Metallurgical Systems Research Articles

Thermodynamic Studies of Metallurgical Systems by Mass Spectrometry.

The application of the Knudsen cell-mass spectrometer technique to the thermodynamic studies of alloys and oxide melts which are called metallurgical slags is discussed in this review paper. Particular attention is paid to the development of such studies during the last twenty years.In conducting mass spectrometric studies on the composition dependency of properties of mixtures, a sereies of measurements with the samples of different compositions are necessary, and in these measurements small changes in the instrumental sensitivity between experiments is unavoidable. Various methods have been developed in order to overcome this problem. Many alloy systems have been studied employing ion intensity ratio methods. Analytical expression of thermodynamic functions have enabled to compute the thermodynamic functions from the mass spectrometric data more accurately. The experimental technique of multi-Knudsen cell has been improved, and pulse-counting technique was used for the measurement of ion intensity. The determination of the thermodynamic properties of the alloys containing the components of very low vapor pressure were performed. There are many difficulties in conducting mass spectrometric studies with oxide melts, but some of such systems have been studied by applying various techniques. The phase boundaries of some alloy systems were determined using the data of activities or using another technique. A complete listing of the applications to date is presented.

Role of EM in interface science and engineering

The world of materials is a world of interfaces. Indeed many technologically significant materials have properties both physical and mechanical which are determined by the structure, composition, and bonding of the interfaces within these materials. Thus, electron microscopy and microanalysis, with its high resolution and specificity of information, is one of the key methods needed for characterization. Imaging can be done by amplitude contrast but is limited by the factor g • R (where R is a displacement vector), or resolution in phase contrast, and in today's modern instruments atomic arrangements can be imaged directly, both in plan and cross-sectional views. Beautiful examples are now being published. However so far, few developments to utilize this information for materials design have been forthcoming. On the other hand, interface or intergranular phases are very important in many metallurgical and ceramic systems. In fact many materials are composites of one kind or another and composites involving intergranular phases are an important group of such materials.

The coming of age of process engineering in extractive metallurgy

The increasing importance of the application of process engineering principles and techniques in extractive metallurgy is reviewed. Significant developments made in recent years in quantitatively describing metallurgical processes are discussed. Some general approaches and building blocks of process engineering are presented, together with examples related to a number of unit operations and unit processes encountered in extractive metallurgy. A considerable amount of discussion is devoted to the advances made in the engineering analysis of rate processes in metallurgical processes. The importance of the interrelationship between transport phenomena and chemical reactions in metallurgical systems, which are almost always heterogeneous in nature, are emphasized

SGTE data for pure elements

Thermodynamic data for the condensed phases of 78 elements as currently used by SGTE (Scientific Group Thermodata Europe) are tabulated. SGTE is a consortium of seven organisations in Western Europe engaged in the compilation of a comprehensive, self consistent and authoritative thermochemical database for inorganic and metallurgical systems. The data are being published here in the hope that they will become widely adopted within the international community as a sound basis for the critical assessment of thermodynamic data, thereby, perhaps, limiting unnecessary duplication of effort. The data for each phase of each element considered aie presented as expressions showing, as a function of temperature, the variation of (a) G-H SER, the Gibbs energy relative to the enthalpy of the “Standard Element Reference” ie the reference phase for the element at 298.15 K and (b) the difference in Gibbs energy between each phase and this reference phase (ie lattice stability). The variation of the heat capacity of the various phases and the Gibbs energy difference between phases are also shown graphically. For certain elements the thermodynamic data have been assessed as a function of pressure as well as temperature. Where appropriate a temperature— pressure phase diagram is also shown. Throughout this paper the thermodynamic data are expressed in terms of J mol −1. The temperatures of transition between phases have been assessed to be consistent with the 1990 International Temperature Scale (ITS90).

Knowledge-based simulation and identification of various metallurgical reactors

A knowledge-based system (KBS) is discussed for the dynamic simulation and fault diagnosis of various metallurgical reactor systems. The fundamental basis (deep knowledge) of the model is a data base containing concentration-time data and an accompanying generalized kinetic model. The knowledge base is defined by various facts, objects, rules, and functions, which capture both deep as well as shallow knowledge regarding the process. This approach permits the simulation and fault diagnosis or identification of metallurgical reactors at all reactor conditions catered to by the knowledge base. Various examples, which include adsorption, leaching, and reduction (pyrometallurgical) reactions, illustrate the various facets of the proposed knowledgebased simulation (batch and continuous), process identification, and knowledge representation.

Superplasticity in an Ni3Al base alloy with 8wt% Cr

A maximum superplastic elongation of 638% has been obtained in a fine-grained Ni3Al-based intermetallic alloy containing 8wt% Cr. The extent of superplasticity obtained is dependent on the heat treatment given to the alloy, the test temperature and the strain rate. The activation energy of deformation and the value for the strain rate sensitivity parameter were comparable to those noted earlier in metallurgical alloy systems. There was some evidence that dynamic recrystallization plays a role in determining the extent of cavitation in the grain sized encountered here.

On The Nature of Multiple Orientation Relationships in Epitaxial Silicides

ABSTRACTThe Invariant Line Criteria (ILC) has been used to explain experimentally observed precipitation and epitaxial orientation relationships in a number of metallurgical systems. We propose that ILC may explain the crystallography of misoriented silicide grains in epitaxially grown silicide films. We test our hypothesis on the case of misoriented grains in CoSi2 on Si (001). Our analysis shows that the experimentally observed orientation relationship is predicted by the ILC.

Mixing with heat and mass transfer in metallurgical systems

In the first part of this paper, general aspects of research needs in the field of heat and mass transfer in metallurgical systems are discussed as this field is important for innovative iron and steelmaking processes. In the second part, special research needs are mentioned which have to be considered under the view of the first part.

Application of a model of regular solutions to ionic melts

The paper presents a review of applications of the model of regular solutions to ionic melts with regard to metallurgical slags. Various theoretical approaches to systems with a single common ion are discussed. A survey of experimentally determined interaction coefficients for basic metallurgical systems is given. Data for the model of regular solutions for arbitrary numbers of cations and anions are briefly discussed.

ENTHALPY-POROSITY TECHNIQUE FOR MODELING CONVECTION-DIFFUSION PHASE CHANGE: APPLICATION TO THE MELTING OF A PURE METAL

The melting of pure gallium in a rectangular cavity has been numerically investigated using the enthalpy-porosity approach for modeling combined convection-diffusion phase change. The major advantage of this technique is that it allows a fixed-grid solution of the coupled momentum and energy equations to be undertaken without resorting to variable transformations. In this work, a two-dimensional dynamic model is used and the influence of laminar natural-convection flow on the melting process is considered. Excellent agreement exists between the numerical predictions and experimental results available in the literature. The enthalpy-porosity approach has been found to converge rapidly, and is capable of producing accurate results for both the position and morphology of the melt front at different times with relatively modest computational requirements. These results may be taken to be a sound validation of this technique for modeling isothermal phase changes in metallurgical systems.

Pourbaix Diagram for The Prediction of Waste Glass Durability in Geologic Environments

AbstractDissolution of nuclear waste glass occurs by corrosion mechanisms similar to those of metallurgical and mineralogic systems albeit on different time scales. The effects of imposed pH and oxidation potential (Eh) conditions existing in natural environments on metals and minerals have been quantatively and phenomenologically described in compendiums of Pourbaix (pH-potential) diagrams. Construction of Pourbaix diagrams to quantify the response of nuclear waste glasses to repository specific pH and Eh conditions is demonstrated. The expected long-term effects of groundwater contact on the durability of nuclear waste glasses can then be unified.

Some fundamental aspects of mixing in metallurgical reaction systems

It is a well-established fact that mixing time (t m ) in ladle metallurgy systems may be related to the specific power input (P t ) by a relationship of the following form:t m = Const.P t −1/3. On the basis of arguments developed, using turbulence theory, it is shown that this relationship previously developed on an empirical basis does have a fundamental basis. The theoretical derivation given in the paper accounts for both the numerical values of the exponent and of the multiplying factor.

Ultrasonic system for the detection of transient liquid/gas interfaces using the pulse-echo technique

An ultrasonic method has been chosen to examine liquid/gas interfacial areas in closed systems. Although commercial equipment was used for the transducer and ultrasonic analyzer, commercial transient memory devices were inadequate. Consequently, a real-time data analysis and transient memory (DATM) unit was designed and constructed. A series of flight times for a succession of 1024 signals are calculated and recorded in the transient memory. The system clock operates at 10 MHz and increments a 12-bit binary counter. The counter is capable of measuring return signal times as long as 212 μs (4.096 ms) with a 1-μs resolution. The data are available as analog voltages for display on an oscilloscope or the digital data may be directly transferred to a microcomputer for analysis, display, or archival storage. The DATM device was successfully applied, collecting data for the analysis of rising bubbles in metallurgical systems and two-phase flow in horizontal tubes.

Eh measurements in sulphide mineral slurries

Problems in utilizing open-circuit potential (Eh) values as a measurement of the redox conditions in metallurgical systems are explored. Factors which determine the Eh when more than one redox couple is present have been illustrated by studies with platinum, gold and galena indicator electrodes in iron/oxygen and xanthate/oxygen systems. Potential measurements in galena slurries have demonstrated that smooth noble-metal electrodes are sensitive to the conditions at the mineral particle/solution interface.

The analysis and calculation of equilibria in complex metallurgical systems

The analysis of equilibrium and an iterative method of calculation of the equilibrium state in selected metallurgical systems are presented. The methods of matrix algebra are coupled with the chemical knowledge about the system to determine the number of independent reactions occurring at equilibrium. The role of the stoichiometric constraint in heterogeneous systems is delineated. The method of calculation of the equilibrium state in complex systems using high-speed digital computer is illustrated by two examples, namely, Al-C-O-Cl and Fe-C-O-H reaction systems at elevated temperatures.

Serial-layered-transmission line contact-resistance representation for partially-overlaid Al-to-contacts to silicon

We have developed a contact resistance representation for metallurgical systems having two interfacial conductive and resistive layers to a semiconductor surface. This configuration results when an interconnect metal (e.g. Al), which only partially overlays a contact metal (e.g. silicide), reacts with it to form a less conductive interface. As a consequence, circuit designers can take advantage of the unreacted region's lower contact resistance to ease circuit layout constraints. Contact resistance minima are suggested by the degree of overlaid or reacted segment and specific contact resistance degradation trade-off. A coupling of two layered transmission lines is used to simulate these two segment contacts. The model is compared to measurements of hardware.

Heat Transfer and Fluid Flow in Rotating Coolant Channels . By W. D. M ORRIS . Research Studies Press/Wiley, 1981. 228 pp. £13.00. Advances in Heat Transfer, Vol. 15 . Edited by J. P. H ARTNETT and T. F. I RVINE , Jr. Academic, 1982. pp. $54.00. Power Condenser Heat Transfer Technology . Edited by P. J. M ARTO and

Heat Transfer and Fluid Flow in Rotating Coolant Channels . By W. D. M ORRIS . Research Studies Press/Wiley, 1981. 228 pp. £13.00. Advances in Heat Transfer, Vol. 15 . Edited by J. P. H ARTNETT and T. F. I RVINE , Jr. Academic, 1982. pp. $54.00. Power Condenser Heat Transfer Technology . Edited by P. J. M ARTO and

Heat and Mass Transfer in Metallurgical Systems

Heat and Mass Transfer in Metallurgical Systems

Interfacial Hydrodynamics: An Over View

AbstractA fluid interface may promote spontaneous flow, or, particularly if laden with a surface-active agent, may act to suppress flow in its vicinity. In either event, the effect is the result of locally unbalanced forces at the interface. The resulting flows may be chaotic (interfacial turbulence) or orderly (cellular convection), steady, periodic or intermittent. They may significantly increase heat and mass transfer rates and alter contacting patterns in fluid-phase contacting equipment. Flow suppression due to surface-active agents may also assume a variety of forms and may significantly reduce transfer rates. These phenomena are classified, illustrated and rationalized in terms of hydrodynamic theory. Recent research developments and implications for metallurgical systems are given. Resume Une interface fluide peut generer un ecoulement spontane, ou, si elle est recouverte par un agent tensio-actif, supprimer cet ecoulement. Dans les deux cas, l'effet observe est du a des forces locales non equilib...

Cracking of weldments in pipes manufactured by ERW process: An analysis

Cracking of weldment in pipes manufactured by the ERW (electrical resistance welding) method has been examined based on the assumption that crack nucleation as well as propagation in a system must result in a decrease in the free energy of the system. Therefore the appearance of cracks is viewed in the light of decomposition phenomenon common in metallurgical systems. The tendency of cracking of ERW pipes is measured by the gradient of the energy profile of the weldment and it has been shown that the tendency of cracking can be measured by a parameter ‘ R’. Several ERW pipe samples showing both weldment cracks and no weldment cracks were examined and the parameter ‘ R’ determined. It was found that cracking of weldment occurred when ‘ R’ exceeded a value of 25. Further increase in the value of ‘ R’ resulted in increase in the severity of the cracks.