Rapid cooling of rolls

Optimal mechanical properties are achieved by using a combined heat treatment where the roll is quenched and tempered to the basic hardness first, and then the surface is hardened to reach the proper work hardness. These rolls are surface hardened in a dual frequency induction hardening machine, followed by rapid cooling with liquid nitrogen below -140°C, and then tempered at low temperature.
This way we can always achieve optimal levels of retained austenite.