COMPARISON OF LIQUIDUS AND SOLIDUS TEMPERATURES OF STEEL CAST INTO INGOTS IDENTIFIED BY DIFFERENT THERMO-ANALYTICAL METHODS

In the framework of optimising, correct setting of the casting process, knowledge of solidus temperature (T-s) and especially liquidus temperature (T-L) of produced steel grade is necessary. There are options to determine these temperatures: the use of empirical equations or calculations by specialised programs (thermodynamic databases). These calculations are based on the data of steel chemical composition and final temperature of phase transformation is then its reflection. T-s and T-L values then may not completely correspond to reality as well. It is very appropriate to employ a combination of different methods of thermal analysis and theoretical prediction for confrontation of experimental and calculated T-L and Ts. Three modern devices for high temperature thermal analysis and two specialised programs of theoretical prediction are available at the Faculty of Metallurgy and Materials Engineering. Direct thermal analysis method (dirTA) and parallel currently mass-enhanced method of thermal analysis, differential thermal analysis (DTA), were used for determination of T-L and Ts of studied real steel grades. Simultaneous application of both methods allows to reduce significantly disadvantages of each method and recommend proper T-L and Ts into the casting process and real conditions of industrial partner. Paper is focused on the discussion of T-L and Ts of steels cast into ingots (9 melts; 7 steel grades) analysed in the frame of a project TA0410035. Submitted evaluation refers an importance of the parallel utilization of different methods, their accuracy and reproducibility and also the divergences between T-L and Ts experimentally determined, empirically calculated and predicted by thermodynamic SWs' calculations.