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By P. Chris Pistorius

Calcium treatment of alumina inclusions, to convert the alumina to molten or partially molten calcium aluminates, is a well-established treatment for steel, to improve the castability of aluminium-killed steel. However, the role of magnesium in calcium-treated steel is not fully clear, nor is the origin of the several percent of magnesium oxide that is often present in calcium-treated inclusions. To study this, steel was sampled after calcium treatment at an industrial steel plant, and the inclusions identified by energy-dispersive X-ray microanalysis (EDX) on polished sections of the samples (analysing the samples in a scanning electron microscope). The predicted fraction liquid in the inclusion was estimated from the ternary alumina-magnesia-lime phase diagram. Inclusions with higher CaO contents generally had lower MgO contents, indicating that the calcium wire is not the origin of the magnesium in the inclusions; this was also confirmed by wet chemical analysis of the calcium wire. Instead, it appears that magnesium-alumina spinel inclusions form during extended ladle contact after aluminium killing and before calcium treatment. While such spinels have been stated to cause poor castability (clogging the submerged-entry nozzle), it is clear that calcium treatment successfully modifies the spinel inclusions to mixed alumina-lime-magnesia inclusions, where the magnesia content contributes substantially to liquefaction of the inclusions: for typical MgO contents of around 10%, the range of Ca:O ratios which yield liquid (or partially liquid) inclusions is extended substantially to lower Ca:O ratios.

Jan 1, 2006

By N. El-Kaddah, V. L. Acoff, M. Arenas

"Control of the weld penetration, weld pool shape and temperature field in arc welding is critical to achieve the desired microstructure and mechanical properties in the resultant welds. This is particularly important in welding gamma titanium aluminides (y-TiAl) where the weld pool is relatively shallow and the temperature gradient in the heat-affected zone is quite steep. This paper investigates theoretically and experimentally the evolution of the shape of the weld pool for stationary gas tungsten arc welds in y-TiAl alloys. A mathematical model has been developed for predicting the electric current flow, the resultant electromagnetic forces in the metal, and the transient development of the temperature and velocity fields in the molten pool generated by a spatially variable heat flux at the arc-striking zone. The governing equations were solved numerically using the control volume technique. Welding experiments were carried out to determine the shape of the weld pool and the extent of the heat affected zone at different welding times for model validation. The numerical predictions were found to be in reasonable agreement with measurements. It is suggested that the model presented in this paper is likely to provide the information needed for predicting the microstructure and mechanical properties of y-TiAl welds. IntroductionIn recent years, there has been considerable interest in the welding of gamma titanium aluminides as a means of manufacturing high-temperature, high-performance components for turbine and automobile engines. These alloys are highly reactive, and must be welded in vacuum or inert gas atmosphere, rendering electron beam, and inert gas tungsten arc welding (GTA) to be the only suitable welding techniques for joining these materials [1-3]. The GTA welding is especially attractive because of its flexibility and relative cost-effectiveness. However, previous studies on the weldability and weld properties of these alloys using this process revealed a decrease in the mechanical properties in the fusion zone [4]. This is generally attributed to the change of the original duplex structure to a dendritic structure amplified by the shallowness of weld spot. Quantifying the effect of arc operating parameters on the geometry and temperature profile of the welding pool prior cooling is the first step for controlling the fusion zone microstructure and mechanical properties."

Jan 1, 1999

By J. D. Zhu, T. Ohmichi, H. Yasuda, S. Kashiwai, I. Ohnaka

"Since the casting process affects the properties of castings, its computer simulation has been greatly developed in the last decades. This paper presents our recent works, especially on mold filling simulation, because most casting defects such as porosities and inclusions that greatly affect the properties originate during mold filling. The first topic is the mold filling simulation with consideration of cavity pressure change during mold filling, including direct observation of flow phenomena with X-ray and pressure measurement. The second .one is the mold filling simulation in the lost foam process, in which gasification of polystyrene pattern and gas outflow through the coating and mold have been considered. The simulation can predict not only the mold filling sequences but also periodical vibration of the gas layer between the melt and pattern. The third one is the comparison of simulation of Al melt flow in a metallic runner and direct observation through a transparent mold, showing that the entrapped gas or inclusions is expelled ahead through the melt and its simulation needs very fine meshes. These examples show that the comparison of simulation and observation is very important to develop the numerical simulation further.IntroductionThe mechanical properties of castings are greatly affected by casting defects such as porosities and inclusions, and solidification structure. Although recently the structure simulation has greatly progressed [1-4 ], the application in plants is very limited, because the structure is mostly determined by chemical compositions and cooling rate, enabling us to estimate it from the structure of past similar castings without simulation.On the other hand, the casting defects often vary with each casting or time. Among the defects, porosities and inclusions are main causes to deteriorate the properties and mostly originate during mold filling. Therefore, a lot of efforts to simulate the mold filling and estimate those defects have been made in the last decades [l,5,6]. These efforts have been mostly to develop numerical techniques to solve the Navier-Stokes equation. However, the flow phenomena in molds have not been well understood, because the direct observation of the flow phenomena in mold is not easy. This means the accuracy of the simulation is still not clear."

Jan 1, 2000

By S. Malinov, J. J. McKeown, W. Sha, S. McShane

"A model is developed for prediction of fatigue stress life S-N diagrams for Ti-6Al-4V alloy at different conditions, using Artificial Neural Network (ANN). Different factors which have influence on the S-N diagram are involved as input parameters of the NN, namely microstructure, environment, texture, test/work temperature, surface treatment and stress amplitude. As the output the S-N fatigue diagram is simulated and plotted.The model is based on standard multilayer feedforward neural network. The NN is trained with a comprehensive data set collected from the literature, using Levenberg-Marquardt training algorithm in combination with Bayesian regularisation. A very good performance of the trained Neural Network is achieved. Good correspondence between ANN"" prediction and experimental S-N diagrams is observed. Using the model S-N diagrams for different conditions are predicted and analysed. Graphical User Interface is developed for use of the model. We believe that the model will be important for practical applications in solving various problems on fatigue behaviour of the titanium alloy.IntroductionTitanium and its alloys have an increasing range of applications due to their very good combination of mechanical properties, corrosion and erosion resistance. They are currently finding widespread applications in many industries due to their desirable and versatile properties. Most important among the alloys is Ti-6AI-4Y. Jet aircraft manufacturers are the principal 'consumers of Ti-6Al-4V and it is often specified for critical parts, the failure of which could result in the loss of an entire system. A generic class of Ti-6AI-4V has been developed over the past years and it has become the best understood of all the titanium alloys. The advantages of titanium alloys include: (i) low densities, giving very attractive strength to weight ratios allowing lighter and stronger structures; (ii) superior corrosion and erosion resistance in many environments; (iii) high temperature capability. Although the titanium materials are still considered as expensive materials, for many applications the cost of titanium alloys can be justified on the basis of their desirable properties."

Jan 1, 2001

By N. J. Rarmrez, C. Perez, J. D. Calderon, L. Lopez

"Among the thermal characterization of any material, one of the variables to know is the coefficient of thermal conductivity because this value can tell how much heat passes through the material and if the material could be used as an isolator. In order to determine this parameter is required some kind of special equipment and controlled conditions which implies high costs in the development of tests. The present paper proposes a design of a low cost measurement system in order to determine this coefficient with the lower possible error. This equipment was thought for companies or labs where they do not have the economic resources or the infrastructure (environmental controlled labs, heat flux transducers, human resources with specialized knowledge) to do this kind of tests.The system is based on ASTM C 518 - 04 [l] and integrated by two plates (one that contains a thermal resistance and which temperature is controlled by a closed loop controller and the other one with a route of water flow). The thermal resistance is actuated by a relay and a supervisor system checks the total time the relay is on in order to determine the effective power applied to the system. The contact faces of the plates contain a group of temperature sensors connected to a data acquisition system that process and record the temperature in each measurement point.With the power applied to the system, the measurement of temperatures and a process of calibration is possible to determine the coefficient of thermal conductivity. IntroductionWithin the thermal characterization of a material of known variables is the coefficient of heat transfer, since this value can know the amount of heat the material is capable of transferring or isolating. To determine this ratio requires specialized equipment and controlled conditions, which implies high costs in the development of a test. This article proposes a design of a low cost machine to allow closer this coefficient with the least possible error. This equipment was done thinking about companies that do not have the infrastructure (laboratories, controlled environment, heat flux sensors, human resources expertise) and financial resources to conduct these tests."

Jan 1, 2011

By Yongxiang Yang, Yanping Xiao, Robert G. Harskamp

"Stricter environmental regulations demand for safer treatment and disposal of incineratior fly ashes. So far no sound technology and processes are available for a sustainable and ecological treatment of the waste incineration ashes, and only partial treatment is practised for temporary and short-term solutions. New processes and technology need to be developed for comprehensive utilization and detoxification of the MSW (Municipal Solid Waste) incinerator residues. The objective of the current research is to better understand the behaviour of the environmental harmful elements during low or high temperature treatment, and to find an optimum route for an efficient processing of the incineration fly ash. In the present study, the fly ashes including boiler ash and ESP (Electrostatic Precipitator) ash sampled from a MSW incinerator were washed with warm water, and the residues were dried and sintered or vitrified at high temperatures. The solutions from ash washing were analysed, and will be treated for salt extraction and purification. The ash residues before and after thermal treatment were also analysed. The results of vitrification and thermal behaviour were compared with those from the ashes without pre-washing. It was found that water pre-washing is an efficient way to remove certain water-dissolvable volatile salts such as chlorides, and thus the secondary emissions during vitrification could be reduced. INTRODUCTION The air pollution control residues from MSW incineration are classified as harzardous waste, including boiler ash, ESP ash and filter cake. The boiler ash is the firstly settled flue dust in the dust-collecting equipment under the boiler, the ESP ash is collected by an electrostatic precipitator in the second step, finally the flue-gas is further cleaned by the wet-scrubbers and residues are accumulated in the filter cake. Both the boiler ash and ESP ash are classified as hazardous materials, harmful to the environment due to the high concentrations of environmental hazardous elements. However, due to the different locations of the ash collection, the boiler ash has different compositions compared to the ESP ash, and is considered less toxic. Fly ash is generally toxic and with low bulk density, and has to be treated before final disposal. The current industrial practice is normally the landfilling after partial detoxification such as cement solidification."

Jan 1, 2008

By Raghavan Srinivasan, Y. V. R. K. Prasad, William G. Frazier, Steve C. Medeiros

"Aerospace gas turbine disks operate in an environment of relatively high stresses caused by centrifugal forces and elevated temperatures. These severe conditions necessitate the need for materials with good high temperature strength and low cycle fatigue resistance. One class of alloys used for this task is the nickel base superalloys, out of which, lN 718 is the most widely used in the aerospace industry [I]. The properties of IN 718 are attributed to the combined effects of the chemistry, heat treatment, and microstructure. The chemistry is tailored not only for solid solution strengthening but also for precipitation hardening developed during heat treatment, which combined with a fine grained microstructure lead to excellent mechanical properties such as low cycle fatigue resistance and elevated temperature strength. The properties of a gas turbine disk are sensitive to the microstructure, in particular the grain size, which is dependent on the processing history. The ability to precisely control the microstructural development during forging is dependent on controlling the process so that the workpiece is deformed within a ""safe"" region where no microstructural damage or flow instabilities occur. The microstructural mechanisms during deformation may themselves vary within the ""safe"" region and it is desirable to determine them within the range of parameters that are commonly used in industrial processing. The objective of this work is to establish a relationship between the grain size and the process control parameters i.e., temperature and strain rate, in the hot working of IN 178.BackgroundIN 718 belongs to a class of nickel-iron base superalloys with a face-centered cubic (FCC) austenitic matrix strengthened by precipitation of ordered intermetallic or carbide precipitates and is a nickel-rich alloy strengthened by ordered body centered tetragonal (BCT) precipitates, Y"". The alloying of nickel and iron results in the formation of the austenitic matrix, y, while the addition of chromium and molybdenum cause solid solution strengthening. Also, alloying with niobium causes precipitation of the metastable hardening constituent Y"" (Ni3(Nb,Ti)). Extended aging treatments in the temperature range 650 °C - 980 °C allow the more stable orthorhombic 8 phase (Ni3Nb) to form. Trace amounts of boron are also added to serve as grain boundary strengtheners for high temperature creep resistance. Hot deformation of IN 718 is performed between the Y"" and 8 solvus temperatures to facilitate recrystallization and to control grain growth. While deformation below the Y"" solvus (""""962°C) produces no change in grain size, deformation above the Y"" solvus but below the 8 solvus will lead to a dynamically recrystallized microstructure. The presence of the 8 precipitates will pin the grain boundaries after recrystallization and restrict grain growth so that a fine grain microstructure is obtained. Deformation above the 8 solvus ("""" 1038°C) will lead to a microstructure which has undergone grain growth during deformation."

Jan 1, 2000

By Lucas L. Costa, Luiz F. Lopes, Ludy C. Motta, Felipe P. D. Lopes, Sergio N. Monteiro, Lara S. Vasconcellos

"Environmentally correct materials like the lignocellulosic natural fibers, which are renewable and biodegradable, are being extensively investigated as possible substitutes for synthetic fiber in polymeric composites. Several natural fibers have never been thoroughly investigated as possible composite reinforcement. The fiber obtained from the leaves of the buriti (Mauritia flexuosa) palm tree is one example. Therefore, the objective of this work was to study the properties of buriti waste fibers, in amounts of up to 30%, reinforcing polyester composites.IntroductionIn the past century, the technological development gave priority to new synthetic materials with energy intensive methods of production. Today, there is a concern that conventional energy source such as petroleum, natural gas and coal are the main responsible for global warming. Therefore, the use of natural materials is gaining attention not only for the saving in process energy but also the renewable and biodegradable characteristics that make them environmentally correct. The lignocellulosic natural fibers extracted from cultivated vegetables like jute, sisal, hemp, coconut, flax, ramie and many others are typical examples. This type of fiber is being extensively investigated as a possible substitute for synthetic ones, especially the glass fiber, as composite reinforcement [1].A relevant example of lignocellulosic fiber substitution is nowadays occurring in vehicles. The automobile industry is applying composites reinforced with natural fibers to replace parts such as panels and seat cushions made of fiberglass or polymeric foams [4], as illustrated in Fig. 1. The practical reasons for this preference are that natural fiber composites present less damage to tools and molding equipments as well as relatively better finishing and less abrasive surface than corresponding parts made, for instance, of glass fibers. On top of these advantages, low cost is probably the main motivation for the industrial interest for natural fiber composites, especially in the case of residual fibers [5] or post-used fabrics such as jute sackcloth [6]. Natural fibers, however, are hydrophilic and will not form strong bonding with a hydrophobic polymer, normally used as composite matrix [1-3]. Another disadvantage is the heterogeneous characteristics of a natural fiber, which is typical of biomaterials. This results in a relatively great dispersion of dimensions and properties values such as the mechanical strength [1-3]."

Jan 1, 2008

By Pekka Parvinen, Saija Luukkanen, Pentti Pirkonen, Väinö Hintikka, Hannu Sekki

In the study was developed a new method for the treatment soils contaminated by polychlorinated dibenzodioxin and dibenzofuran. The method is based on attrition of soil so that the contaminants absorbed on the particle surfaces are liberated with the fine fraction formed in the attrition process. Same the attrition process produces active surface which can absorb the free contaminants. Before starting the remediation process must be decided the limit value under which the residual concentration must lie. Then in the laboratory is performed an experiment in the base of which is determined the grain size level; material under which much be removed together with the contaminant. In the real sample has been found that after the attrition the limit value 0.5 ng/g (I-TEQ) is obtained when the fine under 0.1mm fraction (20% of the original soils amount) is removed together with the contaminants 96% (original level 10 ng/g; 100%).

Jan 1, 2008

By Yousef Mohassab, Feng Chen, Hong Yong Sohn, Mohamed Elzohiery

The determination of reduction degree in a DR process is sensitive to the total iron in the ore and DRI. An accurate and high throughput analysis method for total iron has been developed. Titration of the solution after tin(II) chloride reduction of ferric ion is a widely used method for iron analysis. However, it is a multistep method that requires many chemical reagents and much time. In this work, an ICP-OES analysis method with higher or equivalent accuracy compared with the titrimetric method was developed. This method has much higher throughput and demands fewer chemical reagents compared with the titrimetric method. In this paper, a comparison of the two methods is presented.

Jan 1, 2016

By Jafar Safarian

A new kinetic modelling technique has been applied to study the rate of MnO reduction from slags by dissolved carbon in liquid iron. Based on a consideration of the fundamental reaction kinetics, a general differential equation for the slag reduction process has been formulated, which then is solved analytically for certain special cases. By re-writing the solutions in a dimensionless form the poorly known kinetic constants are eliminated, which makes the model both flexible and applicable to a wide range of experimental conditions. For example, changes in process parameters such as temperature, metal composition, slag composition, gas composition can readily be captured along with variations in the crucible geometry. Based on a comparison with a series of experimental reduction curves being reported in the literature, it is concluded that the predictive power of the model is surprisingly good, yielding outputs that are both reliable and physically reasonable. An attractive feature of the model is that it provides an alternative way of calculating the activation energies from experimental reductions curves. For example, it suggests that the activation energy for the reduction of MnO by dissolved carbon in liquid iron is about 90 kJ/mol, which is different from the previously reported activation energies. The model also suggests that the crucible geometry, which affects both slag the volume and the resulting slag/metal interfacial area, has a significant influence on the overall reduction kinetics. This design parameter is a key to further optimisation of the process on an industrial scale.

Jan 1, 2006

By Corale L. Brierley

Bioheap leaching, commercially applied for secondary copper ores and agglomerates, is rapidly gaining popularity. Bioleaching of chalcopyrite concentrates is imminent. Copper bioheap leaching encompasses the bioleaching of acidified and agglomerated coarse, secondary copper ore, stacked on permanent or on/off pads. The stacked ore is irrigated with raffinate containing bacteria. LME-grade cathode copper is produced by SX/EW. Low capital and operating costs, rapid start-up, environmental benefits, operational simplicity and a good performance record make bioheap leaching an attractive technology. This paper looks at the state-of-the-art of copper bioheap leaching and chalcopyrite concentrate leaching, the risks, the benefits, costs, bioheap performance and the future prospects of copper bioleaching.

Jan 1, 1999

By George R. St. Pierre

A method for the quantitative description of activity interactions between solutes in a metallic solvent which is consistent with stalistical thermodynamic principles is presented. The chemical potential of a solute in an alloy is derived from the weighted mean of its values in the individual solvent components, µi = S?jµi(i). The weighting factors, ?j, are obtained from the distribution functions. The resulting equation contains far fewer adjustable parameters than the Epsilon Formalism and because of its correct functional form it provides an improved fit to the available data on a variety of alloy systems containing oxygen, carbon, sulfur, nitrogen, and hydrogen. For a binary metallic solvent ( A, B ) containing a solute (i), it is shown that

Jan 1, 1995

By M. A. Gerdel

In carboxylate collector flotation of bastnasite from other semisoluble salt type minerals such as barite various modifiers must be added in order to achieve selective flotation. One such modifier is a lignin sulfonate. It may function in part by acting as a sequestrant for metal ions present, preventing autoactivation in the system by metal ions derived from the minerals themselves. It also functions as a depressant for both bastnasite and barite, chemisorbing on both. However, it is shown that the lignin sulfonate functions as a much stronger depressant for barite than for bastnasite. It is suggested that the; strong depressing action on barite is related to a good fit of the sulfonate into the barite structure.

Jan 1, 1989

By R. Peterson, D. C. Popko, J. Y. Hwang, R. McChesney, A. M. Hein, R. C. Greenlund, M. Jeong

MTU is conducting a study to recycle and reuse the aluminum waste generated from various segments of the aluminum smelting industry. This research is supported by the U.S. Department of Energy and industry. A portion of this effort is to determine the operating efficiencies of Eddy Current Separation, comparing separating characteristics of white and black dross. The results of this effort will be presented here.

Jan 1, 2000

By Guo Xueyi

The nonferrous metal industry is facing the resource depletion, energy crisis and environmental deterioration. The resource recycling is a correct way to promote the nonferrous metal industry development towards sustainable. To realize the resource recycling, the technical support is most important. In this paper, the techniques barrier for nonferrous metal resource recycling are summarized, the fundamental on resource recycling of nonferrous metals are proposed.

Jan 1, 2006

By Rashmi Kumar, Amit Chatterjee, Sanjay Chandra

The practice of adding alloying materials to a molten bath is an integral feature of many pyrometallurgical operations. However, very little is known about the dissolution rate and solution mechanisms of solid additives in liquid melts. In foundries where large tonnages of liquid metals are handled, there is considerable interest in achieving optimum metal quality at minimum cost. This objective is influenced by several factors and the solution is often plant specific. Though the amount, sequence and mode of ferroalloy addition vary from plant to plant, various fundamental factors determine how quickly these additions dissolve in the bath. At the Ingot Mould Foundry (IMF) in TATA STEEL blast furnace hot metal is used to cast ingot moulds. The composition of hot metal desired for making ingot moulds demands addition of 20 kg each of Ferromanganese and Ferrosilicon in the 12 T transfer ladles into which the blast furnace metal is poured at the IMF. Owing to low temperature of hot metal at the IMF, casting commences immediately and complete dissolution of the ferroalloys is often not possible. To study this aspect in detail and to evolve suitable corrective measures, a mathematical model for the melting of a solid particle in a liquid metal bath was developed at TATA STEEL. The model was validated using the data available in literature. In keeping with published work, two separate dissolution periods were identified - a "shell period" and a "free dissolution period". The maximum thickness of the crust formed around a spherical particle shortly after immersion, can be obtained by using the mathematical model which has been developed. The model can also be used to investigate the effect of various parameters such as superheat of the bath, size of the particle, etc., on the maximum crust thickness and the particle melting time. On the basis of this study, the addition of ferromanganese and ferrosilicon was optimized at the IMF in Tata Steel.

Jan 1, 1996

By M. Cowling, S. Kumarl, A. W. Piper, R. A. Forsdick, C. Bailei, M. Patell

"The lead-refining process takes place in hemispherical vessels called kettles. In these kettles, lead-bullion is mixed at a certain temperature to remove impurities from the melt. This paper presents steps in a novel method for calculating vortex shape and flow field in the refining kettle using Computational Fluid Dynamics (CFD). First of all a two-dimensional axisymmetric model is used to calculate the vortex shape at the liquid-air interface. Here action of impellers and baffles are accounted for by adding source and sink terms to the appropriate momentum equations. The model includes Yolume of Fluid (YOF) method to predict the shape of interface deformation, i.e. vortex. This strategy reduces the computationally intensive three-dimensional transient simulations to a more efficient two-dimensional model. The calculated vortex shape is then used to regenerate a full three-dimensional grid. This grid is used to carry out steady-state simulation using the standard multiple-reference-frame method of impeller-fluid-baffle interaction within the commercial code Fluent. Simulation results for both stages of the development are compared with experimental data.IntroductionOne of the most important steps in Lead Refining process is impeller stirred mixing of Lead Bullion in hemispherical vessels. During this process, the melt is treated with one or more reagents in order to remove impurity elements such as copper, antimony, silver and bismuth. These impurities react selectively with the reagents and float to the melt surface in the form of a powdery layer, which is then skimmed for further processing. Figure-! shows (a) the lead refining kettle and (b) the schematic representation of involved flow pattern. Stirring of the lead bath using specific impeller designs, which creates a central vortex, provides a mechanism for draw-down and dispersion of the buoyant reactants. Clearly, effective control of the impeller generated vortex and flow pattern is crucial to achieving efficient operating conditions."

Jan 1, 2001

By Ashish D. Patel, Ramesh S. Minisandram

"Vacuum Arc Remelting (VAR) is the final and, hence, critical melting step for the production of a sound, segregation-free ingot for the manufacture of alloys used in rotating components in aircraft engines. A mathematical model for this process has been developed by the Specialty Metal Processing Consortium (SMPC). The model predicts temperature distribution in the solidifying ingot, flow in the molten metal pool, and the electromagnetic field in the ingot. These predictions may be used to estimate the effect of melting parameters on the pool profile in the ingot. In this paper, typical pool shapes and flow fields during VAR of Alloy 718 and Ti-6Al-4V are presented. The differences in the pool profile are primarily due to vastly different melting conditions. The model predictions are compared to the observed pool shapes from industrial-size VAR ingots.1. IntroductionVacuum Arc Remelting (VAR) is a process in which an electrode is melted in vacuum by the heat from a DC electric arc. Metal droplets from the electrode fall into the molten metal pool, which solidifies in a water-cooled copper crucible to form the ingot, as shown in Figure I. The ingot obtained from VAR is sound, and has superior cleanliness and chemical homogeneity. Hence, the process is the final melting process for most nickel-base superalloys and titanium alloys used in the manufacture of critical rotating components (discs & blades) of aircraft engines. Modeling of this process provides an insight into the effect of melting parameters on the molten metal pool in the solidifying ingot, which is a key first step in process optimization and defect prevention. In this paper, typical pool shapes, both measured and predicted, for VAR of Alloy 718 and Ti-6Al-4Vare presented. Alloy 718 is the most common VAR-processed nickel-base superalloy; whereas Ti-6Al-4V is the ''workhorse"" alloy for titanium-based alloys."

Jan 1, 2004

By R. E. Fanning

"IntroductionThe Aluminum industry is one of many materials industries which strive to make their material the preferred choice for large volume products. In some applications one material has a natural advantage over others, but more frequently several materials compete with one another, each providing one or more advantages and some trade-offs. Customers may design their product with several objectives such as minimum system cost, maximum customer appeal or maximum manufacturing flexibility, choosing materials which best combine cost and performance. In such markets it may become necessary for a material supplier to enhance the attractive features of the particular material to outweigh its disadvantages.It is difficult, if not impossible, to predict how various materials will evolve. Technological breakthrough, government regulations, material availability or sociological issues may redefine the balance between competing materials. In spite of some uncertainty regarding the competitive position of competing materials, there is little doubt that unrelenting pursuit of product quality improvement and cost reduction are essential to future viability of the aluminum industry. It is the intent of this paper to identify some areas where technological improvement would be beneficial. Thus this paper is a collection of briefly described problems that will hopefully stimulate the thoughts and research required for knowledge based solutions. Rolling ProcessA particular example is the beverage can industry where aluminum, steel, glass and plastics vie for a share of the m.arket. The high cost of aluminum relative to steel or glass requires minimizing the amount of metal per can. The high intrinsic value of aluminum has led to extensive recycling of cans although net metal cost is still higher than that of the competing materials. Intensive engineering of the beverage can led to improved design and better understanding of material requirements. These improvements permitted substantial reduction in sheet thickness over the past decade. The downward trend in metal thickness for beverage can sheet is shown in Figure 1."

Jan 1, 1988