Improving the technology of deposition using strip electrode

Abstract

The behavior of the arc at the strip electrode tip is studied. It is shown that the arc is moving along the electrode tip due to periodic short-circuits of the arc gap. Thus, a new arc is excited at the point where short circuit occurred after a conductive bridge formed by molten metal is vanished due to a high welding current. This leads to an increase in the probability of defect formation in the deposited layer of workpiece under treatment. To improve deposited layer quality, it is suggested to identify the moments of short-circuits of the electrode to the base metal and to discharge the pre-charged capacitorat these instants, connecting it between the electrode and the product. High discharge current pulse speeds up the destruction of the molten metal bridge between electrode tip and workpiece, thus lowering the time needed for arc re-ignition and improving depostion process stability. A special automated equipment has been developed to implement this process. Capacitor discharge is done using power thyristor with series-connected inductance for limiting discharging current rate of rise and for limiting discharge current peak value such that it is not impairing thyristor reliability. The pre-charging of the capacitor is done by an auxiliary power supply. Several thyristor-capacitor networks can be used in parallel to allow for multiple current pulses mode and to reduce RMS currents in capacitors