Melting and Solidification Studies by Advanced Thermal Analysis of Cast Iron
A tool widely employed in foundry is measuring the melt temperature during free cooling in cups. Thermal analysis curves provide information on liquidus, eutectic, solidus temperatures and recalescence effects. More advanced analyses can be performed in the laboratory using differential devices where a temperature program is imposed to both the sample and an inert reference. The sensitivity in the detection of temperature points is enhanced and quantitative determination of the heat release during solidification, and therefore of the solid fraction, becomes feasible.
In this work we have employed a high temperature differential scanning calorimeter (Setaram HTDSC) capable of reaching temperatures up to 1600 °C to follow melting and solidification of master alloys for the production of lamellar, compact graphite and spheroidal cast irons, at various heating and cooling rates under protective helium atmosphere. Binary Fe-C alloys prepared in the laboratory with composition of 4.3 wt% C were analysed as well. The solid fraction as a function of temperature is obtained by integration of the DSC traces. The correlation between thermal data obtained by HTDSC, free cooling in cups and microstructure is shown.