Industrial trials for hot deformation production of low carbon steel with fine ferrite grains were carried out. The different hot rolling parameters including the amount of strain and strain rate at each of six rolling stands as well as the final deformation temperature were designed to produce the required microstructure. Two types of low carbon steels, with/without Nb-addition, were used in this study to evaluate the effect of Nb addition. Stress induced grain refinement has been successfully achieved, aided by Nb, resulting in an average grain size of 4µm following the coiling process. The flow stress calculated at each of the six stands was used to follow the structure evaluation during processing.