Through continuous attention to customer needs and long-term research and development investment, our new product have recently been put on the market after successful trial in local customers.From this issue we will gradually unveil this new product.
About the author Dr.Juan Llano:
Deputy general manager of TSR
– Degree in Chemical Engineering. Universidad del País Vasco. Bilbao. 1981.
– Ph.D. course in Metallurgical Engineering. Universidad de Oviedo. 1989.
Part A. Introduction to the rolling process
Author:Dr.Juan Llano
During the rolling of the steel, the rolls are subjected to a heating and cooling cycle on each turn of the roll.
In the hot rolling process this cycle can be summarized as follows;
When the roll gets into contact with the steel bar to be rolled, due to the temperatures of the bar in the rolling mill and the heat generated by the deformation of the material and the friction, the surface of the roll undergoes a heating whose depth and extension depend on the passing speed of the bar, the temperature of the bar at the entrance and the deformation and friction of the material.
The roll is then subjected to the action of the cooling nozzles whose function is to reduce the temperature of the roll to prepare it for the next rolling and thermal cycle that will take place on the next lap.
These heating / cooling cycles cause cyclical compressive and tensile stresses on the roll surface at each turn, which can exceed the mechanical strength of the material and cause the formation of thermal cracks on the surface.
These tensions are outlined in the attached figure.
The action of this thermal cycling, and its consequence in the form of surface thermal cracks, is inevitable, although it can be reduced with several measures:
– Increase in the speed of the material (Less contact time with the roll surface)
– Optimization of roll cooling.
– Improvement of the mechanical properties and residual stresses of the roll material.
Next part: Roughing Stands of a Bar Mill.