0
Hydrogenation
One of the effects of hydrogenating vegetable oil is to raise the melting temperature, making it a solid instead of a liquid at room temperature.
mostly is the hardening done by induction hardening machine, I know also manufactures that do this using the flame hardening method.
in my opinion surface hardening is applied only on the surface while the true hardening is applied in the whole part of the metal....
what the was on tooth hardening day?