Ac pulse arc welding control method

Abstract

To provide good welding quality by constantly maintaining a one-pulse period one-droplet transfer state even when a welding state changes in consumable electrode ac pulse arc welding.SOLUTION: This AC pulse arc welding control method energizes, during an electrode plus polarity period, a transition current rising from a base current value to a peak current value, energizes a peak current, energizes a transition current falling from the value of the peak current to the value of the base current, energizes the base current, energizes an electrode minus polarity current, repeats these energization steps as one pulse period, and modulation-controls the pulse period to control an arc length. A feeding speed Fw repeats a forward feed peak value and a reverse feed peak value. The feeding speed takes the reverse feed peak value during at least a base period of time t4-t5 and during an electrode minus polarity period of time t5-t6, and the forward feed peak value and / or the reverse feed peak value is variable-speed controlled so as to make an average value of the feeding speeds Fw constant.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for controlling AC pulse arc welding in which welding is performed by feeding a welding wire. [Background technology]

[0002] Pulse arc welding, which uses a welding wire to weld, is widely used for welding steel and other materials. To increase welding speed and improve welding efficiency, the melting rate of the welding wire must be increased. AC pulse arc welding, by incorporating a negative electrode polarity period, can increase the melting rate of the welding wire by approximately 1.5 times compared to DC pulse arc welding. In AC pulse arc welding, the welding wire is fed, and during the positive electrode polarity period, a peak rise current is applied, which rises from the base current to the peak current during the peak rise period, a peak current is applied during the peak period, a peak fall current is applied, which falls from the peak current to the base current during the peak fall period, a base current is applied during the base period, and a negative electrode polarity current is applied during the negative electrode polarity period. These current applications are repeated as one pulse period, and the arc length is controlled by modulating the pulse period. Pulse arc welding minimizes spatter and produces a beautiful bead appearance by achieving one droplet transfer per pulse period.

[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 welding wire feed speed is set to be slower than the feed speed at the rising point of the peak current, or the welding wire is fed in a reverse direction, i.e., in a direction away from the workpiece to be welded. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6123069 Summary of the Invention [Problem to be solved by the invention]

[0005] In AC pulsed arc welding, the size of the droplets formed at the tip of the welding wire is larger than in DC pulsed arc welding. As a result, in conventional AC pulsed arc welding, the transfer state of one droplet per pulse cycle deviates, resulting in a problem of poor welding quality.

[0006] Therefore, an object of the present invention is to provide an AC pulse arc welding control method that can always maintain a one-droplet-per-pulse-cycle state and obtain good welding quality. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the invention of claim 1 is as follows: Feed the welding wire; In the electrode positive polarity period, a peak rise current that rises from a base current value to a peak current value is passed during a peak rise period, the peak current is passed during the peak period, a peak fall current that falls from the peak current value to the base current value is passed during a peak fall period, the base current is passed during the base period, and an electrode negative polarity current is passed during an electrode negative polarity period, and these passes are repeated as one pulse period; In the AC pulse arc welding control method, the arc length is controlled by modulating the pulse period, and welding is performed by controlling the arc length. the welding wire feed speed alternates between a forward feed peak value and a reverse feed peak value, and is at the reverse feed peak value at least during the base period and the electrode negative polarity period; variably controlling the forward feed peak value and / or the reverse feed peak value so that the average value of the feeding speed is constant; The present invention relates to a method for controlling AC pulse arc welding.

[0008] The invention of claim 2 is as follows: The welding wire feed speed is a change from the reverse transport peak value to the forward transport peak value at a start of the peak rise period; a change from the forward transport peak value to the reverse transport peak value at a start of the peak fall period; 2. The AC pulse arc welding control method according to claim 1, wherein:

[0009] The invention of claim 3 is as follows: a transition period from the forward transport peak value to the reverse transport peak value is equal to or shorter than the peak fall period; 3. The AC pulse arc welding control method according to claim 2, wherein:

[0010] The invention of claim 4 is as follows: the absolute value of the reverse transport peak value is set to a value greater during the electrode negative polarity period than during the base period; 4. The AC pulse arc welding control method according to claim 3, wherein:

[0011] The invention of claim 5 is as follows: The electrode negative polarity current ratio is maintained at a set value by modulating and controlling the electrode negative polarity current. 5. The AC pulse arc welding control method according to claim 1, wherein: the AC pulse arc welding control method comprises: a step of: controlling a first AC pulse arc welding process; [Effects of the Invention]

[0012] According to the AC pulse arc welding control method of the present invention, a one-droplet-per-pulse-cycle state can be constantly maintained, thereby obtaining good welding quality. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a block diagram of a welding device for carrying out an AC 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 method for controlling AC pulse arc welding according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] 1 is a block diagram of a welding apparatus for carrying out an AC pulse arc welding control method according to an embodiment of the present invention. The welding apparatus is mainly composed of a welding power source PS, a robot control device RC, a robot (not shown), etc., all of which are enclosed by a dashed line. Each block will be described below with reference to the diagram.

[0016] The welding power source PS consists of the following blocks:

[0017] The power control circuit MC is connected to a three-phase 200V or other commercial AC power supply (not shown), and receives a drive signal Dv and a polarity switching signal Spn (described later) as inputs to perform output control such as inverter control in accordance with the drive signal Dv, switching between electrode positive polarity EP and electrode negative polarity EN in accordance with the polarity switching signal Spn to output an AC welding voltage Vw and welding current Iw suitable for welding. Although not shown, the power control circuit MC includes a primary rectifier circuit that rectifies the AC commercial power supply, a capacitor that smoothes the rectified DC, a primary-side inverter circuit that converts the smoothed DC to high-frequency AC in accordance with the drive signal Dv, an inverter transformer that steps down the high-frequency AC to a voltage value suitable for welding, a secondary rectifier circuit that rectifies the stepped-down high-frequency AC, a reactor that smooths the rectified DC, and a secondary-side inverter circuit that switches the smoothed DC between electrode positive polarity EP and electrode negative polarity EN in accordance with the polarity switching signal Spn.

[0018] The feed motor WM is driven to rotate by a feed control signal Fc, which will be described later. The welding wire 1 is fed forward and backward through the welding torch 4 at a feed speed Fw by the rotation of a 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. 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.

[0019] The welding voltage detection circuit VD detects the AC welding voltage Vw, converts it to an absolute value, and outputs a welding voltage detection signal Vd. The welding voltage averaging circuit VAV averages this 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.

[0020] The pulse period modulation circuit TC receives the voltage error amplified signal Ev, performs PI (proportional-integral) control or PID (proportional-integral-derivative) control, and outputs a base period setting signal Tbr. This circuit performs pulse period modulation control by varying the base period setting signal Tbr 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.

[0021] The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr, and the base current setting circuit IBR outputs a predetermined base current setting signal Ibr.

[0022] 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, and the peak fall period setting circuit TKR outputs a predetermined peak fall period setting signal Tkr.

[0023] The electrode negative polarity period setting circuit TNR outputs a predetermined electrode negative polarity period setting signal Tnr.

[0024] The welding current setting circuit IR receives as input the peak rise period setting signal Tur, the peak period setting signal Tpr, the peak fall setting signal Tkr, the base period setting signal Tbr, the electrode negative polarity period setting signal Tnr, the peak current setting signal Ipr, the base current setting signal Ibr, and an electrode negative polarity current setting signal Inr (described later), 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, a timer signal Tm=1 is output, and the peak rise current Iu, which 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, a timer signal Tm=3 is output, and the peak fall current Ik decreasing 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, the timer signal Tm=4 is output, and the base current setting signal Ibr is output as the welding current setting signal Ir. 5) Subsequently, during the electrode negative polarity period Ten determined by the electrode negative polarity period setting signal Tnr, a timer signal Tm=5 is output, and the electrode negative polarity current setting signal Inr is output as the welding current setting signal Ir, and just before the end of the electrode negative polarity period Ten, a current setting signal Ir that drops to the value of the base current setting signal Ibr is output. 6) Repeat steps 1) to 5) above.

[0025] The polarity switching circuit SPN receives the timer signal Tm as input and outputs a polarity switching signal Spn that is at a high level when the timer signal Tm=1 to 4 (electrode positive polarity Tep) and at a low level when the timer signal Tm=5 (electrode negative polarity period Ten).

[0026] The average feed speed setting circuit FAR outputs a predetermined average feed speed setting signal Far. The feed speed error amplifier circuit EF amplifies the error between the 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.

[0027] The forward feed peak value setting circuit WSR receives the above-mentioned feed speed error amplified 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 forward feed peak value setting signal Wsr having a positive value. The reverse feed peak value setting circuit WRR receives the above-mentioned feed speed error amplified 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 reverse feed peak value setting signal Wsr having a negative value. Only one of the forward feed peak value setting signal Wsr or the reverse feed peak value setting signal Wrr may be variable speed controlled.

[0028] The electrode negative polarity period backward transmission peak value setting circuit WNR outputs an electrode negative polarity period backward transmission peak value setting signal Wnr having a predetermined negative value.

[0029] The welding current detection circuit ID detects the AC welding current Iw, converts it to an absolute value, 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 PWM 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 primary inverter circuit in the power control circuit MC, but does not output the drive signal Dv when the activation signal On is low (welding stops).

[0030] The rising transition period setting circuit TFUR outputs a predetermined rising transition period setting signal Tfur. The value of the rising transition period setting signal Tfur is set to be equal to or less than the value of the peak rising period setting signal Tur. The falling transition period setting circuit TFKR outputs a predetermined falling transition period setting signal Tfkr. The value of the falling transition period setting signal Tfkr is set to be equal to or less than the value of the peak falling period setting signal Tkr.

[0031] The feeding speed setting circuit FR receives the forward feeding peak value setting signal Wsr, the reverse feeding peak value setting signal Wrr, the electrode negative polarity period reverse feeding peak value setting signal Wnr, the timer signal Tm, the rising change period setting signal Tfur, and the falling change period setting signal Tfkr as inputs, performs the following processing, and outputs a feeding speed setting signal Fr. 1) During the rising change period Tfu determined by the rising change period setting signal Tfur from the start of the peak rising period Tu of the timer signal Tm=1, the feeding speed setting signal Fr is output, which changes from the value of the electrode negative polarity period reverse feed peak value setting signal Wnr to the value of the forward feed peak value setting signal Wsr. 2) Subsequently, the forward feed peak value setting signal Wsr is output as the feed speed setting signal Fr until the timer signal Tm=2 (peak period Tp) ends. 3) Subsequently, during the falling change period Tfk determined by the falling change period setting signal Tfkr from the start of the peak falling period Tk of the timer signal Tm=3, the feeding speed setting signal Fr is output, which 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. 4) Subsequently, the reverse feed peak value setting signal Wrr is output as the feed speed setting signal Fr during the period until the timer signal Tm=4 (base period Tb) ends. 5) Subsequently, during the electrode negative polarity Ten of the timer signal Tm=5, the electrode negative polarity period reverse feed peak value setting signal Wnr is output as the feed speed setting signal Fr. 6) Repeat steps 1) to 5) above.

[0032] 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.

[0033] The average feed speed detection circuit FAD receives the 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.

[0034] The electrode negative current ratio calculation circuit RND receives the welding current detection signal Id and the timer signal Tm as inputs, calculates the percentage of the value obtained by integrating the welding current detection signal Id during the electrode negative polarity period Ten of timer signal Tm=5 to the value obtained by integrating the welding current detection signal Id during the pulse period Tf of timer signal Tm=1 to 5, and outputs this as an electrode negative polarity current ratio calculation signal Rnd. Therefore, the electrode negative polarity current ratio Rn [%] is the percentage of the electrode negative polarity current Ien in the average value of the welding current Iw.

[0035] The electrode negative polarity current ratio setting circuit RNR outputs a predetermined electrode negative polarity current ratio setting signal Rnr.

[0036] The electrode negative polarity current setting circuit INR receives the electrode negative polarity current ratio calculation signal Rnd and the electrode negative polarity current ratio setting signal Rnr as inputs, performs modulation control so that both values ​​are equal, and outputs the electrode negative polarity current setting signal Inr.

[0037] 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.

[0038] 2 is a timing chart of each signal in the welding device of FIG. 1, illustrating an AC 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 welding wire feed speed Fw, and (D) in FIG. 2 shows the change over time in polarity switching signal Spn. The operation of each signal will be explained below with reference to the diagram.

[0039] The welding current Iw shown in Fig. 1A and the welding voltage Vw shown in Fig. 1B are positive values ​​above 0 when the electrode has positive polarity EP, and negative values ​​below 0 when the electrode has negative polarity EN. The feed speed Fw shown in Fig. 1C is a forward feed state in which the wire is fed forward in a direction toward the base metal when the feed speed Fw is a positive value above 0, and a reverse feed state in which the wire is fed backward in a direction away from the base metal when the feed speed Fw is a negative value below 0.

[0040] At time t1, as shown in (D) of the figure, the polarity switching signal Spn changes to a high level, and the period from time t1 to t5 becomes an electrode positive polarity period Tep. During a predetermined peak rise period Tu from time t1 to t2, as shown in (A) of the figure, a peak rise current Iu increases from a predetermined base current Ib to a predetermined peak current Ip, and as shown in (B) of the figure, a peak rise voltage increases from a base voltage Vb to a peak voltage Vp is applied between the welding wire and the base metal. During a predetermined rise change period Tfu from time t1 to t11, as shown in (C) of the figure, the feed speed Fw changes from the value of the electrode negative polarity period reverse feed peak value Wn to the value of the forward feed peak value Ws. The start of the rise change period Tfu is synchronized with the start of the peak rise period Tu. The rise change period Tfu is a period that is shorter than the peak rise period Tu. The peak rise period Tu is set by the peak rise period setting signal Tur of FIG. 1. The base current Ib is set by the base current setting signal Ibr of FIG. 1. The peak current Ip is set by the peak current setting signal Ipr of FIG. 1. The rise change period Tfu is set by the rise change period setting signal Tfur of FIG. 1. The electrode negative polarity period reverse transmission peak value Wn is set by the electrode negative polarity period reverse transmission peak value setting signal Wnr of FIG. 1. The forward transmission peak value Ws is set by the forward transmission peak value setting signal Wsr of FIG. 1.

[0041] During a predetermined peak period Tp from time t2 to t3, as shown in FIG. 1(A), a peak current Ip flows, and as shown in FIG. 1(B), a peak voltage Vp is applied between the welding wire and the base metal. During the period from time t11 to t3, as shown in FIG. 1(C), the feed rate Fw is equal to the forward feed peak value Ws. The peak period Tp is set by the peak period setting signal Tpr in FIG. 1.

[0042] During a predetermined peak fall period Tk from time t3 to t4, as shown in FIG. 1A, a peak fall current Ik is applied, decreasing from a peak current Ip to a base current Ib, and as shown in FIG. 1B, a peak fall voltage is applied between the welding wire and the base metal, decreasing from a peak voltage Vp to a base voltage Vb. During a predetermined fall change period Tfk from time t3 to t31, as shown in FIG. 1C, the feed speed Fw changes from the forward feed peak value Ws to the reverse feed peak value Wr. The start of the fall change period Tfk is synchronized with the start of the peak fall period Tk. The fall change period Tfk is a period that is equal to or shorter than the peak fall period Tk. The peak fall period Tk is set by the peak fall period setting signal Tkr in FIG. 1. The fall change period Tfk is set by the fall change period setting signal Tfkr in FIG. 1. The reverse transmission peak value Wr is set by the reverse transmission peak value setting signal Wnr in FIG.

[0043] During a base period Tb controlled by pulse period modulation from time t4 to t5, as shown in FIG. 1(A), a base current Ib flows, and as shown in FIG. 1(B), a base voltage Vb is applied between the welding wire and the base metal. During a period from time t31 to t5, as shown in FIG. 1(C), the feed speed Fw is equal to the reverse feed peak value Wr. The base period Tb is set by a base period setting signal Tbr in FIG. 1.

[0044] At time t5, as shown in FIG. 1D, the polarity switching signal Spn changes to a low level, and the period from time t5 to t6 becomes an electrode negative polarity period Ten. During the predetermined electrode negative polarity period Ten from time t5 to t6, as shown in FIG. 1A, a negative electrode negative polarity current Ien is supplied by current modulation control, and the electrode negative polarity current Ien drops to a negative base current Ib just before the end of the electrode negative polarity period Ten. As shown in FIG. 1B, a negative electrode negative polarity voltage Ven is applied between the welding wire and the base metal. At the same time, as shown in FIG. 1C, the feed speed Fw becomes the electrode negative polarity period reverse feed peak value Wn. Therefore, the welding wire is reverse fed at least during the base period Tb and the electrode negative polarity period Ten. The electrode negative polarity period Ten is set by the electrode negative polarity period setting signal Tnr in FIG. 1. The electrode negative polarity current Ien is set by the electrode negative polarity current setting signal Inr in FIG. 1.

[0045] Numerical examples of the above parameters are shown below. Tu=1ms, Tp=1.5ms, Tk=1ms, Tb=1~4ms, Ten=1.3ms Ip=500A, Ib=50A, Ien=350~500A Tfu=0.5~1ms, Tfk=0.5~1ms Ws=45~55m / min, Wr=-15~-25m / min, Wn=-30m / min

[0046] The effects of this embodiment will be described below. According to this embodiment, in the AC pulse arc welding control method, a welding wire is fed, and during an electrode positive polarity period, a peak rise current that rises from a base current value to a peak current value during a peak rise period is passed, a peak current is passed during the peak period, a peak fall current that falls from the peak current value to the base current value during a peak fall period is passed, a base current is passed during the base period, and an electrode negative polarity current is passed during an electrode negative polarity period, and these current passes are repeated as one pulse period, and the pulse period is modulated and controlled to control the arc length while welding. In this method, the welding wire feed speed alternates between a forward feed peak value and a reverse feed peak value, and is at the reverse feed peak value at least during the base period and the electrode negative polarity period, and the forward feed peak value and / or the reverse feed peak value are variably controlled so that the average value of the feed speed is constant. A droplet is formed at the tip of the welding wire by passing the electrode negative polarity current and the peak current. By feeding the welding wire backward during the subsequent base period, an upward force can be continuously applied to the droplets during the base period, thereby ensuring that the droplets are transferred to the molten pool. As a result, even if the droplet size increases in AC pulse arc welding, a one-droplet-per-pulse-cycle transfer state can be maintained, resulting in good welding quality. Furthermore, since the welding wire is fed backward when droplets are gradually formed by the application of the electrode negative polarity current, the occurrence of a short circuit between the welding wire and the base metal can be suppressed, and a stable welding state can be maintained. Furthermore, even if the pulse period changes moment by moment due to arc length control, the forward feed peak value and / or reverse feed peak value are variably controlled, so the average feed speed remains constant during welding, thereby maintaining good welding quality.

[0047] More preferably, according to this embodiment, the welding wire feed speed starts changing from the reverse feed peak value to the forward feed peak value at the start of the peak rise period, and starts changing from the forward feed peak value to the reverse feed peak value at the start of the peak fall period. By synchronizing the start of the peak rise period with the start of the change from the reverse feed peak value to the forward feed peak value, it is possible to reliably form a droplet of an appropriate size during the peak period. Furthermore, by synchronizing the start of the peak fall period with the start of the change from the forward feed peak value to the reverse feed peak value, a strong upward force can be applied to the droplet, thereby reliably detaching the droplet and transferring it to the molten pool.

[0048] More preferably, in this embodiment, the change period from the forward feed peak value to the reverse feed peak value is equal to or shorter than the peak fall period, so that the upward force acting on the droplet can be further strengthened, and the droplet can be more reliably separated and transferred to the molten pool.

[0049] More preferably, according to this embodiment, the absolute value of the reverse feed peak value is set to a value greater than that during the electrode negative polarity period, thereby more reliably preventing a short circuit between the welding wire and the base metal during the electrode negative polarity period.

[0050] More preferably, according to this embodiment, the electrode negative polarity current ratio is maintained at a set value by modulating and controlling the electrode negative polarity current. When the pulse period is modulated and controlled, the electrode negative polarity current ratio changes. In this case, the electrode negative polarity current ratio can be maintained at a set value by modulating and controlling the electrode negative polarity current. As a result, it is possible to suppress fluctuations in the electrode negative polarity current ratio and thus fluctuations in the bead appearance and penetration shape. [Explanation of symbols]

[0051] 1 welding wire 2 Base material 3. Arc 4 welding torches 5 Feeding roll DV drive circuit Dv drive signal EF Feed speed error amplifier circuit Ef Feed speed error amplification signal EI current error amplifier circuit Ei Current error amplification signal EV voltage error amplifier circuit Ev Voltage error amplified signal FAD average feed 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 Feeding speed Ib Base current IBR base current setting circuit Ibr Base current setting signal ID welding current detection circuit Id Welding current detection signal Ien Electrode negative polarity current Ik Peak falling current InR Electrode negative polarity current setting circuit Inr Electrode negative polarity current setting signal 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 rising current Iw Welding current MC power control circuit On Start signal PS welding power source RC robot controller Rn Electrode negative polarity current ratio RND Electrode negative polarity current ratio calculation circuit Rnd Electrode negative polarity current ratio calculation signal RNR Electrode negative polarity current ratio setting circuit Rnr Electrode negative polarity current ratio setting signal SPN polarity switching circuit SPN polarity switching signal Tb base period Tbr Base period setting signal TC Pulse Period Modulation Circuit Ten electrode negative polarity period Tep electrode positive polarity period 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 Fall Period TKR Peak fall period setting circuit Tkr Peak fall period setting signal TNR electrode negative polarity period setting circuit Tnr Electrode negative polarity period setting signal Tp peak period TPR peak period setting circuit Tpr Peak period setting signal Tu Peak rise 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 Vp Peak voltage VR welding voltage setting circuit Vr Welding voltage setting signal Vw welding voltage WM feed motor Wn electrode negative polarity period reverse peak value WNR electrode negative polarity period reverse peak value setting circuit Wnr Electrode negative polarity period reverse peak value setting signal Wr Reverse transport peak value WRR reverse transmission peak value setting circuit Wrr Reverse transmission peak value setting signal Ws forward peak value WSR forward peak value setting circuit Wsr Forward transmission peak value setting signal

Claims

1. Feed the welding wire; In the electrode positive polarity period, a peak rise current that rises from a base current value to a peak current value is passed during a peak rise period, the peak current is passed during the peak period, a peak fall current that falls from the peak current value to the base current value is passed during a peak fall period, the base current is passed during the base period, and an electrode negative polarity current is passed during the electrode negative polarity period, and these passes are repeated as one pulse period; In the AC pulse arc welding control method, the arc length is controlled by modulating the pulse period, and welding is performed by controlling the arc length. the welding wire feed speed alternates between a forward feed peak value and a reverse feed peak value, and is at the reverse feed peak value at least during the base period and the electrode negative polarity period; The forward feed peak value and / or the reverse feed peak value are variably controlled so that the average value of the feed speed is constant.

1. A method for controlling AC pulse arc welding.

2. The welding wire feed speed is a change from the reverse transport peak value to the forward transport peak value at a start of the peak rise period; a change from the forward transport peak value to the reverse transport peak value at a start of the peak fall period; 2. The method for controlling AC pulse arc welding according to claim 1.

3. a transition period from the forward transport peak value to the reverse transport peak value is equal to or shorter than the peak fall period; 3. The method for controlling AC pulse arc welding according to claim 2.

4. the absolute value of the reverse transport peak value is set to a value greater during the electrode negative polarity period than during the base period; 4. The method for controlling AC pulse arc welding according to claim 3.

5. The electrode negative polarity current ratio is maintained at a set value by modulating and controlling the electrode negative polarity current.

5. The AC pulse arc welding control method according to claim 1, wherein the AC pulse arc welding control method is a method for controlling an AC pulse arc welding.

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