C. Kolan, A. Wrońska, A. Lis, G. Golański
October 12, 2013
This paper presents results of quantitative analysis of ferrite grains in low carbon steel C15V with microalloying addition of vanadium. Thermomechanical treatment in the intercritical (α+γ) region was performed using the dilatometer DIL805A. On the basis of dilatometric researches the critical temperatures of α ↔ γ transformation for C15V steel during heating with v 5−8 =0.5 K/s and cooling with v 8−5 =1 K/s were estimated. The steel deformation was carried out with application of two different variants: deformation in (α+γ) region after cooling from full austenitization temperature and deformation in (α+γ) region after heating from ambient temperature (ferritic-bainitic microstructure). The effects of these treatments were observed by means of a light optical microscope in bright and polarized field. The quantitative analysis of microstructure was investigated using Image Pro Plus (IPP) program. Characteristic parameters for ferrite grains such as: field area, average diameter, shape factor were estimated. For each of these parameters, histograms and maps of average grain diameter distribution were performed using STATISTICA 9 and IPP programs. It was observed that deformation in the intercritical range (α+γ) promotes the occurrence of many ferrite nucleus in the obtained structures, especially at grain boundaries. For low carbon steel this results in formation of very fine microstructure.