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By Anna Wasilkowska

The study concentrates on the effects exerted by microstructure, deformation history and uniaxial stress conditions (temperature, stress state, strain rate) on the mechanical properties offerritic TRIP-aided steels for automotive applications. In low-alloyed TRIP-steels it is quite difficult to separate the effect of the austenite to martensite phase transformation from the influence of the ferritic matrix contributing to the yield stress and uniform elongation. Investigation of transformation kinetics of retained austenite as a function of the deformation temperature show that using the parameter k to characterize the retained austenite stability allows to identify regious of different temperature sensitivity separated by a transition temperature of 10±5°C. The observed low strain-rate sensitivity of the flow stress is an intrinsic property of the ferritix matrix and points to defomtation governed by slip. The ultimate tensile strength is much stronger affected by temperature than the yield stress. The influence of the temperature on the elongation is complex, because of the heating of the specimens by 60-l20°C at moderate and high strain rates. The increase of the total strain can be understood in terms of thermal softening of the ferrite. On the other hand, the steep increase of the stress during dynamic testing is an effect of accommodated elastic and plastic strains in the matrix. The strain- hardening exponent is dependent on the conditions imposed during testing. The martensite transfomtation rate is lower and the critical stress for martensite nucleation is much higher under compression compared to tensile loading. In secondary tensile tests, the yield stress increases steeply, and the ultimate tensile strength and the total elongation depend linearly on the amount of pre-straining. The results confirm that in the range of 8=10-4 s-l the TRIP-effect governs room temperature plasticity. Keywords: TRIP-steels, mechanical properties, strain rate sensitivity, temperature sensitivity, austenite stability

Jan 1, 2003

By Srinath Viswanathan, Adrian Sabau

"In general, the occurrence of microporosity during metal casting is due to the combined effects of solidification shrinkage and gas precipitation. The governing equations for fluid flow and hydrogen evolution indicate that porosity formation and fluid flow are strongly coupled. However, in most studies on microporosity, it is considered that the porosity formation does not influence the fluid flow in the mushy zone. In this study, a computational methodology is presented for the numerical simulation of interdendritic fluid flow and microporosity evolution. The solution algorithm presented includes a fully coupled, implicit treatment of microporosity and local pressure in the mushy zone. The effects of microporosity evolution due to the local pressure drop in the mushy zone, and pore expansion in casting regions where liquid feeding alone cannot compensate for the solidification shrinkage are also considered. It is shown that neglecting the effect of porosity formation on the pressure in the mushy zone yields higher pressure drops. By its growth, microporosity partially compensates for the solidification shrinkage, reducing the feeding demand. A reduced feeding demand requires less fluid flow to compensate for solidification shrinkage, and results in smaller pressure drops in the mushy zone. Therefore, in order to accurately describe casting defects, comprehensive models of fluid flow, heat transfer, and solidification must include the effect of microporosity as well.IntroductionIn the terminology commonly used by foundrymen, porosity is usually considered to be either ""hydrogen"" or ""shrinkage"" porosity. Hydrogen porosity is the term given to porosity that is generally rounded, isolated, and well distributed. Porosity that is interconnected or clustered, and of an irregular shape corresponding to the shape of the interdendritic region, is usually termed shrinkage. In general, the occurrence of microporosity in aluminum alloys is due to the combined effects of solidification shrinkage and gas precipitation [1]. Continuum models [1, 2- 7] have been used to predict the level of porosity in castings. A number of other studies have also attempted to understand the phenomena of porosity formation and pore growth [8-10] and pore morphology [11].The governing equations for fluid flow and hydrogen evolution indicate that porosity formation and fluid flow are strongly coupled. However, in most studies [4, 9, 10], it is considered that the porosity formation does not influence the fluid flow in the mushy zone. Kubo and Pehlke [3] presented a methodology for the prediction of microporosity distribution in shaped castings by considering the effects of both the hydrogen precipitation during solidification and the pressure drop in the mushy zone. In their approach, the local pressure and porosity were computed in an uncoupled manner based on a ""flux of interdendritic liquid"" criterion, i.e., either pressure or porosity was first computed using the other variable at the previous time step. Their approach has been used with little change in numerous studies [6, 12, 13]. Recently, Kuznetsov and Vafai [14] presented a fully coupled, one-dimensional model for the computation of pressure and porosity. They showed that neglecting the effect of porosity formation on the pressure in the mushy zone yields higher pressure drops and an over-prediction of final porosity. They also showed that the influence of porosity formation on the pressure is larger at lower pressures in the mushy zone."

Jan 1, 2001

By Eva B. Kisvarsanyi

An Early Proterozoic orogenic terrane of metasedimentary and metaigneous rocks underlies Nebraska, Kansas, and Missouri. Middle Proterozoic epizonal terranes of anorogenic granite and rhyolite, a known metallogenic province partly exposed in southeastern Missouri, overlap the orogenic terrane on the south. These Proterozoic terranes, covered by less than 1,000 meters of Phanerozoic strata, contain a virtually untapped source of mineral wealth and are one of the last frontiers for geologic exploration in the continen-tal United States. Petrographic study of subsurface samples is a powerful tool in the identification of favorable host rocks for a variety of ore deposits.

Jan 1, 1987

By James Cornwell, John A. Elton

"Thermionic induced reactions and radiation resonance catalysis of aluminum and aluminum oxide materials exposed to microwaves and triboemissions will be described and explained from both a fundamental and practical level. Magnetron operation at distinct operating conditions that generates both plasmon and triboemissive radiation will be explained and the resulting tribochemical and radiation resonance catalytic reactions between aluminum, aluminum oxide, water and graphite will be delineated. The generation of hydrogen from these materials using triboemissive radiation and microwaves will be described, and the application of this methodology for hydrogen based technologies will be discussed.IntroductionProtective Systems Directed Energy RadiationProtective Systems, Inc, has developed a new radiation device called the EMR (Electromagnetic Resonator) that has unique characteristics that separates it from traditional microwave and rf radiation devices. The radiation from the EMR device is generated using a modified electronresonance magnetron with proprietary filters and operating characteristics.Electronic Device Shutoff. When electronic devices such as cell phones, computers, and other IC based electronics are placed within the EMR radiation, these devices become non-functional as long as the EMR beam is active. Upon removal of the EMR radiation the devices either become operational again or become operational after a cold start. The devices are not damaged by the irradiation.Faraday Cage Interaction Effect. When any of the above electronic devices are placed in a Faraday cage and activated within the Faraday cage without EMR radiation, they operate normally. However, these devices will still be rendered inoperative when an EMR beam generated outside the Faraday cage is directed at the electronic."

Jan 1, 2010

By Rajashekhar Marthi

Lithium is a key component for future electric vehicle batteries and energy storage. The future availability of lithium to meet the growing demands remains in question. Around 60% of lithium resources exist in the form of continental brines. Traditional methods to recover lithium from brines use solar concentration with precipitation and have found limitations in lithium extraction due to interference of Mg in high Mg/Li brines. Thus, there is a need for highly selective adsorbents. Recently, spinel structured delithiated lithium manganese oxides have demonstrated promising results. However, due to the small particle sizes, it is economically difficult to recover the adsorbents and thereby limits industrial applications. In our work, LiMn2O4 ion sieve was synthesized and immobilized on diatomaceous earth. Fundamental adsorption studies were carried out in lithium buffer solutions to understand the nature of adsorption and kinetics. The adsorbents were also tested for recycle stability, as well as recovery of lithium from Great Salt Lake water samples.

By Rolando Campos

In August 1993, the operation of Refimet Chile's copper custom smelter commenced at La Negra, near Antofagasta in northern Chile. Design smelter throughput corresponded to 235 000 tonnes of concentrate, calcines and copper cements arising from suppliers in the north of the country to produce 90 000 t/y of blister copper. Refimet had initially gained experienced in building and operating leaching, roasting and a blast furnace facility at Rungue, near Santiago, followed by Roasting at La Negra. The initial smelter project was based on conventional reverb- smelting and Peirce-Smith converting and the majority of equipment was 'purchased second-hand and rehabilitated or modified. After only 3 years in production, the treatment capacity was significantly improved by introduction of technical improvements to the original plant operating scheme. Recently, the plant was further expanded to an annual smelting capacity in excess of 400 000 t/y feed, corresponding to around 160 000 t/y copper production. This expansion, referred to as Phase 2, was achieved by modification of the reverb to oxy-fuel firing, addition of a further (second-hand) acid plant, fire refining and anode casting facilities. Parallel development of concentrate injection into enlarged converters-also took place. Following successful commissioning of Phase 2 expansion, initial engineering studies for a third expansion phase have been completed. This aims to use leading technology based on bath smelting of bone-dry concentrates in a Continuous Reactor. This paper provides an overview of the relatively short plant history, its development and improvements together with operating indices achieved.

Jan 1, 1998

By Xiaoyan Xiang, Wenqiang Yang, Wentang Xia

Magnesium aluminate spinel is widely used in the metallurgical industry as refractory material, however, natural magnesium aluminate spinel is rare and most of the magnesium aluminate spinel is synthetic. The traditional synthesis of magnesium aluminate spinel often needs high temperature, which leads to more energyconsumption. In this article, solid phase sintering process was employed to synthesize magnesium aluminate spinel, in which, magnesium and aluminum oxide were used as raw materials and magnesium and aluminum powder were used as composite additives. The mass ratio of magnesium and aluminum on the effect of synthesis of magnesium aluminate spinel and the characteristic of the synthesis at different temperature and time was discussed. Experiment found that the synthesis temperature was observably lowered when the addition of magnesium and aluminum was 2.0% and 1.0% respectively.

Jan 1, 2016

By Toshiaki Tsuru, Takeshi Ohgai, Hisaaki Fukushima, Shigeo Kobayashi, Tetsuya Akiyama

"Electrodeposition behavior of Zn-Cr alloys from the methanol baths was investigated. In the methanol baths of low Cr3+ concentration, Cr (III) compound was incorporated in the deposits and no lusfrous Zn-Cr alloys was deposited. However, Cr was existed as metallic state in the deposits obtained from the baths of higher Cr3+ concentration. With an increase in water content in the baths, the chemical state of Cr in the deposits changed from metallic to trivalent state. Under the condition that metallic Cr can be electrodeposited, Zn deposition was significantly polarized to the potential of Cr deposition.INTRODUCTIONAn attention has been paid to Zn-Cr alloy plated steel sheet because of its excellent properties for body panels of automobile and electrical appliances [1]-[4]. This plating process can be operated using the sulfate solutions containing Cr3+ ion [1] - [6].In decorative single Cr plating, on the other hand, many attempts have been made to electroplate Cr from trivalent electrolytes, which is motived by environmental deficiencies of the presently used hexavalent process [7]. [8]. However, it has been reported that in the aqueous solutions the behavior of the electroreduction of 0 3+ is atypical due to the complicated nature of the chemistry and electrochemistry of cr3+ species [9]-[11]. Even in Zn-Cr alloy plating, it is difficult to codeposit metallic Cr with Zn in simple sulfate electrolytes [l]-[4], [12]. Therefore, it can be expected that the electrodeposition behaviors of Zn-Cr alloys as well as Cr are significantly changed when the electrodeposition is conducted in non-aqueous plating solutions.In this study, the electrodeposition of Zn-Cr alloy was conducted from methanol solutions to clarify the electroreduction mechanism of Cr3·-Cr0 in the alloy deposition process."

Jan 1, 2000

By Patricia Negrini Siqueira

Abstract. Polymers are susceptible to changes in their chemical structures that affect their mechanical properties under weather condition. Exposure of plastics to UV radiation causes a loss in their mechanical properties and/or change in appearance, including reduced ductility, color changes, yellowing and cracking. Today, there are several additive systems (light stabilizers) developed to work according to resin, final application, type of cultivation, and other characteristics. This study evaluates the different additive systems (Hindered Amine Light Stabilizer - HALS, nano calcium carbonate - NPCC, nZnO and nTiO2), applied 0.75% (in weight) in linear low density polyethylene (LLDPE). The samples were mixed by high rotation homogenizer and extrusion. Later, the samples were molded by injection and aged in QUV-B simulating 6 months of exposure to weather. Tests of FT-IR and tensile strength comparing to the non-aged samples were carried out in order to evaluate the performance of several additive systems.

Jan 1, 2015

By Bradford C. Wesstrom

The extraction of metals from Copper Refinery Slimes may involve many different processes. This paper describes the use of pressure leaching for decopperizing of copper refinery slimes at the El Paso Refinery. Process equipment will be described, along with the process chemistry, unit operations and unit processes associated with the decopperizing process. Copper contained in the raw slimes ranges from 15-35%. After autoclaving less than 1 % copper remains.

Jan 1, 2000

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 Thomas Niehoff, Yin Qing, Wei Zhongling, Liu Yongguo, Zhang Deliang, Tang Le

The gold ore of Shandong Gold Mining (Xinhui) was a refractory ore, which contained multi metallic sulfides (ZnS and PbS etc.) and carbonaceous. The gold ore concentrate came into leaching process and thickener and zinc replacement to recover gold. In order to improve gold recovery, the GOLDOX™ hydrometallurgy process was studied in Shandong Gold (Xinhui) by bench scale and 6 month plant scale test supported by Linde Gas. It was shown that the process promoted the leaching kinetics and improved gold recovery. The residue grade reduced 0.22 g/t in average after oxygen was applied. This indicates an operating profit increase 850,000 yuan/a in the plant. It was setting a good example for similar gold mine plant and would promote the oxygen application in Chinese gold mining industry.

Jan 1, 2015

By Fathi Habashi

During the recovery of copper, nickel, zinc, and lead from their sulfide ores, large amounts of sulfur dioxide are generated. A fraction of this gas is captured and transformed into sulfuric acid and liquid SOl and the remainder is emitted to the atmosphere. Numerous proposals were made to solve this problem. Hydrometallurgy offers the only valid solution by which elemental sulfur instead of sulfur dioxide can be produced. Sulfur can be easily stored, transported long distances, or transformed into S02 and H2S04 when desired.

Jan 1, 1996

By C. P. Snyman

Three independent methods of coal classification can be distinguished, namely on the basis of grade, type and rank. The latter two can be determined accurately and unambiguously only by means of microscopical techniques. These three independent variables affect all the coal properties and therefore also the technological behaviour of a particular coal. The influence of the inorganic constituents of coal on the fusibility of the ash and on the length of the slag, and also on fouling and slagging, is discussed. The fractionation of the ash-forming constituents during combustion and gasification of pulverised coal shows that fouling and slagging are not related directly to the fusibility and composition of ash of the coal as a whole. The results of combustion experiments using a drop furnace technique indicate that the ignition temperatures of the light volatiles in the coal, and of the formed char, as well as the burn-out time of the char are more dependent on the rank than on the type or grade of the original coal. High-ash coals, however, apparently ignite at lower temperatures and are more reactive than low-ash coals of similar type and rank. The surface properties of coal, which are important in froth flotation and oil agglomeration, correlate well with the inherent moisture content (and by inference with the heat of wetting and the calorific value) and therefore with the type and rank of the coal. In coal exploration, variations of rank offer the possibility of predicting the presence of an intrusion near the seam, thus contributing to more effective exploration and mine planning.

Jan 1, 1991

By B. Q. Li, R. A. Mirshams

"A numerical algorithm is described for the simultaneous prediction of the thermomechanical behavior of the materials and microstructure evolption during metal forging. The numerical development is based on the finite element solution of the thermoviscoplastic deformation of metals coupled with the internal state variable model describing the microstructure evolution involving work hardening, recovery, recrystallization and grain size distribution. The finite element code for rigid viscoplastic deformation is developed based on the modification of the existing code for the thermal and fluid flow calculations. The code is tested against and compares well with the results reported in literature. The procedures for the integration of the · rnicrostructure model into the macro finite element model are described. Results are presented showing the characteristics of materials dynamics and mechanical deformation during simple metal forging processes.IntroductionIn industrial deformation processes such as hot rolling and forging, the workpiece undergoes both macroscopic plastic deformations and microstructural evolution. A computer model that allows to predict both materials dynamics and macroscopic deformation is obviously more useful for both fundamental understanding and deformation process optimization. For some industrial applications, especially those involving novel, light and high strength materials, such an integrated model is critical in that both materials and thermomechanical 'behavior during forging must be carefully controlled to obtain the products that meet the desired strength requirement [I]."

Jan 1, 2000

By Rejane Tubino Geyer

The volume of electric arc furnace (EAF) plus oxygen (BOF) slag produced yearly in the world is about 84 million ton. Because of this, the study of recycling processes as a way to solve the storage problem of these slags rise in importance. There are, however, some inconvenients on using this byproduct: lime, which takes part of the process of steel production, remains as a non-reactive raw product in the slag. Since lime reacts in presence of humidity, forming expansive compounds, slag use is strongly limited. There are some utilizations for the electric arc furnace and oxygen slag in the Civil Construction Industry, mainly as base, subbase and asphalt covering in highways. However, independently of the type of recycling, a period of "cure" of about six months is necessary. Because of this slow cure process this byproduct may turn non-competitive in some regions if compared, for example, with the natural aggregate. The objective of this work is to present the flowsheet of the slags production as a residue both at the electric and oxygen steel plants and, through a bibliographic review, to analize the possibilities and limiting factors for the use of steelmaking slags in the Civil Construction Industry.

Jan 1, 1996

By Herbert Pöllmann

Waste disposals are needed for safe deposition of different kinds of materials which can not be used as secondary raw materials. Often high contents of heavy metals must be bonded tightly to cristalline compounds to protect the environment from contamination. Therefore it is important. to find minerals which are capable to incorporate different heavy metals and protect the ground water. The power of resistance against leaching out effects of highly water-soluble salts can be increased. Mineral groups of metal hydroxy salts, ettringites, apatites, sodalites and calciumchlorosilicates and their hydrates are recommended for their formation in mineral reservoirs. Different wastes as red mud, gasification ash, garbage combustion ash and fluidized bed ashes were included in this study. The formation of different new compounds and their properties were determined.

Jan 1, 1991

By Huimin Lu, Liyuan Zhao, Zhijiang Gao

The aluminum matrix composite reinforced by graphene was successfully fabricated using high pressure torsion (HPT). With only 0.5wt% graphene, the grain size was reduced to 100nm while that of pure Al was about 500nm. The hardness of the composite increased from the center (64HV) to the edge (120HV) of the sample. Moreover, the tensile strength of this composite reached 197MPa, while that of pure Al was 157MPa. The enhancement in mechanical properties was induced by grain refinement, load transfer from the matrix to the reinforcement and dislocations piled up at the grain boundaries.

Jan 1, 2015

By G. L. Pedroti

With the development of industrial processes and the consequent emergence of numerous products that quickly become necessities, industrial activity has acquired an essential character today. Although its importance is unquestionable, industrial activity is responsible for generating quite a large number of residues, with different shapes and characteristics. It has been observed, in particular the grits (Kraft process in the cellulose industry) and the residue from the processing of granite. And, given the importance of Portland cement as a building material, its vast employment and waste properties that resemble components of the clinker, it was decided to produce cementitious compounds from these industrial wastes. The residues were subjected to mineralogical, chemical, physical and morphological. And, the mixing ratio between the residues in the 70% and 30% grits residue granite was sintered at 1250 ° C furnaces to burn threshold of 6 hours forming new compounds observing tri-calcium aluminate and di-calcium silicate that are compounds found in portland cement.

Jan 1, 2015

By Denise Crocce Romano Espinosa, Andrea Moura Bemardes, Jorge Alberto Soares Tenorio, Daniella Cardoso Buzzi, Tatiana Scarazzato

"In copper plating processes, a fraction of raw materials are incorporated to the final products, while other portions are discarded as effluents. In this study, the application of electrodialysis (a membrane treatment process) was studied for treatment of wastewaters from cyanide-free strike baths, in order to reuse the components of this bath: copper and HEDP. The synthetic solutions studied consider 1 % of ion concentration of the bath used in this process, simulating the rinsing waters to be discarded. The electrodialysis allowed a percentage extraction up to 73% of copper ions and 72% of HEDP from the effluent. Complexes formation between the acid and copper indicates the possibility of recovery of components in the same compartment, obtaining a concentrated solution of these substances that can be reinserted in the process, for compensating drag-out losses. A diluted solution is also obtained, that can be reused as water in rinsing tanks.IntroductionIn metal finishing industries, contaminants in wastewater and the type of treatment required are determined according to the type of operation [l]. Generally, electroplating industries employ conventional wastewater treatments, e.g. oxidation of cyanide and chemical precipitation. This stage promotes reactions with soluble compounds to produce an insoluble precipitate, removed by physical separation. The sludge is dried by press-type filters [2].In this manufacturing sector, part of the raw materials are discarded as hazardous waste. The cost of discarded compounds and the treatment and disposal of waste may compromise profit margins. In addition, water consumption per unit of production stimulates the development of methods able to recover and reuse the largest possible amount of water [3].In some plating processes, cyanide-based substances are used as complexing agents and as raw materials in form of metal salts [4]. However, the toxicity associated with cyanide has been promoting research for the development of new raw materials in plating processes.A study conducted in Brazil [4] evaluated the modification of a commercial cyanide-free bath for processes of copper coating on Zamak. In the performed study, a new alkaline copper bath was formulated using l,hydroxyethane-1,1-diphosphonic acid (HEDP), an organic compound known for forming stable complexes with metal ions.As results of the study, the operational conditions and the formulation of a bath to obtain adherent, uniform and bright layers were established (Table I) [4]."

Jan 1, 2014