Slope Out Welding Development for Thick Section Electron Beam Welding for Pressure Vessel Applications

Abstract

As part of a Department of Energy (DOE) funded programme assessing advanced manufacturing techniques for SMR applications, the Nuclear AMRC and EPRI have been developing Electron Beam Welding (EBW) parameters and procedures based upon SA508 Grade 3 Class 1 base material. For linear EB welds, the start and stop regions can be managed by using sacrificial run on/off blocks. However, for circumferential welds, such as joining shell to flange components, the use of sacrificial material is not possible. As such an effective method of closing the keyhole must be developed to ensure that weld defects are not entrained. This process is termed ‘slope out’ welding. This paper presents results from the steady state welding in the 80–90 mm material thickness range, showing that weld properties meet specification requirements. Subsequently the paper describes the steps in developing an effective slope out welding procedure for circumferential welds. Weld quality was assured by Phased Array Ultrasonic Testing (PAUT) in conjunction with weld sectioning. All welds were assessed against ASME V requirements. The results presented in this study clearly indicate that defect free and repeatable electron beam welds, including the slope out region, can be produced on thick section pressure vessel steel.