Just an fyi for others. I just successfully cut 3/8" steel.
20IPM, 45amps, .060 cut height, .120 pierce height, 1.25 sec pierce delay, 0.060" kerf width
I had 12 IPM initially, but it kept blowing out. When I went to 20 IPM it cut without incident. A bit of backside dross, but pretty good otherwise.