Effect of Warm Rolling Process Parameters on Microstructure and Mechanical Properties of Structural Steels

Warm rolling has grown interest as means of cutting down costs and of extending the application range of hot-rolled products. However, high resistance to deformation limits its application. Warm rolling is presently not in practice for carbon steel rolling in any of the SAIL plants. In view of this, the feasibility of warm rolling of structural steels, namely E250/E350/E450 steel grades, was conducted in the Experimental Rolling Mill to evaluate the effect of warm rolling parameters on deformation behavior, microstructure and properties of structural steel. The deformation temperature range was determined using JMatPro software for carrying out warm rolling of the selected grade of steels. Processing maps were also constructed to determine the safe working window for warm rolling. The microstructure of warm-rolled samples dominates fragmented Pearlite with elongated ferrite. Decrease in temperature results in more fragmented pearlite in the microstructure. The increased ratio of fragmented pearlite in microstructure leads to higher strength in structural steels. Improvement in yield strength and tensile strength by more than 12% with same toughness in properties is observed for warm-rolled sample compared to the conventional hot-rolled sample. From the results, it is inferred that warm rolling can be used to achieve better mechanical properties with the same alloy chemistry.