Abstract
The low – alloyed Cr-Mo based steels are very sensitive to internal crack occurence especially in cases when they are hot rolled from round continuously cast blooms. The scope of the paper is therefore dedicated to the study of microscopic crack mechanism of 25CrMo4 steel variant. We have demonstrated that the crack presence after hot rolling strongly depends on the microstructure composition as well as on the segregation of chromium, manganese and molybdenum content. The main conclusions are supported by the metallographic analysis that was performed on the surface and in the center of the investigated billet and also the microchemical line analysis carried out with the energy - dispersive X - ray spectroscopy (EDX) to precisely determine the internal segregation behavior of above mentioned elements. Moreover we have also utilised the microhardness determination of Cr-Mo steels.