The applicability of a welding process depends on the rate of heat input, which determines the residual stresses, the heat affected zone and the microstructural changes in the base material. An adequate approach of heat input through a heat source represents a crucial step in the welding thermal field simulation affecting the accuracy of mechanical and microstructural studies. This research work proposes a volumetric-moving heat source for the Gas Tungsten Arc Welding process (GTAW) based on an elliptic paraboloid geometry capable of representing shallow and deep, wide and narrow fusion zones, considering as shape parameters of the heat source, the fusion width and depth penetration. The interaction of the melting material flow in the weldpool and the heat transfer process were analyzed taking into account the effect of convective heat transfer in the heat input distribution in the fusion zone, and the weldpool shape variations during its displacement. The mathematical model for the GTAW thermal field was solved numerically by means of Finite Volume Method (FVM). The elliptic paraboloid model provided a comparable heat input to the classic double ellipsoid model. The estimated temperatures and the predicted geometry of cross-section weld bead by the proposed model are in a good agreement with experimental results. (C) 2016 Elsevier Ltd. All rights reserved.