JP2014024077A - Pulse arc welding control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a stable droplet transfer state even when an external inductance value is large in pulse arc welding.SOLUTION: In a pulse arc welding control method, a welding current Iw is applied in such a way as to rise from a base current Ib to a peak current Ip during a peak rising period Tu, become the peak current Ip during a peak period Tp, fall from the peak current Ip to the base current Ib during a peak falling period Td, and become the base current Ib during a base period Tb. A rising rate of the welding current Iw during the peak rising period Tu is detected. When the rising rate is equal to or higher than a reference rate, the peak current Ip is set to a standard peak current value Ips. When the rising rate is lower than the reference rate, the peak current Ip is set to an increased peak current value Iph larger than the standard peak current value Ips. When an external inductance value is large, the peak current Ip is increased, and a pinch force becomes strong, so that a droplet transfer state is stabilized.

Description

  The present invention relates to a pulse arc welding control method capable of stabilizing a droplet transfer state even when an external inductance value by a welding cable is large.

  FIG. 4 is a general current / voltage waveform diagram of consumable electrode pulse arc welding. FIG. 4A shows the time change of the welding current setting signal Ir, FIG. 4B shows the time change of the welding current Iw, and FIG. 4C shows the time change of the welding voltage Vw. The welding current setting signal Ir is a signal for setting the welding current Iw. The welding current Iw is a current for energizing the arc, and the welding voltage Vw is a voltage applied between the welding wire and the base material. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 5A, the welding current setting signal Ir becomes a value that rises from the base current setting value Ibr to the peak current setting value Ipr during a predetermined peak rising period Tu at times t1 to t2, and then continues. During the peak period Tp from time t2 to t3, the peak current set value Ipr is reached. Subsequently, during the predetermined peak falling period Td from time t3 to t4, the peak current set value Ipr decreases to the base current set value Ibr. Then, during the base period Tb from time t4 to t5, the base current set value Ibr is obtained. Corresponding to the value of the welding current setting signal Ir, as shown in FIG. 5B, during the peak rising period Tu, a transition current rising from the base current Ib to the peak current Ip is energized. During the peak period Tp, the peak current Ip is energized. Subsequently, during the peak fall period Td, a transition current that decreases from the peak current Ip to the base current Ib is energized, and subsequently during the base period Tb. Is supplied with a base current Ib. Corresponding to the energization of these welding currents, as shown in FIG. 5C, during the peak rising period Tu, a transition voltage rising from the base voltage Vb to the peak voltage Vp is applied, and then the above-mentioned During the peak period Tp, the peak voltage Vp is applied. Subsequently, during the peak falling period Td, a transition voltage falling from the peak voltage Vp to the base voltage Vb is applied, and subsequently, the base period Tb described above. During this, the base voltage Vb is applied. The welding is performed by repeating the period from the time t1 to the time t5 as the pulse period Tf.

  In consumable electrode arc welding, maintaining the arc length during welding at an appropriate value is important for obtaining good welding quality. The arc length is proportional to the average value of the welding voltage Vw. Therefore, in order to maintain the arc length at an appropriate value, the pulse period Tf is fed back so that the average value of the welding voltage Vw becomes equal to the predetermined voltage setting value Vr, as shown in FIG. Control (arc length control). The average value of the welding voltage Vw is generated by passing the detected value of the welding voltage Vw through a low-pass filter (cutoff frequency of about 1 to 10 Hz).

  The numerical example described below is a case where the welding wire is a steel wire having a diameter of 1.2 mm. The base current Ib is set to about 20 to 70 A, which is a small current value less than the critical value, so as not to melt the welding wire. The peak current Ip is set to about 450 to 550 A, which is a large current value greater than the critical value, in order to melt the welding wire. The peak rising period Tu and the peak falling period Td are set so that the change in arc force accompanying the change in the welding current Iw is optimized and the bead appearance is improved. Both values are set to about 0.4 to 1.0 ms. Said peak period Tp is set as follows so that it may become a stable droplet transfer state of 1 droplet period 1 droplet transfer. When the welding current Iw is integrated from the beginning of the peak rising period Tu, and when the integrated value Si = ∫Iw · dt reaches a predetermined reference value St during the peak period Tp after the peak rising period Tu has elapsed, The peak period Tp ends and the peak falling period Td is entered. Hereinafter, this control is referred to as variable peak period control (see Patent Document 1). When this integrated value Si is equal to the reference value St, the amount of heat input to the welding wire becomes a constant value, so that a droplet of an appropriate size is formed during the peak period Tp, and during the peak falling period Td or the base period Tb. The droplets move to the molten pool. For example, when the reference value St is set to 630 (a.ms), the peak period Tp at that time is 1.2 ms. There is a certain range in the reference value St at which one droplet period and one droplet transfer state are achieved. The peak current Ip and the reference value St are set so that the droplet transfer state becomes one droplet cycle one droplet transfer state according to the material, diameter, etc. of the welding wire.

  The external inductance value depends on the length of the reciprocating welding cable, which is the sum of the welding cable that connects the positive output terminal of the welding power source and the welding torch, and the welding cable that connects the negative output terminal of the welding power source and the base metal, and the routing condition. Big and small are decided. As the length of the reciprocating welding cable increases, the external inductance value increases. Further, when the reciprocating welding cable is routed in a large circle, the external inductance value increases. In pulse arc welding, since the change in current becomes gentle as the external inductance value increases, it becomes impossible to maintain the pulse waveform of the welding current Iw as shown in FIG. That is, the rising speed of the welding current Iw during the peak rising period Tu becomes moderate, and the welding current Iw has not yet reached the peak current Ip even at time t2 when the peak rising period Tu ends. When the peak period Tp is set to a predetermined value, the integrated value Si during the peak rising period Tu and the peak period Tp decreases as the external inductance value increases. As a result, the amount of heat input to the welding wire is reduced, and droplets cannot be sufficiently formed, and the one-pulse cycle / one droplet transfer state cannot be maintained. In order to solve this problem, as described above, the peak period variable control is performed so that the peak period Tp ends when the integrated value Si reaches the reference value St.

  Even if the external inductance value is a large value, the welding quality is not extremely deteriorated because the peak period variable control is performed. However, there is no doubt that the quality of the welding becomes a requirement when the external inductance value is small. For this reason, when constructing a welding apparatus for pulse arc welding, care is taken so that the length of the reciprocating welding cable is as short as possible and that the external inductance value is also reduced in the routing of the welding cable. However, there are cases where the external inductance value inevitably increases due to restrictions on the layout in the factory. Also, when the work is a large structure, the external inductance value may increase. In such a case, the waveform of the welding current Iw cannot maintain the waveform of FIG. Hereinafter, the current / voltage waveforms in such a state will be described.

  FIG. 5 is a current / voltage waveform diagram of consumable electrode pulse arc welding when the external inductance value is large. FIG. 4A shows the time change of the welding current setting signal Ir, FIG. 4B shows the time change of the welding current Iw, and FIG. 4C shows the time change of the welding voltage Vw. This figure corresponds to FIG. 4 described above. Hereinafter, a description will be given with reference to FIG.

  During the peak rising period Tu from time t1 to t2, the welding current setting signal Ir is a value that rises from the base current setting value Ibr to the peak current setting value Ipr as in FIG. 4, as shown in FIG. Become. As shown in FIG. 5B, the welding current Iw increases from the base current value Ib at a slower rate than in FIG. 4, and has not yet reached the peak current value Ip at time t2. As shown in FIG. 4C, the welding voltage Vw rises from the base voltage value Vb at a slower rate than in FIG. 4, and has not yet reached the peak voltage value Vp at time t2.

  When the peak rising period Tu ends at time t2, the welding current setting signal Ir is maintained at the peak current setting value Ipr as shown in FIG. As shown in FIG. 5B, the welding current Iw continues to rise from time t2, reaches the peak current value Ip at time t21, and thereafter maintains the peak current value Ip. As shown in FIG. 5C, the welding voltage Vw continues to rise from time t2, reaches the peak voltage value Vp at time t21, and thereafter maintains the peak voltage value Vp.

  The peak period Tp ends (peak period variable control) at time t3 when the integrated value Si of the welding current Iw from the start point (time t1) of the peak rising period Tu reaches the reference value St. When the peak period Tp ends at time t3, during the peak falling period Td from time t3 to t4, the welding current setting signal Ir is changed from the peak current setting value Ipr to the base current setting value Ibr as shown in FIG. The value descends to. As shown in FIG. 5B, the welding current Iw decreases from the peak current value Ip at a slower rate than in FIG. 4, and has not yet reached the base current value Ib at time t4. As shown in FIG. 5C, the welding voltage Vw decreases from the peak voltage value Vp at a slower rate than in FIG. 4, and has not yet reached the base voltage value Vb at time t4.

  When the peak falling period Td ends at time t4, the welding current setting signal Ir is maintained at the base current setting value Ibr until time t5 when the pulse period ends, as shown in FIG. As shown in FIG. 5B, the welding current Iw continues to decrease from time t4, reaches the base current value Ib at time t41, and thereafter maintains the base current value Ib until time t5. As shown in FIG. 5C, the welding voltage Vw continues to decrease from time t4, reaches the base voltage value Vb at time t41, and thereafter maintains the base voltage value Vb until time t5.

  The time lengths of the peak rising period Tu from time t1 to t2 and the peak falling period Td from time t3 to t4 are the same as those in FIG. However, the time length of the peak period Tp at times t2 to t3 is longer than that in FIG. 4 because the peak period variable control operates. Even if the external inductance value changes, the amount of heat input to the welding wire becomes a constant value by this variable control during the peak period, so that one droplet period 1 droplet transfer state can be substantially maintained.

JP 2003-285163 A

  As described above, in the conventional variable peak period control, the amount of heat input to the welding wire can be maintained at an appropriate value even when the external inductance value is large. Drop transfer state. However, even when the peak period variable control is performed, as the external inductance value increases, the droplet transfer state sometimes becomes an unstable state that deviates from the one-pulse cycle 1 droplet transfer state. This frequency increases as the external inductance value increases.

  Therefore, an object of the present invention is to provide a pulse arc welding control method capable of reducing the frequency at which the droplet transfer state deviates from the one-pulse period 1 droplet transfer state even when the external inductance value increases. .

In order to solve the above-described problem, the invention of claim 1 is characterized in that the welding wire is fed and the transition current rising from the base current to the peak current is continuously supplied during the peak rising period and the peak current is supplied during the peak period. During the peak fall period, the transition current descending from the peak current to the base current is continuously applied, and the base current is supplied during the base period, and the welding current is supplied in a pulse cycle. As repeatedly energized,
In the pulse arc welding control method for transitioning from the peak period to the peak falling period when the integral value of the welding current during the peak rising period and the peak period reaches a predetermined reference value,
The rising speed of the welding current during the peak rising period is detected, and when the rising speed is equal to or higher than a predetermined reference speed, the peak current is set to a predetermined standard peak current value, and when the rising speed is lower than the reference speed, Setting the peak current to a predetermined increased peak current value greater than the standard peak current value;
It is the pulse arc welding control method characterized by this.

In the invention of claim 2, the ascending speed is a differential value of the welding current.
The pulse arc welding control method according to claim 1, wherein:

In the invention of claim 3, the rising speed is a value of the welding current at a time point when the peak rising period ends.
The pulse arc welding control method according to claim 1, wherein:

Invention of Claim 4 changes the said increase peak electric current value according to the said raise speed,
It is the pulse arc welding control method of any one of Claims 1-3 characterized by the above-mentioned.

  When the external inductance value is large, the rate of current increase is moderate, but the amount of heat input to the welding wire becomes a constant value by the peak period variable control. However, the heat input process varies depending on the rate of current increase. For this reason, the shape of the droplets varies as the rising speed becomes slower. As a result, the droplet transfer state sometimes deviates from the one-pulse cycle 1 droplet transfer state. At this time, if the peak current value is increased, even if the shape of the droplet varies, the pinch force becomes strong, so that the droplet can be detached. For this reason, according to the present invention, the frequency at which the droplet transfer state deviates from the one-pulse cycle 1 droplet transfer state can be reduced even if the ascending speed becomes slow.

It is an electric current / voltage waveform diagram which shows the pulse arc welding control method which concerns on embodiment of this invention when an external inductance value is large. In embodiment of this invention, it is a figure which shows the change of increase value (DELTA) Iph of the peak current with respect to the difference (Bt-Bd) of a reference speed and a raise speed. It is a block diagram of the welding power source for implementing the pulse arc welding control method concerning an embodiment of the invention. It is a general current and voltage waveform diagram of consumable electrode pulse arc welding in the prior art. In a prior art, it is an electric current and voltage waveform figure of consumable electrode pulse arc welding when an external inductance value is large.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a current / voltage waveform diagram showing a pulse arc welding control method according to an embodiment of the present invention when the external inductance value is large. FIG. 4A shows the time change of the welding current setting signal Ir, FIG. 4B shows the time change of the welding current Iw, and FIG. 4C shows the time change of the welding voltage Vw. This figure shows a case where the rising speed Bd of the welding current Iw during the peak rising period Tu is less than the reference speed Bt because the external inductance value is large. This figure corresponds to FIG. 5 described above. In the figure, the standard peak current set value Ips is the same as the peak current set value Ipr shown in FIGS. Hereinafter, a description will be given with reference to FIG.

  The operation during the peak rising period Tu at times t1 to t2 is the same as that in FIG. As shown in FIG. 6A, the welding current setting signal Ir has a value that rises from a predetermined base current setting value Ibr to a predetermined standard peak current setting value Ips. As shown in FIG. 5B, the welding current Iw rises from the base current value Ib at a slower rate than in FIG. 4, and still reaches the peak current value Ip corresponding to the standard peak current set value Ips at time t2. Has not reached. As shown in FIG. 4C, the welding voltage Vw rises from the base voltage value Vb at a slower rate than in FIG. 4, and has not yet reached the peak voltage value Vp at time t2. During this peak rising period Tu, the rising speed Bd of the welding current Iw is detected. This detection method will be described later.

  When the peak rising period Tu ends at time t2, the detected ascending speed Bd is compared with a predetermined reference speed Bt. When Bd ≧ Bt, the welding current setting signal Ir is set to the standard peak current setting value Ips. When Bd <Bt, it is set to a predetermined increase peak current set value Iph. Here, Iph> Ips. A method for setting the increased peak current set value Iph will be described later. Since this figure is a case where Bd <Bt, as shown in FIG. 11A, the welding current setting signal Ir increases to the increased peak current setting value Iph at time t2. As shown in FIG. 5B, the welding current Iw continues to increase from time t2, and the peak current value Ip is increased, so that the increase is made at time t22 later than time t21 in FIG. The peak current value Ip corresponding to the peak current set value Iph is reached, and thereafter the peak current value Ip is maintained. As shown in FIG. 6C, the welding voltage Vw continues to rise from time t2, reaches the peak voltage value Vp at time t22, and thereafter maintains the peak voltage value Vp. That is, the peak current value Ip is increased when Bd <Bt than when Bd ≧ Bt.

  The peak period Tp ends (peak period variable control) at time t3 when the integrated value Si of the welding current Iw from the start point (time t1) of the peak rising period Tu reaches the reference value St. When the peak period Tp ends at time t3, the peak falling period Td from time t3 to t4 starts. The operation during this period is the same as in FIG. As shown in FIG. 6A, the welding current setting signal Ir has a value that decreases from the increased peak current setting value Iph to the base current setting value Ibr. As shown in FIG. 5B, the welding current Iw decreases from the peak current value Ip at a slower rate than in FIG. 4, and has not yet reached the base current value Ib at time t4. As shown in FIG. 5C, the welding voltage Vw decreases from the peak voltage value Vp at a slower rate than in FIG. 4, and has not yet reached the base voltage value Vb at time t4.

  When the peak falling period Td ends at time t4, the base period Tb starts. The operation during this period is the same as in FIG. As shown in FIG. 6A, the welding current setting signal Ir is maintained at the base current setting value Ibr. As shown in FIG. 5B, the welding current Iw continues to decrease from time t4 and reaches the base current value Ib at time t42 later than time t41 in FIG. 5 because the peak current value Ip is large. Thereafter, the base current value Ib is maintained. As shown in FIG. 5C, the welding voltage Vw continues to decrease from time t4, reaches the base voltage value Vb at time t42, and thereafter maintains the base voltage value Vb.

  The time lengths of the peak rising period Tu from time t1 to t2 and the peak falling period Td from time t3 to t4 are the same as those in FIG. However, the time length of the peak period Tp at times t2 to t3 is longer than that in FIG. 4 because the peak period variable control operates.

  The current / voltage waveforms when the external inductance value is small and the ascending speed Bd is equal to or higher than the reference speed Bt are substantially the same as those in FIG. The reason why they are substantially the same is that a case where the welding current Iw does not reach the peak current value Ip only slightly at the end of the peak rising period Tu is included. The current waveform in FIG. 4B is a current waveform that is originally set.

The detection of the rising speed Bd of the welding current Iw during the peak rising period Tu described above is performed as follows.
(1) A differential value of the welding current Iw is calculated and set as a rising speed Bd. The reference speed Bt in this case is set with reference to FIG. 4B, which is a current waveform when the external inductance value is small. For example, in FIG. 4B, when Ib = 50 A, Ip = 450 A, and Tu = 0.5 ms, the ascending speed is 80 A / 100 μs. With this as a reference, the reference speed Bt = 80 × 90% = 72 A / 100 μs is set. The percentage is set to about 80 to 95%.

(2) The value of the welding current Iw at the time when the peak rising period Tu ends is set as a rising speed Bd. The reference speed Bt in this case is also set with reference to the current waveform in FIG. 4 (B. In the above numerical example, the reference speed Bt = 450 A × 90% = 405 A is set. The percentage is about 80 to 95%. Set.

Next, a method for setting the increased peak current set value Iph will be described.
(1) The increased peak current set value Iph is set as a value obtained by adding a predetermined value to the standard peak current set value Ips. The predetermined value is about 50 to 100A.

(2) The increase peak current set value Iph is set as a value obtained by adding the increase value ΔIph to the standard peak current set value Ips. The increase value ΔIph is a value proportional to the difference (Bt−Bd) between the reference speed Bt and the ascending speed Bd. An example is shown in FIG. The horizontal axis of the figure shows (Bt−Bd), which is in the range of 0 to 40 A / 100 μs. The vertical axis represents the increase value ΔIph, which is in the range of 0 to 100A. This figure shows the case where the method of detecting the ascending speed Bd is the item (1) described above. As shown in the figure, ΔIph = 30A when (Bt−Bd) = 0, ΔIph = 80 when (Bt−Bd) = 30, and ΔIph = 80 when (Bt−Bd) = 40. It is. In the figure, it is a polygonal line, but it may be changed to a curved line or a staircase.

FIG. 3 is a block diagram of a welding power source for carrying out the pulse arc welding control method according to the above-described embodiment of the present invention. In the figure, the block for controlling the feeding of the welding wire is omitted. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200 V, performs output control such as inverter control in accordance with a current error amplification signal EI described later, and outputs a welding voltage Vw and a welding current Iw. The power supply main circuit PM includes a primary rectifier that rectifies commercial power, a smoothing capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current to high frequency alternating current, and the high frequency alternating current to a voltage value suitable for arc welding. A step-down high-frequency transformer, a secondary rectifier that rectifies the stepped-down high-frequency alternating current, a reactor that smoothes the rectified direct current, a modulation circuit that performs pulse width modulation control using the current error amplification signal EI as an input, and a pulse width-modulated signal And a drive circuit for driving the above inverter circuit. The wire feeder WF feeds the welding wire 1 by rotationally driving a built-in wire feeding motor. The welding wire 1 is fed through the welding torch 4 by the wire feeder WF, and an arc 3 is generated between the welding wire 1 and the base material 2 to perform welding. A welding current Iw is passed through the arc 3, and a welding voltage Vw is applied between the welding wire 1 and the base material 2.

  The voltage detection circuit VD detects the welding voltage Vw, calculates the average value through a low-pass filter, and outputs a voltage detection signal Vav. The welding voltage setting circuit VR outputs a predetermined welding voltage setting signal Vr. The voltage error amplification circuit EV amplifies an error between the welding voltage setting signal Vr and the voltage detection signal Vav, and outputs a voltage error amplification signal Ev. The voltage / frequency conversion circuit VF converts the frequency according to the voltage error amplification signal Ev and outputs a pulse period signal Tfs that changes to a high level for a short time every pulse period Tf.

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The peak period variable control circuit CTP receives the current detection signal Id and a period switching signal Ct, which will be described later, and starts integration of the current detection signal Id from the time when it changes to Ct = 1 (peak rising period), and Ct = 2. When the integral value reaches a predetermined reference value during the (peak period), a peak period end signal Ctp that changes to high level for a short time is output, and the integral value is reset to zero.

  The period switching circuit CT receives the pulse period signal Tfs and the peak period end signal Ctp as an input, and when the pulse period signal Tfs changes to a high level, its value becomes 1, and then a predetermined peak rising period is reached. When the time has elapsed, the value becomes 2, when the peak period end signal Ctp changes to High level, the value becomes 3, and then when the predetermined peak falling period has elapsed, the value becomes 4. The signal Ct is output. Therefore, the period switching signal Ct is a signal that is 1 during the peak rising period, 2 during the peak period, 3 during the peak falling period, and 4 during the base period.

  The rising speed detection circuit BD receives the current detection signal Id and the period switching signal Ct, detects the rising speed of the current detection signal Id when Ct = 1 (peak rising period), and detects the rising speed. The signal Bd is output. The method for detecting the rising speed is as described above. The comparison circuit CM receives this rising speed detection signal Bd and compares it with a predetermined reference speed Bt, and outputs a comparison signal Cm that is at a high level when Bd <Bt and is at a low level when Bd ≧ Bt. To do.

  The standard peak current setting circuit IPS outputs a predetermined standard peak current setting signal Ips. The increased peak current setting circuit IPH outputs the increased peak current setting signal Iph set by the above-described setting method with the standard peak current setting signal Ips and the rising speed detection signal Bd as inputs. The peak current setting circuit IPR receives the standard peak current setting signal Ips, the increased peak current setting signal Iph, and the comparison signal Cm, and is standard when Cm = Low level (the rising speed is equal to or higher than the reference speed). The peak current setting signal Ips is output as the peak current setting signal Ipr, and when the level is High (the rising speed is less than the reference speed), the increased peak current setting signal Iph is output as the peak current setting signal Ipr.

  The base current setting circuit IBR outputs a predetermined base current setting signal Ibr. The welding current setting circuit IR receives the base current setting signal Ibr, the peak current setting signal Ipr and the period switching signal Ct as inputs, and when Ct = 1 (peak rising period), the peak is generated from the base current setting signal Ibr. The value increases to the current setting signal Ipr. When Ct = 2 (peak period), the value is the peak current setting signal Ipr. When Ct = 3 (peak falling period), the base current is changed from the peak current setting signal Ipr. The value decreases to the setting signal Ibr, and when Ct = 4 (base period), the welding current setting signal Ir that is the value of the base current setting signal Ibr is output.

  The current error amplification circuit EI amplifies an error between the welding current setting signal Ir and the current detection signal Id, and outputs a current error amplification signal EI. By these circuit blocks, the welding current Iw described above with reference to FIGS. 1 and 4 is applied.

  According to the above-described embodiment, the rising speed of the welding current during the peak rising period is detected, and when the rising speed is equal to or higher than a predetermined reference speed, the peak current is set to a predetermined standard peak current value, When the speed is less than the reference speed, the peak current is set to a predetermined increased peak current value that is larger than the standard peak current value. In this way, when the rising speed becomes less than the reference speed due to the large external inductance value, the peak current value increases to the increased peak current value. When the external inductance value is large, the rate of current increase is moderate, but the amount of heat input to the welding wire becomes a constant value by the peak period variable control. However, the heat input process varies depending on the rate of current increase. For this reason, the shape of the droplets varies as the rising speed becomes slower. As a result, the droplet transfer state sometimes deviates from the one-pulse cycle 1 droplet transfer state. At this time, if the peak current value is increased, even if the shape of the droplet varies, the pinch force becomes strong, so that the droplet can be detached. For this reason, even if the rising speed becomes slow, the frequency at which the droplet transfer state deviates from the one-pulse cycle 1 droplet transfer state can be reduced. On the other hand, when the external inductance value is small and the rising speed is equal to or higher than the reference speed, the welding current waveform is substantially as set. In this case, even if the peak current value remains the standard peak current value, the amount of heat input to the welding wire and the heat input process are both constant, so the droplet transfer state is changed from the one-pulse cycle 1 droplet transfer state. The frequency of detachment is originally low.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch BD Ascent speed detection circuit Bd Ascent speed (detection signal)
Bt reference speed CM comparison circuit Cm comparison signal CT period switching circuit Ct period switching signal CTP peak period variable control circuit Ctp peak period end signal EI current error amplification circuit EI current error amplification signal EV voltage error amplification circuit Ev voltage error amplification signal Ib base Current IBR Base current setting circuit Ibr Base current setting signal ID Current detection circuit Id Current detection signal Ip Peak current IPH Increase peak current setting circuit Iph Increase peak current setting signal IPR Peak current setting circuit Ipr Peak current setting signal IPS Standard peak current setting circuit Ips standard peak current setting signal IR welding current setting circuit Ir welding current setting signal Iw welding current PM power supply main circuit Si integrated value St reference value Tb base period Td peak falling period Tf pulse period Tfs pulse period signal Tp peak period Tu peak rising Period Vav Voltage detection signal Vb Base voltage VD Voltage detection circuit VF Voltage / frequency conversion circuit Vp Peak voltage VR Welding voltage setting circuit Vr Welding voltage setting signal Vw Welding voltage WF Wire feeder ΔIph Increase value

Even if the external inductance value is a large value, the welding quality is not extremely deteriorated because the peak period variable control is performed. However, it external inductance value is small, it is no doubt that the welding quality is improved. For this reason, when constructing a welding apparatus for pulse arc welding, care is taken so that the length of the reciprocating welding cable is as short as possible and that the external inductance value is also reduced in the routing of the welding cable. However, there are cases where the external inductance value inevitably increases due to restrictions on the layout in the factory. Also, when the work is a large structure, the external inductance value may increase. In such a case, the waveform of the welding current Iw cannot maintain the waveform of FIG. Hereinafter, the current / voltage waveforms in such a state will be described.

(2) The value of the welding current Iw at the time when the peak rising period Tu ends is set as a rising speed Bd. Reference speed Bt in this case is also set on the basis of the current waveform in FIG. 4 (B). In the above numerical example, the reference speed Bt = 450 A × 90% = 405 A is set. The percentage is set to about 80 to 95%.

The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200 V, performs output control such as inverter control according to a current error amplification signal Ei described later, and outputs a welding voltage Vw and a welding current Iw. The power supply main circuit PM includes a primary rectifier that rectifies commercial power, a smoothing capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current to high frequency alternating current, and the high frequency alternating current to a voltage value suitable for arc welding. A step-down high-frequency transformer, a secondary rectifier that rectifies the stepped-down high-frequency alternating current, a reactor that smoothes the rectified direct current, a modulation circuit that performs pulse width modulation control using the current error amplification signal Ei as an input, and a pulse width-modulated signal And a drive circuit for driving the above inverter circuit. The wire feeder WF feeds the welding wire 1 by rotationally driving a built-in wire feeding motor. The welding wire 1 is fed through the welding torch 4 by the wire feeder WF, and an arc 3 is generated between the welding wire 1 and the base material 2 to perform welding. A welding current Iw is passed through the arc 3, and a welding voltage Vw is applied between the welding wire 1 and the base material 2.

The current error amplification circuit EI amplifies an error between the welding current setting signal Ir and the current detection signal Id, and outputs a current error amplification signal Ei . By these circuit blocks, the welding current Iw described above with reference to FIGS. 1 and 4 is applied.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch BD Ascent speed detection circuit Bd Ascent speed (detection signal)
Bt Reference speed CM Comparison circuit Cm Comparison signal CT Period switching circuit Ct Period switching signal CTP Peak period variable control circuit Ctp Peak period end signal EI Current error amplifier circuit
Ei Current error amplification signal EV Voltage error amplification circuit Ev Voltage error amplification signal Ib Base current IBR Base current setting circuit Ibr Base current setting signal ID Current detection circuit Id Current detection signal Ip Peak current IPH Increase peak current setting circuit Iph Increase peak current setting Signal IPR Peak current setting circuit Ipr Peak current setting signal IPS Standard peak current setting circuit Ips Standard peak current setting signal IR Welding current setting circuit Ir Welding current setting signal Iw Welding current PM Power supply main circuit Si Integral value St Reference value Tb Base period Td Peak falling period Tf Pulse period Tfs Pulse period signal Tp Peak period Tu Peak rising period Vav Voltage detection signal Vb Base voltage VD Voltage detection circuit VF Voltage / frequency conversion circuit Vp Peak voltage VR Welding voltage setting circuit Vr Welding voltage setting signal Vw Welding Voltage WF I hate feeding machine ΔIph increase value

Claims (4)

The welding wire is fed, and during the peak rise period, the transition current rising from the base current to the peak current is continuously supplied, the peak current is continuously supplied during the peak period, and the peak current is supplied during the peak fall period. The base current continues to be passed through the transition current falling from the base current to the base current, and the welding current is repeatedly applied as a pulse period,
In the pulse arc welding control method for transitioning from the peak period to the peak falling period when the integral value of the welding current during the peak rising period and the peak period reaches a predetermined reference value,
The rising speed of the welding current during the peak rising period is detected, and when the rising speed is equal to or higher than a predetermined reference speed, the peak current is set to a predetermined standard peak current value, and when the rising speed is lower than the reference speed, Setting the peak current to a predetermined increased peak current value greater than the standard peak current value;
The pulse arc welding control method characterized by the above-mentioned. The rising speed is a differential value of the welding current,
The pulse arc welding control method according to claim 1. The ascending speed is the value of the welding current at the time when the peak rising period ends.
The pulse arc welding control method according to claim 1. Changing the increase peak current value according to the rising speed;
The pulse arc welding control method according to any one of claims 1 to 3, wherein:

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