JP2012006020A - Arc welding control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress much generation of sputter as overheating and formation of a huge size of a droplet proceed since an arc period Ta becomes too long.SOLUTION: In an arc welding control method where a welding wire is fed and the arc period Ta and a short circuit period Ts are repeated to carry out welding, the welding wire is forwardly fed with a predetermined first forward feed speed Ffs1 during a first arc period Ta1 where the arc period Ta is shorter than a predetermined reference period, the welding wire is forwardly fed with a predetermined second forward feed speed Ffs2 during a second arc period Ta2 where the arc period Ta is equal to or longer than the reference period, and the second forward feed speed Ffs2 is set higher than the first forward feed speed Ffs1. A short circuit is smoothly generated by accelerating the forward feed speed, and the prolongation of the arc period Ta is suppressed.

Description

  The present invention relates to an arc welding control method for feeding a welding wire and repeatedly welding an arc period and a short-circuit period.

  Examples of the arc welding method that repeats the arc period and the short circuit period include a carbon dioxide arc welding method, a mag welding method, and a MIG welding method. Further, as the droplet transfer mode, there are a short-circuit transfer mode, a bromule transfer mode with a short circuit, a spray transfer mode with a short circuit, and the like. In these welding methods, the welding wire is fed forward at a constant feeding speed, and welding is performed by repeating the arc period and the short-circuit period. There is also a method of performing welding by feeding a welding wire forward during an arc period and performing backward feeding during a short circuit period (see, for example, Patent Document 1). Hereinafter, this conventional technique for retracting and feeding the welding wire during the short circuit will be described.

  FIG. 4 is an output waveform diagram showing a conventional arc welding control method. (A) shows the welding voltage Vw, (B) shows the welding current Iw, (C) shows the feed speed setting signal Fr, and (D) shows the actual welding wire tip. The feeding speed Fs is shown. When the feed speed setting signal Fr and the feed speed Fs are positive values, they indicate forward feed, and when they are negative values, they indicate reverse feed. Hereinafter, a description will be given with reference to FIG.

  In the figure, the period from time t1 to t2 is the (n-1) th arc period Ta (n-1), and the period from time t2 to t3 is the n-1th short-circuit period Ts (n-1). Yes, the period from time t3 to t4 is the nth arc period Ta (n), and the period from time t4 to t5 is the nth short circuit period Ts (n). Here, if the reference period Tt is a predetermined value, Ta (n-1) <Tt and Ta (n)> Tt. A period in which the arc period is less than the reference period Tt is referred to as a first arc period Ta1, and a period longer than the reference period Tt is referred to as a second arc period Ta2. In this way, a short circuit occurs during the first arc period Ta1 during the (n-1) th arc period Ta (n-1) from time t1 to t2. The n-th arc period Ta (n) from time t3 to t4 is formed by a first arc period Ta1 from time t3 to t32 and a second arc period Ta2 from time t32 to t4.

  During the arc period Ta (n-1) from time t1 to t2, as shown in FIG. 5C, the value of the feed speed setting signal Fr is a first positive feed speed setting value that is a predetermined positive value. As shown in FIG. 4D, the feeding speed Fs becomes the first forward feeding speed Ffs1. As shown in FIG. 3A, the welding voltage Vw has an arc voltage value of several tens of volts. As shown in FIG. 5B, the welding current Iw is a current value determined by the first forward feed speed Ffs1 and the arc load because the welding power source is controlled at a constant voltage. Therefore, the welding current Iw has a waveform that varies with the variation of the arc load. During this arc period Ta (n-1), the tip of the welding wire melts to form droplets.

  When the droplet formed at the tip of the welding wire comes into contact with the molten pool at time t2, a short-circuit state occurs. In the short circuit state, the welding voltage Vw decreases to a short circuit voltage value of several volts as shown in FIG. It is determined that the welding voltage Vw is less than the threshold value, and occurrence of a short circuit is determined. This threshold is set to about 10-15V. When the occurrence of a short circuit is determined, the welding power source is switched to constant current control. As shown in FIG. 5B, the short circuit current Is is a predetermined small value during a predetermined short circuit initial period Tsi from time t2 to t21. The current value is maintained, increases during a predetermined short-circuit current increase period Tsu from time t21 to t23, and has a slope during the short-circuit current decrease period Tsd from time t23 to time t3 when the arc is generated. Decrease. At the same time t2, as shown in FIG. 5C, the feed speed setting signal Fr is switched to a reverse feed speed setting value Frr having a predetermined negative value. In response to this, as shown in FIG. 4D, the feed speed Fs is a negative value passing through 0 from the first forward feed speed Ffs1 having a positive value during the period of time t2 to t22. The reverse feed speed Frs changes. That is, when the short-circuit occurs at time t2, the feeding speed Fs at the tip of the welding wire decelerates from the first forward feeding speed Ffs1 to 0, accelerates by reversing the feeding direction, and reverses feeding speed Frs at time t22. To reach. Therefore, the period from time t2 to t22 is referred to as a feeding reversal period. This feed reversal period is about 2 ms when a servo motor having good responsiveness is used as the feed motor, the length of the welding torch is shortened to several tens of centimeters, and the friction of the feed path is reduced. In the figure, the time t22 at which the feed speed Fs becomes the reverse feed speed Frs is in the above-described short-circuit current increasing period Tsu. After time t22, the backward feeding at the backward feeding speed Frs is continued. As a result, the tip of the welding wire gradually moves away from the molten pool. When the contact state with the molten pool is eliminated at time t3, the arc is regenerated. The initial short-circuit period Tsi is set to about 0.5 to 2 ms by experiment according to welding conditions. Said short circuit current increase period Tsu is set to about 2-6 ms by experiment according to welding conditions. The short circuit current value Is during the short circuit initial period Tsi is set to about several tens of A. The maximum value of the short circuit current Is during the short circuit current increase period Tsu is set to a value close to the welding current average value. The short-circuit initial period Tsi is provided in order to lead the contact between the droplet and the molten pool to a stable short-circuit state. The reason why the short-circuit current Is is increased is not to promote detachment by forming a constriction by applying an electromagnetic pinch force to the droplet as in general consumable electrode arc welding, but during the short-circuit period Ts. This is also to ensure heating by Joule heat. Therefore, the maximum value of the short-circuit current Is is about 400 to 500 A in general consumable electrode arc welding, but is about 150 to 250 A in the figure. Since the arc is regenerated by the backward feeding, each short-circuit period becomes a substantially constant value. Therefore, both values are set so that the addition point of Tsi + Tsu is shorter by about 1 ms than the time length of the short-circuit period. This is because the short-circuit current reduction period Tsd is secured for about 1 ms so that the short-circuit current Is can be reduced to a small value by the time of arc re-occurrence at time t3. The decrease rate of the short circuit current Is during the short circuit current decrease period Tsd is determined by the resistance value of the short circuit load, the inductance value of the current path from the welding power source, and the resistance value. This decrease rate is about 150 A / ms. Therefore, if the maximum value of the short-circuit current Is at time t23 is 200 A and the short-circuit current reduction period Tsd is 1 ms as described above, the current value at time t3 is as small as 50 A. When the current value at the time of arc re-generation becomes a small value, the occurrence of spatter is reduced. For example, to give numerical examples, Tsi = 1 ms, Tsu = 3 ms, and Tsd = 1 ms. In this case, the short-circuit period Ts = 5 ms.

  When the arc is regenerated at time t3, the welding voltage Vw increases to an arc voltage value of about several tens of volts as shown in FIG. When it is determined that the welding voltage Vw is equal to or higher than the threshold value and the reoccurrence of the arc is determined, the feed speed setting signal Fr is the first forward feed speed setting as shown in FIG. The value is switched to Ffr1. In response to this, as shown in FIG. 4D, the feed speed Fs is changed from the reverse feed speed Frs to the first forward feed speed Ffs1 during the feed reversal period from time t3 to time t31. To change. At time t3, since the welding power source is switched to constant voltage control, the welding current Iw increases to a current value determined by the first forward feed speed Ffs1 and the arc load, as shown in FIG. . At time t32, when the arc period reaches the reference period Tt, the welding power source is switched to constant current control, and the welding current Iw is a low arc with a predetermined small current value as shown in FIG. It decreases to the current value Ia. Thereafter, after the second arc period Ta2 continues for a while, a short circuit occurs at time t4. The reference period Tt is set in a range of about 10 to 30 ms. The low arc current value Ia is set to about several tens of A.

The same applies to the n-th short-circuit period Ts (n). In the feed control method shown here, since the current value when the arc is regenerated at time t3 is a small value, the amount of spatter generation is reduced. Moreover, since the arc can be reliably regenerated by performing the backward feeding during the short circuit period, the stability of the welding state is improved. When the arc period reaches the reference period Tt, the reason why the welding current Iw is decreased and maintained at a small current value is as follows. That is, the distribution of the arc period is concentrated in a certain range. However, sometimes the arc period becomes longer due to disturbances such as irregular movement of the molten pool and fluctuation of the arc length accompanying movement of the cathode spot forming position. When the arc period becomes longer than usual, the size of the droplet increases and the droplet is overheated. As a result, a phenomenon occurs in which the gas inside the droplet expands due to overheating and the droplet bursts, and many spatters are scattered along with the burst. Furthermore, when a large droplet is short-circuited, many spatters are scattered from the molten pool at that moment. In order to prevent these, when the arc period becomes equal to or longer than the reference period Tt, the arc current is weakened by setting the welding current Iw to a small current value so that a short circuit occurs early.

JP 2007-216268 A

  As described above, in the prior art, when the arc period becomes longer than the reference period due to disturbance, the welding current value is decreased and maintained at a small current value. When the welding current becomes a small current value, since the arc force becomes weak, the depression of the molten pool becomes small, the force that lifts the droplets upward becomes weak, and a short circuit occurs early. As a result, overheating and enlarging of the droplets can be prevented and occurrence of spatter can be suppressed.

  However, even if the welding current is reduced, a short circuit rarely occurs in about 5 ms or less. Depending on the welding current value, it takes 7-10 ms or more to reduce the molten pool dent and droplet rise, so a short circuit will not occur until more time has passed. There are many cases. Of course, when the welding current is reduced, the short circuit occurs earlier, but the effect is limited. In order to prevent the droplets from overheating and enlarging more reliably, it is desirable that a short circuit occurs as soon as possible after the reference period. Furthermore, if the period during which the welding current is maintained at a low current value continues for a long time, a problem that the bead appearance is deteriorated newly arises.

  Therefore, an object of the present invention is to provide an arc welding control method capable of quickly generating a short circuit when the arc period becomes equal to or longer than a reference period.

In order to solve the above-described problem, the invention of claim 1 is directed to an arc welding control method for feeding a welding wire and repeatedly welding an arc period and a short-circuit period.
During the first arc period in which the arc period is less than a predetermined reference period, the welding wire is fed forward at a predetermined first forward feed speed;
During the second arc period in which the arc period is equal to or greater than the reference period, the welding wire is fed forward at a predetermined second forward feed speed,
Setting the second forward feed speed to a value greater than the first forward feed speed;
An arc welding control method characterized by the above.

In the invention of claim 2, the second forward feed speed changes so as to increase with time.
The arc welding control method according to claim 1, wherein:

The invention of claim 3 reduces the welding current value during the second arc period to a value smaller than the welding current value during the first arc period.
The arc welding control method according to claim 1, wherein the arc welding control method is provided.

According to a fourth aspect of the present invention, during the short circuit period, the welding wire is fed backward.
It is an arc welding control method given in any 1 paragraph of Claims 1-3 characterized by things.

  According to the present invention, during the first arc period in which the arc period is less than a predetermined reference period, the welding wire is fed forward at a predetermined first forward feed speed, and the arc period is equal to or greater than the reference period. During the second arc period, the welding wire is fed forward at a predetermined second forward feed speed, and the second forward feed speed is set to a value larger than the first forward feed speed. As a result, when the arc period becomes longer than the reference period, the forward feed speed is accelerated, and it is possible to lead to a short circuit state at an early stage. As a result, since overheating and enlarging of the droplets can be prevented more reliably than in the prior art, the welding quality is further improved.

It is an output waveform diagram which shows the arc welding control method which concerns on Embodiment 1 of this invention. It is a figure which shows the change pattern with time progress of 2nd forward feeding speed Ffs2. It is a block diagram of the welding power supply for implementing the arc welding control method which concerns on Embodiment 1 of this invention. It is an output waveform diagram which shows the arc welding control method of a prior art.

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

[Embodiment 1]
In the invention according to the first embodiment, during the first arc period Ta1 in which the arc period Ta is less than a predetermined reference period Tt, the welding wire is forwardly fed at a predetermined first forward feed speed Ffs1, and the reference period is reached. During the second arc period Ta2, which is equal to or greater than Tt, the welding wire is fed forward at a predetermined second forward feed speed Ffs2, and the second forward feed speed Ffs2 is set to a value larger than the first forward feed speed Ffs1. It is to set. That is, when the arc period Ta becomes equal to or longer than the reference period Tt, the forward feed speed of the welding wire is increased, and the short-circuit is quickly led. Hereinafter, this embodiment will be described.

  FIG. 1 is an output waveform diagram showing an arc welding control method according to Embodiment 1 of the present invention. (A) shows the welding voltage Vw, (B) shows the welding current Iw, (C) shows the feed speed setting signal Fr, and (D) shows the actual welding wire tip. The feeding speed Fs is shown. In the figure, description of the same operation period (time period from time t1 to t32 and time period from t4 to t5) as in FIG. 4 is omitted. In the figure, the operation in the period from time t32 to t4 is different from that in FIG. Hereinafter, this period will be described with reference to FIG.

  In the figure, the period from time t1 to t2 is the (n-1) th arc period Ta (n-1), and the period from time t2 to t3 is the n-1th short-circuit period Ts (n-1). Yes, the period from time t3 to t4 is the nth arc period Ta (n), and the period from time t4 to t5 is the nth short circuit period Ts (n). This is the case when Ta (n-1) <Tt, and when Ta (n)> Tt. In the (n-1) th arc period Ta (n-1) from time t1 to t2, a short circuit occurred during the first arc period Ta1. The n-th arc period Ta (n) from time t3 to t4 is formed by a first arc period Ta1 from time t3 to t32 and a second arc period Ta2 from time t32 to t4. However, the time length of the second arc period Ta2 from time t32 to t4 is a short period of half or less compared to the case of FIG. The reason for this will be described later.

  When the arc is regenerated at time t3, the welding voltage Vw increases to an arc voltage value of about several tens of volts as shown in FIG. When it is determined that the welding voltage Vw has become equal to or greater than the threshold value and the reoccurrence of the arc is determined, the feed speed setting signal Fr is a predetermined first forward feed speed as shown in FIG. The setting value is switched to Ffr1. In response to this, as shown in FIG. 4D, the feed speed Fs is changed from the reverse feed speed Frs to the first forward feed speed Ffs1 during the feed reversal period from time t3 to time t31. To change. At time t3, since the welding power source is switched to constant voltage control, the welding current Iw increases to a current value determined by the first forward feed speed Ffs1 and the arc load, as shown in FIG. .

  At time t32, when the arc period reaches a predetermined reference period Tt, the welding power source is switched to constant current control, and the welding current Iw has a predetermined small current value as shown in FIG. To a low arc current value Ia. At the same time, at time t32, the feed speed setting signal Fr is switched to the predetermined second forward feed speed setting value Ffr2 as shown in FIG. 10C, and as shown in FIG. The feed speed Fs is accelerated to the second forward feed speed Ffs2. Here, since Ffr2> Ffr1, Ffs2> Ffs1. That is, the forward feed speed is controlled to be accelerated and accelerated at time t32. Due to the acceleration of the forward feeding speed, the droplets are quickly short-circuited with the molten pool. As a result, a short circuit occurs at time t4, a short time after time t32. The time from the start of acceleration of the forward feed speed to the occurrence of a short circuit is less than about 2 to 5 ms. The low arc current value Ia is set to about 30 to 100A. This low arc current value Ia is set to be an appropriate value according to welding conditions (welding method, welding current average value, material of welding wire, diameter, etc.) through experiments.

  In the forward feed speed acceleration control, how to set the reference period Tt and the second forward feed speed Ffs2 is important. Hereinafter, a method for setting these parameters will be described.

(1) Setting method of reference period Tt The distribution of the arc period is measured by experiment, and the reference period Tt is set so that the ratio of the arc period that is equal to or greater than the reference period Tt is 5 to 10%. That is, most arc periods are less than the reference period Tt. This is because the arc period sometimes becomes longer due to the disturbance, and this longer arc period is determined by the reference period Tt. The reference period Tt is set to an appropriate value according to welding conditions such as a welding method, a welding current average value, a welding wire material, and a diameter. Examples of the welding method include a carbon dioxide arc welding method, a mag welding method, and a MIG welding method. The average value of the welding current is substantially determined by the first forward feed speed Ffs1. As another method for setting the reference period Tt, welding is performed without setting the reference period Tt so as not to decrease the current and accelerate the feeding speed, and the average value of the arc period at that time is determined. calculate. Then, the reference period Tt may be set to 1.5 to 2.0 times the average value.

(2) Method of setting the second forward feed speed Ffs2 In general arc welding in which welding is performed by feeding a welding wire at a constant forward feed speed, the base metal plate thickness, joint shape, welding speed, etc. The feeding speed is determined according to the above. The average value of the welding current is determined by the feeding speed. Also in the present embodiment, as in the case of the general welding described above, an appropriate bead is formed according to the thickness of the base material, the joint shape, the welding speed, etc., in the first forward feed speed Ffs1. Is set as follows. The average value of the welding current is substantially determined by the first forward feed speed Ffs1. In the present embodiment, the welding wire is retracted during the short-circuit period, so that the average value of the welding current changes under the influence of the number of short-circuits. However, in a stable welding state, the number of short circuits per unit time can be regarded as a substantially constant value. In this case, the average value of the welding current is determined by the first forward feed speed Ffs1. The second forward feed speed Ffs2 is set to 1.5 to 2.0 times the first forward feed speed Ffs1. When the first forward feed speed Ffs1 changes according to the welding conditions, the second forward feed speed Ffs2 may be changed accordingly. In the figure, the second forward feed speed Ffs2 changes stepwise from the first forward feed speed Ffs1 in the reference period Tt, and is a constant value after the reference period Tt has elapsed. The second forward feed speed Ffs2 may be increased in a stepped shape, a straight shape, a curved shape, etc. with the passage of time after the elapse of the reference period Tt. FIG. 2 is a diagram showing a change pattern of the second forward feed speed Ffs2 with time. In the figure, the horizontal axis indicates the elapsed time t (ms) after the lapse of the reference period Tt, and the vertical axis indicates the second forward feed speed Ffs2 (m / min). Therefore, in the same figure, when t = 0 is the time when the arc period reaches the reference period Tt. In the figure, a pattern P1 shown in practice is a case where the second forward feed speed Ffs2 is a constant value regardless of the passage of time. That is, the pattern P1 is the case of FIG. Next, a pattern P2 indicated by a broken line is a case where the second forward feed speed Ffs2 increases to a predetermined peak value in a straight line rising upward with time. Further, the pattern P3 indicated by the alternate long and short dash line is a case where the second forward feed speed Ffs2 increases stepwise. In this case, when the arc period becomes the reference period Tt, the feeding speed is accelerated to the second forward feeding speed Ffs2, and when a predetermined period elapses thereafter, the feeding speed is further accelerated by a predetermined speed. The reason why the second forward feed speed Ffs2 is increased with time as in the patterns P2 and P3 is that it is not desired to increase the forward feed speed when a short circuit occurs. That is, if the forward feed speed when a short circuit occurs is high, the tip of the welding wire is pushed too much into the molten pool, and the short circuit state may become unstable. However, when the time from the acceleration of the forward feed speed to the occurrence of the short circuit is long in the reference period Tt, it is more important to further accelerate and generate the short circuit early.

  FIG. 3 is a block diagram of a welding power source for carrying out the arc welding control method according to the first embodiment of the present invention described above. Hereinafter, each circuit will be described with reference to FIG.

  The power supply main circuit PM receives a commercial AC power supply (not shown) such as a three-phase 200V as input, performs output control by inverter control according to a drive signal Dv described later, and outputs a welding voltage Vw and welding current Iw suitable for welding To do. Although not shown, this power main circuit PM has a primary rectifier circuit that rectifies commercial AC power, a capacitor that smoothes the rectified direct current, and an inverter that converts the smoothed direct current into high frequency alternating current according to the drive signal Dv. The circuit includes a high-frequency transformer that steps down the high-frequency alternating current to a voltage value suitable for arc welding, a secondary rectifier circuit that rectifies the stepped-down high-frequency alternating current, and a reactor that smoothes the rectified direct current. The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 directly connected to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2.

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The short circuit determination circuit SD receives the voltage detection signal Vd as an input, determines a short circuit period and an arc period based on the value, and outputs a short circuit determination signal Sd which is at a high level during the short circuit period and is at a low level during the arc period. To do. The second arc period discriminating circuit AD receives this short circuit discrimination signal Sd and becomes High level when a predetermined reference period Tt elapses from when the short circuit discrimination signal Sd changes to Low level (arc period). A second arc period signal Ad that becomes Low level when the short circuit determination signal Sd changes to High level (short circuit period) is output. That is, the second arc period signal Ad is a signal that becomes High level during the second arc period.

  The first forward feed speed setting circuit FFR1 outputs a predetermined first forward feed speed setting signal Ffr1. The second forward feed speed setting circuit FFR2 receives the second arc period signal Ad as described above, and measures the elapsed time from the time when the second arc period signal Ad becomes High level, as illustrated in FIG. The second forward feed speed setting signal Ffr2 corresponding to the elapsed time is output from a predetermined change pattern. The reverse feed speed setting circuit FRR outputs a predetermined reverse feed speed setting signal Frr. The forward feed speed switching circuit SFF receives the second arc period signal Ad, the first forward feed speed setting signal Ffr1, and the second forward feed speed setting signal Ffr2 as inputs. When Ad is Low level, it switches to the b side and outputs the first forward feed speed setting signal Ffr1 as the forward feed speed setting signal Ffr, and when it is High level, it switches to the a side and sets the second forward feed speed setting signal Ffr1. The signal Ffr2 is output as the forward feed speed setting signal Ffr. The feed speed setting switching circuit SF receives the short circuit determination signal Sd, the forward feed speed setting signal Ffr, and the reverse feed speed setting signal Frr as inputs, and the short circuit determination signal Sd is at a low level (arc period). When it is, it switches to b side and forward feed speed setting signal Ffr is output as feed speed setting signal Fr. When it is High level (short circuit period), it switches to a side and feeds backward feed speed setting signal Frr. Output as a speed setting signal Fr. The feed control circuit FC outputs a feed control signal Fc for feeding the welding wire to the feed motor WM in accordance with the feed speed setting signal Fr. Therefore, as shown in FIG. 1 described above, during the first arc period from time t3 to t32, the value of the feed speed setting signal Fr becomes the value of the first forward feed speed setting signal Ffr1, and the feed speed Fs is The first forward feed speed Ffs1 is obtained. During the second arc period from time t32 to t4, the value of the feed speed setting signal Fr becomes the value of the second forward feed speed setting signal Ffr2, and the feed speed Fs becomes the second forward feed speed Ffs2. During the short-circuit period from time t4 to t5, the value of the feeding speed setting signal Fr becomes the value of the backward feeding speed setting signal Frr, and the feeding speed Fs becomes the backward feeding speed Frs.

  The short-circuit current setting circuit ISR takes the short-circuit determination signal Sd as an input and becomes a small current value during a predetermined short-circuit initial period Tsi from the time when the short-circuit determination signal Sd becomes High level (short-circuit period), and continues to be determined in advance The short-circuit current setting signal Isr is output in a curved line during the short-circuit current increase period Tsu and decreases after the short-circuit current increase period Tsu has elapsed. The low arc current setting circuit IAR outputs a predetermined low arc current setting signal Iar. The arc voltage setting circuit VAR outputs a predetermined arc voltage setting signal Var for setting the arc voltage during the arc period. The current setting switching circuit SI receives the short-circuit determination signal Sd as described above, and switches to the b side when the short-circuit determination signal Sd is at the low level (arc period), and outputs the low arc current setting signal Iar as the current setting signal Ir. When in the High level (short circuit period), the switch is made to the a side and the short circuit current setting signal Isr is output as the current setting signal Ir. The current error amplification circuit EI amplifies an error between the current setting signal Ir and the current detection signal Id, and outputs a current error amplification signal Ei. The voltage error amplification circuit EV amplifies an error between the arc voltage setting signal Var and the voltage detection signal Vd, and outputs a voltage error amplification signal Ev. The OR circuit OR performs an OR operation on the short circuit determination signal Sd and the second arc period signal Ad, and outputs a OR signal Or. The OR signal Or is a signal that is at a high level during the short circuit period and the second arc period, and is at a low level during the first arc period. The external characteristic switching circuit SP receives the logical sum signal Or, the current error amplification signal Ei, and the voltage error amplification signal Ev. When the logical sum signal Or is at the low level (first arc period), the b side The voltage error amplified signal Ev is output as the error amplified signal Ea, and when it is at the High level (short circuit period and second arc period), the voltage error amplified signal Ev is switched to the a side, and the current error amplified signal Ei is used as the error amplified signal Ea Output. Therefore, constant voltage control is performed during the first arc period, and constant current control is performed during the short circuit period and the second arc period. The drive circuit DV performs pulse width modulation control according to the error amplification signal Ea, and outputs a drive signal Dv for driving the inverter circuit.

  In the present embodiment, the case where the welding current is reduced to a small current value during the second arc period has been described. However, the current may not be reduced. This is because, when the second arc period is entered, a short circuit can be quickly led by the control for accelerating the forward feed speed, so there is no need to reduce the current when the welding current average value is about 200 A or less. It is. In the present embodiment, the case where the welding wire is fed backward during the short-circuit period has been described. However, as in general arc welding, the forward feed is performed at the first forward feed speed even during the short-circuit period. May be. In this case, the short-circuit current Is is maintained by decreasing to a predetermined small current value during the predetermined initial short-circuit period Tsi, and thereafter increasing in a curved line to restore the arc to a predetermined peak value. Maintain until it occurs. That is, the short-circuit current reduction period Tsd is not provided. In the present embodiment, the case where the low arc current value during the second arc period is energized by the constant current control has been described. However, the arc voltage set value Var is decreased so as to decrease during the second arc period. You may make it energize by voltage control. In this case, constant voltage control is performed during the entire arc period. The present invention can be applied to short circuit transfer welding, globule transfer welding with short circuit, spray transfer welding with short circuit, and the like. The present invention can also be applied to carbon dioxide arc welding, mag welding, MIG welding, pulse arc welding, AC pulse arc welding, and the like.

  According to the first embodiment described above, during the first arc period in which the arc period is less than the predetermined reference period, the welding wire is fed forward at a predetermined first forward feed speed, and the arc period is the reference period. During the second arc period which is equal to or longer than the period, the welding wire is fed forward at a predetermined second forward feed speed, and the second forward feed speed is set to a value larger than the first forward feed speed. As a result, when the arc period becomes longer than the reference period, the forward feed speed is accelerated, and it is possible to lead to a short circuit state at an early stage. As a result, since overheating and enlarging of the droplets can be prevented more reliably than in the prior art, the welding quality is further improved.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll AD 2nd arc period discrimination circuit Ad 2nd arc period signal DV Drive circuit Dv Drive signal Ea Error amplification signal EI Current error amplification circuit Ei Current error amplification signal EV Voltage Error amplification circuit Ev Voltage error amplification signal FC Feed control circuit Fc Feed control signal Ffr Forward feed speed setting signal FFR1 First forward feed speed setting circuit Ffr1 First forward feed speed setting (value / signal)
FFR2 Second forward feed speed setting circuit Ffr2 Second forward feed speed setting (value / signal)
Ffs1 First forward feed speed Ffs2 Second forward feed speed Fr Feed speed setting signal FRR Reverse feed speed setting circuit Frr Reverse feed speed setting (value / signal)
Frs Reverse feed speed Fs Feed speed Ia Low arc current value IAR Low arc current setting circuit Iar Low arc current setting signal ID Current detection circuit Id Current detection signal Ir Current setting signal Is Short circuit current ISR Short circuit current setting circuit Isr Short circuit current setting Signal Iw Welding current OR OR circuit OR OR signal PM Power supply main circuit SD Short circuit determination circuit Sd Short circuit determination signal SF Feeding speed setting switching circuit SFF Forward feeding speed switching circuit SI Current setting switching circuit SP External characteristic switching circuit Ta Arc Period Ta1 First arc period Ta2 Second arc period Ts Short circuit period Tsd Short circuit current decrease period Tsi Short circuit initial period Tsu Short circuit current increase period Tt Reference period VAR Arc voltage setting circuit Var Arc voltage setting (value / signal)
VD Voltage detection circuit Vd Voltage detection signal Vw Welding voltage WM Feeding motor

Claims (4)

In the arc welding control method of feeding a welding wire and repeatedly welding an arc period and a short-circuit period,
During the first arc period in which the arc period is less than a predetermined reference period, the welding wire is fed forward at a predetermined first forward feed speed;
During the second arc period in which the arc period is equal to or greater than the reference period, the welding wire is fed forward at a predetermined second forward feed speed,
Setting the second forward feed speed to a value greater than the first forward feed speed;
An arc welding control method characterized by the above. The second forward feed speed changes so as to increase with time.
The arc welding control method according to claim 1. Reducing the welding current value during the second arc period to a value smaller than the welding current value during the first arc period;
The arc welding control method according to any one of claims 1 to 2, wherein the arc welding control method is performed. During the short circuit period, the welding wire is fed backward.
The arc welding control method according to any one of claims 1 to 3, wherein:

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