Detection Of Fluorine In Continuous Casting Mold Fluxes By Electrochemical Method

Calcium fluoride in the continuous casting mould flux play the role of reducing the melting point of slag casting, conducive to the protection slag melting, and lower the viscosity of the slag, and so as to improve the liquidity of liquid slag. In in the process of continuous casting, fluoride in mold slag will escape into the atmosphere and produce harmful fluoride compound for environment. , cause serious pollution to the environment.In this study, electrochemical method was utilized to determination of fluorine content in continuous casting mold fluxes. The determination of the conditions of the solution and the protection of slag sample decomposition conditions were discussed. The calomel electrode was used as reference electrode, and fluorine ion selective electrode was used to the determination of fluorine electrode potential.TISAB used in determination of fluorine ion was as follows: CDTA -potassium hydrogen phosphate-potassium di-hydrogen phosphate (pH5.8). The temperature was 30℃. When the concentration of fluorine ion in solution was in the range of 2x 10-4～4×10-3 mol/L, E and lgc· shown good linear correlation. The linear equation was y=-62.493x-51.89. The coefficient of correlation was R2=0.9978. The effect of decomposition for continuous casting mould flux sample in use of different fusion agent was examined. For 0.1 g mould flux sample, the best dosage of fusion agent was: 1.2 g Na2O2 + 0.6 g ZnO. The best range of sample melting temperature is 750°C～800°C. The hot water had a better effect for use of slag leaching determined by experiment. The recovery rate of fluoride in protecting slag samples after adding sodium fluorine were measured by standard addition method. When the amount of sodium fluoride added within the scope of 2%～8%, the recovery rate of fluorine was within the scope of 98.9%～103.3%, so the result was satisfied. Under the best conditions, 4 mould flux sample with scope of 2.27%～2.27% fluorine content were determined. Parallel sample measured value is consistent, which illustrates the feasibility of this method.