Fiber laser and hybrid welding of T-joint in structural steels

Abstract

Laser welding processes are amongst the most versatile joining technologies, suitable for both, small scale and mass production. The advancements in laser sources and optics is allowing autogenous laser beam welding to infiltrate the manufacturing sectors where laser-arc hybrid welding has already replaced traditional joining methods. In order to be successfully applied, fundamental understanding of the process is essential to control the mechanisms affecting the weld formation. This dissertation concentrates on single-sided laser and laser-arc hybrid welding of T-joints in medium thickness structural steels S355 and AH36 with high power fiber laser.

The main research topic in this thesis is the investigation of factors affecting joint geometry formation in laser- and laser-arc hybrid welding of T-joints. Depth, width and surface topology of the weld define the mechanical properties and performance of the joints. Effect of welding parameters on weld profile has been studied using three different optical set-ups. The work aims to understand phenomena behind weld shape variations and to propose means for reducing the complexity of the welding process.

In summary, this work provides considerably enhanced understanding of the formation mechanisms of weld geometries under different processing conditions. The results of this work aim to contribute to expanding the applications of autogenous laser welding processes in manufacturing. Knowledge gained can readily be implemented to practical use, particularly in machine- and shipbuilding industry, where autogenous laser welding could be eligible for wide range of applications.