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TWI Industrial Member Report Summary 399/1989
By I M Norris
Background
When laser welding thick (>10mm) materials at high power and slow welding speeds ( <1m/min) the welding process may be adversely affected by the formation of laser induced
plasma above the workpiece surface.
A number of techniques have been developed to suppress or eliminate plasma formation above the weld and hence increase laser welding performance. The technique that has received most research attention is one in which a jet of gas is blown at the top of the weld to disrupt plasma formation. In most cases, the gas employed in the plasma control jet and associated weld shielding devices is helium which has been reported to be effective by virtue of its high ionisation potential and therefore reduced tendency to plasma formation. Although effective, helium is an expensive gas to use and its adoption can significantly increase production costs.
It was the purpose of this work to assess the feasibility of substituting argon for helium in both the plasma control jet and the weld shield when making partial penetration laser melt runs in 25mm thick and full penetration melt runs in 12mm thick structural steels.