Abstract

Nowadays, great efforts have been destining to obtain steels with ultrafine grains through viable industrially routes. These efforts are justified by cost reduction with the alloy elements and the improvement properties from plain carbon steels, which increase the aggregated value and its commercial range application. However, to obtain ultrafine grains steels with stable microstructure represents a hard task, owing to a strong tendency for grains growth. For this reason, some fine grains microstructures are inherently unstable which turns necessary to promote mechanisms that restrict grain boundaries movement to stabilize these microstructures. The cementite particles precipitation during the thermomechanical processing can produce a stable and homogeneous microstructure. In this work, the influence of cementite precipitation in microstructure refinement of low carbon steel, as well, the high angle boundaries generation during the warm processing were investigated. During the accomplishment of this work, two sheets of steel were used; a 0,16C steel (Cosar) and another of ultra-low carbon (IF), as reference. The subcritical field deformation in quenched and tempered samples was previously imposed by the torsion test. The use of the EBSD (Electron Backscattering Diffraction) technique enabled the attainment of data related to the misorientation amongst grains and/or sub-grains after isothermals torsion test.