JP2012110951A - Method of controlling pulsed arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of controlling pulsed arc welding adapted to inhibit worsening of a bead appearance due to magnetic blow in pulsed arc welding.SOLUTION: The method of controlling pulsed arc welding is a method adapted to perform, in combination with feed of a welding wire, welding in repetition with a peak current in a peak time interval and a base current in a base time interval conducted as one pulse period, in which, through raising a welding voltage in the base time interval, a test welding is executed to determine the magnetic-blow-generating section A1 to A2 on the weld line Ps to Pe and store the section in memory, and, in an implementing process, the welding current waveform parameter is automatically altered to inhibit the occurrence of magnetic blow, when the stored magnetic-blow-generating section A1 to A2 on the weld line Ps to Pe is subjected to welding. The altering of the welding current waveform parameter means the increase of the base current. Because the base current increases within the magnetic-blow-generating section A1 to A2 by this processing, the rigidity of an arc enhances and the deflection of the arc due to a magnetic blow is inhibited. As a result, the bead appearance can be prevented from worsening.

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 peak current having a large current value that is greater than or equal to the critical value is applied during the peak period, and a base current having a small current value that is less than the critical value is applied during the base period. Welding is performed repeatedly. 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. 5 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 peak period Tp from time t1 to t2, a peak current Ip having a large current value equal to or higher than the critical value is energized to transfer droplets from the welding wire as shown in FIG. ), A peak voltage Vp proportional to the arc length is applied between the welding wire and the base material. The critical value of a steel wire having a diameter of 1.2 mm is about 280A.

  During the base period Tb from time t2 to t3, as shown in FIG. 5A, the base current Ib having a small current value less than the critical value is energized in order to prevent the formation of droplets. ), The base voltage Vb is applied. Welding is performed by repeating the period from time t1 to t3 as one period (pulse period Tf).

  By the way, in order to perform good pulse arc welding, it is important to maintain the arc length at an appropriate value. In order to maintain the arc length at an appropriate value, the following arc length control (output control of the welding power source) is performed. The 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 output for changing the welding current average value Iav indicated by the broken line in FIG. 5A so that the detected value becomes equal to the welding voltage set value corresponding to the appropriate arc length. Take control. When the welding voltage average value Vav is larger than the welding voltage set value, the arc length is longer than the appropriate value. Therefore, the welding current average value Iav is decreased to reduce the wire melting rate and shorten the arc length. To do. On the other hand, when the welding voltage average value Vav is smaller than the welding voltage set value, the arc length is shorter than the appropriate value, so the welding current average value Iav is increased to increase the wire melting rate and the arc length is increased. Like that. 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, as a means for changing the welding current average value Iav, changing the pulse period Tf is performed. That is, the pulse period Tf is feedback controlled (arc length control) so that the welding voltage average value Vav becomes equal to the welding voltage setting value. At this time, the peak period Tp, the peak current Ip, and the base current Ib are set to predetermined values. The peak period Tp is set to about 1.0 to 1.5 ms, the peak current Ip is set to about 500 to 600 A, and the base current Ib is set to about 20 to 60 A. 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. This arc length control method is called frequency modulation control.

  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. 6 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 stiffness is weak and the deflection is greatly caused 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. If arc breaks due to magnetic blowing occur many times, the arc generation state becomes unstable, and a large amount of spatter is generated, and the bead appearance is deteriorated. Therefore, in pulse arc welding, it is important to suppress arc breaks due to magnetic blowing in order to obtain good welding quality.

  FIG. 7 is a current / voltage waveform diagram when magnetic blow 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.

  During the peak period Tp from time t1 to t2, a peak current Ip greater than the critical value is energized as shown in FIG. 6A, and a peak voltage approximately proportional to the arc length as shown in FIG. Vp is applied. During the base period Tb after time t2, a base current Ib less than the critical value is energized as shown in FIG. 6A, and a base voltage Vb that is substantially proportional to the arc length as shown in FIG. Is applied.

  When a magnetic blow occurs at time t21 and the arc is deflected, as shown in FIG. 5B, the arc length increases with the deflection of the arc, and the base voltage Vb gradually increases and increases. On the other hand, the base current Ib remains constant as shown in FIG. At time t3, 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 arc breakage 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. 8 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 t3, and a welding state in which magnetic blowing is generated during the subsequent pulse period from time t3 to t5. Show.

  During the pulse period from the time t1 to the time t3, since the magnetic blowing is not generated, the welding state is stable. The operation during this period is the same as that shown in FIG.

  During the peak period Tp from time t3 to t4, the peak current Ip is energized as shown in FIG. 9A, and the peak voltage Vp is applied as shown in FIG. The base period Tb starts from time t4, the base current Ib is energized as shown in FIG. 5A, and the normal base voltage Vb is applied as shown in FIG. At time t41 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 is increased and increased as shown in FIG. At time t42, 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 t42 to t43, 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 t42 to t43, 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 t43, 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 t41 and is canceled immediately after time t43. At time t43, the value of the base current Ib returns to the normal value as shown in FIG. During the remaining base period Tb from time t43 to t5, 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, the state in which the arc is deflected to some extent by magnetic blowing and the arc length is increased is determined. For this reason, since welding is performed in a state where the arc is deflected to some extent by magnetic blowing, the bead appearance may be deteriorated. That is, in the prior art, it is possible to prevent the bead appearance from remarkably deteriorating due to arc breakage due to magnetic blowing, but it is inevitable that the bead appearance is deteriorated to some extent.

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

In order to solve the above-described problem, the invention of claim 1 is directed to a pulse arc which feeds a welding wire and repeatedly welds a peak current during a peak period and a base current during a base period as one pulse period. In the welding control method,
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 stored magnetic blow occurrence section on the weld line, the welding current waveform parameter is automatically changed to suppress the occurrence of magnetic blow.
It is the pulse arc welding control method characterized by this.

The invention of claim 2 is that the change of the welding current waveform parameter is to increase the base current.
The pulse arc welding control method according to claim 1, wherein:

The invention of claim 3 is that the change of the welding current waveform parameter is to reduce the peak current and / or the peak period.
The pulse arc welding control method according to claim 1, wherein:

  According to the present invention, test welding is performed to discriminate and store a magnetic blow occurrence section on the weld line by increasing the welding voltage during the base period. When welding, the welding current waveform parameter is automatically changed to suppress the occurrence of magnetic blow. For this reason, since the deflection of the arc due to magnetic blowing can be suppressed, the bead appearance can be kept good.

It is the figure which showed the welding line Ps-Pe used as welding object as a straight line in order to demonstrate the pulse arc welding control method which concerns on embodiment of this invention. It is an electric current and voltage waveform diagram which shows the pulse arc welding control method which concerns on embodiment of this invention. FIG. 3 is a current / voltage waveform diagram different from FIG. 2 showing a pulse arc welding control method according to an embodiment of the present invention. It is a block diagram of the welding apparatus for enforcing the pulse arc welding control method concerning an embodiment of the 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.

  FIG. 1 is a diagram showing a welding line Ps-Pe to be welded as a straight line in order to explain the pulse arc welding control method according to the embodiment 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. The welding line Ps-Pe is subjected to pulse arc welding to which the magnetic blow countermeasure control described above with reference to FIG. 8 is added using a robot. The pulse arc welding is performed by dividing into test welding and execution welding.

(1) Test welding Welding is started from the welding start position Ps along the weld line while discriminating the deflection of the arc caused by the magnetic blow described above with reference to FIG. 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. When the magnetic blow is determined, as described above, the base current is increased to prevent arc interruption. Since it is test welding, the base current may not be increased. . 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) Execution Welding When performing welding, when welding the first section Ps-A1, the welding current waveform parameter remains at the normal value, and when welding the magnetic blowing generation section A1-A2, which is the second section. Automatically changes the welding current waveform parameter to a value at which the arc is not deflected by magnetic blowing, and returns the welding current waveform parameter to the normal value when welding the third section A2-Pe. The change in the welding current waveform parameter may be as follows.

a) The change in the welding current waveform parameter is to increase the base current Ib. The normal value of the base current Ib is about 20 to 60 A as described above. This is increased by about 1.5 to 2.0 times in the magnetic blowing generation section. This increased base current is referred to as a magnetic blow countermeasure base current Iba. When the base current Ib is increased, the arc rigidity is increased, and therefore it is difficult for the arc to be deflected by magnetic blowing. As a result, since the arc is not deflected, it is possible to suppress deterioration of the bead appearance. However, when the base current Ib is increased, the droplet transfer state may become slightly unstable, resulting in a slight increase in spatter. However, a slight increase in spatter has less influence on the welding quality than the bead appearance is deteriorated as in the prior art. The reason why the base current Ib is set to the normal value in the first section Ps-A1 and the third section A2-Pe that are not the magnetic blowing generation section is to avoid the increase in sputtering. Unlike the prior art, the base current Ib is not increased after the arc deflection due to magnetic blowing has progressed to some extent, but the base current Ib is increased before the arc deflection occurs, so the arc deflection is suppressed in advance. can do. Therefore, the increase value of the base current may be considerably smaller in this embodiment than in the prior art. This also reduces the influence on the bead appearance.

b) The change in the welding current waveform parameter is to reduce the peak current Ip and / or the peak period Tp. The normal value of the peak current Ip is about 500 to 600 A as described above, and the normal value of the peak period Tp is about 1.0 to 1.5 ms as described above. This is reduced by about 10 to 20% in the magnetic blowing generation section. This reduced peak current is called a magnetic blow countermeasure peak current Ipa, and the reduced peak period is called a magnetic blow countermeasure peak period Tpa. In this way, the base period Tb is shortened by the frequency modulation control described above. When the base period Tb is shortened, energization of the next peak current Ip is started when the arc is slightly deflected by magnetic blowing, and the arc deflection is corrected. As a result, since the deflection of the arc is reduced, it is possible to suppress deterioration of the bead appearance. However, if the peak current Ip and / or the peak period Tp is reduced, the droplet transfer state may be slightly unstable, and the generation of spatters is slightly increased. However, a slight increase in spatter has less influence on the welding quality than the bead appearance is deteriorated as in the prior art. The reason why the peak current Ip and the peak period Tp are set to normal values in the first section Ps-A1 and the third section A2-Pe that are not the magnetic blowing generation section is to avoid the increase in sputtering. Unlike the prior art, the base current Ib is not increased after the arc deflection due to magnetic blowing has progressed to some extent, but the peak current Ip and / or the peak period Tp is reduced before the arc deflection occurs. Arc deflection can be suppressed in advance.

  FIG. 2 is a current / voltage waveform diagram showing the pulse arc welding control method according to the embodiment of the present invention described above. 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, the period before time t3 corresponds to the first section Ps-A1 in FIG. 1, and the period after time t3 corresponds to the second section (magnetic blowing occurrence section) A1-A2 in FIG. Yes. Therefore, the time point t3 corresponds to the position A1 in FIG. This figure shows a case where the base current Ib is increased from the normal value and the magnetic blow countermeasure base current Iba is applied during the magnetic blow generation period, as shown in a) above. Further, this figure corresponds to FIG. 8 described above, and the operation in the period before time t3 is the same, so the description will be simplified.

  During the pulse period from the time t1 to the time t3, since it is in a section where no magnetic blow occurs, the welding state is stable. During the peak period Tp of the normal value from time t1 to t2, the peak current Ip of the normal value is energized as shown in FIG. 5A, and the peak voltage Vp is applied as shown in FIG. . During the base period Tb from time t2 to t3, the normal value base current Ib is energized as shown in FIG. 9A, and the normal value base voltage Vb is applied as shown in FIG. .

  The period after time t3 is determined as a magnetic blowing occurrence section by test welding. During the normal value peak period Tp from time t3 to t4, the normal value peak current Ip is energized as shown in FIG. 9A, and the peak voltage Vp is applied as shown in FIG. . The base period Tb starts from time t4, and a magnetic blow countermeasure base current Iba larger than the normal value is energized as shown in FIG. Further, during the period from time t4 to t41, the base voltage Vb having a normal value is applied as shown in FIG. At time t41 during the base period Tb, magnetic blowing occurs and a biased force acts on the arc. However, since the magnetic blowing countermeasure base current Iba is energized, the deflection of the arc does not affect the welding quality. It is very small. Due to this magnetic blowing, the base voltage Vb becomes slightly higher than the normal value during the period from the time t41 to the time t5 as shown in FIG. Since the rise of the base voltage Vb is slight, the base voltage Vb is considerably smaller than the reference voltage value Vt indicated by the broken line. Therefore, the occurrence of magnetic blow is not determined. The operation during the period from the time t3 to the time t5 is repeated during the magnetic blowing generation section A1-A2. And if a welding position enters 3rd area A2-Pe, it will return to the operation | movement of the period of time t1-t3.

  FIG. 3 is a current / voltage waveform diagram different from FIG. 2 showing the pulse arc welding control method according to the above-described embodiment of the present invention. 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, the period before time t3 corresponds to the first section Ps-A1 in FIG. 1, and the period after time t3 corresponds to the second section (magnetic blowing occurrence section) A1-A2 in FIG. Yes. Therefore, the time point t3 corresponds to the position A1 in FIG. Unlike FIG. 2, the figure shows that during the magnetic blow generation period, as shown in the above b), the peak current Ip is reduced from the normal value and changed to the magnetic blow countermeasure peak current Ipa, and the peak period Tp is normally set. This is a case where the value is reduced from the value and changed to the magnetic blow countermeasure countermeasure peak period Tpa. Further, this figure corresponds to FIG. 8 described above, and the operation in the period before time t3 is the same, so the description will be simplified.

  During the pulse period from the time t1 to the time t3, since it is in a section where no magnetic blow occurs, the welding state is stable. During the peak period Tp of the normal value from time t1 to t2, the peak current Ip of the normal value is energized as shown in FIG. 5A, and the peak voltage Vp is applied as shown in FIG. . During the base period Tb from time t2 to t3, the normal value base current Ib is energized as shown in FIG. 9A, and the normal value base voltage Vb is applied as shown in FIG. .

  The period after time t3 is determined as a magnetic blowing occurrence section by test welding. During the magnetic blow countermeasure peak period Tpa from time t3 to t4, the magnetic blow countermeasure peak current Ipa is energized as shown in FIG. 5A, and the peak voltage Vp is applied as shown in FIG. . The base period Tb starts from time t4, and a normal value base current Ib is energized as shown in FIG. Further, during the period from time t4 to t41, the base voltage Vb having a normal value is applied as shown in FIG. The time length of the base period from time t4 to t5 is shorter than the time length of the base period from time t2 to t3. This is because the base period is shortened by the above-described frequency modulation control because the peak current and the peak period are small. At time t41 in the base period Tb, magnetic blowing occurs and biased force acts on the arc. However, since the base period is short, energization of the next magnetic blowing countermeasure peak current Ipa is started immediately thereafter, This deflection is corrected in a state where only a little progress has been made. Due to this magnetic blowing, the base voltage Vb becomes slightly higher than the normal value during the period from the time t41 to the time t5 as shown in FIG. Since the rise of the base voltage Vb is slight, the base voltage Vb is considerably smaller than the reference voltage value Vt indicated by the broken line. Therefore, the occurrence of magnetic blow is not determined. The operation during the period from the time t3 to the time t5 is repeated during the magnetic blowing generation section A1-A2. And if a welding position enters 3rd area A2-Pe, it will return to the operation | movement of the period of time t1-t3. When the peak current and / or peak period is reduced, the base period is shortened by frequency modulation control, so that the arc deflection due to magnetic blowing is corrected immediately in the initial state, thus preventing the influence on the welding quality. be able to.

  FIG. 4 is a block diagram of a welding apparatus for carrying out the above-described pulsed arc welding control method according to the embodiment 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, It comprises 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. 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.

  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 pulse period signal Tf is a signal that determines a frequency having a peak period and a base period as one period. The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr. The peak period timer circuit TTP receives the peak period setting signal Tpr and the pulse period signal Tf as described above, and becomes High level only for a period determined by the peak period setting signal Tpr every time the pulse period signal Tf changes to High level for a short time. After that, the peak period signal Ttp that is low level is output until the pulse period signal Tf next becomes high level. Therefore, the peak period signal Ttp is a signal that is at a high level during the peak period and is at a low level during the base period.

  The magnetic blow occurrence determination circuit AD receives the voltage detection signal Vd and the peak period signal Ttp as an input, and the reference of the value of the voltage detection signal Vd when the peak period signal Ttp is at the low level (base period) is predetermined. Only when the voltage value is equal to or higher than the voltage value, the magnetic blow occurrence determination signal Ad that becomes a high level is output. In other words, this magnetic blow occurrence determination signal Ad is a signal that determines that the base voltage has risen due to the deflection of the arc caused by the magnetic blow and becomes a high level. As described above, the occurrence of the magnetic blow may be determined as a period in which the decrease rate becomes equal to or higher than the reference decrease rate after the increase rate of the base voltage becomes equal to or higher than the reference increase rate.

  The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr. The base current setting circuit IBR receives the above-described magnetic blow occurrence determination signal Ad and a magnetic blow generation interval signal Pd from the robot controller RC described later, and increases in advance when the magnetic blow occurrence determination signal Ad is at a high level. Value base current setting signal Ibr is output, and when the magnetic blow occurrence determination signal Ad is at the low level and the magnetic blow occurrence section signal Pd is at the low level (non-magnetic blow occurrence section), a predetermined normal value base current is set. When the setting signal Ibr is output, the magnetic blow occurrence determination signal Ad is at the low level, and the magnetic blow occurrence section signal Pd is at the high level (magnetic blow occurrence section), a base current setting of a predetermined magnetic blow countermeasure base current value is performed. The signal Ibr is output. The switching circuit SW outputs the peak current setting signal Ipr as the current switching setting signal Isw when the peak period signal Ttp is high level, and the base current setting signal Ibr when the peak period signal Ttp is low level. Output as signal Isw.

  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 switching setting signal Isw 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 an activation signal On from the robot controller RC described later, and performs PWM modulation control based on the current error amplification signal Ei when the activation signal On is at a high level. A drive signal Dv for driving the inverter circuit is output. When the start signal On is at a low level, 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 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 according to the work program. 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 is moved to the welding end position Pe, the start signal On is set to the Low level to end the welding.
2) In the working welding mode, as described above with reference to FIG. 1, when the welding torch 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 according to the work program. During this welding, when the position of the welding torch 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 is moved to the welding end position Pe, the start signal On is set to the Low level to end the welding.

  In both the test welding and the execution welding, when the magnetic blow occurrence determination signal Ad becomes High level, the base current is increased to correct the deflection of the arc caused by the magnetic blow. However, in practical welding, the magnetic blow countermeasure base current is energized when in the magnetic blow generation section, so that the magnetic blow occurrence determination signal Ad is at a very rare case.

  This figure shows a case where the base current Ib is changed to the magnetic blow countermeasure base current Iba when the magnetic blow generation interval signal Pd is at a high level. In addition to this, as described above, when the magnetic blowing occurrence section signal Pd is at the high level, the peak current Ip is changed to the magnetic blowing countermeasure peak current Ipa, and the peak period Tp is changed to the magnetic blowing countermeasure peak period Tpa. You may do it. In this case, the magnetic blow generation section signal Pd from the robot controller RC may be input to the peak current setting circuit IPR and the peak period setting circuit TPR and the values thereof may be switched.

  According to the above-described embodiment, test welding is performed to discriminate and memorize the magnetic blowing 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 generation section, the welding current waveform parameter is automatically changed to suppress the occurrence of magnetic blowing. For this reason, since the deflection of the arc due to magnetic blowing can be suppressed, the bead appearance can be kept good.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll A1-A2 Magnetic blow generation | occurrence | production area AD Magnetic blow generation determination circuit Ad Magnetic blow generation determination signal DV Drive circuit Dv Drive signal EI Current error amplification circuit Ei Current error amplification signal EV voltage error amplification circuit Ev voltage error amplification signal Iav welding current average value Ib base current Iba magnetic blow countermeasure base current IBR base current setting circuit Ibr base current setting signal ID current detection circuit Id current detection signal Ip peak current Ipa magnetic blow countermeasure peak Current IPR Peak current setting circuit Ipr Peak current setting signal Isw Current switching setting signal Iw Welding current MC Power supply main circuit On Start signal Pd Magnetic blowing generation section signal Pe Welding end position Ps Welding start position RC Robot controller SW switching circuit Tb Base period Tf Pulse period (signal)
Tp Peak period Tpa Magnetic blow countermeasure peak period TPR Peak period setting circuit Tpr Peak period setting signal TTP Peak period timer circuit Ttp Peak period signal VAV Voltage averaging circuit Vav Voltage average signal / Welding voltage average value 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 Vt1 First reference voltage value Vt2 Second reference voltage value Vw Welding voltage WL reactor

Claims (3)

In the pulse arc welding control method of feeding welding wire and repeatedly welding the peak current during the peak period and the base current during the base period 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 stored magnetic blow occurrence section on the weld line, the welding current waveform parameter is automatically changed to suppress the occurrence of magnetic blow.
The pulse arc welding control method characterized by the above-mentioned. The change in the welding current waveform parameter is to increase the base current.
The pulse arc welding control method according to claim 1. The change in the welding current waveform parameter is to reduce the peak current and / or the peak period.
The pulse arc welding control method according to claim 1.

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