I did this project with under 150 amps of power at any time. And never needed any more then 100 to weld. I just used some more power to heat more quickly.
I did this with straight DC current. That means the torch is charged (-) and the ground is charged (+). This type of welding flies. You can only stay in one spot so long or you will blow a hole right through the 0.387″ thick material. I weld this so fast that most don’t believe it. The stringers web or face is over 3/8″ thick the treads are 3/16″ thick diamond plate.
I welded all the treads and top deck in today. It is also welded underneath but you can’t see it.