| Mould fluxes is a very important and critical material during continuous casting of steel, and takes a key role to improve quality of strands. In continuous casting of steel, mould fluxes infiltrates between strand and mould , forms a film consisting of solid layer, predominantly glassy, (typically 1-2mm thick) and a liquid layer(ca. 0.1 mm thick) next to the strand. Sometimes, the solid glassy layer crystallizes partially. The heat transfer from the shell to the mould is controlled by the properties of the solid flux film and the lubrication supplied by the flux film is determined by the thickness of the liquid layer.An increase in crystallization of mould fluxes, which is a usual way to minimize surface defects especially for medium-carbon (MC) peritectic steel grades, may deuce the radiation conduction in glass and the lattice conduction in crystal. But it will bring deterioration between strand and mould. Thus the control of crystallization within a mould fluxes is a key parameter.Based on the research that the reduction of radiation conduct when the transition metal oxides are added to the mould fluxes, the paper, which is surported by the project"Study on the formed Mechanism of Mold Fluxex film with low infrared Radiation properties"(serial number:50474024 ) from national natural science foundation of china and the project"Study on Effect of Transitin Metal Oxides on Crystallization and low infrared Transmition of Mould Fluxes"(serial number: 2006BB4200) from national natural science foundation of chongqing, put the research on the mechanism that how the transition metal oxides adjust and control the crystallization of mould fluxes and the rule that the transition metal oxides influence the crystallization temperature, crystallization ratio, mineralogical phase and the crystal growth rate. The research offer a reference to design the mold fluxes for the MC steel grade. The TTT curves, CCT curves, the crystal growth curve and the direct observation on crystallization process bring a good way to simulate the crystallization behavior of mold fluxes which has not been observed directly in the mould. The conclusions were as follows:①The experiments give a certification that the mould fluxes is crystallizable in isothermal and continuous cooling process at high temperature and the first crystallographic axis and crystallographic axis are observed during the crystallization process. Temperature and degree of supercooling are key parameter to affect crystals'size and pattern.②Addition of MnO and TiO2 were founded to inhibit the crystallization ability of mould fluxes. MnO=0～2%,the crystallization temperature increasing, MnO=2～4%, the crystallization temperature decreasing, MnO=4～8 % , the crystallization temperature decreasing sharply. The addition of MnO cause a reduction of crystallization ratio and the mineralogical phase of mould fluxes is Ca4Si2O7F2, CaMnSi2O6, NaMnSi2O6, Mn2SiO4. The addition of TiO2 has a negative effect on the crystallization temperature and crystallization ratio in the base sample of low basicity. But, the addition of TiO2 has a positive effect on the crystallization temperature in the base sample of high basicity. The mineralogical phase of mould fluxes contented is Ca4Si2O7F2, Ca2SiO4, Ca2Al(AlSi7O7) and CaTiO3.③In the paper's research, the cooling rate have a negative effect to the temperature of mould fluxes contented TiO2.and the cooling rate have a complex effect to the temperature of mould fluxes contented MnO.④The TTT curves, CCT curves, the crystal growth curve are achieved. The active energy are increased with the addition of TiO2 and MnO in the base sample.⑤The melting temperature, viscosity, break-temperature all decrease with the increasing of MnO. Additions of ZnO, NiO, TiO2 have a negative effect on viscosity and break-temperature, but a little positive effect on melting temperature.
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