JP7431661B2 - arc welding equipment - Google Patents

Description

The present invention relates to an arc welding device that performs welding by alternately switching the feeding of welding wire between forward feeding and reverse feeding, and repeating a short circuit period and an arc period.

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 the base metal. In consumable electrode arc welding, the welding wire and the base metal are often in a welded state in which short circuit periods and arc periods alternate.

In order to further improve welding quality, forward and reverse feed arc welding has been proposed in which welding is performed by alternately switching the feed of the welding wire between forward feed and reverse feed (see, for example, Patent Document 1). This forward and reverse feed arc welding can stabilize the cycle of short-circuit and arc repetitions compared to conventional technology with a constant feed speed, resulting in reduced spatter generation and improved bead appearance. It is possible to improve welding quality.

Unexamined Japanese Patent Publication No. 2018-1270

In forward and reverse feed arc welding, welding quality is improved by transferring droplets in synchronization with the short circuit/arc cycle. However, when an aluminum welding wire is used in forward and reverse feed arc welding, if the welding current value during the arc period becomes large and exceeds the critical current value, droplets will migrate during the arc period. In this case, the transfer of the droplets is no longer performed in synchronization with the cycle of short circuits and arcs. As a result, there is a problem that welding quality deteriorates. In particular, when the welding wire is made of soft aluminum, the critical current value is small, so droplets migrate randomly during the arc period, which significantly deteriorates the welding quality.

Therefore, an object of the present invention is to provide an arc welding apparatus that can obtain good welding quality even when using a soft aluminum welding wire in forward and reverse feed arc welding.

In order to solve the above-mentioned problem, the invention of claim 1:
Using a soft aluminum welding wire, the welding wire feed is alternately switched between forward feed and reverse feed, and the short circuit period and arc period are repeated.
During the arc period, a first arc period in which the first arc current Ia1 is applied, a second arc period in which the second arc current Ia2 is applied, and a third arc period in which the third arc current Ia3 is applied are changed over time. In an arc welding device in which the welding current is applied so that Ia1>Ia2>Ia3,
The first arc current Ia1 is set to a critical current value or more, and the first arc period is set to a time longer than the time during which the droplet migrates during this period,
the second arc current Ia2 is set below the critical current value;
This is an arc welding device characterized by the following.

The invention of claim 2 is:
The average value of the welding current is 200A or more,
The arc welding apparatus according to claim 1, characterized in that:

The invention of claim 3 is:
the first arc period is constant current controlled;
The arc welding apparatus according to claim 1 or 2, characterized in that:

The invention of claim 4 is:
The second arc period is constant voltage controlled.
The arc welding apparatus according to any one of claims 1 to 3, characterized in that:

According to the present invention, good welding quality can be obtained even when a soft aluminum welding wire is used in forward and reverse feed arc welding.

1 is a block diagram of an arc welding apparatus according to Embodiment 1 of the present invention. 2 is a timing chart of each signal in the arc welding apparatus of FIG. 1. FIG.

Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 is a block diagram of an arc welding apparatus according to Embodiment 1 of the present invention. Each block will be explained below with reference to the same figure.

The power supply main circuit PM receives a commercial power supply (not shown) such as a three-phase 200V power supply as an input, performs output control by inverter control, etc. according to an error amplification signal Ea, which will be described later, and outputs an output voltage E. Although not shown, this power supply main circuit PM is driven by a primary rectifier that rectifies commercial power, a smoothing capacitor that smoothes the rectified DC, and the above-mentioned error amplification signal Ea that converts the smoothed DC into high-frequency AC. It is equipped with an inverter circuit, 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 DC.

Reactor WL smoothes the above output voltage E. The inductance value of this reactor WL is, for example, 100 μH.

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

The welding wire 1 is fed through the welding torch 4 by rotation of the feed roll 5 coupled to the above-mentioned feed motor WM, and an arc 3 is generated between the welding wire 1 and the base metal 2. A welding voltage Vw is applied between a power supply tip (not shown) in the welding torch 4 and the base metal 2, and a welding current Iw is applied. Shielding gas (not shown) is ejected from the tip of the welding torch 4. As the welding wire 1, a 1000-series pure aluminum wire or a 4000-series soft aluminum wire specified in the JIS standard is used. In this specification, the term soft aluminum wire also includes pure aluminum wire. 100% by volume argon gas is used as the shielding gas.

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

The voltage error amplification circuit EV receives the above output voltage setting signal Er and the above output voltage detection signal Ed as input, and amplifies the error between the output voltage setting signal Er (+) and the output voltage detection signal Ed (-). , outputs a voltage error amplified signal Ev.

The current detection circuit ID detects the above-mentioned welding current Iw and outputs a current detection signal Id. Voltage detection circuit VD detects the above-mentioned welding voltage Vw and outputs voltage detection signal Vd. The short-circuit discrimination circuit SD inputs the above-mentioned voltage detection signal Vd, and when this value is less than a predetermined short-circuit discrimination value (approximately 10V), it determines that there is a short-circuit period and becomes High level; It determines that it is in the arcing period and outputs a short circuit determination signal Sd that goes to Low level.

The normal feed acceleration period setting circuit TSUR outputs a predetermined normal feed acceleration period setting signal Tsur.

The normal feed deceleration period setting circuit TSDR outputs a predetermined normal feed deceleration period setting signal Tsdr.

The 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.

The normal feed peak value setting circuit WSR outputs a predetermined normal feed peak value setting signal Wsr.

The reverse transmission peak value setting circuit WRR outputs a predetermined reverse transmission peak value setting signal Wrr.

The feeding speed setting circuit FR has 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, and the above-mentioned The forward feed peak value setting signal Wsr, the above-mentioned reverse feed peak value setting signal Wrr, and the above-mentioned short circuit determination signal Sd are input, and a feed speed pattern generated by the following processing is output as a feed speed setting signal Fr. When this feeding speed setting signal Fr is 0 or more, it is a forward feeding period, and when it is less than 0, it is a reverse feeding period.
1) During the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur, a feed speed setting signal Fr is output that accelerates from 0 to a positive forward feed peak value Wsp determined by the forward feed peak value setting signal Wsr. .
2) Subsequently, during the normal feed peak period Tsp, the feed speed setting signal Fr is output to maintain the above normal feed peak value Wsp.
3) When the short circuit determination signal Sd changes from Low level (arc period) to High level (short circuit period), it shifts to the normal feed deceleration period Tsd determined by the normal feed deceleration period setting signal Tsdr, and from the above normal feed peak value Wsp. Outputs a feed speed setting signal Fr that decelerates to 0.
4) Subsequently, during the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur, the feed rate setting signal Fr is accelerated from 0 to a negative value reverse feed peak value Wrp determined by the reverse feed peak value setting signal Wrr. Output.
5) Subsequently, during the reverse feed peak period Trp, the feed speed setting signal Fr is output to maintain the above-mentioned reverse feed peak value Wrp.
6) When the short-circuit determination signal Sd changes from High level (short-circuit period) to Low level (arc period), it shifts to the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr, and from the above reverse feed peak value Wrp. Outputs a feed speed setting signal Fr that decelerates to 0.
7) By repeating steps 1) to 6) above, a feeding speed setting signal Fr having a feeding pattern that changes in the form of a positive and negative trapezoidal wave is generated.

The feed control circuit FC inputs the above feed speed setting signal Fr and generates 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. Output to the above feed motor WM.

The current reducing resistor R is inserted between the reactor WL and the welding torch 4 described above. The value of this current reducing resistor R is set to a value (approximately 0.5 to 3 Ω) that is 50 times or more larger than the short circuit load (approximately 0.01 to 0.03 Ω). When this current reducing resistor R is inserted into the current carrying path, the energy stored in the reactor WL and the reactor of the external cable is rapidly discharged.

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

The constriction detection circuit ND inputs the short circuit determination signal Sd, the voltage detection signal Vd, and the current detection signal Id, and detects the voltage detection signal Vd when the short circuit determination signal Sd is at a high level (short circuit period). Constriction detection determines that the constriction formation state has reached the standard state when the voltage rise value reaches the reference value and becomes High level, and becomes Low level when the short circuit determination signal Sd changes to Low level (arc period) Outputs signal Nd. Furthermore, the constriction detection signal Nd may be changed to High level at the time when the differential value of the voltage detection signal Vd during the short-circuit period reaches the corresponding reference value. Furthermore, the resistance value of the droplet is 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 this resistance value reaches the corresponding reference value, the constriction detection signal Nd is calculated. It may be changed to High level.

The low level current setting circuit ILR outputs a predetermined low level current setting signal Ilr. The current comparison circuit CM inputs this low-level current setting signal Ilr and the above-mentioned current detection signal Id, 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 inputs the above current comparison signal Cm and the above constriction detection signal Nd, changes to Low level when the constriction detection signal Nd changes to High level, and then changes to Low level when current comparison signal Cm 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 a constriction is detected, the drive signal Dr becomes Low level, the transistor TR is turned off, and the current reducing resistor R is inserted into the current carrying path, so the welding current Iw that conducts the short-circuited load suddenly decreases. . Then, when the rapidly decreased value of welding current Iw decreases to the value of low-level current setting signal Ilr, drive signal Dr becomes High level and transistor TR is turned on, so current reducing resistor R is short-circuited and normal Return to state.

The first arc period setting circuit TA1R outputs a predetermined first arc period setting signal Ta1r. The first arc period setting signal Ta1r is set to a time longer than the time during which the droplets migrate during this period.

The first arc period circuit STA1 inputs the short circuit determination signal Sd and the first arc period setting signal Ta1r, and the short circuit determination signal Sd changes to Low level (arc period) and a predetermined delay period Tc elapses. From the point in time, the first arc period signal Sta1 is outputted to be at High level during the first arc period Ta1 predetermined by the first arc period setting signal Ta1r.

The first arc current setting circuit IA1R outputs a predetermined first arc current setting signal Ia1r. The first arc current setting signal Ia1r is set to a critical current value or higher.

The third arc period circuit STA3 inputs the above-mentioned short circuit determination signal Sd and becomes High level when a predetermined current drop time Td has elapsed from the time when the short circuit determination signal Sd changed to Low level (arc period). Then, when the short circuit determination signal Sd becomes High level (short circuit period), the third arc period signal Sta3 that becomes Low level is output.

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

The current control setting circuit ICR has the above short circuit determination signal Sd, the above low level current setting signal Ilr, the above constriction detection signal Nd, the above first arc period signal Sta1, the above third arc period signal Sta3, and the above With the first arc current setting signal Ia1r and the third arc current setting signal Ia3r as input, the following processing is performed and a current control setting signal Icr is output.
1) During the delay period from the time when the short circuit determination signal Sd changes to Low level (arc period) until the first arc period signal Sta1 changes to High level, the current control setting becomes the value of the low level current setting signal Ilr. A signal Icr is output.
2) After that, when the first arc period signal Sta1 is at High level (first arc period), the current control setting signal Icr which becomes the first arc current setting signal Ia1r is output.
3) During the period from the time when the first arc period signal Sta1 changes to Low level until the third arc period signal Sta3 changes to Low level (second arc period and third arc period), the third arc current setting is A current control setting signal Icr, which becomes a signal Ia3r, is output.
4) When the short-circuit determination signal Sd changes to High level (short-circuit period), the current becomes the predetermined initial setting value during the predetermined initial period, and thereafter the current changes to the predetermined short-circuit peak setting value with the predetermined short-circuit slope. It outputs a current control setting signal Icr that increases to a value of 1 and maintains that value.
5) After that, when the constriction detection signal Nd changes to High level, a current control setting signal Icr having the value of the low-level current setting signal Ilr is outputted.

The current error amplification circuit EI receives the above current control setting signal Icr and the above current detection signal Id, amplifies the error between the current control setting signal Icr (+) and the current detection signal Id (-), and outputs a current. Outputs an error amplified signal Ei.

The power supply characteristic switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev, the first arc period signal Sta1, and the third arc period signal Sta3 as input, and performs the following processing, Outputs an error amplified signal Ea.
1) During the second arc period Ta2 until the first arc period signal Sta1 changes to Low level and the third arc period signal Sta3 changes to High level, the voltage error amplification signal Ev is output as the error amplification signal Ea. .
2) During other periods, the current error amplification signal Ei is output as the error amplification signal Ea.
With this circuit, the characteristics of the welding power source are constant current characteristics during the short circuit period, delay period, first arc period Ta1, and third arc period Ta3, and constant voltage characteristics during the second arc period Ta2.

FIG. 2 is a timing chart of each signal in the arc welding power source of FIG. 1. The same figure (A) shows the time change of the feeding speed Fw, the same figure (B) shows the time change of the welding current Iw, the same figure (C) shows the time change of the welding voltage Vw, the same figure (D ) shows the time change of the short-circuit discrimination signal Sd, the same figure (E) shows the time change of the first arc period signal Sta1, and the same figure (F) shows the time change of the third arc period signal Sta3. The operation of each signal will be explained below with reference to the same figure.

The feed rate Fw shown in FIG. 1A is controlled by the value of the feed rate setting signal Fr output from the feed rate setting circuit FR of FIG. The feeding speed Fw is a normal feed acceleration period Tsu determined by the normal feed acceleration period setting signal Tsur in FIG. 1, a normal feed peak period Tsp that continues until a short circuit occurs, and a normal feed speed determined by the normal feed deceleration period setting signal Tsdr in FIG. A feed deceleration period Tsd, a reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur in FIG. 1, a reverse feed peak period Trp that continues until an arc occurs, and a 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 feed peak value Wsp is determined by the forward feed peak value setting signal Wsr in FIG. 1, and the reverse feed peak value Wrp is determined by the reverse feed peak value setting signal Wrr in FIG. As a result, the feed rate setting signal Fr has a feed pattern that changes in the shape of a substantially trapezoidal wave of positive and negative values.

[Operation during the 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 suddenly decreases to a short circuit voltage value of several volts, as shown in (D) of the same figure, as shown in (C) of the same figure. 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 feeding speed Fw is decelerated from the above normal feed peak value Wsp to 0, as shown in FIG. . For example, the normal feed deceleration period Tsd is set to 1 ms.

As shown in FIG. 3A, the feed rate Fw enters a predetermined reverse feed acceleration period Tru from time t2 to t3, and accelerates from 0 to the above-mentioned reverse feed peak value Wrp. During this period, the short circuit period continues. For example, the reverse transmission acceleration period Tru is set to 1 ms.

When the reverse feed acceleration period Tru ends at time t3, the feed rate Fw enters the reverse feed peak period Trp and reaches the above-mentioned reverse feed 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 becomes a short circuit period. Although the reverse transmission peak period Trp is not a predetermined value, it is approximately 3 ms. Further, for example, the reverse transport peak value Wrp is set to -20 to -50 m/min.

As shown in FIG. 3B, the welding current Iw during the short-circuit period from time t1 to t4 has a predetermined initial current value during a predetermined initial period. Thereafter, the welding current Iw increases at a predetermined short-circuit slope, and when it reaches a predetermined short-circuit peak value, it maintains that value.

As shown in FIG. 3C, the welding voltage Vw increases from around the point where the welding current Iw reaches its peak value at the time of short circuit. This is because a constriction is gradually formed in the droplet at the tip of the welding wire 1 due to the reverse feeding of the welding wire 1 and the action of the pinch force due to the welding current Iw.

After that, when the voltage increase 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 going high, the drive signal Dr in FIG. 1 goes low, so the transistor TR in FIG. 1 turns off and the current reducing resistor R in FIG. inserted. At the same time, the current control setting signal Icr in FIG. 1 is reduced to the value of the low level current setting signal Ilr. For this reason, as shown in the same figure (B), the welding current Iw rapidly decreases from the peak value at the time of short circuit to the low level current value. Then, when the welding current Iw decreases to a low level current value, the drive signal Dr returns to High level, so the transistor TR is turned on and the current reducing resistor R is short-circuited. As shown in the same figure (B), since the current control setting signal Icr remains at the low level current setting signal Ilr, the welding current Iw remains at a low level until a predetermined delay period Tc elapses from the re-occurrence of the arc. Maintain current value. Therefore, the transistor TR is in an off state only during the period from when the constriction detection signal Nd changes to High level until the welding current Iw decreases to a low level current value. As shown in FIG. 3C, the welding voltage Vw decreases once and then rises rapidly because the welding current Iw becomes smaller. Each of the parameters described 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, delay period Tc = 0.5ms.

[Operation during the arc period from time t4 to t7]
At time t4, when the constriction progresses and an arc is generated due to the pinch force caused by the reverse feeding of the welding wire and the application of the welding current Iw, the welding voltage Vw increases to an arc voltage value of several tens of V, as shown in FIG. As a result, the short circuit determination signal Sd changes to Low level (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 as shown in FIG. . For example, the reverse feed deceleration period Trd is set to 1 ms.

When the reverse deceleration period Trd ends at time t5, a transition begins to a predetermined forward acceleration period Tsu from time t5 to t6. During this normal feed acceleration period Tsu, as shown in FIG. 2A, the feeding speed Fw accelerates from 0 to the above normal feed peak value Wsp. During this period, the arc period continues. For example, the normal feed acceleration period Tsu is set to 1 ms.

When the normal feed acceleration period Tsu ends at time t6, the feeding speed Fw enters the normal feed peak period Tsp and reaches the above-mentioned normal feed peak value Wsp, as shown in FIG. The arc period continues during this period as well. The forward transmission peak period Tsp continues until a short circuit occurs at time t7. Therefore, the period from time t4 to t7 becomes an 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 15 ms. Further, for example, the normal feed peak value Wsp is set to 30 to 60 m/min.

When an arc occurs at time t4, the welding voltage Vw rapidly increases to an arc voltage value of 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 delay period Tc from time t4. This is because if the current value is increased immediately after an arc occurs, the reverse feeding of the welding wire and the melting of the welding wire due to the welding current are added together, causing the arc length to increase rapidly and the welding condition to become unstable. This is because there are cases.

When the delay period Tc ends at time t51 during the forward acceleration period Tsu, the first arc period signal Sta1 changes to High level as shown in FIG. Transition to one arc period Ta1. During this first arcing period Ta1, constant current control is continued, and as shown in the same figure (B), a predetermined first arc current Ia1 determined by the first arc current setting signal Ia1r of FIG. 1 is energized. As shown in the same figure (C), the welding voltage Vw becomes a value that is influenced by the current value and the arc load, and becomes a large value.

At time t62, when a predetermined current drop time Td has elapsed from arc occurrence time t4, the third arc period signal Sta3 changes to High level, as shown in FIG. The period from time t61 to t62 becomes the second arc period Ta2. During this second arc period Ta2, constant voltage control is performed. As shown in the figure (B), the second arc current Ia2 changes depending on the arc load, but has a smaller value than the first arc current Ia1 and a larger value than the third arc current Ia3. That is, the output is controlled so that Ia1>Ia2>Ia3. As shown in FIG. 2C, the welding voltage Vw is controlled to a predetermined value by constant voltage control, and becomes an intermediate value between the voltage value in the first arc period Ta1 and the voltage value in the third arc period Ta3. The second arc period Ta2 is not a predetermined value, but is approximately 5 ms.

The period from time t62 when the third arc period signal Sta3 changes to High level to time t7 when a short circuit occurs is the third arc period Ta3. During this third arc period Ta3, constant current control is performed. As shown in the figure (B), a predetermined third arc current Ia3 determined by the third arc current setting signal Ia3r of FIG. 1 is applied. As shown in the same figure (C), the welding voltage Vw becomes a value determined by the current value and the arc load. For example, the third arc current Ia3 is set to 60A. The third arc period Ta3 is not a predetermined value, but is approximately 1 ms.

As described above, according to the present embodiment, during the arc period, there is a first arc period in which the first arc current Ia1 is applied, a second arc period in which the second arc current Ia2 is applied, and a third arc current The third arc period in which Ia3 is energized is switched over time to control so that Ia1>Ia2>Ia3. The first arc current Ia1 is set to be equal to or higher than a critical current value at which the droplet transfer state becomes the spray transfer state. The first arc period is set to be longer than the time during which the droplets migrate. The second arc current Ia2 is set by adjusting the output voltage setting signal Er of FIG. 1 to be less than the above critical current value. For example, the first arc current Ia1 is 300 A, and the first arc period is 10 ms. In the above, a case has been described in which constant current control is performed during the first period, but constant voltage control may be performed. Even in that case, the first arc current Ia1 is made to be equal to or higher than the critical current value.

The effects of this embodiment will be explained below. When performing forward and reverse feed arc welding using a soft aluminum welding wire, it is common to use 100% by volume argon gas as the shielding gas. For this reason, the critical current value at which the droplet transfer state becomes the spray transfer state is as small as about 200A. As a result, there is a long period during which the current exceeds the critical current value during the arc period. During the period when the current exceeds this critical current value, droplet transfer occurs randomly, resulting in a state that is not synchronized with the short circuit/arc cycle.

In contrast, according to the present embodiment, a soft aluminum welding wire is used, the feeding of the welding wire is alternately switched between forward feeding and reverse feeding, the short circuit period and the arcing period are repeated, and the arcing period is During the process, a first arc period in which the first arc current Ia1 is applied, a second arc period in which the second arc current Ia2 is applied, and a third arc period in which the third arc current Ia3 is applied are switched over time, In an arc welding device that applies a welding current so that Ia1>Ia2>Ia3, the first arc current Ia1 is set to be equal to or higher than the critical current value, and the first arc period is longer than the time during which the droplets migrate during this period. The second arc current Ia2 is set to be less than the critical current value. In the above, the first arc current Ia1 is set to be equal to or higher than the critical current value, and the first arc period is set to a time longer than the time during which the droplets migrate, so the droplets are A transition will take place. Since the second arc current Ia2 and the third arc current Ia3 are less than the critical current value, droplets are formed at the tip of the welding wire but do not migrate. When the short-circuit period begins, the droplet formed at the tip of the welding wire will be short-circuited. Therefore, the droplet transfer will be ensured during the first arc period and the short circuit period, and will be synchronized with the short circuit/arc period. As described above, in this embodiment, good welding quality can be obtained even when a soft aluminum welding wire is used in forward and reverse feed arc welding.

Furthermore, according to this embodiment, the average value of the welding current is 200A or more. In the prior art, when the average value of the welding current is 200 A or more, the period during which the current exceeds the critical current value becomes longer during the arc period, and therefore the randomness of droplet transfer increases. In contrast, in this embodiment, even if the average value of the welding current exceeds 200 A, droplet transfer can be synchronized with the short circuit/arc cycle, so good welding quality can be obtained. .

Furthermore, according to the present embodiment, constant current control is performed during the first arc period. As a result, in this embodiment, the current value and its period can be precisely controlled so that the droplets migrate during the first arc period. Furthermore, the heat input during the first arc period can be precisely controlled. As a result, welding quality can be made higher.

Furthermore, according to this embodiment, constant voltage control is performed during the second arc period. Thereby, in this embodiment, the average arc length can be controlled to an appropriate value. As a result, the welding state can be made more stable.

1 welding wire
2 Base material
3 arc
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 EV Voltage error amplification circuit Ev Voltage error amplification signal FC Feed control circuit Fc Feed control signal FR Feed rate setting circuit Fr Feed rate setting signal Fw Feed rate Ia1 1st arc current IA1R 1st arc Current setting circuit Ia1r First arc current setting signal Ia2 Second arc current Ia3 Third arc current IA3R Third arc current setting circuit Ia3r Third arc current setting signal 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 Waist detection circuit Nd Waist detection signal PM Main power supply circuit R Current reducing resistor SD Short circuit determination circuit Sd Short circuit determination signal STA1 1st arc period circuit Sta1 1st 1 arc period signal STA3 3rd arc period circuit Sta3 3rd arc period signal SW Power supply characteristic switching circuit Tc Delay period TA1R 1st arc period setting circuit Ta1r 1st arc period setting signal Td Current drop time TR Transistor Trd Reverse feed deceleration period TRDR Reverse feed deceleration period setting circuit Trdr Reverse feed deceleration period setting signal Trp Reverse feed peak period Tru Reverse feed acceleration period TRUR Reverse feed acceleration period setting circuit Trur Reverse feed acceleration period setting signal Tsd Forward feed deceleration period TSDR Forward feed deceleration period setting circuit Tsdr Forward feed deceleration period setting signal Tsp Forward feed peak period Tsu Forward feed acceleration period TSUR Forward feed acceleration period setting circuit Tsur Forward feed acceleration period setting signal VD Voltage detection circuit Vd Voltage detection signal Vw Welding voltage WL Reactor WM Feed motor Wrp Reverse feed Peak value WRR Reverse feed peak value setting circuit Wrr Reverse feed peak value setting signal Wsp Forward feed peak value WSR Forward feed peak value setting circuit Wsr Forward feed peak value setting signal

Claims (4)

Using a soft aluminum welding wire, the welding wire feed is alternately switched between forward feed and reverse feed, and the short circuit period and arc period are repeated.
During the arc period, a first arc period in which the first arc current Ia1 is applied, a second arc period in which the second arc current Ia2 is applied, and a third arc period in which the third arc current Ia3 is applied are changed over time. In an arc welding device in which the welding current is applied so that Ia1>Ia2>Ia3,
The first arc current Ia1 is set to a critical current value or more, and the first arc period is set to a time longer than the time during which the droplet migrates during this period,
the second arc current Ia2 is set below the critical current value;
An arc welding device characterized by: The average value of the welding current is 200A or more,
The arc welding apparatus according to claim 1, characterized in that: the first arc period is constant current controlled;
The arc welding device according to claim 1 or 2, characterized in that: The second arc period is constant voltage controlled.
The arc welding apparatus according to any one of claims 1 to 3, characterized in that:

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