CRYSTALLIZATION BEHAVIOR OF LI2O-SIO2, NA 2O-SIO2 AND NA2O-CAO-SIO2 GLASSES

It has been known that crystallization of mold powder is effective on the disturbance of heat transfer between mold and solidified shell in production of middle carbon steel slabs in continuous casting process. But it has not yet been made clear which composition of mold powder i s the most suitable for crystallization. The crystallization behavior of Li2O-SiO2, Na2O-SiO2 and Na2O-CaO-SiO2 glasses was observed by diff erential thermal analysis(DTA) and hot-thermocouple methods with DTA i n the present work. As a result, addition of alkaline metal and alkali ne earth metal oxides to SiO2 increased the critical cooling rate for glass formation in binary system of Li2O-SiO2 and Na2O-SiO2 ,and Li2O- SiO2 system crystallized easier than Na2O-SiO2 system. In ternary syst em of Na2O-CaO-SiO2, addition of Na2O hurried the critical cooling rat e at CaO/SiO2 = 0.93 mass ratio, but the rate was almost constant in t he composition range of more than 15 mass% Na2O. The slag of CaO/SiO2 = 0.93 made the rate faster than the slag of CaO/SiO2 = 0.47 at consta nt content of 10mass% Na2O.