Electron beam welding of 2205 duplex stainless steel with nickel-based filler wire using multi-beam technique

Abstract

The duplex stainless steels have many favorable properties attributed to their two-phase microstructure consisting of almost equal fractions of ferrite and austenite. Therefore, they are widely used in the offshore, petroleum, and chemical industries as a base material for pressure vessels and pipelines. Such components often possess large thicknesses, which can be effectively welded with electron beam. This process is characterized by rapid cooling combined with a relatively great loss of nitrogen, resulting in insufficient austenite formation. To compensate this phenomenon, the addition of nickel, in the form of wire, was performed in this study. This promoted the formation of austenite at the same cooling rate, so that approximately an equal amount of ferrite and austenite was achieved. Beam oscillation was applied to maintain good dilution even at large depth/width ratios. Furthermore, the multi-beam technique was implemented to reduce the spatter formation and provide a higher process stability. This allows the spatial, but not temporal, separation of the melting-off of the wire and the main welding process. The joints produced in this way exhibit a good weld dilution and consequently an austenite distribution with a low inhomogeneity. Additionally, a narrow heat-affected zone was produced.