Influence of mill scale on weld bead geometry and thermal cycle during GTA welding of high-strength steels

Abstract

High-strength steel heavy plates are usually covered with a mill scale after production. Morphology, structure, and chemical composition are determined by several factors, e.g., rolling parameters, cooling rate, quenching method, and alloying elements. As the mill scale might cause pore formation and process instability, it is preferably removed prior to welding. In welding practice, the removal of scale is in many cases insufficient and can lead to welding defects. In this paper, the influence of a scale layer on the weld bead geometry and thermal cycle during GTA welding is analyzed. Several high-strength steels with different chemical compositions and plate thicknesses have been used for bead-on-plate welding. The influence of mill scale on penetration depth and cooling time is analyzed and a connection to the varying fluid flow in the weld pool is drawn.