TWI Industrial Member Report Summary 121/1980
By E W L Norman
A review has been made of the literature concerned with the MIG and TIG arc spot welding of aluminium alloy sheet. There is a general indication that the MIG process can produce acceptable spot welds in arc weldable aluminium alloy sheet up to 3.2mm in thickness, and plug welds in thicknesses up to 6.4mm. The main drawback to the production use of the process would seem to be the general inconsistency in penetration and weld size, apparently associated with variations in the arc starting characteristics. While this can be overcome to some extent by allowing excess weld penetration or by the use of a backing bar, an identification of this variability and its elimination would seem to be necessary before the process achieves wider production application.
The d. c. TIG spot welding process with the electrode negative appears to be possible but limited in application by the need to control electrode tip geometry and problems in the removal of interfacial oxide films. This situation needs to be reviewed following the introduction of a. c. square wave power sources.