SU948572A1 - Plasma welding method - Google Patents

Description

This invention relates to the field of plasma and microplasma welding. . Currently, processes where welding is carried out with opposite polarity pulses of welding current are of great use.

A known method of plasma welding with bipolar pulses is that two electrically isolated non-melting electrodes 11 are placed in front of the plasma torch nozzle. Current pulses of direct polarity are supplied to the first electrode, and reverse polarity is supplied to the second electrode. In this case, the arc compression occurs both with direct polarity current pulses and reverse.

The disadvantage of this method is the presence of two electrodes, which complicates both the design of the plasma torch and the electrical circuit of the source.

Also known is the method of plasma welding using a duty arc for the ionization of the arc gap, burning between the nozzle and the electrode of the plasma torch C2. Current polarity pulses are applied to the gap, the electrode — the product, and the floating current — to the gap, the nozzle — is the helium. Thus, the reverse-polarity arc is not compressed by the plasma-forming gas and the current density in it is much lower than with direct polarity, because of the relatively large nozzle sizes, it is difficult to eliminate reverse-polarity wandering arcs, which leads to the expansion of the heat-affected zone deterioration of strength related to it

10 welded joint characteristics.

The aim of the invention is to obtain a crimped arc with direct and reverse polarity.

The goal is achieved by the fact that, in plasma plasma welding, radio-controlled pulses, in which the arc burn is between the electrode and the nozzle, change the polarity of the pilot arc, and the polarity of the pilot arc corresponds to the polarity of the subsequent pulse of the main arc.

The method is carried out in the following manner.

When applied to the electrode pulse

25, a negative voltage relative to the product, the arc is on, a positive, relative to the electrode, voltage is applied to the nozzle. When a positive pulse is applied to the electrode 30,

with respect to the product (in the case, if the arc is on fire, as well as when a voltage pulse arrives at the electrode, negative with respect to the product), the potential of the nozzle will be more positive than the potential of the electrode, and the main arc will be excited by the nozzle and product, but not between electrode and product.

In order for the main arc, when a voltage pulse, positive relative to the product, is applied to the electrode, be excited between the electrode and the product, it is necessary that the arc be burned under the action of a positive voltage on the electrode relative to the nozzle. . The drawing shows a diagram of an apparatus for carrying out a plasma welding method with different polarity pulses,

The device consists of an alternating current source (network); transformer 2 with increased dissipation, having two secondary windings; phase shifters 3 and 4; AC regulators 5 and 6, each of which consists of two oppositely connected thyristors; devices 7 and 8 of ignition of the arc of sequential action; plasma torch 9. Position 10 in the drawing indicates the product to be welded.

The device works as follows.

The mains voltage from the source of foam current 1 is fed to the primary winding of the transformer 2, is fed to the input of the phase shifter 3 and also through the AC regulator 5 and the arc ignition device 7 to the gap of the plasma torch nozzle 9. The output pulses of the phase shifter 3 are fed to the control The thyristors of the thyristors of the AC regulator 5 and the input of the device 7 for igniting the arc are shifted from the beginning of the half-wave voltage of the first secondary winding of the transformer 2 by the time chosen from the condition stable ignition and combustion of the pilot arc between the electrode and the nozzle .plazmotrona 9. The voltage across the second secondary winding of the transformer 2 is input

phase shifting device 4, as well as through an ac regulator and an arc ignition device 8 to the gap of the plasma torch 9 is a product 10. The output pulses of the phase shifter 4 are supplied to the control electrodes of the thyristors of the ac regulator and to the arc ignition device 8 / shifted relative to the beginning of the half-wave of the voltage of the second secondary winding of the transformer 2 for a time ensuring stable burning of the main arc between the plasma torch 9 and the product 10. This time shift should provide Heal the ignition of the main arc after the ignition of the pilot arc, as well as the specified ratio of the currents of the main arc of direct and reverse polarity. The secondary windings of transformer 2 are phased in such a way that, with a positive voltage across the electrode relative to the nozzle on the product, the voltage is negative relative to the electrode.

Approximate economic effect when applying the proposed method in the automotive and electrical industry will be about 2.5 million rubles. per year compared to the prototype.

Claims (1)

1. The method of microplasma welding The second interdepartmental meeting on microplasma welding. Kiev-Ufa 1973, p.6. 2 USSR author's certificate number 221477, cl. At 23 K 9/16, 17.06.67 (prototype). / / / / L f