Studium reálných jakostí ocelí metodami DTA a TMA

Abstract

The Bachelor thesis deals with thermal analysis of two real steel grades with different chemical composition using two different methods of thermal analysis: Differential Thermal Analysis (DTA) and Thermo-Mechanical Analysis (TMA).

The theoretical part is focused on general characteristics of iron and steel, including phase transformations according to metastable Fe-Fe3C diagram. It also includes description of some specific methods of thermal analysis with closer focus on DTA and TMA methods. Physical quantities associated with thermal expansion and possibilities of their calculation are also described.

In the experimental part of this thesis, the temperatures of phase transformations in the low-temperature area (up to 950°C) of real steel grades and their link with different content of some alloying elements are studied. Concretely it’s the start of eutectoid transformation (Ac1), end of transformation    (Ac3) and Curie point (TC). For study of temperatures of these phase transformations were used two methods of thermal analysis: DTA and TMA. Measurements, with the use of both methods, were realised using instrument Setaram SETSYS 18TM. Results of TMA measurements were also used for calculation of linear coefficient of thermal expansion and density depending on temperature (up to 1400 °C).

All mentioned steel properties were studied also theoretically and the calculations were realized using Thermo-Calc software which is based on CALPHAD principle. Calculated temperatures of phase transformations and other properties were compared with experimental data (DTA and TMA) and obtained differences were discussed. The results of each steel grade considering different chemical composition were also discussed.