JPS6178567A - Short-circuiting arc welding method and its device - Google Patents

Abstract

PURPOSE:To perform continuously the short-circuiting arc welding having a good efficiency by generating an arc forcibly with increasing rapidly an output current in case of no arc being caused even if the output current is controlled in the specified waveform in the short-circuiting section time. CONSTITUTION:An arc welding is performed with generating an arc 3 forcibly by feeding a consumable electrode 1 at constant speed. When a short-circuit is appeared from the arc 3 with the distance between the consumable electrode 1 and base material 2 being reduced gradually, a voltage detector 5 cuts off a voltage controlling circuit 6 with driving a switching circuit 11 and feeds to a load the output current Iz (Iz=Ia+Is+It) of an extraordinary waveform. In this case Ia is for the arc current immediately before short-circuiting, Is for the rising part set in advance, It for the changing part increasing linearly approximately according to the time lapse. When the arc 3 is not generated even with passing said output current Ia for the prescribed time t0, said output current Iz is increased (Ib) rapidly. The arc 3 can be thus generated forcibly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement in short-circuit transfer arc welding, and in particular, to ensure i8 droplet transfer in a short time by controlling the output current to a predetermined waveform during the short-circuit section. The present invention relates to a method and an apparatus for making it possible to more stably generate an I-reverse and to continuously perform efficient short-circuit transfer arcs.

The conventional short-circuit transfer arc welding method is to perform welding by generating an arc by alternately shorting and separating the consumable electrode from the base material while feeding the consumable TPI at a constant rate.

The problem in doing this is that it is strongly desired to suppress the occurrence of sbanking (which is particularly noticeable when a short circuit occurs and when an arc occurs), and to always generate an arc stably during welding.

Conventionally, in order to meet these demands, the delay characteristics of a DC reactor have been used to control the flow of short circuits. Not only is it a drawback to select a current, but also a very large time constant is required when the current changes.As a result, the required inductance reaches 100 μH, making it difficult to design and manufacture. There was a problem in that it was difficult and the manufacturing cost was high.

Furthermore, since the current during a short circuit is as large as several hundred amperes, a large inductance is required, and a very large glue handle is required. For this reason, in the past, a large inductance was obtained using an iron core, but in such cases, the problem of saturation of the iron core could not be ignored and various problems occurred.

Therefore, in recent years, output feeders have been developed to solve the steaming problems of DC reactors.

Various types of circuits have been proposed in which a phase delay element is inserted into the circuit to cause a phase delay in the output change in response to a change in the load, thereby essentially producing the effect of a DC reactor.

For example, the one proposed in Japanese Unexamined Patent Publication No. 112659/1983 is a representative example of the improved method.

In other words, this device uses a switching control method using a switching element to control the output of a DC source, and is equipped with a circuit that causes the output circuit to have a phase delay in response to fluctuations in the negative part. It is characterized by a circuit configuration that allows the amount of output to be adjusted to 1.' when the output increases and when the output decreases. This method has the advantage of being able to easily obtain the optimal output rise and fall speeds for welding, dramatically improving welding stability, and making it possible to control the bead shape.

Problems to be Solved by the Invention The present invention is a further improvement of the arc welding method using a phase delay element. The problem to be solved is to provide a short-circuit transitional arc welding method with high resistance to short circuits, and in particular, it is possible to change the output it at the time of a short circuit to a specific waveform, which has not been done in conventional methods. 1
i'41i, the above-mentioned problems are solved.

Means for Solving the Problems In order to solve the above problems, the present inventor has conducted various studies in implementing the short-circuit transitional arc welding method, and has patented the waveform of the output current during a short-circuit. By setting as described in the range, droplet transfer can be performed reliably in an extremely short time, and at the same time, the current value at the time of arc generation can be suppressed to promote heat generation for droplet transfer and stabilize the arc. The present invention was developed based on the knowledge that efficient arc welding can be performed by continuously generating arc welding.

That is, the method provided by the method of the present invention is a short-circuit transfer arc welding method in which short-circuiting and arc generation are alternately performed while feeding a consumable electrode at a constant speed, and when an arc is generated, constant voltage control is performed in a closed loop, In addition, in the event of a short circuit, the current control is switched to closed loop current control, and the waveform of the output voltage tjtIt supplied to the load during the short circuit section is changed to I, mIa + Is + It (here, I
a is the arc current immediately before the short circuit, Is is the preset rise, and I (is the change that increases approximately linearly over time), and the output current to the load is controlled during the short circuit section. If the next arc to be generated does not occur even after the current has been energized for a predetermined period of time, the output ti is rapidly increased to force the generation of an arc.
Let's be honest.

Furthermore, the apparatus provided for carrying out the method of the present invention includes:
An arc welding device configured by combining a constant voltage control circuit and a voltage control circuit, which drive a switching control circuit to make the output voltage and current supplied to the load into a closed loop II jM, and in particular, the above The constant voltage control circuit is driven by receiving an arc detection signal from a voltage detector that detects the load voltage when an arc occurs, and receives an output signal from the voltage detector to perform control set in advance in the switching control circuit. The current control circuit is driven by receiving a short circuit detection signal from the voltage detector, and the current control circuit outputs a drive signal according to the current value. The Ti current control circuit 1l-Ia+Is+It (herein,
Ia is the arc flowing just before the short circuit, Is is the preset rising edge, and I is the output that has developed a predetermined waveform determined by [I is the change that increases approximately linearly over time]. Current is supplied to the load during the short-circuit period, and if the next arc that should occur does not occur even after the output current has been applied to the load for a predetermined period during the short-circuit period, the output current is rapidly increased to prevent an arc. The gist of this is that the system is configured to force the occurrence of .

Functions and Effects of the Invention According to the method of the present invention, when an arc occurs, a constant voltage of 11II
When a short circuit occurs, it automatically switches to current control, and arc welding is performed continuously due to short circuit transition. When the output current I8 supplied to the load during the short-circuit section is normal, I - Ia + ls + It (where Ia is the arc t'dL that occurs just before the short-circuit, IS is the preset rising edge, and 1t is the time. This is a change that increases approximately linearly over time. Therefore, when a short circuit is detected by the voltage detector, the arc current Ia immediately before the short circuit is used as a reference. As the short circuit progresses, this current becomes approximately linear over time as the short circuit progresses. The increasing change (1) is captured. As a result, the load is rapidly heated by a large short-circuit current during the contact! As the contact resistance increases, this short-circuit current is supplemented by 11 minutes, or a change that increases over time, so the consumable electrode becomes a small droplet in an extremely short period of time, ensuring that At the same time as cutting, the current value at the time of arc generation is suppressed, and the melt a
Since it promotes heat generation for migration, a fine-grained bead can be obtained and efficient continuous welding work can be performed.

In addition, in the event of an abnormality in which the output current supplied to the load during a short circuit section is in a state where the next arc that should occur does not occur even if 5 loads are energized for a predetermined time, such as at the time of arc start, a preset function can be used. Since the large level current determined by the current setting device is superimposed and supplied to the load, arcing can be forcibly generated and welding work can be performed continuously.

As a result, when an arc occurs, the output does not flow during normal operation.
However, the waveform is defined by It-Ia+ls+It [where Ia is the arc current immediately before the short circuit, Is is the preset rising edge, and +1 is the change that increases approximately linearly over time]. In addition, in the event of an abnormality in which the next arc that should occur does not occur even if the output current is supplied to the load for a predetermined time during the above control, the output current supplied to the load is rapidly increased to prevent the arc from occurring. By forcing the generation, continuous short-circuit transfer arc welding with high reliability is always possible.

Furthermore, if a short-circuit current upper limit setting circuit is provided in the current control circuit, the output current supplied to the load is constantly monitored, so it is possible to prevent the output current from increasing indefinitely in the event of a short circuit, thereby reducing the occurrence of sparks. Another advantage is that arc welding can be performed continuously with suppressed arc welding.

Embodiments of the Invention Below, the attached drawings are shown below.
・Details will be explained along with the configuration of the device.

FIG. 1 shows the configuration of the apparatus of the present invention using a block diagram.

As shown in the figure, the device of the present invention is configured by combining a constant voltage control circuit that drives a switching control circuit IO to perform closed loop control of the output voltage and current supplied to the load, and a current control circuit. Constant voltage control is performed when an arc occurs, and current control is performed when a short circuit occurs.

In the figure, l indicates a consumable electrode (welding wire) that is fed at a predetermined speed by a control system (not shown), 2 indicates a base material which is a member to be welded, and 3 indicates a welding arc generated when an arc is generated.
4 is a current detector, 5 is a voltage detector, 6 is a voltage tIII'm circuit driven in constant voltage control mode, 7 is a current control circuit driven in current control mode, 8 is a smoothing circuit,
9 is a rectifier circuit, IO is a switching control in circuit provided to supply the necessary voltage to the load, 11 is a voltage detection; 12 = constant voltage control by arc detection signal and short circuit detection signal from 5 This is a switching means that alternately switches between current control and current control.

Here, the voltage control circuit 6 is driven when the voltage detector 5 detects the occurrence of an arc, and controls the switching control circuit 1O in a closed loop in order to maintain the generated arc 3 stably and heat and melt the consumable electrode 1. Then, during the arc generation period (72 to Tl), a constant output voltage V as shown in FIG. 3(a) is stably supplied to the load.

In addition, the current control circuit 7 is driven when the voltage detector 5 detects a short circuit, and when it is normal, the current control circuit 7 is operated to control the load as shown in Fig. 3 (b).
), but the output current is supplied to the load for a predetermined time [. Even if the current is supplied continuously, if the next arc that should occur does not occur, the current supplied to the load is rapidly increased to force an arc to occur, as shown by l in Figure 3 (C). is configured to do so.

In other words, the current supplied to the load during the short-circuit section (Tl to T2) is normally lt, that is, /1 mi in FIG. 3(b). l, sea urchin l: r' l-, -l + and one 1ζ
:of,.

+2 in case of an abnormality in which the arc that should occur does not occur.
In other words, it exhibits a waveform as shown in FIG. 3(C).

FIG. 2 is a more detailed block diagram of the block diagram in FIG. driver 10
2, the pulse width of the drive pulse can be adjusted by a pulse width control circuit 103.

Further, as the switching means 11, a switching circuit 11 provided after the pulse width control circuit 103 is adopted, and this switching circuit 11 is used for the above-mentioned voltage detection, ? When receiving the arc detection signal from S5, the control mode is selected as constant voltage control, and when receiving the short circuit detection signal, the control mode is switched from constant voltage control to current control.

A voltage control circuit 6 is provided after the switching circuit 11.
and the voltage control circuit 7 are connected, and the voltage control port B
6 is configured to include an error amplifier 61 and a voltage setting device 62 in the embodiment, and the error amplifier 61 compares the output signal from the voltage detector 5 and the output signal from the voltage setting device 62. The error output is sent to the pulse width control circuit 103 via the switching circuit II.

Here, the voltage setter 62 defines the MaI value in the constant voltage control mode, and when the constant voltage M control mode is executed, the output 111! A signal corresponding to the control value is sent to the I element 101, and feedback control is performed to supply a constant voltage to the load.

On the other hand, in the embodiment, the current control circuit 7 is configured as follows.

Ching circuit 70 and error amplifier 71. Current setter 72 and comparator 73. Furthermore, an additional X circuit 74. I/■ converter 75, time setter 76, integration circuit 77, sample hold circuit 78. The switching circuit 70 is configured by combining a rise position setting device 79, and a comparator 7.
The adder circuit 74 and the current setter 7
2 and comparator 7.
Inverted output from 3 (when No. 3 is output, add T; 11ul
n 74 is switched and connected to the T-wave setting device 72 .

Here, the error amplifier 71 uses the output from the adder circuit 74, which is output via the switching circuit 70, as a reference, and the
/V is compared with the output from the converter 75, and the output error between the two is amplified, and the error output is passed through the switching circuit 11 to a pulse width of 1748 times Ia IO3ci
Muhte, mN2J Short circuit section (Tl-
T2) Flow control is performed at 1 of the time. That is, in the normal state during the short-circuit section, the output tube 'fL1', which is defined by the applied output from the adder circuit 74 and has the unique waveform shown in FIG. 3(b), is supplied to the load.

However, on the other hand, the comparator 73 compares the output of the integrating circuit 77 and the output of the time setting device 76, and when the output of the time setting device 76 exceeds the output of the integrating circuit 77, it outputs an inverted output signal and activates the switching circuit 70. , the output from the adder circuit 74 is cut off, and the output from the current setter 72 is output to the error amplifier 71. In other words, this comparator 73 determines the 1 it time of flow of the output supplied to the load in the event of a short circuit by comparing the output j of the integrating circuit 77 with the output of the time setting 2S76 as a reference. When the output of the integrating circuit 77 exceeds the output of the time setting device 76, it is determined that the predetermined energization time t0 has elapsed, and an inverted output signal is sent to the switching circuit 1S70 to increase the current to the high level specified by the current setting device 72. will be supplied to the load.

FIG. 3(C) shows the current It supplied to the load in this case.
The waveform initially rises at 11, and after a current of this level is continuously supplied to the load for 0 hours, the current rises rapidly as shown by l. I can see that

On the other hand, the sample and hold circuit 78 samples the voltage signal corresponding to the output current Ia sent via the I/V converter 75, and samples the voltage signal every time it receives the short circuit detection signal from the voltage detector 5 described above. The signal held is held and outputted, and the rise amount setting r
G79 outputs the L pressure (No. 41) of the level determined according to the welding conditions in order to specify the rise of the output current 1 s as an arbitrary π, and the integrating circuit 77 outputs the L voltage (No. 41) when the output current rises by Is. Later, the gradient value tan δ of the captured variation 1 is defined.

Therefore, in this embodiment, when the current control mode is normal, the error amplifier 71 receives the output signal of the l/V converter 75 and the output of the adder circuit 74, that is, the sample and hold circuit 78, the rise i setting device 79, and the integration circuit 77. The added signal and the output signal from the l/V converter 75 are input manually, and these error signals are supplied to the switching circuit 11, and the output during the short circuit period is changed as shown in FIG. 3(b). controlled by a waveform.

However, if the current is 8 in the control mode,
The comparator 73 compares the output signal of the integration circuit 77 and the output signal of the time setter 76, and detects an abnormality in the control.

In other words, even if an output current is supplied to the load for a predetermined period of time, if the next 7 - error that should occur does not occur, an inverted output signal is sent from the comparator 73 to the switching circuit 70 and the output of the adder circuit 74 is cut off. , the error amplifier 71 sends the output of the current setting device 72 to the pulse width mm circuit 103 via the switching circuit 11, and the output current as shown in FIG. 3(C) is supplied to the load. ,As a result,
An arc will be forced to occur.

Although not shown in the figure, it is desirable to incorporate a circuit that defines an upper limit so that the short-circuit current does not increase indefinitely during normal operation in the current control mode.In this way, the output current 1t during a short-circuit can be infinitely increased. This means that the increase in the number of sparks can be prevented, and the generation of spacks during short circuit control can be effectively suppressed.

Next, the operation of the circuit and the method of the present invention will be explained with reference to the block diagram shown in FIG. 2 and the waveform diagram shown in FIG.

At the start of arc welding, appropriate pre-control is performed to facilitate the generation of the arc, and the consumable electrode 1 is fed at a constant speed to forcibly generate the arc 3.

When arc 3 occurs, an arc detection signal is sent from voltage detection 2S5 to switching circuit 11, and voltage control circuit 7
Is the pulse width 1111? Connected to B circuit 103. Therefore, the normal constant voltage control mode is selected for control.
The output voltage preset by the voltage setter 62 will be supplied to the load.

The waveform of the output voltage ■ at this time is shown in FIG. 3(a).

However, as the consumable electrode 1 continues to be fed, the gap distance between the consumable electrode 1 and the base material 2 gradually decreases, leading to an arc and a short circuit.

Then, the voltage detector 5 immediately detects the state and outputs a short circuit detection signal.

That is, in this state, the output voltage suddenly changes from several tens of volts to around zero volts, so in order to detect this state with the voltage detector 5, the voltage detector 5 must be connected to a comparator, for example, so that it can be compared with the reference voltage. It should be configured as follows.

In the embodiment shown in FIG. 2, the detection signal at this time is used to drive the switching circuit II, immediately cut off the voltage control circuit 6, and connect the current II control circuit 7 to the pulse width setting circuit 103. At the same time, a drive signal is sent to an integrating circuit 77 and a sample hold circuit 78 to enable closed-loop current control.

When the voltage detector 5 outputs a short circuit detection signal, the switching circuit 11 switches to the current control mode, the integrating circuit 77 is driven, and the sample and hold circuit 78 holds the sampled signal. As a result, when the current control mode is normal, the addition signals output from each of the integrating circuit 77, sample hold circuit 78, and rise position setter 79 are input to the error amplifier 72 as a reference signal for the control value. , the output current I sent from the current detector 4 via the I/V converter 75
a, the output current It (Fig. 3(b)
) will be output. When an abnormality occurs during such current control mode, the output supplied to the load is not energized for a predetermined period of time, but then... , :
If there is no problem with the residence, the third
Figure (c) shows 1. As shown in the figure, the output current ]t increases rapidly and an arc is forcibly generated.

As a result of these controls, when an arc occurs, the device goes into constant voltage control mode, and when a short circuit occurs, it goes into current control mode, and when normal, the output tml□ with the peculiar waveform shown in Figure 3 (b) is applied to the load. In addition, in the event of an abnormal situation where arc generation is incomplete, an output voltage tlL+z' with a waveform as shown in Fig. 3(c) will be supplied to the load, causing small droplets to form in a short period of time. This allows for reliable separation and efficient arc welding.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the schematic configuration of the device of the present invention;
FIG. 2 is a block diagram showing the 4JT position shown in FIG. 1 in more detail, and FIG. 3 is a waveform diagram of the output voltage and output current controlled by the method of the present invention. (Explanation of symbols) In the figure, l is a consumable electrode, 2 is a base material, 3 is an arc generated during welding, 4 is a current detector, 5 is a voltage detector, 10
is a switching control circuit.

Claims (3)

[Claims] (1) A short-circuit transition arc welding method in which short-circuiting and arc generation are alternately performed while feeding a consumable electrode at a constant speed,
When an arc occurs, constant voltage control is performed using a closed loop, and when a short circuit occurs, the current control is switched to a closed loop, and the output current I_2 is supplied to the load during the short circuit section.
The waveform of is defined as I_2=Ia+Is+It [where Ia is the arc current immediately before the short circuit, Is is the preset rising edge, and It is the variation that increases approximately linearly over time.] In devices that control waveforms, if the next arc that should occur does not occur even after the output current supplied to the load during the short-circuit section has been energized for a predetermined period of time, the output current is rapidly increased to generate an arc. A short-circuit transition arc welding method characterized by forcibly performing the following. (2) An arc welding device configured by combining a constant voltage control circuit and a current control circuit that drive a switching control circuit to control the output voltage and current supplied to the load in a closed loop, comprising: The constant voltage control circuit is driven by receiving an arc detection signal from a voltage detector that detects the load voltage when an arc occurs, and receives an output signal from the voltage detector to perform control set in advance in the switching control circuit. The current control circuit is configured to include a voltage control circuit that outputs a drive signal according to a value, and the current control circuit is driven in response to a short circuit detection signal from the voltage detector, and outputs an output from the current detector that detects the load current. It is equipped with a current control circuit that receives a signal and outputs a drive signal according to a control value set in advance to the switching control circuit, and this current control circuit is constructed by I_2=Ia+Is+It [where Ia is the arc current immediately before the short circuit. , Is is a preset rising edge,
It is a change that increases approximately linearly over time] is supplied to the load during the short-circuit period, and the output current I_2 having a predetermined waveform defined by Arc welding characterized in that, when the next arc to be generated does not occur even after being energized for a predetermined time, the output current is rapidly increased to force the generation of an arc. Device. (3) The arc welding apparatus according to claim 2, wherein the current control circuit includes a short circuit current upper limit setting device that limits the upper limit value of the output current to a preset value.