Crystallization Behavior of Quarternary Mold Slag Using the Single Hot Thermocouple Technique

The crystallization behavior of CaO-SiO2-CaF2-Na2O quarternary slag was investigated by visual observation using the single hot thermocouple technique (SHTT). The influence of basicity R (1.0 similar to 1.7), F- (3 similar to 11 mass%) and Na2O (3 similar to 11 mass%) on the critical cooling rate and incubation time has been measured in the study. The results indicate that i) with basicity or the content of F increasing, mold slags have larger critical cooling rate and shorter incubation time to have stronger crystallization tendency. ii) When basicity reaches 1.5 or the content of F- is 10 mass%, the critical cooling rate and incubation time of the two samples are respectively 20 degrees C/s (20s) and 22 degrees C/s (25s) to achieve the above requirements of crystallization properties of mold slags controlling heat transfer in continuous casting. iii)As the content of Na2O increases, the critical cooling rate and beginning time of crystallization of samples reduce. But when the content of Na2O reaches 8mass%, the incubation time of mold slag has a trend to increase. iv)It's possible for crack sensitive steels that the basicity, F- and Na2O in CaO-SiO2-CaF2-Na2O quartary slag system are respectively up to 1.5, 10mass% and less than 8mass%.