Effect of slag composition on the crystallization of synthetic CaO-SiO2-Al2O3-MgO slags: Part II- Measurement and prediction of critical cooling rate

• The Rc obtained from CCT diagram results are lower than those from TTT diagrams which agrees with the fact that TTT diagrams present an overestimation of transformation rate when slag is cooled continuously.
• The correlation between the optical basicity (Λcorr) and Rc is stronger than NBO/T with Rc.
• The critical cooling rate is inversely proportional to the viscosity.
• A correlation was developed based on theories of nucleation and growth during slag crystallization to allow prediction of the critical cooling rate using only two parameters: liquidus temperature (TL) and viscosity at nose temperature (ηnose) : Rc = 1.23 × 10− 5 (TL2/ηnose)

In this study, the critical cooling rate (RC) of CaO-SiO2-Al2O3-MgO slag samples are determined using time-temperature-transformation (TTT) and continuous cooling transformation (CCT) diagrams, obtained using the hot thermocouple technique. The relationships between RC and slag composition, and slag viscosity are investigated. It is shown that a theoretical treatment of nucleation and growth rates of slag crystals leads to the following correlation that can be employed to predict the RC from the liquidus temperature (TL)and slag viscosity at the nose temperature (ηnose) of the TTT diagram.Rc=1.23×10−5TL2/ηnose