SynopsisExperiments have been made to study the phosphorus distribution between liquid iron and the Ca0-Si02 FeOx slag equilibrated in a magnesia crucible in the temperature range 1550° to 1650°C.The phosphorus distribution ratio (P205)/[P] increased with increasing Ca0 content and decreasing temperature. The maximum value of the distribution ratio was found to be present near the slag composition saturated with the tricalcium silicate and the magnesio wustite phases. The experimentally determined phosphorus content in metal disagrees with the phosphorus contents estimated from the treatments proposed by Balajiva et al., Turkdogan and Pearson, and Hea y over the present range of slag compositions, except by Flood and Grjotheim.

The phosphorus distribution ratios between CaO-MgOsat .-FetO-Si02 P205(<3wt%)- MnO(2s5wt%) or CaO-MgOsat ,-FetO-Si02P205(4N5wt%) Slags and liquid iron have been obtained in the temperature range from 1 550 to 1 650 °C. The dephosphorization quotients can be expressed by the following three different equations. (i) log (P205)/([P]2(FetO)5) = 0.145[(%Ca0)+0.3(%Mg0) --0.5(%P205)+0.6(%Mn0)]+22 810/T-20 .506 (ii) log (P205)/([P]2(FetO)5) = 7.87 log [(%Ca0) +0.3(%Mg0) -0.05(%Fet0) -0.5(%P205) +0.6(%Mn0)]+22 240/T--27.124 (iii) log (P)/([P](T.Fe)5/2) = 0.0720[(%Ca0)+0.3(%Mg0) +0.6(%P205)+0.6(%Mn0)]+11570/T-10.520 The activity coefficient of P205 by Turkdogan and Pearson's treatment can be expressed as follows : log YP2o5 = -1.02(23Ncao+ 17NMgo+8NFeto -26N, 2o5 + 13NMno) -22 990/T+9.490In the plot of logarithms of activity coefficient of Fet0 against mole fraction of Si02, the values for log YFeto tend to increase with increase of the P205 content and with the addition of Mn0 in the range of X102<0.1.

shown in Fig. 1(b The iso-AI (massppm)Iines were calculated from Eq.(2) at C=0.8 and Si=0.3masso/o, by using the AGṽ alue, the activities of A1203(s) and Si02(s)18) and the respective interaction coefflcientsl'8) for fsi and fA~. The results are shown in Fig. 2(a).~T heiso-O (massppm)Iines can be calculated from Eq.

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