Laser arc hybrid welding method

Abstract

To form good beads in high-speed welding exceeding 3 m / min with a laser-arc hybrid welding method.SOLUTION: A laser-arc hybrid welding method includes welding using both laser welding and arc welding. The arc welding includes feeding a welding wire and repeating a short-circuit period and an arc period. The arc period includes a first arc period and a subsequent second arc period. The arc welding has electrode negative polarity in the first arc period of time t51 to t61 and electrode positive polarity in other periods.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a laser-arc hybrid welding method in which laser welding and consumable electrode arc welding are used in combination for welding.

Background Art

[0002] A laser-arc hybrid welding method in which consumable electrode arc welding and laser welding are used in combination for welding is commonly used (see, for example, Patent Document 1).

[0003] As the above-mentioned consumable electrode arc welding, carbon dioxide arc welding, MAG welding, MIG welding, etc. are used.

[0004] As the above-mentioned laser, a fiber laser, a semiconductor laser, a YAG laser, a carbon dioxide laser, etc. are used.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the laser-arc hybrid welding method, since there are two heat sources for one molten pool, high-speed welding is possible. However, in high-speed welding exceeding 3 m / min, it was difficult to obtain a sufficient weld bead width and throat thickness due to insufficient wire deposition amount, and it was difficult to form a good bead.

[0007] Therefore, an object of the present invention is to provide a laser-arc hybrid welding method capable of forming a good bead in high-speed welding exceeding 3 m / min.

Means for Solving the Problems

[0008] To solve the above-mentioned problems, the invention of claim 1 is: Welding is performed using a combination of laser welding and arc welding. The aforementioned arc welding is a laser arc hybrid welding method in which a welding wire is fed, and a short-circuit period and an arc period are repeated, and the arc period comprises a first arc period and a second arc period that follows it. In the aforementioned arc welding, the electrode polarity is negative during the first arc period, and the electrode polarity is positive during the rest of the period. Apply welding current, This is a laser arc hybrid welding method characterized by the following features.

[0009] The invention of claim 2 is, When switching polarity, the process should be carried out when the absolute value of the welding current is less than or equal to the reference value. The laser arc hybrid welding method according to feature 1.

[0010] The invention of claim 3 is, The welding wire is fed in reverse during the short-circuit period and in forward during the arc period. The laser arc hybrid welding method according to claim 1 or 2, characterized by the above. [Effects of the Invention]

[0011] According to the laser arc hybrid welding method of the present invention, a good bead can be formed even in high-speed welding exceeding 3 m / min. [Brief explanation of the drawing]

[0012] [Figure 1] This is a configuration diagram of a laser arc hybrid welding apparatus according to an embodiment of the present invention. [Figure 2] Figure 1 is a detailed block diagram of the welding power supply PS. [Figure 3]It is a timing chart of each signal in the welding apparatus of FIGS. 1 and 2 showing the laser-arc hybrid welding method according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a configuration diagram of a laser-arc hybrid welding apparatus according to an embodiment of the present invention. The laser-arc hybrid welding apparatus includes an arc welding apparatus for performing consumable electrode arc welding and a laser welding apparatus for performing laser welding. Hereinafter, each component will be described with reference to the same figure.

[0015] The arc welding apparatus includes a welding power source PS, a feeder WF, and a welding torch WT.

[0016] The welding power source PS performs output control such as inverter control with an AC commercial power source (not shown) such as three-phase 200 V as an input, and outputs a welding voltage Vw and a welding current Iw.

[0017] The feeder WF feeds the welding wire 1.

[0018] The welding torch WT supplies power to the welding wire 1 through a mounted power supply tip (not shown), and sends out the welding wire 1 to the welded portion of the base material 2. An arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the power supply tip and the base material 2, and a welding current Iw flows. Shielding gas 5 is ejected from the nozzle (not shown) of the welding torch WT to shield the arc 3 from the atmosphere. The material of the welding wire 1 is steel, aluminum, aluminum alloy, etc. The shielding gas 5 is carbon dioxide gas, inert gas (argon gas, helium gas, etc.), or a mixed gas of carbon dioxide gas and inert gas.

[0019] The laser welding apparatus mainly includes a laser oscillator LS, an optical fiber LF, and a processing head LH.

[0020] The laser oscillator LS outputs a laser beam 4 for laser welding.

[0021] The optical fiber LF guides the laser beam 4 to the processing head LH.

[0022] The processing head LH condenses the laser beam 4 by various built-in optical systems (not shown) and irradiates the generation part of the arc 3. In this figure, the laser beam 4 is irradiated from in front of the arc 3, but it may also be irradiated from behind. The distance between the aiming position of the arc welding and the irradiation position of the laser is about 2 to 4 mm.

[0023] Figure 2 is a detailed block diagram of the welding power source PS in Figure 1. In this figure, a circuit for applying a high voltage of several hundred volts for a short time between the welding wire 1 and the base material 2 to smooth the polarity switching is omitted. Hereinafter, each block will be described with reference to this figure.

[0024] The power control circuit PM takes a commercial power source (not shown) such as three-phase 200V as an input, performs output control by inverter control or the like according to an error amplification signal Ea described later, and switches between the electrode positive polarity EP and the electrode negative polarity EN by a polarity switching signal Dr described later to output a welding voltage Vw and a welding current Iw between the welding wire 1 and the base material 2. This power control circuit PM includes, although not shown, a primary rectifier for rectifying the commercial power source, a smoothing capacitor for smoothing the rectified direct current, an inverter circuit driven by the above error amplification signal Ea for converting the smoothed direct current into a high-frequency alternating current, a high-frequency transformer for stepping down the high-frequency alternating current to a voltage value suitable for welding, a secondary rectifier for rectifying the stepped-down high-frequency alternating current into a direct current, a reactor for smoothing the rectified direct current, and a secondary-side inverter circuit for converting the smoothed direct current into an alternating current of several tens to several hundreds of Hz based on the above polarity switching signal Dr.

[0025] The feeder WF takes a feeder control signal Fc described later as an input, and alternately repeats forward feeding and reverse feeding to feed the welding wire 1 at a feeding speed Fw. Also, generally, the welding wire 1 may be fed at a predetermined speed at a constant speed.

[0026] The welding wire 1 is fed through the welding torch WT by the rotation of the feeding roll 6 coupled to the feeder WF, and an arc 3 is generated between it and the base material 2. A welding voltage Vw is applied between the welding wire 1 and the base material 2, and a welding current Iw is passed through.

[0027] The current detection circuit ID detects the absolute value of the welding current Iw mentioned above and outputs a current detection signal Id.

[0028] The voltage detection circuit VD detects the absolute value of the welding voltage Vw and outputs a voltage detection signal Vd. The voltage setting circuit VR outputs a voltage setting signal Vr to set the welding voltage Vw during the second arc period.

[0029] The voltage error amplification circuit EV takes the above-mentioned voltage setting signal Vr and voltage detection signal Vd as inputs, amplifies the error between the two values, and outputs a voltage error amplification signal Ev.

[0030] The short-circuit detection circuit SD takes the above-mentioned voltage detection signal Vd as input and outputs a short-circuit detection signal Sd that goes to a high level when this value is less than a predetermined short-circuit detection value (approximately 10V), indicating that a short circuit is in progress, and goes to a low level when this value is greater than or equal to an arc period.

[0031] The forward transmission acceleration period setting circuit TSUR outputs a predetermined forward transmission acceleration period setting signal Tsur.

[0032] The forward / decelerate period setting circuit TSDR outputs a predetermined forward / decelerate period setting signal Tsdr.

[0033] The reverse acceleration period setting circuit TRUR outputs a predetermined reverse acceleration period setting signal True.

[0034] The reverse drive deceleration period setting circuit TRDR outputs a predetermined reverse drive deceleration period setting signal Tdr.

[0035] The forward peak value setting circuit WSR outputs a predetermined forward peak value setting signal Wsr.

[0036] The reverse peak value setting circuit WRR outputs a predetermined reverse peak value setting signal Wrr.

[0037] The feed speed setting circuit FR takes the above-mentioned forward acceleration period setting signal Tsur, forward deceleration period setting signal Tsdr, reverse acceleration period setting signal Tru, reverse deceleration period setting signal Trdr, forward peak value setting signal Wsr, reverse peak value setting signal Wrr, and short-circuit detection signal Sd as inputs and outputs the feed speed pattern generated by the following process as the feed speed setting signal Fr. When this feed speed setting signal Fr is 0 or greater, it is the forward period, and when it is less than 0, it is the reverse period. 1) During the forward acceleration period Tsu, which is determined by the forward acceleration period setting signal Tsur, a feed speed setting signal Fr is output that accelerates from 0 to a positive forward peak value Wsp, which is determined by the forward peak value setting signal Wsr. 2) Next, during the positive transmission peak period Tsp, a transmission speed setting signal Fr is output to maintain the above positive transmission peak value Wsp. 3) When the short-circuit detection signal Sd changes from a low level (arc period) to a high level (short-circuit period), the system transitions to the forward deceleration period Tsd determined by the forward deceleration period setting signal Tsdr, and outputs a feed speed setting signal Fr that decelerates the feed speed from the forward peak value Wsp to 0. 4) Next, during the reverse acceleration period Tru, which is determined by the reverse acceleration period setting signal Trur, a feed speed setting signal Fr is output, which accelerates from 0 to a negative reverse peak value Wrp, which is determined by the reverse peak value setting signal Wrr. 5) Next, during the reverse transmission peak period Trp, a transmission speed setting signal Fr is output to maintain the above reverse transmission peak value Wrp. 6) When the short-circuit detection signal Sd changes from a high level (short-circuit period) to a low level (arc period), the system transitions to the reverse-speed deceleration period Trd, determined by the reverse-speed deceleration period setting signal Trdr, and outputs a feed speed setting signal Fr that decelerates the feed speed from the reverse-speed peak value Wrp to 0. 7) By repeating steps 1) to 6) above, a feed rate setting signal Fr is generated, which has a feed pattern that changes in a positive and negative trapezoidal wave shape.

[0038] The feed control circuit FC takes the feed speed setting signal Fr as input and outputs a feed control signal Fc to the feeder WF for feeding the welding wire 1 at a feed speed Fw corresponding to the value of the feed speed setting signal Fr.

[0039] The low-level current setting circuit ILR outputs a predetermined low-level current setting signal Ilr.

[0040] The short-circuit current setting circuit ISR outputs a predetermined short-circuit current setting signal Isr.

[0041] The first arc period setting circuit TA1R outputs a predetermined first arc period setting signal Ta1r.

[0042] The first arc period circuit STA1 takes the above-mentioned short-circuit detection signal Sd and the above-mentioned first arc period setting signal Ta1r as inputs and outputs the first arc period signal Sta1, which is at a high level from the moment the short-circuit detection signal Sd changes to a low level (arc period) until the first arc period Ta1 predetermined by the first arc period setting signal Ta1r.

[0043] The first arc current setting circuit IA1R outputs a predetermined first arc current setting signal Ia1r.

[0044] The third arc period circuit STA3 takes the short-circuit detection signal Sd as input and outputs a third arc period signal Sta3 that becomes high when a predetermined current drop time Td has elapsed from the moment the short-circuit detection signal Sd changes to a low level (arc period), and then becomes low when the short-circuit detection signal Sd becomes high level (short-circuit period).

[0045] The third arc current setting circuit IA3R outputs a predetermined third arc current setting signal Ia3r.

[0046] The current control setting circuit ICR takes the above-mentioned short-circuit detection signal Sd, low-level current setting signal Ilr, short-circuit current setting signal Isr, first arc period signal Sta1, third arc period signal Sta3, first arc current setting signal Ia1r, and third arc current setting signal Ia3r as inputs, performs the following processing, and outputs the current control setting signal Icr. 1) From the moment the short-circuit detection signal Sd changes to a low level (arc period) and the first arc period signal Sta1 changes to a high level, a current control setting signal Icr, which is equal to the value of the low-level current setting signal Ilr, is output during a predetermined delay period Tc. 2) Subsequently, a current control setting signal Icr, which is the value of the first arc current setting signal Ia1r, is output. 3) After that, the current is reduced to a predetermined switching current value and the current control setting signal Icr is output. 4) During the period from when the first arc period signal Sta1 changes to a low level until the third arc period signal Sta3 changes to a low level (the second and third arc periods), a current control setting signal Icr, which is equal to the value of the third arc current setting signal Ia3r, is output. 5) When the short-circuit detection signal Sd is at a high level (short-circuit period), the current control setting signal Icr, which is equal to the value of the short-circuit current setting signal Isr, is output.

[0047] The current error amplification circuit EI takes the above-mentioned current control setting signal Icr and the above-mentioned current detection signal Id as inputs, amplifies the error between the two values, and outputs a current error amplification signal Ei.

[0048] The power supply characteristic switching circuit SW takes the above-mentioned current error amplification signal Ei, the above-mentioned voltage error amplification signal Ev, the above-mentioned first arc period signal Sta1, and the above-mentioned third arc period signal Sta3 as inputs, performs the following processing, and outputs the error amplification signal Ea. 1) During the second arc period Ta2, from when the first arc period signal Sta1 changes to a low level until the third arc period signal Sta3 changes to a high level, the voltage error amplification signal Ev is output as the error amplification signal Ea. 2) During other periods, the current error amplification signal Ei is output as the error amplification signal Ea. With this circuit, the welding power supply characteristics become constant current during the short-circuit period, the first arc period Ta1, and the third arc period Ta3, and constant voltage during the second arc period Ta2.

[0049] The polarity switching circuit DR takes the above-mentioned first arc period signal Sta1 and the above-mentioned short-circuit detection signal Sd as inputs, performs one of the following processes 1) to 3), and outputs a polarity switching signal Dr. When the polarity switching signal Dr is at a high level, the output of the welding power supply becomes electrode negative polarity EN, and when it is at a low level, it becomes electrode positive polarity EP. 1) When the first arc period signal Sta1 changes to a high level, a polarity switching signal Dr is output that changes to a high level (electrode negative polarity EN), and when it changes to a low level, it changes to a low level (electrode positive polarity EP). 2) When the first arc period signal Sta1 changes to a high level and the above delay period Tc has elapsed, a polarity switching signal Dr is output that changes to a high level (electrode negative polarity EN), and when it changes to a low level, it changes to a low level (electrode positive polarity EP). 3) When the short-circuit detection signal Sd changes to a high level (short-circuit period) and a predetermined period has elapsed, the polarity switching signal Dr changes to a high level (negative electrode polarity EN), and when the first arc period signal Sta1 changes to a low level, the polarity switching signal Dr changes to a low level (positive electrode polarity EP).

[0050] Figure 3 is a timing chart of each signal in the welding apparatus shown in Figures 1 and 2, illustrating a laser arc hybrid welding method according to an embodiment of the present invention. Figure (A) shows the time variation of the feed rate Fw, Figure (B) shows the time variation of the welding current Iw, Figure (C) shows the time variation of the welding voltage Vw, Figure (D) shows the time variation of the short-circuit detection signal Sd, Figure (E) shows the time variation of the first arc period signal Sta1, Figure (F) shows the time variation of the third arc period signal Sta3, and Figure (G) shows the time variation of the polarity switching signal Dr. The operation of each signal will be explained below with reference to the figure.

[0051] In the same figure, although not shown, laser light 4 is irradiated onto the non-welded area. The feed speed Fw shown in Figure (A) indicates a forward feed state where the welding wire 1 is fed forward toward the base material 2 when it is a positive value, and a reverse feed state where it is fed backward toward the base material 2 when it is a negative value. The feed speed Fw is controlled by the value of the feed speed setting signal Fr output from the feed speed setting circuit FR in Figure 2. The feed speed Fw is formed from the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur in Figure 1, the forward feed peak period Tsp which continues until a short circuit occurs, the forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr in Figure 1, the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Tru in Figure 1, the reverse feed peak period Trp which continues until an arc occurs, and the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Tdr in Figure 1. Furthermore, the positive feed peak value Wsp is determined by the positive feed peak value setting signal Wsr in Figure 1, and the negative feed peak value Wrp is determined by the negative feed peak value setting signal Wrr in Figure 1. As a result, the feed speed setting signal Fr has a feed pattern that changes in a roughly trapezoidal wave shape with positive and negative values. The welding current Iw shown in Figure (B) and the welding voltage Vw shown in Figure (C) show the waveform when the electrode is positive polarity EP when the value is positive, and the waveform when the electrode is negative polarity EN when the value is negative.

[0052] [Operation during the short-circuit period from time t1 to t4] During the short-circuit period, as shown in Figure (G), the polarity switching signal Dr is at a low level, so the output of the welding power supply becomes electrode positive polarity EP. Therefore, during the short-circuit period, the welding current Iw shown in Figure (B) and the welding voltage Vw shown in Figure (C) are positive values. When a short circuit occurs at time t1 during the positive feed peak period Tsp, as shown in Figure (C), the welding voltage Vw rapidly decreases to a short-circuit voltage of a few volts, and as shown in Figure (D), the short-circuit discrimination signal Sd changes to a high level (short-circuit period). In response to this, the system transitions to a predetermined positive feed deceleration period Tsd from time t1 to t2, and as shown in Figure (A), the feed rate Fw is reduced from the positive feed peak value Wsp to 0.

[0053] As shown in Figure (A), the feed rate Fw enters a predetermined reverse acceleration period Tru from time t2 to t3, accelerating from 0 to the reverse peak value Wrp. The short-circuit period continues during this period.

[0054] When the reverse acceleration period Tru ends at time t3, the feed rate Fw enters the reverse peak period Trp, as shown in Figure (A), and becomes the reverse peak value Wrp. The reverse peak period Trp continues until an arc occurs at time t4. Therefore, the period from time t1 to t4 is the short-circuit period.

[0055] As shown in Figure (B), the instantaneous value of the welding current Iw during the short-circuit period from time t1 to t4 is controlled by a constant current to the value of the short-circuit current setting signal Isr shown in Figure 2. The value of this short-circuit current setting signal Isr is set to be less than or equal to the average value of the welding current Iw. The average value of the welding current Iw is approximately determined by the average value of the feed rate Fw. Preferably, the value of the short-circuit current setting signal Isr is set to 100A or less, and more preferably to 70A or less. By controlling the welding current Iw to a small current value during the short-circuit period in this way, the generation of spatter when a short circuit occurs is suppressed, and the smooth absorption of molten droplets into the molten pool is promoted.

[0056] [Operation during the arc period from time t4 to t7] At time t4, as the welding wire is reversed, constriction progresses and an arc is generated. As shown in Figure (C), the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts, and as shown in Figure (D), the short-circuit detection signal Sd changes to a low level (arc period). In response to this, as shown in Figure (E), the first arc period signal Sta1 changes to a high level, and the period from time t4 to t61 becomes the predetermined first arc period Ta1. The first arc period Ta1 is set by the first arc period setting signal Ta1r in Figure 1. Constant current control is performed during the first arc period Ta1. Simultaneously, the process transitions to the predetermined reverse-feed deceleration period Trd from time t4 to t5, and as shown in Figure (A), the feed rate Fw is reduced from the reverse-feed peak value Wrp to 0.

[0057] When the reverse deceleration period Trd ends at time t5, the system transitions to a predetermined forward acceleration period Tsu from time t5 to t6. During this forward acceleration period Tsu, as shown in Figure (A), the feed rate Fw accelerates from 0 to the forward peak value Wsp. The arc period continues during this period.

[0058] When the forward acceleration period Tsu ends at time t6, the feed rate Fw enters the forward peak period Tsp, as shown in Figure (A), and becomes the forward peak value Wsp. The arc period continues during this period as well. The forward peak period Tsp continues until a short circuit occurs at time t7. Therefore, the period from time t4 to t7 is the arc period. When a short circuit occurs, the operation returns to that of time t1.

[0059] When an arc is generated at time t4, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts, as shown in Figure (C). On the other hand, as shown in Figure (B), the welding current Iw is the value of the low-level current setting signal Ilr in Figure 1 for a predetermined delay period Tc from time t4. This is because if the current value is increased immediately after the arc is generated, the reverse feeding of the welding wire and the melting of the welding wire due to the welding current will be added together, causing the arc length to increase rapidly and potentially making the welding state unstable. This delay period Tc may also be set to 0.

[0060] At time t51 during the forward feed acceleration period Tsu, when the delay period Tc ends, as shown in Figure (G), the polarity switching signal Dr changes to a high level, and the output of the welding power supply becomes electrode negative polarity EN. When the delay period Tc=0, the electrode becomes negative polarity EN at time t4. In response to this, as shown in Figure (B), the welding current Iw becomes a low-level current value with a negative value, and as shown in Figure (C), the welding voltage Vw also becomes a negative arc voltage value. As shown in Figure (B), the welding current Iw increases from time t51 to maintain the first arc current value Ia1 set by the first arc current setting signal Ia1r, and thereafter decreases to a predetermined switching current value at time t61. As shown in Figure (C), the welding voltage Vw also has a waveform similar to that of the welding current Iw. The reason for reducing the welding current Iw to a switching current value of about 50~100A is as follows. If the current value during polarity switching is large, a problematic surge voltage may be applied to the transistors constituting the secondary inverter circuit of the power control circuit PM in Figure 1, potentially causing them to be destroyed. This is to prevent that from happening.

[0061] At time t61, when the first arc period Ta1 ends, as shown in Figure (G), the polarity switching signal Dr changes to a low level, and the output of the welding power supply becomes electrode positive polarity EP. In response to this, as shown in Figure (B), the welding current Iw becomes a positive switching current value, and as shown in Figure (C), the welding voltage Vw also becomes a positive arc voltage value. The period from time t61 to t62 becomes the second arc period Ta2, and the welding power supply is switched to constant voltage control. As shown in Figure (B), the second arc current Ia2 becomes a value corresponding to the arc load, and as shown in Figure (C), the welding voltage Vw becomes a value controlled by the voltage setting signal Vr in Figure 2. By controlling this second arc period Ta2 with constant voltage, the arc length is controlled to an appropriate value.

[0062] At time t62, after a predetermined current drop time Td has elapsed since the arc generation time t4, the third arc period signal Sta3 changes to a high level, as shown in Figure (F). The period from this point until time t7, when the next short circuit occurs, is the third arc period Ta3. During the third arc period Ta3, as shown in Figure (G), the polarity switching signal Dr remains at a low level, so the output of the welding power supply becomes electrode positive polarity EP. Constant current control is performed during the third arc period Ta3. As shown in Figure (B), a predetermined third arc current Ia3, determined by the third arc current setting signal Ia3r in Figure 1, is supplied. As shown in Figure (C), the welding voltage Vw becomes a value determined by the current value and the arc load. By making the third arc current value Ia3 immediately before the short circuit a small value, the occurrence of a short circuit can be induced, and spatter generation at the time of the short circuit can be suppressed.

[0063] Numerical examples for each of the above parameters are shown below: Short circuit period (not a specified value): 3ms, Arc period (not a specified value): 4ms, Delay period Tc (specified value): 0.5ms, First arc period Ta1 (specified value): 1.5ms, Second arc period Ta2 (not a specified value): 2ms, Third arc period Ta3 (not a specified value): 0.5ms, Current drop time (specified value): 3.5ms, Low-level current value (specified value): 50A, First arc current value Ia1 (specified value): -150A, Third arc current value Ia3 (specified value): 50A, Forward transmission peak value Wsp (specified value): 30m / min, Reverse transmission peak value Wrp (specified value): -25m / min.

[0064] According to the above-described embodiment, in a laser-arc hybrid welding method in which welding is performed using both laser welding and arc welding, the arc welding involves feeding a welding wire and repeatedly alternating between a short-circuit period and an arc period, and the arc period comprises a first arc period and a subsequent second arc period, in which the second arc period of the arc welding is set to negative electrode polarity, and the rest of the period is set to positive electrode polarity. In the arc welding, since the first arc period is set to negative electrode polarity EN, the amount of wire welded can be increased. For this reason, in this embodiment, in high-speed welding exceeding 3 m / min, the amount of wire welded can be increased to secure the necessary weld bead width and throat thickness, and a good bead can be formed.

[0065] More preferably, according to this embodiment, when switching polarity, the absolute value of the welding current is kept below a reference value. In this way, it is possible to prevent the transistors constituting the secondary inverter circuit provided for switching polarity from being damaged by a problematic surge voltage.

[0066] More preferably, according to this embodiment, the welding wire is fed in the reverse direction during the short-circuit period and in the forward direction during the arc period. In this way, the repetition cycle between the short-circuit period and the arc period is stabilized, thereby improving the welding quality during high-speed welding. [Explanation of Symbols]

[0067] 1. Welding wire 2 Base material 3 Arc 4. Laser light 5. Shielding gas 6 Feeding Rolls DR polarity switching circuit Dr polarity switching signal Ea Error Amplification Signal EI Current Error Amplifier Circuit Ei Current Error Amplification Signal EV voltage error amplification circuit Ev Voltage Error Amplification Signal FC feed control circuit Fc feed control signal FR feed speed setting circuit Fr feed speed setting signal Fw Feed speed Ia1 First arc current IA1R First Arc Current Setting Circuit Ia1r First arc current setting signal Ia2 Second arc current Ia3 Third arc current IA3R Third Arc Current Setting Circuit Ia3r Third arc current setting signal ICR Current Control Setting Circuit Icr current control setting signal ID Current Detection Circuit Id Current detection signal ILR Low-Level Current Setting Circuit Ilr Low-level current setting signal ISR Short-Circuit Current Setting Circuit ISR short-circuit current setting signal Iw welding current LF optical fiber LH machining head LS laser oscillator PM Power Control Circuit PS welding power supply SD Short Circuit Detection Circuit Sd short-circuit detection signal STA1 First Arc Period Circuit Sta1 First Arc Period Signal STA3 Third Arc Period Circuit Sta3 Third Arc Period Signal SW Power supply characteristic switching circuit TA1R First Arc Period Setting Circuit Ta1r First arc period setting signal Tc delay period Td Current drop time Trd Reverse feed deceleration period TRDR Reverse Drive Deceleration Period Setting Circuit Trdr Reverse feed deceleration period setting signal Trp reverse transmission peak period Tru Reverse acceleration period TRUR Reverse Acceleration Period Setting Circuit Trur reverse acceleration period setting signal Tsd Forward feed deceleration period TSDR Forward feed deceleration period setting circuit Tsdr Forward feed deceleration period setting signal Tsp peak period for forward transmission Tsu forward acceleration period TSUR Forward feed acceleration period setting circuit Tsur Forward feed acceleration period setting signal VD Voltage Detection Circuit Vd voltage detection signal VR voltage setting circuit Vr voltage setting signal Vw welding voltage WF feeder Wrp reverse peak value WRR reverse peak value setting circuit Wrr reverse peak value setting signal Wsp positive peak value WSR positive feed peak value setting circuit WSR positive transmit peak value setting signal WT welding torch

Claims

1. Welding is performed using a combination of laser welding and arc welding. The aforementioned arc welding is a laser arc hybrid welding method in which a welding wire is fed, and a short-circuit period and an arc period are repeated, and the arc period comprises a first arc period and a second arc period that follows it. The aforementioned arc welding is performed by applying a welding current that has negative polarity to the electrode during the first arc period and positive polarity to the electrode during all other periods. A laser arc hybrid welding method characterized by the following features.

2. When switching polarity, the process should be carried out when the absolute value of the welding current is less than or equal to the reference value. The laser arc hybrid welding method according to feature 1.

3. The welding wire is fed in reverse during the short-circuit period and in forward during the arc period. The laser arc hybrid welding method according to claim 1 or 2, characterized by the above.

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