Analytical studies on thermal behaviour and geometry of weld pool in pulsed current gas metal arc welding

In view of the criticality of pulsed current gas metal arc welding (P-GMAW) due to simultaneous influence of the pulse parameters on thermal and metal transfer behaviour of the process an analytical model has been developed for predicting the temperature and geometry of the weld pool by appropriately considering two types of heat sources of different nature. The model considers the impact of heat in droplets of filler metal depositing in the weld pool in addition to initial arc heating. The model assumes the primary heat transfer to weld pool is the initial arc heating considered as continuous heat source (arc heat source) of double ellipsoidal nature followed by deposition of superheated filler metal considered as point heat source of interrupted nature superimposed on the first one. The dissimilar nature of the two heat sources is treated by different analytical techniques to estimate their temperature distribution in weld pool and HAZ at its vicinity. The geometry of the weld pool has been estimated by evaluation of the weld isotherms causing melting of the base metal under the influence of two heat sources acting on the weld pool. The impact of impinging droplets on weld pool has been considered to determine the depth at which the droplets transfer their heat in it. The predicted temperature and geometry of the weld pool as well as the temperature of HAZ are found well in agreement to the experimental values with a deviation of the order of ±10% in case of the weld deposition of Al–Mg alloy and commercial aluminium especially at high mean current of the order of 180 A and beyond the transition current of the filler wire. However, prediction of weld pool temperature and weld geometry is relatively different at comparatively lower mean current of 150 A below the transient current of the filler wires is not up to the mark.