Ultrasonic Detection and Characterisation of Electron Beam Weld Imperfections
TWI Industrial Member Report 1208-2025
By Dr Channa Nageswaran and Derek Holiver
Industrial Need
Electron beam welding (EBW) is different from arc welding in many ways and, in comparison, has particular advantages for joining thick section plates and pipes rapidly. Electron beam is a keyhole process capable of joining thicker alloys in a single pass as opposed to the multiple passes required for arc welding. Reliable non-destructive identification of discontinuities due to keyhole instabilities in EBW is required during welding. There is an industrial need to correlate between data collected during welding and flaws that are likely to appear in the joints.
The objectives of the project were to:
- Establish whether ultrasonic inspection can detect, and classify as planar or volumetric, imperfections in welds made by EBW, particularly root spiking porosity in the slope out region.
- Establish whether ultrasonic acceptance criteria for EBW can be generated that follow standards on product quality for EBW.
- Establish whether ultrasonic techniques can be used to assess imperfections in welds made by EBW with an elevated scanning surface temperature.
- High temperature TOFD implementation was feasible, offering an avenue for online monitoring of EBW during the welding process, particularly as part of the reduced pressure local chamber process.
Key Findings
- Imperfections in electron beam welds, including root spiking porosity in the slope out region, can be characterised by UT techniques using commercial off-the-shelf equipment, in 20mm carbon steel and 7mm titanium alloy.
- Characterising EBW indications by UT as volumetric (such as porosity) or planar (such as cracking) is difficult and likely to always be uncertain, especially for small pores and tips of planar indications.
- Establishing EBW workmanship acceptance criteria for UT techniques following BS EN ISO 13919-1 (2019) is feasible, provided the criteria are built on the length of a cluster of indications with signal amplitude above a threshold value.
- The acceptance levels provided in BS EN ISO 19285 (2017) provide a good basis for agreed criteria.
- High temperature TOFD implementation was feasible, offering an avenue for online monitoring of EBW during the welding process, particularly as part of the reduced pressure local chamber process.