A short, intensive but very precise in-line quenching of the rolled bar is imparted in Thermex^® process through a proprietary system and this results in a hardened periphery.

On further cooling of the bar in atmosphere, a thermal exchange (THERMEX) occurs between the core and cooled outside martensite surface whereby the resultant bar structure is a distinct tempered martensite at periphery and a fine grained ferrite-pearlite structure in the central zone.