Using the sophisticated MAXStrain II unit, part of the HDS-20 simulator, the effect of intensive cumulative hot deformation on the final structural properties of non-alloyed low carbon steel was investigated. In the case of the MAXStrain II unit, the specimens are deformed by compression in two axes, which allows to achieve large cumulative strains. This fact, together with the possible course of suitable softening processes, represents a potential for research and development of materials with fine-grained structures. The microstructure of all samples of low-carbon alloy steel, deformed at MAXStrain II unit, was composed of a mixture of ferrite and pearlite; in the case of samples after accelerated cooling, hardening components were also detected in the microstructure (share up to 5 %). In all cases, during the MAXStrain II tests, the resulting ferritic grain of the steel under test was refined, with the finest microstructure showing an average ferritic grain size of 6.8 m. The resulting ferritic grain size decreased with decreasing deformation temperature and, in the case of lower overall equivalent strain, also with longer interpass time. However, the chosen cooling rate had a dominant effect on the resulting ferritic grain size.