DUAL WELDING OF HIGH STRENGTH LOW ALLOY (HSLA) STEEL AND COMPARISON OF MECHANICAL PROPERTIES WITH INDIVIDUAL WELDING PROCESSES

Abstract

Welding is a major joining technique employed in hi-tech industries like in nuclear, aerospace and aeronautical, submarine and shipbuilding and pressure vessel applications for the production of high performing resilient structures. Tremendous efforts were made in the last couple of decades showing remarkable development in new welding technologies for defect free resilient structures capable of excellent in-service thermal and structural load bearing features. The objective of this research work is to find the alternative welding methods for welding of aerospace alloys, pressure vessels and in industrial applications. So far, very little attention is given towards multi-process welding (hybrid welding and dual welding). The multi-process welding procedures combine two welding processes for joining of metals on one work-piece. Through multi-process welding, the advantages of two welding processes can be combined. The combination of the two welding processes reduces thermal distortion of the welded work-piece and assures weld penetration. Although some research is done on hybrid welding, but still the dual welding process is mostly unexplored. Low alloy steels (may or may not requiring post weld strengthening heat treatments depending upon the in-service loadings) along with stainless steels are the potential candidate materials. Heat Affected Zone (HAZ) and Fusion Zones (FZ) are developed during welding process and subsequent cooling of the metals have significant effect on the microstructures, physical properties, mechanical properties and stress distributions. In this research work Dual welding process is selected as welding process. Two welding processes are selected and tensile samples are prepared by these welding processes. High Strength Low Alloy (HSLA) steel is used for the welding process. The effects of the dual welding process on the mechanical properties of HSLA steel are studied. The comparison of different mechanical properties such as tensile strength, yield strength, percentage elongation and hardness is made at the end. The microstructure analysis of weld beads has also been made in this work. In the last chapter, the results are discussed and some objectives have also been suggested for further work.