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By Basant L. Tiwari

An electrolytic process, based on a three-layer concentration cell, to extract magnesium from commercial aluminum alloy scrap has been examined. The process was repeatedly tested at 1025 K with two cells of d1fferent sizes, 0.6 kg and 5 kg feed aluminum, to have a better understanding of the opera ting parameters and evaluate the scale-up potential. In both cells, the magnesium content of the scrap was selectively reduced ?from 1. 1 to less than 0.1 wt.% at anodic current dens-Hy as high as 1. 1 A/cm2 with current efficiency exceeding 85%. Magnesium was recovered in the form of salt coated globules. Comparison of performances for the two cells suggests that the process can be scaled up. With further development, this process could become a viable alternative for demagging secondary aluminum.

Jan 1, 1985

By You-Hai Wen, Yinkai Lei, Tian-Le Cheng

A phase field model is developed to simulate the performance of SOFC electrodes. By solving the conduction equations on both the electrolyte and electrode phases, and incorporating the three-dimensional microstructure and reaction front at triple phase boundaries, the current-voltage relation of an electrode is directly simulated. By further coupling it to our recently developed coarsening model, we are able to investigate the effect of initial microstructure on the performance degradation in SOFC electrode. This model is applied to LSM-YSZ cathodes with different LSM volume fraction. The volume fraction effect on the electrode performance and its degradation rate has been analyzed and discussed.

Mar 1, 2018

By Ing. R. Geutskens

Zinc-bearing dust from blast furnace gas-scrubbing operation is a well known environmental health problem in the iron and steel industry. Hoogovens IJmuiden (The Netherlands) developed processes to solve this problem. 90% of the zinc is concentrated in 25% of the dust (the fine particle fraction) by means of slurry-hydrocyclonage. The resulting fine particle fraction is treated in a pressure leaching process. Hydrochloric waste pickle liquors have been used as a leaching liquor. By creating optimal leaching conditions more than 98% of the zinc is brought into an acid' solution, whereas nearly all the iron remains in the residue. The zinc can be separated selectively from the solution. The residue can be reused in the blast furnace (via the sintering plant). In the article information is given about the research work and -results of the pressure leaching process as well as the possibilities of the process for solving comparible problems.

Jan 1, 1990

By K. Fagerlund

Methods for simulation of settler reactions, matte-slag separation and matte settling in copper flash smelting have been examined. The reaction, separation and settling phenomena of slightly oxidized chalcopyrite samples and cuprous sulfide-magnetite mixtures in fayalite type slags were examined at about 1300°C under inert atmosphere. Two methods based on introduction of molten samples of oxidized chalcopyrite concentrates or synthetic matte-magnetite mixtures onto the surface of molten iron silicate slag were tested. In the first method the samples were water quenched and polished specimens were studied and analysed using light optical microscope, scanning electron microscope, energy dispersive spectrometer. In the second method processes taking place after the introduction of samples onto the slag are followed "in situ" using X-ray transmission image monitoring. Great differences were observed in separation and settling behaviour of low and high grade copper mattes produced as a results of interaction of initial samples and slag.

Jan 1, 1997

By Animesh Jha, Chris Dometakis

"Without the use of a flux, only a poor dispersion of ceramic phase can be achieved. A molten-flux-assisted ceramic phase dispersion technique for producing aluminium alloy metalmatrix composites has been developed. In this paper, we report the physical chemistry for the dispersion of TiB2 in molten aluminium. In particular, aspects of the interfacial energy and the thermodynamics of the dispersion reactions are briefly discussed for enhancing the volume of dispersion phase in the molten metal and for controlling their morphology. This investigation also addresses the role of molten flux in the fabrication of AI-alloy mmc using a casting technique. The morphological aspects of the dispersion are explained on the basis of the classical theory· of nucleation.IntroductionMetal matrix composites (MMCs), have long been recognised as an important class of material due to their greater wear resistance, specific stiffness and temperature capability when compared to conventional monolithic alloys. Particulate reinforced composites produced by melt casting techniques have been amongst the first MMCs to achieve commercial market viability. The advent of melt mixing techniques such as the Duralcan™ process have enabled low cost, easily fabricated composites based on the AI-SiC and AIAlz0 3 systems to be produced. In this process, uncoated ceramic particles with diameters 10ltm and larger, are incorporated into conventional monolithic alloys with reinforcement levels up to 25 volume percent. The AI-7Si-SiC metal-matrix composites have good wear resistance, high strength, low density and high thermal conductivity. The combination of these physical and mechanical properties has become a major attraction for the fabrication of light-alloy composite disc rotor brakes for the automotive sector2. However, in silicon-free alloys, SiC is thermodynamically unstable above the composite melting point and is extensively attacked by the melt to form aluminium carbide3 :"

Jan 1, 1996

By V. A. Luganav

The behavior of arsenopyrite under heating has been studied by many scientists. It has been already established that under heating at more than 650°c and without air access the arsenopyrite dissociates with the formation of one atom arsenic. Under vacuum the dissociation process begins at 5500C with the formation of elemental arsenic. The residue of dissociation process contains pyrrhotite and throilite. In the presence of pyrite, arsenopyrite dissociates under lower temperature and with a higher velocity than without it. The industrial realization of fool scale processing of arsenic bearing raw materials is possible only by the use of standard equipment and oxygen containing blast. In this view the paper presents the results of the study on the effect of oxygen in the gaseous phase and its addition into the charge of pyrite in the process of arsenopyrite decomposition. Thermodynamic analyses showed that under thermal processing of arsenopyrite in the presence of pyrite and limited quantities of oxygen in the gaseous phase the formation of arsenic sulfides is possible according to the following reactions:

Jan 1, 2003

By M. Wenzel, Dang Thanh Tung, Nguyen Anh Duc, Nguyen Huu Luong, Dang Van Sy, N. Kelly, K. Gloe, K. Kretschmer, Phuc Nguyen Le, K. Schnaars, S. Robles M, L. Götzke, J. J. Weigand

The recovery of rare earth metals from secondary sources has attracted much attention due to their ever expanding demand in the high-tech industry. The studies reported here focus on the hydrometallurgical recovery of lanthanum and cerium from spent fluid catalytic cracking (FCC) catalysts in a two-step process: leaching with nitric acid and solvent extraction by tri-n-butyl phosphate (TBP) and di(2-ethylhexyl)phosphoric acid (D2EHPA). The experiments show a high dissolution yield of about 93% lanthanum and 42% cerium in a single leaching step with 2 M (126 g/L) HNO3 at 80 °C; only 11% aluminum has been dissolved simultaneously. In the subsequent solvent extraction step the best results for this leach liquor could be achieved using a 1:1 mixture of 25% (v/v) TBP (0.92 M) and 25% (v/v) D2EHPA (0.76 M) in n-decane without the need for any pH adjustment. In that case La(III) and Ce(III) can be extracted with 60% and 74% yield respectively in one stage from the majority of accompanying matrix elements. In particular no extraction of Al(III) could be observed under these conditions.

Jan 1, 2016

By Takao Yasugi

The majority of copper in the raw material migrates to the de-copperized dross that forms when the crude lead produced in the blast furnace is treated in the de-copperizing process. The de-copperized dross is treated in the electric furnace producing matte, speiss, and crude lead. The de-copperized dross also contains the silver. Therefore, it is important to improve the rate of silver migration to the crude lead. For this reason, the behavior of silver between the matte, speiss and crude lead phases was examined. At the same time, several tests to improve the percentage of silver migrating to crude lead were conducted.

Jan 1, 2003

By Hongxu Li, Zhaobo Liu, Zihan Zhao

A completely new process of selectively recovering Sc3+ without impurity of Fe3+ from Bayer red mud was developed. Prior to water leaching process, red mud needs to be digested and sulfated at a low temperature and subsequently roasted at a higher temperature for a period of time. During the roasting process, the products such as SO2, SO3 and H2SO4 molecules of thermal decomposition of sulfites including NaFe(SO4)2 and NaAl(SO4)2 could be recycled and reused as the raw materials of sulphuric acid. The leaching results indicate that roasting temperature and roasting time are the main constraint on selective leaching performance of scandium. As the sulfated red mud sample is roasted at 750 degrees C for 40 min and subjected to water leaching at 50 degrees C for 30 min, 53.0 wt% Sc3+, <1.0 wt% Fe3+, <0.3 wt% Si4+ and ~8.9 wt% Al3+ could be leaching out. Of note, the solid-liquid separation process is quite easy to be carried out.

Mar 1, 2017

By Carlos A. Nunes

V-AI alloys have been used commercially to produce pure vanadium by Electron Beam Melting (EBM), as well as to obtain Ti-based alloys (ex. Ti-6AI-4V). The aluminothermic reduction of vanadium pentoxide (V205) is the primary method to obtain these alloys. Concerning the obtention of pure vanadium, earlier studies have indicated alloys presenting Al content between 10 and 15wt% as the most suitable alloys for direct EBM. In the present work we investigated the aluminothermic reduction of V205 in order to define process parameters for the obtention of V-AI alloys with composition in the previously mentioned range. It was studied basically the effect of excess AI, CaO addition and reaction atmosphere (air, argon) on the alloy composition (AI, 0, N). In addition, microstructural analysis of selected alloys by SEM (BSE images) and EPMA (WDX) were also performed.

Jan 1, 1996

By B. R. Baldock

The converting of high-grade nickel matte for production of low-sulphur matte or nickel metal is a process which has eluded metallurgists in the past because of the limitations of conventional converting furnaces. The high temperatures required and the refractory nature of nickel oxide has prevented practical success in a process which has been known to be theoretically feasible for a long time. The Ausmelt top submerged lancing system is capable of operating under close control of the smelting conditions. High temperatures and both rapid oxidation and rapid reduction can be achieved. These features have provided the basis for successful pilot plant trials of the desulphurisation of high-grade matte from the Kalgoorlie Nickel Smelter. Sulphur level in product was lowered from 20 to 25% to as low as 0.2%, with iron levels in matte in the range of 1.0 to 3.5%. The theoretical background of matte desulphurisation is surveyed and the pilot plant operations described. The implications of the results in relation to commercial plants and possible refinery operations are summarised.

Jan 1, 1993

By A. V. Reddy, C. Beckermann

"The DC continuous casting of a grain refined AI-4.5%Cu round ingot with realistic boundary conditions is numerically simulated. Of particular interest are the effects of the transport of free solid in the form of equiaxed grains on the macro segregation patterns and the final grain size distribution. The study uses a previously developed two-phase model that incorporates descriptions of heat transfer, solute redistribution, melt convection, and solid transport on the system scale with microscopic models of solutal undercooling, microsegregation and grain impingement. The numerical results indicate that grain transport inhibits the formation of inverse segregation in the ingot shell and promotes negative centerline segregation. This is explained by the reduction in the solid coherency next to the mold and the advection of solute-lean grains towards the centerline. Comparisons with the experiments of Finn et al. [5] illustrate the need for considerable improvements in the model. IntroductionMacrosegregation continues to be one of the concerns in DC continuous casting of aluminum ingots. The variation in composition over the ingot cross section results in the need to adjust alloy composition in order to meet mechanical property specifications in finished products. The extent of macrosegregation is greatly affected by the casting conditions, such as casting speed, superheat, cooling rate, mold size, alloy composition, and grain refining practices. Thus, it is of great interest to develop a comprehensive mathematical model to simulate the casting process, enabling the selection of conditions that minimize macrosegregation while maintaining a high productivity."

Jan 1, 1994

By Shengli Wu, Juan Zhu, Wei Huang, Xinliang Liu, Kaiping Du, Kaifa Zhang

Based on the furnace burden of high content of Al2O3, the process of softening and melting and the characteristic of primary slag were studied with the increase of MgO content in the sinter and adding some MgO into the pellet. The results showed that the content of MgO in the primary slag increased with the increase of MgO in the sinter and pellet. Meanwhile, the permeability of the furnace burden was improved because of low viscosity of high MgO primary slag. Compared with the increase of MgO content in the sinter, the increase of MgO content in the pellet can improved the softening and melting characteristic of the comprehensive furnace burden more effectively. More Mg-bearing pellet should be chosen in the comprehensive furnace burden for the purpose of improvement the fluidity of primary slag and the permeability of the furnace burden in the burden of high Al2O3 content.

Jan 1, 2015

By Yuzhe Zhang, Xiaodi Huang, Xinli Wang, Bowen Li, Matthew Andriese, Xin Yan, Jiann-Yang Hwang, Zhiwei Peng

Using a TM0n0 cavity system as the main reactor, an integrated process was developed to find the best condition for waste tire rubber to absorb microwaves. The penetration depth was the main character for determining the best condition. The penetration depth is defined as the distance from the surface into the materials at which the traveling wave power drops to from its value at the surface. The waste tire powder was irradiated by two different microwave frequencies, including 915 and 2466 MHz. The study was conducted with same powder size and atmospheric condition. The effects of temperature and microwave frequency were analyzed based on the experimental data. The main trends are higher the temperature, the absorption will be better and the higher the frequency, the better the absorption will be.

Mar 1, 2017

By Tetsuro Ohashi, Tooru Matsumiya, Yoshio Abe

"The three-dimensional deformation of a continuously cast slab was modeled into two-dimensional deformation by developing the solidified shell of the slab. The developed solidified shell was divided into rectangular elements. The thermal strain produced as the slab is wi thdrawn over one roll spacing in the casting direction was calculated from the temperature change during that time and the increment of the geometrical unbending strain during the time was calculated from the change in the radius of curvature of the slab by assuming that the neutral axis of bending is located at the mid-thickness of the slab and that the transverse section of the slab is kept in a plane during unbending. These strains were imparted to each element as initial strains. The interaction between the elements and the overall deformation of the solidified shell were analyzed by the finite element method.The analysis was performed on a slab being cast on a machine of the circular arc type with progressive unbending. The following findings were obtained as a result. The effect of unbending is spread in the upstream and downstream directions of the slab by the shear deformation of the narrow and wide faces. As the shear deformation increases, the strain in the unbending zone decreases and the strain outside of the unbending zone increases. The effects of secondary cooling conditions, slab size, radius of caster circular arc section, compression casting, etc., were also analyzed. IntroductionTo develop a method for preventing the internal cracking of continuously cast slabs, it is important to acurately analyze the deformation of the slab and this subject has been extensively investigated. Many researchers, including the present authors, have analyzed slab bulging. (1)- (11) Analysis has also been made of thermal deformation that assumes importance in continuous casting of small-section blooms.(12)-(18) However, unbending deformation, an extremely important subject for continuous casters of the circular arc type, has not been fully analyzed."

Jan 1, 1986

By Zhihe Dou, Guozhi Lyu, Liping Liu, Yi Luo, Ting-an ZHANG, Xijuan Pan, Zhuolin Liu

Due to the high energy consumption, long technical process, low usage rate of vanadium during the traditional smelting vanadium steel process, a new method for decarburization by CO2 to directly smelt vanadium-containing steel in blast furnace was proposed. In this paper, the thermodynamics of CO2 decarburization in molten iron process was calculated out by FactSage. The thermodynamic calculations indicated that in standard state, the transformation temperature of C and V was 1357 °C; the oxidation order of element was Si, C, V, Mn and S when using CO2 as oxidant. The experiment of blowing CO2 temperature showed that decarburization reaction temperature was 1550 °C, carbon content could be decreased to 0.676%, the decarburization rate was 88%. There was no effect on vanadium content in molten iron during the decarburization process, vanadium content was 0.323%, which meets the request of vanadium mould steel.

Mar 1, 2018

By Yifei Zhang, Jianzhong Li, Wenhao Zhang

Eletrochemical behavior and corrosion properties of a Ti–6Al–4V alloy fabricated by selective laser melting in artificial seawater at temperature ranges from 20 to 40 °C were investigated using electrochemical techniques, including potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky measurement, etc. Equivalent circuits were simulated to investigate alloy surface and analytic effects of temperature on interface of alloy and solution. The results showed that corrosion potential increased with temperature rise, and the EIS presented a single capacitive resistance characteristics. When the temperature reached 35 °C or above, passive current increased, while the passivation phenomenon was not obvious and corresponding radiating arc radius reduced, indicating that the resistance decreased, conductivity of surface passivation film improved, and corrosion performance improved. According to the Mott-Schottky curves, alloys exhibited n-type semiconductor characteristics. With increasing temperature, conductivity of passivation film enhanced, and alloy corrosion resistance decreased. At 40 °C, alloy possessed the worst corrosion resistance.

Mar 1, 2018

By Y. Yang, S. Peelman, J. Sietsma, Z. H. I. Sun

The rare earth elements (REEs) present in the Kiruna iron ore mine tailings are being considered as a new REE resource for the EU. These tailings, after beneficiation, contain approximately 5000 ppm of rare earths, concentrated in apatite and monazite minerals. To economically extract the REEs from these tailings the phosphorous contained within the apatite must also be extracted and the waste production of the process should be minimal. To achieve the extraction of REEs and phosphorous HCl and HNO3 were investigated as possible leaching agents. Based on the results a leaching process using HNO3 is proposed. This process produces H3PO4 from the apatite while simultaneously dissolving the REEs. The resulting leach liquor is then cooled to remove the unwanted Ca as Ca(NO3)2. Analysis of the leach liquor reveals extraction ratios of between 75% and 100% for the heavy REE (e.g. Y, Eu, Dy, …) and below 40% from the light REEs (i.e. Ce, La). Full phosphorous extraction was also achieved.

Jan 1, 2016

By R. E. Moore

The lining systems currently in use in BOF furnaces, certain steel ladles, and the slag line of electric are furnaces were developed during the late seventies through the mid-eighties using a trial and error method of combining aggregate, carbon sources, additives and binders. They are currently based on magnesia, graphite, metal additives and resin binders, the selections of each being tied to the anticipated intensity of the use conditions. The general functions of the respective constituents are well appreciated, however, there is still a great deal that is not known about how the socalled antioxidants protect the graphite nor how impurities from the graphite and the aggregate enter into the wear processes. In a simplified assessment of wear processes, it appears that if the deoxidized layer can be kept very thin, less than 810 mm in depth, and if the viscosity and quantity of the matrix glassy phases can be controlled to resist erosion of the deoxidized layer, lining life can be maximized for the various applications. This paper will discuss the characteristics of the starting materials systems currently being employed for applications requiring a deoxidation function to realize extended wear. It will not attempt to explain all the complex interrelationships between the respective constituents but will point to the potential for improvements through the use of improved constituents.

Jan 1, 1991

By Do-Hyeong Kim, Tae-Jung Kim, Seung-Yeon Won, Jong-Jin Pak, Min-Kyu Paek

Liquid iron alloys containing V, Mo, and Ni can be produced by the carbothermic reduction of spent catalysts used in petrochemical industry. Thermodynamics of carbon in these alloy melts is important for refining these alloys. In the present study, the carbon solubility in Fe-V, Fe-Mo, Fe-Ni, Fe-V-Mo, Fe-V-Ni, Fe-Mo-Ni and Fe-V-Mo-Ni alloy melts of various compositions was measured at 1873 K. The temperature dependency of vanadium effect on carbon solubility in liquid iron was also measured in the temperature range from 1823K to 1923K. The additions of vanadium and molybdenum significantly increased the carbon solubility in liquid iron alloys while nickel decreased the solubility. The experimental results were thermodynamically analyzed using Lupis’ relation at constant activity to determine the first- and the second-order interaction parameters of vanadium, nickel and molybdenum on carbon at carbon saturated condition. Using thermodynamic parameters determined in the present study, the carbon solubility in Fe-V-Mo-Ni alloy melts of various composition were accurately predicted and verified experimentally at 1873 K.

Jan 1, 2014