I had my torch running today so I ended up clamping the steerer in the alignment table fork steerer thingy and warming up the steerer. I applied some heat and waited 2 mins and gave the stub a twist and nothing, I said "forget it, head to the mill" (I have a bridgeport set up at 90 degrees for mitering fork blades). It sat for five more mins, and I gave it another twist and the piece came right out. There was only 75mm of "slightly corroded" stem that came out. I was really shocked that it took the amount work and really "fell out" when enough heat was applied. Which was still under 600F.

Unfortunately, you can't heat the steerer while it's in the head tube. I think next time the giant soldering iron will spend more time in the steerer. It was pretty humbling getting beat by such a thing. I look forward to the next one.