JP2001321940A - Welding power supply controller and consumable electrode gas shielded arc welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding power supply controller and a welding equipment with which the detachment of an actual droplet can be electrically, surely and simply detected and the waveform of the welding power supply after the detachment of the droplet can be controlled as it is prescribed in consumable electrode gas shielded arc welding. SOLUTION: The welding power supply controller 101 is equipped with a welding power supply device 111 which is continuous and connected to a consumable electrode wire and a material to be welded. and the above welding power supply device is controlled by the welding power supply controller 101 in a consumable electrode gas shielded are welding device performing arc welding in a shielded gas atmosphere. The welding power supply controller 101 is equipped with a droplet transfer detecting part 102 detecting the detachment of the droplet from the tip part of a consumable electrode wire and outputting a droplet detaching signal and a welding power supply waveform controlling part 103 controlling a welding power supply waveform after the detachment of the droplet according to the droplet detaching signal from the above droplet transfer detecting part 102. The time differential signal of a welding voltage/welding current is found from the welding voltage and the welding current and the detachment of the droplet is detected by the droplet transfer detecting part 102 according to this time differential signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a consumable electrode gas shielded arc welding apparatus for performing arc welding using a consumable electrode in a shield gas atmosphere, and a welding power supply control apparatus used in the apparatus.

[0002]

2. Description of the Related Art In consumable electrode gas shielded arc welding,
As the consumable electrode wire is consumed, droplets are formed at the tip of the wire. The droplet formed at the tip of the wire has a certain size as a result of various forces acting on the droplet, such as gravity, arc reaction force, current pinch force, and droplet surface tension. Material to be removed (base material)
A weld bead is continuously formed on the base material by a phenomenon of dropping into a molten pool, that is, so-called droplet transfer, and welding is performed.

The lower part of the droplet formed at the tip of the wire acts as an anode for arc discharge, and the molten pool acts as a cathode. When the stability of the arc is deteriorated, the droplets are irregularly and greatly affected, so that the droplets are liable to cause a so-called spatter phenomenon. Particularly in carbon dioxide gas shielded arc welding in which carbon dioxide or a mixed gas containing carbon dioxide as a main component is used as a shielding gas, since the arc is relatively converged, a large upward reaction force against the droplet is generated. When the droplet operates and the droplet is unstable, the droplet is blown off by the reaction force. Also, when the droplet is detached and the arc re-lights on the molten pool and the tip of the wire, a sudden arc reaction acts on the tip of the wire and blows away the remaining hot water or molten pool after the droplet is detached, generating spatter. It's easy to do. This phenomenon occurs remarkably when the arc current is large and the fluctuation of the arc state (arc length, arc position) is large. This poses a serious problem particularly when high-speed large-current welding using a carbon dioxide-based shielding gas or high-efficiency welding with a large amount of deposition is performed.

Factors causing large fluctuations in the arc length and position include fluctuations in the feeding speed of the welding wire, fluctuations in the cathode spot due to instability of the droplet form, relighting of the arc due to detachment of the large droplet, A sudden change in impedance due to a short circuit of the droplet, or the like can be considered. Conventionally, these instability factors have been eliminated by improving the wire feedability by optimizing the lubricant, stabilizing the roller feed by improving the wire surface, or stabilizing the droplet shape by improving the wire composition. (Increase in surface tension) or irregular fluctuation of the arc length due to the promotion of regular detachment of droplets and prevention of short circuit in the molten weld pool are employed.

[0005] One of the methods for reducing spatters due to irregular fluctuations of the arc length due to the promotion of regular droplet detachment and prevention of short circuit in the molten pool is to use a pulse power supply as a welding power supply. This method is disclosed in
As disclosed in JP-A-16743, JP-A-7-47473, JP-A-8-267238, etc., a welding current waveform in which a peak current and a base current are repeated at a constant period is set, and a peak current is given. During the base current period, the shape and position of the droplet are stabilized, and the so-called one-pulse, one-transition power supply waveform control is performed to prepare for the next droplet separation. It is intended to achieve droplet transfer.

However, in these methods, the current waveform is controlled so as to make the average transition period of the droplet coincide with the pulse period in order to realize one droplet per droplet transition. Since the pulse is applied regardless of the timing, it is difficult to accurately synchronize the pulse with the transition period. Therefore, when the timing of droplet detachment comes during the peak current, since the current value after droplet detachment is high, droplets that have started to form at the wire tip are blown off by strong arc moss and spatter occurs. . On the other hand, if the droplet does not detach during the peak current and the timing of detachment of the droplet is shifted during the base current, the droplet cannot be detached in many cases, deviating from the transition from one pulse to one droplet. The droplet transfer phenomenon becomes unstable, resulting in problems such as short-circuiting with the molten pool and spattering of large particles. Thus, in the above method, since the power supply waveform is not controlled in accordance with the timing of the droplet detachment, a situation occurs in which the droplet detachment timing and the phase of the current waveform are reversed,
On the contrary, spatter was often increased.

To address this problem, various attempts have been made to detect the detachment timing of the droplet and control the current waveform in accordance with the timing. These methods are disclosed in JP-A-8-267239, JP-A-8-290270, JP-A-8-318375, and JP-A-9-854.
39, JP-A-10-272591, etc., the welding current or the welding voltage, and further, these time-varying signals are used to set a certain set value at which it is determined that the drop of the droplet occurs. If it exceeds, it is determined that the droplet has detached, and the detachment of the droplet is detected, and the welding current waveform is controlled based on the droplet detachment signal output thereby.

According to these methods, the detachment of the droplet is promoted by using a temporary high current (peak current),
By quickly dropping to a low current (base current) together with the detection of detachment, it is possible to prevent the droplets at the wire tip from scattering due to re-arcing under high current conditions, and to drop droplets at an appropriate timing. Formation and shape stabilization can be promoted.

[0009]

In these techniques, it is necessary to accurately detect the detachment of the droplet. That is, in order to suppress the spatter immediately after the droplet is detached, almost at the same time as the detachment of the droplet, at least within the time required for the arc to re-light on the base material and the wire tip at least continuously (usually 1 hour).
Within less than msec), the welding current must be reduced promptly. In addition, it is necessary to accurately detect the timing of droplet separation for forming and shaping the droplet subsequent to droplet separation. If the detection of droplet detachment is later than the actual detachment, the state of high current is maintained even after the droplet actually detaches, and spatter occurs. Also, if the detection of droplet detachment is earlier than the actual detachment, the current value will decrease before the actual detachment of the droplet, and the detachment of the droplet will be further delayed, and in extreme cases the tip of the wire will melt. It spills into the pond, causing a large amount of spatter.

Conventional methods for detecting droplet detachment include a method for determining that droplet detachment has occurred when the welding voltage exceeds a reference voltage for determining that droplet detachment has occurred, a welding current or a welding current. A time differential of the voltage is obtained, and a detection method is employed in which the separation of the droplet occurs when the time differential signal exceeds a reference value. In other words, the arc impedance that determines the welding current characteristics and welding voltage characteristics depends on the shape of the wire tip, the distance between the wire and the base material, the elements injected into the arc (shielding gas, evaporation flux, wire components, etc.) and the arc. Plasma components depending on temperature, etc.
Influenced by the density, etc., the distance between the base metal and the wire tip increases, especially as the droplet moves at the wire tip, and the cathode spot moves sharply (flying from the droplet to the undissolved wire tip as the droplet moves) Shifting) causes a sharp and large fluctuation in the arc impedance. In the conventional method for detecting droplet detachment, the detachment of droplets is detected by utilizing a change in welding current or welding voltage caused by such a large change in arc impedance.

However, when droplet detachment is detected by comparing a welding current or a welding voltage, or a time differential signal thereof, with a threshold value at which droplet detachment is determined to occur, actually, power supply noise (thyristor noise) is detected. ,
There is a problem that many extra pulses other than the droplet detachment signal are detected due to the influence of inverter noise, other noise appearing in the current conversion circuit, and disturbance noise). In this case, measures to remove the noise component by setting a high threshold value to avoid the influence of noise or providing a low-pass filter are taken.However, the signal corresponding to the impedance change due to the detachment of the droplet and the power supply noise are removed. Cannot be properly distinguished, and even if such measures are taken, there is a risk that the droplet detachment timing corresponding to the actual droplet detachment may be overlooked.

Also, for example, a power supply operating at a constant voltage does not have an ideal constant voltage control (output impedance = 0), but actually has a finite output resistance and a current smoothing circuit in the output circuit. In the case of ideal constant voltage control, the steep change that should appear in the welding current is not actually seen, and a missing pulse error that overlooks the departure timing occurs. There are many things. Therefore, it is difficult to accurately detect droplet detachment, and it has been difficult to stably perform the intended waveform control after droplet detachment.

FIG. 16 shows waveforms of an output current (welding current) and an output voltage (welding voltage) in a consumable electrode gas shielded arc welding apparatus using a constant voltage control welding power source. It can be seen that noise peculiar to the power supply appears, and it is difficult to detect the droplet detachment signal separately from these noises. FIG. 16 shows an output waveform of a welding power source having a general constant voltage characteristic, and a change in the waveform accompanying the detachment of the droplet appears more frequently in the voltage waveform. FIG. 17 shows a voltage-time differential signal waveform obtained by differentiating the welding voltage. This signal also has an influence of noise, and the pulse other than the pulse (black arrow in the figure) accompanying the actual droplet detachment is shown. Many pseudo pulses (white arrows in the figure) are observed. The black arrow was confirmed by observing the actual droplet detachment timing with a high-speed camera.

The present invention has been made in view of such a problem, and in the consumable electrode gas shielded arc welding, the actual detachment of the droplet can be detected electrically and simply and easily. It is an object of the present invention to provide a welding power source control device capable of controlling a welding power source waveform in a predetermined manner, and a welding device using the same.

[0015]

SUMMARY OF THE INVENTION A welding power supply control device according to the present invention includes a welding power supply device for conducting connection between a consumable electrode wire and a material to be welded, and a consumable electrode gas shielded arc for performing arc welding in a shield gas atmosphere. A welding power supply control device for controlling the welding power supply device in the welding device, the droplet transfer detection unit detecting a detachment of the droplet from the tip of the consumable electrode wire and outputting a droplet detachment signal; A welding power supply waveform control unit that controls a welding power supply waveform after droplet detachment based on a droplet detachment signal from the droplet transfer detection unit, wherein the droplet transfer detection unit determines a welding voltage based on a welding voltage and a welding current. /
A time differential signal of the welding current is obtained, and detachment of the droplet is detected based on the time differential signal.

The droplet shift detecting section may be provided with a discriminating means for discriminating the time differential signal based on a threshold value at which the droplet is determined to be detached. Further, the droplet transfer detecting section is provided with an analog circuit for outputting a time differential signal of the welding voltage / welding current based on the welding voltage and the welding current, and the analog circuit has a cut-off frequency of 10 kHz or more. It is desirable to have characteristics and to have a time constant sufficiently lower than the average droplet transfer interval.
In addition, the droplet transfer detection unit has a sampling rate of 1 k
It is preferable that the differential signal of the welding voltage / welding current sampled at Hz or more is divided by the sampling interval to obtain a time differential signal of the welding voltage / welding current. In addition, the welding power supply control device is configured such that after the droplet detachment signal is output from the droplet transition detection unit, the droplet detachment detection is not performed for a predetermined period shorter than the average droplet transition interval. Processing means may be further provided.

In the consumable electrode gas shielded arc welding apparatus of the present invention, a consumable electrode wire is supplied, and a welding torch for supplying a shielding gas to an outer peripheral portion thereof is connected to the consumable electrode wire and a material to be welded. And a welding power supply control device for controlling a power supply waveform of the welding power supply device, wherein the welding power supply control device is used as the welding power supply control device.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A welding power supply control device 101 according to the present invention.
Is preferably used for controlling a welding power supply device in a consumable electrode gas shielded arc welding using a carbon dioxide gas-based shielding gas. As shown in FIG. Is connected to a welding power supply unit 111 having an inverter and electrically connected to the welding power supply unit 111 having an inverter. The welding before and after the droplet detachment is performed based on the droplet detachment signal. A welding power supply waveform control unit 103 for controlling a power supply waveform. The output side of welding power supply device 111 is electrically connected to a welding torch and a workpiece (base material).

The droplet transfer detecting section 102 calculates an arc impedance, that is, a welding voltage / welding current and a time differential signal thereof based on the welding voltage and welding current input from the voltage detector V and the current detector A. 105
And a discriminating means 106 for discriminating a time differential signal of the arc impedance as a threshold using a reference value determined to cause droplet detachment, and outputs a droplet detachment signal when the time differential signal exceeds the threshold. Is done. The welding power supply waveform control unit 103 controls the welding power supply waveform so as to be a set power supply waveform, and switches the waveform before and after the droplet detachment by the droplet detachment signal.

The present invention is characterized in that a droplet detachment signal is generated based on a time differential signal of arc impedance. By generating a droplet detachment signal based on a change in impedance of a welding arc caused by droplet detachment, instead of a single signal of the welding current or welding voltage, the actual droplet detachment timing can be accurately grasped. In other words, a large change in the arc state due to droplet detachment appears as a change in the waveform of the welding current or welding voltage, but by taking the time derivative of the arc impedance that allows the change in the arc state to be monitored more directly, The change in the arc state can be found as a large signal change. In addition, since a signal truly caused by the arc change can be extracted, for example, power supply noise can be removed from a droplet detachment signal based on true droplet detachment. There are various methods of obtaining the arc impedance by modulating the waveform of the power supply output. However, in the present invention, since the DC component of the arc impedance, that is, the welding voltage / current is monitored, there is no need to use a special probe waveform, and the method is simplified. Droplet migration detection can be performed.

FIG. 2 shows a waveform of a time differential signal of arc impedance (welding voltage / welding current) when a welding power supply device of constant voltage control is used.
The pseudo pulse due to the power supply noise indicated by 7 is removed, and a pulse-like steep arc impedance time differential signal is generated only near the actual droplet detachment timing.
From this, most of the false pulses caused by power supply noise are
It can be seen that it is removed in the process of signal processing of welding voltage / welding current. This is based on the fact that the change in the DC component of the arc impedance is not affected by power supply noise.

By the way, when detachment of the droplet occurs, FIG.
As can be seen from FIG.
In the differential signal waveform of welding voltage / welding current, it is observed that several pulse-like signals are generated with one droplet detachment. This is a phenomenon caused by a sharp change in the position of the arc point between the droplet and the molten pool as the droplet separates, and is similar to chattering seen in switches of electrical contacts. Such chattering causes an overestimation of the number of transfers in the detection of droplet detachment. The occurrence of chattering is concentrated within a very short time interval as compared to the time interval between transfer of the next droplet. From this, false recognition of droplet detachment due to chattering is performed by performing insensitive processing to prevent a droplet detachment signal generated within a fixed time smaller than the average droplet transfer interval from being processed as a true droplet detachment signal. That can be avoided.

For this reason, as shown in FIG. 1, the insensitive processing means 108 for performing the insensitive processing to the welding power supply control device 101.
Is preferably provided. Insensitive processing means 1
In step 08, after receiving the first droplet detachment signal at the time of droplet detachment, the welding power supply waveform control unit 103 is controlled so that an apparent droplet detachment signal generated by chattering is not input.
An opening / closing gate 109 may be provided between the apparatus and the droplet transfer detection unit 102, and may be closed for a predetermined time (called a dead time) under the control of the opening / closing control unit 110. The dead time may be set directly by a timer, and / or indirectly using the dead integrated power that is a fixed reference value smaller than the integrated power supplied before the droplet formation and transition. It may be set manually. In addition,
When the dead integrated power is used as the dead time, an integrator for integrating the welding power with time can be used as the measuring means.

The time differential signal of the arc impedance can be obtained by an analog circuit including a divider for calculating the arc impedance (welding voltage / welding current) and a differentiator for differentiating the arc impedance signal. Further, the welding current and welding voltage are sampled at an appropriate period, the welding current / welding voltage is intermittently obtained, and the change value obtained by dividing the difference of the arc impedance signal before and after the sampling interval by the interval is used as the arc. It can be a time differential signal of the impedance.
By sampling, high-frequency power noise (for example, switching noise of a pulsed inverter) can be easily eliminated by setting an appropriate sampling frequency, and recording as digital information can be easily performed. This is convenient for performing intelligent control. However, an appropriate noise filter can be used to remove power supply noise.

FIG. 4 shows a signal waveform of welding voltage / welding current obtained by sampling when carbon dioxide shielded arc welding is performed using a 1.2φ Cu plated solid wire. The welding voltage and welding current were sampled at a sampling frequency of 25 kHz using an AD converter. The difference between the welding voltage and the welding current before and after the sampling interval is obtained, and this difference is divided by the sampling interval to obtain a time-differentiated signal waveform shown in FIG. A discriminator of threshold = 200 Ω / sec was set for this time differential signal, and the detachment of the droplet was detected by setting the time from receiving the initial droplet detachment signal to reaching the integrated power of 100 joules as the dead time. The drop separation signal train is shown in the lower part of FIG.
In the upper part of FIG. 6, the waveform of the welding voltage / welding current and the actual droplet transfer timing observed by the high-speed camera are shown by vertical broken lines. As shown in FIG. 6, the droplet detachment signal obtained by the droplet transfer detection unit 102 was obtained by differentiating the welding current or welding voltage so far, although some extra pulses still remained. It can be seen that the detection accuracy for the signal is significantly improved.

Next, the present invention will be described more specifically with reference to examples, but the present invention is not construed as being limited to the examples. For example, the droplet transfer detection unit and the welding power supply waveform control unit according to the present invention may be configured to output welding voltage and welding current to A
It can be realized by D-converting and processing the obtained digital signal by a computer.

[0027]

[Embodiment 1] FIG. 7 is a functional block diagram showing an overall configuration of a consumable electrode gas shield pulse arc welding apparatus according to an embodiment. This welding apparatus uses a consumable electrode wire W wound around a spool 122. Is electrically connected between a welding torch 121 supplied with a supply motor 123 and supplied with a shielding gas from a carbon dioxide gas source (not shown), the consumable electrode wire W and the base material M, and a welding power And a welding power supply control device 101 for controlling a power supply waveform of the welding power supply device 111. The welding power supply device and the welding power supply control device have the same functions as those shown in FIG.

The wire W is fed toward the welding torch 121 by a wire feed roller driven by a feed motor 123, and an arc discharge is generated between the wire W and the base material M to perform welding. The feed motor control circuit 124 controls the rotation speed of the feed motor 123 based on the wire feed speed set by the output setting device 19 attached to the welding power source control device 101.

The welding power supply 111 converts commercial three-phase AC power into welding power.
Conductive connection is made between the base material 21 and the base material M. The AC current supplied from the three-phase AC power supply unit provided in the factory is rectified into DC by the first rectifier circuit 2 and smoothed by the smoothing capacitor 3. This DC current is converted into a high-frequency AC current by the inverter 4, and the output of the inverter 4 is reduced to a welding voltage by the transformer 5. Transformer 5
Is rectified into a welding DC current by the second rectifier circuit 6, and the welding current is supplied to the welding wire W and the base material M via the smoothing reactor 7, and arc welding is performed. Is performed.

The welding power supply control device 101 includes a voltage detector 8 for detecting an arc voltage and a current detector 9 for detecting a welding current. The output (welding voltage) of the voltage detector 8 and the output (welding current) of the current detector 9 are provided to an inverter control unit 18, a divider 26 that outputs welding voltage / welding current, and a power multiplier 29.

The output control section 17 of the welding power supply control device 101 outputs a waveform generation signal from the waveform generator 16 so that the welding current waveform set by the waveform setting device 15 is output from the welding power supply device 111. In response, the inverter 4 is controlled. Further, the waveform generator 16 receives a trigger from a pulse trigger circuit 21 which operates upon receiving a droplet detachment signal output when the droplet transition detecting unit 102 detects that the droplet has detached from the wire tip. The switching control of the welding current waveform after droplet detachment is performed by a signal. As the welding current waveform set by the waveform setting unit 15, for example, as shown in FIG. 8A, a peak current P for promoting the separation of the droplet and a base current B for forming the droplet after the separation of the droplet. May be alternately repeated to form a square waveform. In this case, the waveform generator 16 switches the peak current waveform to the base current waveform according to the droplet detachment signal. Also,
As shown in FIG. 8 (B), a first peak current P1 for promoting the detachment of the droplet, a second peak current P2 for promoting the formation of the droplet at a current value lower than the first peak current after the detachment of the droplet, A multi-step waveform that alternately repeats a base current B for shaping the shape of a droplet can be provided. In the case of this multi-stage waveform, the waveform generator 16 switches the first peak current P1 to the second peak current P2 according to the droplet detachment signal.

The droplet transfer detector 102 receives the outputs of the current detector 8 and the voltage detector 9 as inputs and outputs the arc impedance (welding voltage / welding current) thereof, and differentiates the output. Differentiator 25 and differentiator 25
The analog pulse-like output signal from the discriminator is discriminated by a threshold set to the occurrence level of droplet detachment, a discriminator 24 for removing low-level noise, and an output signal from the discriminator 24 are shaped, and the threshold is set. A waveform shaper 23 is provided for outputting a droplet detachment signal (1-0 signal) in response to the exceeded pulse-like output signal. The waveform shaper 23
Is output to the pulse trigger 21 and the reset trigger 27 via the gate 22.
The threshold value of the discriminator 24 is set by the detection level setting device 14. When measuring the amount of spatter to be described later, a general-purpose single-channel pulse height analyzer was used as the discriminator 24 and the waveform shaper 23.

On the other hand, the welding input power multiplied by the power multiplier 29 is integrated by the integrator 28 and output as integrated power. After the value of the integrated input power of the integrator 28 is reset by a reset signal output from the reset trigger 27 based on the droplet detachment signal output from the droplet transfer detection unit 102, the integration is started. The integrated power signal from the integrator 28 is compared with power preset by the dead integrated power setting unit 12 by the comparator 30, and outputs a gate opening signal to the gate 22 after reaching a predetermined integrated power, Drop transition detection unit 1
02 to the pulse trigger 21 and the reset trigger 27. As a result, transmission of an apparent droplet detachment signal accompanying the chattering detected while the dead integrated power value is not reached is interrupted, and one droplet detachment signal is transmitted to the waveform generator 16 per droplet transfer. Then, a current waveform after droplet detachment is generated, and the inverter 4 is controlled via the output control unit 17.

The control of the gate 22 is also performed by the dead time setting unit 13. After the first droplet separation signal is input to the pulse trigger circuit 21, the gate 22 is closed for the set dead time. You. When controlling the welding power supply waveform by the multi-stage waveform, the first peak current and the second peak current are controlled.
An opening / closing signal is output from the waveform generator 16 to the gate 22 in accordance with the output level of the current waveform so that the gate 22 is opened and closed so that the detection of droplet transfer can be limited only to the peak period PT where the peak current flows.

Using a welding device equipped with the above welding power supply control device, using a φ1.2 mm Cu-plated solid wire (brand name MIX-50S: manufactured by Kobe Steel) as a consumable electrode wire, and using carbon dioxide gas as a shielding gas. Then, gas shield pulse arc welding was performed, and the amount of generated spatter was examined.

For comparison, as a droplet transfer detection unit of the welding power supply control device, the change in arc impedance is detected as a change in the voltage level in Comparative Example A and a change in the time derivative of the voltage waveform in Comparative Example B. Spattering occurs even when gas shielded pulse arc welding is performed under the same conditions as in the embodiment by a welding device equipped with a conventional welding power supply control device equipped with a conventional droplet transfer detection unit that outputs a droplet detachment signal based on The amount was investigated. As shown in FIG. 9, the droplet transfer detection unit based on the change in the welding voltage level used for comparison includes a detection level setting unit 41 for setting a reference voltage, a welding voltage and a reference voltage input from the voltage detector, and , A zero cross detector 43 that outputs a zero cross signal when the difference waveform becomes zero, and a waveform shaper 44 that receives the zero cross signal and outputs a droplet detachment signal. ing. When using the time differential value of the voltage waveform, the reference level of the welding voltage time differential signal is set by the detection level setting device, and a differentiator for differentiating the welding voltage is provided, and the differential signal output from the differentiator is provided. Is input to the subtractor 42.

As shown in FIG. 10, the amount of spatter generated is measured by moving the welding torch 121 along the length of the base material M, performing bead-on-plate welding on the upper surface thereof, Collection boxes 131 and 131 so as to surround the welded portion of the base material M so as to collect the scattered spatter.
Was carried out, and the amount of spatter collected in the collection box was measured.

The welding conditions for the embodiment and the comparative example were as follows: shielding gas flow rate: 25 l / min, wire feed speed: 10 m
/ Min, and wire protrusion length: 20 mm. Further, the waveform control of the welding current was performed so that the current waveform became a square waveform shown in FIG. In this case, the peak current: 380 A,
Base current: 150 A × 5 msec.

Regarding the droplet transfer detection conditions, the detection level was set to a value at which the amount of spatter generation takes the lowest value in the comparative example, that is, 42 V in the comparative example A and 500 V / sec in the comparative example B. . On the other hand, in Example, the amount of spatter generation was examined by setting the dead integrated power to 100 J and changing the discriminator level. At this time, the cutoff frequency of the analog circuit (divider, differentiator) of the droplet transfer detection unit was set to 100 kHz. Further, in order to check the required response speed of the arithmetic circuit of the divider and the differentiator, the time constant of the differentiator was set to 0.02 msec, which was sufficiently high, and droplet shift detection was performed using dividers having various cutoff frequencies. The stability was investigated.

FIG. 11 shows the relationship between the discriminator level and the amount of spatter generated in the droplet transfer detecting section of the embodiment. In addition, the results of droplet transfer detection according to the comparative example are also shown in the figure for reference. As can be seen from the figure, when the discriminator level is lowered, many extra pulses other than the droplet detachment signal accompanying the actual droplet transfer are detected, and spatter is increased. Conversely, when the discriminator level is increased, extra pulses due to noise are removed, but spatter is increased because a signal accompanying the actual droplet transfer is also overlooked. Under the conditions of the present embodiment, a discriminator level of 200 to 500 Ω / sec is appropriate, and by setting such a discriminator level, the embodiment is compared with a comparative example in which droplet transfer detection is performed in the related art. It can be seen that the amount of sputtering can be significantly reduced.

On the other hand, when the discriminator level is 20
FIG. 12 shows the result of examining the effect of the cut-off frequency of the analog circuit (divider, differentiator) of the droplet transfer detection unit while fixing to 0 Ω / sec. From FIG. 12, it can be seen that a stable spatter reduction effect can be obtained by setting the cutoff frequency to 10 kHz or more as the pass characteristic of the analog circuit.

[Second Embodiment] Using a welding device and a consumable electrode wire similar to those of the first embodiment, a shield gas pulse arc using a mixed gas of Ar gas and carbon dioxide gas (flow rate: 25 L / min) as a shield gas. Welding was performed and the amount of spatter generated was examined. Further, as a comparative example, droplet transfer detection is performed using a welding power supply control device including a droplet transfer detection unit that outputs a droplet detachment signal based on a time differential signal obtained by differentiating the voltage waveform, Under the same conditions, shield gas pulse arc welding was performed.

The amount of sputtering was measured in the same manner as in Example 1. In addition, the welding current waveform, in the examples and comparative examples,
The control was performed so as to obtain a multi-stage waveform shown in FIG. On this occasion,
First peak current P1: 480 A, second peak current P2:
330 A, peak time PT: 13 msec, base current: 1
10 A, base current supply time: 15 msec.

In the comparative example, the droplet transfer detection level was set to 800 V / sec at which the amount of generated spatter was the lowest. In the examples, welding was performed while changing the discriminator level. At this time, the cutoff frequency of the analog circuit of the divider and the differentiator was 100 kHz. In the embodiment, the dead integrated power is set to 70 J, the gate is closed during the base current supply period, and the gate is opened at the same time as the start of the supply of the peak current to detect droplet transfer.

FIG. 13 shows the relationship between the discriminator level and the amount of spatter generated in the embodiment. The figure also shows the amount of spatter generated in the comparative example in which the voltage change was processed as the shift detection data. It can be seen that, under the conditions of the embodiment, by setting the discriminator level to 200 to 600 Ω / sec, the spatter amount can be greatly reduced as compared with the conventional droplet transfer detection.

[Embodiment 3] Using a welding apparatus equipped with a welding power source control unit having a droplet transfer detecting unit for outputting a droplet detachment signal based on a time differential signal of a difference in arc impedance obtained by sampling. Carbon dioxide shielded pulse arc welding was performed to check the amount of spatter generated.

This welding power supply control device differs from the device of FIG. 7 in the droplet transfer detecting section, and this point will be described.
FIG. 14 is a block diagram of the droplet transfer detection unit 102 used in the present embodiment, and includes a divider 26, a difference detection differentiator 25A,
Consisting of a discriminator 24 and a waveform shaper 23,
The other configuration of the difference detection differentiator 25A is the same as that of FIG.

The difference detector / differentiator 25A includes a divider 26
Subtracted from an arc impedance signal input from a delay circuit 32 for delaying the signal by a delay circuit 32 for delaying this signal by a sampling interval (a reciprocal time of the sampling frequency), and outputting a difference signal.
A sampling frequency setting unit 34 for setting a sampling interval; a gate 36 for opening and closing a difference signal from the subtractor 33 by an opening and closing signal from a pulse generator 35 at each sampling timing;
And a divider 37 that divides the difference signal output from by the sampling interval time. This difference differentiator 25A allows the welding voltage /
A difference between the welding currents is obtained, a time change rate of the difference, that is, a time differential signal of the arc impedance is output to the discriminator 24, compared with a predetermined threshold value, and a droplet detachment signal is output from the waveform shaper 23. . The droplet transfer detection unit 25A discretely samples the arc impedance and takes the difference to mask the high-frequency noise generated in a pulsed manner, and to detect the impedance associated with the transfer of the droplet. Can be detected over time.

The sampling frequency was set variously, the discriminate level was adjusted so that the amount of spatter was minimized for each sampling frequency, and the dependency of the obtained spatter generation amount on the sampling frequency was examined. The result is shown in FIG. According to FIG. 15, the sampling frequency is 100
At Hz, the amount of spatters increases extremely, but it can be seen that an excellent spatter suppression effect can be obtained by increasing the sampling frequency to 1 kHz or more.

[0050]

According to the present invention, in consumable electrode gas shielded arc welding, arc impedance (welding voltage / welding current) is used as data serving as a basis for determining drop detachment.
Since the time differential signal is used, it is possible to accurately detect the actual droplet transfer timing with a simple configuration without being affected by power supply noise, thereby appropriately controlling the welding power supply waveform.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a welding power supply control device and a welding power supply device according to an embodiment of the present invention.

FIG. 2 Arc impedance (welding voltage / welding current)
5 is a waveform diagram of a time differential signal of FIG.

FIG. 3 is a partially enlarged view of a chattering portion of a time differential signal waveform of an arc impedance.

FIG. 4 is a waveform diagram of an arc impedance signal obtained by sampling.

FIG. 5 is a waveform diagram of a time differential signal of the arc impedance shown in FIG.

FIG. 6 is an arc impedance signal waveform diagram (upper stage) and an output diagram (lower stage) of a droplet detachment signal detected based on a time differential signal thereof.

FIG. 7 is an overall functional block diagram of a consumable electrode gas shielded arc welding apparatus provided with a welding power supply control device according to the embodiment.

FIG. 8 is a waveform chart showing two examples of set current waveforms in welding current waveform control.

FIG. 9 is a functional block diagram of a droplet transfer detection unit based on a conventional voltage change.

FIG. 10 is an explanatory diagram of a bead-on-plate welding procedure and a spatter collection procedure according to an example.

FIG. 11 is a graph showing the relationship between the discriminator level and the amount of spatter generated in Example 1.

FIG. 12 is a graph showing the relationship between the cutoff frequency of the analog circuit and the amount of spatter generated in the first embodiment.

FIG. 13 is a graph showing the relationship between the discriminator level and the amount of spatter generated in Example 2.

FIG. 14 is a functional block diagram of a droplet transfer detection unit used in the third embodiment.

FIG. 15 is a graph showing the relationship between the sampling frequency and the amount of spatter generation in Example 3.

FIG. 16 is a waveform diagram showing a welding voltage and a welding current when a consumable electrode gas shield arc welding is performed using a constant voltage control welding power source.

FIG. 17 is a waveform diagram of a welding voltage time differential signal obtained by time differentiating the welding voltage of FIG. 16;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Welding power supply control device 102 Droplet transition detecting unit 103 Welding power supply waveform control unit 105 Computing means 106 Discriminating means 108 Insensitive processing means 111 Welding power supply device

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4E001 AA03 BB06 DE04 4E082 AA01 AA02 AA04 AB03 BA01 BA04 BB02 DA01 EA11 EB11 EC04 EC14 EE03 EE05 EF28

Claims (6)

[Claims] 1. A welding power supply for controlling a welding power supply in a consumable electrode gas shielded arc welding apparatus for providing arc welding in a shield gas atmosphere, comprising a welding power supply for electrically connecting a consumable electrode wire and a workpiece. An apparatus, comprising: a droplet transfer detection unit that detects separation of a droplet from a tip end of a consumable electrode wire and outputs a droplet release signal; based on a droplet release signal from the droplet transfer detection unit. A welding power source waveform control unit for controlling a welding power source waveform after the droplet detachment, wherein the droplet transfer detection unit obtains a time differential signal of a welding voltage / welding current from the welding voltage and the welding current; A welding power supply control device that detects detachment of droplets based on signals. 2. The welding power supply control device according to claim 1, wherein the droplet transfer detection unit includes a discriminating unit that discriminates the time differential signal based on a threshold value at which it is determined that the droplet is detached. 3. The droplet transfer detecting section has an analog circuit for outputting a time differential signal of a welding voltage / welding current based on a welding voltage and a welding current, and the analog circuit has a cutoff frequency of 10 kHz. With the above passing characteristics,
3. The welding power source control device according to claim 1, wherein the welding power source control device has a time constant sufficiently lower than an average droplet transfer interval. 4. The method according to claim 1, wherein the droplet transfer detection unit obtains a time differential signal of the welding voltage / welding current by dividing a difference signal of the welding voltage / welding current sampled at a sampling rate of 1 kHz or more by a sampling interval. 2. The welding power supply control device according to 2. 5. The welding power supply control device according to claim 1, wherein after the droplet detachment signal is output from the droplet transition detecting unit, the droplet detachment detection is not performed for a predetermined period shorter than the average droplet transition interval. The welding power supply control device according to any one of claims 1 to 4, further comprising: 6. A welding torch to which a consumable electrode wire is supplied and which supplies a shielding gas to an outer peripheral portion thereof, a welding power supply device electrically connected to the consumable electrode wire and a workpiece, and the welding power supply device. A consumable electrode gas shielded arc welding device comprising: a welding power supply control device for controlling a power supply waveform of the welding power supply device, wherein the welding power supply control device according to any one of claims 1 to 5 is used as the welding power supply control device. Consumable electrode gas shielded arc welding equipment used.