I was checking the prices on our filler wire the other day and found that for a pound of 4643 it was over $21.00 vs $5.31 a pound for 4043.  The part we build is all 1/2" 6061-T6 aluminum and does not get heat treated after welding.  I can't see that big of strength difference between the 2 wires in the as welded condition.  Do you guys agree.  We do not need good impact resistance for this part either.  The F#'s are the same for both of these fillers so I could switch without violating any essential variables in D1.2 (2003).  The procedures were qualified with the 4643 in the as welded condition before I got here.  They had a heck of a time getting them to pass.

Kix