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By Guangliang Wu, Dong-chang Huang, Xin-bin Liu

High temperature mechanical properties of 50Cr5MoV roll steel was investigated by Gleeble 1500 thermal simulator testing machine The morphology, composition and microstructure of fracture surface were observed and analyzed by OM, SEM and EDS The results are indicative of that, there are two brittle temperature zones of 50Cr5MoV roll steel at the temperature of 600°C~950°C and 1300°C~1450°C, respectively. The section shrinkage rate is less than 60% The fracture mode changes from mixed ones dominated by intergranular to toughness transgranular one with the increase of temperature at the range of 650°C~1300°C. The fracture is along the solid--liquid phase at the range of 1300°C~ melting point It is crucial to formulate the 50Cr5MoV casting technology, to prevent the cracks and improve the quality of 50Cr5MoV roll steel.

Jan 1, 2016

By Vianey Garcia-Osorio

One of the problems in the carbothermic aluminum process is the substantial loss of aluminum compounds as vapors due to the high temperatures in the process. In order to solve this problem a Vapor Recovery Unit (VRU) is proposed. In this unit operation the aluminum vapor undergoes a series of heterogeneous non-catalytic reactions forming solid, liquid and gas products. In this work a model for the simulation of this unit was developed which includes heat and material balances as well as heterogeneous non-catalytic reactions. The model leads to a system of differential equations; its solution was implemented in Matlab giving as a result a stage-by- stage solid-fluid reaction model.

Jan 1, 2001

By Denise Cristina de O. Nascimento

Natural lignocellulosic fibers are increasingly being used as polymeric matrix composite reinforcement owing to economical and environmental advantages as renewable and biodegradable materials. Among these, the piassava fiber extracted from a palm tree native of South America stands as one of the most rigid with a potential to be used as composite reinforcement. Therefore, the present work investigates the notch toughness behavior, by Izod impact tests, of epoxy composites reinforced with up to 40 % in volume of continuous and aligned piassava fibers. It was found that the incorporation of piassava fibers results in significant increase in the impact energy of the composite. Scanning electron microscopy analysis showed that the nature of the piassava fiber interface with the epoxy matrix is the major responsible for the superior toughness of the composite.

Jan 1, 2009

By Qiang Zhong, Qian Li, Yongbin Yang, Tao Jiang

Thermogravimetric analysis (TGA) has been used to research the pyrolysis and combustion processes of coal used in rotary kiln of iron ore oxide pellet. Furthermore, the effects of air flow and oxygen concentration on the combustion behavior of coal were examined with TGA. The results showed that two individual stages can be distinguished for the pyrolysis of coal, the water evaporation stage and the de-volatilization stage. And the information on ignition and burnout characteristics can be obtained from the combustion process analyzed by TGA. Large air flow almost has no effect to the combustion process except that it enhances combustion intensity. However, the combustion process is further accelerated under oxygen-enriched conditions. With all experimental results, it could provide an attractive approach of analyzing coal for the rotary kiln process.

Jan 1, 2016

By Mim Li, Huimin Lu, Lisha Yang

"CuInS2 thin films solar cells have drawn much attention for their low-cost, stability and high conversion efficiency. The electrodeposition of Cu-In precursor films, as the first step in making CuinS2 solar cells electrochemically in the air-and water-stable ionic liquid based on choline chloride/urea eutectic mixture has been investigated at constant potential. Compared with aqueous electrolytes, the large electrochemical window as well as the high thermal stability of this ionic liquid allow the direct electrodeposition of Cu-In precursor films. Then the precursor films were sulfuretted in a tube furnace at different sulfurization temperatures to optimize the films properties. The films obtained were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS).IntroductionCuInS2 is one of the most prospective absorber materials for low cost thin film solar cells, with a high conversion efficiency that exceeds 32% in terms of theory and nearly 13% in laboratory level [1-2]. In addition to its long-term stability, CuinS2 has a band gap energy Eg ranging from 1.3 to 1.55 eV and an optimal optical absorption coefficient reaching 105cm-1 [3-4]. CuinS2 thin films have been prepared by several methods such as spray pyrolysis [5-6], r.f.sputtering [7], vacuum evaporation [8-9] and electrodeposition. Comparing with vacuum methods, electrodeposition has lots of advantages such as less energy consumption, preparation big area thin film, stable system and enabling cheaper films.The electrodeposition of most technologically important metals has been shown to be possible from a wide range of ionic liquids. These ionic liquids are currently applied in a wide variety area. It is reported that the cell efficiency of chalcopyrite absorber layer (CIS, CISeS, and CIGS) via an electrodeposition route in laboratory condition has reached 11.3% [10]. Copper and indium alloy film is regarded as important precursor for the production of compound semiconductors with sulfur. The electrodeposition of the alloy film from room temperature ionic liquid (RTIL) has not been widely investigated. Only few alloy films, such as ZnTe, CdTe, GaAs and AlSb have been electrodeposited."

Jan 1, 2011

By Matthew John M. Krane

"The macrosegregation patterns and convective behavior of a Pb-5wt%Sb-35wt%Sn alloy are studied using new numerical treatments of solid particle motion and of transport phenomena occurring during the solidification of ternary metal systems. At this composition, the solidification which occurs while the local liquid composition is in the (Pb)-(SbSn) binary eutectic trough has a significant effect on these phenomena. The effects of this solidification path on fluid flow and macrosegregation are compared to the more familiar binary alloy patterns and the effect of solid particle transport is evaluated. The final predictions of macrosegregation are compared to measured composition profiles. IntroductionThe macroscopic maldistribution of alloy constituents during solidification, commonly called macrosegregation, is a defect which occurs in real metal processing systems. This nonuniformity of species distribution, especially when it forms a high composition gradient or a poor distribution of secondary phases, can lead to areas of high stress concentration, which contribute to cracking during extrusion or forging of wrought alloys or when an as-cast piece is severely loaded in service [1, 2]. Macrosegregation studies in binary systems have become quite common since the introduction of single-domain numerical models which feature one set of conservation equations and boundary conditions for an entire, fixed computational domain containing solid, liquid and multiphase regions. A complete review up to 1995 has been presented by Prescott and Incropera [3]. However, most commercial alloys generally have more than two species in amounts significant enough to affect the convective flows which lead to macrosegregation and other defects. The formation of secondary solid phases, including eutectic and peritectic reactions, also may occur in commercial metal alloys and should be treated using appropriate thermodynamic models."

Jan 1, 1999

By Hiroyuki Matsuura

The effects of P2OS or Na2O addition on the reaction rate of CO2 dissociation on the surface of FexO-base molten oxides was investigated at I 773K by isotope exchange method 1-6. The rate constant decreased with increasing P2Os content of molten oxides and the residual rate constant was observed at high P2OS content. On the other hand, the rate constant increased with increasing Na20 content for FexO-SiO2 melts, The rate constant was evaluated by the composition of oxides and the rate controlling step of CO2 dissociation was discussed.

Jan 1, 2003

By H. Y. Sohn

The purpose of this article is to analyze critically and quantitatively the effect of chemical equilibrium on the overall rates of fluid-solid reactions. It is shown through a mathematical analysis that a reaction with a small equilibrium constant (a positive standard free energy of reaction) is more likely to be rate-controlled by pore diffusion or mass transfer than a reaction with a large equilibrium constant. The overall reaction rate of the former also tends to be slow. Furthermore, the apparent activation energy of such a reaction approaches the standard enthalpy of reaction (M-f'), rather than the true activation energy of the chemical reaction. The Law of Additive Reaction Times developed by the author is shown to apply to equilibrium-limited fluid-solid reactions and to be useful in quantitatively analyzing the behavior of such reactions.

Jan 1, 2003

By Tianzu Yang, Weifeng Liu, Lin Chen, Deyu Wang

"Due to the gradual exhaustion of easily extractive gold ores, it is vital to make efficient use of refractory gold ores which hold 30% gold storage of the world. However, the disadvantage of current processing technologies for refractory gold ores consists of severe pollution, low gold extraction ratio, high investment, etc, thus great research interests were attracted during recent years. This article provides an overview of the distribution and categories of the refractory gold ores in the world. The state of art in processing refractory gold ores by pyrometallurgy, hydrometallurgy and biometallurgy techniques and their industrial applications are highlighted. Potential environmental conservative techniques for efficient gold extraction are also reviewed.IntroductionResources of Refractory Gold OresAs easily extractive gold ores are going to be exhausted with the large scale mining nowadays, refractory gold ores are becoming more and more important. Gold in the refractory gold ore cannot be fully extracted using conventional method (cyanidation) even with fine grinding. The amount of gold in the refractory gold ores is about 1500~2000t in China, which occupies 30~40% of the total gold storage [1]. Therefore, it is vital to make efficient use of refractory gold ores."

Jan 1, 2013

By H. Kaffash

Ferromanganese is a ferroalloy with high manganese content which finds many uses for example as deoxidizer in steelmaking industry. However, there is very little data on the dissolution rate of carbonaceous materials in Mn containing metals. In this paper, the kinetic analysis of carburization reactions is investigated for Mn–Fe alloys. Dissolution rate of graphite in pure iron and four different alloys with 10 wt%, 40 wt%, 60 wt% and 85 wt% manganese at 1823 K was studied. Results showed that the dissolution rate of carbon from graphite increased with increasing time for all alloys. The dissolution rate constant increased with the increasing manganese content from 6.5 × 10−3 cm/s for 0%Mn to 23.6 × 10−3 cm/s for 85%Mn.

By M. Krishna, Jayagopal Uchi1, Shanta Sastry, B. M. Satish

"A well-considered composite of ZA-27 reinforced with weight percentage 0, 2, 4, and 6% of alwninite particulate has been made by compocasting technique. The elastic properties of ZA- 27 /alwniniute particulate composite were determined by using U1M. The results showed that the modulus of elasticity and UTS of the composite gradually increases with increase in the wt.% of reinforcement. However, the overall ductility decreased monotonically with an increase in reinforcement. The results of these tests· as well as the predictions of several model~ for composite strengthening available in the literature were compared with experimental results. The data observed from Young's modulus by measurements studies were compared with theoretical results predicted by Eshelby model.IntroductionMetal matrix composites (MMCs) have received increasing attention in _the recent decades as engineering materials. The introduction of a ceramic reinforcement into a metal matrix produces a composite material resulting in an attractive combination of physical and mechanical properties that cannot be obtained with monolithic alloys. Particulate reinf9rced MMCs among the discontinuously reinforced MMCs have attracted quite a lot of attention both in the industrial sectors and the academic communities. There is an increasing need for knowledge about the processing techniques and mechanical behavior of particulate MMCs in view of their production getting enhanced and their commercial applications becoming wider [I]. Interest in particulate reinforced MMCs is mainly due to easy availability of particles and economical processing techniqu"

Jan 1, 2000

By H. Y. Sohn

"The nonferrous production industry has gone through a remarkable transformation in recent years in terms of developing and adopting new technologies. Technology innovations have largely been driven by the need for greatly improved environmental protection in addition to increased productivity. One of the most notable aspects of the new technologies is their ability to reduce the emission of sulfur and other pollutants to extremely low levels.The current industry trends towards more environmentally friendly technologies are bringing about additional benefits of developing more efficient, technically advanced, and continuous processes in closed reactor vessels. Key aspects of these modem trends include the use of increased oxygen enrichment in the process gas, better process control, reduced manpower requirements, and plant operations with more skilled personnel.Computer simulation and modeling of complex processes have become more reliable, realistic, and thus increasingly useful in metal production. Some of the notable examples are reviewed.Finally, the need and advantages for value-added production in the nonferrous industry are discussed.I. IntroductionMost recently commissioned technologies for nonferrous metals production have been developed largely in response to environmental concerns. One of the most remarkable improvements made by the nonferrous industry in the last decade has been the rapid increase in sulfur capture. Before the start of the last decade, 90% capture of sulfur was considered good. Since then, strict emission regulations have become the norm in advanced societies, although smelters in many parts of the world still operate with limited pollution control. Other emissions and discharges have also been substantially reduced, resulting in much improved working conditions and worker hygiene in addition to the overall environmental protection. The development of the more environmentally friendly technologies has accompanied other advantageous advances made in the nonferrous industry, i.e., the trend towards more gas-tight, continuous processes and larger plants. This has increased the competitive edge enjoyed by the industry in the industrial countries, offsetting the higher costs of labor and pollution abatement that they have to overcome in those countries. Experience has shown that clean technology often leads to a profitable business, because its adoption forces the concomitant advancement of related technologies in addition to the avoidance of penalties imposed by the public on pollution-prone industries. Needless to say, there are other driving forces for new technologies such as reduction of operating and capital costs, improved product quality, and energy considerations in terms of reduced consumption and utilization of readily available sources."

Jan 1, 2000

By R. Ratnagiri, B. Minaie

"In order to expeditiously produce defect-free metallic components in materials processing applications, the relationship between the process parameters and the product properties needs to be well understood while minimizing the production engineering iterations. To achieve this goal, a realistic mathematical formulation of the process should be carried out and an appropriate numerical modeling of various phenomena occurring in such process should be implemented. The materials processing of transforming the molten material into a finished metallic component involves fluid flow and solidification/melting. In the present paper, a finite element based analysis of the fluid flow ·and solidification/melting phenomena in cavities is presented and the various issues in modeling these phenomena are discussed. These transport phenomena play an important role in determining the final characteristics and material properties of the part by affecting the formation of defects and microstructure. A realistic numerical modeling of these phenomena can significantly reduce the rejection rates during the process and can increase the quality of the final product.IntroductionDuring the intelligent materials processing of various metallic components, it is often required to have a thorough knowledge of the behavior of the transport phenomena involved in this process. This is due in large to the coupling that exists between the transport phenomena and the final material properties of the components produced during materials processing. This interrelationship demands that the pertinent transport phenomena in the form of fluid flow and solidification/melting be studied and predicted accurately. In many materials processing applications, the fluid flow is in the form of either a forced convection free surface flow intended to fill a cavity or a natural convection flow resulting from the gravity when the cavity is filled. In either case, the phase change in the form of solidification/melting is also involved in order to complete the process. However, the thermal history during this phase change has a direct impact on the material properties of the final part and the possible defect formation that may be involved. This thermal history itself is dependent on the nature of the fluid flow during the earlier stages of the process. As such, there is a coupling between the fluid flow, phase change, microstructure, and defect formation in the resulting component. It is therefore necessary to analyze these phenomena in order to find optimum methods to produce good quality parts by minimizing the defects that may be generated. Such an analysis can result in the development of appropriate numerical models for the process that can facilitate the economical and timely manufacturing of various components with high consistency. The present paper discusses the issues related to the transport phenomena encountered during materials processing of components engineered largely by using various combination of convective fluid flow and solidification/melting in cavities."

Jan 1, 1994

By Zhihe Dou, Yan Li, Qiuyue Zhao, Guozhi Lv, Yan Liu, Hongliang Zhao

"Abstract: How to reduce carbon dioxide emissions has become a vexing problem, meanwhile, there exist high energy consumption and low efficiency problems in the existing CO2 capture and storage technologies. For CO2 comprehensive Utilization, this paper researches a new technology of absorbing the CO2 emission with high alkaline calcium or high alkaline wastewater sludge mineralization of calcium and invent a core device for multi-level jet carbonation. The industrial test has been carried out in China Xinyu slag Engineering Co., Ltd. The wastewater flow is 150m3/h in the pilot scale. The prepared calcium carbonate has a whiteness greater than 90%, particle size less than 150nm. The mineralization of aluminum exhaust with waste carbide indicates that the CO2 absorption rate is greater than 99.0%, CO2 concentration in the exhaust gas is lower than 0.08%, the purity of mineralized calcium carbonate is greater than 99.0% and particle size is less than 100 nm.InstructionAccording to the statistic data from IEA (2009), the carbon dioxide discharge from fossil fuel consumption in China has exceeded it in the US by the year of 2007, China, has become the largest emitter of carbon dioxide all over the world. Meanwhile, the economic scale is still on an increasing trend in the next 50-100 years, leading to a continuous increment in carbon dioxide discharge. According to the international energy agency forecasts, the energy-relative CO2 discharge in China will rise to 11,615 million tons, 91.3% higher than it in 2007. In the year of 2012, the CO2 gross discharge has reached 10,000 million tons, obviously higher than the predicted value. It is a tremendous task to reduce the emission. Non-ferrous metals industry is one of the largest emitters of carbon dioxide among the industrial circle, the whole industry might discharge a huge amount of carbon dioxide (over 600 million tons), in which the electrolytic aluminum industry is the largest energy consuming industry and CO2 emitter. At present, the CO2 discharge has focused by the whole world due to the environmental problems it causes; meanwhile, supplement of new carbon source is needed due to the exhausting oil and coal resources, so that various countries in the world are attaching importance of the recycle and purification of CO2. Many countries are studying on the cyclic utilization of carbon dioxide. Gas CO2 is mainly applied in chemical, pharmaceutical raw materials, beverage filling agent, refrigerant, inert medium, solvents, pressure source, the welding protective gas, antioxidant and fire extinguishing agent, etc. Solid CO2 is mainly applied in penicillin production, fish, cream, ice cream and other food storage and transportation at low temperature, etc. nowadays, such methods as absorption method, membrane separation, adsorption, etc. are widely used to recycle CO2, with such problems as high investment cost and technical constraints etc."

Jan 1, 2014

By Pengfu Tan

In order to understand and control the formation of dioxins and furans in iron ore sinter plants and to possibly avoid expensive end-of-pipe removal stages, thermodynamic calculations on the stability of PCDD/Fs have been combined with sinter process modeling by means of kinetic simulations and computational fluid dynamics. Three thermodynamic databases of PCDD/Fs, derived using the Group Additivity approach and two computational molecular modeling methods, MNDO and PM3, respectively, combined with the SGTE database have been used to model the PCDDIF formation and the PCDD/F isomer distributions in iron ore sintering. The results show very similar conditions for the PCDD/F formation using the different databases. Concerning the isomer distributions of toxic PCDD/Fs, the calculated data derived from the MNDO method showed optimum agreement with measured values from industrial furnaces. The thermodynamic calculations also proved that the isomer distributions found in combustion processes are equilibrium values, while the concentration ratio of PCDDs and PCDFs in the wind boxes does not represent an equilibrium state. A CFD model of iron ore sintering was developed including the kinetics of 15 relevant chemical reactions with the aim of describing the temperature fields and the gas flow patterns in the sintering bed. On the basis of these information and experimental observations reported in the literature possible pathways for the PCDD/F formation in sinter plants have been identified: PCDD/Fs are formed in the critical temperature region of 250 to 450°C below the combustion zone, are then carried downwards with the gas and condensed close to the bottom of the sinter bed. Transported to the discharge end with the solid mixture, they are again released into the gas phase when the flame front approaches the bottom. PCDD/Fs are also formed in the last wind boxes when the hot off-gases cool down and reach the critical temperature range. Consequently, methods to reduce the dioxin formation reactions are proposed including inhibitor addition to the sinter feed and off-gas quenching.

Jan 1, 2003

By A. Schönecker, P. Y. Pichon, B. Kraaijveld, Y. Meteleva-Fischer

"Ribbon-growth-on-substrate is a casting method, which offers a possibility to control heat flow, nucleation and subsequent crystal growth at the liquid-substrate interface. This technology allows for low-cost and high throughput shaping of silicon sheets with controlled crystal grain size and orientation for use in solar cells. In this work, sheets of silicon- metal silicide composite materials were produced and their microstructure was studied. It was shown that depending on the relevant phase diagram and casting conditions, a micro/nano-sized eutectic structure of the casted sheet can be formed. Such composite materials possess properties promising for various applications in energy generation, storage and conservation. The advantages, potential and challenges of the ribbon-growth-on-substrate technique for production of composite sheet materials as well as novel areas of application for such materials are discussed.IntroductionThe Ribbon Growth on Substrates (RGS) process is well known in the solar industry as a process to produce multicrystalline silicon wafers. An industrial size pilot production line for continuous casting of silicon wafer was developed by RGS Development B.V. in the Netherlands (Figure 1). A comprehensive review of this technology and properties of the produced silicon wafers were reported by Schönecker et al [1]. The principle of the RGS process is explained in Figure 2. The relatively cold substrate extracts the crystallization heat from the liquid silicon in the casting frame. This results in the growth of a silicon ribbon (Vc) in contact with the substrate. When the substrate (Vp) is transported from the casting zone into the cooling section, the crystal growth stops, the wafer can be removed and the substrate can be re-used. Last few years large work was done on the industrialization and market development of RGS wafers for the solar industry. Part of this work was discussed by Schönecker et al [2]. Although there is still a good perspective on the middle and long term solar market for the RGS wafers, the current market situation was found to be unfavorable for new entrants."

Jan 1, 2014

By F. Patisson

During exothermic gas-solid reactions, heat generation makes temperature rise and modifies the rate of the various mass transfer processes, namely the chemical reaction itself, the pore diffusion and the external transfer. We have investigated this thermal effect during the oxidation of zinc sulfide porous pellets in a thermo balance furnace, between 550 and 900°C-and under O2-N2 atmosphere. The results have been' analyzed by using, firstly, the law of additive reaction times derived from the isothermal Grainy Pellet Model, and, secondly, a new numerical model taking into account non-isothermal conditions. Both the models can satisfactorily simulate conversion versus time, but the numerical model also depicts the temperature evolution within the pellet. Finally it is shown that owing to the heat generation the zinc sulfide oxidation takes place under diffusion control (3/4 internal, 114 external) in all the cases studied. During the course of reaction, the. pellet undergoes strong temperature variations, with thermal gradients confined to a shell oxide layer.

Jan 1, 1996

By N. J. Themelis

In the last two decades, the Outokumpu flash smelting process has become the dominant new technology for copper smelting and has? also been applied to the smelting of other metal sulfides. The application of oxygen enrichment and improvements in concentrate burner and furnace design have resulted in ever increasing smelting rates per unit volume of the reaction shaft. This paper examines the. rate phenomena taking place in the reaction shaft of the Outokumpu furnace and compares information obtained from a mathematical model of heat and mass transfer rates to results obtained in pi1ot tests conducted at Pori, Finland, and to actual performance of a number of flash smelters around the world. 2?

Jan 1, 1985

By Sergio N. Monteiro

Polymer matrix composites have been applied in components such as helmets and shielding for which toughness is a major requirement. Natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. The objective of this work was then to assess the Izod impact resistance of polymeric composites reinforced with different amounts, up to 30% in volume, of a promising high strength natural fiber from the Amazon region known as curaua. The results showed a remarkable increase in the notch toughness with the amount of incorporated curaua fibers. This can be attributed to a preferential debonding of the fiber/matrix interface, which contributes to an elevated absorbed energy.

Jan 1, 2009

By Tapani Järvinen

Non-ferrous metals and metals in general are considered as being non-renewable natural resources. Metals are needed because of their excellent and irreplaceable properties. The consumption of metals, with the exception of carbon steel, is steadily growing by 1-3 % annually, and that of stainless steel as much as 3-6 %. This is a general trend, which is periodically disturbed by cyclical variations. In recent years so-called "New Economy" has become prominent in the public media and the market value of the traditional industry has been well below its real value and importance. Nevertheless, the modem society requires metals today and also in the future, and the companies using the most modem technology in a responsible way and innovative solutions not only in technology, but also in everything they do will survive. This paper describes the role of Europe as a producer of primary base metals and as a supplier of technologies in the base metals industry. It concentrates on the development and commercialization of technologies and project implementation in the metallurgical industry. As one example of a European approach to these matters the paper presents Outokumpu' s response to the future challenges in the base metals industry. Outokumpu Oyj is one of the leading metals and technology companies in the world of stainless steel, copper, zinc, and sales of technology in metals and minerals businesses. Outokumpu applies its knowledge of metals and processing to generate value for its customers and shareholder. Everything we do, we do in an economically, environmentally and socially responsible way.

Jan 1, 2003