Influence of focus and deflection when comparing electron beam welds to laser welds at varying parameters in 304 SS

Abstract

In many cases, both laser and electron beam welding may be considered for critical applications involving a wide range of structural materials. The ability to use both processes to make comparable welds in terms of both weld profile (penetration) and microstructure provides considerable process selection flexibility. In this study, autogenous, partial penetration welds on 304 and 304L SS were made using both fiber laser and electron beam processes. To simplify the analysis, many parameters were kept constant between processes, including working distance and spot size. The main variables, power and travel speed, were varied individually. Beam analysis was conducted using a PRIMES Focus Monitor to characterize the laser beam and a pro-beam diagnostic tool (PBD) for the electron beam. Electron beam welds were deflected or defocused to achieve a spot size similar to that of the laser welds, approximately 500 μm. The deflection pattern chosen for electron beam welding was made to mimic the power distribution of the laser. A similar melting efficiency at varying powers and travel speeds was maintained for both processes. Geometries and microstructures of the deflected and defocused electron beam welds and the laser beam welds are compared and related to process parameters.