"THERMO MECHANICAL TREATMENT PROCESS FOR REINFORCEMENT BARS, OPENING UP NEW VISTAS"
In bar mills, directly after the last rolling stand, the bar passes through the Cooling System achieving a short and intensive cooling of the surface. Because of the reduction in the temperature at a rate higher than the critical rate for martensite quenching the surface layer of there-bar is converted to a hardened structure while the core remains austenitic.
After the intensive cooling, the bar is exposed to air and the core re-heats the quenched surface layer by conduction, therefore tempering the external martensite. The thermal profiles of the Surface and Core merge at the so called equalizing temperature that together with the final rolling temperature is the most important parameter to achieve the required mechanical properties.
Finally, when the bar is discharged on to the Cooling Beds, the remaining austenite transforms into a very fine-grained pearlite structure.
This process is called Thermo Mechanical Treatment process for reinforcement bars.