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The rate of dephosphorization of liquid iron-carbon alloys by FeO-CaO-SiO2 slaps and the effect o f NaCl or CaCl2 added to the slaps on the reaction rate have been investigated on a laboratory scale at temperatures of 1300-1460°C. The results show that the rate and degree of dephosphorization increase by the addition of NaCl or CaCl2 to the slag. But the degree of dephosphorization decreases with increasing temperature.It is found that the rate of dephosphorization of iron-carbon melt can be explained by the modified mass transfer controlled model in which mass transfer of iron and phosphorus across the slag-metal interface is controlled by diffusion while the evolution of CO gas is the chemical reaction controlled.

Cylinders of burnt dolomite with the apparent porosities of 20 to 35% were immersed into molten FetO-CaO-SiO2 slags at temperatures of 1350 to 1425°C and rotated at 100 to 400rpm. The dissolution rates were determined by measuring the decrease in radius of cylinder.The dissolution rate increased with increases in temperature and revolutional speed of cylinder, but was not affected by the difference in apparent porosity of burnt dolomite. From the analysis of experimental results, it was concluded that the dissolution rate was controlled by the mass transport of CaO in burnt dolomite for low FetO slag (slag A) and that of MgO for other slags in the boundary layer of molten slag. Mass transport coefficients calculated were in the range of 4.7×10-4 to 1.7×10-3cm/s at 1400°C.It was found that the burnt dolomite after the experiment was widely covered with (Fe, Mg) O solid solution in the case of high FetO slag.

Dephosphorization of liquid iron by CaF2-base fluxes was studied at 1600°C. Iron oxide was added to metal or flux as the oxidizing agent. Dephosphorizing reaction proceeded rapidly and the rate increased with increasing CaF2 content of flux. The rate of reaction was analyzed on the assumption that the reaction was controlled by the simultaneous transport of phosphorus, oxygen and sulfur.The effect of CaF2 on the distribution ratio of phosphorus between liquid iron and flux was examined.