TWI Industrial Member Report Summary 358/1988
By M D F Harvey and M H Rodwell
Despite advances in TIG welding process technology, a number of material related problems persist, which must be overcome if true weld reproducibility is to be achieved. Although a regular feature of TlG weld metal, slag island formation is not generally considered to be a major problem. However, several examples of serious arc disturbances and consequent inconsistent weld penetration as a result of gross weld pool slag island formation have been reported and a recent research programme at The Welding Institute identified a cast of Type 316 stainless steel sheet with this particular problem.
This report describes a study of the influence of shielding gas composition, travel speed, welding current and process techniques on, and the identification of the element responsible for, the formation of slag islands during the mechanised TIG welding of this particular stainless steel cast.