Degala Venkata Kiran

Probing influence of welding current on weld quality in two wire tandem submerged arc welding of HSLA steel

Abstract Two wire tandem submerged arc welding (SAW-T) involves application of two electrode wires to form a single weld pool with one wire leading the other along the weld interface. Realisation of the influences of the lead and trail wire currents on the weld bead morphology and the weld strength are important in SAW-T. The authors here present an experimental and computational investigation on SAW-T process. The concept of central composite rotatable design is followed for designing the experimental trials. The final weld width and the reinforcement height showed greater sensitivity to trail current while the penetration was influenced primarily by lead current. A three-dimensional heat transfer analysis is carried out using finite element method. The computed weld profiles were validated with the corresponding measured results. The computed cooling rates showed a decline with higher welding current and, the corresponding sample welds showed reduced acicular ferrite percentage and lower weld strength.

Efficient Estimation Of Volumetric Heat Source In Fusion Welding Process Simulation

Mathematical models of heat transfer phenomena in fusion welding process can provide important physical insight on the mechanism of weld pool development, and compute temperature field and final weld dimensions fairly reliably in several welding systems. In particular, the conduction heat transfer based numerical models are relatively simpler and computationally inexpensive in comparison to the comprehensive heat transfer and fluid flow models although the later can undertake greater physical attributes in weld pool. One significant requirement of the conduction heat transfer based models is the predetermination of a volumetric source term to account for the heat input from the welding heat source. We present here two efficient approaches to define the volumetric heat source term which do not require a-priori information of the final weld joint dimensions, which has always remained a difficult task. The first approach involves an intrinsic mapping of the heat source geometry with the numerically computed melt pool dimensions within the framework of modeling calculations in an iterative manner and is validated for the prediction of final weld dimensions in autogenous gas tungsten arc welds with butt joint geometry. The other approach involves an analytical estimation of the volumetric source term as function of only the welding conditions and the initial weld joint geometry and is examined successfully for the prediction of weld pool dimensions and thermal cycles in tandem submerged arc welds with typical groove joint geometry.