A new method for estimating the isothermal devitrification and crystallization of mold powder slags from non-isothermal DSC data

• Non-isothermal DSC tests allow characterizing slag crystallization behavior.
• Two isoconversional methods were used to formulate an isothermal kinetic model.
• The model predicts with good accuracy TTT diagrams of mold powder slags.

The rate of formation of crystalline phases from liquid and glassy mold powder slags is of foremost importance in the performance of molds used for continuous casting of steel. This study shows how the Induction Period (of Šimon and Kolman) and the Kissinger methods can be combined in a kinetic model to evaluate the isothermal rate of formation of crystalline phases from thermo-analytical data – onset temperature, Ti, peak maximum temperature, Tm, shape index, S, and conversion at peak maximum, xm – collected at various linear heating and cooling rates. The diagram of the extent of isothermal transformation as a function of time calculated for a commercial mold powder, used for casting low carbon steels, shows good agreement with the degree of transformation observed in photomicrographs of glass disks devitrified isothermally, at several temperatures for different times. Additionally, qualitative and quantitative X-ray diffraction results obtained at room-temperature from glass powder samples treated isothermally and quenched also show good accord with the degree of transformation predicted with the kinetic model developed in this work.

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