Introduction into the electron beam welding of austenitic 321-type stainless steel

Electron beam welding has great potential in the welding of engineering materials, since very narrow and deep penetration is possible with this process. Austenitic stainless steels are prone to inter-granular corrosion when subjected to sensitizing heat treatments between 723 and 1073 K, due to the formation of a titanium-depleted zone adjacent to a titanium-rich zone. However, during the electron beam welding of this material, the heat affected zone extends only to a narrow region across the weld pool, thus resulting in a lesser degree of defects in the weld zone. The present study is conducted to investigate the mechanical and metallurgical properties of electron beam welded austenitic 321 stainless steel. Consequently, microhardness tests across the heat-affected zone and tensile and impact testing of the resulting welds were carried out, with SEM and micro-particle induced X-ray emission (μ-PIXE) being carried out to study the microstructures and element distribution in the weld zone. In addition, analysis of the first- and second-law of thermodynamics of the welding process was carried out. It was found that the heat-affected zone increased as the workpiece thickness increased and that dendritic transverse microcracks were present at the boundary of the molten and solid regions.