Abstract: Viscosity stability indexes of mold flux at high temperature and low temperature have been introduced, and the effects of flux compositions on viscosity stability indexes have been studied. Two mold fluxes have been developed by analyzing the effects of flux viscosity stability on the process and the condition of continuous casting slab of medium carbon steel. The results show that the fluxes are suitable for the process.

Key words: mold flux, viscosity stability index, high temperature,