1 Pass - 1.6 mm 5356 - approximately 22 ipm travel speed
23.0 V; 342 ipm wire feed speed
What is the best backing bar material for an aluminum groove weld?
There really isn’t a “best” material for a backing bar. To determine the most appropriate material, you must
consider a few things:
Is the backing bar going to be permanent or temporary?
For a permanent backing bar the answer is easy – use the same alloy as one of the groove weld components.
For temporary bars, consider these points:
Hard-coat anodized aluminum, copper, stainless steel, and ceramic can all be used.
Don’t weld directly on the backing material. A temporary bar is there only to support the root reinforcement.
Elements from the backing material may contaminate the weld.
Hard-coat anodized aluminum works very well. The thermal properties are the same as the base material
and the groove is easily machined.
Copper has a tendency to cool the weld more quickly than the other materials (copper cools quickly).
Stainless Steel has a tendency to heat up and cool the weld more slowly (stainless cools slowly).
Ceramic is available with adhesive for attaching directly to the base material, but is also very fragile.
Should the groove be square or rounded in a temporary backing bar?
Typically, a square cut groove is going to provide better results than a rounded (or bowl shaped) groove.
The images below show the result of a square cut in the temporary backing bar, the joint design, and the cross
section of the weld achieved.