Optimization of Processing Parameters in Deep Penetration Electron Beam Welding of Stainless Steel 316L for ITER Diagnostic Shield Module Application

Diagnostic shield modules (DSMs) fabrication for Upper Port 18 (UP18) of ITER application requires a deep penetration of 165 mm or more for the joint part so that large distortion of welded assembly is expected during the joining process. Given the engineering challenges posed by very thick weldment and the precise tolerances required for the DSM structure, electron beam welding was identified as a potential solution. A feasibility study using E-beam welding was therefore considered a priority. E-beam welding is a fusion joining process that produces a weld by impinging a beam of high-energy electron to the weld joint. E-beam welding has been widely used due to its advantages like narrow weld zone and heat-affected zone, low distortion, etc., although its application to large assemblies is often restricted by the need to use a vacuum environment. There are several standard E-beam welding parameters that need to be developed for each joint geometry and material. These include the beam current, welding speed, welding position, beam oscillation size, frequency, etc. This study provides the optimal parameters to obtain deep penetration without defects using response surface methodology (RSM) for austenitic stainless steel 316L. This methodology, consisting of experimental design, statistical modeling, and optimization is used to decide the optimal parameters.