TWI Industrial Member Report Summary 898/2008
By C Punshon
Electron beam (EB) welding offers many advantages for thick section fabrication, particularly when applied to large structures where significant savings in both costs and time are anticipated. To date, however, the full potential of the process has not been realised commercially because of restrictions associated with working at high vacuum with the entire structure to be welded enclosed in a vacuum envelope.
TWI has demonstrated that operating the EB process in the pressure range 0.1-10mbar (so-called 'Reduced Pressure' or rough vacuum) in preference to high-vacuum (~10-3mbar) offers the possibility of eliminating the need for a vacuum chamber by permitting the practical use of local sealing and pumping.
To date, however, Reduced Pressure EB (RPEB) welding has only been applied industrially in a few specific cases. It is envisaged that many more industrial applications of the process could be promoted, and the true viability demonstrated by the further development of practical local sealing devices.
The purpose of this project was to research and develop simple local sealing devices for a range of component types and applications.
The objectives of the work reported here were to:
- Design and construct an experimental local sealing and pumping test facility to permit evaluation of various seal/pumping concepts.
- Establish the optimum local sealing method in the pressure regime consistent with reliable welding performance (ie 0.1-10mbar).
- Establish a demonstration facility at TWI with sufficient flexibility to permit the practicality of EB welding using local vacuum on a variety of component types to be examined.