Grind a chamfer approximately 1/8" x 45 degrees on the end of your pipe, use 6011 or 6013 rod 1/8" diameter set on 130 amps.
I have used an old Lincoln AC welder for years and got good results with the above settings and rod. I prefer the 6013 rod, it seems to flow out better than the 6011. If you have trouble eith "burn thru". back it up to 115 amps, but your penetration won't be as good.