JP2024021967A - Forward/backward feeding arc-welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform high-quality welding having no sputtering occurring in the entire current range in forward/backward feeding arc-welding in which a material of a welding wire is aluminum or its alloy.

SOLUTION: A forward/backward feeding arc-welding method repeats an arc period and a short-circuit period between a welding wire a material of which is aluminum or its alloy and a base material, feeds forward (Fw) the welding wire during the arc period of time t4-t7, and feeds backward (reverse Fw) the welding wire during the shortcircuit period of time t1-t4. When a welding current average value is lower than a reference current value, shortcircuit Iw lower than the welding current average value is supplied. When the welding current average value is equal to or higher than the reference current value, shortcircuit Iw equal to or higher than the welding current average value is supplied. Then, when droplet constriction is detected at time t31, the shortcircuit Iw is reduced, and the process proceeds to the arc period.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

In the present invention, the material of the welding wire is aluminum or its alloy, an arc period and a short-circuit period are repeated between the welding wire and the base metal, the welding wire is fed forward during the arc period, and the welding wire is welded during the short-circuit period. The present invention relates to a forward and reverse feed arc welding method in which wire is fed in reverse 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 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, a forward and reverse feed arc welding method is used in which the welding wire is fed forward during the arc period and fed backward during the short circuit period for welding.

Furthermore, when the material of the welding wire is steel, current control is performed to detect signs of arc generation from the short-circuit period and rapidly reduce the welding current to several tens of amperes in order to reduce the amount of spatter generated. The sign of arc occurrence is detected by detecting the occurrence of a constriction in the droplet and an increase in the resistance value of the droplet. For this reason, this current control is called constriction detection control.

When the material of the welding wire is aluminum or its alloy (hereinafter referred to as aluminum material), its resistance value is small, so that it becomes difficult to detect the occurrence of constriction due to an increase in the resistance value. For this reason, it is not possible to perform constriction detection control that detects a sign that an arc will occur during the short-circuit period and rapidly reduces the welding current. As a result, there was a problem in that the amount of spatter generated increased.

In order to deal with the above problem, in the invention of Patent Document 1, the welding current is controlled so that the average value of the maximum value of the welding current during the short circuit period is 150A or less.

Patent No. 7075705

In forward and reverse feed arc welding in which the welding wire is an aluminum material, when the average value of the welding current is less than 150 A, high-quality welding with less spatter generation can be performed by applying the conventional technology. However, if the average value of the maximum welding current during the short-circuit period is controlled to be 150A or less as in the conventional technology, there is a problem that the welding condition becomes unstable when the average value of the welding current exceeds 150A. Occur.

Therefore, in the present invention, it is possible to perform high-quality welding with less spatter generation even when the average value of the welding current is less than 150 A or more than 150 A in forward and reverse feed arc welding in which the welding wire is made of aluminum material. The purpose is to

In order to solve the above-mentioned problem, the invention of claim 1:
The material of the welding wire is aluminum or its alloy, and an arc period and a short-circuit period are repeated between the welding wire and the base metal, the welding wire is fed forward during the arc period, and the welding wire is fed forward during the short-circuit period. In the forward and reverse feed arc welding method, which welds by feeding the welding wire in reverse,
When the average value of the welding current is less than the reference current value, the welding current less than the average value of the welding current is applied during the short circuit period,
When the average value of the welding current is equal to or higher than the reference current value, the welding current equal to or higher than the average value of the welding current is applied during the short-circuit period, and the constriction of the droplet is then detected during the short-circuit period. reducing the welding current to transition to the arc period;
This is a forward and reverse feed arc welding method characterized by the following.

The invention of claim 2 is:
The detection of the constriction is performed when the duration of the short circuit period reaches a reference time,
2. The forward and reverse feed arc welding method according to claim 1.

The invention of claim 3 is:
Detecting the constriction time from detecting the constriction to transitioning to the arc period, calculating an average value of the constriction time every predetermined period, and setting the reference time based on the average value of the constriction time. ,
3. The forward and reverse feed arc welding method according to claim 2.

According to the forward and reverse feed arc welding method in which the welding wire is an aluminum material according to the present invention, high-quality welding with little spatter generation can be performed even if the average value of the welding current is less than 150 A or more than 150 A. .

1 is a block diagram of a welding power source for carrying out a forward and reverse feed arc welding method according to an embodiment of the present invention. The timing of each signal in the welding power source of FIG. 1 when the value of the welding current average value setting signal Iar indicating the forward and reverse feed arc welding method according to the embodiment of the present invention is equal to or greater than the value of the reference current value setting signal Itr It is a chart. The timing of each signal in the welding power source of FIG. 1 when the value of the welding current average value setting signal Iar indicating the forward and reverse feed arc welding method according to the embodiment of the present invention is less than the value of the reference current value setting signal Itr It is a chart.

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

FIG. 1 is a block diagram of a welding power source for carrying out a forward and reverse feed arc welding method according to an embodiment of the present invention. Each block will be explained below with reference to the same figure.

The power control unit PM inputs a commercial power source (not shown) such as a three-phase 200V, 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, thereby controlling the welding wire 1. A welding voltage Vw and a welding current Iw are supplied between the base metal 2 and the base metal 2. Although not shown, this power control unit 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. Forward feeding refers to forward feeding of the welding wire in a direction approaching the base material, and reverse feeding refers to feeding backward in a direction away from the base material. 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. The material of the base material 2 is aluminum or its alloy. A shielding gas (not shown) such as argon gas is ejected from the tip of the welding torch 4.

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 welding current average value setting circuit IAR outputs a predetermined welding current average value setting signal Iar for setting the average value of the feed rate Fw. In consumable electrode arc welding, the average value of welding current Iw is set by the average value of feed rate Fw.

The forward feed peak value setting circuit WSR outputs a normal feed peak value setting signal Wsr calculated by inputting the above-mentioned welding current average value setting signal Iar to a predetermined function.

The reverse feed peak value setting circuit WRR outputs a reverse feed peak value setting signal Wrr calculated by inputting the above-mentioned welding current average value setting signal Iar into a predetermined function.

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 average constriction time calculation circuit TSA inputs the current decrease signal Nd described later and the above-mentioned short circuit determination signal Sd, and from the time when the current decrease signal Nd changes to High level for a short time, the short circuit determination signal Sd goes to Low level (arc period). Detects the constriction time Ts until the constriction time changes to , calculates a moving average value of the constriction time Ts at predetermined intervals, and outputs an average constriction time calculation signal Tsa. The above-mentioned predetermined cycle is a cycle at which a short circuit occurs, and is set to about 3 to 10 cycles. Therefore, each time a short circuit occurs, the average value of the constriction time Ts of the predetermined cycle immediately before the short circuit is calculated.

The squeezing time setting circuit TSR outputs a squeezing time setting signal Tsr for setting a target value of the squeezing time Ts. This value is set to about 0.5 ms.

The reference time setting circuit TNR inputs the average constriction time calculation signal Tsa and the constriction time setting signal Tsr, calculates Tnr=Tni+∫G・(Tsa−Tsr)・dt, and generates the reference time setting signal Tnr. Output. Here, Tni is a predetermined initial value, and is set to 4 ms, for example. G is a predetermined amplification factor. Therefore, the reference time setting signal Tnr is set based on the average constriction time calculation signal Tsa. Furthermore, the reference time setting signal Tnr is set by feedback control so that the value of the average constriction time calculation signal Tsa and the value of the constriction time setting signal Tsr are equal. The constriction formation state is in the reference state in a state before the short circuit ends and the arc re-occurs by the value of the constriction time setting signal Tsr. If the welding current is reduced at this timing, the welding current will reach a desired low level current value at the time of arc re-occurrence.

The current reduction timer circuit ND inputs the above-mentioned short-circuit discrimination signal Sd and the above-mentioned reference time setting signal Tnr, and calculates the elapsed time since the short-circuit discrimination signal Sd is at a high level (short-circuit period) and changed to high level. When the time reaches the reference time Tn determined by the reference time setting signal Tnr, the current reduction signal Nd which becomes High level for a short time is output.

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 current comparison signal Cm and the current reduction signal Nd, changes to Low level when the current reduction signal Nd changes to High level, and then changes to Low level when the 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 normally Return to state.

The first arc period setting circuit TA1R outputs a predetermined first arc period setting signal Ta1r.

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 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 reference current value setting signal ITR outputs a predetermined reference current setting signal Itr. The reference current setting signal Itr is set to 150A, for example.

The short circuit current setting circuit ISR receives the above welding current average value setting signal Iar, the above reference current value setting signal Itr, the above short circuit determination signal Sd, the above low level current setting signal Ilr, and the above current reduction signal Nd. , performs the following processing and outputs the short circuit current setting signal Isr.
1) When the value of the welding current average value setting signal Iar is greater than or equal to the value of the reference current value setting signal Itr The short circuit current setting signal Isr changes to a predetermined initial period when the short circuit discrimination signal Sd changes to High level (short circuit period) During the period, the current becomes a predetermined initial setting value, and thereafter increases to a predetermined short-circuit peak setting value at a predetermined short-circuit slope and maintains that value. After that, when the current decrease signal Nd changes to High level, it becomes the value of the low level current setting signal Ilr.
2) When the value of the welding current average value setting signal Iar is less than the value of the reference current value setting signal Itr The short circuit current setting signal Isr is the value obtained by subtracting a predetermined value (about 50 A) from the welding current average value setting signal Iar. .

The current control setting circuit ICR includes the short circuit determination signal Sd, the low level current setting signal Ilr, the first arc period signal Sta1, the third arc period signal Sta3, and the first arc current setting signal Ia1r. , the above third arc current setting signal Ia3r and the above short circuit current setting signal Isr are 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 discrimination signal Sd changes to High level (short-circuit period), the current control setting signal Icr having the value of the short-circuit current setting signal Isr is output.

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 the 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 shows the welding power source of FIG. 1 when the value of the welding current average value setting signal Iar is greater than or equal to the value of the reference current value setting signal Itr, which shows the forward and reverse feed arc welding method according to the embodiment of the present invention. It is a timing chart of each signal. 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, the same figure (F) shows the time change of the third arc period signal Sta3, and the same figure (E) shows the time change of the third arc period signal Sta3. (G) shows the time change of the current decrease signal Nd. The operation of each signal will be explained below with reference to the same figure.

The reference current setting signal Itr is set in a range of 100 to 200A, for example, 150A. Therefore, the figure shows the operation when the average value of the welding current is 150A or more. When the average value of the welding current exceeds the reference current value, a large amount of spatter will occur unless waist detection control is performed. On the other hand, as will be described later with reference to FIG. 3, if the average value of the welding current is less than the reference current value, less spatter will occur even if the constriction detection control is not performed. Therefore, in this embodiment, the control of the short circuit current is switched depending on whether the average value of the welding current is greater than or equal to the reference current value or less than the reference current value.

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. The forward feed peak value Wsp and the reverse feed peak value Wrp are set by a function using the welding current average value setting signal Iar of FIG. 1 as input. 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 -40 m/min.

As shown in FIG. 1B, the welding current Iw during the short circuit period from time t1 to t4 is constant current controlled by the short circuit current setting signal Isr shown in FIG. The short circuit current 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.

When the elapsed time from the start of the short-circuit period at time t1 reaches the reference time Tn, it is estimated that the constriction formation state has reached the reference state, and at time t31, as shown in FIG. Nd changes to High level for a short time. The reference time Tn is set by the reference time setting signal Tnr shown in FIG. Furthermore, the reference time setting signal Tnr is set by feedback control so that the value of the average constriction time calculation signal Tsa in FIG. 1 and the value of the predetermined constriction time setting signal Tsr in FIG. 1 are equal. The average constriction time calculation signal Tsa is calculated by performing a moving average of the constriction time Ts over a predetermined period. The constriction time Ts is a period from time t31 when the current reduction signal Nd becomes High level to time t4 when the arc occurs again. For example, the short circuit from time t1 is the mth short circuit, the predetermined period is 3, and the constriction times during the predetermined period are Ts(m-3), Ts(m-2), and Ts(m-1). Then, the average constriction time calculation signal Tsa(m) in the m-th short circuit period is calculated as follows.
Tsa(m)=(Ts(m-3)+Ts(m-2)+Ts(m-1))/3
The point in time when the reference time Tm has elapsed is a point in time before the short circuit ends and the arc occurs again by the value of the constriction time setting signal Tsr, and it is assumed that the constriction formation state is in the reference state. This is the point in time. For example, the short circuit period is about 5 ms, the value of the constriction time setting signal Tsr is about 0.5 ms, and the reference time Tn is about 4.5 ms. As described above, the reference time Tn can be automatically set to an appropriate value under various welding conditions.

When the material of the welding wire is steel, constriction is detected by an increase in the resistance value of the droplet or the voltage. However, when the welding wire is made of aluminum, it is difficult to detect the constriction by increasing the voltage because the increase in resistance due to the constriction is small. Therefore, in this embodiment, the constriction is detected when the duration of the short circuit period reaches the reference time. In forward and reverse feed arc welding, the repetition period between the short circuit period and the arc period is much more stable than in general constant speed feed arc welding. As a result, the formation of a constriction during the short-circuit period is also stabilized, so that the state of constriction formation can be accurately detected based on the elapsed time of the short-circuit period. However, the reference time changes depending on welding conditions such as the average value of welding current, welding speed, and welding posture. For this reason, in this embodiment, the reference time is automatically set to an appropriate value using the constriction time as an index. As a result, even when the material is made of aluminum, the detection accuracy of constrictions can be improved. That is, in this embodiment, when the average value of the welding current is equal to or higher than the reference current value, the formation of a constriction is promoted by applying a short circuit current equal to or higher than the average value of the welding current, and then the constriction of the droplet is It detects the short circuit current and reduces it to transition to the arc period. In this way, even when the average value of the welding current is equal to or higher than the reference current value, stable welding with less spatter generation is possible.

At time t31, as shown in FIG. 1G, in response to the current reduction signal Nd becoming High level for a short time, the drive signal Dr in FIG. 1 becomes Low level, so that the transistor TR in FIG. is turned off, and the current reducing resistor R shown in FIG. 1 is inserted into the current carrying path. 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 the time when the current reduction 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.

[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 5 ms. Further, for example, the normal feed peak value Wsp is set 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. For example, the delay period Tc is about 1 ms, the first arc period Ta1 is about 1 ms, and the first arc current Ia1 is about 400 A.

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. Although the second arc period Ta2 is not a predetermined value, it is approximately 4.5 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 0.5 ms.

FIG. 3 shows the welding power source of FIG. 1 when the value of the welding current average value setting signal Iar is less than the value of the reference current value setting signal Itr, which shows the forward and reverse feed arc welding method according to the embodiment of the present invention. It is a timing chart of each signal. 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, the same figure (F) shows the time change of the third arc period signal Sta3, and the same figure (E) shows the time change of the third arc period signal Sta3. (G) shows the time change of the current decrease signal Nd. The operation of each signal will be explained below with reference to the same figure.

In the figure, the operations other than the short-circuit period from time t1 to t4 are the same as those in FIG. 2, so the description will not be repeated. Further, during the short-circuit period, the operation of the feeding speed Fw shown in FIG. This figure shows a case where the value of the welding current average value setting signal Iar is less than the value of the reference current value setting signal Itr, so the waist detection control is not performed. For this reason, the current reduction signal Nd shown in FIG. 2G remains at the Low level, so the transistor TR in FIG. 1 is turned on and the current reducing resistor R in FIG. 1 is short-circuited.

As shown in FIG. 1B, the welding current Iw during the short circuit period from time t1 to t4 is constant current controlled by the short circuit current setting signal Isr shown in FIG. The short circuit current is a constant value obtained by subtracting a predetermined value (about 50 A) from the value of the welding current average value setting signal Iar. As shown in FIG. 3C, the welding voltage Vw has a short circuit voltage value of several volts.

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.

When the average value of the welding current is less than the reference current value, the short circuit current is set to a value less than the average value of the welding current, and the constriction detection control is not performed. Even if the short circuit current is a small value that is less than the average value of the welding current, since the welding wire is fed backwards, it is possible to smoothly transition to the arc period. Furthermore, since the short circuit current is a small value less than the average value of the welding current, there is less occurrence of spatter. If constriction detection control is performed when the average value of the welding current is less than the reference current value, since constriction detection accuracy is not 100%, spatter may increase when a constriction is erroneously detected. Therefore, when the average value of the welding current is less than the reference current value, necking detection control is not performed.

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 IAR Welding current average value setting circuit Iar Welding current average value 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 ISR Short circuit current setting circuit Isr Short circuit current setting signal ITR Reference current value setting circuit Itr Reference current value setting signal Iw Welding current ND Current reduction timer circuit Nd Current reduction signal PM Power control unit R Current reduction resistor SD Short circuit determination circuit Sd Short circuit determination signal STA1 1st arc period circuit Sta1 1st arc period signal STA3 3rd arc period circuit Sta3 3rd Arc period signal SW Power supply characteristic switching circuit TA1R First arc period setting circuit Ta1r First arc period setting signal Tc Delay period Td Current drop time Tn Reference time TNR Reference time setting circuit Tnr Reference time setting signal 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 TSA Average constriction time calculation circuit Tsa Average constriction time calculation 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 TSR Waist time setting circuit Tsr Waist time setting signal 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 (3)

The material of the welding wire is aluminum or its alloy, and an arc period and a short-circuit period are repeated between the welding wire and the base metal, the welding wire is fed forward during the arc period, and the welding wire is fed forward during the short-circuit period. In the forward and reverse feed arc welding method, which welds by feeding the welding wire in reverse,
When the average value of the welding current is less than the reference current value, the welding current less than the average value of the welding current is applied during the short circuit period,
When the average value of the welding current is equal to or higher than the reference current value, the welding current equal to or higher than the average value of the welding current is applied during the short-circuit period, and the constriction of the droplet is then detected during the short-circuit period. reducing the welding current to transition to the arc period;
A forward and reverse feed arc welding method characterized by: The detection of the constriction is performed when the duration of the short circuit period reaches a reference time,
The forward and reverse feed arc welding method according to claim 1. Detecting the constriction time from detecting the constriction to transitioning to the arc period, calculating an average value of the constriction time every predetermined period, and setting the reference time based on the average value of the constriction time. ,
The forward and reverse feed arc welding method according to claim 2.

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