JP4319432B2 - Magnetic blow control method for consumable electrode pulse arc welding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic blow countermeasure control method for preventing arc breakage when magnetic blow occurs in consumable electrode pulse arc welding.
[0002]
[Prior art]
In consumable electrode pulse arc welding of steel or the like, welding is performed by repeatedly energizing a peak current that transfers droplets with a large current value and a base current that does not melt the wire tip with a small current value of about several tens of A. In pulse arc welding, it is important to maintain a one-pulse, one-droplet transfer state in which one droplet is transferred by applying a single peak current in order to obtain a beautiful bead appearance with less spattering. However, in pulse arc welding of steel or the like, a magnetic field is often formed around the arc by a welding current that energizes the base metal, and the arc is often deformed by receiving a force from this magnetic field. Such a state is generally called magnetic blow or arc blow.
[0003]
FIG. 5 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, the arc 3 is greatly deformed by the force from the magnetic field and the arc length is increased, as shown in FIG. When the deformation further increases, as shown in FIG. 3C, the arc cannot be maintained and an arc break occurs. In pulse arc welding, since a large current is applied during the peak period, the arc is highly rigid, and the arc hardly deforms 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 rigidity of the arc is weak and is greatly deformed by the force from the magnetic field. Therefore, it is 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.
[0004]
FIG. 6 is a current / voltage waveform diagram when magnetic blow occurs in pulse arc welding. FIG. 4A shows the time variation of the welding current Iw, and FIG. 4B shows the time change of the welding voltage Vw. Hereinafter, a conventional magnetic blow countermeasure control method will be described with reference to FIG.
[0005]
During the peak period Tp from time t1 to t2, a peak current Ip of about 400 to 600 A is energized as shown in FIG. 5A, and a peak approximately proportional to the arc length as shown in FIG. A voltage Vp is applied. During the base period Tb after time t2, a base current Ib of about several tens of A is energized as shown in FIG. 6A, and a base voltage approximately proportional to the arc length is shown in FIG. Vb is applied.
[0006]
When the magnetic blow occurs at time t21 and the arc is deformed, as shown in FIG. 5B, the arc length increases with the deformation of the arc, and the base voltage Vb gradually increases. On the other hand, the base current Ib remains constant as shown in FIG. At time t3, when the deformation of the arc due to the 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 voltage Vw becomes a no-load voltage of the maximum output voltage as shown in FIG.
[0007]
As described above, when magnetic blowing occurs, the welding voltage Vw increases rapidly. Therefore, as shown in FIG. 5B, it is possible to determine the occurrence of magnetic blowing by detecting that the welding voltage Vw during the base period Tb is equal to or higher than a predetermined reference voltage value Vt. In the prior art, the occurrence of magnetic blow is determined by this method, and the base current Ib is increased over several cycles in order to prevent arc breakage. This is because, as the base current Ib increases, the arc rigidity increases, so that arc deformation is suppressed and arc breakage is prevented. As another method, when magnetic blow is determined, the welding wire feed speed is increased to shorten the distance between the wire tip and the base metal, thereby suppressing arc deformation and preventing arc breakage. is there. (For example, see Patent Document 1)
[0008]
[Patent Document 1]
Japanese Utility Model Publication No. 59-73081 [0009]
[Problems to be solved by the invention]
The above-described conventional magnetic blow countermeasure control method has many problems as described below.
[0010]
(1) Problems in the method of discriminating magnetic blow FIG. 7 is a current / voltage waveform diagram when a short circuit occurs. In the pulse arc welding, when an appropriate welding condition is set, a short circuit between the welding wire and the base material occurs several times to several tens times per second. As shown in FIG. 5B, when a short circuit occurs, the arc disappears. And a big energy is needed when an arc generate | occur | produces again. As a result, an abnormal voltage is superimposed on the welding voltage Vw in order to supply this energy immediately after the short circuit is released. The abnormal voltage may be small or large as shown in FIG. Thus, in order to accurately determine the occurrence of the magnetic blow in the state where the abnormal voltage is generated immediately after the short circuit is released, the reference voltage value Vt must be set large as shown in FIG. Don't be. However, when the reference voltage value Vt is increased, the timing for determining the occurrence of magnetic blow is delayed. As a result, at the time of determination, the arc is about to break, and even if the base current is increased in this state, it is too late. On the other hand, if the reference voltage value Vt is set to be small, erroneous detection is caused by the abnormal voltage. Therefore, in the conventional magnetic blow discrimination method, the occurrence of magnetic blow cannot be discriminated early and accurately.
[0011]
{Circle around (2)} Problems of Increasing the Base Current After Determining the Generation of Magnetic Blowing When the base current is increased over several cycles, a certain effect is exhibited against arc breaks caused by magnetic blowing. However, by increasing the base current, the tip of the wire is melted greatly, so that the one-pulse / one-droplet transfer state is deviated. As a result, even if the arc break due to magnetic blowing can be suppressed, the arc state becomes unstable and the welding quality deteriorates. In addition, when the determination of the occurrence of magnetic blow is delayed, there are many cases where the arc break cannot be prevented even if the base current is increased.
[0012]
{Circle around (3)} Problems of Increasing the Feeding Speed after Determining the Generation of Magnetic Blowing The time from the occurrence of magnetic blowing to the end of the arc is about 1 ms to several tens of ms. For this reason, even if the feeding speed is increased after the determination of the occurrence of the magnetic blow, it is impossible to respond in this short time, and in many cases it is not possible to prevent arc interruption.
[0013]
As described above, the conventional technique has various problems, and thus it has not been possible to suppress the arc break due to magnetic blowing to such an extent that the welding quality does not deteriorate. Therefore, the present invention provides a control method for dealing with magnetic blow of consumable electrode pulse arc welding that can prevent arc breakage due to magnetic blow and obtain good welding quality.
[0014]
[Means for Solving the Problems]
In order to solve the above-described problem, the invention of claim 1 is a consumable electrode pulse arc welding in which energization of a peak current and a base current is repeated.
When the rate of increase in welding voltage when an arc is generated during the energization period of the base current is greater than or equal to a predetermined reference increase rate and a predetermined reference time has elapsed since the last short circuit was released It is determined that magnetic blowing has occurred, and the base current is rapidly increased to 200 A or more. If the welding voltage decreases during this magnetic blowing period, it is determined that the magnetic blowing has been canceled and the base current is set to a normal value. This is a control method for dealing with magnetic blow in consumable electrode pulse arc welding, characterized in that arc breakage due to the magnetic blow is suppressed.
[0016]
Furthermore, the invention according to claim 2 determines that the magnetic blowing has been canceled when the welding voltage decreases by a predetermined reference decrease value from the maximum value during the magnetic blowing period. This is a magnetic blow countermeasure control method for pulse arc welding.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 is a current / voltage waveform diagram showing a magnetic blow countermeasure control method according to an embodiment of the present invention. (A) shows the welding current Iw, (B) shows the welding voltage Vw, and (C) shows the increase in the welding voltage Vw during arc generation during the base period Tb in which no short-circuit has occurred immediately before. The time change of the rate Dv = dVw / dt is shown. In the figure, operations other than the base period Tb at times t2 to t3 are the same as those in FIG. Hereinafter, the operation in the base period Tb will be described with reference to FIG.
[0019]
(1) Method for discriminating occurrence of magnetic blowing As shown in FIG. 5B, when a short circuit occurs at time t21 and the short circuit is released at time t22 and an arc is regenerated, an abnormal voltage is superimposed as described above. . Thereafter, when magnetic blowing occurs from time t24, the welding voltage Vw starts to increase as shown in FIG. Along with this, as shown in FIG. 3C, the voltage increase rate Dv during arc generation gradually increases. Then, at time t25, when it is detected that the voltage increase rate Dv is equal to or higher than a predetermined reference increase rate Dvt, it is determined that magnetic blowing has occurred. In the above, the voltage increase rate Dv shown in FIG. 5C is the increase rate of the welding voltage Vw during the base period Tb in which the short-circuit has occurred and is released immediately before the abnormal voltage is not superimposed. The method for determining that a short circuit has not occurred immediately before is as follows. That is, as shown in FIG. 5B, the voltage increase rate Dv becomes equal to or higher than the reference increase rate Dvt after the time t23 when a predetermined reference time Td has elapsed from the time when the short circuit is released at time t22. Is detected to determine the occurrence of magnetic blow. This can prevent erroneous detection due to an abnormal voltage immediately after the short circuit is released. Furthermore, by using the rate of increase of the welding voltage, it is possible to detect the increase in the welding voltage due to the occurrence of magnetic blowing early and reliably. In addition to this, it may be determined that the abnormal voltage has converged based on the welding voltage value immediately after the short circuit. Immediately after the short circuit is released, the arc length is short, so that magnetic blowing is less likely to occur. Therefore, there is almost no magnetic blowing during the reference time Td. The value of the reference increase rate Dvt is, for example, about 5 V / ms, and the value of the reference time Td is, for example, about 2 ms.
[0020]
{Circle around (2)} When the magnetic blow occurrence control method is determined at time t25, the base current Ib is rapidly increased by a predetermined increased current value Iu as shown in FIG. Therefore, the base current value is Ib + Iu. The increased base current value is set to a large current value of 200 A or more. This is because, in order to restore the deformation of the arc due to the magnetic blow to the normal shape, it is necessary to energize a large current of 200 A or more to increase the rigidity of the arc. The maximum value of the base current (Ib + Iu) to be increased is about the peak current value so that the arc generation state does not become unstable. In the prior art described above, since the increase in the base current is intended to suppress the deformation of the arc, it is generally set to about 100 A or less. However, an object of the present invention is to restore the arc deformation to a normal shape by energizing a large current for a short time.
[0021]
{Circle around (3)} At the time t26, as shown in FIG. 5B, when it is detected that the welding voltage Vw during the magnetic blowing occurrence has decreased, it is determined that the magnetic blowing has been eliminated. The base current is returned to the normal value Ib. The decrease in the welding voltage Vw is determined by a decrease in the welding voltage Vw by a predetermined reference decrease value ΔV from the maximum value Vm during the magnetic blowing period, as shown in FIG. As another method, there is also a method of discriminating based on a decrease rate of the welding voltage Vw during the magnetic blowing period. The reference decrease value ΔV is set to about 5V, for example.
[0022]
As described above, the occurrence of magnetic blow is determined early, the base current is rapidly increased to a large current value, the arc deformation is restored to the normal shape in a short time, and the occurrence of magnetic blow is immediately determined to determine the base current. Return to normal value. Therefore, as shown in FIG. 5B, the base current increase period Tu is short, and therefore, there is almost no influence on the good arc state of 1 pulse / one droplet transfer.
[0023]
FIG. 2 is a diagram showing an arc state during the period from time t24 to t26 in FIG. 1 described above. Prior to the occurrence of magnetic blow immediately before time t24, as shown in FIG. In the engine in which the magnetic blow is generated from time t24 to t25, the arc 3 is slightly deformed by the magnetic blow as shown in FIG. As the base current increases from time t25 to time t26, the arc 3 returns to its normal shape as shown in FIG.
[0024]
FIG. 3 is a block diagram of the welding power source apparatus of the present invention. Hereinafter, each circuit will be described with reference to FIG.
[0025]
The power supply main circuit MC receives an AC commercial power supply (3-phase 200 V, etc.) as input, performs output control such as inverter control and thyristor phase control according to a current error amplification signal Ei described later, and a welding voltage Vw and welding current suitable for welding. Iw is output. The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 of the wire feeding device, and an arc 3 is generated between the welding wire 1 and the base material 2.
[0026]
The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The voltage averaging circuit VAV averages 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 frequency signal Tf having a frequency corresponding to the voltage error amplification signal Ev. The pulse frequency signal Tf is a signal for determining a frequency having a peak period and a base period as one cycle. The peak period timer circuit TTP outputs a peak period signal Ttp that is at a high level for the peak period Tp for each frequency of the pulse frequency signal Tf. Therefore, the peak period signal Ttp is a signal that is at a high level during the peak period Tp and is at a low level during the base period.
[0027]
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 switching circuit SW outputs the peak current setting signal Ipr as the current switching setting signal Isw when the peak period signal Ttp is at a high level, and outputs the base current setting signal Ibr when the peak period signal Ttp is at a low level. It is output as a current switching setting signal Isw.
[0028]
The reference time elapsed measurement circuit PM after the release of the short circuit receives the voltage detection signal Vd, and when an arc is generated during the base period and a predetermined reference time Td has elapsed since the previous short circuit release. A detection permission signal Pm that is at a high level is output. The voltage increase rate discriminating circuit DV detects the increase rate of the voltage detection signal Vd when the detection permission signal Pm is at a high level, and is a set signal that is at a high level when the detected value is equal to or higher than a predetermined reference increase rate Dvt. St is output. The voltage decrease determination circuit CV determines that the voltage detection signal Vd has dropped by a predetermined reference decrease value ΔV from the maximum value Vm during this period when an increase period signal Tu described later is at a high level (magnetic blowing period). Then, the reset signal Rs which becomes High level is output.
[0029]
The flip-flop circuit FF outputs an increase period signal Tu that becomes High level when the set signal St changes to High level and becomes Low level when the reset signal Rs changes to High level. The increase current setting circuit IUR outputs a predetermined increase current setting signal Iur only while the increase period signal Tu is at a high level.
[0030]
The adder circuit AD adds the current switching setting signal Isw and the increased current setting signal Iur, and outputs a current control setting signal Icr. 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 control setting signal Icr and the current detection signal Id, and outputs a current error amplification signal Ei. The above-described operation of FIG. 1 can be performed by the above-described welding power source apparatus.
[0031]
FIG. 4 is a comparison diagram of the number of occurrences of arc breaks due to magnetic blowing, showing an example of the effect of the present invention. This figure shows the case of MAG pulse welding of steel, in which the average welding current is set to 140 A, and the number of occurrences of arc breaks due to magnetic blowing during welding for 5 minutes is compared between the prior art and the present invention. Further, this figure shows a case where the position where the output terminal of the welding power supply device and the base material are connected by a cable (the ground position of the base material) is intentionally caused to cause magnetic blowing. As is apparent from the figure, arc breakage occurs about 3 times / minute in the prior art, but hardly occurs in the present invention. Further, in the present invention, since the increase period of the base current for preventing arc break due to magnetic blowing is short, the arc state always remains good. As a result, a good bead appearance with less spatter can be obtained.
[0032]
【The invention's effect】
According to the control method for dealing with magnetic blow of consumable electrode pulse arc welding according to the present invention, the occurrence of magnetic blow is surely determined at an early stage, the base current is rapidly increased to restore the deformation of the arc, and the occurrence of magnetic blow is determined to determine the base. By returning the current to the normal value, it is possible to prevent arc breakage due to magnetic blowing. Further, since the base current is increased only for a short time, there is almost no influence on the arc state. Further, the occurrence of magnetic blowing is not erroneously detected by the abnormal voltage immediately after the short circuit.
[Brief description of the drawings]
FIG. 1 is a current / voltage waveform diagram showing a magnetic blow countermeasure control method according to the present invention.
FIG. 2 is an arc state diagram when magnetic blow occurs in the present invention.
FIG. 3 is a block diagram of a welding power source device of the present invention.
FIG. 4 is a comparison diagram of the number of occurrences of arc breaks due to magnetic blowing, showing the effect of the present invention.
FIG. 5 is an arc state diagram when magnetic blow occurs in the prior art.
FIG. 6 is a current / voltage waveform diagram showing a magnetic blow countermeasure control method in the prior art.
FIG. 7 is a current / voltage waveform diagram showing superposition of an abnormal voltage immediately after a short circuit is released.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll AD Adder circuit DV Voltage rise rate discriminating circuit Dv Voltage rise rate Dvt Reference rise rate EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit Ev Voltage error Amplified signal FF Flip-flop circuit Ib Base current IBR Base current setting circuit Ibr Base current setting signal Icr Current control setting signal ID Current detection circuit Id Current detection signal Ip Peak current IPR Peak current setting circuit Ipr Peak current setting signal Isw Current switching setting signal Iu Increase current value IUR Increase current setting circuit Iur Increase current setting signal Iw Welding current MC Power supply main circuit PM Reference time elapsed measurement circuit Pm after short-circuit release Detection detection signal Rs Reset signal St Set signal SW Switching circuit Tb Base period Td Reference time Tf Pulse frequency signal Tp Peak period T P peak period timer circuit Ttp peak period signal Tu increase period (signal)
VAV voltage averaging circuit Vav voltage average signal Vb base voltage VD voltage detection circuit Vd voltage detection signal VF V / F converter Vm maximum value Vp peak voltage VR voltage setting circuit Vr voltage setting signal Vt reference voltage value Vw welding voltage ΔV reference decrease value CV voltage decrease discrimination circuit

Claims (2)

In consumable electrode pulse arc welding that repeats energization of peak current and base current,
When the rate of increase in welding voltage when an arc is generated during the energization period of the base current is greater than or equal to a predetermined reference increase rate and a predetermined reference time has elapsed since the last short circuit was released It is determined that magnetic blowing has occurred, and the base current is rapidly increased to 200 A or more. When the welding voltage decreases during this magnetic blowing period, it is determined that the magnetic blowing has been canceled and the base current is set to a normal value. A control method for dealing with magnetic blow of consumable electrode pulse arc welding, characterized in that arc breakage due to the magnetic blow is suppressed. 2. The control method for dealing with magnetic blow of consumable electrode pulse arc welding according to claim 1, wherein when the welding voltage is reduced by a predetermined reference decrease value from the maximum value during the magnetic blow period, it is determined that the magnetic blow is eliminated. .

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