Metallurgical Problems Research Articles

Mineralogical Characterization and Hg Deportment in Field Samples from the Polymetallic Eskay Creek Deposit, British Columbia, Canada

Applied and process mineralogy in the mining industry is the application and utilization of mineralogical information. Mineralogy is used in understanding and solving problems during exploration and mining, processing of ores and related materials. It involves the characterization of minerals and materials and interpretation of data. Such an example is presented by a study of three composite field samples from the Eskay Creek Mine, British Columbia, Canada. Mineralogical techniques, including optical mineralogy, scanning electron microscopy, and electron microprobe analyses, coupled with chemical assays, are used to determine the textural features and the Hg distribution among the minerals and the samples. The contribution of accurate mineralogical information in such a study can assist in solving metallurgical problems and offer petrogenetic evidence with regards to the type, time and sequence of mineralization.

The Influence of Strain on Point Defect Dynamics

Stress migration of point and open-volume defects is an important problem in a wide variety of applications, ranging from semiconductor technology and basic metallurgical problems to ion implantation and surface modification. Often the driving force of the drift is the local stress field of other defects in the material, although other sources of residual stress as well as external loads play an important role. This paper concentrates on the behaviour of non-equilibrium vacancies in a non-uniformly strained material. Illustrative models of one-dimensional problems are developed and compared to available experimental results in different ion implanted materials.

Inclusion engineering: a keytool in achieving steelmaking operations stability at OneSteel Whyalla

A new billet casting machine and ladle metallurgy furnace were commissioned at OneSteel (formerly BHP) Whyalla steelworks in June and October of 1999. The production of low Mn/Si ratio grades using, at first, an oxygen reheating station, and then later a ladle metallurgy furnace, provided many challenges to the achievement of stable steelmaking and casting operations. The multiphase equilibrium model as developed by the Commonwealth Scientific Industrial Research Organisation (CSIRO) has been used to solve complex metallurgical problems of practical importance in the production of silicon killed steels. Subtle changes to ladle practice for dissolved oxygen content combined with calcium treatment dictates inclusion composition and liquidus. Inclusion composition control has been a key requirement for making open cast product with good surface quality, and also for the control of refractory stopper erosion for submerged cast grades.

A New Software to Evaluate Preheat Temperature and Cost

Preheating is a method for preventing hard structures and cold cracking in fusion welding of steels. Its application requires time and money, so that an evaluation of minimal preheat temperatures may be interesting. The thermal, metallurgical and economic problems of preheating were studied in order to acquire the most complete and logical as possible knowledge of the phenomenon thus defined. On this basis an easy and flexible instrument was developed. Parameters involved in the evaluation of the preheating temperature (chemical composition, hydrogen content, plate thickness, heat input, steel strength, restraint) were investigated. Available methods for determining the preheating temperature are briefly listed. An Uwer-modified formula was developed. A method for evaluating preheating costs is given. The developed software is presented.

RMS Titanic: A Metallurgical Problem

RMS Titanic: A Metallurgical Problem

RMS Titanic: A metallurgical problem

On 14 April 1912, at 11:40 p.m., Greenland Time, the Royal Mail Ship Titanic on its maiden voyage was proceeding westward at 21.5 knots (40 km/h) when the lookouts on the foremast sighted a massive iceberg estimated to have weighed between 150,000 to 300,000 tons at a distance of 500 m ahead. Immediately, the ship’s engines were reversed and the ship was turned to port (left) in an attempt to avoid the iceberg. In about 40 seconds, the ship struck the iceberg below the waterline on its starboard (right) side near the bow. The iceberg raked the hull of the ship for 100 m, destroying the integrity of the six forward watertight compartments. Within 2 h 40 min the RMS Titanic sank. Metallurgical examination and chemical analysis of the steel taken from the Titanic revealed important clues that allow an understanding of the severity of the damage inflicted on the hull. Although the steel was probably as good as was available at the time the ship was constructed, it was very inferior when compared with modern steel. The notch toughness showed a very low value (4 joules) for the steel at the water temperature (−2 °C) in the North Atlantic at the time of the accident.

Expert system shell for welding preheating: Technical and economic problems, as well as its impact on the physical environment ‐ part 3

Summary This article, published in three parts, is based on a doctoral thesis undertaken at the Department of Applied Mechanics and Engine Construction of Genoa University, in collaboration with the Italian Welding Institute. The aim of this article is to study the thermological, metallurgical, economic and safety problems of preheating which arise in fusion welding of steels and to acquire a basic knowledge of these phenomena, as fully and logically as possible. On this basis, a simple, flexible and expandable tool, illustrated by experiments, has been devised for use by expert welding engineers. For this purpose, state‐of‐the‐art research, national and international standards were studied, and experimental tests conducted to correlate available data. An expert system (ES) was thus produced, using artificial intelligence techniques, in order to determine preheat temperature, evaluate costs, and make health and safety recommendations to the user. In this third part, the development of the expert shell is described, as well as a brief software user's guide.

Metallurgical applications of AES: anisotropy of grain boundary segregation

Recent metallurgical application of methods of surface analysis on investigation of internal interfaces are discussed. The fundamental requirements necessary for such studies (fracture possibility, lateral and depth resolution, detection limit and possibility of depth profiling) are listed and compared to characteristics of Auger electron spectroscopy. A way of transformation of AES spectra of fracture surfaces to the chemical composition of grain boundaries is suggested. The adaptability of AES to solve current metallurgical problems is documented by studies of the temperature dependence of grain boundary composition in NiAl base intermetallics and of anisotropy of grain boundary segregation in Fe–Si alloy bicrystals. Copyright © 2000 John Wiley & Sons, Ltd.

Recent progress and future trend on grain-oriented silicon steel

Secondary recrystallization mechanism has rapidly progressed together with the advance in manufacturing process for grain-oriented silicon steel. The acquired inhibitor method was developed to avoid the metallurgical problem for controlling secondary recrystallization. As magnetic domain structure is affected largely by core loss, pinning of domain wall movement and surface closure domains must be removed to reduce core loss further.

Expert system shell for welding preheating: Technical and economic problems, as well as its impact on the physical environment (Part 2)

Summary This article, published in three parts, is based on a doctoral thesis undertaken at the Department of Applied Mechanics and Engine Construction of Genoa University in collaboration with the Italian Institute of Welding. The aim of this article is to study the thermological, metallurgical, economic and safety problems of preheating which arise in fusion welding of steels and to acquire a basic knowledge of these phenomena as fully and logically as possible. On this basis, a simple, flexible and expandable tool, illustrated by experiments, has been devised for use by expert welding engineers. For this purpose, state‐of‐the‐art research, national and international standards were studied and experimental tests conducted to correlate available data. An expert system was thus produced, using artificial intelligence techniques, in order to determine preheating temperature, evaluate costs, and make health and safety recommendations to the user. This second section considers the issues of economics, safety and the environment.

Metallurgical applications of AES: anisotropy of grain boundary segregation

Recent metallurgical application of methods of surface analysis on investigation of internal interfaces are discussed. The fundamental requirements necessary for such studies (fracture possibility, lateral and depth resolution, detection limit and possibility of depth profiling) are listed and compared to characteristics of Auger electron spectroscopy. A way of transformation of AES spectra of fracture surfaces to the chemical composition of grain boundaries is suggested. The adaptability of AES to solve current metallurgical problems is documented by studies of the temperature dependence of grain boundary composition in NiAl base intermetallics and of anisotropy of grain boundary segregation in Fe-Si alloy bicrystals.

Metallurgical problems associated with the production of aluminium-tin alloys

Of all the plain bearing alloys available, aluminium alloys have a better combination of ideal bearing characteristics than any other single material. Conventional Babbit alloys, especially the lead bronzes are increasingly being replaced by aluminium alloys, particularly in the automobile industry. It has been known, that the addition of elements, like tin or lead, improves the antiscoring and antifrictional properties of aluminium. Aluminium tin alloys have a wide miscibility gap in the molten state and are virtually insoluble in each other during solidification. Further difficulties arise from the large freezing range of the alloys, which together with the wide density difference between the two components greatly increase the tin segregation during alloy preparation. It has, therefore, been difficult to introduce and uniformly disperse tin in aluminium to the desired extent by conventional melting and casting techniques. The present authors have developed a simple foundry technique which has been used successfully to disperse and retain tin at contents up to 20 wt% in aluminium ingots, which is the subject of the present paper.

Metallurgical Technologies and Problems Related to Self-Disposal of Radioactive Waste by Deep Rock Melting

Radioactive waste arranged inside the container releases heat as a result of radioactive decay. If the heat power is sufficient, the geological rock near the container melts and the container moves into the Earth's depths. This method of self-immersion of radioactive waste may be suggested as an additional method to the deep geological disposal approach. The basic problem of method realization is to find a container material that remains firm in a temperature of about 1300–1400°C in melted rock (for example basalt). This problem is considered in connection with the question of radioactive matrix choice and compatibility of materials.

Recent developments in grain-oriented silicon-steel

The metallurgical problems associated with the manufacture of grain-oriented silicon-steel with high permeability was investigated using AIN as an inherent inhibitor. To avoid the metallurgical problems, the acquired inhibitor method was used. The characteristics of the new method and the new products which can be obtained using the one-stage cold rolling process with the use of AIN as the acquired inhibitor are described.

The blast furnace as a multifunctional device

1. In the twenty-first century, metallurgy will remain the basic branch of the world economy, but the conditions of its functioning will change substantially. On one hand, the exhaustion of resources of iron ores will lead to the predominant processing of compound polymetallic ores. On the other hand, the need for conserving resources will make the extraction of one basic metal with all others going to waste impossible. 2. Of all the known installations for obtaining primary metal, only the blast furnace can combine processing of compound ores with meeting stringent requirements on conserving resources and preserving the ecology. This objectively makes the blast furnace a leading metallurgical installation in the twenty-first century. 3. Calculations show that 20–30% of the reserved capacity of the blast furnace production in Russia can be used for processing technogenic waste and garbage. 4. In the twenty-first century, the blast furnace will become a multifunctional device, solving both metallurgical and sanitary-ecological problems. In the future, blast furnaces will be used for producing pure pig and cast irons, ferroalloys, polymetallic alloying compositions from compound ores and technogenic waste, slags of specified compositions and properties, gasification of solid fuel, and the processing of solid garbage.

Some recent advances in bulk growth of mercury cadmium telluride crystals

The inherent metallurgical problems associated with the HgTe/CdTe pseudobinary alloy system render the standard crystal growth processes inapplicable to the preparation of mercury cadmium telluride crystals for infrared detector applications. A variety of rather nonconventional techniques have been developed to overcome these problems. Two such techniques, viz. asymmetrical Bridgman and horizontal casting for solid-state recrystallization, developed at Solid State Physics Laboratory for the bulk growth of mercury cadmium telluride crystals are reviewed in this communication.Due to the poor thermal conductivity of mercury cadmium telluride melts and solids, and the use of thick-walled quartz ampuoles, it is extremely difficult to obtain a flat solid-liquid interface during Bridgman growth of this material. The technique of asymmetrical Bridgman has been successful in overcoming this problem to a great extent. Solid-state recrystallization has been widely accepted as one of the most successful techniques for obtaining large quantities of acceptable-quality mercury cadmium telluride crystals for infrared detector applications. This is a two-step process—the melt is first quenched to obtain a good cast, which is then subjected to a grain-growth annealing. The horizontal casting procedure developed for solid state recrystallization growth has been successful in improving the overall quality and yield of bulk mercury cadmium telluride crystals.

Processing and editing of kinetic data of substances for the data and program base system Kindas

On the basis of a Dbase system in the programming languages Fortran and Clipper, the data processing system Kindat has been created. With the aid of this system, approx. 120,000 kinetic data of substances have been compiled, approximated and annotated. These data are available to the metallurgical industry both in tabular form or as approximation formulae. Furthermore, the user can apply the Kindat system directly to solve metallurgical problems, or to process and manage own data.

Genetic adaptive search model of hot metal desulphurization

Genetic adaptive search (GAS) techniques, based on the mechanics of natural genetics, are used in this paper to find an optimal model of desulphurization process of iron‐melt by powder injection. Industrial data on 400 t torpedo are used to evaluate contributions of transitory and permanent contact reactions to the overall desulphurization process during calcium carbide powder injection. The results obtained with GAS agree more closely with the plant data than the theoretical model. GAS solutions are also found to be better than regression models. These results suggest immediate application of GAS in similar metallurgical problems.

Investigation of some selected metallurgical problems with the tomographic atom probe

The tomographic atom probe is a new instrument which enables a small volume of a metallic material to be reconstructed in 3D on a near-atomic scale. The basic principles on which the tomographic atom probe relies are briefly described. The performance of this new generation of apparatus is illustrated on the ground of some specific experiments. The intrinsic resolution of the spatial detector that was designed and developed is estimated. Several 3D atomic reconstructions of materials are provided. Images related to the investigation of precipitation processes in two-phase nickel-base superalloys, grain-boundary segregation effects as well as G-phase formation related to the spinodal decomposition of the ferrite in duplex stainless steels are given as illustrations. The quantitativity of composition measurements and the mass resolution of the instrument are discussed.

Metallurgical problems of joining composites to conventional structural materials

An important problem in using composite materials (CM) in practice is to join them together or with conventional structural materials. This problem is complicated as a result of the fact that it is necessary to join together materials with anisotropic mechanical properties with isotropic materials. To join these materials, it is necessary to select technology which guarantees: retention of the mechanical properties of composites (reinforcement fibres should not be disrupted or their properties should not be impaired by the effect of, for example, thermal energy used to produce the joint), minimum deformation of the joint material, especially in the joint area, retention or only a small increase of the mass of the structure. There are several technologies of joining composite materials to conventional materials. Generally, they can be divided into two groups: metallurgical joining methods (diffusion bonding, brazing, spot welding), mechanical joiniong methods (riveting, bolted joints, adhesion bonding, etc.) Lap types of joints are used in most cases.'The quality of the joint can be evaluated using the socalled bonding efficiency (BE) expressed by the relation: