Feasibility study of acoustic signals for on-line monitoring in short circuit gas metal arc welding

摘要

The acoustic waves produced by the gas metal arc welding (GMAW) contain information about the behaviour of the arc column, the molten pool and droplet transfer. In this study measurements of acoustic waves generated during GMAW process were performed. Acoustic waves were measured in the surrounding air and in the parts being welded by employing a microphone and PZT sensor. To evaluate influences on sound generation extensive experiments were performed with two different unalloyed carbon steels: DIN RSt13 with 0.1% C and DIN Ck45 with 0.46% C, using two types of shielding gas: CO{sub}2 and gas mixture by its brand name Crystal (90%> Ar, 10% CO{sub}2) and welding on a slope to vary the distance between welding nozzle and welding part. Acoustic signals were processed to obtain time domain and frequency domain descriptors. Some relationships between descriptors and the weld process characteristics were investigated. Results indicate that the arc sound exhibits distinct characteristics for each welding situation and that the main source of acoustic waves in short circuit metal transfer mode is arc reignition. From acoustic signals one can easily assess process stability and detect welding conditions resulting in weld defects.