TWI Industrial Member Report Summary 608/1997
D S Howse
Plasma welding offers increased electrode life, reliable arc starting, improved arc stability, reduced current levels and increased welding speeds over TIG welding. However, the process is largely used for non-ferrous materials such as aluminium and titanium sheet and, hence, has acquired a reputation as a process which can only be used with some difficulty.
Plasma arc welding is similar in some respects to the TIG process in that it uses a non-consumable electrode to generate an arc between it and the workpiece. The main difference is in the torch design in which the ionised gas is separated from the shielding gas and forced through a nozzle. This produces a more constricted, denser current, columnar arc column than TIG welding,  which in turn leads to greater productivity benefits compared to TIG welding.
Keyhole plasma welding generally requires welding parameters to be carefully balanced whilst welding to maintain the stability of the keyhole and the weld pool. Close control of arc current, welding speed, gas flow and stand-off distance are required.
It was the intention of this work to investigate further the effect of the keyhole plasma pulsed welding parameters on the bead shape of the weld to give full penetration welds in 3mm thickness carbon steel. It was also intended to use a Taguchi experimental approach which would investigate the effects of the parameters in isolation upon the weld bead shape. The final objective of this work would be to provide greater confidence in the use of the pulsed keyhole plasma process for thinner gauge materials.
- To define the effect of parameters for pulsed keyhole plasma welding in carbon steel sheet in order to gain greater confidence in its use for thinner materials.