Session: MF-15-01 Fatigue and Fracture of Welds and Heat Affected Zones

Paper Number: 104710

104710 - POST WELD HEAT TREATMENT AND FRACTURE TOUGHNESS EVALUATION OF ELECTRON BEAM WELDED SA508 ALLOYS 

Whilst Electron Beam Welding (EBW) has been in existence for several decades, it typically requires the welded component to be housed within a conventional vacuum chamber in order to minimize diffusion of the electron beam, thus limiting the maximum overall size of the component. Recent advances in EBW by TWI (UK) have led to the development of a local vacuum system, whereby a local vacuum is implemented around only the welded section rather than the whole component, thereby avoiding the component size limitations associated with more conventional systems. A direct comparison between the two EBW systems does not appear to have been published hitherto and thus forms one aspect of the work reported here.

For the EBW low alloy steel SA508 materials employed in this study, the post weld heat treatment (PWHT) regime has also been investigated, since there has been some concern over the appropriateness of employing conventional PWHTs typically used for traditional arc welds. Charpy impact testing was performed to assess the initial toughness of the welds, with the notch located on the weld centre-line, within the HAZ, and within the parent materials. For SA508 Gr.3, Charpy testing suggested that only the full austenitise and temper heat treatment gave weld centre-line properties similar to the parent material. However, for SA508 Gr. 4N, a modified single step PWHT restored a high level of toughness performance to the weld metal, in comparison with the parent.

Finally, fracture toughness testing on the SA508 Gr. 3 and SA508 Gr. 4N materials has been undertaken to determine the upper shelf fracture toughness (J_1C) at 250°C, using multi-specimen compact tension (C(T)) test specimens. These data showed that there were little observable differences in the performance of welds produced by either the conventional high vacuum welding system, or the local vacuum system.

Presenting Author: Adam Cooper Jacobs

Presenting Author Biography: Adam Cooper is Technical Manager within Jacobs fracture mechanics testing team. He is responsible for the delivery of a variety of complex mechanical performance and evaluation experimental testing programmes to assess the deformation and fracture behaviour of structural materials for both existing nuclear fleet and new nuclear build.

Authors:

Adam J. Cooper Jacobs
Andrew Wisbey Jacobs
William Kyffin N-AMRC, UK
Thomas Dutilleul N-AMRC, UK
Mike Nunn TWI
Chris Punshon Cambridge Vacuum Engineering
Mike C. Smith University of Manchester
Ed Pickering University of Manchester
Vasileios Akrivos University of Manchester
Alex Carruthers University of Manchester