but even this guy doesn't say that they just quench the blade in liquid nitrogen. You do it AFTER tempering. That's entirely different. If you just tossed red hot metal into liquid nitrogen, it would shatter. And you're still not putting nitrogen in it, and I see no reason why organic carbon would do the same thing as liquid nitrogen as it's the TEMPERATURE that is causing the hardening. Soooo....yah. Even if the frozen nitrogen is valid, the rest of the theory still doesn't line up.