I've been welding a bit of mandrel bent aluminium tube lately and am running into a bit of trouble. As much as I clean the joints and the outside I'm getting a lot of contamination from the bending lube on the inside of the tube. It seems to melt and flow into the weld pool as it heats up. I've tried cleaning the lube out but there always seem to residue left over.Has anyone had the same problem and found a solution?