SU1738524A1 - Apparatus for electric arc welding with forced short circuiting - Google Patents

Abstract

Use: to the field of electric arc welding with a fusible electrode in a protective gas environment, mainly in a carbon dioxide environment. SUMMARY OF THE INVENTION: A forced short circuit electric arc welding device comprises a source of welding voltage and a power regulator with a control circuit. The welding voltage source is made with voltage modulation, which makes it possible to obtain a near-optimal algorithm for welding current modulation with small losses in the power regulator and a simpler control circuit. 4 il. yo

Description

The invention relates to electric arc welding with a fusion electrode in a protective gas environment, preferably in a carbon dioxide environment.

One of the main disadvantages of carbon dioxide welding is metal spraying.

There is a known method of arc welding with a melting electrode, in which a short circuit is forced by periodically lowering the voltage of the power source at a predetermined frequency.

When the voltage drops, the molten metal droplets tend to occupy a position coaxial with the electrode, which provides favorable conditions for the development of the contact of the droplet and the weld pool.

This method only partially solves the problem of reducing the splashing of metal, because it does not provide a reduction in

blast jumper energy, in addition, the work on a rigid program causes a high sensitivity to various kinds of disturbances and requires a long adjustment to the desired mode.

Closest to the present invention is a device consisting of a DC power source, a transistor regulator connected in a welding circuit in series with an arc, a current control sensor, a arc voltage control device and a control circuit.

This device implements an optimal algorithm for modulating the welding current, which makes it possible to reduce the loss of metal by spraying several times as compared to the power supply of the arc from a common welding voltage source.

The disadvantage of this device is the complexity of the transistor controller,

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which is due to the need for a high switching speed of the welding current, as well as the relatively high heat losses at the transistor regulator.

The aim of the invention is to simplify the device and reduce the splashing of the metal during welding.

The goal is achieved by the fact that the welding voltage source is made with voltage modulation, and the power regulator is connected to the outputs of the welding voltage source.

The combined use of a modulated voltage welding source and a power regulator connected to the outputs of the welding source (parallel to the arc) is a significant difference between the invention and the known one.

The combined use of a modulated voltage source and a power regulator connected to the outputs of the welding voltage source allows one to obtain a near-optimal algorithm for modulating the welding current with small losses in the power regulator and a simpler control circuit.

This effect is due to the fact that the welding current passes through the power regulator for a much shorter time than through the power regulator connected in series with the arc, and also because the power regulator acts on the welding process mainly only at the jumper break stage, and Favorable conditions for the development of metal drop contact and weld pool are provided by modulating the voltage of the power supply.

FIG. 1 shows a diagram of the device; in fig. 2 is a diagram of a power regulator and an embodiment of a modulated voltage source; in fig. 3 shows an embodiment of the control circuit; in fig. 4 - time diagrams.

The device consists of a modulated voltage source 1, a power regulator 2, a control circuit 3. The device is connected to the welding electrode 4 and product 5. In the proposed device, the power regulator 2 is connected to the output of the source of modulated welding voltage, the control circuit 3 is connected to the source 1 of the modulated voltage and to the power regulator 2.

Power regulator 2 (Fig. 2) consists of a symmetrically thyristor switch VD1 and VD2 and a capacitor C1 connected in series with it. Thyristor key consists of two included anti-parallel thyristors VD1 and VD2. A symmetric thyristor switch is used to charge and discharge capacitor C1.

The modulated voltage source is made on the basis of a standard controlled welding rectifier of the type VDU-506, in which the following changes are made in the circuit: the VS3 thyristor electrode is disconnected from the welding control circuit

0 rectifier and connected to the circuit to control the proposed device;

The VS4 thyristor electrode is disconnected from the control circuit of the welding rectifier and connected to the cathode, while the thyristor

5 VS4 is permanently closed.

The control circuit (Fig. 3) consists of voltage comparators 6 and 14, the inputs of which are connected to the welding voltage, the output of the comparator 6 is connected to

0 elements 7 and 11 of the time delays, the outputs of which are connected respectively to the driver 8 and 12 pulses, the outputs of the drivers 8 and 12 pulses are connected to the elements 9 and 13 galvanic

5, the output of the comparator 14 is connected to the pulse shaper 15 on a leading edge, the output of which is connected to the galvanically isolated element 16; the minus of the power supply unit 10 is connected to the minus of the welding voltage, and the power supply unit 10 is connected via the diode V1 to the plus of the welding voltage.

Device for electric arc welding with forced short circuits

5 works as follows.

After the arc is ignited after several welding microcycles, the device operates in an operating mode, which is characterized by a relatively stable duration of the welding micro cycles.

For the beginning of the microcycle, conditionally accepted time is to (Fig. 4). At this time, the voltage on the arc begins to decrease as the VS 4 thyristor in power supply 1

5 is closed, the capacitor C1 in the power regulator 2 is charged at this time point before the voltage UCB.

At time ti, the arc extinguishes, the voltage across the arc gap becomes

0 equal to Uo, this voltage is supplied to power supply unit 10. After the arc extinguishes, the distance between the electrode moving at a constant speed and the welding bath quickly decreases and by the time t2

5 a short circuit occurs. The voltage across the arc gap becomes less than Ui, and a comparator 6 is triggered, the output of which is connected to the elements 7 and 11 of the time delays. Through time ri after the operation of the comparator

6, a pulse arrives at the control electrode of the thyristor VD1, the thyristor opens (time ts) and through it the short-circuited arc gap discharges capacitor C1. With a delay τ relative to the time t2, the impulse generated by shaper 7 is applied to the control electrode of the thyristor VS3. The thyristor VS3 opens and the current through the jumper between electrode 4 and product 5 begins to increase. The voltage across the jumper wire increases, due to both an increase in current and an increase in jumper resistance.

When the voltage on the jumper reaches the value Ua (time t2), the comparator 14 is triggered, the shaper 15 forms a pulse on the leading edge, which through the galvanic isolation 16 enters the thyristor electrode VD2.

Through the opened thyristor VD2, most of the current from the welding source goes to the charge of capacitor C1. The current through the jumper is sharply reduced and its rupture occurs with a small current, which is one of the main conditions for reducing splash formation. After the jumper is destroyed, the arc is ignited, the capacitor C1 is charged through the thyristor VD2 to the voltage UCB, the thyristor VD2 closes. The operation of the device in this welding microcycle is completed on this; in the following microcycles, the operation of the device proceeds as described.

In the proposed device, each of the constituent elements of the device (molded power source, power regulator, control circuit) can be made in several versions, depending on operating conditions and operating modes.

The modulated power supply can be made on the basis of thyristor

welding rectifiers (type VDU-601, VDU-506), in which the modulation of the drive voltage is produced,

The power regulator can be made in the form of a transistor switch.

The control circuit variant depends on the type of power controller used and the type of modulated power supply used.

The proposed apparatus can be used in welding with reverse polarity on the arc, as well as in welding in the direct polarity.

The proposed device, in comparison with the known one, provides a reduction in metal spatter during welding and has a simpler power regulator with less heat losses and a simpler control circuit. The known devices for reducing metal spraying have not yet received widespread use in industry due to the complexity of power controllers and control circuits. The use of the proposed device allows wider use due to the simplicity of the power controller and control circuit.

Claims (1)

Claims An apparatus for forced-arc electric arc welding, comprising a welding voltage source, a power regulator connected to a control circuit, the inputs of which are connected to the outputs of the welding voltage source, characterized in that, in order to simplify the design of the device and reduce splashing metal during welding, the welding voltage source is made with voltage modulation, and the power regulator is connected to the outputs of the welding voltage source. ® "/ Rig. 2 + UcB