The client company manufactured mainshaft assemblies consisting of two stainless steel shafts friction welded to a central mild steel rotor. The process is technically successful but, with only small batches, high set-up costs prompted the company to request a Joining Forces* Product & Process Review to assess alternative joining technologies.
A Feasibility Study was recommended to investigate two techniques - Metal Active Gas (MAG) and Electron Beam (EB) welding, and trials were held at TWI using the client's materials.
In the MAG trials, energy input required control, sometimes interrupting welding to dissipate heat. It is unlikely that the 28 minutes welding time would reduce greatly with a fully mechanised system.
The EB trials gave problems with low welding speed (to allow nitrogen outgasing from the weld pool). The welding time of 3 minutes suggested time savings, even allowing for preparation, assembly and chamber evacuation.