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.
SynopsisManganese distribution between liquid iron and Mg0-saturated Ca0-FetO-Si02 Mn0 slaps containing P205 or S has been obtained in the temperature range 1 550 to 1 650 °G by use of magnesia crucibles. The manganese distribution ratio was found to increase with increase in Si02 content and decrease in temperature. The good relationship between activity coefficient of Mn0 or equilibrium quotient kMn (= (%Mn0)/ { [%Mn]. (%Fet0)
Lime particles (0.5 to 1 mm) were added by dropping to CaO-Fe t O-P 2 O 5 slag at 1 400°C, followed by stirring and the reaction products near a CaO particle/slag interface were determined by a microprobe analysis (EPMA-EDX). The 3CaO · P 2 O 5 and 4CaO · P 2 O 5 phases were crystallized depending on the amount of added CaO particles which are rapidly dissolved after the contact with a molten slag. The phosphorous distribution ratios between calcium phosphates and CaO-Fe t O slag obtained at temperatures between 1 400 and 1 570°C are higher than those between 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution and CaO-SiO 2 -Fe t O slag. Lime particles (0.3 to 0.5 mm) are added to CaO-SiO 2 -Fe t O-P 2 O 5 slag at 1 400°C and the reaction products near a CaO particle/slag interface are determined by EPMA-EDX. The 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution layer is formed on the surface of a CaO particle and thereafter the CaO-Fe t O slag layer is formed between a CaO particle and 2CaO · SiO 2 -3CaO · P 2 O 5 solid solution layer which is surrounded by CaO-SiO 2 -Fe t O-P 2 O 5 slag. It is also experimentally confirmed that the meso-phase slag refining is superior to conventional slag refining and the discrepancy between the theoretical and experimental results obtained by the meso-phase slag refining is discussed.KEY WORDS: phosphorous distribution ratio; lime; calcium phosphate; dicalcium silicate.again and heated at 1 600°C for 24 h, followed by He quenching.CaO-Fe t O and CaO-Fe t O-P 2 O 5 slags: The CaO powder produced by the aforementioned method, reagent grade Fe t O and 3CaO · P 2 O 5 were well mixed and the mixture was melted at 1 420°C under Ar flowing atmosphere in an Fe crucible, followed by stirring with an Fe rod. The melt was quenched by using a water-cooled sandwich type Cu plates. The present slag compositions D1 and D2 are plotted in the CaO-Fe t O-P 2 O 5 phase diagram 8,9) shown in Fig. 1. The slag samples were ground to below 3 mm by a stainless steel ball mill. ProcedureThe CaO-Fe t O-P 2 O 5 or CaO-Fe t O slag was melted at 1 400°C in an Fe crucible under Ar flowing atmosphere (200 cm 3 · min Ϫ1) and then CaO (0.5 to 1 mm) or calcium phosphate (20 to 50 mm) particles were added by dropping into a molten slag, followed by stirring with an Fe rod. A melt was quenched by using a water-cooled sandwich type Cu plates. In the experiments carried out at temperatures above 1 500°C, a MgO crucible containing Fe was used in stead of an Fe crucible. This procedure denotes the isothermal method.In the experiments where calcium phosphate phase is crystallized during cooling, the CaO-Fe t O-5mass%P 2 O 5 slag D3 (mp 1 560°C) shown in Fig. 1 was melted at 1 600°C under Ar flowing atmosphere in a MgO crucible containing Fe. The melt was cooled to 1 570°C at 0.83°C · min Ϫ1 and held for 30 min. Then, it was cooled at 2.5°C · min Ϫ1 from 1 570 to 1 400°C, followed by quenching in water. For comparison a melt was cooled from 1 600 to 1 570°C at 0.83°C · min Ϫ1 and quenched in water after holding for 30 min at 1 570...
SynopsisExperiments have been made to study the phosphorus distribution between liquid iron and Mg0 saturated Ca0-Mg0-Fe0x-Si02 slags containing 1 to 4 % CaF2 in the temperature range 1 550 to 1 650 °C. The effect of CaF2 on the equilibrium quotient k5(= (%P205) f ([%P]2(%FeO)5}) was found to be nearly equal to that of Ca0 on the weight percentage base. The equilibrium quotient kp is expressed as The effect of CaF2 on the activity coefficient o f P205 was also studied by the Turkdogan and Pearson's treatment. The following expression for the activity coefficient of P205 is given for the slaps containing CaF2.log TP2o5 = -1.01(23NCao+21NcaF2+l7WMgo+BNFeo) -26300/T+ 11.24It was found from the plot of the activity coefficient of FeO vs. the mole fraction of Si02 that the activity of FeO increases with the addition of CaF2. I. IntroductionThe beneficial effect of fluorspar addition to steelmaking slags has been traditionally recognized. Laboratory and plant scale investigations on fluorspar substitutes have been made on account of the short supply and rising cost of metallurgical fluorspar as well as the environmental problem. The addition of fluorspar to steelmaking slags increases the degree of dephosphorization and desulfurization; it is not clear, however, whether fluorspar affects the slag-metal equilibrium ratios, or whether it simply causes the increase of the fluidity of slags and, consequently, faster approach to the equilibrium. The fundamental study on the influence of CaF2 on the phosphorus partitions between slaps and metal has been first made by Winkler and Chipman,1 who have reported the partitions between liquid iron and Mg0 saturated Ca0--Mg0-FeOx Si02-P205 slags with 4 to 18 % CaF2 in the temperature range of 1 530 to 1 640 °C. The contents of P205 in the slags are between 6 wt% and 19 wt%. Their conclusion is that the addition of fluorspar have no adverse effect on the dephosphorizing power of the slag. However, the small number of melts (7 melts) investigated by Winkler and Chipman have not allowed the quantitative deductions for the exact effect of CaF2 on the slag-metal equilibrium. The further systematic works are necessary to the de-
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