JPH01178368A - Welding arc starting device - Google Patents

Abstract

PURPOSE:To reduce burning up of a wire by providing a first means to control to a stored suppressed current value and a second means to select optimum values of a voltage level, an impressed time and a suppressed current value and to execute starting control. CONSTITUTION:A welding current waveform control circuit 10 receives a signal from a detection circuit 9 and controls a current waveform at the time of short- circuiting and arcing. A welding stop time counter 16 receives the output from a torch switch circuit 15 and counts the time until a torch switch signal is again turned on after being turned off. The welding wire end being in a red-hot state or in a cooled state is judged by the arc stop time and the counter 16 outputs it to the welding current waveform control circuit 10. The waveform control circuit 10 receives signals from the detection circuit 9 and the welding stop time counter 16 to execute the current waveform control at the time of short-circuiting and arcing at the time of starting a welding arc. The output of the waveform control circuit 10 is inputted to a pulse width modulation circuit and the welding output is controlled through a driver 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to shielding a welding area with a shielding gas mainly composed of CO□ gas, etc., and continuously connecting a consumable electrode wire (hereinafter simply referred to as a welding wire) to the welding area. The present invention relates to a welding arc starting device that performs fusion welding by feeding the welding arc.

Conventional Technology As a power source for consumable electrode arc welding, a power source with constant voltage characteristics is usually used, and a control element such as a transistor is used for output control.

In a power supply with such an output control method, the short circuit characteristics or arc characteristics are adjusted by waveform control to obtain good welding characteristics by detecting whether a short circuit or an arc occurs, and the welding operation is performed by adjusting the short circuit characteristics or arc characteristics by controlling the waveform. I am trying to improve my sexuality. This method uses a waveform control method to control the transient characteristics of the power supply itself, and is widely used. Waveform control is particularly effective during steady welding, where short circuits and arcs occur repeatedly at certain intervals.

However, when starting the welding arc, the basic characteristics for obtaining good welding arc starting characteristics have not been elucidated.
At present, no improvement has been made by waveform control at the time of starting the welding arc.

An example of the configuration of this type of control power source that performs waveform control on a steady arc and a control method when starting a welding arc will be described with reference to the drawings. In Fig. 5, 1 is a rectifier,
The three-phase input is full-wave rectified by rectifier 1, passed through choke coil L, smoothed by capacitor CI, and -
Converts to direct current. The DC power is transferred to transistor Q,
~Q4 converts into high frequency alternating current.

This situation will be explained using FIG. 6. At a certain time t1, transistors Q, Q2 are turned on, and the primary winding MTr of the main transformer MTr is turned on.

A primary current i flows. Next time 1. , transistors Q, ~Q are all 0FFL, and no current flows through MTr (this time is called dead time). At the next time t3, transistor Q.

and Q4 is ON L/ % M T r + minus i
Current flows in the direction. At t4, it becomes dead time again.

The high frequency output obtained by switching the transistors is stepped down by the main transformer MTr.

The output of the main transformer MTr is connected to the diode D2. D.

It is rectified by and becomes the welding output through reactor L2.

This type of control method is generally called inverter control, and one period T is the 1st and -14th cycle of transistor switching, and is divided into (repeat DC → AC →
We are doing a direct current exchange. There are many ways to control the welding output in an inverter-controlled welding power source, but pulse 11 modulation is one of them, in which the switching frequency is kept constant and the transistor is turned on during one period (T,). Changing the time ratio, i.e. 1. +13
The output is adjusted by changing /T.

FIG. 7 shows voltage waveforms at various parts on the output side. Figure a is an output characteristic diagram of the main transformer MTr, and figure a is a diagram of the output characteristics of the main transformer MTr.
D is an output characteristic diagram, and C in the same figure shows a welding output characteristic diagram that has been smoothed by the reactor 2 and includes some jaggedness, but has few ripples. Next, an il control circuit for controlling the conduction states of transistors Q1 to Q4 will be explained with reference to FIG.

Reference numeral 2 denotes a remote control for instructing welding output, and its output instruction value is input to a voltage command circuit 5. Reference numeral 3 denotes a remote controller for instructing the welding current, the output of which is connected to a consumable electrode wire feed instruction circuit 4, which drives the wire feed motor in accordance with the welding current value.

The output of the voltage command circuit 5 is added to or subtracted from the output of the output voltage detection circuit 6, which is a feedback signal, and becomes an input signal of the pulse width modulation circuit 7. This input signal is an output voltage setting signal that determines the final welding output, and the pulse width modulation circuit 7 is a circuit that modulates this output voltage setting signal to a pulse width that corresponds to the magnitude of the signal. The output of this pulse width modulation circuit becomes the input signal of the driver circuit 8. Driver 8 is a base current supply circuit for driving power transistors Q, -Q4. It is also a circuit for applying a reverse bias (applying a negative voltage to the base) when turning off the power transistors Q1 to Q4. driver 8
amplifies the output signal of the pulse width modulation circuit and converts it into an output that can drive the power transistors Q1 to Q4, and according to the pulse width of the output pulse of the pulse width modulation circuit,
Power transistor Q, -04 is made conductive.

The power transistor is set to 0N- by the output of driver 8.
OFF (returns to oscillation, becomes an input to the main transformer MTr, and as described above, a welding output is obtained from the secondary side of the main transformer MTr.

Next, in this transistor inverter power supply, a conventionally used control method at the time of starting an arc will be explained.

In FIG. 8, a is a torch switch signal, and the torch switch is turned on at a time of 1 s. Also, the figure shows the welding wire feed speed signal, and the torch switch O
At the same time as N, the welding wire is fed at a low down speed n8 lower than that during steady operation. At time t0 when the welding wire moves toward the base machine, contacts the base machine, welding current flows, and current detection is performed, the welding wire feeding speed becomes the feeding speed during steady welding. C in the same figure shows the output voltage of the welding machine. When the torch switch is turned on, the no-load voltage vN is output, and at the current detection time point t0 phase, the hot voltage VH is applied, and after the hot time period of 1H, the steady output V, becomes.

Based on the conventionally used sequence when starting the welding arc shown in FIG. 8, the situation when starting the welding arc will be explained with reference to FIG. 22 indicates a welding base machine.
The welding wire 21 is slowed down to the base machine direction n,
g, and shows the moment of contact with the mother machine 22.

As is clear from FIG. 8, at this point, a hot voltage V□ is being applied between the welding wire 21 and the base machine 22, so that the welding wire melts as shown in the figure. At the same time, the welding arc 23 is generated, and since this hot voltage vH is considerably higher than the output voltage during normal welding, the welding wire burns up greatly, causing the welding arc to break as shown in Figure C (: may occur.In cases where the welding arc is started continuously,
If the tip of the welding wire is red-hot when starting the welding arc after the first welding arc, the welding wire will flare up as described above, and arc breakage will easily occur (and in extreme cases, the welding wire may It may become fused to the tip, which is the current-carrying part of the welding wire.

Problems to be Solved by the Invention As described above, in the conventional welding method, if welding arc breakage occurs when the welding arc is started, the bead shape at the welding start portion tends to become a defective bead. Particularly when high-speed welding is performed, bead discontinuity becomes noticeable when starting the welding arc, which is a problem.

Further, the amount of spatter generated increases, which is not preferable.

Furthermore, if the welding wire is fused to the tip, the tip must be replaced, resulting in problems such as a decrease in the operating rate of the line.

Means for Solving the Problems The present invention provides a welding arc starting device that applies a hot voltage higher than the output voltage during steady welding when starting the welding arc of a welding arc device using a consumable electrode. A first means performs welding current waveform control on the welding current when a voltage is applied, and controls the welding arc suppression current value to a welding arc suppression current value stored in a welding condition data bank; A second means is provided for controlling the welding arc starting by selecting the voltage level of the voltage, the hot voltage application time, and the optimum value of the welding arc suppression current value.

Effect: By the above means, even if the end of the welding wire is in a red-hot state, the welding wire is less likely to flare up when the welding arc is started.

EXAMPLE An example of the present invention will be described below with reference to the drawings. Components having the same functions as those of the conventional example are given the same numbers and their explanations will be omitted.

In FIG. 1, 9 is a circuit for detecting a short circuit or an arc state, and is a circuit for detecting whether the welding state is an arc generation state or a short circuit state. 10 is a welding current waveform control circuit that receives the signal from the detection circuit 9 and controls the current waveform during short circuit and arcing. 15 is a torch switch circuit, the output of which is a welding stop time counter 16
is input. The welding stop time counter 16 counts the time from when the torch switch signal turns OFF until it turns ON again (hereinafter simply referred to as arc stop time). When the arc stop time is short, the welding wire end is in a red-hot state. Therefore, when the arc stop time is long, the welding wire end is in a cooled state.

The output of the welding stop time counter 16 is outputted to the welding current waveform control circuit 10 by determining whether the welding wire end is in a red-hot state or a cooling state based on the arc stop time. The waveform control circuit 10 receives signals from the detection circuit 9 and the welding stop time counter 16, and controls the current waveform during short circuit and arcing when starting the welding arc. The output of the waveform control circuit 10 is input to a pulse width modulation circuit, and the welding output is controlled through the driver 8.

Next, the operation will be explained using FIGS. 2 and 3.

Fig. 2 is a timing casing diagram when the tip of the welding wire is in a normal cold state, and Fig. 3 is a timing sequence diagram when the tip of the welding wire is red-hot. It is the same as that in Fig. 8, where a is the torch switch signal, b is the wire feed speed signal, and C is the hot voltage value and output timing, and the hot voltage is the short circuit signal that is opened and a stable arc is obtained. A sufficient time period (hora time period tH) is selected and applied.

d is a welding current waveform, and the welding current is controlled to a welding arc suppression current 'AP that is low enough to maintain a stable welding arc after the short circuit is opened and an arc is generated when the welding arc is started. Welding wire slowdown speed n 1 Hot voltage level V) 11 Hot voltage output time tH1 and welding arc suppression current value ■Appropriate values for AP vary depending on the heating condition of the welding wire tip, and the optimal value is selected in each case. It is configured so that As a result, a large flare-up of the welding wire does not occur when the welding arc is started, and in the case of Fig. 2, where the end of the arc welding wire is in a cooled state, the wire slowdown speed nal allows the welding arc to be started smoothly. However, in the case of Figure 3, where the wire end is in a red-hot state, if the slowdown speed is low, the flare-up will increase, and the wire feed speed during steady welding will increase. The slowdown speed n has a value close to
ET has less flare-up. Regarding hot voltage and application time, if the wire end is in the cooling state, a high value of hot power is required to obtain good welding arc starting characteristics,
That is, a high value of hot pressure yHI and a sufficiently long hot time period tH1 are required.

When the wire end is in a red-hot state, a lower level of hot voltage V 1 and a shorter time period tH2 will cause less burning of the welding wire, and better arc starting characteristics can be obtained.

In addition, in order to reduce the burnout of the wire when a short circuit opens and an arc occurs when the welding arc is started, the welding arc suppression current value IAP2 is set when the wire end is red-hot, and when the wire end is cooled. ■Selected as a value closer to 4.1. As described above, by selecting the optimum control conditions at the time of starting the welding arc depending on the heating state of the welding wire end, a large flare-up of the welding arc does not occur, and tip fusion of the welding wire does not occur. e is a signal to obtain the timing for controlling the welding arc current to the suppression current value IAP, and is a signal indicating whether the welding output state is short circuit state S or arc occurrence state tllA, which is determined from the welding voltage waveform. You can get it.

FIG. 4 shows an example of the structure of a data bank in which slowdown speed n, % hot voltage vH1 hot time tH1 welding arc suppression current value ■AP are stored.

Due to the heating state of the wire tip, when the wire end is in the cooling state, the slowdown speed nel' hot voltage v 1
The hot time t) 11 and the welding arc suppression current current value 4, 1 are selected and read into the CPU (not shown) and controlled.

When the wire end is heated, the slowdown speed n0
2. Hot voltage vH2' hot time tH2! Welding arc suppression current value IAP2 is selected and similarly read into the CPU and controlled.

Effects of the invention As is clear from the above explanation, when welding arc starts,
Even if the end of the welding wire is red-hot, the welding wire will be less likely to flare up, resulting in no welding arc breakage, less spatter, and problems such as welding wire tip fusion. The appearance of the bead also improves.

In addition, there is no discontinuity in the bead at the welding arc start part (a good bead appearance can be obtained).

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a welding arc starting device according to an embodiment of the present invention, Figs. 2 and 3 are output characteristic diagrams of the device, Fig. 4 is a data table configuration diagram of the device, and Fig. 5 is a configuration diagram of the welding arc starting device according to an embodiment of the present invention. FIG. 6, FIG. 7, and FIG. 8 are diagrams showing the output characteristics of the conventional device, and FIG. 9 is an explanatory diagram showing the state of arc generation by the device. 9... Short circuit arc detection circuit, 10...
Waveform control circuit, 15...Torch switch circuit,
16...Welding stop time counter. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1: 9--One-wing bribe A, the number of people who circulate in Kude (+o----Saka wo Shishou circuit TE--y-÷Switch + Circulation number) Figure 2 Figure 3 Area, Moi () -7 5th WJ / Figure 6 Figure -7 Figure 8 Figure 9

Claims (1)

[Claims] When starting the welding arc of a welding arc device using a consumable electrode, a hot voltage higher than the output voltage during steady welding is applied. and a first means for controlling the welding arc suppression value to a welding arc suppression value stored in a welding condition data bank; A welding arc starting device comprising a second means for selecting an optimum current value and controlling welding arc starting.