Phosphorus removal in basic oxygen steelmaking is a significant problem for integrated steelmakers. Phosphorus removal is required due to its deleterious effect on the mechanical properties of steel. However, this is progressively becoming more difficult due to the increasing phosphorus content of many iron ores. Many studies have investigated dephosphorisation and published empirical phosphorus partition (L P ) equations for a range of conditions. The structure of these equations has been used to develop a new partition relation that allows the effect of minor slag constituents such as TiO 2 , Al 2 O 3 and V 2 O 5 on steel dephosphorisation to be tested. Al 2 O 3 was found to have a weak negative effect on the measured L P , except at the lower oxygen potential range tested, where a positive correlation was observed. Increasing TiO 2 and V 2 O 5 contents were found to decrease the measured L P ; however, these correlations became less prevalent at the higher oxygen potential ranges tested. AbstractPhosphorus removal in basic oxygen steelmaking (BOS) is a significant problem for integrated steelmakers. Phosphorus removal is required due to its deleterious effect on the mechanical properties of steel. However, this is progressively becoming more difficult due to the increasing phosphorus content of many iron ores.Many studies have investigated dephosphorisation and published empirical phosphorus partition (L P ) equations for a range of conditions. The structure of these equations have been used to develop a new partition relation that allows the effect of minor slag constituents such as TiO 2 , Al 2 O 3 and V 2 O 5 on steel dephosphorisation to be tested. Al 2 O 3 was found to have a weak negative effect on the measured L P , except at the lower oxygen potential range tested, where a positive correlation was observed. Increasing TiO 2 and V 2 O 5 contents were found to decrease the measured L P , however these correlations became less prevalent at the higher oxygen potential ranges tested. Definitions and Nomenclature( ) = in slag solution [ ] = in liquid iron solution %i = mass % of i (%Fe t ) = mass% of total Fe in slag phase (%Fe t O) = mass% of total Fe in slag phase as FeO M i = molecular weight of oxide i R = universal gas constant, 8.314 JK -1 mol -1 N = mole fraction of oxide or ion = L P calculated by model � = L P calculated by linear regression line through results to the origin = optical basicity of slag Λ i = optical basicity of single oxide of species i T = Temperature in K 4

The phosphorus partition (L P) and phosphate capacity C PO4 3 were measured for slags in the CaO-SiO 2-MgO-Fe t O-(MnO-Al 2 O 3-TiO 2-P 2 O 5) system over temperatures representative of basic oxygen steelmaking. The measured L P values were found to be in good agreement with those predicted from the model of Assis et al. The oxygen potential of the slag-metal systems studied was also evaluated and used in combination with the measured L P to calculate the C PO4 3− of the slags. Capacity values in the range of 7.77 × 10 16 to 4.27 × 10 19 for temperatures 1 550°C to 1 700°C were obtained. Correlations of C PO4 3− with common measures of slag basicity (v-ratio and optical basicity) were sought and reported. Consistent with other researchers it was found that the L P and C PO4 3− increased with increasing slag basicity and decreasing temperature.

The phosphorus partition (L P) and phosphate capacity (C PO4 3−) were measured for TiO 2 bearing basic oxygen steelmaking slags in the CaO-SiO 2-MgO-Fe t O-(TiO 2-MnO-Al 2 O 3-P 2 O 5) system at 1 650°C. The effect of slag and metal additions were tested by varying the TiO 2 content from 0.0 to 18.0 mass% and the [Ti] content from 0.009 to 0.301 mass%. A recently published L P model was used to assess the experimental L P data using the measured slag composition and temperature. Experimental L P data from this study and literature data were used to modify the published model to include titania. Increasing the TiO 2 concentration of the slag was found to decrease the L P and C PO4 3− of basic oxygen steelmaking (BOS) slags. Capacity values in the range of 2.2 × 10 16 to 1.5 × 10 18 at 1 650°C were obtained. An empirical model for determining C PO4 3− was developed for BOS slags using a large dataset of published slag and pO 2 data for relevant slag systems, including published data for titania bearing slags. The predicted C PO4 3− from the empirical model was found to agree with the experimentally determined C PO4 3− data from this study.

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Blast furnace hearth refractories are a key component in achieving long furnace lives. These refractories can be degraded by among other things reactions with coke ash products. Recent studies have shown that these coke ash products could be calcium aluminate based. To understand and characterize the effects of these calcium aluminates on hearth refractories a study has been carried out that investigates the reaction kinetics of CaO.Al2O3, CaO.2Al2O3 and CaO.6Al2O3 in contact with an aluminosilicate blast furnace hearth refractory. The experimental program covered the temperature range 1 450° to 1 550°C. The temperatures were chosen to represent the hot face temperatures of the hearth refractories. From this study it was found that the rate of reaction with the aluminosilicate refractory and CaO.6Al2O3 was much slower than that of CaO.Al2O3 and CaO.2Al2O3. The prevailing kinetics of the aluminosilicate refractory with CaO.Al2O3 and CaO.2Al2O3 was found to be consistent with the linear rate law. The slow rate of reaction of the refractory with CaO.6Al2O3 prohibited identification of the prevailing kinetic regime. In characterizing the reaction interface between the aluminosilicate and the calcium aluminates it was found that there was significant reaction between the refractory and CaO.Al2O3 and CaO.2Al2O3 but little reaction with the CaO.6Al2O3. The reaction layers formed at the interface between the couples were found to consist of CaO.2Al2O3, CaO.6Al2O3, corundum (Al2O3), plagioclase (CaO.Al2O3.2SiO2) and melilite (2CaO.Al2O3.SiO2). The formation of a layer with these phases could result in spalling/wear of the hearth refractory.