We're trying to qualify an overhead fillet weld procedure for the field joining 1/2" thick 304 stainless plates to an A992 beam.  The welds pass an initial visual, but when we cut the macroetch specimen, the weld has not completely penetrated at the root in the very inside corner.  We've tried several times with different welders, but with the same results.  The electrode being used is a 1/8" dia. Inweld 309L-16 (the erector chose this electrode because of the inexpensive price).  The recommended amp range is 60-110, but the welder has gradually increased that to 120 to 140 amps in an attempt to completely fuse the root.  The welders are running a stringer pass.  Does anyone have any ideas as to what can be done differently?