Laser arc hybrid welding, owing to the complimentary features of the two different heat sources, offers transformational improvement in welding of pipelines. The main benefits are deep penetration and fast processing speed, owing to the highly focused laser energy and improved gap bridging ability from the arc based power source. This enables significant increase of productivity and reduction of welding distortions, as compared to traditional arc-based welding techniques. In pipeline welding the welding time is a major factor in determining the build rate of pipelines. Laser arc hybrid process has been shown to be able to increase the productivity of joining at least by a factor of six, when compared to arc-based processes. However, the effects of such process on compositional gradient through the weld metal thickness need to be understood as a function of different process variables and bevel design. The faster travel speed from the use of a laser source would also result in a faster transient thermal cycle which may result in formation of undesired metallurgical phases in the weld metal and the heat affected area.
In this project, the interaction between the arc and laser heat sources are studied in relation to homogeneity of composition, heat affected zone microstructure and metallurgical phase formation. Thermal simulation using Gleeble Thermo-mechanical simulator, carried out by the other academic partner, will indicate the thermal profile that is necessary to avoid any shear transformed phase formation for a specific composition. Instrumented hybrid weld performed at the Welding Engineering and Laser Processing Centre of Cranfield University generates the thermal cycle data which can be correlated to the total heat input. The final aim of the project is to create a process model for hybrid welding which will be supplemented by the continuous cooling transformation (CCT) curves generated by thermal simulation. Full pipe test welds will be generated to perform the necessary qualification tests to optimise welding process parameters.
For more information on this project please contact Dr Supriyo Ganguly, firstname.lastname@example.org.