JP7272740B2 - Arc welding control method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding control method in which the welding wire is forwardly fed during the arc period between the welding wire and the base material, and the welding wire is reversely fed during the short-circuit period for welding.

In general consumable electrode arc welding, welding is performed by feeding a welding wire, which is a consumable electrode, at a constant speed to generate an arc between the welding wire and a base material. In consumable electrode arc welding, the welding wire and the base material are often welded to alternate short-circuit periods and arc periods.

In order to further improve the welding quality, there has been proposed a forward/reverse feed arc welding method in which welding wire is alternately switched between forward feed and reverse feed (see, for example, Patent Document 1). Compared to the conventional technology with a constant feed speed, this forward/reverse feed arc welding method can stabilize the cycle of repetition of the short circuit and the arc, thereby reducing the amount of spatter generated and improving the appearance of the bead. Welding quality can be improved.

Japanese Patent Application Laid-Open No. 2018-1270

Many brands of welding wire are available for arc welding of steel materials. Since these welding wires have different compositions, they also have different viscosities. In forward/reverse feed arc welding, if a welding wire with relatively low viscosity is used, there is a problem that the amount of spatter generated immediately after the arc is generated increases.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an arc welding control method capable of always reducing the amount of spatter generated in forward/reverse feed arc welding without being affected by the viscosity of the welding wire.

In order to solve the above-mentioned problems, the invention of claim 1 is
During the arc period between the welding wire and the base material, the feed speed starts to switch from the reverse feed peak value to the forward feed peak value, and during the short-circuit period, the feed speed changes from the forward feed peak value to the reverse feed peak value. start switching,
reducing the welding current to a low level current value upon detection of constriction of the welding wire droplet during the short circuit period;
In the arc welding control method for welding by increasing the welding current from the low level current value after the arc period is started,
By detecting the feeding speed when switching from the reverse feeding peak value to the forward feeding peak value and setting the detected feeding speed to 0 as the timing for increasing the welding current. , regardless of the size of the feed resistance, the increase timing is made to coincide with the time when the feed speed becomes 0;
An arc welding control method characterized by:

Advantageous Effects of Invention According to the present invention, in forward/reverse feed arc welding, the amount of spatter generated can always be reduced without being affected by the viscosity of the welding wire.

1 is a block diagram of a welding power source for carrying out an arc welding control method according to Embodiment 1 of the present invention; FIG. 2 is a timing chart of each signal in the welding power source of FIG. 1, showing the arc welding control method according to Embodiment 1 of the present invention; FIG. 7 is a block diagram of a welding power source for carrying out an arc welding control method according to Embodiment 2 of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is a block diagram of a welding power source for implementing an arc welding control method according to Embodiment 1 of the present invention. Each block will be described below with reference to FIG.

The power supply main circuit PM receives a commercial power supply (not shown) such as a three-phase 200V power supply, performs output control by inverter control or the like according to an error amplification signal Ea, which will be described later, and outputs an output voltage E. Although not shown, the power supply main circuit PM is driven by a primary rectifier that rectifies the commercial power supply, a smoothing capacitor that smoothes the rectified direct current, and the error amplification signal Ea that converts the smoothed direct current into high-frequency alternating current. A high-frequency transformer that steps down high-frequency alternating current to a voltage value suitable for welding, and a secondary rectifier that rectifies the stepped-down high-frequency alternating current to direct current.

The reactor WL smoothes the welding current Iw. The inductance value of this reactor WL is, for example, 100 μH.

The feed motor WM feeds the welding wire 1 at a feed speed Fw by alternately repeating forward feed and reverse feed upon receiving a feed control signal Fc, which will be described later. A motor with fast transient response is used for the feeding motor WM. In some cases, the feed motor WM is installed near the tip of the welding torch 4 in order to speed up the rate of change of the feed speed Fw of the welding wire 1 and the reversal of the feed direction. In some cases, two feeding motors WM are used to form a push-pull type feeding system.

The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2 . A welding voltage Vw is applied between a power supply tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is applied. Shielding gas is jetted from the tip of the welding torch 4 to shield the arc 3 from the atmosphere.

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

The voltage error amplifier circuit EV receives the output voltage setting signal Er and the output voltage detection signal Ed, and amplifies the error between the output voltage setting signal Er(+) and the output voltage detection signal Ed(-). , output the voltage error amplification signal Ev.

A current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. A voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The short-circuit determination circuit SD receives the voltage detection signal Vd as an input, and when this value is less than a predetermined short-circuit determination value (about 10 V), it determines that there is a short-circuit period and becomes High level. It determines that it is in the arc period and outputs a short-circuit determination signal Sd that becomes Low level.

A forward acceleration period setting circuit TSUR outputs a predetermined forward acceleration period setting signal Tsur.

A forward deceleration period setting circuit TSDR outputs a predetermined forward deceleration period setting signal Tsdr.

A reverse acceleration period setting circuit TRUR outputs a predetermined reverse acceleration period setting signal Trur.

The reverse deceleration period setting circuit TRDR outputs a predetermined reverse deceleration period setting signal Trdr.

A forward peak value setting circuit WSR outputs a predetermined forward peak value setting signal Wsr. The forward feed peak value setting signal Wsr is set as a value corresponding to the average feed speed (average welding current value).

The reverse feed peak value setting circuit WRR outputs a predetermined reverse feed peak value setting signal Wrr. The reverse feeding peak value setting signal Wrr is set as a value corresponding to the average feeding speed (average welding current value).

The feeding speed setting circuit FR receives the forward acceleration period setting signal Tsur, the forward deceleration period setting signal Tsdr, the reverse acceleration period setting signal Trur, the reverse deceleration period setting signal Trdr, and the The forward feed peak value setting signal Wsr, the reverse feed peak value setting signal Wrr, and the short circuit determination signal Sd are input, and the feed speed pattern generated by the following processing is output as the feed speed setting signal Fr. When this feeding speed setting signal Fr is 0, it is in a stopped state, when it is larger than 0, it is a forward feeding period, and when it is smaller than 0, it is a reverse feeding period.
1) During the normal feeding acceleration period Tsu determined by the normal feeding acceleration period setting signal Tsu, the feeding speed setting signal Fr for accelerating from 0 to the positive forward feeding peak value Wsp determined by the normal feeding peak value setting signal Wsr is output. .
2) Subsequently, during the forward feeding peak period Tsp, the feeding speed setting signal Fr for maintaining the forward feeding peak value Wsp is output.
3) When the short-circuit determination signal Sd changes from Low level (arc period) to High level (short-circuit period), the normal feed deceleration period Tsd determined by the normal feed deceleration period setting signal Tsdr is entered, and the normal feed peak value Wsp is changed. A feeding speed setting signal Fr for decelerating to 0 is output.
4) Subsequently, during the reverse feeding acceleration period Tru determined by the reverse feeding acceleration period setting signal Trur, the feeding speed setting signal Fr accelerates from 0 to the negative reverse feeding peak value Wrp determined by the reverse feeding peak value setting signal Wrr. to output
5) Subsequently, during the reverse feed peak period Trp, the feed speed setting signal Fr for maintaining the reverse feed peak value Wrp is output.
6) When the short circuit determination signal Sd changes from High level (short-circuit period) to Low level (arc period), the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr is entered, and the reverse feed peak value Wrp A feeding speed setting signal Fr for decelerating to 0 is output.
7) By repeating the above 1) to 6), a feeding speed setting signal Fr having a feeding pattern that changes in positive and negative trapezoidal waveforms is generated.

A feeding speed detection circuit FD receives the encoder signal Es from the feeding motor WM and outputs a feeding speed detection signal Fd.

A feeding control circuit FC receives the feeding speed setting signal Fr and the feeding speed detection signal Fd, and controls the feeding speed detection signal Fd so that the value of the feeding speed setting signal Fr is equal to the value of the feeding speed detection signal Fd. A feed control signal Fc for controlling the feed speed Fw is output to the feed motor WM.

A 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 at least 50 times larger than the short-circuit load (about 0.01 to 0.03Ω). When this current reducing resistor R is inserted into the welding current conduction path, the energy accumulated in the reactor component of the reactor WL and the welding cable is rapidly discharged.

The transistor TR is connected in parallel with the current reducing resistor R, and is controlled to be on or off according to a drive signal Dr, which will be described later.

A constriction detection circuit ND receives the short-circuit determination signal Sd, the voltage detection signal Vd, and the current detection signal Id as inputs, and detects the voltage detection signal Vd when the short-circuit determination signal Sd is at High level (short-circuit period). When the voltage rise value reaches the reference value, it is determined that the state of formation of the constriction has reached the reference state, and becomes High level. When the short circuit determination signal Sd changes to Low level (arc period), it becomes Low level. output the signal Nd. Alternatively, the constriction detection signal Nd may be changed to a high level at the time when the differential value of the voltage detection signal Vd during the short-circuit period reaches a corresponding reference value. Furthermore, the value of the voltage detection signal Vd is divided by the value of the current detection signal Id to calculate the resistance value of the droplet. It may be changed to High level.

The low level current setting circuit ILR outputs a predetermined low level current setting signal Ilr. A current comparison circuit CM receives the low-level current setting signal Ilr and the current detection signal Id as inputs, and generates a current comparison signal Cm that becomes High level when Id<Ilr and becomes Low level when Id≧Ilr. Output.

The drive circuit DR receives the current comparison signal Cm and the constriction detection signal Nd as inputs, and changes to Low level when the constriction detection signal Nd changes to High level. A drive signal Dr that changes to High level is output to the base terminal of the transistor TR. Therefore, when the constriction is detected, the driving signal Dr becomes Low level, the transistor TR is turned off, and the current reduction resistor R is inserted in the welding current path, so that the welding current Iw is rapidly reduced. Then, when the value of the welding current Iw, which has suddenly decreased, decreases to the value of the low-level current setting signal Ilr, the drive signal Dr becomes High level, and the transistor TR is turned on, so that the current reducing resistor R is short-circuited and normally state.

The current control setting circuit ICR receives the short-circuit determination signal Sd, the low-level current setting signal Ilr, and the constriction detection signal Nd, performs the following processing, and outputs a current control setting signal Icr.
1) When the short circuit determination signal Sd is at Low level (arc period), the current control setting signal Icr that becomes the low level current setting signal Ilr is output.
2) When the short-circuit determination signal Sd changes to a high level (short-circuit period), the current is set to a predetermined initial current set value during a predetermined initial period, and then to a predetermined short-circuit peak set value with a predetermined short-circuit slope. and output a current control setting signal Icr that maintains that value.
3) After that, when the constriction detection signal Nd changes to High level, the current control setting signal Icr having the value of the low level current setting signal Ilr is output.

A 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 current control setting signal Icr(+) and the current detection signal Id(-), and outputs the current It outputs an error amplification signal Ei.

A current drop time setting circuit TDR outputs a predetermined current drop time setting signal Tdr. The current drop time setting signal Tdr is set as a value corresponding to the average feed speed (average welding current value).

The small current period circuit STD receives the short-circuit discrimination signal Sd and the current drop time setting signal Tdr, and is determined by the current drop time setting signal Tdr from the time when the short-circuit discrimination signal Sd changes to Low level (arc period). It outputs a small current period signal Std that becomes High level when time elapses and becomes Low level when the short-circuit determination signal Sd becomes High level (short-circuit period).

A power supply characteristics switching circuit SW receives as inputs the current error amplification signal Ei, the voltage error amplification signal Ev, the short-circuit determination signal Sd, the reverse deceleration period setting signal Trdr, and the small current period signal Std. , performs the following processing and outputs an error amplified signal Ea.
1) After the short-circuit determination signal Sd changes to High level (short-circuit period), the short-circuit determination signal Sd changes to Low level (arc period), and the reverse deceleration period determined by the reverse deceleration period setting signal Trdr has elapsed. During the period up to the point in time, the current error amplification signal Ei is output as the error amplification signal Ea.
2) During the subsequent high-current arc period, the voltage error amplification signal Ev is output as the error amplification signal Ea.
3) Output the current error amplification signal Ei as the error amplification signal Ea during the small current arc period in which the small current period signal Std becomes High level during the subsequent arc period.
With this circuit, the characteristics of the welding power source are constant current characteristics during the short-circuit period, reverse deceleration period, and small current arc period, and constant voltage characteristics during the other large current arc period.

FIG. 2 is a timing chart of each signal in the welding power source of FIG. 1 showing the arc welding control method according to Embodiment 1 of the present invention. (A) shows the time change of the feed speed Fw, (B) shows the time change of the welding current Iw, (C) shows the time change of the welding voltage Vw, and (D ) shows the temporal change of the short circuit determination signal Sd, and (E) shows the temporal change of the small current period signal Std. The operation of each signal will be described below with reference to FIG.

The feeding speed Fw shown in FIG. 1A is controlled by the value of the feeding speed setting signal Fr output from the feeding speed setting circuit FR shown in FIG. The feeding speed Fw is defined by the forward acceleration period Tsu determined by the forward acceleration period setting signal Tsur shown in FIG. 1, the reverse feed peak period Trp that continues until an arc occurs, and the reverse feed determined by the reverse feed deceleration period setting signal Trdr in FIG. It is formed from the deceleration period Trd. Further, the forward peak value Wsp is determined by the forward peak value setting signal Wsr in FIG. 1, and the reverse peak value Wrp is determined by the reverse peak value setting signal Wrr in FIG. As a result, the feeding speed setting signal Fr has a feeding pattern that changes in a positive and negative substantially trapezoidal waveform.

[Operation during short-circuit period from time t1 to t4]
When a short circuit occurs at time t1 during the forward feed peak period Tsp, the welding voltage Vw rapidly decreases to a short-circuit voltage value of several volts as shown in FIG. The short-circuit determination signal Sd changes to High level (short-circuit period). In response to this, a transition is made to a predetermined normal feed deceleration period Tsd from time t1 to t2, and the feed speed Fw is reduced from the normal feed peak value Wsp to 0 as shown in FIG. . For example, the forward deceleration period Tsd is set to 1 ms.

As shown in FIG. 4A, the feeding speed Fw enters a predetermined reverse feeding acceleration period Tru from time t2 to t3, and accelerates from 0 to the reverse feeding peak value Wrp. During this period, the short-circuit period continues. For example, the reverse acceleration period Tru is set to 1 ms.

When the reverse feeding acceleration period Tru ends at time t3, the feeding speed Fw enters the reverse feeding peak period Trp and becomes the reverse feeding peak value Wrp, as shown in FIG. The reverse feed peak period Trp continues until an arc occurs at time t4. Therefore, the period from time t1 to t4 is the short-circuit period. The reverse transmission peak period Trp is not a predetermined value, but is approximately 4 ms. For example, the backward feed peak value Wrp is set to -60 m/min.

As shown in FIG. 4B, the welding current Iw during the short-circuit period from time t1 to t4 has a predetermined initial current value during the predetermined initial period. After that, the welding current Iw increases at a predetermined short-circuiting slope, and when it reaches a predetermined short-circuiting peak value, the value is maintained.

As shown in (C) of the same figure, the welding voltage Vw rises from around the time when the welding current Iw reaches the short-circuit peak value. This is because constriction is gradually formed in the droplet at the tip of the welding wire 1 due to the action of the pinch force due to the welding wire 1 being reversed and the welding current Iw.

After that, when the voltage rise value of the welding voltage Vw reaches the reference value, it is determined that the constriction formation state has reached the reference state, and the constriction detection signal Nd in FIG. 1 changes to High level.

In response to the constriction detection signal Nd becoming High level, the drive signal Dr in FIG. 1 becomes Low level, so the transistor TR in FIG. It is inserted into the power line. At the same time, the current control setting signal Icr of FIG. 1 decreases to the value of the low level current setting signal Ilr. As a result, the welding current Iw sharply decreases from the short-circuit peak value to the low level current value, as shown in FIG. When the welding current Iw decreases to the low level current value, the drive signal Dr returns to the high level, so that the transistor TR is turned on and the current reducing resistor R is short-circuited. As shown in (B) of the same figure, the welding current Iw remains at the low level current setting signal Ilr from the current control setting signal Icr. Maintain a low level current value. Therefore, the transistor TR is turned off only during the period from when the constriction detection signal Nd changes to High level to when the welding current Iw decreases to the low level current value. As shown in (C) of the figure, the welding voltage Vw decreases once and then rises sharply because the welding current Iw becomes smaller. Each parameter mentioned above is set to the following values, for example. Initial current = 40A, initial period = 0.5ms, slope at short circuit = 180A/ms, peak value at short circuit = 400A, low level current value = 50A.

[Operation during arc period from time t4 to t7]
At time t4, the constriction progresses due to the pinch force due to the reverse feeding of the welding wire and the application of the welding current Iw, and an arc is generated. As shown in FIG. , the short-circuit determination signal Sd changes to the Low level (in the arc period), as shown in FIG. In response to this, a transition is made to a predetermined reverse feed deceleration period Trd from time t4 to t5, and the feed speed Fw is reduced from the reverse feed peak value Wrp to 0 as shown in FIG. . For example, the reverse deceleration period Trd is set to 1 ms.

When the reverse feed deceleration period Trd ends at time t5, the forward feed acceleration period Tsu, which is predetermined from time t5 to t6, is entered. During the normal feed acceleration period Tsu, the feed speed Fw is accelerated from 0 to the forward feed peak value Wsp, as shown in FIG. The arc period continues during this period. For example, the forward acceleration period Tsu is set to 1 ms.

When the normal feeding acceleration period Tsu ends at time t6, the feeding speed Fw enters the normal feeding peak period Tsp and reaches the normal feeding peak value Wsp as shown in FIG. The arc period continues during this period. The forward peak period Tsp continues until a short circuit occurs at time t7. Therefore, the period from time t4 to t7 is the arc period. Then, when a short circuit occurs, the operation returns to time t1. Although the forward transmission peak period Tsp is not a predetermined value, it is approximately 4 ms. For example, the forward feed peak value Wsp is set to 70 m/min.

When the arc occurs at time t4, the welding voltage Vw rapidly increases to several tens of volts as shown in FIG. On the other hand, as shown in FIG. 4B, the welding current Iw continues at a low level current value during the reverse feed deceleration period Trd from time t4 to t5. After that, the welding current Iw rapidly increases from time t5 to reach a peak value, and then gradually decreases to a large current value. Therefore, the timing (time t5) at which the welding current Iw increases after the arc is generated at time t4 is the end of the reverse feed deceleration period Trd when the feed speed when switching from reverse feed to forward feed is 0. becomes.

During the high current arc period from time t5 to time t61, feedback control of the welding power source is performed by the voltage error amplification signal Ev of FIG. 1, so that constant voltage characteristics are obtained. Therefore, the value of the welding current Iw during the high current arc period varies depending on the arc load.

At time t61 when the current drop time determined by the current drop time setting signal Tdr shown in FIG. 1 has passed since the arc was generated at time t4, the small current period signal Std changes to a high level as shown in FIG. do. In response to this, the welding power source is switched from the constant voltage characteristic to the constant current characteristic. As a result, the welding current Iw drops to a low-level current value, as shown in FIG. 1B, and this value is maintained until time t7 when a short circuit occurs. Similarly, the welding voltage Vw also decreases, as shown in FIG. The small current period signal Std returns to Low level when a short circuit occurs at time t7.

According to the first embodiment described above, the timing of increasing the welding current from the low level current value after the arc period is started is when the feed speed when switching from reverse feeding to forward feeding becomes 0. and That is, the welding current increase timing is set at the end of the reverse feed deceleration period. When forward/reverse feed arc welding is performed using a welding wire with a low viscosity among welding wires for steel, the following welding conditions occur depending on the timing of increasing the welding current after arc generation.
(1) When the Welding Current Increase Timing is in the Middle of the Reverse Feed Deceleration Period In this case, the welding current increases while the welding wire is still being reverse fed. As the welding current increases, the welding wire tip melts to form a droplet. With a welding wire having a low viscosity, when droplets are formed while running in the opposite direction, part of the droplets scatters as spatter. A welding wire with a high viscosity will not spatter even if droplets are formed during reversing.
(2) When the Welding Current Increase Timing is at the End of the Reverse Feed Deceleration Period (Embodiment 1)
In this case, the welding current increases when the welding wire feed speed is zero. As the welding current increases, the welding wire tip melts to form a droplet. Therefore, droplets are gradually formed while the feeding speed is gradually accelerated from 0, and spatter does not occur regardless of the viscosity of the welding wire.
(3) When the Welding Current Increase Timing is in the Middle of the Forward Feeding Acceleration Period In this case, the welding current increases while the welding wire is being forward fed. Therefore, since the welding wire is forward-fed before a droplet is formed yet, the probability of short-circuiting again increases regardless of the viscosity of the welding wire. If re-shorting occurs, the welding state becomes unstable.

Therefore, in the invention according to the first embodiment, in forward/reverse feed arc welding, the amount of spatter generated can always be reduced without being affected by the viscosity of the welding wire. In the first embodiment, the welding current is increased when the feed speed becomes 0. However, even if there is a deviation of about ±0.2 ms, the increase in spatter is small, so it is included in the present embodiment.

[Embodiment 2]
In the second embodiment of the invention, after the arc period is started, the timing of increasing the welding current from the low level current value is detected by detecting the feed speed when switching from reverse feed to forward feed. It is assumed that the feeding speed becomes zero.

FIG. 3 is a block diagram of a welding power source for implementing an arc welding control method according to Embodiment 2 of the present invention. This figure corresponds to FIG. 1 described above, and the same blocks are denoted by the same reference numerals, and description thereof will not be repeated. 1, the power supply characteristics switching circuit SW of FIG. 1 is replaced with a second power supply characteristics switching circuit SW2. This block will be described below with reference to the same figure.

A second power supply characteristic switching circuit SW2 receives the current error amplification signal Ei, the voltage error amplification signal Ev, the short circuit determination signal Sd, the feeding speed detection signal Fd, and the small current period signal Std. , the following processing is performed to output the error amplification signal Ea.
1) During the period from when the short-circuit determination signal Sd changes to High level (short-circuit period) to when the feed speed detection signal Fd becomes 0 after the short-circuit determination signal Sd changes to Low level (arc period) , outputs the current error amplification signal Ei as the error amplification signal Ea.
2) During the subsequent high-current arc period, the voltage error amplification signal Ev is output as the error amplification signal Ea.
3) Output the current error amplification signal Ei as the error amplification signal Ea during the small current arc period in which the small current period signal Std becomes High level during the subsequent arc period.
With this circuit, the characteristics of the welding power source are constant current characteristics during the short-circuit period, the actually measured reverse feed deceleration period, and the low current arc period, and constant voltage characteristics during the other large current arc periods.

The timing chart of each signal in FIG. 3 is omitted because it is the same as in FIG. 2 described above. However, the timing at which the welding current Iw increases at time t4 shown in FIG. In Embodiment 1, the timing for increasing the welding current from the low level current value after the arc period is started is the time when the period determined by the predetermined reverse running deceleration period setting signal Trdr ends. On the other hand, in the second embodiment, the increase timing is the period until the feeding speed detection signal Fd becomes zero. When the feeding resistance of the welding wire is small, both substantially match. However, as the feed resistance increases, the difference between the two increases. Therefore, in the second embodiment, regardless of the magnitude of the feeding resistance, the timing of increase can be made coincident with the point at which the feeding speed becomes zero. As a result, the amount of spatter generated can be minimized.

1 welding wire
2 Base material
3 arcs
4 welding torch
5 Feed roll CM Current comparison circuit Cm Current comparison signal DR Drive circuit Dr Drive signal E Output voltage Ea Error amplification signal ED Output voltage detection circuit Ed Output voltage detection signal EI Current error amplification circuit Ei Current error amplification signal ER Output voltage setting circuit Er Output voltage setting signal Es Encoder signal EV (from feeding motor) Voltage error amplification circuit Ev Voltage error amplification signal FC Feeding control circuit Fc Feeding control signal FD Feeding speed detection circuit Fd Feeding speed detection signal FR Feeding Speed setting circuit Fr Feeding speed setting signal Fw Feeding speed ICR Current control setting circuit Icr Current control setting signal ID Current detection circuit Id Current detection signal ILR Low level current setting circuit Ilr Low level current setting signal Iw Welding current ND Constriction detection circuit Nd Constriction detection signal PM Power supply main circuit R Current reduction resistor SD Short-circuit discrimination circuit Sd Short-circuit discrimination signal STD Small current period circuit Std Small current period signal SW Power supply characteristic switching circuit SW2 Second power supply characteristic switching circuit TDR Current drop time setting circuit Tdr Current drop time setting signal TR Transistor Trd Reverse transfer deceleration period TRDR Reverse transfer deceleration period setting circuit Trdr Reverse transfer deceleration period setting signal Trp Reverse transfer peak period Tru Reverse transfer acceleration period TRUR Reverse transfer acceleration period setting circuit Trur Reverse transfer acceleration period setting signal Tsd Forward deceleration period TSDR Forward deceleration period setting circuit Tsdr Forward deceleration period setting signal Tsp Forward peak period Tsu Forward acceleration period TSUR Forward acceleration period setting circuit Tsur Forward acceleration period setting signal VD Voltage detection circuit Vd Voltage detection Signal Vw Welding voltage WL Reactor WM Feed motor Wrp Reverse feeding peak value WRR Reverse feeding peak value setting circuit Wrr Reverse feeding peak value setting signal Wsp Forward feeding peak value WSR Forward feeding peak value setting circuit Wsr Forward feeding peak value setting signal

Claims (1)

During the arc period between the welding wire and the base material, the feed speed starts to switch from the reverse feed peak value to the forward feed peak value, and during the short-circuit period, the feed speed changes from the forward feed peak value to the reverse feed peak value. start switching,
reducing the welding current to a low level current value upon detection of constriction of the welding wire droplet during the short circuit period;
In the arc welding control method for welding by increasing the welding current from the low level current value after the arc period is started,
By detecting the feeding speed when switching from the reverse feeding peak value to the forward feeding peak value and setting the detected feeding speed to 0 as the timing for increasing the welding current. , regardless of the size of the feed resistance, the increase timing is made to coincide with the time when the feed speed becomes 0;
An arc welding control method characterized by:

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