I made a small gas-forge for a friend from a 25cm diameter steel pipe and all the required refractory material. I wanted to see what it was capable of so I tested it at 50kpa and the air inflow at 50. What I got astounded me. Within a few minutes the thick piece of leave spring (5160 high carbon steel) was glowing white hot. It was welding temperature for sure. I wanted to try and weld a billet using the forge and I did, but that is Part 2.