizations as one pulse cycle, In a pulsed arc welding control method for controlling the arc length by modulating and controlling the pulse cycle and performing welding, the feeding speed of the welding wire repeats a forward feeding peak value and a reverse feeding peak value, and is at least the reverse feeding peak value during at least the base period, variably controlling the forward feeding peak value and / or the reverse feeding peak value so that the average value of the feeding speed becomes constant, A pulsed arc welding control method characterized by this.

2. The feeding speed is starting to change from the reverse feeding peak value to the forward feeding peak value at the start of the peak rising period, starting to change from the forward feeding peak value to the reverse feeding peak value at the start of the peak falling period, The pulsed arc welding control method according to Claim 1, characterized by this.

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 pulsed arc welding control method according to Claim 2, characterized by this.

4. The change period from the reverse feeding peak value to the forward feeding peak value is equal to or less than the peak rising period, The pulsed arc welding control method according to Claim 2 or 3, characterized by this.

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