Numerical and Experimental Investigation on Single Side, Double Side and Heat Sink Assisted Submerged Arc Welded Butt Joint of Stainless Steels

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The submerged arc welding is widely used in fabrication of thick materials due to its ability to achieve greater consistency, higher productivity, deeper penetration, and high deposition rates. The primary process variables in a submerged arc welding (SAW) process are current, voltage, speed and electrode extension. The main objective of the present investigation is to study the thermo-mechanical behavior and characterization of submerged arc welded joints and also to develop a suitable technique to minimize distortion. In this work, numerical models were created to study the thermo-mechanical behavior of the weldments. The thermal analysis was conducted by incorporation of a volumetric heat source and with use of temperature dependent material properties. Subsequently thermo-mechanical analysis is conducted for determining the residual stresses and distortion. The results of thermal history and distortion obtained from numerical analysis were compared with the experimental outputs. Also in this work, prediction of weld induced distortions of large structures using equivalent loading technique was performed by considering average plastic strains. Here the actual transient phenomena of the weld is simulated by considering the application of separate average loads at start, middle and end regions along the weld line. The results obtained from numerical model were validated with experimental results. This numerical model was further extended to a large welded structure for prediction of weld induced distortion using the proposed equivalent load based technique. The numerical analysis in this work was performed using ANSYSTM software. In the present experimental work square butt joints were fabricated with top and bottom reinforcements and without any edge preparation in order to reduce the time and also cost involved in the edge preparation. Single response and multi response optimization were carried out in order determine the most influential parameters. In order to minimize the angular distortion in butt welds a heat sink fixture was designed and developed for this purpose. The conventional welds were compared with that of heat sink to study the effects of heat sink on angular distortion and mechanical properties. Also in this investigation double side weld joints were fabricated and overall bead profile as well as mechanical properties was explored. Finally the effect of surface active flux on weld bead geometry was studied.
Supervisors: Pankaj Biswas and Pinakeswar Mahanta