The aim of this thesis is to identify the basic thermal effects by recording liquidus and solidus temperatures, and to determine the optimal heating and cooling program by recording DTA signals of nickel – chromium – iron alloys. The problem of determining the characteristic temperatures, Tliq. occurs in alloy systems with a low value of latent heat, HL, especially in solidification process and the associated hysteresis detection of liquidus temperature. For the successful production of specific types of nickel alloys, the determination of the liquidus temperature, Tliq. is essential since based on the liquidus temperature, individual temperature ranges where we perform individual technological operations of secondary metallurgy (such as oxidation, refining, etc.) as well as the settings of parameters for continuous casting of slabs are determined. All of the above-mentioned parameters directly affect the quality of the manufactured alloy. The latter mainly in terms of controlling the casted steel in the form of macro and micro secretions observable in the manufactured slabs (as an intermediate product) with a direct impact on the transformation during hot rolling of final products (inconsistent hardening, repair, recrystallization).
Based on chemical analysis of nickel-rich alloys during industrial production we calculated the equilibrium solidification flow and developed the necessary equilibrium phase diagrams with a commercial program for simulating thermodynamic equilibrium solidification (Thermo-Calc). We also analyzed the alloy samples by simple thermal analysis (ETA) by recording the cooling curves and deriving the characteristic solidification points from the obtained data. With the method of differential thermal analysis (DTA) we confirmed the course of melting and solidification and thus determined the temperature interval of solidification. The microstructure of the sample was analyzed using OM analysis.
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