For building racks and such, I use 7018. If I am going to forge the weld, I have had good luck with 6013 blending in after I heat and beat it. Sometimes, I tack two pieces together with 1/16" 6013 then flux and forgeweld them together. Of course, I only resort to this after I have tried the "drop-the-tongs weld" at least three times. Sometimes I stick it the first time, sometimes I stick it with Miller.