材料期刊网

This present paper focused on the formation reasons of solidified crust when a basic tundish flux was used to cast the Al-killed steel. Crust samples were taken in an actual tundish, and analyzed by the methods of XRD, SEM and EDX. It was found that the main compositions of crystallization phases existing in tundish crust are Ca12Al4O33, Ca2SiO4 and a little spinel. Spinel and Ca2SiO4 distributed at grain boundaries of Ca12Al4O33, which increased the connection strength of crystallization phases by pinning the grain boundary, density or hardness of tundish crust will also significantly increased. When an initial composition of tundish flux was in spinel region of CaO-SiO2-Al2O3-10%MgO phase diagram, it was easier to form spinel in crust. Three approaches for spinel formation in crust were summarized. When flux is nearly saturated with magnesia, on the metal/flux interface, MgO in flux reduced by dissolved Al and formed the spinel. Inside molten steel and on the interface of steel/refractory, with a feasible Al content it is also easy to form spinel and spinel inclusions will float and captured by flux.