As far as I know it only needs power, torque/speed don't matter. The highest power I did on the comparison was pretty much optimal I think. It heats up to 1902 degrees. 2000 is the max, but if you add too much power it goes kaboom, so higher is kinda risky.
Edit: Highest power on the test is a tier 5 magnetostatic on penultimate speed setting. Highest = kaboom.
Any suggested engines that heat it up to that point? Other than the magnetostatic, cause magnetizing those things is a pain, even if you can do it 16 at a time.
Edit: If I remember correctly, penulitmate means one before last