Huh. Peculiar for sure. It may very well be, in knives at least, relative to the heat treatment processes. You mess with the magnetic field, indeed, that's the simplest way to know when a steel is at the correct temperature to quench it, in order to harden the steel. It's called the critical temperature, and when it is reached, the steel undergoes a structural change, as evidenced by the fact that it loses it's attraction to a magnet run along the hot blade. When it's up slightly past 'non-magnetic', depending on the steel, you quench it.
As an aside, I align my quench tank so that the blade is pointed towards magnetic North, and quench them held horizontally, moving them back and forth in a stabbing motion. Some claim that the mag N thing is voodoo, but my blades universally harden up well, with almost no warpage whatsoever. So, it works for me. LOL!
Michael
www.radharcknives.com