KR102190857B1 - Arc welding control method - Google Patents

Abstract

Improves the stability of arc welding in which the forward and reverse feeds of the welding wire are periodically repeated. An arc welding control method in which the forward and reverse transmission periods of the feed rate (Fw) are periodically repeated, the constant voltage is controlled so that the output of the welding power source becomes equal to the voltage target value (Ecr), and the short-circuit period and the arc period are repeatedly welded. In the following, during the forward transmission period Tas during the arc period, the voltage target value Ecr is decreased with the passage of time. Thereby, even if the arc length is shortened and the welding voltage Vw decreases during the forward transmission period Tas during the arc period, the welding current Iw can be reduced, so that the timing of occurrence of a short circuit can be made constant, and the welding state It can improve the stability of.

Description

Arc welding control method {ARC WELDING CONTROL METHOD}

The present invention is an arc welding control method in which the forward and reverse transmission periods of the feed rate are periodically repeated, constant voltage is controlled so that the output of the welding power source becomes equal to the voltage target value, and the short circuit period and the arc period are repeatedly welded. It is about.

In general consumable electrode type arc welding, welding is performed by feeding a welding wire as a consumable electrode at a constant speed and generating an arc between the welding wire and a base material. In consumable electrode arc welding, the welding wire and the base material are often in a welding state in which the short circuit period and the arc period are alternately repeated.

In order to further improve the welding quality, a method of periodically repeatedly welding the forward and reverse transmission of the welding wire has been proposed (for example, see Patent Document 1). Hereinafter, this welding method will be described.

3 is a waveform diagram in a welding method in which forward and reverse feed of the feed rate are periodically repeated. FIG. 3(A) shows the waveform of the feeding speed (Fw), FIG. 3(B) shows the waveform of the welding current Iw, and FIG. 3(C) shows the waveform of the welding voltage (Vw). 3D shows the waveform of the output voltage setting signal Er, which is a voltage target value for constant voltage control. Hereinafter, it will be described with reference to FIG. 3.

As shown in Fig. 3A, as for the feed rate Fw, 0 or more becomes the forward transmission period, and less than 0 becomes the reverse transmission period. Forward feeding means feeding in the direction of bringing the welding wire closer to the base material, and reverse feeding means feeding in the direction separated from the base material. The feed speed Fw is changed to a sinusoidal shape and has a waveform shifted toward the forward feed side. For this reason, the average value of the feeding speed Fw becomes a positive value, and the welding wire is conveyed in average.

As shown in Fig. 3A, the feeding speed Fw is 0 at the time t1, the period between the times t1 and t2 becomes the forward acceleration period, and becomes the maximum value of the forward transmission at time t2, and the time The period of t2 to t3 becomes the forward deceleration period, the period of time t3 becomes 0, the period of the time t3 to t4 becomes the backward acceleration period, the period of time t4 becomes the maximum value of the reverse transmission, and the period of time t4 to t5 is reverse transmission It becomes a deceleration period. Then, the period of time t5 to t6 becomes a forward acceleration period again, and the period of time t6 to t7 becomes a forward deceleration period again.

In the consumable electrode arc welding, a welding power source with constant voltage control is used. This constant voltage control is performed by feedback control so that the output voltage of the welding power source becomes equal to the predetermined output voltage setting signal Er. As shown in Fig. 3D, since the output voltage setting signal Er is a constant value during welding, a constant output voltage is output by constant voltage control.

The short circuit between the welding wire and the base material often occurs before and after the forward maximum value at time t2. Fig. 3 shows a case where a short circuit occurs at time t21 during the forward speed deceleration period after the maximum value of the forward feed. When a short circuit occurs at time t21, as shown in Fig. 3(C), the welding voltage Vw rapidly decreases to a short circuit voltage value of several V, and as shown in Fig. 3(B), welding The current Iw gradually increases.

As shown in Fig. 3A, since the feeding speed Fw becomes a backfeed period from time t3, the welding wire is fed back. The short circuit is canceled by this reverse transmission, and the arc regenerates at time t31. The regeneration of the arc often occurs before and after the maximum value of the reverse transmission at time t4. Fig. 3 shows a case in which the arc regenerates at time t31 during the backfeed acceleration period before the maximum value of the backfeed. Therefore, the period of time t21 to t31 becomes the short-circuit period.

When the arc regenerates at time t31, as shown in Fig. 3C, the welding voltage Vw increases rapidly to an arc voltage value of several tens of V. As shown in Fig. 3B, the welding current Iw starts to change from the state of the maximum value during the short circuit period.

During the period of time t31 to t5, as shown in Fig. 3A, since the feeding speed Fw is in a reverse feeding state, the welding wire is pulled up and the arc length gradually increases. When the arc length increases, the welding voltage Vw increases, and since the constant voltage is controlled, the welding current Iw decreases. Therefore, during the arc period back-transmission period (Tar) of time t31 to t5, the welding voltage Vw gradually increases as shown in Fig. 3(C), and as shown in Fig. 3(B), welding The current Iw gradually decreases.

Then, the following short circuit occurs at time t61 during the forward deceleration period of times t6 to t7. However, in the short circuit occurring at time t61, the time (phase) from the maximum value of forward transmission is lower than the short circuit occurring at time t21. The period of time t31 to t61 becomes the arc period. During the period of time t5 to t61, as shown in Fig. 3A, since the feeding speed Fw is in the forward feeding state, the welding wire is forward fed and the arc length gradually shortens. When the arc length is shortened, the welding voltage Vw becomes small, and the welding current Iw increases because the constant voltage is controlled. Therefore, during the arc period forwarding period Tas of the times t5 to t61, as shown in Fig. 3C, the welding voltage Vw gradually decreases, and as shown in Fig. 3B, The welding current Iw gradually increases.

As described above, in the welding method of repeating the forward and reverse transmission of the welding wire, the period of repetition of short circuit and arc, which was not possible in the conventional technology of constant speed supply, can be set to a desired value, so that the amount of spatter generated is reduced and the appearance of the bead is reduced. It is possible to improve the welding quality such as improvement.

However, as described above, the welding current Iw gradually increases as the arc length decreases during the forward transmission period Tas of the arc period from time t5 to t61, so the lifting force acting on the volume of the tip of the welding wire This gradually gets bigger. As a result, the timing of occurrence of a short circuit fluctuates. When the fluctuation of the timing of occurrence of a short circuit increases, the period of the short circuit and the arc and the period of the forward transmission and the reverse transmission become out of synchronization, and the period of the short circuit and the arc fluctuates. Patent Document 1 discloses a method for returning this synchronous state to the original synchronous state.

In the invention of Patent Document 1, in the case where a short circuit does not occur until the feed rate reaches a predetermined feed rate during the deceleration of the feed rate during the forward feeding of the welding wire, the periodic change is stopped and the feed rate is changed to the first feed rate. If a short circuit occurs during forwarding at the first feed rate, the speed is decelerated from the first feed rate, and a periodic change is resumed to perform welding. This attempts to return the out of sync state to the sync state.

Japanese Patent No. 4807474

In the invention of Patent Document 1, when a short circuit does not occur at an appropriate timing, the feeding speed is switched to a constant speed of forward feeding, and when a short circuit occurs, the feeding speed is returned to the original periodic change. However, in this control, there is a problem that the short-circuit and arc periods are treated after they are out of sync with the periods of forward and reverse feed rates, and the welding state tends to become unstable.

Accordingly, an object of the present invention is to provide an arc welding control method capable of performing a stable welding by suppressing the period of short circuit and arc and the period of forward and reverse transmission of the feed rate from being out of sync.

In order to solve the above-described problem, the arc welding control method of the present invention is a constant voltage control so that the output of the welding power source becomes equal to the voltage target value by periodically repeating the forward and reverse transmission periods of the feed rate of the electrode to the base material. And, in the arc welding control method of repeatedly welding the short-circuit period and the arc period,

During the forward transmission period during the arc period, the voltage target value is decreased with time.

The arc welding control method of the present invention is characterized in that the decrease in the voltage target value is performed from the start of the forward transmission period during the arc period.

The arc welding control method of the present invention is characterized in that the decrease in the voltage target value is performed from a time point when a predetermined period has elapsed from the start of the forward transmission period during the arc period.

The arc welding control method of the present invention is characterized in that the reduction in the voltage target value is performed from a point in time when the feed rate in the forward transmission period in the arc period reaches a predetermined reference value.

The arc welding control method of the present invention is characterized in that the rate of change of the decrease in the voltage target value is changed according to a specific value of the feed rate.

According to the present invention, even if the arc length gradually decreases during the forward transmission period during the arc period and the welding voltage gradually decreases, the welding current decreases, so that the volume can be prevented from being raised. As a result, fluctuations in timing at which a short circuit occurs can be suppressed. For this reason, in the present invention, it is possible to perform stable welding by suppressing the period of the short circuit and the arc and the period of the forward and reverse transmission of the feed rate from being out of sync.

1 is a block diagram of a welding power supply for implementing the 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 supply of Fig. 1 for explaining the arc welding control method according to Embodiment 1 of the present invention.
Fig. 3 is a waveform diagram in a welding method in which forward and reverse feed rates are periodically repeated in the prior art.

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

[Embodiment 1]

1 is a block diagram of a welding power supply for implementing the arc welding control method according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG. 1.

The power supply main circuit PM receives a commercial power supply (not shown) such as 3-phase 200V as an input, and performs output control by inverter control or the like in accordance with an error amplification signal Ea, which will be described later, to adjust the output voltage E. Print. This power supply main circuit (PM), although not shown, is a primary rectifier that rectifies a commercial power supply, a smoothing capacitor that smoothes the rectified direct current, an inverter circuit that converts smoothed direct current into high-frequency alternating current, and welds high-frequency alternating current. A high-frequency transformer that steps down to a voltage value suitable for the voltage, a secondary rectifier that rectifies the stepped high-frequency alternating current into direct current, a modulation circuit that performs pulse width modulation control with the above error amplification signal (Ea) as input, and a pulse width modulation control signal. It is provided with an inverter driving circuit for driving a switching element of the inverter circuit as an input.

The reactor WL smoothes the output voltage E. The inductance value of this reactor WL is, for example, 200 µH.

The supply motor WM receives the supply control signal Fc to be described later, and periodically repeats forward and reverse transmission to supply the welding wire 1 at the supply speed Fw. A motor with fast transient response is used for this feed motor WM. In order to speed up the rate of change of the feeding speed Fw of the welding wire 1 and the reversal of the feeding direction, the feeding motor WM is sometimes installed near the tip of the welding torch 4. In addition, two feed motors WM may be used to provide a push-pull feed system.

The welding wire 1 is fed into the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 between the welding wire 1 and the base material 2 ) Occurs. A welding voltage Vw is applied between the power supply chip (not shown) in the welding torch 4 and the base material 2, so that the welding current Iw is energized.

The voltage detection circuit VD detects the above welding voltage Vw and outputs a voltage detection signal vd. The short-circuit determination circuit SD receives the voltage detection signal v as an input, and when this value is less than a predetermined short-circuit determination value, it determines that it is a short-circuit period and becomes a high level, and the voltage detection signal v is a predetermined short circuit. When it is more than the discrimination value, it is discriminated as an arc period, and a short discrimination signal Sd which becomes a low level is output. This short-circuit discrimination value is set to about 15V.

The feed rate setting circuit FR outputs a feed rate setting signal Fr of a predetermined pattern in which forward and reverse feeds are periodically repeated, as described in detail with reference to Fig. 2A. When the feed rate setting signal Fr is 0 or more, it becomes the forward transmission period, and when it is less than 0, it becomes the reverse transmission period.

The supply control circuit FC receives the supply speed setting signal Fr as an input and transmits the supply control signal Fc for supplying the welding wire 1 at a supply speed Fw corresponding to this set value. It is output to the supply motor (WM) of.

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.

The output voltage control setting circuit (ECR) receives the output voltage setting signal (Er), the short-circuit determination signal (Sd), and the feed rate setting signal (Fr) as inputs, so that the short-circuit determination signal Sd is At the low level (arc period), during the first period from the point when the feed speed setting signal Fr becomes 0 or more (forward transmission period) until the short discrimination signal Sd becomes the high level (short period), The output voltage control setting signal Ecr, which decreases with the passage of time, is output based on the value of the output voltage setting signal Er as a starting point. During periods other than the first period of the arc period, the output voltage control setting circuit ECR outputs the value of the output voltage setting signal Er as it is as the output voltage control setting signal Ecr. In this embodiment, this output voltage control setting signal Ecr becomes a voltage target value for constant voltage control.

The error amplification circuit EA receives the output voltage control setting signal Ecr and the output voltage detection signal Ed as inputs, and the output voltage control setting signal Ecr (+) and the output voltage detection signal ( Ed) (-) error is amplified, and the error amplified signal Ea is output. By this circuit, the welding power source is controlled at a constant voltage.

FIG. 2 is a timing chart of signals in the welding power supply of FIG. 1 for explaining the arc welding control method according to Embodiment 1 of the present invention. Fig. 2(A) shows the time change of the feeding speed (Fw), Fig. 2(B) shows the time change of the welding current Iw, and Fig. 2(C) shows the time of the welding voltage (Vw) The change is shown, and FIG. 2D shows the time change of the output voltage control setting signal Ecr, which is a voltage target value for constant voltage control. Fig. 2 corresponds to Fig. 3 described above, and the operation is different during the arc period forwarding period Tas at times t5 to t61. Hereinafter, it will be described with reference to FIG. 2.

As shown in Fig. 2A, as for the feed rate Fw, 0 or more is the forward feed period, and less than 0 is the back feed period. The feed rate Fw is changed to a sinusoidal wave shape, and is a waveform shifted toward the forward feed side. For this reason, the average value of the feeding speed Fw becomes a positive value, and the welding wire is conveyed on average. The change pattern of the feeding speed Fw may be a triangular wave shape or a trapezoidal wave shape.

As shown in Fig. 2A, the feed rate Fw is 0 at the time t1, the period between the times t1 and t2 becomes the forward acceleration period, and becomes the maximum value of the forward feed at time t2, and the time The period of t2 to t3 becomes the forward deceleration period, the period of time t3 becomes 0, the period of the time t3 to t4 becomes the backward acceleration period, the period of time t4 becomes the maximum value of the reverse transmission, and the period of time t4 to t5 is reverse transmission It becomes a deceleration period. Then, the period of time t5 to t6 becomes a forward acceleration period again, and the period of time t6 to t7 becomes a forward deceleration period again. The repetition period of this forward transmission and reverse transmission is set to a predetermined value. For example, the forward acceleration period at times t1 to t2 is 2.7 ms, the forward deceleration period at times t2 to t3 is 2.7 ms, the reverse acceleration period at times t3 to t4 is 2.3 ms, and the reverse speed deceleration at times t4 to t5 The period is 2.3 ms. In addition, the maximum value of forward transmission is 50 m/min, and the maximum value of reverse transmission is -50 m/min. In this case, the repetition period of forward and reverse feed is 10 ms, and the average value of the feed speed Fw is about 4 m/min (average welding current is about 150 A).

The short circuit between the welding wire and the base material often occurs before and after the forward maximum value at time t2. In Fig. 2, a case where a short circuit occurs at time t21 during the forward speed deceleration period after the maximum value of the forward feed is shown. When a short circuit occurs at time t21, as shown in Fig. 2(C), the welding voltage Vw rapidly decreases to a short circuit voltage value of several V, and as shown in Fig. 2(B), welding The current Iw gradually increases.

As shown in Fig. 2A, since the feeding speed Fw becomes a backfeed period from time t3, the welding wire is fed back. The short circuit is canceled by this reverse transmission, and the arc regenerates at time t31. The regeneration of the arc often occurs before and after the maximum value of the reverse transmission at time t4. In Fig. 2, the case where an arc occurs at time t31 during the backfeed acceleration period before the maximum value of the backfeed is shown. Therefore, the period of time t21 to t31 becomes the short-circuit period. During this short-circuit period, as shown in Fig. 2D, the output voltage control setting signal Ecr has a predetermined constant value. This point is the same as in the prior art.

When the arc regenerates at time t31, as shown in Fig. 2C, the welding voltage Vw rapidly increases to a value of several tens of V. As shown in Fig. 2B, the welding current Iw starts to change from the state of the maximum value during the short circuit period.

During the period of time t31 to t5, as shown in Fig. 2A, since the feeding speed Fw is in a reverse feeding state, the welding wire is pulled up and the arc length gradually increases. When the arc length increases, the welding voltage Vw increases, and since the constant voltage is controlled, the welding current Iw decreases. Therefore, during the arc period back-transmission period (Tar) of the time t31 to t5, as shown in Fig.2(C), the welding voltage (Vw) gradually increases, and as shown in Fig.2(B), welding The current Iw gradually decreases. During this arc period and reverse transmission period Tar, the output voltage control setting signal Ecr remains at a constant value, as shown in Fig. 2D. The operation in this period is the same as in the prior art.

Then, the following short circuit occurs at time t61 during the forward deceleration period of times t6 to t7. However, unlike FIG. 3, the time (phase) from the maximum value of the forward transmission substantially coincides with the short circuit occurring at the time t61 and the short circuit occurring at the time t21. The period of time t31 to t61 becomes the arc period. During the period of time t5 to t61, as shown in Fig. 2A, since the feeding speed Fw is in the forward feeding state, the welding wire is forwarded and the arc length gradually shortens. During this arc period forwarding period Tas, as shown in Fig. 2D, the output voltage control setting signal Ecr gradually decreases with the passage of time. When the arc length is shortened, as shown in Fig. 2C, the welding voltage Vw decreases. Here, as shown in Fig. 2D, since the output voltage control setting signal Ecr decreases, the reduction rate of the welding voltage Vw becomes larger than that in the conventional technique of Fig. 3. As a result, as shown in Fig. 2B, the welding current Iw gradually decreases, unlike the prior art. Therefore, during the arc period forwarding period Tas of the times t5 to t61, as shown in Fig. 2C, the welding voltage Vw gradually decreases with a large decrease rate, and as shown in Fig. 2B. As such, the welding current Iw also gradually decreases.

As shown in Fig. 2D, the output voltage control setting signal Ecr becomes a constant value during periods other than the arc period forward transmission period Tas, and accompanies the passage of time during the arc period forward transmission period Tas. To decrease. This reduction method is performed as follows.

1) As shown in Fig. 2D, the output voltage control setting signal Ecr starts to decrease from the start of the arc period forwarding period Tas at time t5, and continues until the short-circuit period at time t61. do. The output voltage control setting circuit ECR in this case is as shown in FIG. 1.

2) The output voltage control setting signal Ecr may start to decrease from the start of the arc period forwarding period Tas at time t5 to the time when a predetermined period has elapsed, and continue until the short circuit period at time t61. In this case, the output voltage control setting circuit ECR receives the output voltage setting signal Er, the short-circuit determination signal Sd, and the feed rate setting signal Fr as inputs, and the short-circuit determination signal Sd is at a low level ( Arc period), the second from the point when a predetermined period has elapsed after the feed rate setting signal Fr becomes 0 or more (forward transmission period) until the short-circuit determination signal Sd reaches the high level (short period). During the period, the output voltage control setting signal Ecr which decreases with the passage of time is output based on the value of the output voltage setting signal Er as a starting point. During a period other than the second period of the arc period, the output voltage control setting circuit ECR outputs the value of the output voltage setting signal Er as it is as the output voltage control setting signal Ecr.

3) The output voltage control setting signal Ecr may start to decrease from the point in time when the feed rate Fw during the arc period forward feed period Tas reaches a predetermined reference value, and continue until the short-circuit period at time t61. In this case, the output voltage control setting circuit ECR receives the output voltage setting signal Er, the short-circuit determination signal Sd, and the feed rate setting signal Fr as inputs, and the short-circuit determination signal Sd is at a low level ( Arc period), output during the third period from the point when the feed rate setting signal Fr reaches the reference value of a predetermined positive value until the short-circuit discrimination signal Sd reaches the high level (short-circuit period). The output voltage control setting signal Ecr which decreases with the passage of time is output based on the value of the voltage setting signal Er as a starting point. During periods other than the third period of the arc period, the output voltage control setting circuit ECR outputs the value of the output voltage setting signal Er as it is as the output voltage control setting signal Ecr.

4) In 1) to 3) above, the rate of change of the decrease in the output voltage control setting signal Ecr may be changed in accordance with a specific value of the feeding speed Fw. The specific value of the feed rate Fw is the average value of the feed rate Fw, the maximum value of the forward feed, or the rate of change of the feed rate Fw during the forward feed period Tas during the arc period.

5) In the above 1) to 4), when the output voltage control setting signal Ecr during decrease reaches a predetermined lower limit value, the decrease may be stopped.

6) In the above 1) to 5), the decrease in the output voltage control setting signal Ecr may be linear or curved.

According to the first embodiment described above, the voltage target value (output voltage control setting signal Ecr) is decreased with the passage of time during the forwarding period (arc period forwarding period Tas) during the arc period. Thereby, in the first embodiment, even if the arc length gradually decreases during the forward transmission period during the arc period and the welding voltage gradually decreases, the welding current decreases, so that the volume can be prevented from being raised. As a result, fluctuations in timing at which a short circuit occurs can be suppressed. For this reason, in the present embodiment, it is possible to perform stable welding by suppressing the period of the short circuit and the arc and the period of the forward and reverse transmission of the feed rate from being out of sync.

According to the present invention, an arc welding control in which the forward and reverse periods of the feed rate are periodically repeated, the constant voltage is controlled so that the output of the welding power source becomes equal to the value of the target voltage value, and the short-circuit period and the arc period are repeatedly welded. Can provide a way.

As mentioned above, although the present invention has been described with reference to specific embodiments, the present invention is not limited to this embodiment, and various modifications can be made without departing from the technical idea of the disclosed invention.

This application is based on the Japanese patent application (Japanese patent application 2013-266768) of the application on December 25, 2013, The content is taken in here.

1: welding wire
2: base material
3: arc
4: welding torch
5: feed roll
EA: Error amplifier circuit
Ea: error amplification signal
ECR: Output voltage control setting circuit
Ecr: Output voltage control setting signal
ED: output voltage detection circuit
Ed: output voltage detection signal
ER: Output voltage setting circuit
Er: Output voltage setting signal
FC: Supply control circuit
Fc: dispatch control signal
FR: Feed rate setting circuit
Fr: Feed rate setting signal
Fw: feed rate
Iw: welding current
PM: Power main circuit
SD: short circuit detection circuit
Sd: Short circuit discrimination signal
Tar: Arc period and reverse transmission period
Tas: arc period forwarding period
VD: voltage detection circuit
vd: voltage detection signal
Vw: welding voltage
WL: Reactor
WM: feed motor

Claims (5)

In the arc welding control method of repeatedly welding the short-circuit period and the arc period by periodically repeating the forward transmission period and the reverse transmission period of the feed rate of the electrode to the base material, and controlling the constant voltage so that the output of the welding power source becomes equal to the voltage target value. In,
The arc welding control method, characterized in that during the forward transmission period during the arc period, the voltage target value is decreased with time. The arc welding control method according to claim 1, wherein the decrease in the voltage target value is performed from the start of the forward transmission period during the arc period. The arc welding control method according to claim 1, wherein the decrease in the voltage target value is performed from a time point when a predetermined period has elapsed from the start of the forward transmission period during the arc period. The arc welding control method according to claim 1, wherein the decrease in the voltage target value is performed from a point in time when the feed rate in the forward transmission period in the arc period reaches a predetermined reference value. The arc welding control method according to any one of claims 1 to 4, wherein the rate of change of the decrease in the voltage target value is changed according to a specific value of the feed rate.

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