CO2-shielded arc as a high-intensity heat source

The characteristics of a CO2-shielded arc are studied to evaluate its potential as a novel heat source for material processing, with lower costs and higher productivity than that of the tungsten–inert gas (TIG) arc. A double-gas-shielded system, using both CO2 and an inert gas, is employed for the arc torch; this minimizes consumption of the tungsten electrode and gives arc stability equivalent to an argon TIG arc for 1800 s operation. The arc voltage of the CO2-shielded arc is about 19 V for an arc current of 150 A and an arc gap of 3 mm, which is much higher than the 12 V obtained for an argon TIG arc. The CO2 constricts the arc, resulting in an increase in the maximum heat flux density at the anode surface by a factor of about 10 relative to the TIG arc. The penetration depth of stainless steel melted by the CO2-shielded arc is much larger than that for the argon TIG arc. It is concluded that the greater heating power of the CO2-shielded arc, which is due to the greater arc constriction, in turn a consequence of the greater specific heat of CO2, should lead to a large increase in material processing productivity.