JPH01205875A - Method and device for controlling consumable electrode arc welding - Google Patents

Abstract

PURPOSE:To surely control the occurrence of spatters by controlling to reduce a welding current up to a prescribed value in the course till the arc regeneration from detecting a constriction and detecting the time till the arc is generated from detecting the constriction to determine the detection reference of the constriction. CONSTITUTION:When a construction phenomenon (d) of a globule is changed by the change of device setting conditions and others, the change is detected as the time till the arc regeneration (f) from detecting the constriction. When the detection time becomes longer than the proper time, while the reference to detect the constriction of the next globule is determined in the direction where a point of time to detect the construction comes close to a point of time of the arc regeneration, when the detection time becomes shorter than the proper time, the above-mentioned reference is determined in the direction where the point of time to detect the constriction is separated from the point of time of the arc generation. By this method, the time till the arc is regenerated from detecting the constriction is made to the proper time and thrusting into base metal of a consumable electrode and the occurrence of spatters are controlled surely. Welding work is stabled most and the spatters are reduced by setting the above-mentioned proper time at 100-300musec.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for controlling consumable electrode arc welding including short-circuit transitions.

[Prior art] In consumable electrode arc welding, in which welding is performed while repeatedly shorting and generating an arc between the welding wire and the base metal, the general process of droplet formation and transfer is shown in Figure 8. (,) ~
It is as shown in (f).

In Fig. 8, 11 is the welding wire, 12 is the base material, and 13 is the droplet. (a) shows the arc generation state immediately before the short circuit (b) shows the initial state of the short circuit when the droplet is in contact with the molten pool ( In c), the contact between the droplet and the molten pool is ensured and the droplet is moving; in the short-circuit intermediate state (d), the droplet is moving toward the molten pool, creating a constriction between the welding wire and the droplet. The late short circuit state (e) is the moment when the short circuit is broken and a welding arc is generated (f) is the arc generation state where the welding wire melts and a droplet grows, and the processes of (a) to (f) are repeated. It will be done.

In such a process, it has been revealed that a large amount of spatter is generated at the moment when the short circuit is broken and the welding arc is generated again, that is, at the moment shown in FIG. 7(e).

Due to complaints from users due to this spatter, the 7th
A method for suppressing the occurrence of spatter during the process shown in FIG. 3(e) has been put into practical use.

That is, while the droplet 13 is short-circuited to the base metal 12, the welding current is set to a predetermined short-circuit current, and the droplet 13 short-circuited due to the pinch effect.
As shown in Figure 7(d), the welding current is restarted by detecting the increase in voltage ΔV due to the increase in resistance, and when this value exceeds the preset reference voltage value, the welding current starts to constrict as shown in Figure 7(d). The re-arc initial current is reduced to the minimum possible for arcing, and the transfer of the constricted droplet 13 to the molten pool is alleviated.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, in order to detect the constriction of the droplet 13 and reduce the welding current to the re-arc initial current, even if the output is controlled, the impedance of the welding current attenuation path Therefore, the desired welding current cannot be reduced substantially.

In the "control method and apparatus for welding power source" disclosed in Japanese Patent Application Laid-Open No. 59-206159, which improves this point, a switch interposed in the welding current attenuation path is turned off in synchronization with the reduced output of the welding current, An impedance element provided in parallel with the switch promotes a reduction in welding current.

But in fact, semi-automatic welding in use.

Variations in equipment settings such as wire extension, wire feed speed, and welding speed during automatic welding, changes in welding conditions by the operator, and external disturbances such as molten pool fluctuations that vary significantly depending on the welding position. Due to the droplet size, shape,
Due to variations in viscosity, etc., droplet transfer occurred while the welding current was being reduced after the constriction was detected [see Figure 7 (e)].
may be completed. In such a case, the welding current cannot be sufficiently reduced, resulting in spatter. As described above, in order to reliably suppress the occurrence of spatter, there is a problem that cannot be solved by the conventional technology that only shortens the reduction time of the welding current.

The present invention aims to solve these problems, and provides control for consumable electrode type arc welding that can reliably suppress the generation of spatter without being affected by fluctuations in the constriction phenomenon of droplets. An object of the present invention is to provide a method and an apparatus thereof.

[Means for Solving the Problems] In order to achieve the above object, the consumable electrode arc welding control method of the present invention detects the constriction of the droplet (a sign of the end of the short circuit), and from the detection of this constriction, the arc welding In addition to controlling the welding current to drop to a predetermined value until the arc reoccurs, the time from detection of the constriction to the reoccurrence of the arc is detected, and the criteria for detecting the next constriction of the droplet is determined according to the detection time. (Claim 1).

In addition, in the above control method, the standard for detecting the next constriction of the droplet is determined based on the comparison result between the above detection time and a predetermined set time. It is preferable to set it as 100-300 microseconds (Claim 2).

On the other hand, the control device for consumable electrode type arc welding of the present invention includes a welding power source that controls the output of DC voltage by on/off operation of one or more switching elements to control the welding current, and a control device for controlling the welding current from the welding power source. A detector applies welding current between the consumable electrode and the base metal to detect conditions from short circuit to arc generation, and the output from the detector is compared with a predetermined reference value to detect the constriction of the droplet ( A comparator that detects a sign of the end of a short circuit (a sign of the end of a short circuit), and an output means that outputs the predetermined reference value of the comparator, and the output means determines the occurrence of an arc based on the output from the detector and outputs the result. a time detector that detects the time from when the comparator detects constriction to when the determiner outputs an arc occurrence determination;
A calculator that calculates and outputs the difference between the preset appropriate time from constriction detection to arc generation and the detection time from the time detector, and determines the constriction of the next droplet according to the output from the calculator. The present invention is characterized in that it comprises a setting device that outputs and sets a predetermined reference value for detecting to the comparator (claim 3).

In addition, in the above control device, in order to improve the attenuation characteristic of the welding current, a switch means is inserted in the welding current attenuation path and turns off in accordance with the output from the comparator, and a switch means is connected in parallel to the switch means. A power supply circuit may be provided for applying a predetermined DC voltage to both ends of the capacitor connected to the capacitor (Claim 4).

Furthermore, in order to keep the attenuation rate of the welding current constant, the power supply circuit may include an adjustment circuit that maintains the voltage applied across the capacitor at a predetermined value (claim 5); It is preferable to include a regeneration circuit that regenerates the voltage that exceeds a predetermined value out of the applied voltage into the primary side DC voltage of the welding power source (Claim 6).

[Function] In the above-described control method for consumable electrode type arc welding of the present invention,
Changes in equipment setting conditions, changes in welding conditions.

When the constriction phenomenon of a droplet changes due to variations in the condition of the droplet, the change is detected as the time from detection of constriction to arc re-occurrence. If the detection time becomes longer than the appropriate time, the standard for detecting the next droplet constriction is determined so that the constriction detection point is closer to the arc re-occurrence point, while the detection time If the time is shorter than the appropriate time, the criterion is set such that the necking detection time point moves away from the arc re-occurrence time point. As a result, the time from the detection of the constriction to the re-occurrence of the arc becomes an appropriate time, and the penetration of the consumable electrode into the base material and the occurrence of spatter are reliably suppressed.

Note that by setting the appropriate time to 100 to 300 μsec, welding workability is most stable and spatter is reduced.

Furthermore, the control device for consumable electrode arc welding of the present invention described above is used directly when carrying out the method, and in this device, the constriction of the droplet is detected by a detector and a comparator. At this time, the predetermined reference value set in the comparator to detect the waist is appropriately set by the output means.

The method of setting the predetermined reference value by this output means is in accordance with the method described above, in which the comparator 2 determiner and the time detector detect the time from the detection of the constriction to the re-occurrence of the arc, and the calculation unit and the setting The predetermined reference value is determined by the device based on the detection time and the appropriate time.

Furthermore, the switch means that turns off in response to the output from the comparator (detection of the constriction of the droplet) is designed to cause the current in the welding current attenuation path to flow into the capacitor in the power supply circuit and absorb its energy. As a result, a current decay characteristic having a linear and steep falling slope can be obtained.

Further, the adjustment circuit works to maintain the voltage across the capacitor constant and to keep the attenuation rate of the welding current constant. Further, the regeneration circuit maintains the voltage across the capacitor constant, keeps the attenuation rate of the welding current constant, and works to reduce energy loss when the current attenuates.

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

FIG. 1 is a circuit diagram showing a control device for consumable electrode type arc welding as a first embodiment of the present invention, in which 1 is a torch, 2 is a welding wire (consumable electrode), 3 is a base material, and the welding wire is 2 is fed from a feeder (not shown). In addition, L is a linactor, DI and D2 are rectifier diodes, El is a commercial AC power supply, DBI is a diode bridge that rectifies the AC voltage from the AC power supply E1 to DC voltage, C1 is a smoothing capacitor, and SWI to SW4 are switching elements. , T1 is a transformer, and these AC power supply El, diode bridge DBI, capacitor C1, and switching element 5WI
-5W4 and transformer T1 constitute a welding power source E.

5 is a driver that turns on/off the switching elements SW1 to SW4 based on a predetermined signal from a circuit not shown; here, the switching elements SWI, S
W4 and SW2. SW3 is turned on and off alternately as a set, and M is controlled so that the welding current (2) becomes the set current value. 6 is an arc voltage detection circuit (detector) including an amplifier that detects and amplifies the arc voltage (electrical change from short circuit to arc generation) between the torch 1 and the base material 3; 7 is a comparator; A detection signal is received from the voltage detection circuit 6, and the detection signal is transmitted after the short circuit starts [Fig.
b)], when the constriction detection level (predetermined reference value) set by the output means 8, which will be described later, is reached, the constriction of the droplet [a sign of the end of the short circuit; see Fig. 8 (d)] is detected. It outputs a high level signal. Although not shown in FIG. 1, the point in time when the droplets of the welding wire 2 begin to contact the molten pool of the base metal 3 (the point in time when short circuiting starts) is
A short circuit detection circuit that detects from the output of the arc voltage detection circuit 6 is provided.

In addition, 8 sets the constriction detection level in the comparator 7.
An output means for outputting an arc occurrence determiner 8a that determines when an arc occurs based on the voltage detection signal from the arc voltage detection circuit 6 and outputs the result. A time detector 8b detects the time (TA) until a judgment is output, and a preset appropriate time (TA) from constriction detection to arc occurrence.
A deviation calculator 8c calculates and outputs the difference between T1) and the detection time (TA) from the time detector 8b, and detects the constriction of the next droplet according to the output from the deviation calculator 8c. and a waist detection level setter 8d that outputs and sets the waist detection level (predetermined reference value) to the comparator 7.

Furthermore, SWD is a switching element (switch means) inserted in the welding current supply path (welding current attenuation path) between the diode D1 (D2) and the welding cable 4, and 9 is a switching element that turns on this switching element SWD. / off control driver, and the signal from comparator 7 is Low
When the level rises from high to high, the output signal goes low.
OW level to turn off the switching element SWD.

Note that the driver 9 is configured to turn on the switching element SWD again when the welding current I decreases to a predetermined current value. Further, when the driver 5 receives a low level signal from the driver 8, it turns off all of the switching elements SWI to SW4.

On the other hand, Po is a constant voltage power supply (power supply circuit), and commercial AC power supply E2. Transformer T2. Diode bridge DB2. It is composed of a resistor R1, a switching element SW5, and a capacitor C2. Capacitor C2 is connected in parallel to switching element SWD via backflow prevention diode D3. Further, the AC voltage from the AC power source E2 is rectified into a DC voltage by the diode bridge DB2 via the transformer T2, and is applied to the capacitor C2. Furthermore, resistor R1 and switching element SW5
is provided in parallel to the capacitor C2, and a constant DC voltage V is applied across the capacitor C2 by turning on/off the switching element SW5 by a control circuit (not shown). is applied. These resistor R1 and switching element SW5 constitute an adjustment circuit that maintains the voltage applied across the capacitor C2 at a predetermined value.

The control device for consumable electrode type arc welding according to the first embodiment of the present invention is constructed as described above, so by using the device of this embodiment, the method of the present invention can be carried out by operating as follows. It will be implemented.

First, an AC power source E1 is rectified by a diode bridge DB1, smoothed by a capacitor C1, and converted into a DC power source. Then, the high frequency alternating current whose output is controlled by turning on/off the switching elements SWI to SW4 by the driver 5 is stepped down via the transformer T1. Normally, the switching element SWD is in the on state, so the welding current I rectified by the diodes Di and D2 is supplied to the torch 1 → welding wire 2 → base metal 3, and the arc voltage is applied between the welding wire 2 and base metal 3. being applied between.

Short-circuit transferred arc welding is performed.

The droplet transfer process in this short-circuit transfer arc welding is the 8th
As explained in FIGS. (a) to (f), after the droplet from the welding wire 2 contacts the molten pool of the base material 3 [at the start of short circuit;
See Figure 8(b)], the droplet moves to the molten pool side and a constriction begins to form between the welding wire 2 and the droplet [Figure 8(d)]
reference〕. At this point, the arc voltage between the torch 1 and the base material 3 detected by the arc voltage detection circuit 6 increases. When this arc voltage reaches the constriction detection level, the comparator 7 determines that constriction has occurred, and a high level signal is output to the driver 9. Accordingly, the driver 9 operates, and the switching elements SWI to SW4 and SWD are driven and controlled to be in the off state.

As a result, the welding current I flows in the order of welding wire 2 → base metal 3 → transformer T1 → diode D 1 (D 2) → diode D3 → capacitor C2 → reactor L → torch 1 → welding wire 2 and is attenuated. During this current decay, in this embodiment, the welding current flows into the capacitor C2 and its energy is absorbed, and the voltage across the capacitor C2 increases somewhat, but the switching element SW5 can be turned on/off by a control circuit (not shown). So, capacitor C2
The energy stored in the resistor R1 is consumed by the resistor R1.

Therefore, the voltage across capacitor C2 is always a constant value v0
will be maintained.

Here, switching elements SWI to SW4 and SWD
■ The welding current when turned off. Then, the damping current factor can be expressed isometrically by the following equation.

x=t, -(v0/L)・t However, I o < Vo / RA, I>01RA
is the resistance of the welding wire 2, t is the time, and the voltage V across the capacitor C2 is adjusted by the adjustment circuit consisting of the switching element SW5 and the resistor R1. is kept constant, so
The current attenuation rate V, /L is constant. Also, various circuit constants are l0=400A, 1=50μH, Vo=40
If 0V-RA=20 mΩ, the attenuation current I based on the above equation will have an attenuation characteristic as shown by the symbol a in FIG. According to this, it is clear that a current decay characteristic having a linear and steep falling slope can be obtained, and 8
The decay time to 0A is 40 μsec.

Note that the reference numeral in FIG. 3 is a curve showing the current attenuation characteristic when a 1Ω resistor is provided as an impedance element in parallel to the switching means (switching element 5WD of this embodiment) in the conventional device. Comparing curves a and b, it can be seen that in this example, the decay time from 400A to 8OA is reduced to approximately 1/2 in a short time.

Furthermore, FIG. 4 shows the relationship between the voltage v swo applied to the switching element SWD and the time required for the welding current to decrease from 40 OA to 80 A, and the symbol C is according to this embodiment. , symbol d indicates a conventional device (when a resistor R is provided as an impedance element). As is clear from comparing these curves c and d, in this example, if the voltage applied to the switching element SWD is the same, the decay time is a short time of about 172. On the contrary, in order to obtain the same decay time, it is found that in this embodiment, it is sufficient to use the conventional switching element SWD having a breakdown voltage of about 172.

Furthermore, the above attenuation rate is the voltage v0 across the capacitor C2.
However, if the welding current ISP at the time of a short circuit is the same as the welding current at the previous short circuit, the welding current after constriction detection can be changed by adjusting the slope at the time of the previous welding current control (
The re-arc initial current IRA is controlled to decrease to a predetermined re-arc initial current IRA at the same slope as the welding current attenuation rate).

As described above, when the welding current decreases from the short circuit current (Isp) to a predetermined current value (re-arc initial current IRA), the driver 9 again switches the switching element SWD.
turns on, and the switching element SWI~
SW4 is also turned on/off driven by the driver 5 as usual. Thereafter, the above-described operations are repeated.

By the way, while performing arc welding by repeating the above operations, the constriction detection level (predetermined reference value) set in the comparator 7 is changed as follows by the operation of the output means 8 as the constriction changes. Determined/settings changed. Figures 2 (a) and (b) are for explaining this, and show the welding voltage ■ and welding current during the process from the formation of a constriction in the droplet to arc generation when moving from short circuit to arc generation. This is a schematic enlarged view of the waveform of the mechanical process.

As shown in FIGS. 2(a) and (b), the constriction detection time t
. When the time from t1 to re-arc generation time t1 is appropriate, the appropriate time is T, and the change in voltage due to the constriction of the droplet is ΔV□.

Here, the time from when the welding current ■ is reduced to the predetermined re-arc initial current IRA until the re-arc occurs is approximately several tens of tens of seconds.
However, as a result of experiments, the probability that the welding wire 2 will penetrate into the base metal 3 increases rapidly when the time is 500 μsec or more, while the
It was found that when the welding current is below c, an arc occurs and spatter increases before the welding current is lowered to the re-arc initial current IRA. In particular, it has been confirmed that about 100 to 300 μsec is the range in which welding workability is most stable and spatter is reduced, and it is preferable to set this value as the appropriate time T.

Now, the time t when the arc occurs after the constriction detection time t0
2 is later than the proper arc occurrence time 11 (=111+T1), and if that time becomes longer than T2 (>T,), the timing of lowering the welding current is too early, causing re-arc. This means that the short circuit remains at the initial current IRA for a long time.

Therefore, the possibility that the welding wire 2 will penetrate into the base metal 3 increases, so in the next step, the constriction detection level is corrected to a value Δv2 higher than ΔV□ according to the detection time T2,
Delays the timing of lowering the welding current. As a result, the time from constriction detection to arc generation is the appropriate time T□
manipulated to return to .

On the other hand, the constriction detection time t. The time t when the arc occurred after
, is earlier than the appropriate arc generation time 11 (=1°+T,), and if that time becomes short to T, (<T,), the timing of lowering the welding current is relatively late. Therefore, an arc occurs immediately after the welding current is lowered, and there is still strong movement of the molten end of the wire due to the inertia of the strong electromagnetic force caused by the short circuit current. Therefore, the risk of spatter generation increases, so in the next process, the detection time T,
The constriction detection level is set to a value Δv3 lower than ΔV according to
The timing for lowering the welding current has been made earlier.

As a result, the time from constriction detection to arc generation is operated to return to the appropriate time T1.

The re-arc initial current IRA for suppressing spatter and stably continuing welding is 3O-150.
Grade A is desirable.

In addition, when modifying the constriction detection level according to the detection time from constriction detection to arc generation, the constriction detection level may be given as a function of detection time and the correction may be made based on this function, or the constriction detection level may be corrected based on this function. It may be corrected in proportion to the deviation ΔT from the time T□ (this is applied to the apparatus of this embodiment and will be described later). Further, an appropriate dead zone may be provided to provide an area that is not modified.

Next, the specific operation of the output means 8 having the function of determining the constriction detection level in the comparator 7 as described with reference to FIGS. 2(a) and 2(b) will be described.

The arc occurrence determination device 8a in the output means 8 receives the voltage detection signal from the arc voltage detection circuit 6, determines whether there is a short circuit or an arc occurrence, and outputs a high level signal when an arc occurs. . Then, the time detector 8b detects the time TA from receiving the constriction detection signal (f (high level signal)) of the comparator 7 until receiving the output of the arc occurrence determiner 8a, and outputs it to the deviation calculator 8c. The deviation calculator 8c calculates the deviation ΔT (=TA-T) between the above-mentioned appropriate time T1 set in advance and the detection time TA, and the constriction detection level setter 8d calculates the deviation ΔT (=TA-T) from the deviation calculator. A new constriction detection level (ΔV+a・ΔT) is output by adding a value a・ΔT (a is a proportionality constant) proportional to the deviation ΔT to the previous constriction detection level ΔV, and this is used in the next process in the comparator 7. Set as the constriction detection standard.

Now here, the detection time TA is greater than the appropriate time T,
If the deviation ΔT is a positive value, the welding current is lowered too early because the constriction detection level is small, so the new constriction detection level is increased to ΔV+a·ΔT. Conversely, when the detection time is appropriate MT, the deviation is small and the deviation ΔT
If becomes a negative value, the waist detection level is large and the timing of lowering the welding current is too late, so the new waist detection level is reduced to ΔV + a·ΔT.

The constriction detection level changed in this way is set in the comparator 7, and in the next process, the new constriction detection level is compared with the voltage detection signal from the arc voltage detection circuit 6, and constriction is detected. . As a result, in the process from the next generation of constriction to the droplet to arc generation, when the welding voltage V reaches the changed constriction detection level, the comparator 7
outputs a constriction detection signal.

Therefore, the initial constriction detection level is a certain reference level Δ
V□, and thereafter, the output means 8 repeats the above-mentioned operation every time a constriction occurs in the droplet, thereby controlling the constriction detection level so that the detection time TA becomes the appropriate time T□. Become.

Below, the results of experiments conducted by actually applying the method and apparatus of the present invention are shown. However, the welding wire is YGWI 2 (
Diameter 1,2+m), shielding gas is Co2 gas (15
The base material is S P CC (3,2t), the average welding current is 165A, the average welding voltage is 20V, the wire feeding speed is 4.5m/min, and the welding speed is 7Qcpm.

After welding under these conditions for 20 minutes, the weight of spatter adhering to the shield gas nozzle was measured and the results are shown in Table 1 below. As is clear from Table 1, the amount of spatter was significantly reduced.

Table 1 As described above, according to the consumable electrode arc welding control method and device of the present embodiment, the output means 8 detects the next constriction detection level in the comparator 7 from constriction detection to arc re-occurrence. Since the settings can be changed as appropriate depending on the time, it is possible to control the application time of the re-arc initial current IRA, and to always maintain the time from lowering the welding current to the time when the arc re-occurs at the appropriate time T1. , can adapt to fluctuations in droplet transfer due to disturbances during use.

Spatter can always be reliably suppressed.

In addition, in this example, occurrence of constriction (a sign of end of short circuit)
is detected as an increase in arc voltage, the switching element SWD is turned off in response, and the current in the welding current attenuation path flows into the capacitor C2 with a constant voltage across both ends, and the energy is absorbed, resulting in a linear Since a current decay characteristic with a steep falling slope (see Fig. 3) can be obtained, the welding current T can be reduced to a low welding current (re-arc initial current IRA) in a very short time after constriction occurs.
This makes it possible to effectively attenuate the amount of spatter, thereby making it possible to more reliably suppress the occurrence of spatter.

As a result, various adverse effects caused by sputtering can be eliminated, and its industrial value is extremely large.

In this embodiment, as an example of means for detecting constriction, a method is explained in which the arc voltage (change in short circuit voltage) is compared with the constriction detection level. It is also possible to detect a change in the current value and compare it with the constriction detection level, and any means that can detect constriction, which is a sign of the end of a short circuit, may be used.

Further, according to this embodiment, as explained with reference to FIG. 4, there is an effect that the withstand voltage of the switching element SWD can be lowered compared to the conventional device.

In addition, in this embodiment, if the welding current is rapidly reduced not only when a constriction occurs but also immediately after a short circuit, it is possible to prevent spatter caused by the current increase immediately after a short circuit. Additionally, when the welding current falls below a predetermined low welding current, switching element SWD is turned on to suppress the welding current from falling too much, thereby preventing arc breakage during arc regeneration. .

In addition, in this embodiment, the current attenuation characteristic when all of the switching elements SWI to SW4 and SWD are turned off when the occurrence of constriction is detected is explained, but the welding power source of the present invention According to the method, only the switching element SWD is turned off.

Even if all of the switching elements SWI to SW4 are not turned off, the same effects as described above can be obtained. In other words,
When only the switching element SWD is turned off,
If the no-load voltage of the welding power source is Vp, the attenuation current Ia is I a" I o (Vo Vp)" t / L
Although the attenuation slope (attenuation rate) becomes somewhat smaller, a linear slope is still obtained, and even if the attenuation target value is set to a low current, attenuation can be performed quickly and in a short time. For example, when only the switching element SWD is turned off, the time t required to attenuate the welding current from 400A to 8OA is given by t=L(Io Ia)/(Vo Vp), assuming Vp=70V. =5
0.(400-80)/(400-70) 48 seconds.

Further, in this embodiment, the adjustment circuit is configured by the resistor R1 and the switching element SW5, but a Zener diode may be used instead.

Next, a welding power source as a second embodiment of the present invention will be described. FIG. 5 is a circuit diagram thereof. Note that in FIG. 5, the same reference numerals as those already described indicate the same parts, so the explanation thereof will be omitted. In addition, in FIG. 5, the arc voltage detection circuit 6. Comparator 7. Output means 8.
The illustration of the driver 5.9 is omitted.

As shown in FIG. 5, the second embodiment has almost the same structure as the first embodiment, but the constant voltage power supply POI (power supply circuit) in the second embodiment has the same configuration as the first embodiment. Instead of the resistor R1 in the voltage source po, a flywheel diode D4. An energy regeneration circuit composed of a transformer T3 and a diode D5 is provided.

This energy regeneration circuit uses capacitor C2 at the time of current decay.
The energy stored in the capacitor C1 is regenerated into the capacitor C1 by the on/off operation of the switching element SW5. That is, the voltage applied across the capacitor c2 that exceeds the predetermined value v0 is regenerated into the primary side DC voltage of the welding power source, and the voltage across the capacitor C2 is kept at a constant value V.

The goal is to maintain it.

As a result, the second embodiment not only provides the same effects as the first embodiment, but also makes it possible to suppress energy loss during current decay, and at the same time keep the current decay rate constant. It is possible to maintain it.

In addition, in the first and second embodiments described above, the case is explained in which the main circuit of a unipolar welding power source is provided with a full bridge type inverter, but the welding power source of the forward/reverse polarity switching type is also The arc phenomenon is the same in each case. Therefore, by providing the switching element SWD and the constant voltage power source PO (POI) in the welding current attenuation path, the present invention can also be applied to a forward/reverse polarity switching type welding power source as in the first and second embodiments. can be applied to obtain similar effects.

Also, in the case of power supplies using half-bridge type inverters and chopper types as shown in Figs. 6 and 7, respectively,
The present invention provides a switching element SWD and a constant voltage power supply P.
By providing O (POI) in the welding current attenuation path,
It can be applied in the same manner as in the first and second embodiments, and the same effects can be obtained. However, in FIGS. 6 and 7, symbol E represents a DC power supply, 5WIA and 5WIB represent switching elements, and T represents a transformer.

A Zener diode may be used instead of the capacitor provided in parallel with the switching element SWD of the constant voltage power supply in each of the above embodiments. Furthermore, instead of the backflow prevention diode D3, a switching means synchronized with the operation of the switching element SWD or the like may be used.

[Effects of the Invention] As detailed above, the consumable electrode type arc welding control method and device of the present invention provide the following effects.

The predetermined value (constriction detection level) for the next standard in the comparator is changed as appropriate depending on the detection time from detection of constriction to arc re-occurrence, so the time from lowering the welding current to the point of arc re-occurrence is always appropriate. In addition to being able to maintain the time, it can also adapt to fluctuations in droplet transfer caused by disturbances during use.
Spatter can always be reliably suppressed, various harmful effects caused by spatter are eliminated, and extremely large industrial value can be obtained.

By setting the correction time to 100 to 300 μsec, welding workability becomes extremely stable and spatter is significantly reduced.

In addition, when a constriction is detected, the switch means is turned off in response to this, so that the current in the welding current attenuation path flows into a capacitor with a constant voltage across both ends, and the energy is absorbed, resulting in a linear and steep curve. Since a current attenuation characteristic with a falling slope can be obtained, it is possible to effectively attenuate the welding current to the re-arc initial current in a very short time after constriction occurs, and the generation of spatter can be suppressed more reliably. .

As mentioned above, since high current attenuation characteristics can be obtained, the attenuation time can be shortened and the withstand voltage of the switch means can be lowered compared to conventional devices. Even in the off state, a current attenuation characteristic having a linear and steep falling slope can be obtained.

Further, by providing the adjustment circuit, the voltage across the capacitor can be maintained constant, and the attenuation rate of the welding current can be kept constant at all times.

Furthermore, by providing a regenerative circuit, the voltage across the capacitor can be maintained constant, the attenuation rate of the welding current can always be kept constant, and energy loss during current attenuation can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a control device for consumable electrode type arc welding as a first embodiment of the present invention, and FIGS. 2(a) and (b) and FIGS. 5 is a circuit diagram showing a control device for consumable electrode type arc welding as a second embodiment of the present invention, and FIG. 6 is a graph for explaining the operation of the invention.
, 4 are circuit diagrams showing modified examples of a control device for consumable electrode type arc welding to which the present invention is applied, and FIG. 8 (
a) to (f) are diagrams showing the transfer process of droplets on the consumable electrode. In the figure, 2 - welding wire (consumable electrode), 3 - base material, 5 - driver, 6 - arc voltage detection circuit, 7 -
Comparator, 8 - Output means, 8a - Arc occurrence determination device, 8b - Time detector, 8 c - Deviation calculator, 8
d.--Constriction detection level setter, 9-.Driver,
PO, POI-・Constant voltage power supply (power supply circuit), C2・-
Capacitor, R1-resistor, SWI to SW5...-switching element, SWD...-switching element (switching means), E--welding power source. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Patent applicant: Kobe Steel, Ltd.

Claims (6)

[Claims] (1) A control method for consumable electrode arc welding, in which welding is performed by repeatedly shorting and generating an arc between the consumable electrode and the base metal, by detecting the constriction of the droplet, which is a sign of the end of the short circuit. The welding current is controlled to drop to a predetermined value between the detection of the constriction and the re-occurrence of the arc, and the time from the detection of the constriction to the re-occurrence of the arc is detected, and the constriction of the next droplet is detected according to that detection time. A control method for consumable electrode type arc welding, characterized by determining a standard. (2) A criterion for detecting the constriction of the next droplet is determined by comparing the detection time with a predetermined set time, and the set time is set to 100 to 300 μsec. The control method for consumable electrode type arc welding described. (3) Welding in which the welding current is controlled by output-controlling the DC voltage through on/off operations of one or more switching elements in order to perform welding by repeatedly short-circuiting and arcing between the consumable electrode and the base metal. In a control device for consumable electrode arc welding equipped with a power source, a detector that applies a welding current output from the welding power source between the consumable electrode and the base material to detect conditions from short circuit to arc generation. a comparator that compares the output from the detector with a predetermined reference value to detect a constriction of the droplet that is a sign of the end of a short circuit; and an output means for outputting the predetermined reference value in the comparator. Equipped with
The output means includes a determiner that determines and outputs arc occurrence based on the output from the detector, and a time detector that detects the time from when the comparator detects the constriction to when the determiner outputs an arc occurrence determination. a calculator that calculates and outputs the difference between a preset appropriate time from constriction detection to arc generation and the detection time from the time detector;
A consumable electrode type characterized by comprising a setting device that outputs and sets a predetermined reference value to the comparator for detecting the constriction of the next droplet according to the output from the computing device. Arc welding control device. (4) A predetermined DC voltage is applied across a switch means inserted in the welding current attenuation path and turned off in response to the output from the comparator, and a capacitor connected in parallel to the switch means. 4. The control device for consumable electrode type arc welding according to claim 3, further comprising a power supply circuit. (5) The control device for consumable electrode type arc welding according to claim 4, wherein the power supply circuit includes an adjustment circuit that maintains the voltage applied to both ends of the capacitor at a predetermined value. (6) A claim characterized in that the power supply circuit has a regeneration circuit that regenerates the voltage applied to both ends of the capacitor that exceeds a predetermined value into the primary DC voltage of the welding power source. Item 4. A control device for consumable electrode type arc welding according to Item 4.