Why is “pushing the puddle” the only recommended direction for welding aluminum?
When the aluminum oxide forms on the surface, it also migrates below the surface. The heat from the welding process causes the aluminum oxide below the surface to rise into the welding site. By using the push technique---also known as an arc cleaning action---the 100% argon gas acts as a snow plow to push the oxides out of the way and to the sides of the weld site.
Note: The welding nozzle for aluminum is usually larger than a steel MIG/braze nozzle to accommodate the increased gas flow (25 to 45 CFH depending on the gun and nozzle.) Pushing the puddle, the weld will be cleaner with improved shielding gas coverage and reduced weld bead contamination.
Finally, what is the recommended standoff distance (distance from the nozzle to the work surface) when welding aluminum?
The distance from the nozzle to the work surface is 12 to 13 mm with a gun angle of 80 degrees from perpendicular. There should be no side to side movement when welding aluminum.
Going back to the welding discussion with the four techs and Schaffer---who has participated in every I-CAR class I have conducted at the shop so he would have the knowledge and skills his techs have---we welded the bead on the Series 7 extrusion with 5554 wire. These were the results with no practice.
On the other hand, a short bead happened when the first tech forgot to measure the extrusion’s thickness and set the welder for it. Ladies and gentlemen, this is why we need to continue to train on a regular basis.
Abby Andrews