Alternating current consumable electrode electric arc welding control method

Abstract

The invention provides an alternating current consumable electrode arc welding control method. In an AC consumable electrode arc welding method, the welding state during the period of negative polarity of an electrode is stabilized, so that the welding quality is good. A short-circuit period and an arc period are repeated between a welding wire and a base material, the welding wire is fed in a reverse direction during the short-circuit period and fed in a forward direction during the arc period, and the electrode polarity is periodically switched between an electrode positive polarity period (Tep) including at least one arc period and an electrode negative polarity period (Ten). In the AC consumable electrode arc welding control method, the absolute value of the peak value of the forward feed of the feed speed (Fw) and the absolute value of the peak value of the reverse feed of the feed speed (Fw) are set to be larger in the electrode negative polarity period (Ten) at the time t4-t7 than in the electrode positive polarity period (Tep) at the time t1-t4.

Description

Technical Field

[0001] The present invention relates to an AC consumable electrode arc welding control method, in which welding is performed by periodically switching the electrode polarity between a positive electrode polarity period and a negative electrode polarity period while repeating a short circuit period and an arc period between a welding wire and a base material. Background Art

[0002] An AC consumable electrode arc welding method is conventionally used in which welding is performed by periodically switching electrode polarity to an electrode positive polarity period and an electrode negative polarity period including a plurality of cycles of short circuit periods and arc periods (see, for example, Patent Document 1).

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: JP Patent No. 6601870

[0006] In the conventional AC consumable electrode arc welding method, there is a problem that the welding quality deteriorates because the welding state tends to become unstable during the electrode negative polarity period. Summary of the invention

[0007] Therefore, an object of the present invention is to provide an AC consumable electrode arc welding control method that can stabilize the welding state during the electrode negative polarity period and improve the welding quality.

[0008] In order to solve the above-mentioned problems, the invention of technical solution 1 is an AC consumable electrode arc welding control method, in which a short circuit period and an arc period are repeated between the welding wire and the base material, the welding wire is fed reversely during the short circuit period and fed forwardly during the arc period, and the electrode polarity is periodically switched to an electrode positive polarity period and an electrode negative polarity period including at least one of the arc periods for welding. In the AC consumable electrode arc welding control method, the absolute value of the peak value of the forward feed and the absolute value of the peak value of the reverse feed are set to a larger value during the electrode negative polarity period than those during the electrode positive polarity period.

[0009] The invention of technical solution 2 is based on the AC consumable electrode arc welding control method recorded in technical solution 1, and is characterized in that the switching period from the peak of the reverse feed to the peak of the forward feed and the switching period from the peak of the forward feed to the peak of the reverse feed are set to be shorter periods in the electrode negative polarity period than in the electrode positive polarity period.

[0010] The invention of claim 3 is the AC consumable electrode arc welding control method according to claim 1 or 2, wherein the average value of the feeding speed of the welding wire is set to a larger value during the electrode negative polarity period than during the electrode positive polarity period.

[0011] The invention of technical solution 4 is based on the AC consumable electrode arc welding control method recorded in technical solution 1 or 2. During the positive polarity period of the electrode, the output is controlled by constant voltage control during at least a part of the arc period, and during the negative polarity period of the electrode, the output is controlled by constant current control during the entire arc period.

[0012] The invention of technical solution 5 is based on the AC consumable electrode arc welding control method recorded in technical solution 1 or 2, wherein the arc period is formed by a first arc period, a second arc period and a third arc period, and the welding current in the first arc period rises obliquely from a low-level current value, and the inclined rising rate in the electrode negative polarity period is set to a smaller value than that in the electrode positive polarity period.

[0013] The invention of technical solution 6 is based on the AC consumable electrode arc welding control method recorded in technical solution 1 or 2, wherein the arc period is formed by a first arc period, a second arc period and a third arc period, and the maximum value of the welding current in the first arc period is set to a smaller value in the electrode negative polarity period than in the electrode positive polarity period.

[0014] Effects of the Invention

[0015] According to the AC consumable electrode arc welding control method according to the present invention, the welding state during the electrode negative polarity period can be stabilized to improve the welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a block diagram of a welding power source for implementing the AC consumable electrode arc welding control method according to the embodiment of the present invention.

[0017] Figure 2 The present invention is a method for controlling AC consumable electrode arc welding according to an embodiment of the present invention. Figure 1 Timing diagram of each signal in the welding power supply.

[0018] Explanation of symbols

[0019] 1 welding wire

[0020] 2. Base material

[0021] 3 Arc

[0022] 4 welding torch

[0023] 5 Feed rollers

[0024] CM Current Comparison Circuit

[0025] Cm current comparison signal

[0026] Ea error amplification signal

[0027] EI current error amplifier circuit

[0028] Ei current error amplified signal

[0029] EV voltage error amplifier circuit

[0030] Ev voltage error amplification signal

[0031] FC feed control circuit

[0032] Fc feed control signal

[0033] FR feed speed setting circuit

[0034] Fr feed speed setting signal

[0035] Fw feed speed

[0036] IA1R 1st arc current setting circuit

[0037] Ia1r 1st arc current setting signal

[0038] IA2R electrode negative polarity second arc current setting circuit

[0039] Ia2r electrode negative polarity second arc current setting signal

[0040] IA3R 3rd arc current setting circuit

[0041] Ia3r 3rd arc current setting signal

[0042] ICR current control setting circuit

[0043] Icr current control setting signal

[0044] ID current detection circuit

[0045] Id current detection signal

[0046] ILR low level current setting circuit

[0047] I1r low level current setting signal

[0048] Iw welding current

[0049] ND Neck Detection Circuit

[0050] Nd necking detection signal

[0051] PM power supply main circuit

[0052] SD short circuit detection circuit

[0053] Sd short circuit detection signal

[0054] SNR electrode negative polarity rise rate setting circuit

[0055] Snr electrode negative polarity rising rate setting signal

[0056] SPN Polarity Switching Circuit

[0057] Spn polarity switching signal

[0058] SPR electrode positive polarity rise rate setting circuit

[0059] Spr electrode positive polarity rising rate setting signal

[0060] SR rise rate setting circuit

[0061] Sr Rise rate setting signal

[0062] Sta1 1st arc period signal

[0063] STA3 3rd arc period circuit

[0064] Sta3 3rd arc period signal

[0065] SW power supply characteristic switching circuit

[0066] Tc delay period

[0067] Td Current fall time

[0068] TDR current fall time setting circuit

[0069] Tdr Current fall time setting signal

[0070] TNR electrode negative polarity period setting circuit

[0071] Tnr electrode negative polarity period setting signal

[0072] TPR electrode positive polarity period setting circuit

[0073] Tpr electrode positive polarity period setting signal

[0074] Trd Reverse feed deceleration period

[0075] TRDR Reverse feed deceleration period setting circuit

[0076] Trdr Reverse feed deceleration period setting signal

[0077] Trp Reverse feed peak period

[0078] Tru reverse feed acceleration period

[0079] TRUR reverse feed acceleration period setting circuit

[0080] Trur reverse feed acceleration period setting signal

[0081] Tsd Forward feed deceleration period

[0082] TSDR Forward feed deceleration period setting circuit

[0083] Tsdr Forward feed deceleration period setting signal

[0084] Tsp Forward feed peak period

[0085] Tsu Forward feed acceleration period

[0086] TSUR Forward feed acceleration period setting circuit

[0087] Tsur Forward feed acceleration period setting signal

[0088] VD voltage detection circuit

[0089] Vd voltage detection signal

[0090] VR voltage setting circuit

[0091] Vr voltage setting signal

[0092] Vw welding voltage

[0093] WM Feed Motor

[0094] Wrp reverse feed peak value

[0095] WRR reverse feed peak setting circuit

[0096] Wrr Reverse feed peak setting signal

[0097] Wsp forward feed peak value

[0098] WSR forward feed peak setting circuit

[0099] Wsr Forward feed peak setting signal. DETAILED DESCRIPTION

[0100] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0101] Figure 1This is a block diagram of a welding power source for implementing the AC consumable electrode arc welding control method according to the embodiment of the present invention.

[0102] The power main circuit PM receives a 3-phase 200V or other commercial power supply (not shown), and receives an error amplification signal Ea and a polarity switching signal Spn as inputs. The primary side inverter circuit performs output control based on the error amplification signal Ea, and the secondary side inverter circuit switches the electrode polarity to the electrode positive polarity EP and the electrode negative polarity EN based on the polarity switching signal Sw to output an AC welding voltage Vw and a welding current Iw. Although not shown, the power main circuit PM includes: a primary rectifier that rectifies the commercial power supply; a smoothing capacitor that smoothes the rectified DC; a primary side inverter circuit that converts the smoothed DC into a high-frequency AC and is driven by the error amplification signal Ea; a high-frequency transformer that steps down the high-frequency AC to a voltage value suitable for welding; a secondary rectifier that rectifies the stepped-down high-frequency AC into DC; a reactor that smoothes the rectified DC; and a secondary side inverter circuit that converts the smoothed DC into AC and outputs it, driven by the polarity switching signal Spn.

[0103] The feed motor WM receives the feed control signal Fc described later as an input, alternately repeats forward feeding and reverse feeding, and feeds the welding wire 1 at a feed speed Fw. A motor with fast transient response is used for the feed motor WM. In order to increase the rate of change of the feed speed Fw of the welding wire 1 and the reversal of the feed direction, the feed motor WM is sometimes provided near the front end of the welding torch 4. In addition, two feed motors WM are sometimes used to make a push-pull feeding system.

[0104] The welding wire 1 is fed into the welding torch 4 by the rotation of the feed roller 5 coupled to the feed motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. An alternating welding voltage Vw is applied between the power supply nozzle (not shown) in the welding torch 4 and the base material 2, and an alternating welding current Iw is passed. A shielding gas (not shown) is ejected from the front end of the welding torch 4. As the shielding gas, carbon dioxide gas, a mixed gas of carbon dioxide gas and argon gas, a mixed gas of oxygen and argon gas, etc. are used.

[0105] The voltage setting circuit VR outputs a predetermined voltage setting signal Vr for setting the welding voltage Vw in the second arc period in the electrode positive polarity period. The voltage detection circuit VD detects the above-mentioned welding voltage Vw and converts it into an absolute value, and outputs a voltage detection signal Vd. The short-circuit determination circuit SD takes the above-mentioned voltage detection signal Vd as input, and when the value is less than a predetermined short-circuit determination value (about 10V), it determines that it is in the short-circuit period and outputs a short-circuit determination signal Sd of a high level. When the value is greater than a predetermined short-circuit determination value (about 10V), it determines that it is in the arc period and outputs a short-circuit determination signal Sd of a low level.

[0106] The voltage error amplifier circuit EV receives the voltage setting signal Vr and the voltage detection signal Vd as inputs, amplifies the error between the two values, and outputs a voltage error amplified signal Ev.

[0107] The current detection circuit ID detects the welding current Iw described above, converts it into an absolute value, and outputs a current detection signal Id.

[0108] The forward feed acceleration period setting circuit TSUR takes the polarity switching signal Spn described later as input, and when the polarity switching signal Spn is at a high level (electrode positive polarity period), the output becomes the forward feed acceleration period setting signal Tsur of the predetermined electrode positive polarity forward feed acceleration period, and when the polarity switching signal Spn is at a low level (electrode negative polarity period), the output becomes the forward feed acceleration period setting signal Tsur of the predetermined electrode negative polarity forward feed acceleration period. Here, the electrode negative polarity forward feed acceleration period is set to a period shorter than the electrode positive polarity forward feed acceleration period.

[0109] The forward feed deceleration period setting circuit TSDR takes the polarity switching signal Spn described later as an input, and when the polarity switching signal Spn is at a high level (electrode positive polarity period), the output becomes the forward feed deceleration period setting signal Tsdr of the predetermined electrode positive polarity forward feed deceleration period, and when the polarity switching signal Spn is at a low level (electrode negative polarity period), the output becomes the forward feed deceleration period setting signal Tsdr of the predetermined electrode negative polarity forward feed deceleration period. Here, the electrode negative polarity forward feed deceleration period is set to a period shorter than the electrode positive polarity forward feed deceleration period.

[0110] The reverse feed acceleration period setting circuit TRUR takes the polarity switching signal Spn described later as input, and when the polarity switching signal Spn is at a high level (electrode positive polarity period), the output becomes the reverse feed acceleration period setting signal Trur of the predetermined electrode positive polarity reverse feed acceleration period, and when the polarity switching signal Spn is at a low level (electrode negative polarity period), the output becomes the reverse feed acceleration period setting signal Trur of the predetermined electrode negative polarity reverse feed acceleration period. Here, the electrode negative polarity reverse feed acceleration period is set to a period shorter than the electrode positive polarity reverse feed acceleration period.

[0111] The reverse feed deceleration period setting circuit TRDR takes the polarity switching signal Spn described later as input, and when the polarity switching signal Spn is at a high level (electrode positive polarity period), the output becomes the reverse feed deceleration period setting signal Trdr of the predetermined electrode positive polarity reverse feed deceleration period, and when the polarity switching signal Spn is at a low level (electrode negative polarity period), the output becomes the reverse feed deceleration period setting signal Trdr of the predetermined electrode negative polarity reverse feed deceleration period. Here, the electrode negative polarity reverse feed deceleration period is set to a period shorter than the electrode positive polarity reverse feed deceleration period.

[0112] The forward feed peak setting circuit WSR takes the polarity switching signal Spn described later as an input, and when the polarity switching signal Spn is at a high level (during the electrode positive polarity), the output becomes a forward feed peak setting signal Wsr of a predetermined electrode positive polarity forward feed peak, and when the polarity switching signal Spn is at a low level (during the electrode negative polarity), the output becomes a forward feed peak setting signal Wsr of a predetermined electrode negative polarity forward feed peak. Here, the absolute value of the electrode negative polarity forward feed peak is set to a value greater than the absolute value of the electrode positive polarity forward feed peak.

[0113] The reverse feed peak setting circuit WRR takes the polarity switching signal Spn described later as an input, and when the polarity switching signal Spn is at a high level (during the electrode positive polarity), the output becomes the reverse feed peak setting signal Wrr of the predetermined electrode positive polarity reverse feed peak, and when the polarity switching signal Spn is at a low level (during the electrode negative polarity), the output becomes the reverse feed peak setting signal Wrr of the predetermined electrode negative polarity reverse feed peak. Here, the absolute value of the electrode negative polarity reverse feed peak is set to a value greater than the absolute value of the electrode positive polarity reverse feed peak.

[0114] The feed speed setting circuit FR takes the above-mentioned forward feed acceleration period setting signal Tsur, the above-mentioned forward feed deceleration period setting signal Tsdr, the above-mentioned reverse feed acceleration period setting signal Trur, the above-mentioned reverse feed deceleration period setting signal Trdr, the above-mentioned forward feed peak value setting signal Wsr, the above-mentioned reverse feed peak value setting signal Wrr and the above-mentioned short-circuit determination signal Sd as inputs, and outputs a feed speed pattern generated by the following processing as a feed speed setting signal Fr. When the feed speed setting signal Fr is 0 or more, it becomes a forward feed period, and when it is less than 0, it becomes a reverse feed period.

[0115] 1) During the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur, a feed speed setting signal Fr is output for accelerating from 0 to a positive forward feed peak value Wsp determined by the forward feed peak value setting signal Wsr.

[0116] 2) Next, during the forward feed peak period Tsp, the feed speed setting signal Fr is output for maintaining the forward feed peak value Wsp described above.

[0117] 3) If the short-circuit detection signal Sd changes from a low level (arc period) to a high level (short-circuit period), it shifts to the forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr, and outputs a feed speed setting signal Fr that decelerates from the above-mentioned forward feed peak value Wsp to 0.

[0118] 4) Next, during the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur, the feed speed setting signal Fr is outputted to accelerate from 0 to the reverse feed peak value Wrp of a negative value determined by the reverse feed peak value setting signal Wrr.

[0119] 5) Next, during the reverse feed peak period Trp, the feed speed setting signal Fr is outputted to maintain the reverse feed peak value Wrp described above.

[0120] 6) If the short-circuit detection signal Sd changes from a high level (short-circuit period) to a low level (arc period), it shifts to the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr, and outputs a feed speed setting signal Fr that decelerates from the above-mentioned reverse feed peak value Wrp to 0.

[0121] 7) By repeating the above steps 1) to 6), a feed speed setting signal Fr is generated in a feed pattern that changes in a positive and negative trapezoidal wave shape.

[0122] The feed control circuit FC takes the above-mentioned feed speed setting signal Fr as an input, and outputs a feed control signal Fc for feeding the welding wire 1 at a feed speed Fw equivalent to the value of the feed speed setting signal Fr to the above-mentioned feed motor WM.

[0123] The necking detection circuit ND takes the above-mentioned short-circuit discrimination signal Sd, the above-mentioned voltage detection signal Vd, and the above-mentioned current detection signal Id as inputs. When the voltage rise value of the voltage detection signal Vd during the period when the short-circuit discrimination signal Sd is at a high level (during short circuit) reaches the reference value, it is determined that the formation state of necking becomes the reference state, and a necking detection signal Nd at a high level is output. When the short-circuit discrimination signal Sd changes to a low level (during arc), a necking detection signal Nd at a low level is output. In addition, the necking detection signal Nd can also be changed to a high level at the time point when the differential value of the voltage detection signal Vd during the short-circuit period reaches the corresponding reference value. Furthermore, the resistance value of the molten droplet can be calculated by dividing the value of the voltage detection signal Vd by the value of the current detection signal Id, and the necking detection signal Nd can be changed to a high level at the time point when the differential value of this resistance value reaches the corresponding reference value.

[0124] The low-level current setting circuit ILR outputs a predetermined low-level current setting signal I1r. The current comparison circuit CM takes this low-level current setting signal I1r and the above-mentioned current detection signal Id as inputs. When Id < I1r, a current comparison signal Cm at a high level is output. When Id ≥ I1r, a current comparison signal Cm at a low level is output.

[0125] The first arc current setting circuit IA1R takes the polarity switching signal Spn described later as an input. When the polarity switching signal Spn is at a high level, it outputs a first arc current setting signal Ia1r with a predetermined electrode positive polarity first arc current value. When the polarity switching signal Spn is at a low level, it outputs a first arc current setting signal Ia1r with a predetermined electrode negative polarity first arc current value. Here, the electrode positive polarity first arc current value > the electrode negative polarity first arc current value.

[0126] The electrode negative polarity second arc current setting circuit IA2R outputs a predetermined electrode negative polarity second arc current setting signal Ia2r. The electrode negative polarity second arc current setting signal Ia2r becomes a value that decreases with time during the second arc period during the electrode negative polarity period.

[0127] The current fall time setting circuit TDR takes the above-mentioned first arc current setting signal Ia1r and the polarity switching signal Spn described later as input, and when the polarity switching signal Spn is at a high level, the output becomes the current fall time setting signal Tdr of the predetermined electrode positive polarity current fall time, and when the polarity switching signal Spn is at a low level, the output becomes the current fall time setting signal Tdr of the electrode negative polarity current fall time that changes according to the electrode negative polarity first arc current value of the first arc current setting signal Ia1r.

[0128] The third arc period circuit STA3 takes the above-mentioned short-circuit determination signal Sd and the above-mentioned current fall time setting signal Tdr as inputs, and outputs the third arc period signal Sta3 which becomes a high level at the time point when the short-circuit determination signal Sd changes to a low level (arc period) and the current fall time Td determined by the current fall time setting signal Tdr has passed. If the short-circuit determination signal Sd becomes a high level (short-circuit period) thereafter, the third arc period signal Sta3 which becomes a low level is output.

[0129] The third arc current setting circuit IA3R outputs a predetermined third arc current setting signal Ia3r.

[0130] The electrode positive polarity rise rate setting circuit SPR outputs a predetermined electrode positive polarity rise rate setting signal Spr [A / ms]. The electrode negative polarity rise rate setting circuit SNR takes the above-mentioned first arc current setting signal Ia1r as input and outputs an electrode negative polarity rise rate setting signal Snr [A / ms] calculated by a predetermined rise rate setting function.

[0131] 1) Snr <Spr。

[0132] 2) Snr is 50% or less of Spr, more preferably 30% or less.

[0133] 3) Snr is set to a range of 50 to 500 A / ms, more preferably 50 to 200 A / ms.

[0134] 4) Snr is a function of Ia1r, and the larger Ia1r is, the smaller Snr is. For example, when the function changes Ia1r in the range of 300 to 400 A, Snr when Ia1r=400 is set to a value 20% smaller than when Ia1r=300.

[0135] The rise rate setting circuit SR takes the above-mentioned electrode positive polarity rise rate setting signal Spr, the above-mentioned electrode negative polarity rise rate setting signal Snr and the polarity switching signal Spn described later as inputs, and when the polarity switching signal Spn is at a high level, the electrode positive polarity rise rate setting signal Spr is output as the rise rate setting signal Sr, and when the polarity switching signal Spn is at a low level, the electrode negative polarity rise rate setting signal Snr is output as the rise rate setting signal Sr.

[0136] The electrode positive polarity period setting circuit TPR outputs a predetermined electrode positive polarity period setting signal Tpr. The electrode negative polarity period setting circuit TNR outputs a predetermined electrode negative polarity period setting signal Tnr.

[0137] The polarity switching circuit SPN receives the electrode positive polarity period setting signal Tpr, the electrode negative polarity period setting signal Tnr, and the short circuit determination signal Sd as inputs, performs the following processing, and outputs a polarity switching signal Spn.

[0138] 1) If the period determined by the electrode positive polarity period setting signal Tpr has passed since the polarity switching signal Spn changed to a high level, and then the short circuit determination signal Sd becomes a high level (short circuit period), the polarity switching signal Spn is changed to a low level (electrode negative polarity period) and output.

[0139] 2) If the period determined by the electrode negative polarity period setting signal Tnr has passed since the polarity switching signal Spn changed to a low level, and then the short circuit detection signal Sd becomes a high level (short circuit period), the polarity switching signal Spn is changed to a high level (electrode positive polarity period) and output.

[0140] The current control setting circuit ICR takes the above-mentioned short-circuit judgment signal Sd, the above-mentioned low-level current setting signal I1r, the above-mentioned necking detection signal Nd, the above-mentioned third arc period signal Sta3, the above-mentioned first arc current setting signal Ia1r, the above-mentioned third arc current setting signal Ia3r, the above-mentioned rise rate setting signal Sr and the above-mentioned electrode negative polarity second arc current setting signal Ia2r as input, performs the following processing, and outputs the current control setting signal Icr and the first arc period signal Sta1.

[0141] 1) During a predetermined delay period Tc from the time when the short-circuit determination signal Sd changes to a low level (arc period), a current control setting signal Icr having a value equal to the low-level current setting signal I1r is output.

[0142] 2) When the delay period Tc ends, the current control setting signal Icr is outputted, which increases from the value of the low-level current setting signal I1r to the value of the first arc current setting signal Ia1r at a rising rate determined by the rising rate setting signal Sr. This period becomes the first arc period Ta1, and the first arc period signal Sta1 is outputted at a high level.

[0143] 3) Thereafter, in the second arc period Ta2 until the third arc period signal Sta3 becomes high level, the current control setting signal Icr which becomes the electrode negative polarity second arc current setting signal Ia2r is output.

[0144] 4) Thereafter, in the third arc period Ta3 until the short circuit determination signal Sd changes to the low level (arc period), the current control setting signal Icr, which becomes the third arc current setting signal Ia3r, is output.

[0145] 5) If the short-circuit detection signal Sd changes to a high level (during the short-circuit period), the output becomes a predetermined initial current setting value in a predetermined initial period, and then rises to a predetermined short-circuit peak setting value with a predetermined short-circuit slope and maintains the current control setting signal Icr at this value.

[0146] 6) Thereafter, when the constriction detection signal Nd changes to a high level, the current control setting signal Icr having the value of the low-level current setting signal I1r is output.

[0147] The current error amplifier circuit EI receives the current control setting signal Icr and the current detection signal Id as inputs, amplifies the error between the two values, and outputs a current error amplified signal Ei.

[0148] 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, the above-mentioned third arc period signal Sta3 and the above-mentioned polarity switching signal Spn as input, performs the following processing, and outputs the error amplification signal Ea.

[0149] 1) When the polarity switching signal Spn is at a high level (electrode positive polarity EP), and in the second arc period Ta2 in the electrode positive polarity period until the first arc period signal Sta1 changes to a low level and 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.

[0150] 2) During the other periods, the current error amplification signal Ei is output as the error amplification signal Ea.

[0151] With this circuit, the characteristics of the welding power source become constant current characteristics in the short circuit period, the delay period, the first arc period Ta1, the second arc period Ta2 in the electrode negative polarity period, and the third arc period Ta3, and become constant voltage characteristics in the second arc period Ta2 in the electrode positive polarity period. Therefore, in the electrode positive polarity period, the output is controlled by constant voltage control during at least a part of the arc period, and in the electrode negative polarity period, the output is controlled by constant current control during the entire arc period.

[0152] Figure 2 The present invention is a method for controlling AC consumable electrode arc welding according to an embodiment of the present invention. Figure 1 The timing diagram of each signal in the welding power supply is shown in FIG. (A) of the figure shows the time change of the feed speed Fw, (B) of the figure shows the time change of the welding current Iw, (C) of the figure shows the time change of the welding voltage Vw, (D) of the figure shows the time change of the short circuit determination signal Sd, (E) of the figure shows the time change of the first arc period signal Sta1, (F) of the figure shows the time change of the third arc period signal Sta3, (G) of the figure shows the time change of the polarity switching signal Spn, and (H) of the figure shows the time change of the necking detection signal Nd. The operation of each signal will be described below with reference to the figure.

[0153] The upper side of the feed speed Fw shown in (A) of the figure is a forward feed period in which the welding wire is fed toward the base material, and the lower side is a reverse feed period in which the welding wire is fed away from the base material. The upper side of the welding current Iw shown in (B) of the figure and the welding voltage Vw shown in (C) of the figure represent the electrode positive polarity EP and the lower side represent the electrode negative polarity EN. The values ​​of the feed speed Fw, welding current Iw and welding voltage Vw represent the values ​​of their absolute values. For example, the value becomes larger when the feed speed Fw is in the reverse feed state, which means that the absolute value becomes larger. Similarly, the value becomes larger when the welding current Iw and the welding voltage Vw are in the electrode negative polarity period Ten, which means that the absolute value becomes larger. Controlled by the polarity switching signal Spn shown in (G) of the figure Figure 1 The secondary-side inverter circuit in the power supply main circuit PM becomes the electrode positive polarity period Tep when the level is high, and becomes the electrode negative polarity period Ten when the level is low.

[0154] In this figure, the electrode positive polarity period Tep is a period from time t1 to t4, and the electrode negative polarity period Ten is a period from time t4 to t7. Figure 1 The period is the period of time until the short circuit occurs, plus the value of the electrode positive polarity period setting signal Tpr. The electrode negative polarity period Ten becomes Figure 1The period is the value of the electrode negative polarity period setting signal Tnr added to the period until the short circuit occurs. Since the frequency of the AC is set to 0.1-30 Hz and the duty cycle is set to a range of about 20-80%, the electrode positive polarity period Tep and the electrode negative polarity period Ten are set to a range of about 7ms-8 seconds. Each period includes at least one arc period. For example, when the frequency of the AC is 10 Hz and the duty cycle is 50%, Tep=50ms and Ten=50ms. At this time, since the period of the short circuit / arc period is about 10ms, each period includes 5 cycles of short circuit / arc periods.

[0155] (1) Tep action during electrode positive polarity

[0156] At time t0, which is the short-circuit period of the electrode negative polarity period Ten, as shown in (G) of the figure, the polarity switching signal Spn becomes low level. As shown in (A) of the figure, the feed speed Fw is in the state of the electrode negative polarity reverse feed peak. As shown in (B) of the figure, the welding current IW is in the state of the initial current value of the negative value. As shown in (C) of the figure, the welding voltage Vw is in the state of the short-circuit voltage value of several V of the negative value. As shown in (D) of the figure, the short-circuit determination signal Sd is in the state of the high level (short-circuit period).

[0157] At time t1, as shown in (G) of the figure, if the polarity switching signal Spn changes to a high level, the transition to the electrode positive polarity period Tep occurs. In response to this, as shown in (A) of the figure, the feed speed Fw is accelerated toward the electrode positive polarity reverse feed peak. As shown in (B) of the figure, the welding current Iw is controlled by a constant current during the short circuit period and changes to a positive initial current value. As shown in (C) of the figure, the welding voltage Vw changes to a positive short circuit voltage value. The timing at which the polarity switching signal Spn changes to a high level at time t1 is during the short circuit period, which is a time point immediately after the short circuit occurs or after a predetermined period (about 1 ms) has passed.

[0158] Afterwards, when the predetermined initial period ends, as shown in (B) of the figure, the welding current Iw rises at a predetermined short-circuit slope, and when it reaches the short-circuit peak, the value is maintained. As shown in (C) of the figure, the welding voltage Vw rises from near the peak value of the welding current Iw when it becomes short-circuit. This is because, due to the reverse feeding of the welding wire 1 and the pinching force caused by the welding current Iw, the molten droplet at the front end of the welding wire 1 gradually forms a neck. If the voltage rise value of the welding voltage Vw reaches the reference value thereafter, it is determined that the neck formation state becomes the reference state, and as shown in (H) of the figure, the neck detection signal Nd changes to a high level. In response to this, Figure 1The current control setting signal Icr is reduced to the value of the low-level current setting signal I1r. For this reason, as shown in (B) of the figure, the welding current Iw decreases sharply from the peak value during the short circuit to the low-level current value. Then, if the welding current Iw is reduced to the low-level current value, as shown in (B) of the figure, since the current control setting signal Icr keeps the low-level current setting signal I1r unchanged, the welding current Iw maintains the low-level current value from the arc regeneration to the predetermined delay period Tc. In order to make the rapid deceleration rate of the welding current Iw when the necking is detected high, it is desirable to add a circuit in which a resistor and a switch element are connected in parallel in the current path of the welding current Iw. Until the necking is detected, the switch element is set to the on state, the resistor is short-circuited, and the normal state is set. If the necking is detected, the switch element is set to the off state, and the resistor is inserted into the current path, thereby enabling the rapid deceleration rate to be high. For example, the initial period is set to 1 ms, the initial current value is set to 50 A, the short circuit inclination is set to 400 A / ms, the short circuit peak is set to 450 A, and the low level current value is set to 50 A. As shown in (H) of the figure, if an arc is generated again at time t2, the necking detection signal Nd returns to a low level.

[0159] At time t2, if the constriction progresses due to the pinching force caused by the reverse feeding of the welding wire and the conduction of the welding current Iw, thereby generating an arc, the welding voltage Vw increases sharply to an arc voltage value of several tens of V as shown in (C) of the figure. Therefore, as shown in (D) of the figure, the short circuit determination signal Sd changes to a low level (arc period). In response to this, as shown in (A) of the figure, the feed speed Fw starts to switch from the electrode positive polarity reverse feed peak to the electrode positive polarity forward feed peak. The switching period from the electrode positive polarity reverse feed peak to the electrode positive polarity forward feed peak becomes Figure 1 The period of the electrode positive polarity reverse feed deceleration period and the electrode positive polarity forward feed acceleration period are combined. For example, the electrode positive polarity reverse feed period and the electrode positive polarity forward feed acceleration period are set to 1ms. In the predetermined delay period Tc from time t2 to t21, as shown in (B) of the figure, the welding current Iw is maintained at a low level current value by constant current control. As shown in (C) of the figure, the welding voltage Vw becomes the arc voltage value. For example, the electrode positive polarity forward feed peak value is set to 50m / min, and the electrode positive polarity reverse feed peak value is set to -30m / min. In addition, the delay period Tc is set to about 0 to 0.5ms. When Tc=0, the delay period Tc is deleted.

[0160] At time t21, when the delay period Tc ends, the first arc period signal Sta1 changes to a high level as shown in (E) of the figure. In response to this, as shown in (B) of the figure, the welding current Iw changes from a low level current value to a high level current value through constant current control. Figure 1 The electrode positive polarity rise rate setting signal Spr determines the rise rate and rises to Figure 1 The electrode positive polarity first arc current value is determined by the first arc current setting signal Ia1r. At time t22, when the welding current Iw rises to the electrode positive polarity first arc current value, as shown in (E) of the figure, the first arc period signal Sta1 changes to a low level, and the first arc period ends. As shown in (C) of the figure, the welding voltage Vw also rises with a slope. The electrode positive polarity rise rate is set to about 500 to 1000 a / ms, and the electrode positive polarity first arc current value is set to about 400 to 500 A.

[0161] At time t23, if the arc is generated from time t2, Figure 1 The electrode positive polarity current falling time Td determined by the current falling time setting signal Tdr is set, and as shown in (F) of the figure, the third arc period signal Sta3 changes to a high level. The period from time t22 to t23 becomes the second arc period Ta2. In the second arc period Ta2, the arc length is maintained at an appropriate value by constant voltage control. As shown in (B) of the figure, the welding current Iw gradually decreases. As shown in (C) of the figure, the welding voltage Vw is controlled by constant voltage control and gradually decreases. For example, the electrode positive polarity current falling time Td is set to 6ms. The second arc period Ta2 is not a given value but is about 5ms.

[0162] The period from the time t23 when the third arc period signal Sta3 changes to the high level to the time t3 when the short circuit occurs is the third arc period Ta3. In the third arc period Ta3, the welding current Iw is controlled by constant current. As shown in (B) of the figure, Figure 1 The value determined by the third arc current setting signal Ia3r. As shown in (C) of the figure, the welding voltage Vw becomes a value smaller than the second arc period. For example, the third arc current is set to 50A. The third arc period Ta3 is not a given value but becomes about 1ms. By making the welding current Iw a small value, the next short circuit will occur early. If a short circuit occurs at time t3, the short circuit detection signal Sd changes to a high level as shown in (D) of the figure. In response to this, as shown in (A) of the figure, the feed speed Fw begins to switch from the electrode positive polarity forward feed peak to the electrode positive polarity reverse feed peak. The switching period from the electrode positive polarity forward feed peak to the electrode positive polarity reverse feed peak becomes Figure 1The period is the sum of the electrode positive polarity forward feed deceleration period and the electrode positive polarity reverse feed acceleration period. For example, the electrode positive polarity forward feed period and the electrode positive polarity reverse feed acceleration period are set to 1 ms.

[0163] The period from time t3 to time t4 becomes a short circuit period again, and thereafter becomes an arc period. The operation during this period is the same as that described above, and therefore its description will not be repeated.

[0164] (2) Action of Tem during negative electrode polarity

[0165] At time t31 in the middle of the third arc period Ta3 in the electrode positive polarity period Tep, after the time t1 is reached, Figure 1 The period determined by the electrode positive polarity period setting signal Tpr. Then, at time t4, if a short circuit occurs, as shown in (C) of the figure, the welding voltage Vw becomes a short circuit voltage value of a positive value, and as shown in (D) of the figure, the short circuit determination signal Sd changes to a high level. In response to this, as shown in (G) of the figure, the polarity switching signal Spn changes to a low level and shifts to the electrode negative polarity period Ten. In response to this, as shown in (A) of the figure, the feed speed Fw changes from the electrode positive polarity forward feed peak to the electrode negative polarity reverse feed peak. As shown in (B) of the figure, the welding current Iw is controlled by constant current during the short circuit period and changes to a negative initial current value. As shown in (C) of the figure, the welding voltage Vw changes to a negative short circuit voltage value. The timing at which the polarity switching signal Spn switches to the low level at time t4 is during the short-circuit period, that is, a time point immediately after the short-circuit occurs or after a predetermined period (about 1 ms) has passed.

[0166] Afterwards, when the predetermined initial period ends, as shown in (B) of the figure, the welding current Iw rises at a predetermined short-circuit slope, and when it reaches the short-circuit peak, it maintains the value. As shown in (C) of the figure, the welding voltage Vw starts to rise near the peak value of the welding current Iw when it becomes a short-circuit. This is because, due to the reverse feeding of the welding wire 1 and the pinching force caused by the welding current Iw, the molten droplet at the front end of the welding wire 1 gradually forms a neck. If the voltage rise value of the welding voltage Vw reaches the reference value thereafter, it is determined that the neck formation state becomes the reference state, and as shown in (H) of the figure, the neck detection signal Nd changes to a high level. In response to this, Figure 1The current control setting signal Icr decreases to the value of the low-level current setting signal I1r. For this reason, as shown in (B) of the figure, the welding current Iw decreases sharply from the peak value during short circuit to the low-level current value. Then, if the welding current Iw decreases to the low-level current value, as shown in (B) of the figure, since the current control setting signal Icr keeps the low-level current setting signal I1r unchanged, the welding current Iw maintains the low-level current value from the time when the arc is regenerated to the time when the predetermined delay period Tc has passed. The above-mentioned initial period, initial current value, short-circuit inclination, short-circuit peak value and low-level current value can be set to the same value as in the electrode positive polarity period, but can also be set to different values ​​in consideration of the characteristics of the electrode negative polarity. As shown in (H) of the figure, if the arc is generated again at time t5, the necking detection signal Nd returns to the low level.

[0167] At time t5, when the constriction progresses due to the pinching force caused by the reverse feeding of the welding wire and the conduction of the welding current Iw, and an arc is generated, the welding voltage Vw increases sharply to an arc voltage value of several tens of V as shown in (C) of the figure. Therefore, as shown in (D) of the figure, the short circuit determination signal Sd changes to a low level (arc period). In response to this, as shown in (A) of the figure, the feed speed Fw starts to switch from the electrode negative polarity reverse feed peak to the electrode negative polarity forward feed peak. The switching period from the electrode negative polarity reverse feed peak to the electrode negative polarity forward feed peak becomes Figure 1 The period of the electrode negative polarity reverse feed deceleration period and the electrode negative polarity forward feed acceleration period is combined. For example, the electrode negative polarity reverse feed period and the electrode negative polarity forward feed acceleration period are set to 0.5ms. Therefore, the switching period from the reverse feed peak to the forward feed peak is set to be shorter in the electrode negative polarity period than in the electrode positive polarity period. In the predetermined delay period Tc from time t5 to t51, as shown in (B) of the figure, the welding current Iw is maintained at a low level current value by constant current control. As shown in (C) of the figure, the welding voltage Vw becomes the arc voltage value. For example, the electrode negative polarity forward feed peak is set to 80m / min, and the electrode negative polarity reverse feed peak is set to -50m / min. The average value of the feed speed Fw in the electrode negative polarity period Ten becomes a value greater than that in the electrode positive polarity period Tep. This is to make the average values ​​of the welding current Iw in the two periods approximately the same value. In addition, the delay period Tc is set to about 0 to 0.5 ms similarly to the electrode positive polarity period Tep. When Tc=0, the delay period Tc is deleted.

[0168] At time t51, when the delay period Tc ends, the first arc period signal Sta1 changes to a high level as shown in (E) of the figure. In response to this, as shown in (B) of the figure, the welding current Iw changes from a low level current value to a high level current value through constant current control. Figure 1 The electrode negative polarity rising rate setting signal Snr determines the rising rate to rise to Figure 1 The electrode negative polarity first arc current value is determined by the first arc current setting signal Ia1r. At time t52, if the welding current Iw rises to the electrode negative polarity first arc current value, the first arc period signal Sta1 changes to a low level as shown in (E) of the figure, and the first arc period ends. As shown in (C) of the figure, the welding voltage Vw also rises with an inclination. The electrode negative polarity rise rate is set to about 50 to 500 a / ms, and the electrode negative polarity first arc current value is set to about 300 to 400 A, which is a value smaller than the electrode positive polarity first arc current value.

[0169] At time t53, if the arc is generated at time t5, Figure 1 The third arc period signal Sta3 changes to a high level as shown in (F) of the figure. The period from time t52 to t53 becomes the second arc period Ta2. In the second arc period Ta2, unlike the electrode positive polarity period Tep, the electrode negative polarity current falling time Td is determined by the current falling time setting signal Tdr. Figure 1 The electrode negative polarity second arc current setting signal Ia2r is used as the target value for constant current control. As shown in (B) of the figure, the welding current Iw becomes a value about 50A smaller than the electrode negative polarity first arc current value at time t52, and becomes a waveform that decreases with time until time t53. Therefore, the relationship of electrode negative polarity first arc current value>electrode negative polarity second arc current>electrode negative polarity third arc current is formed. As shown in (C) of the figure, the welding voltage Vw also gradually decreases. For example, the electrode negative polarity current drop time Td is set to 5ms. The second arc period Ta2 is not a given value but is about 4ms. Here, the maximum value of the welding current Iw in the first arc period Ta1, that is, the electrode negative polarity first arc current value, is set to a value smaller than the electrode positive polarity first arc current value.

[0170] The period from the time t53 when the third arc period signal Sta3 changes to the high level to the time t6 when the short circuit occurs is the third arc period Ta3. In this third arc period Ta3, constant current control is performed. As shown in (B) of the figure, the welding current Iw is Figure 1The value determined by the third arc current setting signal Ia3r. As shown in (C) of the figure, the welding voltage Vw becomes a value smaller than the second arc period. For example, the third arc current is set to 50A. The third arc period Ta3 is not a given value but becomes about 1ms. As mentioned above, by making the welding current Iw a small value, the next short circuit is generated early. If a short circuit occurs at time t6, the short circuit detection signal Sd changes to a high level as shown in (D) of the figure. In response to this, as shown in (A) of the figure, the feed speed Fw starts to switch from the electrode negative polarity positive feed peak to the electrode negative polarity reverse feed peak. The switching period from the electrode negative polarity positive feed peak to the electrode negative polarity reverse feed peak is Figure 1 The period of the electrode negative polarity forward feed deceleration period and the electrode negative polarity reverse feed acceleration period are combined. For example, the electrode negative polarity forward feed period and the electrode negative polarity reverse feed acceleration period are set to 0.5ms. Therefore, the switching period from the forward feed peak to the reverse feed peak is set to a shorter period in the electrode negative polarity period than in the electrode positive polarity period.

[0171] The period from time t6 to t7 becomes a short circuit period again, and then becomes an arc period. The operation during this period is the same as above, so its description will not be repeated. At time t61 in the middle of the third arc period Ta3, after the time t4 has passed, Figure 1 The period determined by the electrode negative polarity period setting signal Tnr is set. Then, at time t7, if a short circuit occurs, as shown in (C) of the figure, the welding voltage Vw becomes a short circuit voltage value of a negative value, and as shown in (D) of the figure, the short circuit determination signal Sd changes to a high level. In response to this, as shown in (G) of the figure, the polarity switching signal Spn changes to a high level, and the electrode positive polarity period Tep starts. The operation after this is the same as that after time t1.

[0172] In this figure, the rise of welding current Iw from time t21 to t22 and time t41 to t42 is shown as a straight line, but it also includes the case of a curve rise. The magnitude of the rise rate in this case is compared with the maximum rise rate of the curve. The so-called curve means that there are cases where the rise rate decreases with time and cases where it increases with time.

[0173] Hereinafter, the effects of this embodiment will be described.

[0174] According to the present embodiment, the absolute value of the peak value of the forward feed and the absolute value of the peak value of the reverse feed are set to be larger values ​​during the electrode negative polarity period than during the electrode positive polarity period. Since the melting speed of the welding wire is greater during the electrode negative polarity period than during the electrode positive polarity period, the arc length becomes longer and the arc period tends to become longer. If the arc period becomes longer, a short circuit occurs when the molten droplet at the front end of the welding wire grows larger, so the welding state becomes unstable and more spatter is generated. In the present embodiment, the absolute value of the peak value of the forward feed and the absolute value of the peak value of the reverse feed are set to be larger values ​​during the electrode negative polarity period than during the electrode positive polarity period. In this way, since the forward feed peak value during the arc period during the electrode negative polarity period becomes larger, the arc period can be shortened. As a result, since a short circuit can be generated before the molten droplet grows larger, it is possible to suppress the welding state from becoming unstable.

[0175] More preferably, according to the present embodiment, the switching period from the reverse feed peak to the forward feed peak and the switching period from the forward feed peak to the reverse feed peak are set to be shorter in the electrode negative polarity period than in the electrode positive polarity period. In this way, since the switching period from the reverse feed peak to the forward feed peak is shorter in the electrode negative polarity period than in the electrode positive polarity period, the feed speed quickly reaches the forward feed peak after the arc is generated. As a result, since the arc period in the electrode negative polarity period can be shortened, the welding state can be further suppressed from becoming unstable.

[0176] More preferably, according to this embodiment, the average value of the feeding speed of the welding wire is set to a larger value during the electrode negative polarity period than during the electrode positive polarity period. In this way, the average value of the welding current can be set to substantially the same value during the electrode negative polarity period and during the electrode positive polarity period. As a result, the appearance of the weld bead can be improved.

[0177] Further preferably, according to the present embodiment, during the electrode positive polarity period, the output is controlled by constant voltage control for at least a portion of the arc period, and during the electrode negative polarity period, the output is controlled by constant current control for the entire arc period. During the electrode positive polarity period, the arc length can be detected by the value of the welding voltage during the arc period. Therefore, during the electrode positive polarity period, the arc length is controlled to an appropriate value by constant voltage control during a portion of the arc period (the second arc period), and the welding state can be maintained stable. However, during the electrode negative polarity period, the arc length cannot be detected by the value of the welding voltage during the arc period. This is because the position of the cathode point formed at the front end of the welding wire during the electrode negative polarity period is unstable and moves, so the proportional relationship between the welding voltage and the arc length is unbalanced. Therefore, even if the arc length is maintained to an appropriate value by constant voltage control during a portion of the arc period during the electrode negative polarity period as in the electrode positive polarity period, the arc length cannot be detected by the value of the welding voltage, and the welding state becomes unstable instead. Therefore, in the present embodiment, during the electrode positive polarity period, the arc length is maintained at an appropriate value by performing constant voltage control during at least a portion of the arc period, thereby stabilizing the welding state. Furthermore, in the present embodiment, during the electrode negative polarity period, constant current control is performed during the entire arc period, thereby suppressing the welding state from becoming unstable due to low voltage control. As a result, in the present embodiment, the welding state during the electrode negative polarity period can be stabilized, thereby improving the welding quality.

[0178] Further preferably, according to the present embodiment, the arc period is formed by the first arc period, the second arc period, and the third arc period, and the welding current in the first arc period rises with an inclination from a low-level current value, and the inclination rise rate is set to a smaller value in the electrode negative polarity period than in the electrode positive polarity period. In the electrode positive polarity period, the welding current is rapidly increased to the first arc current value by setting the rise rate to a large value. Thus, sufficient heat input to the base material can be ensured, and the melting of the welding wire is promoted to form a suitable droplet. In the electrode negative polarity period, compared with the electrode positive polarity period, due to the difference in arc characteristics, the melting speed of the welding wire becomes larger even when the same welding current is energized. Therefore, if the rise rate in the electrode negative polarity period is set to the same value as that in the electrode positive polarity period, the melting of the welding wire is rapidly promoted, the droplet grows rapidly, and more sputtering is generated. Therefore, by setting the increase rate in the electrode negative polarity period to a value smaller than that in the electrode positive polarity period, the melting rate of the welding wire can be made gentle, thereby easing the growth of the droplet. As a result, in this embodiment, the generation of spatter can be suppressed and the welding state can be stabilized.

[0179] Further preferably, according to the present embodiment, the arc period is formed by the first arc period, the second arc period, and the third arc period, and the maximum value of the welding current in the first arc period (the first arc current value) is set to a smaller value in the electrode negative polarity period than in the electrode positive polarity period. In the electrode positive polarity period, by setting the first arc current value to a large value, sufficient heat input to the base material can be ensured, and the melting of the welding wire can be promoted to form a suitable droplet. In the electrode negative polarity period, due to the difference in arc characteristics, the melting speed of the welding wire becomes larger than that in the electrode positive polarity period, even if the same welding current is energized. For this reason, if the first arc current value in the electrode negative polarity period is set to the same value as that in the electrode positive polarity period, the melting of the welding wire is rapidly promoted and the droplet grows rapidly, and more sputtering is generated. Therefore, by setting the first arc current value in the electrode negative polarity period to a smaller value than that in the electrode positive polarity period, the melting speed of the welding wire can be slowed down, thereby easing the growth of the droplet. As a result, in the present embodiment, the occurrence of sputtering can be suppressed and the welding state can be stabilized.

[0180] More preferably, according to this embodiment, the rate of increase of the welding current in the first arc period is set to 50% or less of that in the electrode positive polarity period during the electrode negative polarity period. More preferably, it is set to 30% or less. In this way, the melting speed of the welding wire in the electrode negative polarity period can be optimized, and a stable molten droplet can be formed. As a result, the generation of spatter can be reduced, and the welding state can be further stabilized.

[0181] More preferably, according to this embodiment, the rate of increase during the electrode negative polarity period is set to a range of 50 to 500 A / ms. More preferably, it is set to a range of 50 to 200 A / ms. In this way, the melting speed of the welding wire during the electrode negative polarity period can be optimized, and a stable molten droplet can be formed. As a result, the generation of spatter can be reduced, and the welding state can be further stabilized.

[0182] More preferably, according to the present embodiment, the larger the first arc current value is, the smaller the rise rate during the electrode negative polarity period is set. The larger the average value of the welding current is, the larger the first arc current value is set within the range of about 300 to 400A in consideration of the heat input to the base material. If the rise rate is set to the same value even if the setting of the first arc current value during the electrode negative polarity period is increased, the molten droplet grows excessively and sputtering occurs. In order to suppress this, the larger the first arc current value is, the smaller the rise rate is. As a result, even if the first arc current value is increased, the generation of sputtering can be suppressed.

Claims

1. A method for controlling AC consumable electrode arc welding, During repeated short circuits and arcing between the welding wire and the base material, The welding wire is fed in reverse during the short circuit period and fed in forward during the arc period, The electrode polarity is periodically switched to an electrode positive polarity period and an electrode negative polarity period including at least one of the arc periods to perform welding, The AC consumable electrode arc welding control method is characterized in that: The absolute value of the peak value of the forward feed and the absolute value of the peak value of the reverse feed are set to be larger in the electrode negative polarity period than in the electrode positive polarity period.

2. The AC consumable electrode arc welding control method according to claim 1, characterized in that: A switching period from the peak of the reverse feed to the peak of the forward feed and a switching period from the peak of the forward feed to the peak of the reverse feed are set to be shorter in the electrode negative polarity period than in the electrode positive polarity period.

3. The AC consumable electrode arc welding control method according to claim 1 or 2, characterized in that: The average value of the feeding speed of the welding wire is set to a larger value during the electrode negative polarity period than during the electrode positive polarity period.

4. The AC consumable electrode arc welding control method according to claim 1 or 2, characterized in that: During the electrode positive polarity period, the output is controlled by constant voltage control during at least a portion of the arc period, In the electrode negative polarity period, the output is controlled by constant current control throughout the arc period.

5. The AC consumable electrode arc welding control method according to claim 1 or 2, characterized in that: The arc period is formed by a first arc period, a second arc period, and a third arc period. The welding current in the first arc period increases with a slope from a low level current value. The rising rate of the slope is set to a smaller value in the electrode negative polarity period than in the electrode positive polarity period.

6. The AC consumable electrode arc welding control method according to claim 1 or 2, characterized in that: The arc period is formed by a first arc period, a second arc period, and a third arc period. The maximum value of the welding current in the first arc period is set to a smaller value in the electrode negative polarity period than in the electrode positive polarity period.

Images