Mark E. Schlesinger

Refractories for Copper Production

Abstract The furnaces used for producing molten copper from concentrates and scrap - flash: smelters, converters, and anode and fire-refining furnaces - present a unique combination of challenges to refractory life. Highly aggressive slags, mechanical stresses, batch operation, and increasingly higher operating temperatures all combine to destroy most refractory materials. Over the past generation, copper producers have adopted refractory materials biased on the MgO-Cr2O3 system to meet these challenges, to the point where ‘mag-chrome’ brick is used almost exclusively in the industry. However, recent environmental imperatives have created a need to develop chrome-free alternative refractories for copper smelters, converters and refining furnaces. Some possible alternative materials are introduced, and speculation is made about the locations where they might be used most advantageously.

Determination of the kinetics of TiAl3 formation from fine Ti and Al particles using differential scanning calorimetry

Abstract Differential scanning calorimetry was applied to the study of high temperature kinetics of TiAl 3 formation from the constituent metal powders. The reaction proceeds at a measurable rate above the melting point of aluminum. The effects of various experimental parameters on the reaction kinetics were determined. The heating rate affects the exothermic reaction temperature. In the temperature range 690–740°C, the rate equation obeys the Prout-Tompkins equation and the activation energy and pre-exponential factor are 149 kJ mol −1 and 1.2×10 6 s −1 respectively. In the temperature range 750–900°C, the rate equation obeys a second-order rate equation with an activation energy of 517 kJ mol −1 and a pre-exponential factor of 1.9×10 23 s −1 . These kinetics parameters represent true intrinsic values because they are directly determined by eliminating any heat transfer effects.

The B-Nd (boron-neodymium) system

Given the scientific and commercial significance of the ternary Nd-Fe-B system, it is surprising that so little is known about the Nd-B binary phase diagram. Figure 1, the assessed Nd-B diagram, was constructed using contributions from a number of sources. The diagram is similar to that for the B-Sm system. Its phases include the liquid, L; the two stable neodymium allotropes, (txNd) and ([3Nd), each with negligible solid solubility ranges; four intermetallic phases assigned the stoichiometries Nd2B 5, NdB4, NdB6, and NdB66; and the terminal solid solution, (~B), with negligible solubility for Nd. The liquidus temperatures and invariant compositions are estimated, largely based on results f0r the B-Sm system [76Spe, 77Spe].

Effect of VB and VIB oxides on nucleation parameters in lithium disilicate glass

Abstract It has been proposed that some oxides act as nucleation agents in glass ceramics by reducing the interfacial tension between subcritical nuclei and the glass matrix. Evidence exists for classifying the Groups VB and VIB oxides in this type, which would support their behavior as homogeneous nucleation agents. However, substitution of MoO 3 , Nb 2 O 5 , Ta 2 O 5 , and WO 3 for silica in lithium disilicate glass was shown to cause decreased steady-state nucleation rates and increased induction periods at 733 K, while substitution of V 2 O 5 resulted in inconsequential changes. The effect of differential cooling rates through the glass cross section on crystal density following heat treatment was most apparent in those glasses containing the oxides that most retarded nucleation as a whole. The possible relationships between these effects and the effects of the substituted oxides on the physical properties of the glasses are analyzed; an especially significant link between viscosity and nucleation parameters is postulated.

Enthalpies of mixing in Fe–C–Si melts

Abstract The enthalpy of mixing of molten Fe–C–Si alloys is a significant element in performing mass balances on iron production and steelmaking, but almost no experimental data has been reported on enthalpy determination in these melts. As a result, models expressing this property as a function of composition must be derived from measurements of component activity, which are more widely available. The use of three such models – the regular solution model, Wagner’s model for dilute solutions, and the unified interaction parameter model developed by Bale and Pelton – have been used to calculate enthalpies of mixing in Fe–C–Si melts. The results are compared with each other and with the experimental data of Vitusevich et al.

Cathodoluminescence microscopy characterization of chrome-free refractories for copper smelting and converting furnaces

The results of an experimental program assessing the potential of several chrome‐free refractory materials as potential replacements for the mag‐chrome brick currently used in copper production furnaces are presented. Several commercial chrome‐free bricks were subjected to the standard dip test in a high‐copper calcium ferrite slag. The mineralogical changes in the bricks resulting from their interaction with the molten slag are described. The use of optical cathodoluminescence microscopy as an analytical tool is highlighted, along with reflected light microscopy and scanning electron microscopy–energy dispersive spectroscopy. Using the three tools together provides a description of the experimental results not achievable using one or two alone. The penetration resistance of the potential replacement refractories is comparable to that of mag‐chrome, but the substitution of Fe2+ for Mg2+ in the periclase and spinel crystalline structures of the replacements reduces their corrosion resistance compared with mag‐chrome, diminishing the likelihood that they will serve as reliable alternatives.

PbO Solubility in Lead-Blast Furnace Slags

AbstractA series of slags in the PbO-CaO-FeO-Fe2O3-SiO2 system has been equilibrated in contact with molten Pb and Pb-Ag alloys in a closed system at 1473 K. The influences of lead activity and the CaO/SiO2 and ferric/ferrous ion ratios on PbO solubility in slag have been examined. The PbO content is proportional to the lead activity and the ferric/ferrous ratio, but decreases with increasing values of the CaO/SiO2 ratio. The solubility of lead in the slag can also be characterized by the following empirical equation, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaieYlf9irVeeu0dXdh9vqqj-hEeeu0x% Xdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs% 0dXdbPYxe9vr0-vr0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaO% qaaiGacYgacaGGVbGaai4zaGqaaiaa-bcacaWFybWaaSbaaSqaaiaa% -bfacaWFIbGaa83taaqabaGccqGH9aqpdaWcaaqaaiaaigdaaeaaca% aIYaaaaiGacYgacaGGVbGaai4zaiaa-bcaieGacaGFWbWaaSbaaSqa% aiaa-9eadaWgaaadbaGaa8NmaaqabaaaleqaaOGaeyOeI0IaaGimai% aac6cacaaI3aGaaGOnaiaa+zeadaahaaWcbeqaaiaa+DeaaaGccqGH% RaWkcaaIWaGaaiOlaiaaigdacaaIWaGaciiBaiaac+gacaGGNbGaa4% Nraiaa-TcacaWFWaGaa8Nlaiaa-DdacaWF2aGaa83kaiaa-XgacaWF% VbGaa83zaiaa+TeadaWgaaWcbaGaa8NmaaqabaGccaGGSaaaaa!6054!

Thermodynamics of the iron-carbon-zinc system

\log X_{PbO} = \frac{1}{2}\log p_{O_2 } - 0.76F^G + 0.10\log F + 0.76 + logK_2 ,