Studium vybraných termofyzikálních vlastností ocelí

Abstract

This thesis studies the temperatures of phase transformations of two selected real steels grades, which differ in their composition. These real steels grades are used for the production of continuously cast billets and subsequently for the production of seamless tubes in ArcelorMittal Ostrava a.s. and ArcelorMittal Tubular Products Ostrava a.s. The theoretical part is focused on describing the methods of thermal analysis and their use. The differential thermal analysis is one of the methods suitable to obtain thermodynamic and thermophysical steel data. This method was used in the experimental section to obtain phase transformation temperatures of the two steels. DTA method was experimentally performed on a Setaram SETSYS 18TM. Evaluation of the DTA curves was done in Setsoft. The temperatures of phase transformation of two steel samples were obtained at low and high temperature region (eutectoid transformation, transformation α → γ, transformation γ → δ, peritectic transformation, the solidus temperature and liquidus). The experimentally obtained temperatures of steel were extrapolated to equilibrium conditions. The acquired phase transformations temperatures were compared with temperatures set in binary metastable diagram Fe-Fe3C. Subsequently, the phase transformation temperatures were calculated by substituting chemical composition of the steel into computational relationships found in the sources and by using Thermo-Calc software and IDS. Calculated temperatures were compared with experimental results and their differences were discussed. The influence of individual parameters and results are summarized in the conclusion.