I have some questions on welding structural steel tubulars (drill stems) together to make a small bridge. I have access to a diesel driven arc welding machine and I wanted to know how to weld these pipes together. The sizes I have range from 2 3/8" to 5 1/2" outside diameter. I am not 100% sure how thick the walls are. It seems I may need to MIG weld them. Can someone let me know what materials I need to properly weld these pipes together? Thanks!