Unveiling Impact of Electron Beam Optics on Weld Attributes in EN30B Steel

Abstract

The influence of electron optics in terms of beam oscillation (BO) has been studied on weld quality of several steels and reported to develop cosmetic weld with smooth surface and enhanced weld properties. However, effect of electron beam oscillation on the weld quality of medium carbon low alloy steel, especially EN30B, have not reported well and investigated in this study. By manipulating magnetic lens in-line with electron beam, the diameter of oscillating beam (OD) and its effect on weld quality has been studied. The OD was changed between 0.5 mm and 2 mm. Numerous tests, including XRD, SEM, EBSD, hardness, wear, and tensile, were used to characterize the weld quality. Welds with BO significantly lowered the heat input rate than welds without oscillation. In presence of beam oscillation, retained austenite (RA) in the weld increased and it became least in welds made without BO. Tensile residual stress was found in the fusion zone (FZ) and it was higher with beam oscillation, especially with higher OD. In contrast to columnar grains predominantly found in welds made without BO, significant equiaxed grains were identified in welds made with BO. Nonmetallic inclusions (NMIs) in the weld became finer and less by use of BO. Introducing BO enhanced the hardness and reduced wear rate of weld, particularly at greater beam OD. Although Weld strength was diminished in comparison to the base metal (BM), beam oscillation increased the weld's ductility and strength.