JP5926589B2 - Plasma MIG welding method - Google Patents

Description

  The present invention relates to a plasma MIG welding method for performing welding by simultaneously generating a MIG arc and a plasma arc using a single welding torch.

  Conventionally, a plasma MIG welding method combining a plasma welding method and a MIG welding method has been proposed (see, for example, Patent Document 1). In this plasma MIG welding method, a plasma arc is generated by passing a plasma welding current between a plasma electrode and a base material arranged in a welding torch. At the same time, the plasma electrode is formed into a hollow shape, and a welding wire fed through a power supply tip disposed in the plasma electrode is fed through the hollow shape, and between the welding wire and the base material. A MIG arc is generated by applying a MIG welding current. Therefore, the MIG arc is wrapped in a plasma arc. The welding wire functions as an electrode for generating a MIG arc, and the tip of the welding wire melts to form a droplet to assist the joining of the base materials. Therefore, the plasma MIG welding method is often used for high-efficiency welding of thick plates, high-speed welding of thin plates, and the like.

  In general, a DC pulse waveform is often used for the MIG welding current in order to suppress generation of spatter and stably supply droplets. Therefore, the MIG welding method is a general MIG pulse welding method. In the consumable electrode type arc welding method including the MIG pulse welding method, it is important to maintain the arc length during welding at an appropriate value, and therefore arc length control is performed. A DC or DC pulse waveform is used for the plasma welding current. In the following description, when the arc length is simply described, it means the arc length of the MIG arc. Hereinafter, the plasma MIG welding method described above will be described.

  FIG. 6 is a waveform diagram showing a plasma MIG welding method in the prior art. (A) shows the MIG welding current Iwm, (B) shows the MIG welding voltage Vwm, (C) shows the plasma welding current Iwp, and (D) shows the plasma welding voltage Vwp. Show. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 6A, a MIG welding current Iwm composed of a peak current Ip during the peak period Tp and a base current Ib during the base period Tb is energized. The peak period Tp and the base period Tb are combined to form a pulse period Tf. Corresponding to the energization of the MIG welding current Iwm, the peak voltage Vp is applied between the welding wire and the base material during the peak period Tp, and during the base period Tb, as shown in FIG. A base voltage Vb is applied.

  In MIG pulse welding, arc length control is performed to maintain the arc length at an appropriate value in order to obtain good welding quality. Normally, this arc length control uses the fact that the MIG welding voltage Vwm is substantially proportional to the arc length, and controls the pulse cycle so that the average value of the MIG welding voltage Vwm is equal to a predetermined voltage setting value. Is done. The average value of the MIG welding voltage Vwm is generated by passing the MIG welding voltage Vwm through a low-pass filter. This arc length control method is called a frequency modulation method. In this case, the peak period Tp, the peak current Ip, and the base current Ib are set to predetermined values and become pulse parameters. The peak current Ip is set to a critical value or more and is called a unit pulse condition in combination with the peak period Tp. This unit pulse condition is set so that one droplet period is one droplet transfer. The base current Ib is set to a small current value of about several tens of A that is less than the critical value. The unit pulse condition and the base current Ib are set to appropriate values according to the welding wire material, diameter, feeding speed, and the like.

  On the other hand, as shown in FIG. 5C, the plasma welding current Iwp is constant-current controlled and becomes a DC waveform having a predetermined constant value. Further, as shown in FIG. 4D, a plasma welding voltage Vwp is applied between the plasma electrode and the base material. Therefore, the plasma arc is generated by energizing the plasma welding current Iwp with a constant value.

  In the invention of Patent Document 2, in the plasma MIG welding method, the arc intensity distribution is changed by changing at least one of the generation position and generation angle of the MIG arc within the generation range of the plasma arc. In Patent Document 2, a groove is formed with respect to a narrow groove made of a material having good heat conductivity such as aluminum or steel by shifting the generation position or generation angle of the MIG arc within the generation range of the plasma arc. It is described that high-quality welding can be performed without increasing the length or making the arc length longer than necessary.

JP 2008-229641 A JP-A-2-147169

  In the plasma MIG welding method described above, the wire melting efficiency is increased by the effect of preheating the welding wire by the plasma arc, so that high-weld welding is possible. However, in the case of welding conditions where the amount of deposited metal is large relative to the preheating width of the base metal by the plasma arc (the width in the direction perpendicular to the weld line of the portion where the plasma arc contacts the base metal), There is a problem that the fatigue strength is reduced and the fatigue strength is reduced. In order to solve this problem, a method of weaving the welding torch in a direction (left-right direction) orthogonal to the welding progress direction is performed. If it does in this way, the preheating range of a base material will spread by weaving, and the familiarity of a bead toe part will be improved. However, in this method, since the mig arc is also weaved, there is a new problem that rough beads are formed on the bead surface and the bead appearance is deteriorated.

  Therefore, in the present invention, the plasma MIG welding method that can improve the fit of the bead end and the appearance of the bead in a welding condition in which the amount of deposited metal is large with respect to the preheating range of the base metal by the plasma arc. The purpose is to provide.

In order to solve the above-described problems, the invention of claim 1
A plasma arc is generated by applying a plasma welding current between a plasma electrode and a base material arranged in a welding torch and energizing a plasma welding current, and the plasma electrode has a hollow shape, A welding wire fed through a power feed tip disposed on the wire is fed through the hollow shape, and a MIG welding current is applied between the power feed tip and the base material to pass a MIG welding current. In a plasma MIG welding method for generating a MIG arc by:
The difference between the preheat width of the base metal and the bead width due to the plasma arc is measured, and when the difference is less than a predetermined reference value, the MIG arc is not weaved, only the plasma arc is weaved and welded, When the difference is not less than the reference value, welding is performed without weaving the MIG arc and the plasma arc.
This is a plasma MIG welding method.

In the invention of claim 2, the weaving is performed by swinging the plasma electrode without swinging the feeding tip and the welding wire.
The plasma MIG welding method according to claim 1.

  According to the present invention, the MIG arc is moved on the welding line without being weaved, and the plasma arc is welded while being weaved in the left-right direction. For this reason, since the preheating width of the base material by the plasma arc is widened, the familiarity of the bead toe is improved and the fatigue strength is improved. At this time, since the mig arc moves on the weld line without being weaved, there is no phenomenon that a rough wave is formed on the bead surface and the bead appearance is deteriorated.

It is a block diagram of the welding apparatus for enforcing the plasma MIG welding method which concerns on Embodiment 1 of this invention. It is a block diagram of the MIG welding power supply PSM which comprises FIG. It is a block diagram of the plasma welding power supply PSP which comprises FIG. It is a wave form diagram which shows the plasma MIG welding method which concerns on Embodiment 1 of this invention. 6 is a block diagram of a plasma welding power source PSP according to Embodiment 2. FIG. It is a wave form diagram which shows the plasma MIG welding method in a prior art.

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

[Embodiment 1]
FIG. 1 is a configuration diagram of a welding apparatus for performing a plasma MIG welding method according to Embodiment 1 of the present invention. Hereinafter, each component will be described with reference to FIG.

  This welding apparatus includes a welding torch WT, a MIG welding power source PSM, and a plasma welding power source PSP surrounded by a broken line. The welding torch WT has a structure in which a plasma nozzle 51, a plasma electrode 1b, and a power feed tip 4 are arranged on a concentric axis in a shield gas nozzle 52. From the gap between the shield gas nozzle 52 and the plasma nozzle 51, for example, a shield gas 63 such as argon gas or a mixed gas of argon gas and carbon dioxide gas is supplied. A plasma gas 62 such as argon gas or a mixed gas of argon gas and carbon dioxide gas is supplied between the plasma nozzle 51 and the plasma electrode 1b. A center gas 61 such as argon gas or a mixed gas of argon gas and carbon dioxide gas is supplied between the plasma electrode 1 b and the power feed tip 4.

  The plasma electrode 1b is formed in a hollow shape. The power feeding chip 4 is insulated and disposed in the hollow shape of the plasma electrode 1b. And the welding wire 1a is fed from the through-hole provided in this electric power feeding chip | tip 4. FIG. The power feed tip 4 is electrically connected to the welding wire 1a. However, the welding wire 1a is insulated from the plasma electrode 1b. The welding wire 1a is fed by the rotation of the feed roll 7 using the feed motor WM as a drive source. The plasma electrode 1b is made of, for example, copper or a copper alloy, and is indirectly water-cooled by cooling water passing through a path outside the figure. The plasma nozzle 51 is made of, for example, copper or a copper alloy, and is directly cooled by forming a flow path through which cooling water passes. The welding torch WT is moved relative to the base material 2 while being held by a normal robot (not shown). A mig arc 3 a is generated between the tip of the welding wire 1 a and the base material 2. Between the plasma electrode 1 b and the base material 2, a plasma arc 3 b thermally generated by the plasma gas 62 is generated. Therefore, the MIG arc 3a is in a state of being surrounded by the plasma arc 3b. For this reason, the plasma arc 3b has the effect | action which restrains that the shape of the mig arc 3a spreads.

  As shown in the figure, since a part of the protruding portion of the welding wire 1a is surrounded by the plasma arc 3b, the temperature rises upon receiving heat. This is a preheating effect on the welding wire 1a by the plasma arc 3b described above.

  The weaving drive mechanism 8 is provided in the upper part in the welding torch WT, and is used for weaving the plasma electrode 1b, the plasma nozzle 51, and the shield gas nozzle 52 in the left-right direction of the welding direction with the input of a weaving control signal Ws described later. A mechanism including a motor. Conventionally, a mechanism for converting the rotational motion of the motor into a linear motion by a slider crank mechanism, a mechanism for converting the rotational motion of the motor into a swinging motion by a crank and a swing rod, and the like are used. As a result, the plasma arc 3b, the plasma gas 62, and the shield gas 63 are weaved. On the other hand, the feed tip 4 and the welding wire 1a are not weaved. For this reason, the mig arc 3a and the center gas 61 are not weaved. For example, when the inner diameter of the shield gas nozzle 52 is 19 mm, the inner diameter of the plasma nozzle 51 is 12 mm, and the inner diameter of the plasma electrode 1 b is 9 mm, the weaving frequency is set to 5 Hz and the amplitude is set to ± 2 mm.

  The MIG welding power source PSM is a power source for energizing the MIG welding current Iwm by applying the MIG welding voltage Vwm between the welding wire 1 a and the base material 2 via the power supply tip 4. A feed control signal Fc is sent from the MIG welding power source PSM to the feed motor WM, and the feed speed of the welding wire 1a is controlled. When the MIG welding voltage Vwm is applied from the MIG welding power source PSM, the welding wire 1a is set to the + side. The MIG welding power supply PSM is a power supply having a constant voltage characteristic, and is controlled so that the MIG welding voltage Vwm is equal to a predetermined voltage setting signal Vr (not shown). Further, the value of the MIG welding current Iwm is determined by the feeding speed of the welding wire 1a.

  The plasma welding power source PSP is a power source for energizing the plasma welding current Iwp by applying a plasma welding voltage Vwp between the plasma electrode 1b and the base material 2. From the plasma welding power source PSP, a weaving control signal Ws is sent to the weaving drive mechanism 8, and the weaving frequency and amplitude of the plasma arc 3b are controlled. When the plasma welding voltage Vwp is applied from the plasma welding power source PSP, the plasma electrode 1b is set to the + side. The plasma welding power source PSP is a power source having a constant current characteristic, and is controlled so that the plasma welding current Iwp becomes a predetermined value.

  FIG. 2 is a block diagram of the MIG welding power source PSM constituting the above-described FIG. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200V, performs output control such as inverter control according to a current error amplification signal Ei described later, and outputs a MIG welding voltage Vwm and a MIG welding current Iwm. To do. Although not shown, the power supply main circuit PM includes a primary rectifier circuit that rectifies commercial power, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current into high frequency alternating current, and high frequency alternating current An inverter transformer that steps down the voltage to a voltage suitable for arc welding, a secondary rectifier circuit that rectifies the stepped-down high-frequency alternating current, a reactor that smoothes the rectified direct current, and PWM modulation control according to the current error amplification signal Ei And a drive circuit for driving the inverter circuit based on the result. The welding wire 1 a is fed through the power feed tip 4 by a feed roll 7 coupled to a feed motor WM, and a mig arc 3 a is generated between the welding wire 1 a and the base material 2. The structure of the welding torch is as shown in FIG. 1, and is shown here in a simplified manner.

  The voltage detection circuit VD detects the MIG welding voltage Vwm and outputs a voltage detection signal Vd. The voltage average value calculation circuit VAV calculates an average value of the voltage detection signal Vd and outputs a voltage average value signal Vav.

  The feeding speed setting circuit FR outputs a predetermined feeding speed setting signal Fr. The feed control circuit FC inputs the feed speed setting signal Fr and feeds a feed control signal Fc for feeding the welding wire 1a at a feed speed Fw determined by the value of the feed speed setting signal Fr. Output to motor WM.

  The voltage setting circuit VR outputs a predetermined voltage setting signal Vr. The voltage error amplification circuit EV amplifies an error between the voltage setting signal Vr and the voltage average value signal Vav, and outputs a voltage error amplification signal Ev. The voltage / frequency conversion circuit VF outputs a pulse period signal Tf having a frequency corresponding to the value of the voltage error amplification signal Ev. The pulse period signal Tf is a trigger signal that becomes High level for a short time every pulse period.

  The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr. The peak period timer circuit TP outputs a peak period signal Tp that is at a high level only during a period determined by the value of the peak period setting signal Tpr when the pulse period signal Tf is at a high level. The peak period is the peak period when the peak period signal Tp is at the high level, and the base period is when the peak period signal Tp is at the low level.

  The base current setting circuit IBR outputs a predetermined base current setting signal Ibr. The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr. The current setting control circuit IRC outputs the base current setting signal Ibr as the current setting control signal Irc when the peak period signal Tp is at the low level, and outputs the peak current setting signal Ipr as the current when the peak period signal Tp is at the high level. It is output as a setting control signal Irc.

  The current detection circuit ID detects the MIG welding current Iwm and outputs a current detection signal Id. The current error amplification circuit EI amplifies an error between the current setting control signal Irc and the current detection signal Id, and outputs a current error amplification signal Ei. The MIG welding current Iwm is energized by controlling the output of the welding power source in accordance with the current error amplification signal Ei. The above-described MIG welding power source PSM is a power source having constant voltage characteristics because the output is controlled by changing the pulse period so that the average value of the MIG welding voltage Vwm becomes equal to the value of the voltage setting signal Vr.

  The figure shows the case where the MIG welding current Iwm has a pulse waveform. When the MIG welding current Iwm is a DC waveform, the voltage error amplification signal Ev is directly input to the power supply main circuit PM instead of the current error amplification signal Ei. You can do it. In this way, the MIG arc 3a is DC MIG welding.

  FIG. 3 is a block diagram of the plasma welding power source PSP that constitutes FIG. 1 described above. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as a three-phase 200V as input, performs output control such as inverter control according to a current error amplification signal Ei described later, and outputs a plasma welding current Iwp. The plasma welding current Iwp is energized through the plasma electrode 1b, the plasma arc 3b, and the base material 2. The structure of the welding torch is as shown in FIG. 1 described above, but is shown here in a simplified manner.

  Plasma welding current setting circuit IWPR outputs a predetermined plasma welding current setting signal Iwpr. The current detection circuit ID detects the plasma welding current Iwp and outputs a current detection signal Id. The current error amplification circuit EI amplifies an error between the plasma welding current setting signal Iwpr and the current detection signal Id and outputs a current error amplification signal Ei. The direct current plasma welding current Iwp is energized by controlling the output of the welding power source in accordance with the current error amplification signal Ei. Since the plasma welding power source PSP described above is output-controlled so that the plasma welding current Iwp is equal to the value of the plasma welding current setting signal Iwpr, it is a power source with constant current characteristics.

  The weaving frequency setting circuit FPR outputs a predetermined weaving frequency setting signal Fpr. The weaving amplitude setting circuit DPR outputs a predetermined weaving amplitude setting signal Dpr. The weaving control circuit WS has a weaving control signal Ws that changes sinusoidally at a frequency determined by the weaving frequency setting signal Fpr and an amplitude determined by the weaving amplitude setting signal Dpr, and is provided in the welding torch WT of FIG. Output to the drive mechanism 8. The weaving control signal Ws will be described in detail with reference to FIG.

  This figure shows the case where the plasma welding current Iwp is a DC waveform. However, when the pulse welding waveform is used, the plasma welding current setting signal Iwpr may be set to a pulse waveform.

  FIG. 4 is a waveform diagram showing the plasma MIG welding method according to Embodiment 1 of the present invention. (A) shows the MIG welding current Iwm (A), (B) shows the MIG welding voltage Vwm (V), (C) shows the plasma welding current Iwp (A), (D) shows the plasma welding voltage Vwp (V), (E) shows the weaving control signal Ws, (F) shows the right and left displacement Lm (mm) of the MIG arc, (G) Indicates the left-right displacement Lp (mm) of the plasma arc. In the figure, the time scale shown on the horizontal axis is reduced by about 50 times compared to the case of FIG. 51 described above. For this reason, the pulse waveforms in FIGS. 1A and 1B are the same as those in FIG. 51, but the time axis is shortened, so that the pulse waveforms are dense. These frequencies are about 100 to 300 Hz. In accordance with the weaving control signal Ws shown in FIG. 5E, weaving of the plasma arc is performed in a direction (left-right direction) orthogonal to the weld line. The left and right displacement amount Lm of the MIG arc shown in FIG. 4F indicates the amount of displacement in the left and right direction with respect to the weld line. Since the MIG arc is not weaved, Lm = 0 is always set. Similarly, the left-right displacement amount Lp of the plasma arc shown in FIG. 5G indicates the left-right displacement amount with respect to the weld line. The right and left displacement Lm of the MIG arc is the right and left displacement of the power feed tip 4 and the welding wire 1a in FIG. The displacement amount Lp of the plasma arc is the lateral displacement amount of the center line of the plasma electrode 1b in FIG. Hereinafter, a description will be given with reference to FIG.

  The MIG welding current Iwm shown in FIG. 6A and the MIG welding voltage Vwm shown in FIG. 5B are the same as those in FIG. 51 described above except that the time axis is shortened. Is omitted. Further, the plasma welding current Iwp shown in FIG. 5C and the plasma welding voltage Vwp shown in FIG. 4D are the same as those in FIG.

  The left and right displacement amount Lm of the MIG arc shown in FIG. 5F is always 0 mm because weaving is not performed as described above. As shown in FIG. 5E, the weaving control signal Ws is a signal that changes in a sine wave shape at a predetermined frequency and amplitude. As shown in FIG. 5G, the left-right displacement amount Lp of the plasma arc changes in a sine wave shape in synchronization with the weaving control signal Ws, the frequency becomes the weaving frequency fp (Hz), and the amplitude becomes the weaving amplitude Dp ( mm). The weaving frequency fp and the weaving amplitude Dp are set by the weaving control signal Ws. The weaving frequency fp is set to about 1 to 20 Hz, and the weaving amplitude Dp is set to about ± 1 to ± 3 mm. Both values are set to appropriate values according to the joint shape, the welding wire feeding speed, the welding speed, the material of the base material, and the like. In this way, the lateral movement range of the plasma electrode 1b is widened to the inner diameter + 2 × Dp, and the preheating width of the plasma arc is also widened by 2 × Dp. In the figure, the weaving control signal Ws and the left-right displacement amount Lp of the plasma arc change in a sine wave shape, but may change in a triangular wave shape. Further, weaving may be performed so as to stop at the left end and the right end for a short time.

  An example of welding conditions is shown below. The inner diameter of the plasma electrode 1b is 9 mm, an aluminum wire having a diameter of 1.2 mm is used as the welding wire, the feeding speed is 9 m / min, the MIG welding current Iwm = 170 A, the MIG welding voltage Vwm = 19 V, and the plasma welding current Iwp. = Weighting frequency fp = 5 Hz and weaving amplitude Dp = ± 2 mm under the conditions of 100 A and welding speed 1 m / min. In this way, the lateral movement range of the plasma electrode 1b is widened from 9 mm to 13 mm. As a result, the preheating width by the plasma arc is also widened by 4 mm by weaving.

  According to the first embodiment described above, the mig arc is moved on the welding line without being weaved, and the plasma arc is welded while being weaved in the left-right direction. For this reason, since the preheating width of the base material by the plasma arc is widened, the familiarity of the bead toe is improved and the fatigue strength is improved. At this time, since the mig arc moves on the weld line without being weaved, there is no phenomenon that a rough wave is formed on the bead surface and the bead appearance is deteriorated. It is also conceivable to increase the inner diameter of the plasma electrode 1b in order to widen the preheating range by the plasma arc. However, if it does in this way, the restraint force to a plasma arc will become weak and the high concentration which is the characteristic of a plasma arc will be lost. Furthermore, since a stable MIG arc is generated by being encased in the plasma arc having high concentration, the stability of the MIG arc is lowered when the binding force to the plasma arc is weakened. On the other hand, in the present embodiment, the preheating width by the plasma arc can be widened without increasing the inner diameter of the plasma electrode 1b.

[Embodiment 2]
As described above, in the conventional technique, there is a problem that the familiarity of the bead toe portion is deteriorated in a welding condition in which the amount of deposited metal is large with respect to the preheating width of the base metal by the plasma arc. In the case of welding conditions in which the amount of deposited metal is larger than the preheating width of the base metal by the plasma arc, the difference between the preheating width of the base metal by the plasma arc and the bead width is small. In other words, when the difference between the preheat width of the base metal due to the plasma arc and the bead width is large, the familiarity of the bead toe is good.

Therefore, the plasma MIG welding method according to Embodiment 2 is performed in the following steps.
Step 1: Before the work, test welding is performed without weaving both the plasma arc and the MIG arc, and the preheating width and bead width of the base material by the plasma arc are measured, and the difference between the two values is measured.

Step 2: In the construction work, the measured difference is input to the welding apparatus (plasma welding power source PSP in FIG. 5). The plasma welding power source PSP outputs a mode switching signal Ms that is at a high level when the difference is less than a predetermined reference value and that is at a low level in the above case.

Step 3: When the mode switching signal Ms is at the high level, the plasma welding power source PSP outputs the weaving control signal Ws in which the frequency and amplitude of the weaving are set to appropriate values (values other than 0) to the weaving drive mechanism 8. By doing so, the mig arc is not weaved, but only the plasma arc is weaved to perform welding.

Step 4: On the other hand, when the mode switching signal Ms is at the low level, the plasma welding power source PSP outputs the weaving control signal Ws in which the frequency and amplitude of the weaving are set to 0 to the weaving drive mechanism 8. Welding is performed without weaving both the MIG arc and plasma arc.

  The reference value is set to about 2 to 5 mm. This reference value is set as a value at which the familiarity of the bead toe is good if the above difference is equal to or greater than this reference value.

  The configuration of the welding apparatus for performing the plasma MIG welding method according to Embodiment 2 is the same as that in FIG. 1 described above. However, a block diagram of the plasma welding power source PSP constituting the welding apparatus will be described with reference to FIG.

  FIG. 5 is a block diagram of a plasma welding power source PSP according to the second embodiment. In the figure, the same blocks as those in FIG. 3 described above are denoted by the same reference numerals, and description thereof is omitted. In the figure, a difference input circuit DW and a mode switching circuit MS are newly added, and the weaving control circuit WS of FIG. 3 is replaced with a second weaving control circuit WS2. Hereinafter, these blocks will be described with reference to FIG.

  The difference input circuit DW outputs the difference signal Dw when the difference between the preheat width of the base metal by the plasma arc measured by test welding and the bead width is input as numerical data. The difference signal Dw is, for example, numerical data of 2 (mm). This circuit performs a part of the processing of Step 1 described above.

  The mode switching circuit MS receives the difference signal Dw, and outputs a mode switching signal Ms that is at a high level when the value of the difference signal Dw is less than a predetermined reference value and that is at a low level when the difference signal Dw is above. . This circuit performs the processing of step 2 described above.

  The second weaving control circuit WS2 receives the mode switching signal Ms, the weaving frequency setting signal Fpr, and the weaving amplitude setting signal Dpr, and when the mode switching signal Ms = High level, the frequency determined by the weaving frequency setting signal Fpr and A weaving control signal Ws that changes in a sinusoidal shape with an amplitude determined by the weaving amplitude setting signal Dpr is output to the weaving drive mechanism 8 provided in the welding torch WT of FIG. 1, and is 0 when the mode switching signal Ms = Low level. The remaining weaving control signal Ws is output to the weaving drive mechanism 8. This circuit performs the processing of steps 3 and 4 described above.

  Waveform diagrams showing the plasma MIG welding method according to Embodiment 2 are as follows. The waveform diagram when the mode switching signal Ms is at the high level (the value of the difference signal Dw is less than the reference value) is the same as that in FIG. 4 described above. On the other hand, the waveform diagram when the mode switching signal Ms is at the low level (the value of the difference signal Dw is equal to or greater than the reference value) is different from FIG. That is, since the plasma arc is not weaved, the difference is that the left-right displacement amount Lp of the plasma arc shown in FIG.

  According to the second embodiment described above, the difference between the preheat width of the base metal due to the plasma arc and the bead width is measured, and when this difference is less than a predetermined reference value, as in the first embodiment, the MIG arc Welding is performed by weaving only the plasma arc without weaving. For this reason, as in the first embodiment, in the welding conditions in which the amount of the deposited metal is large with respect to the preheating range of the base metal by the plasma arc, the bead toe is well-fitted and the bead appearance is also good. be able to. On the other hand, when the measured difference is greater than or equal to the reference value, welding is performed without weaving both the MIG arc and the plasma arc. This case is a case where the preheating width has a margin with respect to the bead width, and in this case, the familiarity of the bead toe portion is good. Therefore, it is not necessary to weave the plasma arc. Thus, by stopping weaving when weaving is unnecessary, the maintenance interval of the weaving drive mechanism 8 can be extended, and the production efficiency can be increased.

DESCRIPTION OF SYMBOLS 1a Welding wire 1b Plasma electrode 2 Base material 3a Mig arc 3b Plasma arc 4 Feed tip 51 Plasma nozzle 52 Shield gas nozzle 61 Center gas 62 Plasma gas 63 Shield gas 7 Feeding roll 8 Weaving drive mechanism Dp Weaving amplitude setting circuit Dpr Weaving Amplitude setting signal DW Difference input circuit Dw Difference signal EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC Feed control circuit Fc Feed control signal fp Weaving frequency FPR Weaving frequency setting circuit Fpr Weaving Frequency setting signal FR Feeding speed setting circuit Fr Feeding speed setting signal Fw Feeding speed Ib Base current IBR Base current setting circuit Ibr Base current setting signal ID Current detection circuit Id Current detection signal p Peak current IPR Peak current setting circuit Ipr Peak current setting signal IRC Current setting control circuit Irc Current setting control signal Iwm Mig welding current Iwp Plasma welding current IWPR Plasma welding current setting circuit Iwpr Plasma welding current setting signal Lm Mig arc left / right displacement Lp Left and right displacement of plasma arc MS Mode switching circuit Ms Mode switching signal PM Power supply main circuit PSM Mig welding power supply PSP Plasma welding power supply Tb Base period Tf Pulse period (signal)
TP Peak period timer circuit Tp Peak period (signal)
TPR Peak period setting circuit Tpr Peak period setting signal VAV Voltage average value calculation circuit Vav Voltage average value signal Vb Base voltage VD Voltage detection circuit Vd Voltage detection signal VF Voltage / frequency conversion circuit Vp Peak voltage VR Voltage setting circuit Vr Voltage setting signal Vwm MIG welding voltage Vwp Plasma welding voltage WM Feeding motor WS Weaving control circuit Ws Weaving control signal WS2 Second weaving control circuit WT Welding torch

Claims (2)

A plasma arc is generated by applying a plasma welding current between a plasma electrode and a base material arranged in a welding torch and energizing a plasma welding current, and the plasma electrode has a hollow shape, A welding wire fed through a power feed tip disposed on the wire is fed through the hollow shape, and a MIG welding current is applied between the power feed tip and the base material to pass a MIG welding current. In a plasma MIG welding method for generating a MIG arc by:
The difference between the preheat width of the base metal and the bead width due to the plasma arc is measured, and when the difference is less than a predetermined reference value, the MIG arc is not weaved, only the plasma arc is weaved and welded, When the difference is not less than the reference value, welding is performed without weaving the MIG arc and the plasma arc.
The plasma MIG welding method characterized by the above-mentioned. The weaving is performed by swinging the plasma electrode without swinging the feeding tip and the welding wire.
The plasma MIG welding method according to claim 1.

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