JP2007144509A - Method of controlling arc start for two-electrode arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an arc start being free from spatters without applying high-frequency high voltage discharge in two-electrode arc welding, in which a consumable electrode arc and a non-consumable electrode arc are generated with a consumable electrode 1a and a non-consumable electrode 1b provided in one shielding gas nozzle 5 on the tip of a welding torch. <P>SOLUTION: In a method for controlling the arc start in two-electrode arc welding, the consumable electrode is fed forward to a base material, and when the consumable electrode touches the base material, it is fed backward. When the consumable electrode gets away from the base material, an initial arc with a small current value is generated. While the initial arc is retained, the backward feeding of the consumable electrode is continued during a prescribed period Td so that the arc length is increased. The period Td has passed over, the consumable electrode is again fed forward at a normal feeding speed and arcing is shifted to a normal arc with a large current value. The normal arc makes the space between the non-consumable electrode and the base material full of a plasma atmosphere so as to generate the non-consumable electrode arc. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides a consumable electrode and a non-consumable electrode in one shield gas nozzle at the tip of a welding torch to improve arc start performance in two-electrode arc welding in which a consumable electrode arc and a non-consumable electrode arc are generated and welded. The present invention relates to an arc start control method for two-electrode arc welding.

[Prior art 1]
FIG. 7 is a configuration diagram of a welding apparatus for two-electrode arc welding in which a consumable electrode and a non-consumable electrode are provided in one shield gas nozzle at the tip of the welding torch to generate a consumable electrode arc and a non-consumable electrode arc. A consumable electrode (welding wire) 1a and a non-consumable electrode (tungsten electrode or the like) 1b are insulated from each other in one shield gas nozzle 5 attached to the tip of the welding torch. A consumable electrode arc 3a such as MIG welding is generated between the consumable electrode 1a and the base material 2, and a non-consumable electrode arc 3b such as TIG welding is generated between the non-consumable electrode 1b and the base material 2. Welding is performed.

  The voltage setting circuit VR outputs a predetermined voltage setting signal Vr. The consumable electrode arc welding power source PSM performs constant voltage control based on the voltage setting signal Vr, outputs the consumable electrode arc welding voltage Vwa between the power feed tip 4a and the base material 2, and the consumable electrode arc welding current Iwa is energized. At the same time, a feed control signal Fc for controlling the rotation of the wire feed motor M is output. The consumable electrode 1a is fed at a predetermined feeding speed Fw by the rotation of the feeding roll 6 coupled to the wire feeding motor M, and is fed from the feeding chip 4a. In the above consumable electrode arc welding voltage Vwa, the consumable electrode 1a has a positive polarity EP.

  The non-consumable electrode arc welding power source PST applies a non-consumable electrode arc welding voltage Vwb between the collet 4b and the base material 2 and energizes the non-consumable electrode arc welding current Iwb. The non-consumable electrode 1b is supplied with power from the collet 4b. In the non-consumable electrode arc welding voltage Vwb, the non-consumable electrode 1b has a negative polarity EN.

  The welding start circuit ST outputs a welding start signal St that changes to a high level when welding is started. The consumable electrode arc welding power source PSM and the non-consumable electrode arc welding power source PST start outputting with the welding start signal St as an input. Although the figure shows a case where two welding power sources are used, it can also be performed using only one welding power source. In this case, an AC voltage is output from the welding power source, applied to the consumable electrode 1a when the AC voltage is a positive output, and applied to the non-consumable electrode 1b when the AC voltage is a negative output. (See Patent Documents 1 to 3 for the above-described prior art 1)

[Prior Art 2]
FIG. 8 is a configuration diagram of a welding apparatus for performing plasma MIG welding in which a non-consumable electrode for plasma arc welding is hollow and a consumable electrode arc and a non-consumable electrode arc are generated through the consumable electrode. Similar to a general plasma arc welding torch, a non-consumable electrode (tungsten electrode) 1 b is provided in the plasma nozzle 7, and a plasma arc (non-consumable electrode arc) 3 b is generated between the base material 2. A shield gas nozzle 5 is provided outside the plasma nozzle 7. The non-consumable electrode 1b is hollow in the axial direction, and a consumable electrode (welding wire) 1a is insulated and fed through the hollow, and a consumable electrode arc 3a is generated between the base material 2 and the non-consumable electrode 1b. .

  The voltage setting circuit VR outputs a predetermined voltage setting signal Vr. The consumable electrode arc welding power source PSM performs constant voltage control based on the voltage setting signal Vr, applies the consumable electrode arc welding voltage Vwa between the consumable electrode 1a and the base material 2, and the consumable electrode arc welding current Iwa is energized. At the same time, a feed control signal Fc for controlling the rotation of the wire feed motor M is output. The consumable electrode 1a is fed at a predetermined feeding speed Fw by the rotation of the feeding roll 6 coupled to the wire feeding motor M. In the above consumable electrode arc welding voltage Vwa, the consumable electrode 1a has a positive polarity EP.

  The plasma arc (non-consumable electrode arc) welding power source PSP applies a plasma arc (non-consumable electrode arc) welding voltage Vwb between the collet 4b and the base material 2, and a plasma arc (non-consumable electrode arc) welding current Iwb is energized. To do. The non-consumable electrode 1b is supplied with power from the collet 4b. In the plasma arc (non-consumable electrode arc) welding voltage Vwb, the non-consumable electrode 1b has a negative polarity EN.

  The welding start circuit ST outputs a welding start signal St that changes to a high level when welding is started. The consumable electrode arc welding power source PSM and the plasma arc (non-consumable electrode arc) welding power source PSP start output with the welding start signal St as an input. (Refer to Patent Document 4 for the above-described prior art 2)

JP 63-101082 A JP 57-22877 A JP-A-56-105870 JP 63-168283 A

  FIG. 9 is a timing chart at the time of arc start in the two-electrode arc welding of the prior arts 1 and 2 described above. FIG. 4A shows the welding start signal St, FIG. 4B shows the consumable electrode feed speed Fw, FIG. 3C shows the consumable electrode arc welding voltage Vwa, and FIG. 4D shows the consumable electrode arc. (E) of welding current Iwa shows time change of non-consumable electrode arc welding voltage Vwb, (F) shows time change of non-consumable electrode arc welding current Iwb, and (G1) to (G3) of FIG. It is a schematic diagram of a generation | occurrence | production part. Hereinafter, a description will be given with reference to FIG.

  At time t1, as shown in FIG. 6A, when the welding start signal St becomes High level, the consumable electrode 1a is fed at a very slow slow-down speed as shown in FIG. At the same time, no-load voltage is applied as shown in FIG. At the same time, as shown in FIG. 5E, a high-frequency discharge high voltage is applied to apply an unloaded voltage between the non-consumable electrode 1b and the base material 2 and to generate an arc between the non-consumable electrode and the base material. (Several MHz several kV) is applied.

  At time t2, when the consumable electrode 1a contacts the base material 2 by slow-down feeding, the consumable electrode arc welding voltage Vwa changes to a short-circuit voltage value of several V as shown in FIG. As shown in D), the consumable electrode arc welding current Iwa is energized. In response to this, the feeding speed Fw increases to the steady feeding speed as shown in FIG. At the time t3, the consumable electrode 1a is heated by the Joule heat generated by energization during the short-circuit period from the time t2 to the time t3, is bent and melted, and an arc is generated while a large amount of spatter 8 is scattered. When the arc is generated, as shown in FIG. 5C, the arc voltage is increased from the short-circuit voltage to the arc voltage controlled at the constant voltage to the value of the voltage setting signal Vr. Thereafter, at time t4, as shown in FIG. 4G2, a non-consumable electrode arc is generated by the application of the high-frequency discharge high voltage, and as shown in FIG. When energized, the voltage drops from the no-load voltage to the arc voltage as shown in FIG. At the time t4, the arc length of the consumable electrode arc is still short, and is a transient state in which the generation of the sputter 8 continues. When a little time elapses from time t4, the arc length of the consumable electrode arc becomes longer and becomes a stable steady state as shown in FIG.

  The arc start of the above-described two-electrode arc welding has the following two problems. The first problem is that a high frequency discharge high voltage is used to generate a non-consumable electrode arc. When this high frequency discharge high voltage is applied, a very strong electromagnetic noise is generated. For this reason, it is necessary to take strict noise countermeasures for electronic devices such as a welding power source, a welding robot, a workpiece transfer device, and various sensors. As a result, there is a problem that it takes time to construct the equipment and the cost is high. There is also a method of applying a pulsed DC high voltage (several kV) instead of applying this high frequency discharge high voltage, but there is a problem that the arc start property is deteriorated depending on welding conditions.

  The second problem is that welding quality deteriorates because a large amount of spatter is scattered when a consumable electrode arc is generated. This is an unavoidable problem in principle because the consumable electrode is short-circuited with the base material, a large current is applied, and the arc is started by fusing with Joule heat. Furthermore, if the consumable electrode arc is generated before the non-consumable electrode arc, the non-consumable electrode is contaminated by the occurrence of the above-described sputtering, and the arc start property and welding quality of the non-consumable electrode may be deteriorated.

  Therefore, the present invention provides an arc start control method for two-electrode arc welding that can solve the above-described problems.

In order to solve the above-mentioned problems, the first invention is a two-electrode arc in which a consumable electrode and a non-consumable electrode are provided in one shield gas nozzle at the tip of a welding torch and a consumable electrode arc and a non-consumable electrode arc are generated and welded. In the welding arc start control method,
When starting welding, a voltage is applied between the consumable electrode and the base material, and between the non-consumable electrode and the base material, the consumable electrode is fed forward to the base material, and when it comes into contact with the base material, it is fed back from the base material. When the consumable electrode is separated from the base material by feeding, an initial arc with a small current value is generated, and while maintaining the initial arc, the backward feeding is continued for a predetermined period to increase the arc length. The consumable electrode is re-advanced at a steady feeding speed and the welding voltage between the consumable electrode and the base metal is controlled at a constant voltage based on the steady voltage setting value to shift from the initial arc to a large current steady arc. Two electrodes characterized in that a plasma atmosphere is filled in a space between the non-consumable electrode and the base material by the consumable electrode arc to generate a non-consumable electrode arc, and the consumable electrode arc and the non-consumable electrode arc are started. Ah It is an arc start control method of welding.

  In a second aspect of the present invention, the consumable electrode is fed at an initial feeding speed that is slower than the steady feeding speed during an initial period from the re-forward feeding start time to the non-consumable electrode arc occurrence time. An arc start control method for two-electrode arc welding according to the first aspect of the invention.

According to a third aspect of the present invention, the non-consumable electrode has a hollow structure, the consumable electrode penetrates through the hollow, the consumable electrode arc is a MIG arc, and the non-consumable electrode arc is a plasma arc. Yes,
The consumable electrode is fed at an initial feeding speed that is faster than the steady feeding speed from the start of re-forward feeding, and the consumable electrode is fed at the steady feeding speed after a predetermined period of time has elapsed since the occurrence of the non-consumable electrode arc. An arc start control method for two-electrode arc welding according to the first aspect of the present invention.

According to a fourth aspect of the present invention, the non-consumable electrode has a hollow structure, the consumable electrode penetrates through the hollow, the consumable electrode arc is a MIG arc, and the non-consumable electrode arc is a plasma arc. Yes,
The welding voltage between the consumable electrode and the base material is controlled at a constant voltage based on an initial voltage setting value smaller than the steady voltage setting value from the re-forward feed start time, and after a predetermined period has elapsed since the non-consumable electrode arc has occurred. The arc start control method for two-electrode arc welding according to the first aspect of the invention, wherein the welding voltage between the consumable electrode and the base material is controlled at a constant voltage based on the steady voltage setting value.

  According to the first aspect of the invention, after the consumable electrode is once brought into contact with the base material and then pulled up by reverse feeding to generate an initial arc of a small current value, the arc is started by shifting to a steady arc. For this reason, since there is no fusing at the time of initial arc generation, sputtering hardly occurs. Furthermore, since the plasma atmosphere space is formed immediately below the non-consumable electrode by the consumable electrode arc, it is not applied by applying a normal no-load voltage (about 100 V) without applying a high-frequency discharge high voltage or a pulsed DC high voltage. A consumable electrode arc can be generated. For this reason, strong electromagnetic wave noise does not occur, and good arc start performance can always be obtained without deterioration of arc start performance due to welding conditions.

  According to the second aspect of the invention, in addition to the effect of the first aspect described above, an initial period is provided when the consumable electrode is fed forward again. During this period, the feeding speed is set higher than the steady feeding speed. By slowing down, the arc length can be further increased, and the plasma atmosphere space between the non-consumable electrode and the base material can be distributed to the vicinity of the tip of the non-consumable electrode. For this reason, the arc start property of the non-consumable electrode arc can be further improved.

  According to the third aspect of the present invention, the burnback due to the burning up of the consumable electrode at the time of the plasma arc is prevented by making the supply speed of the consumable electrode faster than the steady feed speed from the start of re-forward feeding. Can do. Furthermore, the burned arc length can be quickly converged to the steady arc length by making the feeding speed during a predetermined period after the plasma arc generation faster than the steady feeding speed. For this reason, in plasma MIG welding, in addition to the effects of the first invention, burnback of the consumable electrode can be prevented and good arc start performance can be obtained.

  According to the fourth aspect of the present invention, by setting the voltage setting value of the consumable electrode arc to be smaller than the steady-state value from the start of re-forward feeding, it is possible to prevent burnback due to the burning up of the consumable electrode when the plasma arc occurs. it can. Furthermore, the burned arc length can be quickly converged to the steady arc length by making the voltage setting value during the predetermined period after the plasma arc generation smaller than the steady value. For this reason, in plasma MIG welding, in addition to the effects of the first invention, burnback of the consumable electrode can be prevented and good arc start performance can be obtained.

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

[Embodiment 1]
FIG. 1 is a timing chart showing an arc start control method for two-electrode arc welding according to Embodiment 1 of the present invention. FIG. 4A shows the welding start signal St, FIG. 4B shows the consumable electrode feed speed Fw, FIG. 3C shows the consumable electrode arc welding voltage Vwa, and FIG. 4D shows the consumable electrode arc. (E) of the welding current Iwa is a time change of the non-consumable electrode arc welding voltage Vwb, (F) is a time change of the non-consumable electrode arc welding current Iwb, and FIGS. (G1) to (G5) are arcs. It is a schematic diagram of a generation | occurrence | production part. This figure is a timing chart of each signal in the welding apparatus described above with reference to FIGS. Therefore, although the structure of the welding apparatus of this Embodiment is the same as FIG. 7, the sequence control with respect to each signal differs. Hereinafter, a description will be given with reference to FIG.

(1) Forward feeding period (slow-down feeding period) at times t1 to t2
At time t1, as shown in FIG. 6A, when the welding start signal St becomes a high level, the consumable electrode 1a is fed forward at a slow-down speed as shown in FIGS. The no-load voltage is applied between the consumable electrode 1a and the base material 2 as shown in FIG. At the same time, a normal no-load voltage is applied between the non-consumable electrode 1b and the base material 2 without applying a high-frequency discharge high voltage, as shown in FIG.

(2) Reverse feed short circuit period from time t2 to t3 When the consumable electrode 1a contacts the base material 2 at time t2, as shown in FIG. (G2), wire feed is performed as shown in FIG. The feed electrode is rotated backward to feed the consumable electrode 1a. At the same time, as shown in FIG. 8C, the consumable electrode and the base material are reduced to a short-circuit voltage value, and as shown in FIG. Apply a small current.

(3) Reverse feed arc period from time t3 to t4 When the consumable electrode 1a is separated from the base material 2 by reverse feed at time t3, as shown in FIG. An arc is generated. This initial arc is generated not by fusing of the consumable electrode but by backward feeding and the current value is small, so that almost no spatter is generated. When the initial arc occurs, the short-circuit voltage changes to the arc voltage as shown in FIG. In this state where the initial arc is generated, the backward feeding is continued for a predetermined backward feeding arc period Td.

(4) Re-forward feeding period from time t4 to t5 When the backward feeding arc period Td elapses at time t4, the consumable electrode 1a is fed from the backward feeding to the steady feeding as shown in FIG. Switch to re-forward feed at speed. As a result, a steady welding current flows as shown in FIG. 4D, and the arc between the consumable electrode 1a and the base material 2 changes from the initial arc to the steady arc as shown in FIG. 4G4. Transition. After this time t4, as shown in FIG. 5C, the consumable electrode arc welding voltage Vwa is constant-voltage controlled to the steady value of the voltage setting signal Vr. During the period from the time t4 to the time t5, the arc length is increased by the backward feeding described above, and in addition to that, a steady welding current having a large current value is energized, so that there is a gap between the consumable electrode 1a and the base material 2. A steady arc is generated which spreads in the plasma, and a plasma atmosphere space is formed in the arc. Since the non-consumable electrode 1b is adjacent to the consumable electrode 1a, this plasma atmosphere space is also widely distributed just below the non-consumable electrode 1b.

(5) Steady feeding period after time t5 At time t5, as shown in FIG. 5E, no-load voltage is applied between the non-consumable electrode and the base material, and the non-consumable electrode 1b and the base material 2 are applied. Since the space between and is a plasma atmosphere, a non-consumable electrode arc is induced between the non-consumable electrode and the base material as shown in FIG. When the arc is generated, as shown in FIG. 5E, the no-load voltage is reduced to the arc voltage, and the non-consumable electrode arc welding current Iwb is energized as shown in FIG. At this point, both a consumable electrode arc and a non-consumable electrode arc are generated, and a good arc start is completed.

  In the above, the non-consumable electrode arc can be generated without applying a high frequency discharge high voltage or a pulsed DC high voltage. At this time, in order to stably generate the non-consumable electrode arc, the reverse feed arc period Td is important. If the arc length of the initial arc at the end of this period is slightly higher than the tip of the non-consumable electrode 1b, a plasma atmosphere space can be formed in the space immediately below the non-consumable electrode 1b, and a good arc start Is realized. Therefore, it is important for the arc start property of the non-consumable electrode arc to optimize the arc length of the consumable electrode arc during the period of time t4 to t5.

  According to the first embodiment described above, since the initial arc is generated by the backward feeding and the application of a small current at time t3, almost no spatter is generated due to the arc start of the consumable electrode arc. Further, at time t5, the non-consumable electrode arc starts without applying a high-frequency discharge high voltage, so that no strong electromagnetic noise is generated.

  FIG. 2 is a diagram showing an arc generation portion when the arc start control method of the two-electrode arc welding according to the first embodiment is applied to the plasma MIG welding described above with reference to FIG. This figure corresponds to (G4) and (G5) of FIG. 1 described above. The timing charts of FIGS. 1A to 1F are the same in the case of plasma MIG welding.

  As shown in FIG. 4G4, the reverse feed arc period Td of the consumable electrode 1a ends, and a transition is made from the initial arc to the steady arc. Due to this steady arc, the plasma atmosphere fills the space between the lower end of the shield gas nozzle 5 and the base material 2. As shown in FIG. 5G5, a plasma (non-consumable electrode) arc is generated between the non-consumable electrode and the base material in the shield gas nozzle 5 and is generated.

[Embodiment 2]
FIG. 3 is a timing chart showing an arc start control method for two-electrode arc welding according to Embodiment 2 of the present invention. This figure corresponds to FIG. 1 described above, and is different only in the initial period Ti from time t4 to t5. Hereinafter, the different initial periods Ti will be described.

  When the reverse feed arc period Td elapses at time t4, as shown in FIG. 5B, the feed speed Fw is set to a speed slower than the steady feed speed, and the re-forward feed at a predetermined initial feed speed is performed. Switch to pay. In response to this, a current smaller than the steady welding current value is applied as shown in FIG. During the initial period Ti from time t4 to t5, the consumable electrode 1a is fed forward at an initial initial feed speed that is slower than the steady feed speed, so as shown in FIG. The length becomes higher than that at time t4. For this reason, the plasma atmosphere space is further widened and formed. As a result, at time t5, as shown in FIG. 5G5, the non-consumable electrode arc is reliably induced to start the arc. When the non-consumable electrode arc is generated, as shown in FIG. 5E, the no-load voltage is reduced to the arc voltage, and the non-consumable electrode arc welding current Iwb is energized as shown in FIG. In response to this, the feed speed Fw changes to a steady feed speed as shown in FIG. 5B, and a steady welding current is applied as shown in FIG.

  FIG. 4 is a diagram showing an arc generation part when the arc start control method of the two-electrode arc welding according to the second embodiment is applied to the plasma MIG welding described above with reference to FIG. This figure corresponds to (G4) and (G5) of FIG. 1 described above. The timing charts of FIGS. 1A to 1F are the same in the case of plasma MIG welding.

  As shown in FIG. 4G4, during the initial period Ti, a consumable electrode arc having an even longer arc length occurs. This consumable electrode arc fills the plasma atmosphere in the space between the lower end of the shield gas nozzle 5 and the base material 2. As shown in FIG. 5G5, a plasma (non-consumable electrode) arc is generated between the non-consumable electrode and the base material in the shield gas nozzle 5 and is generated.

[Embodiment 3]
FIG. 5 is a timing chart showing an arc start control method for two-electrode arc welding according to Embodiment 3 of the present invention. This figure shows the case of the plasma MIG welding described above with reference to FIG. 8. The non-consumable electrode 1b has a hollow structure in the axial direction, and the consumable electrode 1a is fed through the hollow. This figure corresponds to FIG. 1 and FIG. 3 described above, and is the same signal except that the voltage setting signal Vr shown in FIG. In addition, this figure differs from FIGS. 1 and 3 in the operation after time t4. Hereinafter, these different periods will be described with reference to FIG.

  As shown in FIG. 4C, the arc length is increased and the consumable electrode arc welding voltage Vwa is increased in proportion to the arc length by the backward feeding at the times t3 to t4. When the reverse feed arc period Td elapses at time t4, re-forward feed at an initial feed speed higher than the steady feed speed is started as shown in FIG. The plasma atmosphere fills the space between the non-consumable electrode 1b and the base material 2 in the shield gas nozzle 5 by the consumable electrode arc by time t5. Therefore, at time t5, as shown in FIG. 5E, a normal no-load voltage of about 100 V causes a plasma arc between the non-consumable electrode 1b and the base material 2 as shown in FIG. (Non-consumable electrode arc) is generated, and plasma arc welding current Iwb is applied as shown in FIG. At this time, as shown in FIG. 6G5, the consumable electrode 1a is enveloped by the plasma arc, so that melting is accelerated, and as shown in FIG. 5C, the arc length burns and suddenly increases. When this amount of burn-up is large, a state called burnback occurs in which the consumable electrode 1a is welded to the lower end of the torch, resulting in an arc start failure. This burnback occurs depending on a combination condition such as the torch height, the plasma arc welding current Iwb, and the feed rate of the consumable electrode 1a. It tends to occur when the plasma arc welding current Iwb is large. Therefore, burnback may not occur depending on the welding conditions. For this reason, by making the initial feeding speed in the period from the time t4 at which re-forward feeding starts to the time t5 at which the plasma arc is generated faster than the steady feeding speed, as shown in FIG. The arc length is kept low so that welding does not occur even when the flame burns up at time t5. Further, during the period from the time t5 when the plasma arc is generated to the time t6 when the predetermined period Td2 elapses, the initial feeding speed is decreased to the steady feeding speed as shown in FIG. The arc length is quickly converged to the steady arc length by suppressing the burning. In the figure, the feeding speed Fw during the period from time t5 to t6 may be maintained as it is without being reduced, and may be returned to the steady feeding speed at time t6. The period from time t5 to t6 corresponds to the time for convergence to the steady arc length.

  According to the third embodiment described above, burnback due to burning of the consumable electrode at the time of plasma arc generation is prevented by increasing the supply speed of the consumable electrode from the starting point of re-advanced feeding to the steady feeding speed. be able to. Furthermore, the burned arc length can be quickly converged to the steady arc length by making the feeding speed during a predetermined period after the plasma arc generation faster than the steady feeding speed. For this reason, in plasma MIG welding, in addition to the effects of the first embodiment, burnback of the consumable electrode can be prevented and good arc start performance can be obtained.

[Embodiment 4]
FIG. 6 is a timing chart showing an arc start control method of two-electrode arc welding according to the fourth embodiment. This figure corresponds to FIG. 5 described above, and only the operation during the period from time t4 to t6 is different. Hereinafter, this period will be described with reference to FIG.

  In order to prevent burn-back of the consumable electrode when the plasma arc is generated at time t5, the feeding speed is increased in FIG. On the other hand, in the same figure, as shown in the figure (B1), the value of the voltage setting signal Vr is made smaller than the steady value. That is, as shown in FIG. 5B1, during the period from time t4 to t5 from the re-forward feed start time to the plasma arc occurrence time, the value of the voltage setting signal Vr is set to be smaller than the steady value. As shown in the figure (C), the arc length is lowered. Further, during the predetermined period Td2 from the time when the plasma arc is generated, the value of the voltage setting signal Vr is increased from a small initial value to a steady value. Based on the value of the voltage setting signal Vr, the consumable electrode welding voltage Vwa is controlled at a constant voltage, and the arc length is controlled. As a result, the arc length can be induced by the value of the voltage setting signal Vr. The value of the voltage setting signal Vr at times t5 to t6 may be maintained as it is at times t4 to t5.

  According to the above-described fourth embodiment, by setting the voltage setting value of the consumable electrode arc to be smaller than the steady-state value from the start of re-forward feeding, the burnback due to the burning up of the consumable electrode when the plasma arc occurs can be prevented. Can do. Furthermore, the burned arc length can be quickly converged to the steady arc length by making the voltage setting value during the predetermined period after the plasma arc generation smaller than the steady value. For this reason, in plasma MIG welding, in addition to the effects of the first embodiment, burnback of the consumable electrode can be prevented and good arc start performance can be obtained.

  In the above, instead of the voltage setting value, the plasma arc welding current Iwb shown in FIG.

It is a timing chart which shows the arc start control method of the two-electrode arc welding which concerns on Embodiment 1 of this invention. It is a schematic diagram of an arc generation part when the arc start control method of the two-electrode arc welding according to Embodiment 1 of the present invention is applied to plasma MIG welding. It is a timing chart which shows the arc start control method of the two-electrode arc welding which concerns on Embodiment 2 of this invention. It is a schematic diagram of an arc generation part when the arc start control method of the two-electrode arc welding which concerns on Embodiment 2 of this invention is applied to plasma MIG welding. It is a timing chart which shows the arc start control method of the two-electrode arc welding which concerns on Embodiment 3 of this invention. It is a timing chart which shows the arc start control method of the two-electrode arc welding which concerns on Embodiment 4 of this invention. It is a block diagram of the 2 electrode arc welding apparatus of the prior art 1. FIG. It is a block diagram of the plasma MIG welding apparatus of the prior art 2. It is a timing chart which shows the arc start control method of the two-electrode arc welding in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Consumable electrode 1b Non-consumable electrode 2 Base material 3a Consumable electrode arc 3b Non-consumable electrode arc 4a Feed tip 4b Collet 5 Shield gas nozzle 6 Feed roll 7 Plasma nozzle 8 Sputter Fc Feed control signal Fw Feed speed Iwa Consumable electrode arc welding Current Iwb Non-consumable electrode arc welding current M Wire feed motor PSM Consumable electrode arc welding power source PSP Plasma welding power source PST Non-consumable electrode arc welding power source ST Welding start circuit St Welding start signal Td Reverse feed arc period Td2 Predetermined period Ti Initial period Vr Voltage setting signal Vwa Consumable electrode arc welding voltage Vwb Non-consumable electrode arc welding voltage

Claims (4)

In an arc start control method of two-electrode arc welding in which a consumable electrode and a non-consumable electrode are provided in one shield gas nozzle at the tip of a welding torch and a consumable electrode arc and a non-consumable electrode arc are generated and welded,
When starting welding, a voltage is applied between the consumable electrode and the base material, and between the non-consumable electrode and the base material, the consumable electrode is fed forward to the base material, and when it comes into contact with the base material, it is fed back from the base material. When the consumable electrode is separated from the base material by feeding, an initial arc with a small current value is generated, and while maintaining the initial arc, the backward feeding is continued for a predetermined period to increase the arc length. The consumable electrode is re-advanced at a steady feeding speed and the welding voltage between the consumable electrode and the base metal is controlled at a constant voltage based on the steady voltage setting value to shift from the initial arc to a large current steady arc. Two electrodes characterized in that a plasma atmosphere is filled in a space between the non-consumable electrode and the base material by the consumable electrode arc to generate a non-consumable electrode arc, and the consumable electrode arc and the non-consumable electrode arc are started. Ah Arc start control method of welding.   The consumable electrode is fed at an initial feeding speed that is slower than the steady feeding speed during an initial period from the start of re-forward feeding to the occurrence of a non-consumable electrode arc. The arc start control method of two-electrode arc welding. The non-consumable electrode has a hollow structure, the consumable electrode is fed through the hollow, the consumable electrode arc is a MIG arc, and the non-consumable electrode arc is a plasma arc,
The consumable electrode is fed at an initial feeding speed that is faster than the steady feeding speed from the start of re-forward feeding, and the consumable electrode is fed at the steady feeding speed after a predetermined period of time has elapsed since the occurrence of the non-consumable electrode arc. The arc start control method for two-electrode arc welding according to claim 1, wherein: The non-consumable electrode has a hollow structure, the consumable electrode is fed through the hollow, the consumable electrode arc is a MIG arc, and the non-consumable electrode arc is a plasma arc,
The welding voltage between the consumable electrode and the base material is controlled at a constant voltage based on an initial voltage setting value smaller than the steady voltage setting value from the re-forward feed start time, and after a predetermined period has elapsed since the non-consumable electrode arc has occurred. 2. The arc start control method for two-electrode arc welding according to claim 1, wherein the welding voltage between the consumable electrode and the base material is controlled at a constant voltage based on the steady voltage setting value.

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