JP2016002564A - Pulse arc welding control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the deterioration in a bead appearance by magnetic blowing in pulse arc welding.SOLUTION: A rise transition current is conducted in a rise-up period, and a peak current is conducted in a peak period, and a drop transition current is conducted in a fall period, and a base current is conducted in a base period. Test welding, in which a magnetic blowing generation section on a welding line is discriminated by a rise in welding voltage in the base period and stored, is executed, and when welding the stored magnetic blowing generation section on the welding line in actual execution, the fall period Tks is lengthened by delaying a drop speed of the drop transition current Iks. Thus, since the arc length can be put in a short state when entering the base period Tb where rigidity of an arc weakened, even if magnetic blowing is generated, large deflection of the arc can be restrained, and the occurrence of an arc cut can be prevented.

Description

  The present invention relates to a pulse arc welding control method that can suppress instability of a welding state due to magnetic blowing.

  Consumable electrode type pulse arc welding is widely used for welding steel and the like. In this pulse arc welding, a rising transition current that rises from the base current to the peak current is applied during the rising period, the peak current is supplied during the peak period, and the peak current decreases to the base current during the falling period. A downward transition current is applied, a base current is applied during the base period, and welding is performed by repeating the application of these welding currents in one pulse cycle. In pulse arc welding, since one droplet period is one droplet transfer state, the droplet transfer state is stable, so that the occurrence of spatter is small and a beautiful bead appearance can be obtained. Hereinafter, this pulse arc welding will be described with reference to the drawings.

  FIG. 7 is a general current / voltage waveform diagram in pulse arc welding. FIG. 4A shows the time change of the welding current Iw, and FIG. 4B shows the time change of the welding voltage Vw. Hereinafter, a description will be given with reference to FIG.

  During the rising period Tu from time t1 to t2, the rising transition current Iu rising from the base current Ib to the peak current Ip is energized as shown in FIG. A rising transition voltage rising from the base voltage Vb to the peak voltage Vp is applied between the welding wire and the base material. During the peak period Tp from time t2 to t3, as shown in FIG. 6A, a peak current Ip having a large current value greater than the critical value is applied to transfer the droplets from the welding wire, and FIG. ), A peak voltage Vp proportional to the arc length is applied. The critical value of a steel wire having a diameter of 1.2 mm is about 280A.

  During the falling period Tk from time t3 to t4, as shown in FIG. 6A, the falling transition current Ik that decreases from the peak current Ip to the base current Ib is energized, and as shown in FIG. A falling transition voltage falling from the peak voltage Vp to the base voltage Vb is applied. During the base period Tb from time t4 to t5, as shown in FIG. 5A, the base current Ib having a small current value less than the critical value is energized to prevent the formation of droplets, and FIG. ), A base voltage Vb proportional to the arc length is applied. Welding is performed by repeating the period from time t1 to t5 as one pulse period Tf. The arc length is longer during the peak period Tp and shorter during the base period Tb.

  By the way, in order to perform good pulse arc welding, it is important to maintain the average arc length at an appropriate value. In order to maintain the average arc length at an appropriate value, the following arc length control (output control of the welding power source) is performed. The average arc length is substantially proportional to the welding voltage average value Vav indicated by a broken line in FIG. For this purpose, the welding voltage average value Vav is detected, and the welding current average value Iav indicated by the broken line in FIG. 4A is changed so that the detected value becomes equal to the welding voltage setting value corresponding to the appropriate average arc length. Perform output control. When the welding voltage average value Vav is larger than the welding voltage set value, the average arc length is longer than the appropriate value. Therefore, the welding current average value Iav is decreased to decrease the wire melting rate and the average arc length is shortened. Like that. On the other hand, when the welding voltage average value Vav is smaller than the welding voltage set value, the average arc length is shorter than the appropriate value. Therefore, the welding current average value Iav is increased to increase the wire melting rate and the average arc length is increased. Try to be long. As the welding voltage average value Vav, a value (average value, smooth value) obtained by passing the welding voltage Vw through a low-pass filter is generally used. Further, frequency modulation control for changing the pulse period Tf is performed as means for changing the welding current average value Iav. In the frequency modulation control, the pulse period Tf is feedback controlled (arc length control) so that the welding voltage average value Vav becomes equal to the welding voltage set value. At this time, the rising period Tu, the peak period Tp, the falling period Tk, the peak current Ip, and the base current Ib are set to predetermined values, and the pulse period Tf is varied by feedback control of the base period Tb. The combination of the peak period Tp and the peak current Ip is called a unit pulse condition, and is set so that one droplet period is in a droplet transfer state.

  Another arc length control method is pulse width modulation control. In the pulse width modulation control, the peak period (pulse width) Tp is feedback controlled. At this time, the rising period Tu, the falling period Tk, the pulse period Tf, the peak current Ip, and the base current Ib are set to predetermined values, and the peak period Tp is varied.

  In consumable electrode type arc welding including pulse arc welding, a magnetic field is formed around the arc by a welding current passing through the arc and the base material, and the arc may be deflected by receiving a force from the magnetic field. Such a state is generally called magnetic blow or arc blow. Whether magnetic blowing occurs depends on the form of the magnetic field formed by the welding current passed through the base material. When the welded part is away from the end of the base metal, the magnetic field is often formed in a symmetrical shape, so that the arc does not receive a biased force from the magnetic field, so magnetic blowing occurs. Hateful. On the other hand, when the welded part is close to the end of the base material, the magnetic field is formed in an asymmetric shape, so that the arc receives a force deviated from the magnetic field, and magnetic blown easily occurs. Therefore, magnetic blowing is likely to occur at the welding start portion and the welding end portion that are often near the end of the base material. Among consumable electrode arcs, magnetic blow is less likely to occur in short circuit transfer welding, and more likely to occur in pulse arc welding. This is because, in short-circuit transfer welding, the arc length is shorter than in pulse arc welding, and is therefore less susceptible to the influence of a magnetic field. On the other hand, in pulse arc welding, a strong magnetic field is formed when the peak current Ip having a large current value is energized, and a weak magnetic field is formed when the base current Ib having a small current value is energized. In pulse arc welding, magnetic field blow tends to occur due to the fact that the change in strength of the magnetic field is large and the base current Ib is small, so that the arc is deflected as soon as it receives a force biased from the magnetic field. . Therefore, in pulse arc welding, arc deflection due to magnetic blowing is likely to occur during the base period Tb.

  FIG. 8 is a diagram showing an arc state when magnetic blowing occurs. As shown in FIG. 2A, a normal arc 3 is generated between the welding wire 1 and the base material 2. When magnetic blowing occurs in this state, as shown in FIG. 5B, the arc 3 is largely deflected by the force from the magnetic field, and the arc length becomes long. If the deflection is further increased, the arc cannot be maintained and an arc break occurs as shown in FIG. In pulse arc welding, since a large current is applied during the peak period, the arc is highly rigid and the arc hardly deflects even when a force from a magnetic field is applied. On the other hand, since a small current is applied during the base period, the arc rigidity is weak, and it is largely deflected by the force from the magnetic field. Therefore, it is almost during the base period that the magnetic blow occurs and the arc break occurs. When a magnetic blow that does not cause arc breakage rarely occurs, there is almost no effect on the welding state. However, when a magnetic blow accompanied by an arc break occurs many times, the arc generation state becomes unstable, and a large amount of spatter is generated, and a bead failure occurs. Therefore, in pulse arc welding, it is important to suppress arc breaks due to magnetic blowing in order to obtain good welding quality.

  FIG. 9 is a current / voltage waveform diagram when magnetic blowing occurs in pulse arc welding. FIG. 4A shows the time change of the welding current Iw, and FIG. 4B shows the time change of the welding voltage Vw. Hereinafter, a description will be given with reference to FIG.

  When a magnetic blow occurs and the arc is deflected at time t1 in the base period Tb, as shown in FIG. 5B, the arc length is increased with the deflection of the arc, and the base voltage Vb is gradually increased. growing. On the other hand, the base current Ib remains constant as shown in FIG. At time t2, when the deflection of the arc due to magnetic blowing is further increased, the arc length becomes so long that the arc cannot be maintained, and an arc break occurs. When the arc break occurs, the welding current Iw stops flowing as shown in FIG. 5A, and the welding voltage Vw becomes a no-load voltage that is the maximum output voltage as shown in FIG.

  FIG. 10 is a current / voltage waveform diagram showing magnetic blow countermeasure control for preventing arc break due to magnetic blow disclosed in Patent Document 1. FIG. 4A shows the time change of the welding current Iw, and FIG. 4B shows the time change of the welding voltage Vw. In the figure, a stable welding state in which magnetic blowing is not generated is shown during the pulse period from time t1 to t2, and a welding state in which magnetic blowing is generated during the subsequent pulse period from time t2 to t3. Show.

  At time t21 in the base period Tb, the arc length is increased because the magnetic blow is generated and the arc is deflected, and the base voltage Vb increases from the normal value and increases as shown in FIG. At time t22, the value of the base voltage Vb becomes equal to or higher than a predetermined reference voltage value Vt indicated by a broken line. When it is determined that the base voltage value Vb is equal to or higher than the reference voltage value Vt, the base current Ib is increased from the normal value to 200 A or higher as shown in FIG. During the period from time t22 to t23, the base voltage value Vb is equal to or higher than the reference voltage value Vt. During this period, the base current increased to 200 A or more is applied as shown in FIG.

  During the period from time t22 to t23, since the value of the base current Ib increases to 200 A or more, since the rigidity that is a property that the arc is generated in the wire feeding direction becomes strong, the deflection of the arc is in a normal state. Will be returned. For this reason, as shown in FIG. 5B, at time t23, the base voltage value Vb becomes less than the reference voltage value Vt, and then rapidly decreases and returns to the normal value. Therefore, the magnetic blow occurs at time t21 and is canceled immediately after time t23. At time t23, the value of the base current Ib returns to the normal value as shown in FIG. During the remaining base period Tb from time t23 to t3, the value of the base current Ib remains the normal value as shown in FIG. 5A, and the base value of the normal value is maintained as shown in FIG. A voltage value Vb is applied. The arc during this period is in a stable state because no magnetic blow has occurred.

  In the above, the reference voltage value Vt is set to an appropriate value according to the welding conditions in consideration of the fluctuation of the base voltage value Vb in a state where no magnetic blow is generated. For example, since the fluctuation of the base voltage Vb does not reach the peak voltage value Vp, the reference voltage value Vt is set to a value close to the peak voltage value Vp. In addition, hysteresis may be provided in comparison between the base voltage Vb and the reference voltage value Vt. That is, the reference value when the base voltage Vb increases from the normal value is the first reference voltage value Vt1, and the reference value when the base voltage Vb once exceeds Vt1 and then decreases is the second reference voltage value Vt2. It is what. At this time, Vt1> Vt2. Further, the occurrence of magnetic blow is determined when the increase rate of the base voltage Vb (differential value = dVw / dt) reaches the reference value, and then the magnetic blow rate is determined when the decrease rate of the base voltage Vb reaches the reference value. You may make it discriminate | determine cancellation | release. Various conventional methods for determining the occurrence of magnetic blow by increasing the base voltage Vb can be used. The increased base current value is experimentally set to a value that can correct the arc deflection in the range of about 200 to 500 A.

  By performing such magnetic blow countermeasure control, it is possible to prevent arc breakage due to magnetic blow.

JP 2004-268081 A

  In the above-described prior art, arc breakage can be prevented from occurring by discriminating arc deflection caused by magnetic blowing and increasing the base current to 200 A or more. However, in such a method, since the melting of the welding wire is promoted when the base current is increased, the 1-pulse cycle 1 droplet transfer state is broken. As a result, the bead failure is not reached, but there is a problem that the bead appearance is deteriorated.

  Therefore, an object of the present invention is to provide a pulse arc welding control method capable of preventing occurrence of arc breakage due to magnetic blowing and suppressing deterioration of the bead appearance.

In order to solve the above-described problems, the invention of claim 1
In addition to feeding the welding wire, a rising transition current rising from the base current to the peak current is supplied during the rising period, the peak current is supplied during the peak period, and the peak current is supplied from the peak current during the falling period. In a pulse arc welding control method of energizing a falling transition current that decreases to a current, energizing the base current during a base period, and repeatedly energizing these welding currents as one pulse period,
With the increase of the welding voltage during the base period, test welding is performed to determine and store the magnetic blowing occurrence section on the weld line,
At the time of execution, when welding the memorized magnetic blow occurrence section on the weld line, the falling period is lengthened,
It is the pulse arc welding control method characterized by this.

The invention of claim 2 makes the falling period longer by slowing down the descending speed of the descending transition current.
The pulse arc welding control method according to claim 1, wherein:

According to a third aspect of the present invention, when the falling transition current reaches a predetermined reference current value, the value is maintained for a predetermined period, so that the falling period is lengthened, and the reference current value is set to the peak current. Set to a value smaller than the value and larger than the value of the base current,
The pulse arc welding control method according to claim 1, wherein:

  According to the present invention, it is possible to make the arc length short when entering the base period in which the arc rigidity becomes weak. For this reason, even if magnetic blowing occurs, it is possible to prevent the arc from being greatly deflected, and arc breakage can be prevented. Moreover, even if the falling period is lengthened, the bead appearance is not deteriorated because the influence on the droplet transfer state is small.

In order to demonstrate the pulse arc welding control method concerning Embodiment 1 of the present invention, it is a figure showing welding line Ps-Pe used as welding object as a straight line. 4 is a timing chart of each signal when performing test welding in the pulse arc welding control method according to Embodiment 1 of the present invention. In the pulse arc welding control method according to Embodiment 1 of the present invention, it is a timing chart of each signal when performing practical welding. It is a block diagram of the welding apparatus for enforcing the pulse arc welding control method concerning Embodiment 1 of the present invention. In the pulse arc welding control method concerning Embodiment 2 of the present invention, it is a timing chart of each signal when carrying out execution welding. It is a block diagram of the welding apparatus for enforcing the pulse arc welding control method which concerns on Embodiment 2 of this invention. It is a current and voltage waveform diagram of pulse arc welding in the prior art. It is a figure which shows an arc state when magnetic blowing generate | occur | produces in a prior art. FIG. 6 is a current / voltage waveform diagram when magnetic blow occurs in pulse arc welding of the prior art. It is a current / voltage waveform diagram showing magnetic blow countermeasure control for preventing arc breakage due to magnetic blow in the prior art.

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

[Embodiment 1]
FIG. 1 is a diagram showing a welding line Ps-Pe to be welded as a straight line in order to describe the pulse arc welding control method according to Embodiment 1 of the present invention. In the figure, the left end Ps indicates the welding start position, and the right end Pe indicates the welding end position. This welding line Ps-Pe is subjected to pulse arc welding using a robot. The pulse arc welding is performed by dividing into test welding and execution welding.

(1) Test welding As will be described later with reference to FIG. 2, welding is started along the weld line from the welding start position Ps while determining the occurrence of magnetic blow. When the occurrence of magnetic blow is determined during welding, the position on the weld line is stored. In the figure, it is assumed that the occurrence of magnetic blow is determined in the section between A1 and A2 on the weld line. This section A1-A2 will be referred to as a magnetic blowing generation section. Therefore, in the figure, the weld line is divided into three sections. The first section Ps-A1 is a section in which no magnetic blowing has occurred, the second section A1-A2 is a section in which magnetic blowing has occurred, and the third section A2-Pe is a section in which no magnetic blowing has occurred. That is, in the test welding, an operation for discriminating and storing the magnetic blow occurrence section on the weld line is performed. As described above, the determination of the occurrence of magnetic blow can be made by the fact that the base voltage has risen above the reference voltage value. It can also be performed when the base voltage increase rate is equal to or higher than the reference increase rate. The magnetic blowing generation section A1-A2 can be determined as a section in which the pulse cycle in which the magnetic blowing generation is determined is continuous. In the figure, although there is one magnetic blowing occurrence section, there may be a plurality of sections. In addition, in order to provide a margin for discriminating the magnetic blow occurrence section, the start position of the magnetic blow occurrence section is a position that is a predetermined distance before the position where the occurrence of the magnetic blow was first determined during welding (welding The start position Ps may be a front limit). Similarly, the end position of the magnetic blow generation section may be a position that is a predetermined distance after the position at which the last occurrence of magnetic blow was determined during welding (the welding end position Pe is the rear limit). . The predetermined distance is set to an appropriate value by experiment within a range of about 3 to 10 mm. Further, the magnetic blowing occurrence section may be a section in which the occurrence of magnetic blowing is determined to be greater than the reference period per unit pulse period. For example, a section in which occurrence of magnetic blowing is determined in 5 pulse periods per 10 pulse periods is defined as a magnetic blowing generation section. The unit pulse period is set to an appropriate value by experiment in the range of about 10 to 100, and the reference pulse number is set to an appropriate value by experiment in the range of about 30 to 100% as a percentage.

(2) Practical Welding During the practicing, when the first section Ps-A1 is welded, it is a section where no magnetic blow is generated, so the normal pulse arc welding described above with reference to FIG. 7 is performed. When the second section A1-A2 is welded, since it is a section where magnetic blowing is occurring, pulse arc welding to which magnetic blow countermeasure control described later in FIG. 2 is added is performed. When the third section A2-AE is welded, it is a section in which no magnetic blow occurs, so the normal pulse arc welding described above with reference to FIG. 7 is performed again.

  FIG. 2 is a timing chart of each signal when test welding is performed in the pulse arc welding control method according to Embodiment 1 of the present invention. (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, (C) shows the time change of the magnetic blow occurrence determination signal Ad, (D) shows the time change of the magnetic blow occurrence section signal Pd. This figure is when the second section A1-A2 is test welded in FIG. 1 described above. This figure corresponds to FIGS. 7 and 10 described above, and the description of the same operation will not be repeated. Hereinafter, the operation at the time of test welding will be described with reference to FIG.

  Since this figure is at the time of test welding, the magnetic blow occurrence section signal Pd remains at the low level as shown in FIG.

  In the pulse period Tf from time t1 to t2, during the rising period Tu, as shown in FIG. 6A, the rising transition current Iu that increases from the base current Ib to the peak current Ip is energized, and FIG. As shown, the rising transition voltage rising from the base voltage Vb to the peak voltage Vp is applied between the welding wire and the base material. During the subsequent peak period Tp, as shown in FIG. 6A, a peak current Ip having a large current value greater than the critical value is applied to transfer droplets from the welding wire, as shown in FIG. In addition, a peak voltage Vp proportional to the arc length is applied. During the subsequent falling period Tk, as shown in FIG. 9A, the falling transition current Ik that decreases from the peak current Ip to the base current Ib is energized, and as shown in FIG. To the base voltage Vb is applied. During the subsequent base period Tb, as shown in FIG. 5A, a base current Ib having a small current value less than the critical value is energized so as not to form droplets, and as shown in FIG. In addition, a base voltage Vb proportional to the arc length is applied. The arc length is longer during the peak period Tp and shorter during the base period Tb.

  Since the arc length control method is frequency modulation control, the rising period Tu, the peak period Tp, the falling period Tk, the peak current Ip, and the base current Ib are set to predetermined values and the base period Tb ( The pulse period Tf) is determined by feedback control so that the average value of the welding voltage Vw becomes equal to a predetermined voltage setting value.

  At time t11 in the base period Tb, the arc length is increased because the magnetic blow is generated and the arc is deflected, and the base voltage Vb increases from the normal value and increases as shown in FIG. At time t12, the value of the base voltage Vb becomes equal to or higher than a predetermined reference voltage value Vt indicated by a broken line. When it is determined that the base voltage value Vb is equal to or higher than the reference voltage value Vt, the magnetic blow occurrence determination signal Ad changes to a high level as shown in FIG. This magnetic blow occurrence determination signal Ad maintains a high level state until time t2 when the next pulse period Tf is started. Even if the magnetic blow occurrence determination signal Ad changes to a high level, the base current Ib does not increase and maintains a normal value. For this reason, since the deflection of the arc length by magnetic blowing continues, the base voltage Vb maintains a state exceeding the reference voltage value Vt until time t2 when the next pulse period Tf is started.

  Similarly, at time t21 during the base period Tb, the arc length is increased due to the occurrence of magnetic blow and the arc is deflected, and the base voltage Vb increases from the normal value and increases as shown in FIG. Become. Since the subsequent operations are the same, the description will not be repeated.

  FIG. 3 is a timing chart of each signal when performing welding in the pulse arc welding control method according to Embodiment 1 of the present invention. (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, (C) shows the time change of the magnetic blow occurrence determination signal Ad, (D) shows the time change of the magnetic blow occurrence section signal Pd. This figure corresponds to FIG. 2 described above, and description of the same operation will not be repeated. Since this figure is a timing chart when welding the second section A1-A2, which is the section in which the magnetic blow described above in FIG. 1, is generated, as shown in FIG. The signal Pd is at a high level. Hereinafter, control for preventing arc breakage due to magnetic blowing will be described with reference to FIG.

  In the pulse period Tf from time t1 to t2, during the rising period Tu, as shown in FIG. 6A, the rising transition current Iu that increases from the base current Ib to the peak current Ip is energized, and FIG. As shown in FIG. 6, a rising transition voltage that rises from the base voltage Vb, which is larger than the normal value, to the peak voltage Vp is applied due to magnetic blowing. During the subsequent peak period Tp, the peak current Ip is energized as shown in FIG. 5A, and the peak voltage Vp proportional to the arc length is applied as shown in FIG. During the subsequent corrected fall period Tks, as shown in FIG. 5A, the corrected falling transition current Iks that decreases from the peak current Ip to the base current Ib is energized, and as shown in FIG. A falling transition voltage that falls from the voltage Vp to the base voltage Vb is applied. During the subsequent base period Tb, the base current Ib is energized as shown in FIG. 5A, and the base voltage Vb proportional to the arc length is applied as shown in FIG.

  The rising period Tu, the peak period Tp, the peak current Ip, and the base current Ib are set to the same values as in the above-described test welding of FIG. 2 and when the magnetic blow generation interval signal Pd is at the low level. That is, the values of these parameters are constant values regardless of the state of the magnetic blow occurrence section signal Pd shown in FIG.

  On the other hand, the corrected falling period Tks is set to a period longer than the falling period Tk at the time of test welding in FIG. For this reason, the descending speed of the modified descending transition current Iks is slower than the descending speed of the descending transition current Ik. In other words, when the magnetic blow generation interval signal Pd is at a high level, correction is made so that the descending speed of the descending transition current becomes slow.

  During the falling period Tk at the time of test welding, the falling transition current Ik changes from the peak current Ip to the base current Ib at a fast falling speed. However, since the change in the arc length needs to melt the welding wire, it changes with a delay from the descending speed of the descending transition current Ik. Therefore, even if the welding current Iw changes to the base current Ib in the base period Tb, the arc length is maintained for a while longer than the convergence value. Since the base current Ib is a small current value, the arc rigidity is weak. As a result, since the arc stiffness becomes weak when the arc length is long, the arc tends to be deflected by magnetic blowing.

  On the other hand, during the modified fall period Tks shown in the figure, the modified fall transition current Iks changes from the peak current Ip to the base current Ib at a slow fall rate. The slow descending speed is a speed at which the descending speed of the modified descending transition current Iks becomes slower than the arc length changing speed. In this way, even when the base current Ib, in which the arc rigidity becomes weaker and enters the base period Tb, the arc length is already in a short state close to the convergence value at that time. For this reason, even if magnetic blow occurs, the deflection of the arc length is small, and the arc is not cut off. As a result, the base voltage Vb increases in a range smaller than the reference voltage value Vt between times t11 and t3 because a small arc deflection occurs. Therefore, as shown in FIG. 5C, the magnetic blow occurrence determination signal Ad remains at the low level.

  Since the operation during the pulse period Tf from time t2 to t3 is the same as the operation during the pulse period Tf from time t1 to t2, the description will not be repeated.

  As described above, when the magnetic blow generation interval signal Pd is at the high level, the arc at the time when the base period Tb where the rigidity of the arc is weakened by slowing the descending speed of the descending transition current during the falling period is entered. The length can be shortened. For this reason, even if magnetic blowing occurs, it is possible to prevent the arc from being greatly deflected, and arc breakage can be prevented. In addition, even if the descending speed of the descending transition current is decreased, the bead appearance is not deteriorated because the influence on the droplet transfer state is small. However, since the spatter generation amount tends to slightly increase as the descending speed becomes slow, when the magnetic blowing generation section signal Pd is at the low level (in the section where no magnetic blowing occurs), the descending speed is increased. It is better to leave. Therefore, when the magnetic blow occurrence section signal Pd is at a high level, the descending speed is slowed down.

  A numerical example of each parameter described above is shown below. Tu = 0.4 ms, Tp = 1.2 ms, Tk = 0.4 ms, Tks = 1.6 ms, Ip = 450 A, Ib = 50 A. In this case, the descending speed of Ik is 1000 A / ms, and the descending speed of Iks is 250 A / ms, which is four times slower.

  FIG. 4 is a block diagram of a welding apparatus for carrying out the pulse arc welding control method according to Embodiment 1 of the present invention. The welding apparatus is mainly composed of a welding power source PS surrounded by a broken line, a robot control device RC, a robot (not shown), and the like. Hereinafter, each block will be described with reference to FIG.

  The welding power source PS is composed of the following blocks. However, a circuit for feeding control of the welding wire 1 is omitted. The power supply main circuit MC receives an AC commercial power supply (not shown) such as three-phase 200V as input, performs output control such as inverter control in accordance with a drive signal Dv described later, and generates a welding voltage Vw and welding current Iw suitable for welding. Output. Although not shown, this power supply main circuit MC is a primary rectifier circuit that rectifies an AC commercial power supply, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current into high-frequency alternating current according to the drive signal Dv, An inverter transformer that steps down the high frequency alternating current to a voltage value suitable for welding and a secondary rectifier circuit that rectifies the stepped down high frequency alternating current are provided. Reactor WL is inserted between the + side output of power supply main circuit MC and welding torch 4 and smoothes the output of power supply main circuit MC. The welding wire 1 is fed through the welding torch 4 by the rotation of a feeding roll 5 of a wire feeder (not shown), and an arc 3 is generated between the welding wire 1 and the base material 2. The wire feeder and the welding torch 4 are mounted on the 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 is conducted.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The voltage averaging circuit VAV averages (passes through the low-pass filter) the voltage detection signal Vd and outputs a voltage average signal Vav. The voltage setting circuit VR outputs a voltage setting signal Vr having a desired value. The voltage error amplification circuit EV amplifies an error between the voltage setting signal Vr (+) and the voltage average signal Vav (−) and outputs a voltage error amplification signal Ev.

  The V / F converter VF outputs a pulse period signal Tf which is a trigger signal that becomes a high level for a short time at a frequency corresponding to the voltage error amplification signal Ev. The period when the pulse period signal Tf is at a high level for a short time is one pulse period.

  The rising period setting circuit TUR outputs a predetermined rising period setting signal Tur. The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr. The fall period setting circuit TKR receives a magnetic blow generation section signal Pd from the robot controller RC described later as an input, and sets a predetermined fall period Tk when the magnetic blow generation section signal Pd is at a low level. The signal is output as a signal Tkr. When the signal is at a high level, a predetermined corrected fall period Tks is output as the fall setting signal Tkr. As described above, Tk <Tks.

  The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr. The base current setting circuit IBR outputs a predetermined base current setting signal Ibr.

The current setting circuit IR includes the pulse period signal Tf, the rising period setting signal Tur, the peak period setting signal Tpr, the falling setting signal Tkr, the peak current setting signal Ipr, and the base current setting. With the signal Ibr as an input, every time the pulse period signal Tf changes to a high level for a short time, the following processing is performed to output a current setting signal Ir.
1) During the period determined by the rising period setting signal Tur, the current setting signal Ir that rises linearly from the value of the base current setting signal Ibr to the value of the peak current setting signal Ipr is output.
2) Subsequently, during the period determined by the peak period setting signal Tpr, the peak current setting signal Ipr is output as the current setting signal Ir.
3) Subsequently, during the period determined by the falling period setting signal Tkr, the current setting signal Ir that falls linearly from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr is output.
4) Subsequently, the base current setting signal Ibr is output as the current setting signal Ir during a period until the pulse period signal Tf again becomes High level for a short time.

  The magnetic blow occurrence determination circuit AD receives the current setting signal Ir, the base current setting signal Ibr, the voltage detection signal Vd, and the pulse period signal Tf, and the value of the current setting signal Ir is the base current setting. When the value of the voltage detection signal Vd in a period equal to the value of the signal Ibr (base period Tb) becomes equal to or higher than a predetermined reference voltage value Vt, it is set to High level, and thereafter, when the pulse period signal Tf becomes High level, Low. A magnetic blow occurrence determination signal Ad that is reset to the level is output.

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. 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 drive circuit DV receives the current error amplification signal Ei and a start signal On from the robot controller RC described later, and performs PWM modulation based on the current error amplification signal Ei when the start signal On is at a high level (welding start). Control is performed to output a drive signal Dv for driving the inverter circuit in the power supply main circuit MC. When the start signal On is at a low level (welding stop), the drive signal Dv is not output.

The robot controller RC receives the magnetic blow occurrence determination signal Ad as described above, and the test welding mode or the execution welding mode is selected and performs the following operation in each mode, and the start signal On and the magnetic blow The generation interval signal Pd is output.
1) In the test welding mode, as described above with reference to FIG. 1, when the welding torch 4 is moved to the welding start position Ps, the start signal On is set to High level and output. Thereafter, welding is performed along the weld line in accordance with a work program taught in advance. During this welding, a section in which the magnetic blow occurrence determination signal Ad becomes High level during one pulse period is stored as a magnetic blow occurrence section. When the welding torch 4 is moved to the welding end position Pe, the start signal On is set to the Low level to end the welding. In the test welding mode, a low level magnetic blow occurrence section signal Pd is output.
2) In the working welding mode, as described above with reference to FIG. 1, when the welding torch 4 is moved to the welding start position Ps, the start signal On is set to the high level and output. Thereafter, welding is performed along the weld line according to the work program. During the welding, when the position of the welding torch 4 is in the stored magnetic blow generation section, the magnetic blow generation section signal Pd is set to High level and output. When the welding torch 4 is moved to the welding end position Pe, the start signal On is set to the Low level to end the welding.

  According to the first embodiment described above, test welding for determining and storing the magnetic blow occurrence section on the weld line is performed by increasing the welding voltage during the base period, and the stored magnetic blow on the weld line is performed at the time of execution. When welding the generating section, the falling period is lengthened. In the first embodiment, the falling period is lengthened by slowing the descending speed of the descending transition current. Thereby, in Embodiment 1, the arc length at the time of entering the base period Tb where the arc rigidity becomes weak can be made short. For this reason, even if magnetic blowing occurs, it is possible to prevent the arc from being greatly deflected, and arc breakage can be prevented. Moreover, even if the falling period is lengthened, the bead appearance is not deteriorated because the influence on the droplet transfer state is small.

[Embodiment 2]
In the second embodiment, when the falling transition current reaches the reference current value, the value is maintained for a predetermined period, thereby extending the falling period and making the reference current value smaller than the peak current value. Set to a value larger than the value of.

  In the second embodiment, the operations in FIG. 1 and FIG. 2 are the same, and therefore the description thereof will not be repeated.

  FIG. 5 is a timing chart of each signal when performing welding in the pulse arc welding control method according to Embodiment 2 of the present invention. (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, (C) shows the time change of the magnetic blow occurrence determination signal Ad, (D) shows the time change of the magnetic blow occurrence section signal Pd. This figure corresponds to FIG. 3 described above, and the description of the same operation will not be repeated. This figure is different from FIG. 3 only in the operation during the corrected fall period Tks. Hereinafter, this different operation will be described with reference to FIG.

  As shown in FIG. 4D, since the magnetic blow generation interval signal Pd is at a high level, during the corrected fall period Tks in the pulse period Tf from time t1 to t2, as shown in FIG. When the current falls from the peak current Ip and reaches a predetermined reference current value It, that value is maintained for a predetermined period, and thereafter, the corrected falling transition current Iks that switches to the base current Ib is energized. As shown in FIG. 5B, the descending fiber voltage is similar to the current waveform. Here, Tk <Tks and Ib <It <Ip.

  The reference current value It is set to a current value that can suppress the deflection of the arc due to the magnetic blow due to the arc rigidity even in the state of a long arc length during the peak period Tp. The reference current value It is set to about 20% to 40% of the peak current Ip. The predetermined period is set to a time required to shorten the arc length to be less affected by the arc deflection caused by magnetic blowing. The descending speed of the first half of the modified descending transition current Iks is set to the same value as the descending speed of the descending transition current Ik at the time of test welding and when the magnetic blow occurrence section signal Pd is at the low level.

  A numerical example of each parameter described above is shown below. Tu = 0.4 ms, Tp = 1.2 ms, Tk = 0.4 ms, Tks = 1.6 ms, predetermined period = 1.3 ms, Ip = 450 A, Ib = 50 A, It = 150 A. In this case, the descending speed of Ik is 1000 A / ms, and the descending speed of the first half of Iks is the same value.

  During the corrected falling period Tks, the corrected falling transition current Iks that switches to the base current Ib after maintaining the state of the reference current value It from the peak current Ip for a predetermined period is energized. In this way, even when the base current Ib, in which the arc rigidity becomes weaker and enters the base period Tb, the arc length is already in a short state close to the convergence value at that time. For this reason, even if magnetic blow occurs, the deflection of the arc length is small, and the arc is not cut off.

  As described above, when the magnetic blow generation interval signal Pd is at the high level, the falling transition current during the falling period is held at the reference current value It for a predetermined period, thereby entering the base period Tb in which the arc rigidity becomes weak. The arc length at the time can be made short. For this reason, even if magnetic blowing occurs, it is possible to prevent the arc from being greatly deflected, and arc breakage can be prevented. In addition, even in this way, since the influence on the droplet transfer state is small, the bead appearance is not deteriorated.

  FIG. 6 is a block diagram of a welding apparatus for performing the pulse arc welding control method according to Embodiment 2 of the present invention. The welding apparatus is mainly composed of a welding power source PS surrounded by a broken line, a robot control device RC, a robot (not shown), and the like. This figure corresponds to FIG. 2 described above, and the same reference numerals are given to the same blocks, and description thereof will not be repeated. This figure is obtained by replacing the current setting circuit IR of FIG. 4 with a second current setting circuit IR2. Hereinafter, this block will be described with reference to FIG.

The second current setting circuit IR2 receives the pulse period signal Tf, the rising period setting signal Tur, the peak period setting signal Tpr, the falling period setting signal Tkr, the peak current setting signal Ipr, the base current setting signal Ibr, and the magnetic blow generation interval signal Pd. As an input, every time the pulse period signal Tf changes to a high level for a short time, the following processing is performed to output a current setting signal Ir.
1) During the period determined by the rising period setting signal Tur, the current setting signal Ir that rises linearly from the value of the base current setting signal Ibr to the value of the peak current setting signal Ipr is output.
2) Subsequently, during the period determined by the peak period setting signal Tpr, the peak current setting signal Ipr is output as the current setting signal Ir.
3) Subsequently, during the period determined by the falling period setting signal Tkr, when the magnetic blow generation period signal Pd is at the low level, the value falls linearly from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr. Current setting signal Ir to be output, and when the magnetic blow occurrence section signal Pd is at a high level, the value falls from the value of the peak current setting signal Ipr at the same descending speed as when the magnetic blow occurrence section signal Pd is at a low level. When the reference current value It is reached, a current setting signal Ir that maintains that value is output.
4) Subsequently, the base current setting signal Ibr is output as the current setting signal Ir during a period until the pulse period signal Tf again becomes High level for a short time.

  According to the second embodiment described above, test welding is performed to determine and memorize the magnetic blow occurrence section on the weld line by increasing the welding voltage during the base period, and the stored magnetic blow on the weld line at the time of execution. When welding the generating section, the falling period is lengthened. In the second embodiment, when the falling transition current reaches a predetermined reference current value, the falling period is lengthened by maintaining that value for a predetermined period. Thereby, in Embodiment 2, the arc length at the time of entering the base period Tb where the arc rigidity becomes weak can be made short. For this reason, even if magnetic blowing occurs, it is possible to prevent the arc from being greatly deflected, and arc breakage can be prevented. Moreover, even if the falling period is lengthened, the bead appearance is not deteriorated because the influence on the droplet transfer state is small. Moreover, in Embodiment 2, it can respond by changing a reference electric current value and / or a predetermined period according to the strength of magnetic blowing, and the influence on a welding state is made smaller than Embodiment 1. be able to.

  In contrast to the first and second embodiments described above, the integration of the welding current Iw from the start point of the rising period to the end point of the falling period before and after the occurrence of the magnetic blow is determined and the falling period is lengthened. The peak period Tp and / or the peak current Ip may be changed so that the value becomes constant. In this way, the droplet transfer state becomes even better. In the first and second embodiments described above, the case where the arc length control is the frequency modulation control has been described, but the same applies to the case of the pulse width modulation control.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll AD Magnetic blow generation | occurrence | production discrimination circuit Ad Magnetic blow generation | occurrence | production discrimination signal DV Drive circuit Dv Drive signal EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit Ev Error amplification signal Iav Welding current average value Ib Base current IBR Base current setting circuit Ibr Base current setting signal ID Current detection circuit Id Current detection signal Ik Falling transition current Iks Modified falling transition current Ip Peak current IPR Peak current setting circuit Ipr Peak current setting Signal IR Current setting circuit Ir Current setting signal IR2 Second current setting circuit It Reference current value Iu Rising transition current Iw Welding current MC Power supply main circuit On Start-up signal Pd Magnetic blowing generation section signal PS Welding power supply RC Robot controller Tb Base period Tf Pulse period (signal)
TKR falling period setting circuit Tkr falling period setting signal Tks modified falling period Tp peak period TPR peak period setting circuit Tpr peak period setting signal Tu rising period TUR rising period setting circuit Tur rising period setting signal VAV voltage averaging circuit Vav welding Voltage average value / voltage average signal Vb base voltage VD voltage detection circuit Vd voltage detection signal VF V / F converter Vp peak voltage VR voltage setting circuit Vr voltage setting signal Vt reference voltage value Vw welding voltage WL reactor

Claims (3)

In addition to feeding the welding wire, a rising transition current rising from the base current to the peak current is supplied during the rising period, the peak current is supplied during the peak period, and the peak current is supplied from the peak current during the falling period. In a pulse arc welding control method of energizing a falling transition current that decreases to a current, energizing the base current during a base period, and repeatedly energizing these welding currents as one pulse period,
With the increase of the welding voltage during the base period, test welding is performed to determine and store the magnetic blowing occurrence section on the weld line,
At the time of execution, when welding the memorized magnetic blow occurrence section on the weld line, the falling period is lengthened,
The pulse arc welding control method characterized by the above-mentioned. Increasing the falling period by slowing the descending speed of the descending transition current,
The pulse arc welding control method according to claim 1. When the falling transition current reaches a predetermined reference current value, by maintaining the value for a predetermined period, the falling period is lengthened, and the reference current value is smaller than the peak current value. Set to a value greater than
The pulse arc welding control method according to claim 1.

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