Arc Cleaning for Increased Electrode Life—Process Parameters

Even before the present energy crisis and ever-spiralling petroleum products prices, auto makers were busy meeting the various statutory requirements which added to the weight and operating charges of vehicles resulting in increased fuel consumption. One of the means to reduce vehicle weight was through the use of Aluminium alloys in both structural and body parts. A gage-to-gage substitution of Aluminium for steel leads to a 65 percent weight saving.

The widely used technique of joining viz resistance welding, when applied to At, gives rise to problems because of the high conductivity of Aluminium, rapid contamination of copper electrodes by Al and presence of oxide layer on AI alloys, besides tendency of Al for solidification cracking.

This paper deals with aspects to reduce Al pick up by the electrodes and also to reduce surface splashing observed during welding of Al alloys. Arc cleaning is a recent method in which the sheet is cleaned immediately prior to welding, on the welding machine itself.

The parameters influencing the arc-cleaning process have been investigated and the results of the investigation indicate that-

(1) The main process parameters are arc gap, gas flow rate and arc time.

(2) The optimum arc gap is 0.7 to 0.9 mm Higher gaps result in melting of the sheet itself.

(3) At higher gas flow rates, cleaning efficiency reduces.

The process appears to be very useful in increasing the life of the electrodes thereby contributing to increased productivity.