TWI Industrial Member Report Summary 22/1976
By W O Dinsdale and E D Nicholas
The effects of a range of both machine and externally controlled variables has been examined for 25mm diameter solid bar friction welds between aluminium alloy HE9 and EX 58B (321S12) stainless steel. Weld quality was evaluated by means of the hammer bend test, shear test and metallographic sectioning.
The results showed that joints of good bend strength could be achieved but that the ductile heat affected zone (HAZ) was acting as a hinge so that maximum strain was not being transmitted to the interface. The shear test was, however, much more searching. Variations in force and burnoff distance did not affect weld strength but higher or lower welding speeds than normal appreciably reduced weld integrity. It was also shown that the HE9/stainless steel combination was intolerant to variations in surface finish and contamination. Metallurgical examination indicated the presence of intermetallics at the weld interface and suggested that the weld quality is impaired if the thickness is greater than 2 micrometers. It was also observed that The Welding Institute in-process monitor would not give an accurate indication of weld quality where several parameters can fluctuate simultaneously.