Signature image stability and metal transfer in gas metal arc welding

Abstract

This work presents a method for determining a stability index during welding by comparing signature images calculated successively from the welding voltage and current data. It is shown that, with a reasonable choice for the signature image window scaling, the stability index agrees with welding experience in the common gas metal arc welding transfer modes of short circuiting and spray transfer and reflects the decrease in stability inherent in the globular transfer mode. The effect of changing welding consumables, wire and shielding gas, is illustrated. The connection between the stability index and metal transfer phenomena is investigated, and it is shown that very detailed aspects of metal transfer are reflected in the stability index. It is concluded that the signature image stability index not only provides valuable data on the operating regions of welding processes, but also gives information which otherwise would only be available from cumbersome optical diagnostics.