1997 TMS Annual Meeting: Tuesday Abstracts

MATERIALS PROCESSING FUNDAMENTALS: Session I

Session Chairpersons: M.E. Schlesinger, Department of Metallurgical Engineering, University of Missouri-Rolla, 1870 Miner Circle, Rolla, MO 65409-0340; Dr. S. Wang, ASARCO Inc., Technical Services Center, 3422 South 700 West, Salt Lake City, UT 84119

8:30 am

SULFIDE CAPACITY OF FeO-BASED SLAGS: R.G. Reddy, W. Zhao, Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487

Sulfide capacities of FeO-based silicate slags were calculated a priori using the Reddy-Blander model. Experiments were done using encapsulation method for several slag systems as a function of compositions and temperatures. The experimental results agree with the predicted data very well. The predicted sulfide capacity data was used in calculation of the sulfur distribution ratio in the slags and metal.

8:55 am

SULFIDE CAPACITY OF SLAGS: R. Sridhar, S. Simeonov, J.M. Toguri, Department of Metallurgy and Materials Science, University of Toronto, Toronto, Ontario, Canada, M5S 3E4

During the experimental studies on sulfide capacities of non-ferrous metallurgical slags it was found that the choice of the thermodynamic data base is important for calculating the sulfur potential in such measurement. It was also found that some of the earlier sulfide capacity measurements required recalculation. The available sulfide capacity for different slag systems were reviewed after recalculations. This analysis suggested high sulfur solubility in halide melts which were confirmed by experiments reported in another paper. The reviewed data on sulfide capacities are presented together with calculations of sulfur partition achievable with different slags.

9:20 am

SULFUR SOLUBILITY IN CaCl2-CaF2 and BaF2-BaCl2 MELTS: S. Simeonov, R. Sridhar, J.M. Toguri, Department of Metallurgy and Materials Science, University of Toronto, Toronto, Ontario, Canada M5S 3E4.

CaF2 additions are made to oxide based slags used for steel desulfurization to aid in sulfur removal. It is commonly held that CaF2 by itself does not possess sulfur removal capability but enhances fluidity of CaO based slags which helps desulfurization. Recently BaF2 additions to CaO and BaO based slags have been studied to improve their sulfide capacity. To better understand the sulfur removal mechanism, sulfur solubility measurements were carried out on CaCl2-CaF2 and BaCl2-BaF2 melts. Results showed that contrary to earlier expectation they have high sulfur solubility and higher than that for sodium silicate slags which are used for desulfurization. The conventional sulfide capacity definition based on exchange of oxygen and sulfur ions in slag used for defining desulfurization power of slags do not apply to such melts as there are no oxygen ions present and no oxygen ion transfer takes place.

9:45 am

ASPECTS OF SLAG OPTIMIZATION IN SMELTING OF Cu-Ni SULFIDE CONCENTRATES: A.A. Hejja, R.H. Eric, School of Process and Materials Engineering, University of the Witwatersrand, Johannesburg, Private Bag 3, WITS 2050, South Africa

The first part of this study deals with the importance of surface tension of slags produced in the smelting of sulfide concentrates. Theoretically the method of determining the surface tension of slags was laid down by Boni and Derge. The values obtained experimentally for a series of main oxide components were grouped into a useful correlation incorporating experimental constants for the relevant oxides present in the slag, some of these giving the surface tension value for the particular slag. These estimated values were coupled with or incorporated into the slag viscosity plots to show the correlation between the two factors. This is also important from a refractory attack point of view in the furnace operation. In the second part an attempt is made toward the optimization of slag composition relevant both for electric and reverberatory smelting processes. Using the knowledge of the viscosity and electrical conductivity of the slags at the temperature of furnace operation, the mode of optimization is based on Besselt function correlations which utilize the trend of the mostly parabolic plots of viscosities and conductivities. The results obtained by this method agree well with the optimum slag compositions being used in established operations derived from years of practical experience for various slags used in the furnaces. However, due to extensive turbulence in suspension and gas injected bath smelting processes, the outlined methods cannot be used for these processes. Also great caution should be exercised in their application for three electrode circular furnaces with separate slag cleaning.

10:10 am BREAK

10:20 am

SOLUBILITY OF BISMUTH AND LEAD IN IRON AND IRON-CARBON ALLOYS: Lewen Chang, Sandeep Malhotra, Mark E. Schlesinger, Department of Metallurgical Engineering, University of Missouri-Rolla, 1870 Miner Circle, Rolla, MO 65409-0340

The thermodynamic properties of Fe-C-Bi and Fe-C-Pb alloys are of interest for a variety of reasons related to steel production and recycling; however, experimental data on phase equilibria in these systems are scarcer. Experimental procedures will be described for an ongoing research program measuring the activities of Bi and Pb in solid and liquid Fe and Fe-C alloys. Preliminary results will be presented, with the primary goal of using measured solubilities to derive model parameters for calculating bismuth and lead activities as a function of temperature and alloy composition.

10:45 am

THERMODYNAMICAL INVESTIGATIONS OF METALLURGICAL AND MATERIALS PROCESSES AND PHENOMENA: Vladimir Mindin, AFP, 111 East Shore Road, Manhasset, NY 11030; Yakov Mindin, Polytechnic University, Six MetroTech Center, Brooklyn, NY 11201

The report presents results of thermodynamical investigation of wide range of complex systems, including carbo thermal reduction of silica, silicon carbide obtaining from different precursors, anode processes during molten salts electrolysis, tin atomization in AAS, interaction in copper-, manganese- and sulfur- containing systems. Special attention is paid to thermodynamical approach to investigation and estimation of multi component multi element compositions stability. Environmental topic in the report is presented by discussion of two important issues: (a) problem of radioactive wastes interaction -with environment, and (b) investigation on thermodynamic stability of exhaust from different sources. Also are discussed very important problems of informational support (thermodynamics data accuracy) of complex systems thermodynamics simulation.

11:10 am

OXYSULPHIDE IN METALLURGY OF NICKEL AND COBALT: I.D. Reznik, A.V. Tarasov, T.A. Kharlakova, State Research Institute of Non-Ferrous Metals, Acad. Korolyov Street, 13, Moscow, Russia, 129515; E.N. Selivanov, Institute of Metallurgy of the Ural's Branch of the Russian Academy of Sciences, 101 Amundsen Street, Ekaterinburg, Russia, 620147

On blowing nickel matte in a converter without quarts, first the oxidation of metallic iron and a part of FeS occurs without evolving sulfur dioxide, the formed FeO dissolves in a sulfide smelt and form a homogeneous Oxysulphide smelt. On further increasing the FeO content, the Oxysulphide separates into 2 layers. Based on the laboratory investigation of FeO-(FeS+Feo) - (Ni3S2+Nio) ternary phase we have identified the separation region at 1250°C. The boundaries of the separation region have the form of an arc and the composition of the separated Oxysulphide layers is defined by the canodes. In the nickel or copper-nickel matte - calcium oxidesilica slag system at 1250°C three layers, namely sulfide, Oxysulphide, and slag may be formed. A high slag basicity due to the presence of CaO can serve to enhance the activity of FeO; a low nickel content in the matte corresponds to a high concentration of FeS therein; FeO from slag and FeS from the matte form a homogeneous FeO-FeS solution, i.e. an Oxysulphide layer. The investigation on the "Camebakes" apparatus and by the nuclear gamma-ray resonance spectroscopy method of the phase composition in a slowly cooled Oxysulphide layer has shown the presence of four phases. wustite, troilite, ferronickel grains, and calcium oxide-silica inclusions. Knowledge of regulaties in the oxysulphides formation makes it possible to use them in pyrometallurgy of nickel and cobalt or preventing their formation.