The welding of aluminium and its alloys
Welding position
Welding in the flat or downhand position is preferred for all arc welding activities. It is easier for the welder to deposit high-quality weld metal at high deposition rates in the flat position than in any of the other positions. The weld pool is larger in this position with slower solidification and cooling rates, permitting gases to evolve from the pool and reducing the amount of porosity. The force of gravity in positions such as the horizontal-vertical, however, means that the weld pool tends to sag, making it more difficult to achieve an acceptable weld profile. These effects are more marked with MIG than with TIG. Flat position welding therefore gives the best quality weld metal at the lowest cost.
The designer should take these points into account when considering the design of a structure. Wherever possible welding should be performed in the flat position. This may require the fabrication of sub-assemblies that are more easily manipulated. Manipulating equipment such as rotators or faceplate manipulators are useful for items too large for manual handling. The use of this equipment, however, may require the welding of temporary attachments to the component to facilitate fitting the component to the manipulator. As much care must be taken with the welding and removal of these attachments as is applied to the permanent joints - formal welding procedures should be considered in order to exercise control over this sometimes haphazard activity.
