Arc welding method

Abstract

To carry out high-quality welding for a thin plate having a large gap in a welding joint using a base material which is an aluminum material.SOLUTION: A base material is an aluminum material, and an arc-welding method is for executing welding by switching between a period in which pulse arc-welding is carried out with the feed speed Fw of a welding wire set in forward feeding and a period in which short circuit transfer arc-welding is carried out with the feed speed Fw of the welding wire set in backward feeding. The pulse arc-welding at time of t1-t2 is AC pulse arc-welding formed by an electrode positive polarity period and an electrode negative polarity period. The short circuit transfer arc-welding at time of t2-t3 is electrode negative polarity short circuit transfer arc-welding formed by an arc period and a short circuit period. Further, a time ratio of the period of the AC pulse arc-welding in a total welding period is 30%-70%.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an arc welding method in which welding is performed by alternately switching between a period in which a welding wire is fed in the normal direction to perform pulse arc welding and a period in which a welding wire is fed in the normal direction to perform short-circuit transfer arc welding. [Background technology]

[0002] In order to reduce the heat input to the base material and weld thin plates with high quality, the inventions disclosed in Patent Documents 1 and 2 are commonly used. In the AC pulse arc welding method according to Patent Document 1, welding is performed by feeding a welding wire and repeating one cycle of passing a peak current and a base current during an electrode positive polarity period and passing an electrode negative polarity current during an electrode negative polarity period. In this AC pulse arc welding, the electrode negative polarity ratio, which is the time ratio of the electrode negative polarity period in one cycle, can be changed by adjusting the electrode negative polarity period, thereby controlling the heat input to the base metal. This enables low heat input welding and high quality thin plate welding.

[0003] In the welding method according to Patent Document 2, welding is performed by feeding a welding wire and alternating between a period of pulse arc welding and a period of short circuit transfer arc welding. In this welding method, the heat input to the base material can be controlled by adjusting the ratio between the period of pulse arc welding and the period of short circuit transfer arc welding. This enables low heat input welding and high quality thin plate welding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2018 / 079345 [Patent Document 2] Patent Publication No. 2021-53649 Summary of the Invention [Problem to be solved by the invention]

[0005] In thin plate welding, when there is a gap in the welded joint, it is necessary to form a bead shape with a small dilution ratio by making the penetration part small and the excess part large. However, with the conventional welding methods such as those in Patent Documents 1 and 2, it was difficult to weld thin plates with large gaps with high quality when the base metal was aluminum.

[0006] Therefore, an object of the present invention is to provide an arc welding method capable of performing high-quality welding on a thin plate whose base material is aluminum and which has a large gap at the weld joint. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the invention of claim 1 comprises: In an arc welding method in which a base material is an aluminum material, welding is performed by alternately switching between a period in which a welding wire is fed in a forward direction to perform pulse arc welding and a period in which the welding wire is fed in a forward and reverse direction to perform short-circuit transfer arc welding, The pulse arc welding is AC pulse arc welding formed of an electrode positive polarity period and an electrode negative polarity period, The short circuit transfer arc welding is an electrode negative polarity short circuit transfer arc welding formed from an arc period and a short circuit period. The present invention relates to an arc welding method.

[0008] The invention of claim 2 is as follows: The time ratio of the AC pulse arc welding period to the total welding period is in the range of 30% to 70%. 2. The arc welding method according to claim 1,

[0009] The invention of claim 3 is as follows: When the AC pulse arc welding is in the electrode negative polarity period, the arc period is switched to the electrode negative polarity short-circuit transfer arc welding period. 3. The arc welding method according to claim 1, wherein the first and second electrodes are connected to each other.

[0010] The invention of claim 4 is as follows: When the electrode negative polarity short circuit transfer arc welding is in the arc period, switching is made to the electrode negative polarity period of the AC pulse arc welding. 4. The arc welding method according to claim 1, wherein the first and second electrodes are connected to each other. Effect of the Invention

[0011] According to the present invention, high-quality welding can be performed on a thin plate whose base material is aluminum and which has a large gap at the weld joint. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram of a welding power source for carrying out an arc welding method according to an embodiment of the present invention. [Diagram 2] 2 is a timing chart of each signal in FIG. 1 illustrating the arc welding method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0014] Fig. 1 is a block diagram of a welding power source for carrying out an arc welding method according to an embodiment of the present invention. In the figure, a high voltage application circuit for polarity switching is omitted. Each block will be described below with reference to the figure.

[0015] The inverter circuit INV receives an AC commercial power source (not shown) such as 3-phase 200V, and performs inverter control of the rectified and smoothed DC voltage by pulse width modulation control using an error amplification signal Ea (described later), to output a high-frequency AC voltage. The inverter transformer INT steps down the high-frequency AC voltage to a voltage value suitable for arc welding. The secondary rectifiers D2a to D2d rectify the stepped-down high-frequency AC voltage to a DC voltage.

[0016] The electrode positive polarity transistor PTR is turned on by an electrode positive polarity drive signal Pd (described later), at which time the output of the welding power supply becomes the electrode positive polarity EP. The electrode negative polarity transistor NTR is turned on by an electrode negative polarity drive signal Nd (described later), at which time the output of the welding power supply becomes the electrode negative polarity EN.

[0017] Reactor WL smoothes the ripple in the output.

[0018] The welding wire 1 is fed through the welding torch 4 by the rotation of a feed roll 5 connected to a wire feed motor WM, and an arc 3 is generated between the welding wire 1 and the base metal 2. A welding voltage Vw is applied between the welding wire 1 and the base metal 2, and a welding current Iw flows between the welding wire 1 and the base metal 2. The base metal 2 is made of aluminum. The shielding gas sprayed from the tip of the welding torch 4 is 100% argon gas.

[0019] The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The voltage averaging circuit VAV averages the absolute value of the voltage detection signal Vd and outputs a voltage average value signal Vav. The voltage setting circuit VR outputs a predetermined voltage setting signal Vr. The voltage error amplifier circuit EV amplifies the error between the voltage setting signal Vr and the voltage average value signal Vav and outputs a voltage error amplification signal Ev.

[0020] The electrode positive polarity peak period setting circuit TPR outputs a predetermined electrode positive polarity peak period setting signal Tpr, and the electrode positive polarity base period setting circuit TBR outputs a predetermined electrode positive polarity base period setting signal Tbr.

[0021] The electrode negative polarity period setting circuit TNR outputs a predetermined electrode negative polarity period setting signal Tnr.

[0022] The timer circuit TM receives as input a welding method switching signal Sm, which will be described later, the electrode negative polarity period setting signal Tnr, the electrode positive polarity peak period setting signal Tpr, and the electrode positive polarity base period setting signal Tbr, performs the following processing, and outputs a timer signal Tm. 1) When the welding method switching signal Sm changes to 1, or when the electrode positive polarity base period Tb ends, the electrode negative polarity period Tn set by the electrode negative polarity period setting signal Tnr begins, and a timer signal Tm=1 is output. 2) Then, the electrode positive polarity peak period Tp set by the electrode positive polarity peak period setting signal Tpr begins, and the timer signal Tm=2 is output. 3) Then, the electrode positive polarity base period Tb set by the electrode positive polarity base period setting signal Tbr begins, and the timer signal Tm=3 is output. 4) During the period when the welding method switching signal Sm=1, the above steps 1) to 3) are repeated.

[0023] The electrode positive peak current setting circuit IPR receives the voltage error amplified signal Ev, performs feedback control so that the voltage average signal Vav becomes equal to the voltage setting signal Vr, and outputs the electrode positive peak current setting signal Ipr. This circuit feedback controls the electrode positive peak current Ip so that the arc length becomes an appropriate value.

[0024] The electrode positive polarity base current setting circuit IBR outputs a predetermined electrode positive polarity base current setting signal Ibr.

[0025] The electrode negative polarity current setting circuit INR outputs a predetermined electrode negative polarity current setting signal Inr.

[0026] The switching circuit SW receives the timer signal Tm, the electrode positive polarity peak current setting signal Ipr, the electrode positive polarity base current setting signal Ibr, and the electrode negative polarity current setting signal Inr as inputs, performs the following processing, and outputs a current setting signal Ir. 1) When the timer signal Tm=1, the electrode negative polarity current setting signal Inr is output as the current setting signal Ir. 2) When the timer signal Tm=2, the electrode positive polarity peak current setting signal Ipr is output as the current setting signal Ir. 3) When the timer signal Tm=3, the electrode positive polarity base current setting signal Ibr is output as the current setting signal Ir.

[0027] The current detection circuit ID detects the absolute value of the welding current Iw and outputs a current detection signal Id. The current error amplifier circuit EI amplifies the error between the current setting signal Ir and the current detection signal Id and outputs a current error amplified signal Ei.

[0028] The AC pulse arc welding period setting circuit TAR outputs a predetermined AC pulse arc welding period setting signal Tar. The electrode negative polarity short circuit transfer arc welding period setting circuit TSR outputs a predetermined electrode negative polarity short circuit transfer arc welding period setting signal Tsr.

[0029] The short circuit determination circuit SD receives the voltage detection signal Vd as input, and when this value is less than the short circuit determination value (approximately 10 V), it determines that a short circuit period has occurred and outputs a short circuit determination signal Sd that goes to a High level, and when this value is equal to or greater than the short circuit determination value, it determines that an arc period has occurred and outputs a Low level.

[0030] The welding method switching circuit SM receives as inputs the AC pulse arc welding period setting signal Tar, the electrode negative polarity short circuit transfer arc welding period setting signal Tsr, the timer signal Tm and the short circuit discrimination signal Sd, performs the following processing, and outputs a welding method switching signal Sm. 1) When the period set by the AC pulse arc welding period setting signal Tar has elapsed since the welding method switching signal Sm changed to 1, and the timer signal Tm is 1 (electrode negative polarity period Tn), the welding method switching signal Sm is set to 2. 2) When the period set by the electrode negative polarity short circuit transfer arc welding period setting signal Tsr has elapsed since the welding method switching signal Sm changed to 2 and the short circuit discrimination signal Sd is at a low level (arc period), the welding method switching signal Sm=1 is output. 3) Repeat steps 1) and 2) above.

[0031] The error amplifier circuit EA receives the above-mentioned current error amplified signal Ei, the above-mentioned voltage error amplified signal Ev, and the above-mentioned welding method switching signal Sm, performs the following processing, and outputs an error amplified signal Ea. 1) When the welding method switching signal Sm=1 (AC pulse arc welding period Ta), the current error amplified signal Ei is output as the error amplified signal Ea. 2) When the welding method switching signal Sm=2 (electrode negative polarity short-circuit transfer arc welding period Ts), the voltage error amplified signal Ev is output as the error amplified signal Ea.

[0032] The drive circuit DV receives the welding method switching signal Sm and the timer signal Tm, performs the following processing, and outputs a drive signal Dv. The drive signal Dv is formed from an electrode negative polarity drive signal Nd and an electrode positive polarity drive signal Pd. 1) When the welding method switching signal Sm=2 or the timer signal Tm=1, the electrode negative polarity drive signal Nd is output. 2) When the welding method switching signal Sm=1 and the timer signal Tm=2 or 3, the electrode positive polarity drive signal Pd is output. Therefore, during the electrode negative polarity short circuit transfer arc welding period Ts, the electrode negative polarity is EN. During the electrode negative polarity period Tn in the AC pulse arc welding period Ta, the electrode negative polarity is EN, and during the electrode positive polarity peak period Tp and the electrode positive polarity base period Tb, the electrode positive polarity is EP.

[0033] The pulse arc period feed rate setting circuit FAR outputs a pulse arc period feed rate setting signal Far that is a predetermined positive value.

[0034] The short circuit arc period feed speed setting circuit FSR receives the above-mentioned short circuit discrimination signal Sd as an input and outputs a short circuit arc period feed speed setting signal Fsr which has a predetermined reverse feed peak value of a negative value when the short circuit discrimination signal Sd is at a high level (short circuit period) and a predetermined forward feed peak value of a positive value when the short circuit discrimination signal Sd is at a low level (arc period).

[0035] Therefore, the welding wire is fed in the forward direction during the AC pulse arc welding period Ta, and is fed in the forward and reverse directions during the electrode negative polarity short circuit transfer arc welding period Ts. The feed speed setting circuit FR receives as inputs the welding method switching signal Sm, the pulse arc period feed speed setting signal Far, and the short circuit arc period feed speed setting signal Fsr, and outputs the pulse arc period feed speed setting signal Far as the feed speed setting signal Fr when the welding method switching signal Sm=1, and outputs the short circuit arc period feed speed setting signal Fsr as the feed speed setting signal Fr when the welding method switching signal Sm=2.

[0036] The feed control circuit FC receives the feed speed setting signal Fr as an input and outputs a feed control signal Fc to the wire feed motor WM for feeding the welding wire 1 at a feed speed Fw corresponding to this value.

[0037] Fig. 2 is a timing chart of each signal in the welding power source of Fig. 1, which shows the arc welding method according to the embodiment of the present invention. Fig. 2(A) shows the change over time of the welding method switching signal Sm, Fig. 2(B) shows the change over time of the timer signal Tm, Fig. 2(C) shows the change over time of the feed speed Fw, Fig. 2(D) shows the change over time of the welding current Iw, Fig. 2(E) shows the change over time of the welding voltage Vw, Fig. 2(F) shows the change over time of the short circuit determination signal Sd, and Fig. 2(G) shows the change over time of the drive signal Dv. The operation of each signal will be described below with reference to the figures.

[0038] The welding method switching signal Sm shown in FIG. 1A is an AC pulse arc welding period Ta when Sm=1, and is an electrode negative polarity short circuit transfer arc welding period Ts when Sm=2. The timer signal Tm shown in FIG. 1B is an electrode negative polarity period Tn when Tm=1, an electrode positive polarity peak period Tp when Tm=2, and is an electrode positive polarity base period Tb when Tm=3. The feed speed Fw shown in FIG. 1C indicates a positive feed in which the welding wire is forward fed toward the base metal, and a negative value indicates a reverse feed in which the welding wire is reverse fed in a direction away from the base metal. The welding current Iw shown in FIG. 1D indicates a positive value of the electrode positive polarity EP in which current flows from the welding wire to the base metal, and a negative value of the electrode negative polarity EN in which current flows from the base metal to the welding wire. The welding voltage Vw shown in FIG. 1(E) indicates that a positive value indicates electrode positive polarity EP, where the welding wire is positive and the base metal is negative, and a negative value indicates electrode negative polarity EN, where the base metal is positive and the welding wire is negative. When the values ​​of the welding current Iw and welding voltage Vw are listed, their absolute values ​​are shown regardless of the electrode polarity. The drive signal Dv shown in FIG. 1(G) indicates that the electrode negative polarity drive signal Nd in FIG. 1 is output when it is at a high level, resulting in electrode negative polarity EN, and that the electrode positive polarity drive signal Pd in ​​FIG. 1 is output when it is at a low level, resulting in electrode positive polarity EP. In order to prevent arc interruption when switching polarity, a restrike voltage of several hundred volts is applied between the welding wire and the base metal for a short period of time.

[0039] As shown in the same figure (A), the welding method switching signal Sm is 2 (electrode negative polarity short circuit transfer arc welding period Ts) before time t2, 1 (AC pulse arc welding period Ta) between times t2 and t3, 2 (electrode negative polarity short circuit transfer arc welding period Ts) between times t3 and t4, and 1 (AC pulse arc welding period Ta) from time t4 onwards.

[0040] (1) Operation during the electrode negative polarity short-circuit transfer arc welding period Ts before time t2 During this period, as shown in FIG. 1A, the welding method switching signal Sm=2, and the electrode negative polarity short circuit transition arc welding period Ts begins. As shown in FIG. 1G, the drive signal Dv becomes a High level, and the electrode negative polarity EN begins. Therefore, the welding current Iw shown in FIG. 1D and the welding voltage Vw shown in FIG. 1E are negative values. The period from time t1 to t11 is the short circuit period, and the period from time t11 to t2 is the arc period. During the short circuit period from time t1 to t11, the short circuit discrimination signal Sd becomes a High level, as shown in FIG. 1F. In response to this, as shown in FIG. 1C, the feed speed Fw becomes a predetermined reverse feed peak value of a negative value, and the welding wire is fed in reverse. As shown in FIG. 1D, the welding current Iw gradually increases. As shown in FIG. 1E, the welding voltage Vw becomes a short circuit voltage value of several volts. When an arc is generated at time t11, as shown in FIG. 1F, the short circuit discrimination signal Sd changes to a Low level. In response to this, as shown in Fig. 1C, the feed speed Fw changes to a predetermined positive peak value with a slope, and the welding wire is fed in the positive direction. As shown in Fig. 1D, the welding current Iw gradually decreases. As shown in Fig. 1E, the welding voltage Vw becomes an arc voltage value of several tens of volts.

[0041] (2) Operation during AC pulse arc welding period Ta from time t2 to t3 At time t2, the period set by the electrode negative polarity short circuit transition arc welding period setting signal Tsr in Fig. 1 has elapsed since the time when the welding method switching signal Sm=2 was changed, and since the short circuit determination signal Sd is at low level (arc period), the welding method switching signal Sm is switched to 1 and the AC pulse arc welding period Ta starts. Therefore, if it is a short circuit period when the period set by the electrode negative polarity short circuit transition arc welding period setting signal Tsr in Fig. 1 has elapsed since the time when the welding method switching signal Sm=2 was changed, the welding method switching signal Sm is delayed until it becomes an arc period, and then the welding method switching signal Sm is switched to the AC pulse arc welding period Ta. The AC pulse arc welding period Ta always starts from the electrode negative polarity period Tn. For this reason, as shown in FIG. 1B, the timer signal Tm is 1 (electrode negative polarity period Tn) during the period from time t2 to t21, 2 (electrode positive polarity peak period Tp) during the period from time t21 to t22, and 3 (electrode positive polarity base period Tb) during the period from time t22 to t23. As shown in FIG. 1C, the feed speed Fw is decelerated from the positive feed peak value to a constant value set by the pulse arc period feed speed setting signal Far in FIG. 1, and the welding wire is fed in the positive direction. Since basically no short circuit occurs during this period, as shown in FIG. 1F, the short circuit discrimination signal Sd remains at a low level. (21) During the electrode negative polarity period Tn from time t2 to t21, as shown in FIG. 1(G), the drive signal Dv becomes a high level and the electrode polarity becomes negative EN. As shown in FIG. 1(D), the welding current Iw becomes a predetermined electrode negative polarity current with a negative value, and as shown in FIG. 1(E), the welding voltage Vw becomes an arc voltage value with a negative value proportional to the arc length. The electrode negative polarity period may be formed from an electrode negative polarity base period in which an electrode negative polarity base current flows and an electrode negative polarity peak period in which an electrode negative polarity peak current flows. (22) During the electrode positive polarity peak period Tp from time t21 to t22, as shown in FIG. 1(G), the drive signal Dv becomes low level and the polarity is reversed to the electrode positive polarity EP. As shown in FIG. 1(D), the welding current Iw becomes the electrode positive polarity peak current that is feedback-controlled to a positive value, and as shown in FIG. 1(E), the welding voltage Vw becomes the arc voltage value that is proportional to the arc length and has a positive value. The value of the electrode positive polarity peak current is feedback-controlled so that the average value of the welding voltage Vw becomes equal to the value of the voltage setting signal Vr in FIG. 1. This controls the arc length to an appropriate value. The electrode positive polarity peak period Tp is formed by a rise period, a maximum value period, and a fall period. In addition to the above-mentioned electrode positive polarity peak current modulation method, the arc length control method can also include a periodic modulation method and an electrode positive polarity peak period modulation method. (23) During the electrode positive polarity base period Tb from time t22 to t23, as shown in FIG. 14(G), the drive signal Dv is at a low level, and the electrode positive polarity EP is maintained. As shown in FIG. 14(D), the welding current Iw is a predetermined electrode positive polarity base current of a positive value, and as shown in FIG. 14(E), the welding voltage Vw is an arc voltage value of a positive value proportional to the arc length. In the figure, two periods of the waveform are displayed during the period from time t2 to t3.

[0042] (3) Operation during the electrode negative polarity short-circuit transfer arc welding period Ts from time t3 to t4 At time t3, the period set by the AC pulse arc welding period setting signal Tar in FIG. 1 has elapsed since the welding method switching signal Sm changed to Sm=1 at time t1, and the timer signal Tm=1 (electrode negative polarity period Tn) is in effect, so the welding method switching signal Sm is switched to 2 and the electrode negative polarity short circuit transition arc welding period Ts begins. Therefore, if the period set by the AC pulse arc welding period setting signal Tar in FIG. 1 has elapsed since the welding method switching signal Sm=1 and is in a period other than the electrode negative polarity period Tn, the welding method switching signal Sm is delayed until the electrode negative polarity period Tn is reached and then transitioned to the electrode negative polarity short circuit transition arc welding period Ts. This period always starts with an arc period. During this period, as shown in FIG. 1(G), the drive signal Dv becomes a High level and becomes the electrode negative polarity EN. (31) During the arc period from time t3 to t31, the short circuit determination signal Sd becomes low level, as shown in FIG. 1(F). In response to this, as shown in FIG. 1(C), the feed speed Fw accelerates with a slope from the positive pulse arc period feed speed at time t2 to a positive positive feed peak value, as shown in FIG. 1(D), the welding current Iw gradually decreases from the negative electrode negative polarity current value. As shown in FIG. 1(E), the welding voltage Vw becomes a negative arc voltage value of several tens of volts. (32) During the short circuit period from time t31 to t32, the short circuit determination signal Sd becomes high level, as shown in FIG. 1(F). In response to this, as shown in FIG. 1(C), the feed speed Fw changes with a slope from a forward feed peak value to a reverse feed peak value of a negative value, and the welding wire is fed in reverse. As shown in FIG. 1(D), the welding current Iw gradually increases. As shown in FIG. 1(E), the welding voltage Vw becomes a short circuit voltage value of several volts. (33) During the arc period from time t32 to t33, as shown in FIG. 1(F), the short circuit determination signal Sd becomes low level. In response to this, as shown in FIG. 1(C), the feed speed Fw changes from a negative reverse feed peak value to a positive forward feed peak value with a slope, and the welding wire is fed forward. As shown in FIG. 1(D), the welding current Iw gradually decreases. As shown in FIG. 1(E), the welding voltage Vw becomes an arc voltage value of several tens of volts. From time t33, the short circuit period begins again. In FIG. 1(F), two cycles of waveforms are displayed during the period from time t3 to t4.

[0043] At time t4, the operation returns to that at time t2, and the above operation is repeated. Each of the AC pulse arc welding period Ta and the electrode negative polarity short circuit transfer arc welding period Ts has a cycle of about 10 ms. Each period includes at least one cycle, and is in the range of about 1 to 50 cycles.

[0044] Numerical examples of the above parameters are shown below. Base material = aluminum material, shielding gas = 100% argon gas (1) AC pulsed arc welding parameters Pulse arc period feed speed = 10m / min (150A), welding voltage = 18V, electrode negative polarity ratio = 20% Electrode negative polarity period = 1.5 ms, electrode negative polarity current = 150 A Electrode positive polarity peak period = 3.0 ms (rise period = 1.0 ms + maximum value period = 1.0 ms + fall period = 1.0 ms), electrode positive polarity peak current (feedback value) = approx. 350 A Electrode positive polarity base period = 4.0 ms, Electrode positive polarity base current = 50 A (2) Electrode negative polarity short circuit transfer arc welding parameters Feed speed (average value) = 8m / min (100A) Peak forward speed = 20m / min Reverse feed peak value = -15m / min Welding voltage = 11V

[0045] The effects of this embodiment will be described below. According to the above-mentioned embodiment, in an arc welding method in which the base material is an aluminum material, a period in which the welding wire is fed forward to perform pulse arc welding and a period in which the welding wire is fed forward and backward to perform short circuit transfer arc welding are alternately switched, the pulse arc welding is AC pulse arc welding formed of an electrode positive polarity period and an electrode negative polarity period, and the short circuit transfer arc welding is electrode negative polarity short circuit transfer arc welding formed of an arc period and a short circuit period. In order to perform low heat input high adhesion welding on a thin plate having a large gap at a welded joint, it is most effective to perform electrode negative polarity short circuit transfer arc welding by feeding the welding wire forward and backward. However, when the base material is an aluminum material, the cleaning action of removing the oxide film does not work in electrode negative polarity short circuit transfer arc welding, resulting in poor welding. To solve this problem, a period in which AC pulse arc welding is performed is added. By adding AC pulse arc welding, a cleaning action works in the electrode positive polarity peak period and the electrode positive polarity base period, so that the oxide film can be removed and good welding can be performed. Furthermore, since AC pulse arc welding has an electrode negative polarity period, it is a low heat input high deposition welding. As a result, in this embodiment, the base material is an aluminum material, and high quality welding can be performed on a thin plate having a large gap at the weld joint.

[0046] More preferably, according to this embodiment, the time ratio of the AC pulse arc welding period to the total welding period is in the range of 30% to 70%. If the time ratio is less than 30%, the cleaning effect is not sufficient, resulting in poor welding. If the time ratio exceeds 70%, the low heat input high welding effect of the electrode negative polarity short circuit transfer arc welding is reduced, narrowing the range of application.

[0047] More preferably, according to this embodiment, when AC pulse arc welding is in an electrode negative polarity period, the arc period is switched to electrode negative polarity short circuit transfer arc welding. The transition from the electrode negative polarity period of AC pulse arc welding to the arc period of electrode negative polarity short circuit transfer arc welding is of the same polarity and the same arc period, so that the transition state is smooth and the welding state is stabilized.

[0048] More preferably, according to this embodiment, when the arc period of electrode negative polarity short circuit transfer arc welding is in progress, the period is switched to the electrode negative polarity period of AC pulse arc welding. Since the transition from the arc period of electrode negative polarity short circuit transfer arc welding to the electrode negative polarity period of AC pulse arc welding is of the same polarity and the same arc period, the transition state is smooth and the welding state is stabilized. [Explanation of symbols]

[0049] 1 Welding wire 2 Base material 3. Arc 4. Welding torch 5 Feeding roll D2a~D2d Secondary rectifier DV driver circuit Dv drive signal EA Error Amplifier Circuit Ea Error amplification signal EI Current Error Amplifier Circuit Ei Current error amplification signal EN Electrode negative polarity EP electrode positive polarity EV voltage error amplifier circuit Ev Voltage error amplified signal FAR Pulse arc period feed speed setting circuit Far pulse arc period feed speed setting signal FC feed control circuit Fc feed control signal FR feed speed setting circuit Fr feed speed setting signal FSR Short circuit arc period feed speed setting circuit Fsr Short circuit arc period feed speed setting signal Fw Feed speed IBR Electrode positive polarity base current setting circuit Ibr Electrode positive polarity base current setting signal ID Current Detection Circuit Id Current detection signal INR Electrode negative polarity current setting circuit Inr Electrode negative polarity current setting signal INT Inverter transformer INV Inverter circuit Ip Electrode positive peak current IPR Electrode positive polarity peak current setting circuit Ipr Electrode positive polarity peak current setting signal Ir Current setting signal Iw Welding current Nd electrode negative polarity drive signal NTR Negative polarity transistor Pd electrode positive polarity drive signal PTR Electrode Positive Polarity Transistor SD Short circuit detection circuit Sd Short circuit detection signal SM Welding method switching circuit Sm Welding method switching signal SW switching circuit Ta AC pulse arc welding period TAR AC pulse arc welding period setting circuit Tar AC pulse arc welding period setting signal Tb electrode positive polarity base period TBR Electrode positive polarity base period setting circuit Tbr Electrode positive polarity base period setting signal TM timer circuit Tm Timer signal Tn Electrode negative polarity period TNR Electrode negative polarity period setting circuit Tnr Electrode negative polarity period setting signal Tp electrode positive polarity peak period TPR electrode positive polarity peak period setting circuit Tpr electrode positive polarity peak period setting signal Ts Electrode negative polarity short circuit transfer arc welding period TSR Electrode negative polarity short circuit transfer arc welding period setting circuit Tsr Electrode negative polarity short circuit transfer arc welding period setting signal VAV Voltage averaging circuit Vav Average voltage signal VD voltage detection circuit Vd Voltage detection signal VR voltage setting circuit Vr Voltage setting signal Vw welding voltage WL Reactor WM Wire feed motor

Claims

1. In an arc welding method in which a base material is an aluminum material, welding is performed by alternately switching between a period in which a welding wire is fed in a forward direction to perform pulse arc welding and a period in which the welding wire is fed in a forward and reverse direction to perform short-circuit transfer arc welding, The pulse arc welding is AC pulse arc welding formed of an electrode positive polarity period and an electrode negative polarity period, The short circuit transfer arc welding is an electrode negative polarity short circuit transfer arc welding formed from an arc period and a short circuit period.

1. An arc welding method comprising:

2. The time ratio of the AC pulse arc welding period to the total welding period is in the range of 30% to 70%.

2. The arc welding method according to claim 1 .

3. When the AC pulse arc welding is in the electrode negative polarity period, switching to the arc period of the electrode negative polarity short-circuit transfer arc welding is performed.

3. The arc welding method according to claim 1 or 2.

4. When the electrode negative polarity short circuit transfer arc welding is in the arc period, switching is made to the electrode negative polarity period of the AC pulse arc welding.

4. The arc welding method according to claim 1, wherein the welding is performed in a manner similar to that described above.

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