JPS63126672A - Device for conducting ac arc welding by consumable electrode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to arc welding, and more particularly to apparatus for performing alternating current arc welding with consumable electrodes.

The present invention can be utilized for power assisted manual arc welding of steels and their alloys using consumable electrodes.

It is known that during alternating current welding in the prior art electrode gap, short circuits are very likely to occur at the moment when the welding current passes through the zero point. This is because the electromagnetic force associated with the welding current ceases and affects the molten metal droplet of the electrode and the molten metal bath of the work piece being welded. The droplet therefore hangs along the axis of the electrode under gravity and the molten metal of the bath, which has already been forced out under the arc, approaches the droplet directly.

Such short circuits are due to interruptions in the welding process due to interruption of the supply energy from the welding transformer in this case (especially during welding with power assistance while mechanically feeding the wire electrode). ), such a short circuit lasts long enough that the unfused end face of the electrode sinks into the bath and touches its bottom. Immediately thereafter (when the maximum short circuit current value is reached)
, the electrode will burn out. This causes a significant amount of metal to be ejected from the bath and, in rare cases, interrupts the arc and interrupts the welding process.

Alternating current arc welding devices are known which are equipped with an arc stabilizer, which ensures that one discharge pulse of the switched capacitor passes through the electrode gap each time the welding current passes through the zero point ( Soviet inventor certificate Nα5
23769. 9100 on C1°B23, published in 1976). This pulse may prevent a short from occurring at that moment, but it may not be able to reignite the arc. Therefore, such a device stabilizes the arc of welding with non-consumable electrodes or manual welding with consumable electrodes when a short circuit in the electrode gap when the welding current passes through the zero point does not interrupt the welding process. It only stabilizes arc welding. Therefore, this device cannot be used to perform power assisted welding while mechanically feeding the electrode.

The most similar device to the present invention is a device that has an arc stabilization function and performs AC arc welding with a consumable electrode (USSR Inventor's Certificate Nα603521°C1, B23.9
106, published in 1978).

The device comprises a welding transformer with a secondary winding connected to an electrode gap, and a pulse generator having a power circuit connected in parallel with the electrode gap, the pulse generator comprising: a thyristor switch; It consists of a series circuit comprising a power supply winding and a switched capacitor, further comprising a control unit of a thyristor switch, which unit has a zero detector connected in parallel to the electrode gap and a control pulse former. have.

When the welding current passes through the zero point (with each change of polarity in the electrode gap), the zero detector responds to this change by generating a signal that is sent to the control pulse former, which causes the thyristor of the switch to one of them is ignited. The switched capacitor is therefore pulse charged through the electrode gap and the switched thyristor described above is blocked. During the next half of the welding current, when the polarity of the electrode gap changes again, the zero detector generates a signal that is sent to the control pulse former, which fires the second thyristor of the switch. . The switched capacitor is pulse charged through the electrode gap.

Therefore, one pulse passes through the electrode gap each time the welding current passes through the zero point.

In the case of power-assisted welding with consumable electrodes, this pulse can break the liquid metal bridge between the electrode and the workpiece that forms in the event of a short circuit, but cannot re-ignite the arc. I can't.

The arc is re-ignited after the voltage in the secondary winding of the welding transformer reaches the required voltage.

PROBLEM SOLVED BY THE INVENTION The present invention stabilizes the burning of the arc in a circuit by forming two pulses through the electrode gap to destroy the bridging formation in the event of a short circuit and ensure restriking of the arc. The present invention aims to provide an AC arc welding device using a consumable electrode that can be used in various ways.

Means for Solving the Problems According to the invention, a pulse generator is provided, comprising a welding transformer, the secondary winding of which is connected to an electrode gap, and having a power circuit connected in parallel to this electrode gap. Furthermore, it is equipped with
The generator consists of a series circuit including a thyristor switch, a power supply winding and a switched capacitor;
a control unit for controlling the thyristor switch, the unit having a zero detector and a control pulse former connected in parallel to the electrode gap, the input of which is connected to the output of the zero detector; and an auxiliary pulse generator having a power circuit connected in parallel to said electrode gap in an apparatus for performing alternating current arc welding with a consumable electrode whose output is configured to be connected to the control input of a thyristor switch. Further comprising, the auxiliary pulse generator is comprised of a series circuit including a thyristor switch, a power supply winding, and a switched capacitor.

and further comprising a control unit for controlling the thyristor switch, the unit having a zero detector connected in parallel to the switched capacitor of the main pulse generator, and a control pulse former, the input of which is connected to the output of the zero detector, and the output thereof is connected to the control input of the thyristor switch.

The present invention allows alternating current welding to be carried out in such a way that the burning of the arc is stabilized so as to ensure a high quality of the welded joint.

Embodiment According to the invention, a device for performing alternating current arc welding with consumable electrodes comprises a welding transformer 1 (FIG. 1) in which a secondary winding 2 is connected to an electrode gap 3, and two pulse generators. Equipped with: The first pulse generator comprises a power circuit connected in parallel to the electrode gap 3, which circuit comprises a series circuit consisting of a thyristor switch 4° power supply winding 5 and a switched capacitor 6. The thyristor switch 4 is a thyristor 7 connected to a control pulse former 9.
and 8. Furthermore, the first pulse generator comprises a unit for controlling the thyristor switch 4, which unit comprises a zero detector 1o connected in parallel to the electrode gap 3 and a control whose input is connected to the zero detector. A pulse former 9 is provided.

The second pulse generator consists of a power circuit connected in parallel to the electrode gap 3, which circuit is connected in parallel to the electrode gap 3.

Thyristor switch 11. It consists of a series circuit including a power supply winding 12 and a switched capacitor 13. The thyristor switch 11 is formed by thyristors 14 and 15 connected to a control pulse former 16 . Furthermore, the second pulse generator comprises a unit for controlling the thyristor switch 11, which unit has a zero detector 17 connected in parallel to the switched capacitor 6 and an input connected to this zero detector. It is composed of a control pulse former 16.

The zero detector 10 of the first pulse generator consists of a current transformer 18 (FIG. 2) connected to the winding 2 of the welding transformer, and an ohmic split consisting of resistors 19.2o and 21.22 connected in series. and transistors 23, 24 whose bases are connected to the ohmic divider. Furthermore, in this zero detector, a capacitor 25 is connected in series with the primary winding 26 of the transformer 27 and the emitter of the transistor 23, and a capacitor 28 is connected in series with the primary winding 29 of the transformer 30 and the emitter of the transistor 24. connected to.

Shunt rectifier 31 is connected in parallel to winding 26 and shunt rectifier 32 is connected in parallel to winding 29.

One lead of the bias resistor 33 is connected to the transistor 23
and 24, the other lead of the resistor is connected to the positive terminal of power supply unit 34, and its negative terminal is connected to the leads of capacitors 25 and 28.

The pulse former 9 of the first pulse generator includes a thyristor 8
The secondary winding 35 of the transformer 27 connected to the switch 4
A secondary winding 36 of a transformer 30 connected to a thyristor 7 of
It consists of

The zero detector 17 (FIG. 1) of the second pulse generator is connected to the resistor 37. - of capacitor 38 and transformer 40 (FIG. 2)
It consists of a series circuit including a secondary winding 39 and is connected in parallel to the switched capacitor 6 of the first pulse generator.

The control pulse former 16 (FIG. 1) consists of a winding 41 (FIG. 2) of the transformer 4° connected to the thyristor 15 of the switch 11 and a winding 42 connected to the thyristor 14 of the switch 11. configured.

FIG. 3 is a graph showing changes over time in welding current and voltage U, and shows peak values of current and voltage stabilizing pulses in values 1 and I2. Ul and U2 are shown respectively.

The device of the invention functions as follows.

Depending on the polarity of the voltage across the electrode gap 3 (FIG. 2), the current transformer 18, operating under saturation conditions, forms a pulse signal that causes the transistors 23 and 24 to conduct alternately.

Consider the case when the electrode is at a positive potential and the workpiece to be welded is at a negative potential (at the moment the device is switched on). Transistor 23 conducts and capacitor 25, previously charged by power supply 34, connects transformer 27.
through the primary winding 26, the capacitor 25, the emitter/collector junction of the transistor 23, the secondary winding 26. It is discharged through a circuit consisting of capacitor 25. Transformer 27
A pulse is generated in the secondary winding 35 of the magnetic dispersion transformer 1 to fire the thyristor 8, which causes the capacitor 6 to charge when the device is turned on and to charge the magnetic dispersion transformer 1 during the primary cycle.
through the electrode gap from the power supply winding 5 of the
Destroying bridge formation during short circuit.

The parameters of the power supply winding 5 and capacitor 6 are selected to give a recharge pulse magnitude in the range of 200 to 500A.

At the next moment, when the polarity of the electrode gap 3 changes (positive change at the workpiece and negative change at the electrode), the transistor 24 becomes conductive and the capacitor 28, which has been previously charged from the power source 34, Emitter/collector junction of transistor 24, primary winding 29 of transformer 30
discharge through. The firing pulse of the thyristor 7 is formed in the secondary winding 36 of the transformer 30. Thyristor 7 fires, causing capacitor 6 to recharge through electrode gap 3.

The zero detector 17 (FIG. 1), which includes the primary winding 39 (FIG. 2) of the transformer 40 of the second pulse generator, is connected in parallel with the capacitor 6 whose voltage is strictly square. Therefore, during recharging of capacitor 6, thyristor 1 of switch 11
Pulses firing alternately 4 and 15 are formed in the secondary windings 41 and 42 of the transformer 40.

The capacitor 13 recharges from the power supply winding 12 of the transformer 1 through the electrode gap 3 to ensure restriking of the arc.

The parameters of the power supply winding 12 and capacitor 13 are:
The pulses are chosen to have voltage amplitude values of 200 to 100 OV.

The device according to the invention thus allows two pulses to be passed through the electrode gap 3 when the welding current passes through the zero point. The first pulse with a current amplitude value of 200 to 50'OA destroys the molten metal bridge formed during the short circuit,
A second pulse with a voltage amplitude of 200 to 100 OV reignites the arc.

Therefore, stability of arc combustion and high quality of welding are ensured.

[Brief explanation of the drawing]

1 is a block diagram of an apparatus according to the invention for performing AC arc welding with a consumable electrode; FIG. 2 is a diagram showing an embodiment of the apparatus according to the invention; and FIG. 3 is a block diagram of an apparatus according to the invention. It is a time course diagram explaining the operation. 1... Welding transformer 2... Secondary winding of the welding transformer 3... Electrode gap 4... Thyristor switch 5 of the first pulse generator...
- Power supply winding 6 of the first pulse generator...Switched capacitor 7.8 of the first pulse generator...Thyristor 9...Control pulse former 10.17...Zero detector 11...No. 2 pulse generator thyristor switch 12.
- Power supply winding 13 of the second pulse generator...Switch capacitor 14, 15 of the second pulse generator...Thyristor 16...Control pulse former 18...Current transformers 19 to 22 of the zero detector... Ohmic divider resistance 23.24...
Zero detector transistor 25.28...Zero detector capacitor 26.29...Transformer primary winding 27.3o...Transformer 31.32...Zero detector shunt resistance 33...Zero detection Bias resistance of the transformer 34...Power source 35, 36...Secondary winding of the transformer 37...Resistance of the zero detector 38...Capacitor of the zero detector 39...Primary winding of the transformer 40...Transformer 41.42... Secondary winding of transformer ■... Welding current U... Voltage

Claims (1)

[Claims] comprising a welding transformer (1), the secondary winding (2) of which is connected to an electrode gap (3), and further comprising a pulse generator having a power circuit connected in parallel to this electrode gap (3). The generator is composed of a series circuit including a thyristor switch (4), a power supply winding (5) and a switched capacitor (6), and further includes the thyristor switch (
4), the unit includes a control unit that controls:
It has a zero detector (10) and a control pulse former (9) connected in parallel to said electrode gap (3), the input of which is connected to the output of the zero detector (10) and the output of which is In an apparatus for performing alternating current arc welding with a consumable electrode configured to be connected to the control input of a thyristor switch (4), an auxiliary pulse generator having a power circuit connected in parallel to said electrode gap (3); further comprising a thyristor switch (11), said auxiliary pulse generator consisting of a series circuit comprising a thyristor switch (11), a power supply winding (12) and a switching capacitor (13); ), said unit comprising a zero detector (17) connected in parallel to the switched capacitor (6) of said main pulse generator and a control pulse former (16). An alternating current arc welding device, characterized in that its input is connected to the output of said zero detector (17), and its output is connected to the control input of said thyristor switch (11).