TWI Industrial Member Report Summary 190/1982
By S De Rosa, J L Robinson, T G Gooch and R J K Nicholson
Background
An investigation has been initiated into the variation in weld bead geometry and penetration encountered during mechanised autogenous welding of materials nominally of the same type but originating from different casts. Austenitic stainless steel sheets (Types 304, 316 and 316L) of 1.6 to 3.4mm thickness have been examined.
Mechanised TIG equipment and procedures have been developed enabling the extent of variability in fusion characteristics to be defined. Penetration behaviour of the different casts was assessed, and comparison made primarily in terms of the depth-to-width ratio of the weld bead cross-section. Variable penetration was not solely associated with the TIG process, but was observed also in electron beam and laser melt runs.
Differences in penetration behaviour between casts could not be positively attributed to any single feature of the material compositions or microstructures, although the results indicated overall composition to be significant. Preliminary surface tension measurement indicated a slight trend for increased penetration to be associated with lower surface tension and with a more positive surface tension temperature coefficient.