JPH08267238A - Method for controlling output of power source for consumable electrode gas shielded pulsed arc welding - Google Patents

Abstract

PURPOSE: To improve the deposition efficiency by setting the prescribed peak voltage having the prescribed voltage gradient in the peak period of the constant voltage characteristic thereby reducing generation of the spatter. CONSTITUTION: In the peak period to feed the peak current of the constant voltage characteristic, the peak voltage having the prescribed voltage gradient dV/dt in the range of -0.7 to 0V/ms is set as the voltage to be applied between the welding wire and the base metal. That means, the peak voltage where the voltage value is the prescribed constant value, or the peak voltage where the voltage value is gradually reduced with lapse of time. Generation of the spatter due to the contact short circuit of the droplet at the wire tip with the molten pool is reduced to achieve the stable CO2 gas pulsed arc welding where the arc break is extremely rare in the first layer welding of the butt joint.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention alternately and repeatedly supplies a peak current and a base current between a welding wire (consumable electrode) and a base metal, and a carbon dioxide gas or a mixed gas containing carbon dioxide as a main component is used as a shield gas. The present invention relates to an output control method of a power supply for consumable electrode type gas shield pulse arc welding which generates an arc used as.

[0002]

2. Description of the Related Art As is well known, consumable electrode type gas shielded arc welding using a carbon dioxide gas alone or a mixed gas containing carbon dioxide as a main component as a shield gas and a solid wire as a welding wire is the most popular type. Although it is an efficient welding method, it has a drawback that a large amount of spatter is generated. For this reason, in order to reduce the generation of spatter, a mixed gas containing argon gas, which is an inert gas, as a main component is used as a shield gas, and a peak current and a base current are alternately and repeatedly energized between the welding wire and the base metal. So-called mag pulse arc welding has been proposed. Mag-pulse arc welding forms droplets on the tip of the welding wire during the peak period when the peak current is applied, separates the droplets during the base period when the base current is applied and transfers them to the base metal, and spatters. This is to prevent a contact short circuit between the droplet at the tip of the wire and the molten pool, which is one of the causes of occurrence.

However, in the mag pulse arc welding accompanied by such a droplet transfer phenomenon, spatter generation can be extremely reduced depending on the welding conditions, but the cost of argon gas is very high compared to carbon dioxide gas, so that it is limited. The fact is that they are being adopted in the selected fields.

Therefore, as disclosed in JP-B-2-31630, a consumable electrode type gas shield pulse arc welding method using carbon dioxide gas or a mixed gas containing carbon dioxide gas as a main component as a shield gas (hereinafter, A carbon dioxide gas pulse arc welding method) has been proposed.

In this conventional carbon dioxide gas pulse arc welding method, as shown in FIG. 11, between the welding wire W and the base metal, a constant current characteristic has a constant peak current and a constant current characteristic has a constant base current. To generate an arc by repeatedly energizing them and to release the droplet at the tip of the welding wire by pinch force at the beginning of the peak period (peak section) in which the peak current flows, and then melt the droplet at the tip of the welding wire. Is formed, and the droplets at the tip of the welding wire are shaped during the base period (base section) in which the base current flows. In addition, a larger peak current is applied at the initial stage of the peak current, a period for growing the droplet at the tip of the welding wire by the peak current after the droplet detachment is provided, and the peak current is gradually reduced after the droplet detachment. It is characterized in that the droplets grow and are shaped at the tip of the welding wire.

[0006]

However, in the conventional carbon dioxide gas pulse arc welding method described above, although the generation of spatter due to the contact short circuit between the wire tip droplet and the molten pool can be reduced, the peak of constant value of the constant current characteristic is reduced. Since a current is passed to separate and form droplets, the current value for droplet separation is prioritized, and the current value at the moment of droplet separation and the time of droplet formation Because the current value of is too large, spatter is caused by the blowout of the constricted portion of the droplet at the time of droplet separation, spatter by droplet blowout at the time of droplet formation at the welding wire tip after droplet separation, and vibration of the molten pool. There was a problem that a lot of spatter was generated from the molten pool. Hereinafter, this problem will be described.

In the above-mentioned conventional carbon dioxide pulse arc welding method, a constant current has a constant peak current, and the current value is such that the droplet formed at the tip of the welding wire has an electromagnetic pinch force. It is considered as a value that can be released by. Then, when the droplets at the tip of the welding wire are to be released at the beginning of the peak period in which the peak current is flown, it is better that the pinch force for removing the droplets is large, but if the peak current is too large, the results in FIG. As shown in the drawing, when the droplet is separated, the constricted portion K formed when the droplet D is about to separate from the tip of the welding wire W is blown off due to the strong arc force, so that the spatter S is frequently generated.

If the peak current is too large, a sufficient peak current is supplied to separate the droplet even if the droplet is formed at the tip of the welding wire after the droplet is separated. As described above, the droplets formed at the tip of the welding wire W are blown off due to the strong arc force, so that large spatters S are generated. In particular, when an arc is generated by obliquely deflecting from the tip of the welding wire toward the groove wall, it is easily blown off by the arc force and blows off the droplets formed at the tip of the welding wire after the droplets have separated. The frequency of occurrence of spatter due to the remarkably increases.

Therefore, if the peak current of the constant current characteristic is reduced in order to reduce the spatter generated by the above-mentioned generation mechanism, it is necessary to significantly lengthen the peak time for separating and forming the droplets, and the pulse frequency Extremely deteriorates, and welding workability becomes extremely poor. The pulse frequency f is represented by f = 1 / (tp + tb) where tp is the peak time and tb is the base time.

In the conventional carbon dioxide gas pulse arc welding method, the difference between the peak current and the base current is large,
In addition, since it changes abruptly, magnetic blow is likely to occur particularly during initial layer welding of the butt joint, and arc breakage is likely to occur during the base period when the welding voltage is set lower than that during the peak period. Further, since the difference between the peak current and the base current is large, the molten pool vibrates violently due to the arc force, which causes the molten metal to scatter from the molten pool, resulting in more spatter.

In the conventional carbon dioxide gas pulse arc welding method, there has been proposed a technique in which a peak current larger than the normal peak current is caused to flow in order to promote the detachment of droplets. Also in this case, as described above, the current value at the time of detachment of the droplets is too large, and the constricted portion of the droplets is blown off, causing spatter.

In the conventional carbon dioxide gas pulse arc welding method, an example is shown in which the current after the droplet is released is gradually reduced. However, as in the embodiment, the timing for releasing the droplet is set. Since it is after a predetermined period of time after the start of supplying the peak current, spatter occurs due to the following situations. That is, when the timing of droplet detachment comes before the peak current decreases, the current value after droplet detachment is high, so that the droplets that have begun to be formed at the tip of the wire are blown off by the strong arc force, Spatter occurs. On the other hand, if the timing of droplet detachment comes after the peak current starts to decrease gradually, the droplet detachment often becomes impossible, and one pulse / droplet transfer for detaching one droplet per pulse cycle. The droplet transfer phenomenon becomes unstable and the contact short circuit with the molten pool occurs, and large-sized spatters are generated.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems and to reduce the generation of spatter due to the contact short-circuit between the droplet at the tip of the wire and the molten pool during carbon dioxide pulse arc welding. Spatter due to blowout of the constricted portion of the droplet during drop off, spatter due to blow off of droplet during drop formation at the welding wire tip after drop off, and spatter from the molten pool due to vibration of the weld pool To provide an output control method for a power supply for consumable electrode type gas shield pulse arc welding, which can reduce the occurrence of arcing at the time of the first layer welding of a butt joint, and can also reduce the occurrence of arcing. is there.

[0014]

According to the first aspect of the present invention,
Consumable electrode type gas shield pulse arc welding in which peak current and base current are alternately and repeatedly supplied between the welding wire and the base material to generate an arc using carbon dioxide gas or a mixed gas containing carbon dioxide gas as a main component as a shield gas. In the output control method of the power supply for use, an external output characteristic switching control is performed in which the peak period for supplying the peak current has a constant voltage characteristic and the base period for supplying the base current has a constant current characteristic, and the constant voltage characteristic In the peak period, the voltage slope is set in the range of -0.7 to 0V / ms.
It is characterized by setting a set peak voltage having dV / dt.

According to a second aspect of the present invention, in the output control method of the power supply for consumable electrode type gas shield pulse arc welding according to the first aspect, the value of the voltage gradient dV / dt is a function of the wire feeding speed W _FR . Is defined by dV / dt = a × W _FR −b (where constants a and b ≧ 0).

According to a third aspect of the present invention, in the output control method of the power supply for consumable electrode type gas shield pulse arc welding according to the first or second aspect, the response speed of the peak current of the constant voltage characteristic is 500 to 4000A. The output is controlled in the range of / ms.

[0017]

In the output control method of the power supply for consumable electrode type gas shield pulse arc welding according to the present invention, the base period is supplied by supplying the base current by supplying the base current with the constant voltage characteristic during the peak period for supplying and supplying the peak current. During the period (base section), the external output characteristic switching control with the constant current characteristic is performed. First, this will be explained. In carbon dioxide pulse arc welding in which droplets are separated and formed thereafter during the peak period, MIG welding or Ar arc welding is performed.
Since a droplet much larger than that in gas-rich MAG welding separates and transfers, the arc length becomes long immediately after the droplet separates, depending on the droplet diameter. For this reason, if the external output characteristic during the peak period when the peak current is output is set to a constant voltage characteristic, the arc length (arc voltage) is kept approximately constant by the self-control action of the arc by the welding power source having the constant voltage characteristic. The welding current (peak current) decreases immediately after the droplets have separated (see FIG. 8). The welding current drops sharply at the moment of droplet separation, and flows after the droplet separation according to the arc length at that time.

As a result, it is possible to weaken the arc force after the droplets are released, and to reduce the generation of spatter due to the droplets being blown off when forming the droplets at the tip of the welding wire after the droplets are released. Since the current difference when shifting to the base current is also suppressed to a small level, the occurrence of arc breakage during the first layer welding of the butt joint can be extremely reduced, and the vibration of the molten pool is suppressed to prevent spatter from the molten pool. Occurrence can be reduced. Furthermore, when the droplets are separated, the time from the start of the constriction of the droplets to the separation of the droplets is very short, and when the constrictions start, the electrical resistance of that part rapidly increases and the current drops sharply. For,
It is possible to reduce the generation of spatter due to the blowout of the constricted portion of the droplet when the droplet is released. In the base period, a base current having a constant current characteristic is output in order to make the droplet diameter uniform.

In the output control method according to the present invention,
During the peak period of supplying the peak current of the constant voltage characteristic, the voltage applied between the welding wire and the base metal is -0.7 to 0.
A set peak voltage having a voltage gradient dV / dt defined in the range of V / ms, that is, a set peak voltage whose voltage value is a predetermined constant value, or a setting such that the voltage value gradually decreases with time. It is necessary to set the peak voltage. Hereinafter, this will be described.

When the peak period is made to have a constant voltage characteristic, as described above, after the droplets have separated, the peak current supplied to the welding wire is reduced by the self-control action of the arc by the welding power source, and FIG. As shown on the right side of, the first peak current (I _P1 ) having a current value at which the droplet can be separated and the second peak current (I _P2 ) having a current level lower than the current value can be separated in the same peak period. Will be supplied.
Regarding the second peak current that is made to flow after this droplet detachment,
In the peak time range where the pulse frequency that does not impair the welding workability can be maintained, the output must be controlled so that the droplet cannot be separated and the minimum current value required for droplet formation can be obtained. Is good.

The current value (average value) of the second peak current is set as a voltage applied between the welding wire and the base metal during the peak period having the constant voltage characteristic. It can be controlled by the value of dt. FIG. 10 is a diagram showing an example of arc voltage (welding voltage) / welding current waveform when the value (negative value) of the voltage slope dV / dt of the set peak voltage in the peak period in the constant voltage characteristic is changed. Is. In FIG. 10, reference symbol PT indicates a peak period, and BT indicates a base period.

FIG. 14 is a diagram showing the relationship between the peak current and the peak time (peak current conduction time) for releasing the droplet from the wire tip. In carbon dioxide pulse arc welding using a welding power source having a constant current characteristic, one pulse / one droplet transfer condition was obtained when the peak current and the peak time were changed. For a solid wire with a welding wire diameter of 1.2 mm, the appropriate peak current range is 40
It was 0 to 550 A, and the peak time at the pulse frequency that did not impair the welding workability was about 15 ms or less. From these, it can be seen that the current value of the second peak current may be set to about 400 A or less so that the droplet cannot be separated.

FIG. 9 is a diagram showing the relationship between the voltage gradient dV / dt and the second peak current value (average value). The average value of the second peak current when the voltage gradient dV / dt is changed so that the first peak current is about 500 A is investigated. As can be seen from the figure, the upper limit of the voltage gradient dV / dt is preferably 0 (zero) V / ms at which the second peak current becomes about 400 A at which the above-mentioned droplet cannot be separated. If the value is larger than this value, the arcing force is strong because the current drop after the droplet is separated is small, and spatter occurs due to the droplet being blown off when the droplet is formed. The lower limit of the voltage gradient dV / dt is −0.7 V / m, which is the minimum current value of about 200 A required for droplet formation.
s is good. Less than this value (the slope of the fall is large)
As a result, the current drops too much after the droplet has been separated, so that the droplet cannot be formed and the arc becomes unstable, so that spatter occurs.

In the output control method according to the present invention,
The value of the voltage gradient dV / dt is the wire feeding speed W _FR (m /
min) and dV / dt = a × W _FR −b (where
It is preferable that it is determined by the constants a and b ≧ 0). This will be described below.

In the welding power source, the pulse waveform control for the wire feed amount is generally performed by changing the base time. Therefore, low feed side (low current side)
The pulse frequency becomes higher as it shifts from the high feed side to the high feed side. On the low feed side, the pulse frequency is prevented from becoming too low from the viewpoint of welding workability, and the base time is long, and droplets at the tip of the welding wire can grow to some extent during this base time. Therefore, the value of the voltage slope dV / dt may be small (the slope is large) because the current value after the droplets have separated during the peak period may be low. When the value of the voltage gradient dV / dt is reduced, the current value after the droplet breaks off of the peak current becomes lower, so that the amount of wire fed at a certain constant rate per pulse However, the energy for forming droplets is reduced, but the shortage of the energy can be compensated by controlling the pulse frequency to be increased.

On the other hand, on the high feed side, the pulse frequency is prevented from becoming too high, the base time is short, and the droplets at the tip of the welding wire are hardly grown during this base time, so during the peak period. Since it is necessary to actively form droplets after the droplets have separated, the voltage gradient dV / dt
The value of should be large. Therefore, the voltage gradient dV / dt can be set as a function of the wire feeding speed W _FR so that the gradient becomes smaller as the wire feeding speed W _FR increases. The constants a and b are determined by the material of the welding wire, the wire diameter, the shield gas composition, and the like.

In the output control method according to the present invention,
The response speed of the peak current of the constant voltage characteristic is 500 to 4
The output may be controlled in the range of 000 A / ms. If the response speed of the peak current is less than 500 A / ms, a steep current drop (see FIG. 8) at the time of constriction of the droplet (immediately before the detachment of the droplet) cannot be sufficiently obtained, and spatter due to blow-off of the constricted portion of the droplet may occur. It tends to occur. Response speed is 4000A
This is because if the value exceeds / ms, an excessive current decrease is caused and an arc breakage is likely to occur when the droplet is constricted or when the peak current is switched to the base current.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of a consumable electrode type gas shield pulse arc welding power source for carrying out the method according to the present invention.

In FIG. 1, reference numeral 1 is a three-phase AC power supply unit. The alternating current supplied from the three-phase alternating-current power supply unit 1 is rectified into direct current by the first rectifier circuit 2 and smoothed by the smoothing capacitor 3. This DC current is the inverter 4
Is converted into high frequency alternating current by. The transformer 5 steps down the output of the inverter 4 to a welding voltage. Transformer 5
The high-frequency alternating current that has been stepped down for welding is rectified by the second rectifier circuit 6 into welding direct current. This DC current is passed through the smoothing reactor 7 and the welding wire 8 and the base metal 9
It is supplied between the two and arc welding is performed.

Reference numeral 10 is a welding voltage detector for detecting the arc voltage, and 11 is a current detector for detecting the welding current. The output of the welding voltage detector 10 is the control unit 3 described later.
Given to 0. The welding wire 8 is a wire feed motor 18
Is fed toward the base material 9 by the wire feeding roller 19 driven by, and welding is performed by generating an arc between the welding wire 8 and the base material 9. Wire feeding motor control circuit 20
Is for controlling the rotation speed of the feed motor 18 based on the feed speed setting signal from the wire feed speed setting device 24.

The control unit 30 controls the inverter 4 to
To form a pulse waveform consisting of a peak period for supplying the peak current and a base period for supplying the base current, and to perform external output characteristic switching control, etc., where the peak period has a constant voltage characteristic and the base period has a constant current characteristic. belongs to.

An appropriate base current is set in the base current setting circuit 13 of the control unit 30 to maintain an arc, and the base period setting circuit 15 is set in the wire feed speed setting device 24 and the welding voltage detector 10. The base time tb is set so that a predetermined pulse frequency f corresponding to the wire feeding speed and the arc voltage is obtained by inputting the signal from the. Further, the peak period setting circuit 14 is set with an appropriate peak time tp. Then, these setting circuits and the peak voltage setting circuit 12 described later output each set value (signal) to the pulse waveform selection circuit 16 as a pulse parameter setting signal. The pulse waveform selection circuit 16 supplies an inverter control signal based on each pulse parameter setting signal to the power control circuit 17, and the power control circuit 17 controls the inverter 4.

Reference numeral 21 denotes a triangular wave generating circuit, which is a circuit for generating a triangular wave signal whose output value linearly decreases with time at a set inclination. Reference numeral 22 is an amplifier circuit which is composed of an operational amplifier, a resistor and the like, and which amplifies the output signal of the triangular wave generation circuit 21. The triangular wave generating circuit 21 and the amplifying circuit 22 set a set peak voltage having a predetermined voltage slope dV / dt during a peak period having a constant voltage characteristic. Peak voltage setting circuit 12
Is a signal for inputting the signal from the amplifier circuit 22 and the detection signal from the welding voltage detector 10 so that the arc voltage becomes the set peak voltage during the peak period of the constant voltage characteristic. It is output to the pulse waveform selection circuit 16.

The feeding speed setting signal from the wire feeding speed setting device 24 is input to the triangular wave generating circuit 21, and a triangular wave signal having an inclination according to the wire feeding speed setting signal is generated. As a result, the voltage gradient dV / dt of the set peak voltage can be automatically set as a function of the wire feeding speed W _FR . In addition, when the automatic setting is not performed, the variable resistor 23 of the amplifier circuit 22 is
The predetermined voltage slope dV / dt can be set by adjusting and changing the amplification factor.

Hereinafter, carbon dioxide gas was used as a shield gas, and carbon dioxide pulse arc welding was performed by the welding power source having the above-mentioned configuration. First, the amount of spatter generated was measured and investigated. FIG. 2 is a perspective view for explaining a method for collecting spatter. As shown in the same figure, a long test plate M having a width of 25 mm is placed horizontally, and the test plate M is sandwiched from both sides, and a sputter trap having a substantially U-shaped cross section is taken along the test plate longitudinal direction (welding direction). The collecting plate P was set. T indicates a welding torch. Then, the test plate M was welded with a bead-on-plate under the welding conditions described later, and the spatter generated at that time was collected and weighed to obtain and evaluate the spatter generation amount per minute.

First, carbon dioxide gas pulse arc welding was carried out using the method of the present invention while varying the wire feed rate over a wide range, and the amount of spatter generated at that time was measured. Welding conditions are welding wire: YGW-11, wire diameter: 1.2 m.
m, wire feeding speed: 8 to 16 m / min, wire protruding length: 20 mm, welding speed: 40 cm / min. The value of the voltage slope dV / dt of the set peak voltage at each wire feeding speed was determined with reference to FIG. 7 described later. For comparison, conventional carbon dioxide gas pulse arc welding with a welding power source whose peak period and base period are constant current characteristics, normal carbon dioxide gas arc welding without a pulse with an inverter-controlled welding power source, and thyristor control Performs normal carbon dioxide arc welding with a power source for type welding,
Each spatter generation amount was measured.

The results are shown in FIG. As can be seen from the figure, according to the carbon dioxide gas pulse arc welding using the method of the present invention, in addition to the reduction of spatter caused by the contact short circuit between the wire tip droplet and the molten pool, the droplet at the time of droplet separation It also reduces the occurrence of spatter due to blow-out of the necked portion, the occurrence of spatter due to droplet blow-off when forming droplets at the welding wire tip after droplet detachment, and the occurrence of spatter from the molten pool due to vibration of the molten pool. Over a wide range of welding conditions with a wide range of wire feed rates,
Compared with the conventional carbon dioxide pulse arc welding method, it was possible to reduce the generation of spatter. In particular, the generation of spatter in the low wire feeding speed range, which was difficult with the conventional carbon dioxide pulse arc welding method, could be reduced to almost half.

Next, carbon dioxide pulse arc welding using the method of the present invention was performed by changing the voltage gradient dV / dt of the set peak voltage at a standard wire feeding speed, and the amount of spatter generated at that time was measured. . Welding conditions are: welding wire: YGW-11, wire diameter: 1.2 mm, wire feeding speed: 12 m / min, wire protrusion length: 20 m.
m, welding speed: 40 cm / min.

The results are shown in FIG. At a standard wire feed rate with a wire diameter of 1.2 mm, if the voltage gradient dV / dt is in the range of -0.7 to 0 V / ms, the occurrence of spatter can be reduced compared to the conventional case. From FIG. 4, it can be seen that the optimum voltage gradient dV / dt in this case is approximately −0.2 V / ms.

Next, carbon dioxide gas pulse arc welding was carried out using the method of the present invention while changing the response speed of the peak current of the constant voltage characteristic, and the amount of spatter generated at that time was measured.
The welding conditions are welding wire: YGW-11, wire diameter:
1.2 mm, wire feeding speed: 12 m / min, voltage gradient dV / dt: -0.19 V / ms, wire protrusion length: 2
0 mm, welding speed: 40 cm / min.

The results are shown in FIG. When the response speed of the peak current is less than 500 A / ms, a steep drop in current at the time of constriction of the droplet was not sufficiently obtained, and spatter occurred due to blow-off of the constricted portion of the droplet. Also, the response speed is 4000
When it exceeds A / ms, the current is excessively decreased when the droplet is constricted or when the peak current is switched to the base current, and the arc breaks.

Next, the arc breakage during the first layer welding of the butt joint was investigated. The arc breakage is likely to occur mainly in the first layer welding of the butt joint as described above, and occurs when the peak current shifts to the base current. Increasing the base current value is the most effective measure against arc breakage, but on the other hand, spatter increases. Therefore, it is necessary to suppress the base current value as much as possible to reduce the sputtering. The lowest base current value that does not cause arc breakage was set as the limit base current, and carbon dioxide gas pulse arc welding using the method of the present invention and conventional carbon dioxide gas pulse arc welding as a comparative example were performed, and the limit base currents were compared. .

The welding conditions are welding wire: YGW-11,
Wire diameter: 1.2 mm, wire feeding speed: 12 m / m
in, average peak current: 500 A, wire protrusion length: 25 mm. In the carbon dioxide gas pulse arc welding using the method of the present invention, the voltage gradient dV / dt is -0.
It was set to 19 V / ms. The number of arc breaks at a welding length of 30 cm was examined.

The results are shown in FIG. In the carbon dioxide gas pulse arc welding using the method of the present invention, compared to the conventional carbon dioxide gas pulse arc welding, the V-shaped butt groove (no gap,
It can be seen that the limiting base current is low and welding with less spatter is possible in both cases of backing) and Y-shaped butt groove.

FIG. 7 shows YGW-11, wire diameter 1.2 m.
It is a figure which shows the relationship between a wire feed speed and voltage gradient dV / dt when the welding wire of m is used. As shown in FIG. 7, the voltage gradient dV / dt (V / ms) is the wire feed speed W.
It can be expressed as a linear function of _FR (m / min), and in this example, can be expressed by dV / dt = 0.016 × W _FR −0.38.

[0046]

As described above, according to the output control method of the power supply for consumable electrode type gas shield pulse arc welding according to the present invention, the peak period for supplying the peak current has a constant voltage characteristic and the base for supplying the base current. During the period, the external output characteristic switching control with constant current characteristic is performed, and during the peak period with constant voltage characteristic, a set peak voltage having a voltage gradient of a predetermined value is set. When performing pulse arc welding, in addition to reducing the generation of spatter due to contact short-circuit between the droplet at the tip of the wire and the molten pool, the generation of spatter due to the blowout of the constricted portion of the droplet at the time of droplet detachment, and welding after droplet detachment Occurrence of spatter due to droplet blow-off when forming droplets at the wire tip,
Also, it is possible to reduce the generation of spatter from the molten pool due to vibration of the molten pool, which can improve the welding efficiency, and the labor for removing the spatter adhering to the base material and the welding torch nozzle can be reduced. In addition, stable carbon dioxide pulse arc welding with very few arc breaks can be performed in the first layer welding of a butt joint.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a consumable electrode type gas shield pulse arc welding power source for carrying out the method according to the present invention.

FIG. 2 is a perspective view for explaining a method for collecting spatter.

FIG. 3 is a diagram according to the present invention and is a diagram showing a relationship between a wire feeding speed and a spatter generation amount.

FIG. 4 is a diagram according to the present invention, showing the relationship between the voltage gradient dV / dt and the amount of spatter generated.

FIG. 5 is a diagram according to the present invention, showing the relationship between the peak current response speed and the amount of spatter generated.

FIG. 6 is a diagram according to the present invention, showing a relationship between a base current and the number of arc breaks.

FIG. 7 is a diagram according to the present invention and is a diagram showing a relationship between a wire feeding speed and a voltage gradient dV / dt in the case of using a YGW-11 and a welding wire having a wire diameter of 1.2 mm.

FIG. 8 is a diagram according to the present invention, showing a current change and a droplet transfer form in carbon dioxide pulse arc welding.

FIG. 9 is a diagram according to the present invention, showing a relationship between a voltage gradient dV / dt and a second peak current value (average value).

FIG. 10 is a diagram according to the present invention, showing a voltage gradient dV / dt
It is a figure which shows an example of an arc voltage / welding current waveform when changing the value (negative value) of.

FIG. 11 is a diagram showing a welding current waveform and a state of droplet transfer in conventional carbon dioxide gas pulse arc welding.

FIG. 12 is a diagram showing how the constricted portion is blown off and spatter is generated.

FIG. 13 is a diagram showing how droplets formed at the tip of the welding wire are blown off and spatter is generated.

FIG. 14 is a diagram showing a relationship between a peak current and a peak period for releasing a droplet from a tip of a wire.

[Explanation of symbols]

1 ... 3-phase AC power supply part 2 ... 1st rectification circuit 3 ... Smoothing capacitor 4 ... Inverter 5 ... Transformer 6 ... 2nd rectification circuit 7 ... Reactor 8 ... Welding wire 9 ... Base metal 10 ... Welding voltage detector 11 ... Current detector 12 ... Peak voltage setting circuit 13 ... Base current setting circuit 14 ...
Peak period setting circuit 15 ... Base period setting circuit 16
... Pulse waveform selection circuit 17 ... Power control circuit 18 ... Wire feeding motor 21 ... Triangular wave generation circuit 22 ... Amplifying circuit 24 ... Wire feeding speed setting device 30 ... Control unit W ...
Welding wire D ... Droplet K ... Constricted portion S ... Sputter M ... Test plate P ... Sputter collection plate T ... Welding torch

Claims (3)

[Claims] 1. A consumable electrode type for generating an arc by alternately supplying a peak current and a base current between a welding wire and a base metal and using carbon dioxide or a mixed gas containing carbon dioxide as a main component as a shield gas. In the output control method of the power supply for gas shield pulse arc welding, the peak period for supplying the peak current has a constant voltage characteristic, and the base period for supplying the base current performs an external output characteristic switching control with a constant current characteristic, In the peak period having the constant voltage characteristic, a set peak voltage having a voltage gradient dV / dt defined in the range of -0.7 to 0 V / ms is set, and the consumable electrode type gas shield pulse arc welding is characterized. Output control method for power supply. 2. The consumable electrode type gas shield pulse arc welding according to claim 1, wherein the value of the voltage gradient dV / dt is determined by the following equation as a function of the wire feeding speed W _FR. Output control method for power supply. dV / dt = a × W _FR −b where constants a and b ≧ 0 3. The consumable electrode type gas shield pulse arc welding according to claim 1, wherein the peak current of the constant voltage characteristic is output controlled in a response speed range of 500 to 4000 A / ms. Output control method for power supply.