Arc welding method

Abstract

In an arc welding method for welding by alternately switching between pulse arc welding with forward feeding and short-circuit transfer arc welding with forward and reverse feeding, the welding wire is fed with high precision. Welding is performed by alternately switching between the following periods: a pulse arc welding period in which the welding wire is forward fed by the forward feeding rotation of the push-side feeding motor and the forward feeding rotation of the pull-side feeding motor, and the peak current and the base current are connected to perform pulse arc welding; and a short-circuit transfer arc welding period in which the welding wire is forward and reverse fed by the forward feeding rotation of the push-side feeding motor and the forward and reverse feeding rotation of the pull-side feeding motor, and the short-circuit current and the arc current are connected to perform short-circuit transfer arc welding. During the short-circuit transfer arc welding period, the forward feed peak value (Wsp) and / or the reverse feed peak value (Wrp) of the pull feed speed (Fw) is corrected and controlled based on the wire storage capacity of the intermediate welding wire storage section.

Description

Technical Field

[0001] The present disclosure relates to an arc welding method for performing welding by alternately switching between a pulse arc welding period and a short-circuit transition arc welding period. Background Art

[0002] Conventionally, the following method is used: welding is performed by feeding the welding wire and alternately switching between the period of pulse arc welding and the period of short-circuit transfer arc welding (for example, refer to Patent Document 1). The switching frequency in this case is about 0.1 to 10 Hz. In this welding method, a beautiful scaly weld can be formed. Furthermore, in this welding method, by adjusting the ratio of the period of pulse arc welding to the period of short-circuit transfer arc welding, heat input to the base material can be controlled.

[0003] The invention of Patent Document 2 discloses an arc welding method, in which welding is performed by alternately switching between 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 reversely to perform short circuit transfer arc welding. During short circuit transfer arc welding, a forward and reverse feed arc welding method is performed, in which the feed is set to forward feed during the arc period and to reverse feed during the short circuit period. Furthermore, switching from pulse arc welding to short circuit transfer arc welding is performed during the base period after the droplet is transferred by pulse arc welding.

[0004] In the above-mentioned forward and reverse feed arc welding method, it is necessary to switch the forward feed and reverse feed of the welding wire at a high speed and high precision at about 100 Hz. For this reason, the push-pull feed method is often used as the feeding method. Furthermore, an intermediate welding wire storage part for temporarily storing the welding wire is often provided between the feeding paths of the push-side feeding motor and the pull-side feeding motor.

[0005] In the forward and reverse feed arc welding method, the forward feed period and the reverse feed period are switched synchronously with the occurrence timing of the short circuit period and the arc period. For this reason, if the welding conditions such as the set value of the welding voltage and the protruding length change and the time ratio of the short circuit period to the arc period changes, the time ratio of the forward feed period to the reverse feed period also changes, so the average feed speed of the welding wire changes. If the average feed speed changes, the amount of weld deposition changes, so the welding quality deteriorates. In order to cope with this problem, in the invention of patent document 3, the push side motor is fed forward at a fixed speed, the wire storage capacity of the intermediate wire storage part is detected, and the pull feed speed of the pull side motor is corrected and controlled based on the wire storage capacity. The average feed speed change is suppressed by this correction control.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2005-313179

[0009] Patent Document 2: Japanese Patent Application Publication No. 2015-205347

[0010] Patent Document 3: Japanese Patent Application Publication No. 2017-94380

[0011] In an arc welding method that alternates between feeding the welding wire forward for pulse arc welding and feeding the welding wire forward and reverse for short-circuit transfer arc welding, the feeding speed and feeding direction of the welding wire frequently and abruptly change. Therefore, it is a problem to feed the welding wire with high accuracy and stability. Summary of the invention

[0012] In view of the above-mentioned problems, an object of the present disclosure is to provide an arc welding method for performing welding by alternately switching between a pulse arc welding period and a short-circuit transfer arc welding period, thereby feeding a welding wire with high accuracy and stability.

[0013] In order to solve the above-mentioned problems, an arc welding method provided by one aspect of the present disclosure includes the following steps: feeding the welding wire by push-pull feed control, wherein the push-pull feed control is based on a push-side feed motor that performs forward feed rotation and a pull-side feed motor that performs forward feed rotation and reverse feed rotation; temporarily accommodating the welding wire in an intermediate welding wire storage section provided between the feed paths of the push-side feed motor and the pull-side feed motor; correcting the push feed speed of the push-side feed motor or the pull feed speed of the pull-side feed motor based on the welding wire storage capacity in the intermediate welding wire storage section, thereby feeding the welding wire; And alternately switching between the following periods: a pulse arc welding period in which the welding wire is forward fed by the forward feed rotation of the push side feed motor and the forward feed rotation of the pull side feed motor, and a peak current and a base current are connected to perform pulse arc welding; and a short circuit transition arc welding period in which the welding wire is forwardly and reversely fed by the forward feed rotation of the push side feed motor and the forward and reverse feed rotation of the pull side feed motor, and a short circuit current and an arc current are connected to perform short circuit transition arc welding. During the short circuit transition arc welding period, the waveform parameters of the pull feed speed are corrected based on the wire collection capacity.

[0014] Preferably, the waveform parameter is at least one of a forward feed peak value and a reverse feed peak value.

[0015] Preferably, the waveform parameter is a forward feed peak value when the wire retraction amount is larger than a target value, and is a reverse feed peak value when the wire retraction amount is smaller than the target value.

[0016] Preferably, the waveform parameter is a reverse feed peak value when the wire retraction amount is larger than a target value, and is a forward feed peak value when the wire retraction amount is smaller than the target value.

[0017] Preferably, during the pulse arc welding period, the push feed speed and the pull feed speed are not corrected based on the wire storage amount.

[0018] Preferably, during the pulse arc welding period, the feed speed is corrected based on the wire retraction amount.

[0019] Preferably, during the pulse arc welding, when the wire retraction amount is outside a predetermined range, the feed speed is corrected based on the wire retraction amount.

[0020] Effects of the Invention

[0021] According to the above configuration, in an arc welding method that performs welding by alternately switching between a period of forward feeding of the welding wire for pulse arc welding and a period of forward and reverse feeding of the welding wire for short circuit transfer arc welding, the welding wire can be fed stably with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a block diagram of a welding power source for implementing the arc welding method according to the embodiment of the present disclosure.

[0023] Figure 2 is from Figure 1 A timing diagram of each signal when switching from a pulse arc welding period Ta to a short circuit transition arc welding period Tc in a welding power source.

[0024] Figure 3 is from Figure 1 1 is a timing diagram of each signal when switching from the short-circuit transition arc welding period Tc to the pulse arc welding period Ta in the welding power supply.

[0025] Description of Reference Numerals

[0026] 1 Welding wire

[0027] 2. Base material

[0028] 3 Arc

[0029] 4 Welding torch

[0030] 5 Feed roller

[0031] CM Current Comparison Circuit

[0032] Cm current comparison signal

[0033] DR drive circuit

[0034] Dr driving signal

[0035] E Output voltage

[0036] Ea Error amplified signal

[0037] ED output voltage detection circuit

[0038] Ed output voltage detection signal

[0039] EI Current Error Amplifier Circuit

[0040] Ei Current error amplified signal

[0041] ER Output voltage setting circuit

[0042] Er Output voltage setting signal

[0043] EV voltage error amplifier circuit

[0044] Ev voltage error amplified signal

[0045] EW Capacitor Error Amplifier Circuit

[0046] Ew Capacitance error amplification signal

[0047] Fapr Pulse feed speed setting signal

[0048] FAR pulse pull feed speed setting circuit

[0049] Far pulse pull feed speed setting signal

[0050] Farr pulse initial reverse feed speed setting signal

[0051] FASR pulse forward feed speed setting circuit

[0052] Fasr pulse forward feed speed setting signal

[0053] FC pull feed control circuit

[0054] Fc pull feed control signal

[0055] FCP Feed Control Circuit

[0056] Fcp pushes control signal

[0057] FCPR Short circuit arc feed speed setting circuit

[0058] Fcpr Short circuit arc advance speed setting signal

[0059] FCR short circuit arc pull feed speed setting circuit

[0060] Fcr short circuit arc pull feed speed setting signal

[0061] FH Feed speed correction circuit

[0062] FPH Feed Speed ​​Correction Circuit

[0063] FPR Feed Speed ​​Setting Circuit

[0064] Fpr Feed speed setting signal

[0065] FR pull feed speed setting circuit

[0066] Fr Feed speed setting signal

[0067] Fw pulling feed speed

[0068] Fwp feed speed

[0069] IAR pulse current setting circuit

[0070] Iar pulse current setting signal

[0071] IASR pulse initial current setting circuit

[0072] Iasr Pulse initial current setting signal

[0073] IBR base current setting circuit

[0074] Ibr Base current setting signal

[0075] ICR short circuit arc current setting circuit

[0076] Icr short circuit arc current setting signal

[0077] ID Current Detection Circuit

[0078] Id Current detection signal

[0079] ILR Low Level Current Setting Circuit

[0080] Ilr Low level current setting signal

[0081] IPR peak current setting circuit

[0082] Ipr Peak current setting signal

[0083] IR Current Setting Circuit

[0084] Ir current setting signal

[0085] Iw welding current

[0086] ND Neck Detection Circuit

[0087] Nd necking detection signal

[0088] PM power supply main circuit

[0089] R Current reducing resistor

[0090] SD short circuit detection circuit

[0091] Sd short circuit detection signal

[0092] STD small current period circuit

[0093] Std small current period signal

[0094] Stf Final pulse period signal

[0095] SW power supply characteristic switching circuit

[0096] During Ta pulse arc welding

[0097] Tair pulse initial reverse feed period

[0098] TAR Pulse Arc Welding Period Setting Circuit

[0099] Tar Setting signal during pulse arc welding

[0100] TARR pulse initial reverse feed period setting circuit

[0101] Tarr pulse initial reverse feed period setting signal

[0102] Tas pulse initial current period

[0103] TASR pulse initial current period setting circuit

[0104] Tasr pulse initial current period setting signal

[0105] Tb Base period

[0106] TBR base period setting circuit

[0107] Tbr Base value period setting signal

[0108] Tc during short-circuit transfer arc welding

[0109] TCR short circuit transition arc welding period setting circuit

[0110] Tcr Setting signal during short-circuit transfer arc welding

[0111] TDR current fall time setting circuit

[0112] Tdr Current fall time setting signal

[0113] TM Timer Circuit

[0114] Tm timer signal

[0115] Tp peak period

[0116] Tpd falling period

[0117] TPDR Falling Period Setting Circuit

[0118] Tpdr falling period setting signal

[0119] TPR peak period setting circuit

[0120] Tpr Peak period setting signal

[0121] TR Transistor

[0122] Trd Reverse feed deceleration period

[0123] TRDR Reverse feed deceleration period setting circuit

[0124] Trdr Reverse feed deceleration period setting signal

[0125] Trp Reverse feed peak period

[0126] Tru reverse feed acceleration period

[0127] TRUR reverse feed acceleration period setting circuit

[0128] Trur reverse feed acceleration period setting signal

[0129] Tsd Forward feed deceleration period

[0130] TSDR Forward feed deceleration period setting circuit

[0131] Tsdr Forward feed deceleration period setting signal

[0132] Tsf Final pulse period

[0133] Tsp Forward feed peak period

[0134] Tsu Forward feed acceleration period

[0135] TSUR Forward feed acceleration period setting circuit

[0136] Tsur Forward feed acceleration period setting signal

[0137] Tu rising period

[0138] TUR rising period setting circuit

[0139] Tur rising period setting signal

[0140] VD voltage detection circuit

[0141] Vd voltage detection signal

[0142] Vw welding voltage

[0143] WB intermediate wire storage unit

[0144] Wb receiving capacity signal

[0145] WBR receiving capacity setting circuit

[0146] Wbr Receive capacity setting signal

[0147] WL Reactor

[0148] WM pull side feed motor

[0149] WMP Push Side Feed Motor

[0150] Wrp reverse feed peak value

[0151] Wrr Reverse feed peak setting signal

[0152] WRS reverse feed peak initial value setting circuit

[0153] Wrs Reverse feed peak initial value setting signal

[0154] Wsp forward feed peak value

[0155] Wsr Forward feed peak setting signal

[0156] WSS forward feed peak initial value setting circuit

[0157] Wss Forward feed peak initial value setting signal DETAILED DESCRIPTION

[0158] Embodiments of the present disclosure are described below with reference to the drawings.

[0159] Figure 1 1 is a block diagram of a welding power source for implementing the arc welding method according to the embodiment of the present disclosure. Each block will be described below with reference to this figure.

[0160] The power supply main circuit PM, for example, receives a voltage from a 3-phase 200V commercial power supply (not shown) as an input, and outputs an output voltage E according to output control based on an error amplification signal Ea and inverter control. The power supply main circuit PM includes, for example: a primary rectifier that rectifies the AC voltage from the commercial power supply into a DC; a smoothing capacitor that smoothes the rectified DC; an inverter circuit that converts the smoothed DC into a high-frequency AC (driven by the error amplification signal Ea described above); a high-frequency transformer that steps down the high-frequency AC to a voltage value suitable for welding; and a secondary rectifier that rectifies the stepped-down high-frequency AC into a DC.

[0161] Reactor WL smoothes welding current Iw to maintain a stable arc 3.

[0162] The push-side feed motor WMP receives the push feed control signal Fcp as input, performs forward feed rotation, and feeds the welding wire 1 at a push feed speed Fwp. The pull-side feed motor WM receives the pull feed control signal Fc as input, performs forward feed rotation and reverse feed rotation, and feeds the welding wire 1 at a pull feed speed Fw. The push-side feed motor WMP is arranged on the upstream side of the feed path, and the pull-side feed motor WM is arranged on the downstream side. Both feed motors are speed-controlled. The push-pull feed control system includes two feed motors.

[0163] The intermediate welding wire storage unit WB is provided in the feeding path between the push-side feeding motor WMP and the pull-side feeding motor WM, temporarily stores (a part of) the welding wire 1, and outputs a welding wire storage capacity signal Wb corresponding to the welding wire storage capacity. For details of the intermediate welding wire storage unit WB, please refer to Patent Document 3. The storage capacity of the welding wire 1 can be detected by mechanical principle, electrical principle, optical principle, magnetic principle, or a combination of these principles.

[0164] The welding wire 1 is fed through the welding torch 4 by the rotation of the feed roller 5 coupled to the pull-side feed motor WM, and an arc 3 is generated between the front end portion thereof and the base material 2. A welding voltage Vw is applied between the conductive tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is turned on. A shielding gas (not shown) is ejected from the front end of the welding torch 4 to shield the arc 3 from the atmosphere. As the shielding gas, a mixed gas of argon gas and carbon dioxide gas is used when the material of the welding wire 1 is steel, and argon gas is used when the material of the welding wire 1 is aluminum.

[0165] The output voltage setting circuit ER outputs a predetermined output voltage setting signal Er. The output voltage detection circuit ED detects and smoothes the output voltage E and outputs an output voltage detection signal Ed.

[0166] The voltage error amplifier circuit EV takes the output voltage setting signal Er and the output voltage detection signal Ed as inputs, amplifies the error between the output voltage setting signal Er(+) and the output voltage detection signal Ed(-), and outputs a voltage error amplified signal Ev.

[0167] The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The short circuit detection circuit SD takes the voltage detection signal Vd as input and outputs a short circuit detection signal Sd. The short circuit detection signal Sd is a signal such that when the value of the voltage detection signal Vd is less than a predetermined short circuit detection value (e.g., 10V), it is determined that it is in a short circuit period and the short circuit detection signal Sd becomes a high level. When it is greater than the short circuit detection value, it is determined that it is in an arc period and the short circuit detection signal Sd becomes a low level.

[0168] The forward feed acceleration period setting circuit TSUR outputs a predetermined forward feed acceleration period setting signal Tsur.

[0169] The forward feed deceleration period setting circuit TSDR outputs a predetermined forward feed deceleration period setting signal Tsdr.

[0170] The reverse feed acceleration period setting circuit TRUR outputs a predetermined reverse feed acceleration period setting signal Trur.

[0171] The reverse feed deceleration period setting circuit TRDR outputs a predetermined reverse feed deceleration period setting signal Trdr.

[0172] The forward feed peak initial value setting circuit WSS outputs a predetermined forward feed peak initial value setting signal Wss.

[0173] The reverse feed peak initial value setting circuit WRS outputs a predetermined reverse feed peak initial value setting signal Wrs.

[0174] The capacity setting circuit WBR outputs a predetermined capacity setting signal Wbr for setting a target value of the welding wire capacity. The capacity error amplifier circuit EW takes the above-mentioned capacity setting signal Wbr and the above-mentioned capacity signal Wb as input, amplifies the error between the capacity setting signal Wbr (-) and the capacity signal Wb (+), and outputs the capacity error amplified signal Ew. It is Ew = G (Wb-Wbr), G is the amplification factor (positive value). Therefore, when the capacity signal Wb is larger than the capacity setting signal Wbr, the capacity error amplified signal Ew becomes a positive value, and when the capacity signal Wb is smaller than the target value of the capacity setting signal Wbr, the capacity error amplified signal Ew becomes a negative value.

[0175] The pull feed speed correction circuit FH takes the above-mentioned forward feed peak initial value setting signal Wss, the above-mentioned reverse feed peak initial value setting signal Wrs and the above-mentioned receiving capacity error amplification signal Ew as input, selects one from the processing 1) to 5) shown below to perform correction control, and outputs the forward feed peak setting signal Wsr and the reverse feed peak setting signal Wrr. The correction control (modulation control) shown below is performed in each given control cycle. The control cycle is very small, for example, 0.1ms. The correction control shown below is the case where the control system is P control, but it is not limited to this, and it can also be PI control or PID control.

[0176] Processing 1) When only the forward feed peak value is corrected

[0177] The forward feed peak initial value setting signal Wss is corrected (modulated) by the receiving capacity error amplification signal Ew, and the forward feed peak setting signal Wsr=Wss+Ew is output. Then, the reverse feed peak initial value setting signal Wrs is directly output as the reverse feed peak setting signal Wrr=Wrs.

[0178] Processing 2) When only the reverse feed peak value is corrected

[0179] The reverse feed peak initial value setting signal Wrs is corrected and controlled (modulated) by the receiving capacity error amplification signal Ew, and the reverse feed peak setting signal Wrr=Wrs+Ew is output. Then, the forward feed peak initial value setting signal Wss is directly output as the forward feed peak setting signal Wsr=Wss.

[0180] Processing 3) When performing correction control on the forward feed peak value and the reverse feed peak value

[0181] The forward feed peak initial value setting signal Wss is corrected (modulated) by the received capacity error amplification signal Ew, and the forward feed peak setting signal Wsr = Wss + Ew is output. Then, the reverse feed peak initial value setting signal Wrs is corrected (modulated) by the received capacity error amplification signal Ew, and the reverse feed peak setting signal Wrr = Wrs + Ew is output.

[0182] Processing 4) The first case of performing correction control on the forward feed peak value and the reverse feed peak value according to the positive and negative signs of the received capacity error amplification signal Ew

[0183] When the received capacity error amplification signal Ew≥0, the forward feed peak initial value setting signal Wss is corrected (modulated) by the received capacity error amplification signal Ew, and the forward feed peak setting signal Wsr=Wss+Ew is output. On the other hand, when the received capacity error amplification signal Ew<0, the reverse feed peak initial value setting signal Wrs is corrected (modulated) by the received capacity error amplification signal Ew, and the reverse feed peak setting signal Wrr=Wrs+Ew is output.

[0184] Processing 5) The second case of performing correction control on the forward feed peak value and the reverse feed peak value according to the positive and negative signs of the received capacity error amplification signal Ew

[0185] When the received capacity error amplification signal Ew is less than 0, the forward feed peak initial value setting signal Wss is corrected (modulated) by the received capacity error amplification signal Ew, and the forward feed peak setting signal Wsr=Wss+Ew is output. On the other hand, when the received capacity error amplification signal Ew is greater than or equal to 0, the reverse feed peak initial value setting signal Wrs is corrected (modulated) by the received capacity error amplification signal Ew, and the reverse feed peak setting signal Wrr=Wrs+Ew is output.

[0186] The short-circuit arc pull feed speed setting circuit FCR 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 discrimination signal Sd as input, and outputs a feed speed pattern generated by the following processing as the short-circuit arc pull feed speed setting signal Fcr. When the short-circuit arc pull feed speed setting signal Fcr is a positive value, it becomes a forward feed period, and when it is a negative value, it becomes a reverse feed period.

[0187] 1) During the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur, the output is a short-circuit arc pull feed speed setting signal Fcr that extends linearly from 0 (wherein, the value determined by the pulse pull feed speed setting signal Far just after switching to the short-circuit transition arc welding period Tc) to (accelerates to) a positive value of the forward feed peak value Wsp determined by the forward feed peak value setting signal Wsr.

[0188] 2) Next, during the forward feed peak period Tsp, the short-circuit arc pulling feed speed setting signal Fcr is output to maintain the above-mentioned forward feed peak value Wsp.

[0189] 3) If the short-circuit detection signal Sd changes from a low level (arc period) to a high level (short-circuit period), it transitions to the forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr, and outputs a short-circuit arc feed speed setting signal Fcr that extends linearly from the above-mentioned forward feed peak value Wsp to (decelerates to) 0.

[0190] 4) Then, during the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur, the short-circuit arc pull feed speed setting signal Fcr is output, which extends linearly from 0 to (accelerates to) the reverse feed peak value Wrp of the negative value determined by the reverse feed peak setting signal Wrr.

[0191] 5) Next, during the reverse feed peak period Trp, the short-circuit arc pulling feed speed setting signal Fcr is output to maintain the above-mentioned reverse feed peak value Wrp.

[0192] 6) If the short-circuit detection signal Sd changes from a high level (short-circuit period) to a low level (arc period), it transitions to the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr, and outputs a short-circuit arc feed speed setting signal Fcr that extends linearly from the above-mentioned reverse feed peak value Wrp to (decelerates to) 0.

[0193] 7) By repeating the above steps 1) to 6), a short-circuit arc pulling feed speed setting signal Fcr having a feed pattern with positive and negative trapezoidal changes is generated.

[0194] The current reducing resistor R is inserted between the reactor WL and the welding torch 4. The value of the current reducing resistor R is set to a value (about 0.5 to 3Ω) that is 50 times or more as large as the resistance value (about 0.01 to 0.03Ω) of the circuit through which the welding current Iw passes during the short circuit period. When the current reducing resistor R is inserted into the circuit through which the welding current Iw passes, the energy stored in the reactor WL and the reactor of the welding cable is rapidly consumed.

[0195] The transistor TR is connected in parallel with the above-mentioned current reducing resistor R, and is controlled to be turned on or off according to the drive signal Dr.

[0196] The necking detection circuit ND receives the short-circuit determination signal Sd, the voltage detection signal Vd, and the current detection signal Id as inputs, and outputs a necking detection signal Nd. The necking detection signal Nd is a signal such that when the voltage rise value of the voltage detection signal Vd reaches the reference value when the short-circuit determination signal Sd is at a high level (during the short-circuit period), the necking formation state is determined to be the reference state, and the necking detection signal Nd becomes a high level. When the short-circuit determination signal Sd changes to a low level (during the arc period), the necking detection signal Nd becomes a low level. Alternatively, when the differential value of the voltage detection signal Vd during the short-circuit period reaches the corresponding reference value, the necking detection signal Nd changes to a high level. Furthermore, the resistance value of the droplet can be calculated by dividing the value of the voltage detection signal Vd by the value of the current detection signal Id, and when the differential value of the resistance value reaches the corresponding reference value, the necking detection signal Nd changes to a high level.

[0197] The low level current setting circuit ILR outputs a predetermined low level current setting signal Ilr. The current comparison circuit CM takes the low level current setting signal Ilr and the above-mentioned current detection signal Id as input, and outputs a current comparison signal Cm that becomes high level when Id<Ilr and becomes low level when Id≥Ilr.

[0198] The drive circuit DR receives the current comparison signal Cm and the constriction detection signal Nd as inputs, and outputs the drive signal Dr to the base terminal of the transistor TR. The drive signal Dr is a signal that changes to a low level when the constriction detection signal Nd changes to a high level, and changes to a high level when the current comparison signal Cm changes to a high level. Therefore, when constriction is detected, the drive signal Dr becomes a low level, and the transistor TR becomes an off state, and a current reduction resistor R is inserted in the on-circuit, so that the welding current Iw decreases sharply. Then, when the value of the sharply reduced welding current Iw decreases to the value of the low-level current setting signal Ilr, the drive signal Dr becomes a high level, and the transistor TR becomes an on state, so that the current reduction resistor R is short-circuited and returns to a normal state.

[0199] The short-circuit arc current setting circuit ICR takes the above-mentioned short-circuit determination signal Sd, the above-mentioned low-level current setting signal Ilr and the above-mentioned necking detection signal Nd as input signals, performs the following processing, and outputs the short-circuit arc current setting signal Icr.

[0200] 1) When the short-circuit determination signal Sd is at a low level (during the arc period), the output is a short-circuit arc current setting signal Icr which becomes a low-level current setting signal Ilr.

[0201] 2) If the short-circuit detection signal Sd changes to a high level (during a short-circuit period), the output becomes a predetermined initial current setting value during a predetermined initial period, and then rises to a predetermined short-circuit peak setting value at a predetermined short-circuit slope and maintains the short-circuit arc current setting signal Icr.

[0202] 3) Thereafter, if the necking detection signal Nd changes to a high level, a short-circuit arc current setting signal Icr having the value of the low-level current setting signal Ilr is output.

[0203] The current fall time setting circuit TDR outputs a predetermined current fall time setting signal Tdr.

[0204] The small current period circuit STD takes the above-mentioned short circuit determination signal Sd and the above-mentioned current fall time setting signal Tdr as inputs, and outputs the small current period signal Std. The small current period signal Std is a signal as follows: at the time point when the short circuit determination signal Sd changes to a low level (arc period) and the time determined by the current fall time setting signal Tdr passes, the small current period signal Std becomes a high level, and thereafter, if the short circuit determination signal Sd becomes a high level (short circuit period), the small current period signal Std becomes a low level.

[0205] The peak period setting circuit TPR takes the final pulse cycle signal Stf as input and outputs a peak period setting signal Tpr. The peak period setting signal Tpr is a signal such that when the final pulse cycle signal Stf is at a low level, the peak period setting signal Tpr becomes a predetermined steady-state peak period, and when the final pulse cycle signal Stf is at a high level, the peak period setting signal Tpr becomes a predetermined final peak period.

[0206] The peak rise period setting circuit TUR takes the final pulse cycle signal Stf as input and outputs a peak rise period setting signal Tur. The peak rise period setting signal Tur is a signal such that when the final pulse cycle signal Stf is at a low level, the peak rise period setting signal Tur becomes a predetermined steady-state peak rise period, and when the final pulse cycle signal Stf is at a high level, the peak rise period setting signal Tur becomes a predetermined final peak rise period.

[0207] The peak drop period setting circuit TPDR takes the final pulse cycle signal Stf as input and outputs a peak drop period setting signal Tpdr. The peak drop period setting signal Tpdr is a signal as follows: when the final pulse cycle signal Stf is at a low level, the peak drop period setting signal Tpdr becomes a predetermined steady-state peak drop period, and when the final pulse cycle signal Stf is at a high level, the peak drop period setting signal Tpdr becomes a predetermined final peak drop period.

[0208] The base period setting circuit TBR outputs a predetermined base period setting signal Tbr.

[0209] The peak current setting circuit IPR takes the above-mentioned voltage error amplified signal Ev as input, performs modulation control, and outputs a peak current setting signal Ipr. The modulation control is performed by integrating the voltage error amplified signal Ev as Ipr=Ip0-∫Kp·Ev·dt. Ip0 is the initial value of the peak current value, and Kp is a constant for adjusting the gain of the peak current modulation control to a suitable value.

[0210] The base current setting circuit IBR takes the voltage error amplified signal Ev as input, performs modulation control, and outputs the base current setting signal Ibr. The modulation control is performed by integrating the voltage error amplified signal Ev as Ibr=Ib0-∫Kb·Ev·dt. Ib0 is the initial value of the base current value, and Kb is a constant for adjusting the gain of the base current modulation control to a suitable value.

[0211] The pulse initial reverse feed period setting circuit TARR outputs a predetermined pulse initial reverse feed period setting signal Tarr.

[0212] The pulse initial current period setting circuit TASR outputs a predetermined pulse initial current period setting signal Tasr. The pulse initial current setting circuit IASR outputs a predetermined pulse initial current setting signal Iasr.

[0213] The pulse current setting circuit IAR takes the timer signal Tm, the above-mentioned peak period setting signal Tpr, the above-mentioned peak rise period setting signal Tur, the above-mentioned peak fall period setting signal Tpdr, the above-mentioned base period setting signal Tbr, the above-mentioned peak current setting signal Ipr, the above-mentioned base current setting signal Ibr, the above-mentioned pulse initial current period setting signal Tasr and the above-mentioned pulse initial current setting signal Iasr as input, performs the following processing, and outputs the pulse current setting signal Iar.

[0214] 1) When the timer signal Tm is at a low level (during short-circuit transfer arc welding), the value of the pulse initial current setting signal Iasr is output as the pulse current setting signal Iar.

[0215] 2) At the time point when the timer signal Tm changes from a low level to a high level (during pulse arc welding), during the pulse initial current period Tas determined by the pulse initial current period setting signal Tasr, the value of the pulse initial current setting signal Iasr is output as the pulse current setting signal Iar.

[0216] 3) Then, during the peak rise period Tu determined by the peak rise period setting signal Tur, a pulse current setting signal Iar is output that increases from the value of the pulse initial current setting signal Iasr (the base current setting signal Ibr from the second pulse cycle) to the value of the peak current setting signal Ipr.

[0217] 4) Next, during the peak period Tp determined by the peak period setting signal Tpr, the pulse current setting signal Iar is outputted to maintain the value of the peak current setting signal Ipr.

[0218] 5) Next, during the peak falling period Tpd determined by the peak falling period setting signal Tpdr, the pulse current setting signal Iar is outputted so as to decrease from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr.

[0219] 6) Next, during the base period Tb determined by the base period setting signal Tbr, the pulse current setting signal Iar is outputted to maintain the value of the base current setting signal Ibr.

[0220] 7) The above steps 3) to 6) are regarded as one pulse cycle and are repeated until the timer signal Tm changes to a low level.

[0221] The pulse arc welding period setting circuit TAR outputs a predetermined pulse arc welding period setting signal Tar. The short circuit transfer arc welding period setting circuit TCR outputs a predetermined short circuit transfer arc welding period setting signal Tcr.

[0222] The timer circuit TM receives the above-mentioned pulse arc welding period setting signal Tar, the above-mentioned short-circuit transition arc welding period setting signal Tcr, the above-mentioned short-circuit determination signal Sd, the above-mentioned pulse current setting signal Iar, and the above-mentioned base current setting signal Ibr as inputs, and outputs a timer signal Tm and a final pulse cycle signal Stf. The timer signal Tm changes from a high level to a low level (short-circuit transition arc welding period Tc) at the time point ( Figure 2The time point (t1) when the period determined by the short-circuit transition arc welding period setting signal Tcr has passed and the short-circuit determination signal Sd first changes to a low level (arc period) Figure 3 , t1), changes to a high level. If a new pulse cycle starts after a period determined by the pulse arc welding period setting signal Tar from the time point when the timer signal Tm changes to a high level (pulse arc welding period Ta), the final pulse cycle Tsf is entered. At the time point when the pulse current setting signal Iar becomes equal to the value of the base current setting signal Ibr in the final pulse cycle Tsf, the final pulse cycle Tsf ends and the timer signal Tm changes to a low level. The final pulse cycle signal Stf is a signal that becomes a high level only in the above-mentioned final pulse cycle Tsf, and remains at a low level otherwise. Therefore, the pulse arc welding period Ta is the period of the pulse arc welding period setting signal Tar + the period starting until the final pulse cycle Tsf + the period of the final pulse cycle Tsf. The short-circuit transition arc welding period Tc is the period of the short-circuit transition arc welding period setting signal Tcr + the period until the end of the initial short-circuit period thereafter.

[0223] The pulse initial reverse feed speed setting signal FARR outputs a predetermined pulse initial reverse feed speed setting signal Farr that takes a negative value. The pulse forward feed speed setting circuit FASR outputs a predetermined pulse forward feed speed setting signal Fasr that takes a positive value. The average feed speed in the pulse arc welding period Ta is set by the value of the pulse forward feed speed setting signal Fasr.

[0224] The pulse pull feed speed setting circuit FAR takes the above-mentioned timer signal Tm, the above-mentioned pulse initial reverse feed period setting signal Tarr, the above-mentioned pulse initial reverse feed speed setting signal Farr and the above-mentioned pulse forward feed speed setting signal Fasr as input, performs the following processing, and outputs the pulse pull feed speed setting signal Far.

[0225] 1) When the timer signal Tm is at a low level (during short-circuit transfer arc welding), the value of the pulse initial reverse feed speed setting signal Farr is output as the pulse pull feed speed setting signal Far.

[0226] 2) At the time point when the timer signal Tm changes from a low level to a high level (during pulse arc welding), during the pulse initial reverse feed period Tair determined by the pulse initial reverse feed period setting signal Tarr, the value of the pulse initial reverse feed speed setting signal Farr is output as the pulse pull feed speed setting signal Far.

[0227] 3) Next, during the period until the timer signal Tm changes to a low level, the value of the pulse forward feed speed setting signal Fasr is output as the pulse backward feed speed setting signal Far.

[0228] The pull-feed speed setting circuit FR takes the above-mentioned timer signal Tm, the above-mentioned short-circuit arc pull-feed speed setting signal Fcr and the above-mentioned pulse pull-feed speed setting signal Far as inputs. When the timer signal Tm is at a high level (during pulse arc welding Ta), it outputs the pulse pull-feed speed setting signal Far as the pull-feed speed setting signal Fr. When it is at a low level (during short-circuit transition arc welding Tc), it outputs the short-circuit arc pull-feed speed setting signal Fcr as the pull-feed speed setting signal Fr.

[0229] The feed control circuit FC receives the feed speed setting signal Fr as input, and outputs a feed control signal Fc for feeding the welding wire 1 at a feed speed Fw corresponding to the value of the feed speed setting signal Fr to the feed motor WM.

[0230] The short-circuit arc advance feed speed setting circuit FCPR outputs a predetermined short-circuit arc advance feed speed setting signal Fcpr having a positive value. The average feed speed in the short-circuit transfer arc welding period Tc is set by the value of the short-circuit arc advance feed speed setting signal Fcpr.

[0231] The feed speed correction circuit FPH receives the above-mentioned amplified signal Ew of the amount of absorption error as an input, selects one of the following processes 1) to 3) to perform correction control, and outputs a pulse feed speed setting signal Fapr.

[0232] Processing 1) By receiving the capacity error amplification signal Ew, a correction control (modulation control) is performed on the predetermined initial value of the pulse feed speed, and a pulse feed speed setting signal Fapr=initial value of the pulse feed speed-Ew is output.

[0233] Processing 2) When the received capacity error amplification signal Ew is outside the given range, the predetermined initial value of the pulse feed speed is corrected and controlled (modulated) by the received capacity error amplification signal Ew, and the pulse feed speed setting signal Fapr = initial value of the pulse feed speed - Ew is output.

[0234] Processing 3) The predetermined initial value of the pulse feed speed is not corrected and is directly output as the pulse feed speed setting signal Fapr.

[0235] The push feed speed setting circuit FPR takes the above-mentioned timer signal Tm, the above-mentioned short-circuit arc push feed speed setting signal Fcpr and the above-mentioned pulse push feed speed setting signal Fapr as inputs. When the timer signal Tm is at a high level (during pulse arc welding Ta), it outputs the pulse push feed speed setting signal Fapr as the push feed speed setting signal Fpr. When it is at a low level (during short-circuit transition arc welding Tc), it outputs the short-circuit arc push feed speed setting signal Fcpr as the push feed speed setting signal Fpr.

[0236] Push feed control circuit FCP receives push feed speed setting signal Fpr as input, and outputs push feed control signal Fcp for feeding welding wire 1 at push feed speed Fwp corresponding to the value of push feed speed setting signal Fpr to push feed motor WMP.

[0237] The current setting circuit IR takes the above-mentioned timer signal Tm, the above-mentioned short-circuit arc current setting signal Icr and the above-mentioned pulse current setting signal Iar as inputs. When the timer signal Tm is at a high level (during pulse arc welding Ta), it outputs the pulse current setting signal Iar as the current setting signal Ir. When it is at a low level (during short-circuit transition arc welding Tc), it outputs the short-circuit arc current setting signal Icr as the current setting signal Ir.

[0238] The current error amplifier circuit EI receives the current setting signal Ir and the current detection signal Id as inputs, amplifies the error between the current setting signal Ir(+) and the current detection signal Id(-), and outputs a current error amplified signal Ei.

[0239] The power supply characteristic switching circuit SW takes the above-mentioned timer signal Tm, the above-mentioned current error amplification signal Ei, the above-mentioned voltage error amplification signal Ev, the above-mentioned short-circuit judgment signal Sd and the above-mentioned small current period signal Std as input, performs the following processing, and outputs the error amplification signal Ea.

[0240] 1) During the period from the time point when the timer signal Tm is at a low level and the short-circuit determination signal Sd changes to a high level (short-circuit period) to the time point when the short-circuit determination signal Sd changes to a low level (arc period) and passes through the above-mentioned delay period, the current error amplification signal Ei is output as the error amplification signal Ea.

[0241] 2) During the subsequent high current arc period, the voltage error amplification signal Ev is output as the error amplification signal Ea.

[0242] 3) In the subsequent arc period, during the small current arc period in which the small current period signal Std becomes a high level, the current error amplification signal Ei is output as the error amplification signal Ea.

[0243] 4) During the period from when the timer signal Tm changes to a low level to when the short-circuit determination signal Sd first becomes a high level, and when the timer signal Tm is at a high level, the current error amplification signal Ei is output as the error amplification signal Ea.

[0244] By means of this circuit, the characteristics of the welding power source in the short-circuit transition arc welding period Tc become constant current characteristics in the period from the start of the short-circuit transition arc welding period Tc to the first occurrence of a short circuit, the short circuit period, the delay period, and the low-current arc period, and become constant voltage characteristics in the other high-current arc periods (the period from the time point when the short-circuit determination signal Sd changes from a high level to a low level after the delay time has elapsed during the period when the timer signal Tm is at a low level to the time point when the low-current period signal Std changes from a low level to a high level). In addition, the characteristics of the welding power source in the pulse arc welding period Ta become constant current characteristics.

[0245] Figure 2 The arc welding method according to the embodiment of the present disclosure is shown in FIG. Figure 1 The timing diagram of each signal when switching from the pulse arc welding period Ta to the short-circuit transition arc welding period Tc in the welding power source. (A) of the figure shows the time change of the pull-in 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 small current period signal Std, (F) of the figure shows the time change of the timer signal Tm, (G) of the figure shows the time change of the final pulse cycle signal Stf, and (H) of the figure shows the time change of the push-in feed speed Fwp.

[0246] Time t0 is the time from when the timer signal Tm shown in (F) of the figure changes to a high level (the start time of the pulse arc welding period Ta) to when the timer signal Tm reaches the high level. Figure 1 The time when a new pulse cycle starts after the period determined by the pulse arc welding period setting signal Tar. At time t0, as shown in (G) of the figure, the final pulse cycle signal Stf changes to a high level and enters the final pulse cycle Tsf. In the final pulse cycle Tsf from time t0 to t1, as shown in (B) of the figure, during the predetermined final peak rise period Tu, the pulse cycle signal Stf is turned on. Figure 1The peak current setting signal Ipr is used to set the peak current value Ip. During the final peak period Tp, which is determined in advance, the current is turned on at the peak current value Ip. During the final peak falling period Tpd, which is determined in advance, the current is turned on from the peak current value Ip to the peak current value Ip. Figure 1 The transition current is a transition current that decreases the base current value Ib determined by the base current setting signal Ibr. When the final peak drop period Tpd ends at time t1, and the welding current Iw becomes the above-mentioned base current Ib, the final pulse cycle signal Stf returns to a low level as shown in (G) of the figure, and the final pulse cycle Tsf ends. The values ​​of the final peak rise period Tu, the final peak period Tp, and the final peak drop period Tpd in the final pulse cycle Tsf are set to values ​​that prevent the droplet formed in the final pulse cycle Tsf from transitioning.

[0247] From the time point when the timer signal Tm shown in (F) of the figure changes to a high level (pulse arc welding period Ta), a period of time has passed. Figure 1 After the pulse arc welding period setting signal Tar determines the period, it becomes a new pulse cycle and enters the final pulse cycle Tsf. Figure 1 The pulse current setting signal Iar becomes Figure 1 The value of the base current setting signal Ibr is equal to that of the base current setting signal Ibr, and the timing at this time is time t1. At time t1, as shown in (F) of the figure, the timer signal Tm changes from a high level to a low level. Therefore, at time t1, the pulse arc welding period Ta is switched to the short-circuit transfer arc welding period Tc. In the figure, in the period before time t1, as shown in (A) of the figure, the feed speed Fw is set to Figure 1 The forward feed speed setting signal Fasr is used to perform forward feed at a fixed speed determined by the pulse forward feed speed setting signal Fasr. On the other hand, as shown in (H) of the figure, the forward feed speed Fwp is set to a fixed speed determined by Figure 1 The pulse feed speed setting signal Fapr is used to feed forward at the speed determined by the pulse feed speed setting signal Fapr. Figure 1 The push feed speed correction circuit FPH selects any one of processing 1) to 3) to perform correction control on the push feed speed Fwp. When processing 1) is selected, the push feed speed Fwp is subjected to variable speed control so that Figure 1 The value of the capacity signal Wb of the intermediate wire storage portion becomes equal to the target value. In the case of selecting processing 2), the feed speed Fwp is only Figure 1When the error between the value of the storage capacity signal Wb of the intermediate welding wire storage portion and the target value is outside the given range, correction control is performed. In the case of selecting process 3), the feed speed Fwp is not corrected and thus becomes a fixed speed. As shown in (C) of the figure, the welding voltage Vw becomes a waveform similar to the welding current Iw. As shown in (D) of the figure, the short circuit determination signal Sd remains at a low level because the arc period continues. As shown in (E) of the figure, the low current period signal Std remains at a low level.

[0248] At time t1, as shown in (F) of the figure, the timer signal Tm changes to a low level and enters the short-circuit transfer arc welding period Tc. In response to this, as shown in (A) of the figure, the feed speed Fw is increased from Figure 1 The forward feed peak value Wsp determined by the forward feed peak value setting signal Wsr is accelerated and maintained at this value until a short circuit occurs at time t3. The forward feed peak value Wsp during this period can be set to a value different from that during the steady state period of the short circuit transfer arc welding period Tc. The different value is set so that the welding state during this period becomes a stable welding state.

[0249] As shown in (H) of the figure, in the short-circuit transfer arc welding period Tc after time t1, the feed speed Fwp is increased by Figure 1 The short-circuit arc feed speed setting signal Fcpr is used to feed the electric arc in the forward direction at a fixed speed determined by the electric arc feed speed setting signal Fcpr. No correction control is performed on the feed speed Fwp.

[0250] During the period Tc from the start of the short-circuit transfer arc welding at time t1 to the occurrence of the first short circuit at time t3, as shown in (B) of the figure, the welding power source has a constant current characteristic, so the welding current Iw is determined by Figure 1 The low-level current value is determined by the low-level current setting signal Ilr.

[0251] The pulling feed speed Fw shown in (A) of the figure is controlled from Figure 1 The value of the short-circuit arc pull feed speed setting signal Fcr output by the short-circuit arc pull feed speed setting circuit FCR. The pull feed speed Fw includes the following period: Figure 1 The forward feed acceleration period Tsu is determined by the forward feed acceleration period setting signal Tsur; the forward feed peak period Tsp continues until a short circuit occurs; Figure 1 The forward feed deceleration period Tsd is determined by the forward feed deceleration period setting signal Tsdr; Figure 1 The reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur; the reverse feed peak period Trp which continues until an arc is generated; and Figure 1The reverse feed deceleration period Trd is determined by the reverse feed deceleration period setting signal Trdr. Furthermore, the forward feed peak value Wsp is given by Figure 1 The forward feed peak value setting signal Wsr is determined by the reverse feed peak value Wrp. Figure 1 As a result, the short-circuit arc feed speed setting signal Fcr becomes a feed pattern that changes in a substantially trapezoidal wave shape protruding toward the positive and negative sides.

[0252] In this figure, the Figure 1 The pull feed speed correction circuit FH selects one of the processes 1) to 5) to perform correction control on the forward feed peak value Wsp (forward feed peak value setting signal Wsr) and / or the reverse feed peak value Wrp (reverse feed peak value setting signal Wrr).

[0253] The following is a numerical example of the correction control of the above-mentioned pulling feed speed Fw. Assume that Wss = 60m / min, Wrs = -50m / min. When Ew = 2,

[0254] In the case of treatment 1), Wsr = 60 + 2 = 62, Wrr = -50

[0255] In case of treatment 2) Wsr = 60, Wrr = -50 + 2 = -48

[0256] In the case of process 3), Wsr = 60 + 2 = 62, Wrr = -50 + 2 = -48

[0257] In the case of treatment 4), since Ew ≥ 0, Wsr = 60 + 2 = 62, Wrr = -50

[0258] In the case of process 5), since Ew ≥ 0, Wsr = 60, Wrr = -50 + 2 = -48

[0259] In addition, when Ew = -3,

[0260] In the case of treatment 1), Wsr = 60-3 = 57, Wrr = -50

[0261] In case of treatment 2) Wsr = 60, Wrr = -50-3 = -53

[0262] In the case of treatment 3), Wsr = 60-3 = 57, Wrr = -50-3 = -53

[0263] In the case of treatment 4), since Ew < 0, Wsr = 60, Wrr = -50-3 = -53

[0264] In the case of treatment 5), since Ew < 0, Wsr = 60-3 = 57, Wrr = -50

[0265] <Operation during the short-circuit period from time t3 to time t6>

[0266] If a short circuit occurs at time t3 during the forward feed peak period Tsp, as shown in (C) of the figure, the welding voltage Vw drops sharply to a short circuit voltage value of several V, so as shown in (D) of the figure, the short circuit determination signal Sd changes to a high level (short circuit period). In response to this, the predetermined forward feed deceleration period Tsd from time t3 to t4 is transitioned to, and as shown in (A) of the figure, the pull feed speed Fw is decelerated from the forward feed peak Wsp to 0. For example, the forward feed deceleration period Tsd is set to 1 ms.

[0267] As shown in (A) of the figure, the pulling feed speed Fw enters the predetermined reverse feed acceleration period Tru from time t4 to t5, and accelerates from 0 to the reverse feed peak value Wrp. During this period, the short circuit period continues. For example, the reverse feed acceleration period Tru is set to 1 ms.

[0268] If the reverse feed acceleration period Tru ends at time t5, as shown in (A) of the figure, the pull feed speed Fw enters the reverse feed peak period Trp and becomes the reverse feed peak Wrp mentioned above. The reverse feed peak period Trp continues until the arc is generated at time t6. Therefore, the period from time t3 to t6 becomes a short circuit period. The reverse feed peak period Trp becomes, for example, about 4ms. The reverse feed peak Wrp may or may not be modulated, for example, it may become -60m / min.

[0269] As shown in (B) of the figure, welding current Iw in the short circuit period from time t3 to t6 reaches a predetermined initial current value in a predetermined initial period. Thereafter, welding current Iw rises with a predetermined short circuit slope and maintains this value when it reaches a predetermined short circuit peak value.

[0270] As shown in (C) of the figure, the welding voltage Vw increases every time the welding current Iw reaches a short circuit peak value. This is because the molten droplet at the tip of the welding wire 1 gradually forms a neck due to the reverse feeding of the welding wire 1 and the pinching force caused by the welding current Iw.

[0271] When the voltage increase value of the welding voltage Vw reaches the reference value, it is determined that the necking state has reached the reference state, and the welding voltage Vw is Figure 1 The necking detection signal Nd changes to a high level.

[0272] In response to the necking detection signal Nd becoming a high level, Figure 1 The driving signal Dr becomes a low level, so Figure 1The transistor TR becomes off state, Figure 1 The current reducing resistor R is inserted into the welding current Iw through the circuit. At the same time, Figure 1 The short-circuit arc current setting signal Icr decreases to the value of the low-level current setting signal Ilr. 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. When the welding current Iw decreases to the low-level current value, the drive signal Dr returns to the high level, so the transistor TR becomes on and the current reduction resistor R is short-circuited. As shown in (B) of the figure, since the short-circuit arc current setting signal Icr maintains the state of the low-level current setting signal Ilr, the welding current Iw maintains the low-level current value from the time when the arc is regenerated until the predetermined delay period has passed. Therefore, the transistor TR is turned off only during the period from the time when the necking detection signal Nd changes to the high level to the time when the welding current Iw decreases to the low-level current value. As shown in (C) of the figure, since the welding current Iw decreases, the welding voltage Vw decreases once and then rises sharply. The above-mentioned parameters are set to the following values, for example. Initial current = 40A, initial period = 0.5ms, short circuit inclination = 180A / ms, short circuit peak = 400A, low level current value = 50A, delay period = 0.5ms.

[0273] <Operation during the arc period from time t6 to time t9>

[0274] At time t6, when the constriction progresses due to the pinching force caused by the reverse feeding of the welding wire and the connection 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, and the short circuit determination signal Sd changes to a low level (arc period) as shown in (D) of the figure. In response to this, the reverse feeding deceleration period Trd predetermined from time t6 to t7 is transitioned, and the pulling feed speed Fw is decelerated from the reverse feeding peak value Wrp to 0 as shown in (A) of the figure.

[0275] When the reverse feed deceleration period Trd ends at time t7, the forward feed acceleration period Tsu is transitioned to the predetermined forward feed acceleration period Tsu from time t7 to t8. During the forward feed acceleration period Tsu, as shown in (A) of the figure, the pull feed speed Fw is accelerated from 0 to the forward feed peak value Wsp mentioned above. During this period, the arc period continues. For example, the forward feed acceleration period Tsu is set to 1ms.

[0276] If the forward feed acceleration period Tsu ends at time t8, the pull feed speed Fw enters the forward feed peak period Tsp as shown in (A) of the figure, and becomes the forward feed peak Wsp mentioned above. The arc period also continues during this period. The forward feed peak period Tsp continues until a short circuit occurs at time t9. Therefore, the period from time t6 to t9 becomes the arc period. If a short circuit occurs, the action returns to time t3. Although the forward feed peak period Tsp is not a given value, it is about 4ms. The forward feed peak Wsp may be modulated or not, for example, 70m / min.

[0277] If an arc is generated at time t6, as shown in (C) of the figure, the welding voltage Vw increases sharply to an arc voltage value of several tens of volts. On the other hand, as shown in (B) of the figure, the welding current Iw continues to have a low current value during the delay period from time t6 to t61. After that, the welding current Iw increases rapidly from time t61 and reaches a peak value, and then gradually decreases to a large current value. During the high current arc period from time t61 to t81, the welding current Iw is Figure 1 The voltage error amplified signal Ev performs feedback control on the welding power source, thereby achieving a constant voltage characteristic. Therefore, the value of the welding current Iw during the high current arc period changes according to the arc load.

[0278] At time t6, an arc occurs and passes through Figure 1 At the time t81 when the current falling time is determined by the current falling time setting signal Tdr, as shown in (E) of the figure, the low current period signal Std changes to a high level. In response to this, the welding power source switches from the constant voltage characteristic to the constant current characteristic. For this reason, as shown in (B) of the figure, the welding current Iw is reduced to a low-level current value, and this value is maintained until the time t9 when a short circuit occurs. Similarly, as shown in (C) of the figure, the welding voltage Vw is also reduced. If a short circuit occurs at time t9, the low current period signal Std returns to a low level.

[0279] The short-circuit transition arc welding period Tc includes a plurality of repeated cycles of the short-circuit period and the arc period. One cycle of the short-circuit / arc is, for example, about 10 ms. The short-circuit transition arc welding period Tc is, for example, about 50 to 500 ms. Figure 2 The case where the welding process is switched to the short-circuit transfer arc welding period Tc at the start time of the base period in a state where the droplet has not yet transferred. Alternatively, the welding process may be switched in the middle of the base period Tb.

[0280] Figure 3 The arc welding method according to the embodiment of the present disclosure is shown in FIG. Figure 1The timing diagram of each signal when switching from the short-circuit transition arc welding period Tc to the pulse arc welding period Ta in the welding power source. (A) of the figure shows the time change of the pull-in 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 low current period signal Std, (F) of the figure shows the time change of the timer signal Tm, and (G) of the figure shows the time change of the push-in feed speed Fwp.

[0281] At time t1, as shown in (B) of the figure, the short circuit is released and the arc is generated again, so the welding current Iw becomes a low-level current value. In addition, since time t1 is the time when the timer signal Tm shown in (F) of the figure changes to a low level (short-circuit transfer arc welding period Tc), the welding current Iw becomes a low-level current value. Figure 1 At the time point when the short-circuit determination signal Sd first changes to a low level (arc period) after the period determined by the short-circuit transition arc welding period setting signal Tcr, the timer signal Tm changes from a low level to a high level as shown in (F) of the figure. Therefore, at time t1, the short-circuit transition arc welding period Tc is switched to the pulse arc welding period Ta. In the figure, in the period before time t1, as shown in (A) of the figure, the pull feed speed Fw is in a state of reverse feed peak Wrp. As shown in (C) of the figure, the welding voltage Vw becomes a short-circuit voltage value. As shown in (D) of the figure, the short-circuit determination signal Sd changes from a high level (short-circuit period) to a low level (arc period) at time t1. As shown in (E) of the figure, the small current period signal Std remains in a low level state. As shown in (G) of the figure, the push feed speed Fwp is determined by Figure 1 The short-circuit arc advances at a fixed speed determined by the feed speed setting signal Fcpr for forward feeding.

[0282] At time t1, as shown in (F) of the figure, the timer signal Tm changes to a high level, and the pulse arc welding period Ta begins. In response to this, as shown in (A) of the figure, the feed speed Fw enters the high level. Figure 1 The pulse initial reverse feed period setting signal Tarr determines the pulse initial reverse feed period Tair. The pull feed speed Fw in the pulse initial reverse feed period Tair from time t1 to t2 is Figure 1 The pulse initial reverse feed speed setting signal Farr determines the pulse initial reverse feed speed Fa. If the pulse initial reverse feed period Tair ends at time t2, the pull feed speed Fw becomes as shown in (A) of the figure. Figure 1The pulse forward feed speed Fas is determined by the pulse forward feed speed setting signal Fasr, and the forward feed is performed at a fixed feed speed. The pull feed speed Fw is not corrected. On the other hand, as shown in (G) of the figure, the push feed speed Fwp is determined by the pulse arc welding period Ta after time t1. Figure 1 The pulse advances the speed determined by the feed speed setting signal Fapr, and feeds forward. Figure 1 The push feed speed correction circuit FPH selects any one of processing 1) to 3) to perform correction control on the push feed speed Fwp. In the case of selecting processing 1), the push feed speed Fwp is subjected to variable speed control so that Figure 1 The value of the capacity signal Wb of the intermediate wire storage portion is equal to the target value. In the case of selecting processing 2), the feed speed Fwp is only Figure 1 When the error between the value of the capacity signal Wb of the intermediate wire storage portion and the target value is outside the given range, correction control is performed. In the case of selecting process 3), the feed speed Fwp becomes a fixed speed because no correction control is performed. Here, during the pulse initial reverse feed period Tair from time t1 to time t2, the feed speed Fwp can be set to Figure 1 The short-circuit arc advances to the value determined by the speed setting signal Fcpr.

[0283] When the pulse arc welding period Ta begins at time t1, the welding current Iw enters the state of Figure 1 The pulse initial current period Tas is determined by the pulse initial current period setting signal Tasr. The welding current Iw in the pulse initial current period Tas from time t1 to t3 is Figure 1 The pulse initial current Ias is determined by the pulse initial current setting signal Iasr.

[0284] As shown in (B) of the figure, during the predetermined steady-state peak rise period Tu from time t3 to t4, the switch is turned on. Figure 1 The peak current setting signal Ipr is used to set the peak current value Ip. During the predetermined steady-state peak period Tp from time t4 to time t5, the peak current value Ip is turned on. During the predetermined steady-state peak falling period Tpd from time t5 to time t6, the peak current value Ip is turned on. Figure 1 The base current setting signal Ibr is used to set the transition current to a lower base current value Ib. During the predetermined base period Tb from time t6 to t7, the welding power source is turned on with the base current value Ib. During the pulse arc welding period Ta, the welding power source has a constant current characteristic. Therefore, the welding current Iw is Figure 1The welding voltage Vw is set by the pulse current setting signal Iar. As shown in (C) of the figure, the welding voltage Vw becomes a waveform similar to the current waveform. The period from time t3 to t7 is one pulse period Tf. In order to maintain the arc length at an appropriate value, the peak current Ip and the base current Ib are modulated (current modulation control) so that the average value of the welding voltage Vw is equal to the target value. As a modulation control method other than this, there are frequency modulation control that modulates the pulse period Tf, peak period modulation control that modulates the peak period Tp, etc. In any modulation control, the welding state can be improved by setting it to a state in which one droplet is transferred during one pulse period Tf, that is, the so-called one droplet transfer state per one pulse period. Examples of the numerical values ​​of each parameter are Tu=1.5ns, Tp=0.2ms, Tpd=1.5ms, Tb=7ms, Ip=350~450A and Ib=30~80A.

[0285] The pulse arc welding period Ta includes a plurality of pulse cycles Tf. The pulse cycle Tf is, for example, about 10 ms. The pulse arc welding period Ta is, for example, about 50 to 500 ms.

[0286] At time t1, when the pulse arc welding period Ta begins, the arc length is very short because the short circuit has just been released. The pulse initial reverse feed period Tair starting from time t1 is set so that the arc length is extended to the desired value. By turning on the initial peak current Ip from time t3 after the arc length is extended to the desired value, the droplet formation state can be stabilized from the initial cycle. Thus, the switch from the short-circuit transition arc welding period Tc to the pulse arc welding period Ta can be smooth. Therefore, the pulse initial reverse feed period Tair and the pulse initial reverse feed speed Fa are set to values ​​that extend the arc length to the desired value. To this end, the pulse initial reverse feed period Tair is set to at least Figure 2 The reverse feed deceleration period Trd is longer than the reverse feed deceleration period Trd. In addition, the pulse initial reverse feed speed Fa is longer than Figure 2 The reverse feed peak Wrp is small. For example, Tar = 3ms, Fa = -6m / min.

[0287] Furthermore, the pulse initial reverse feed period Tair can be set to a period during which the welding voltage Vw rises to the reference voltage value. The welding voltage Vw is proportional to the arc length. Therefore, by setting the reference voltage value to a value corresponding to the desired arc length, the pulse initial reverse feed period Tair can be automatically set, and the parameter setting operation becomes easy.

[0288] Furthermore, during the pulse initial reverse feed period Tair, the welding current Iw is maintained at the pulse initial current Ias set to a value greater than the base current Ib and smaller than the peak current Ip. The pulse initial current Ias is turned on during the predetermined pulse initial current period Tas. It is set to Tar<Tas. By setting the pulse initial current Ias to a value greater than the base current Ib, the melting of the welding wire is promoted, thereby preventing the welding wire and the base material from being short-circuited again during the period when the arc length is short. For this reason, sputtering when switching to the pulse arc welding period Ta can be reduced, which can be further stabilized. By setting the pulse initial current Ias to a value smaller than the peak current Ip, the arc can be suppressed from igniting rapidly, and the arc length becomes longer than the expected value. For example, Tas=5ms, Ias=100A.

[0289] After the pulse initial reverse feed period Tair has passed, the initial peak current Ip is turned on. That is, Tar is set to be less than Tas. By starting the initial pulse cycle after the pulse initial reverse feed period Tair has ended, the droplet transfer state in the initial pulse cycle can be reliably stabilized.

[0290] The arc welding method implemented by the above-mentioned embodiment has the following steps, for example. (1) Feeding the welding wire by push-pull feed control, wherein the push-pull feed control is based on a push-side feed motor that performs forward feed rotation and a pull-side feed motor that performs forward feed rotation and reverse feed rotation. (2) An intermediate welding wire storage section that temporarily stores (a portion of) the welding wire is provided between the feed paths of the push-side feed motor and the pull-side feed motor, and the push feed speed of the push-side feed motor or the pull feed speed of the pull-side feed motor is corrected based on the wire storage capacity of the intermediate welding wire storage section, thereby feeding the welding wire. (3) Welding is performed by alternately switching between the following periods: a period in which the welding wire is fed forward by the forward feed rotation of the push-side feed motor and the forward feed rotation of the pull-side feed motor, and the peak current and the base current are connected to perform pulse arc welding; and a period in which the welding wire is fed forward and reversely by the forward feed rotation of the push-side feed motor and the forward and reverse feed rotation of the pull-side feed motor, and the short-circuit current and the arc current are connected to perform short-circuit transfer arc welding.

[0291] During the short-circuit transfer arc welding (short-circuit transfer arc welding period), the waveform parameter of the pull-feed speed is corrected based on the wire retraction amount. The waveform parameter is, for example, a forward feed peak value and / or a reverse feed peak value. In addition, the waveform parameter is a forward feed peak value when the wire retraction amount is larger than the target value, and is a reverse feed peak value when the wire retraction amount is smaller than the target value. In addition, the waveform parameter is a reverse feed peak value when the wire retraction amount is larger than the target value, and is a forward feed peak value when the wire retraction amount is smaller than the target value.

[0292] In the past, in an arc welding method in which welding is performed by alternately switching between a pulse arc welding period in which the welding wire is fed forward and a short circuit transition arc welding period in which the welding wire is fed forward and reversely, during the short circuit transition arc welding period, the forward feed period and the reverse feed period are switched synchronously with the occurrence timing of the short circuit period and the arc period. At this time, since the short circuit transition arc welding period becomes a repetition in a relatively short cycle, the welding state becomes a transition state. As a result, since the time ratio of the short circuit period and the arc period changes, the time ratio of the forward feed period and the reverse feed period also changes, and thus the average feed speed (average value of the pull feed speed) of the welding wire changes. Since the amount of deposit changes when the average feed speed changes, the welding quality deteriorates.

[0293] On the other hand, in the present embodiment, the time ratio between the forward feed period and the reverse feed period changes and the average value of the pull feed speed changes, which will produce a difference with the fixed speed of the push feed speed. As a result, an error occurs between the wire storage capacity of the intermediate wire storage section and the target value. By correcting the forward feed peak value and / or the reverse feed peak value so that the error becomes 0, the average values ​​of the pull feed speed and the push feed speed can be made equal. For this reason, the average value of the pull feed speed can be returned to a given value. Furthermore, even if the welding state is a transition state, in the present embodiment, the waveform parameters of the pull feed speed are directly corrected, so that the feeding of the welding wire can be made high-precision and stable.

[0294] More preferably, according to the present embodiment, during the pulse arc welding, the push feed speed and the pull feed speed based on the amount of wire stored are not corrected. Depending on welding conditions such as the material of the welding wire and the average welding current value, if the correction control is performed during the pulse arc welding, the welding state may become unstable. In such a case, by not performing the correction control during the pulse arc welding, the welding state can be stabilized.

[0295] Further preferably, according to the present embodiment, during the pulse arc welding, the push feed speed is corrected based on the wire retraction amount. By performing correction control also during the pulse arc welding according to welding conditions such as the material of the welding wire and the average welding current value, the welding state can be stabilized. The object of correction control is more preferably the push feed speed than the pull feed speed. This is because the feed speed of the welding wire close to the arc generating part can be fixed. Furthermore, when the wire retraction amount is outside a given range, the push feed speed is corrected based on the wire retraction amount. This can further stabilize the welding state.

Claims

1. An arc welding method, characterized in that: The process includes the following steps: Feeding the welding wire by push-pull feed control based on a push-side feed motor that performs forward feed rotation and a pull-side feed motor that performs forward feed rotation and reverse feed rotation; temporarily accommodating the welding wire in an intermediate welding wire accommodating portion provided between the feeding paths of the push-side feeding motor and the pull-side feeding motor; feeding the welding wire by correcting the push feed speed of the push-side feed motor or the pull feed speed of the pull-side feed motor based on the wire storage capacity in the intermediate welding wire storage section; and The pulse arc welding period and the short circuit transfer arc welding period are alternately switched, wherein during the pulse arc welding period, the welding wire is fed forward by the forward feed rotation of the push side feed motor and the forward feed rotation of the pull side feed motor, and the peak current and the base current are connected to perform pulse arc welding, and during the short circuit transfer arc welding period, the welding wire is fed forward and reversely by the forward feed rotation of the push side feed motor and the forward and reverse feed rotation of the pull side feed motor, and the short circuit current and the arc current are connected to perform short circuit transfer arc welding, During the short-circuit transfer arc welding, the waveform parameters of the feed speed are corrected based on the wire retraction capacity. The waveform parameter is at least one of a forward feed peak value and a reverse feed peak value. During the pulse initial reverse feed period, the welding current is maintained at a pulse initial current set to a value greater than the base current and smaller than the peak current.

2. The arc welding method according to claim 1, characterized in that: The waveform parameter is a forward feed peak value when the wire retraction amount is larger than the target value, and is a reverse feed peak value when the wire retraction amount is smaller than the target value.

3. The arc welding method according to claim 1, characterized in that: The waveform parameter is a reverse feed peak value when the wire retraction amount is larger than the target value, and is a forward feed peak value when the wire retraction amount is smaller than the target value.

4. The arc welding method according to any one of claims 1 to 3, characterized in that: During the pulse arc welding period, the push feed speed and the pull feed speed are not corrected based on the wire storage amount.

5. The arc welding method according to any one of claims 1 to 3, characterized in that: During the pulse arc welding period, the feed speed is corrected based on the wire retraction amount.

6. The arc welding method according to any one of claims 1 to 3, characterized in that: During the pulse arc welding period, when the wire retraction amount is outside a predetermined range, the feed speed is corrected based on the wire retraction amount.

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