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EB and MAG process comparsion

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.

The work concluded that both welding processes were suitable. MAG used standard equipment, and mechanisation would improve control of the operation. Many subcontractors offer EB using relatively simple jigs, and the next step would be to EB weld a 'simulation' rotor shaft.

A company spokesman said that investigating alternative production methods had successfully freed them from the worry of being locked into a single supplier and manufacturing route.

For further information please email contactus@twi.co.uk

Joining Forces was a UK government sponsored programme which ran 1994-1999.

Friction welded mainshaft assembly. MAG and EB welding are viable alternatives
Friction welded mainshaft assembly. MAG and EB welding are viable alternatives
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