SHIELDING GAS AND HEAT-TRANSFER EFFICIENCY IN PLASMA ARE WELDING

Variable polarity plasma are welding is widely used in the aerospace i ndustry for producing high-quality welds on aluminum. In plasma weldin g the are is produced in a narrow stream of plasma gas while workpiece shielding is accomplished by a lower velocity but higher flow rate st ream of shielding gas that surrounds the are. This paper will show tha t on aluminum welds both the melt zone and the heat-affected zone are appreciably decreased by this flow of shielding gas. Moreover, the amo unt of cooling is changed by the detailed shape of this flow as well a s the flow rate. On the other hand, it will be shown that excessively high shielding flow rates can cause undercutting from contamination in the shielding gas.