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By G. Upadhya

Of late, solidification modeling has progressed considerably to emerge as a viable simulation tool for the foundry engineer. A wide variety of tools exist in the commercial market to cater to the various needs of the design/ foundry engineer. In fact, recent developments in the area of solidification modeling have been so rapid that a comprehensive review of the state-of-the-art is very much needed. In this paper, an attempt is made to summarize the various issues of solidification modeling, at the same time addressing the historical evolution of the subject. The various phenomenological issues covered in this paper include: heat transfer, fluid flow during mold-filling, solidification kinetics and microstructural evolution, quick-analysis schemes for approximations, porosity prediction models, and the phenomena of fluid flow in the mushy zone. Modeling issues related to the development of solidification stresses which lead to defects such as hot tears and the development of artificial intelligence concepts in the area of rigging design are also discussed. Due emphasis is given to the various phenomena which add to the complexity of the whole subject, and the various alternatives available for solving a particular problem. For example, the heat transfer problem can be approached by the use of simple modulus schemes or by solving the conduction equation to obtain a more accurate temperature distribution. Similarly the microstructural evolution can be handled in a deterministic way by use of nucleation and growth models, or in a probabilistic way by use of empirical models. The main goal of this paper is to put the multi-faceted problem of solidification modeling in proper perspective so that it can serve as a guide for future developments in this area.

Jan 1, 1994

By C. W. Whitten

Solis from an abandoned Pb battery processing facility were characterized prior to the selection of the extraction technique. Reflected light microscopy and electron beam methods were used to locate Pb-bearing phases and to quantify the compositions of the phases. It was found that the soils are composed primarily of quartz and feldspars with minor amounts of iron and titanium oxides. Lead is primarily present as an oxide or sulfate that is associated with the silicate minerals. Specific phases identified were PbO; Pb02; cerrusite, PbCO3; angleslte, PbSO4; galena, PbS; and magnetoplumbite, 2PbO3Fe2O3; or plumboferrite PbO2Fe2O3?

Jan 1, 1989

By Shengli Wu, Wei Huang, Xinliang Liu, Kaifa Zhang

The slagging behavior, the phase of primary blast furnace slag and its transformation law of structure for the single furnace burden were studied in this paper. The results showed that the formation of primary slag was controlled by CaO/SiO2, Al2O3 content, MgO content, reducibility, iron content and porosity of the furnace burden. Fayalite (2FeO•SiO2) was easily formed from acid ferrous furnace burden while kirschsteinite (2(Fe,Ca)O•SiO2) was produced from alkaline ferrous furnace burden

Jan 1, 2015

By Hyun Kyu Shin, Byeong Deok Lee, Young Eun Lee

The reduction of Mn oxides at pre-smelting steps is an integral part of smelting processes for Mn alloys, and an understanding of its reaction mechanism is expected to contribute to the improvement of processing efficiency for Mn alloys smelting. The phase diagram shows that five Mn carbides are operative in the Mn-C system. Although they are expected to participate in the reduction of Mn oxides, no specific information is available yet to clarify their roles in presmelting carbothermic reaction of Mn oxides. Experiments with composite pellets prepared with Mn oxides and graphite powders show that Mn3O4 is reduced initially to MnO at about 1130oC and, subsequently, to Mn7C3 carbide as temperature increases further. At 1331oC, Mn7C3 carbide dissociates to Mn alloy and carbon. The degree of reducing reaction increases with increasing carbon balance in composite pellets and increasing temperatures.

Jan 1, 2014

By G. B. Harris

Much has been written over the past decade concerning the disposal of arsenic from metallurgical processes. In Canada, there are proposed regulations which would classify arsenic in the Primary Group of twenty one persistent, toxic pollutants to be banned or phased out. Since many nickel and cobalt ores, not to mention those of copper, gold and uranium, contain significant amounts of arsenic, it is pertinent to assess the current state-of-the-art of its disposal. The literature is reviewed, and it is demonstrated that from a purely chemical point of view, the family of ferric arsenates largely immobilize arsenic. There is clear evidence from laboratory studies that both crystalline ferric arsenate (scorodite) and amorphous ferric arsenates in which the molar Fe/As ratio is at least three (Fe/As = 3) have very low arsenic solubility; plant data are given to support this. The debate over the long term stability of these compounds continues however; the evidence presented for long term stability and for compound breakdown is critically reviewed in the light? of the recent structural studies, and the role of base metals in these compounds evaluated. Finally, conclusions are drawn as to the viability of a purely chemical process for the long term disposal of arsenic from metallurgical processes.

Jan 1, 1993

By Jesse White, Tyler Salisbury

Research projects contain many stages of development from the conception of an idea to a fullscale commercial operation. The transition from laboratory-scale research to bench-scale roasting can represent a significant increase in complexity and cost, depending on how many variables are being evaluated. Thermogravimetric analysis (TGA) can simulate roasting conditions and produce a small sample for chemical analysis or materials characterization. A simultaneous thermogravimetric and differential scanning calorimetry (TG–DSC) can identify endothermic and exothermic reaction temperatures. Using thermal analysis, some of the process variables can be tested and eliminated such as ore and reagent blends, retention times, operating temperatures, and some atmospheres.

Jan 1, 2015

By Baokuan Li, Qiang Wang, Zhu He

"A mathematical model has been developed to investigate the magnetohydrodynamic (MHD), thermal, and solidified behavior in electroslag remelting process. Based on the finite volume method, a multiphase coupling MHD approach is employed to investigate the droplet formation as well as movement in molten slag under the action of an alternating current. The VOF formulation is adopted for interface tracking. The electrical potential method is adopted for the electric current and magnetic field. The Electromagnetic force and Joule heating are recalculated at each time step and then is implemented in the momentum and energy equations as a source term, respectively. Moreover, solidification of the metal is described by an enthalpy-based formulation, while the mushy zone is treated as a porous medium with porosity equal to the liquid fraction. The model is used to investigate the effect of electrode tip shape on MHD, thermal, and solidified behavior and provide valuable information.IntroductionElectroslag remelting (ESR) process has been used widely to produce high-performance alloys dedicated to critical application, such as hot work tool steels, nickel base alloys, the manufacture of components in aerospace and landbased turbines, etc. Figure 1 shows a schematic diagram of ESR process including a consumable electrode, a molten slag pool, a liquid metal pool, a solidified ingot, and a water-cooled mold. Alternating or direct current flows from the electrode to the water-cooled baseplate through the high resistivity calcium-fluoride-based molten slag which result in Joule heating and Electromagnetic force (EMF). Part of the Joule heating melts the electrode and the droplets travel through the slag and accumulate the liquid metal pool. The electrode is continuously advanced into the slag as it melts to build up an ingot of improved structure and composition by controlled solidification and chemical refinement. The metallurgical properties of the remelted ingot are really related to the solidification structure, which strongly depends on magnetohydrodynamic, thermal, and solidified behavior in the molten slag, liquid metal pool, and mushy zone."

Jan 1, 2014

By Hiroshi Tabuchi, Akihiko Takahashi

"High strength aluminum matrix composites were prepared and studied using as reinforcement newly developed nearly mono-dispersed a-alumina single crystal particles each of which has a regular polyhedral shape. The composites were formed by centrifugal casting using aluminum casting alloys (Al-Si and Al-Cu-Mg) as the matrices, followed by heat treatment. The volume fraction of the alumina particles was as high as 60%. The same matrix composites reinforced by conventional crushed fused alumina particles were similarly prepared as the reference. The bending strength and tensile strength of the Al-Cu-Mg matrix composites reinforced by the novel alumina particles of 10 µm in average diameter are as high as 1020 MPa and 560 MPa, respectively, which are higher than those of the conventional alumina composites. Furthermore, the bending strength of the novel alumina composites degraded less than that of the conventional alumina composites after thermal fatigue tests. The number of cracks in the matrix seemed to influence the thermal fatigue property because many cracks were observed in the conventional alumina composites, whereas only a few cracks were observed in the novel alumina composites. This was confirmed by SEM observation of the sample composites before and after the thermal fatigue tests.IntroductionAluminum matrix composites strengthened by dispersed reinforcements are of interest for various applications due to their improved properties, such as high specific strength and stiffness, wear resistance, etc .. A large number of investigations have been made concerning fabrication processes and properties of these composites. With regard to the fabrication processes, powder metallurgy has been well-known as a solid phase process, and recently many liquid phase processes such as a compocasting, a squeeze casting, the Lanxide process, and the Osprey process have been studied and developed.(1)"

Jan 1, 1998

By S. Gopalan, J. D. Milshtein, S. N. Basu

Production of syngas is proposed utilizing the W/W03 redox system and employing a solarpowered two-step thermochemical cycle. Three chemical reactions occur in two chambers. Assisted by a solar concentrator, a high temperature reaction reduces W03 powder to metallic tungsten in both chambers. Subsequently, the temperature in one of the chambers is lowered and H2(g) is produced via re-oxidation of the tungsten powder using steam. The temperature in the other chamber is simultaneously lowered to an intermediate temperature and CO(g) is produced via oxidation of the tungsten powder using C02(g)· The gas streams coming out of the two chambers result in the syngas production. A complete thermodynamic analysis of the system is described. The W/W03 redox cycle offers greater gravimetric fuel productivity compared to previously proposed systems, and the entire cycle can be operated below 1273K.

Jan 1, 2013

By Honggang Zhong, Tan Yi, Qijie Zhai, Zhao Dan, Xinping Mao, Huigai Li

"The influence of superheat degree on the distribution and volume content of inclusions were studied in 65Mn thin slab produced by compact strip production(CSP) in Zhujiang Steel in China, The results showed that the diameters of inclusions are mainly less than 5µm. Most of the inclusions gathered at the 1/4 thickness direction for the thin slab of 27? superheat degree, compared with the center position for that of 37?. There are more inclusions larger than 50µm in the low superheat samples, which is caused by the short floating time. In addition, the inclusions were observed and analyzed by metallurgical microscope, SEM and EDS in order to ensure their composition, type and further find their source. It was find that the types of these inclusions mainly are Al2O3, SiO2,CaO and their composites, a few of them are TiN and MnS.IntroductionIt is well known that inclusions have a great impact on the strength, plasticity, fracture toughness, cutting performance, fatigue property and corrosion resistance of steels. Especially, with the demand for thinner slab, the cleanness is increasingly becoming more significant as a quality criterion[1]. High manganese and carbon steels not only demonstrate high strength but also proper plasticity. There are many problems unsolved for 65Mn steel as a result of the low solidification rate, bad thermal strength, crack sensitivity and low casting temperature[2,3].The superheat of the molten steel has a great impact on the erosion of refractory lining, molten steel fluidity and non-metallic inclusion behavior[4]. The serious erosion situation of ladle lining, nozzle and casting tundish will give rise to more inclusions at a high superheat. Meantime higher superheat will make second dendrite arm spacing coursing and element segregation which lead to inclusion, bubble formation and shrinkage cavity. On the contrary, it is hard for non-metallic inclusions to float up with a low superheat value. Inclusions of 65Mn steel, which produced in different superheat condition by CSP, were studied for the sake of higher slab properties including statistics and EDS analysis."

Jan 1, 2012

By Jintao Gao, Zhancheng Guo, Chong Li

A new approach to enrich MFe and RO phase from the converter slag by super gravity was investigated. The samples obtained by the gravity coefficient G=600 and cooling rate V=5K/min from 1623K to 1373K appeared significant stratification and the MFe gathered at the bottom of sample. With the help of metallographic microscopy and X-ray diffraction, it is found that large quantity of white RO phase gathered at the lower part of the sample as the concentrate, with volume fraction appearing gradient distribution along the direction of super gravity, while the upper part was mainly composed of dicalcium silicate as the tailing. The mass fractions of the FeO, MgO and MnO in the concentrate are up to 40.46%, 6.9% and 3.91%, while that in the tailing are just 11.65%, 2.15% and 1.55%. The recovery ratios of FeO, MgO and MnO in the concentrate are 60.35%, 58.45% and 72.24%, respectively.

Jan 1, 2016

By G. D. Sandrock

The science and technology of roan temperature rechargeable metal hydrides began about 1969 with the discoveries that the intermetallic Compounds LaNi5 and TiFe could be, conveniently hydrided and dehydrided at roan temperature and modest H2 pressures. Subsequently, this lead to the development of a broad family of REE-containing AB5 hydrides and numerous applications that make use of the extraordinary H2-absorption and reaction-heat properties of these materials. Some of the applications include H2 storage, compression and separation, as well as heat pumping, heat to mechanical energy conversion and electric energy storage. This paper briefly reviews the fundamental phenomenology of metal hydrides, the history of the use of REE's in rechargeable metal hydrides, the practical engineering properties of these materials and the applications that have evolved around them. The rechargeable nickel metal hydride battery, a new vial alternative to NiCd cells, stands at the forefront of the applications.

Jan 1, 1992

By Raymond M. Coveney

Bedded sulfide ores in Cambrian Chinese black shales typically contains at least 2% Ni, 4.5% Mo, 1% As and 0.2% Se. Thin laminae and replaced on colites from the ore contain intimate mixtures of fine-grained Ni-rich sulfides and jordisite complicating ore treatment. The ores contain abundant jordisite, vaesite, nickelian pyrite, and barite and lesser amounts of sphalerite, gersdorffite, millerite, tennantite, fluorite, chalcopyrite, and HgSe (probably tiemannite). At present only ores that are sufficiently rich (>4.5% Mo) for direct roasting are mined and treated to produce, ammonium molybdate. The ores contain Pt, Pd, and Au in amounts totaling up to -2.5 ppm, but these are not recovered.

Jan 1, 1993

By M. Waladan

The top submerged lancing Sirosmelt system has been developed through laborator.y scale testwork and pilot plant trials for recovery of zinc from ISF slag. The effects of the process variables of gas injection rate, method of coal feeding, and temperature on zinc fuming rates were studied in the laboratory. It was found that the rate of zinc elimination was dependent on all of these variabl.es. The rate of zinc removal from slag was independent of zinc content of slag down to approximately 1.5% Zn, below which the rate was proportional to zinc content in slag. Pilot plant trials were carried out to evaluate a proposed process and results followed predictions from the laboratory scale tests. A comparison of the proposed process with conventional slag fuming operations is made and it is shown that the process has a number of advantages which have a significant impact on the economics of zinc slag fuming.

Jan 1, 1990

By W. K. Connor, O&apos

The U.S. Bureau of Mines, in cooperation with the Idaho National Engineering Laboratory (INEL), conducted over 30 hours of melting tests to vitrify simulated low-level radioactive wastes from the INEL Radioactive Waste Management Complex (RWMC). Five separate waste compositions were investigated, each consisting of noncontarninated soil from the RWMC and surrogate materials used to simulate the actual buried wastes. The RWMC soil and five waste compositions were melted in a 50-lb, single-phase electric arc furnace with a water-cooled shell. These tests were conducted to determine melting parameters in preparation for a large-scale melting campaign to be conducted in the Bureau's 1-metric ton (mt), water-cooled-wall, 3-phase electric arc fumace. Bulk chemical composition was determined for each of the feed materials and for the slag, metal, fume solids, and offgas furnace products, and distributions were calculated for the key elements. The material balance for the furnace operation indicates that from 63 to 84 pct of the feed reported to the slag. Cerium, used as the surrogate for the radionuclides in the wastes, demonstrated an extremely strong affinity for the slag product. Although slag temperatures as low as 1250° C were recorded when melting the RWMC soil, temperatures in excess of 1600° C were necessary to achieve the fluidity required for a successful slag tap.

Jan 1, 1994

By N. A. Warner

Fundamental studies on the reaction of limestone or dolomite at high temperature with S02 are extended to the realm of large scale primary copper smelting. Whereas flue gas desulfurisation in the electric power utility industry is concerned with S02 concentrations normally less than 0.5 percent, high temperature smelting gases can have S02 levels approaching 100 percent. The reaction involved is very exothermic so proposals are made in this paper for returning the heat generated in sulfur fixation directly back to the copper smelting process. This integration leads to metal production with lower energy requirements than current technology. The anhydrite reaction product can either be disposed of locally with minimum adverse environmental impact or upgraded to a value-added product. It is assumed, of course, that no viable market exists to support sulfuric acid production.

Jan 1, 1996

By Ma Lijuan, Zhang Yubing, Wang Bo, Sun Huilan

The effect of lime ratio on phase composition and alumina leaching property of MgO-contained calcium aluminate clinker were investigated by analytical reagent, the XRD analysis of its mechanism was discussed. The results showed that: when the sintering temperature was 1350 ℃, C/A was 1.4, A/S was 1.3 and the content of MgO was 4%, the increase of the C/A promoted the formation of C12A7 and restrained the formation of Q-phase. The alumina-leaching ratio of the clinker (A/S was 1.3) was increased from 74.33% to 91.34% when the content of CaO was 5.21%.

Jan 1, 2015

By George J. Karcas

"Non-ferrous metals such as copper, nickel, lead, zinc and precious metals are produced via the electrorefining and electrowinning processes. Apart from controlling electro-chemical conditions for the production of these metals, there has always existed the challenge of controlling the corrosive effect of the electrolyte environment which serves as the medium for non-ferrous metal production.The practice of acid containment in electrometallurgical operations has entered the world of high technology with the advent of advanced acid resistant materials such as vinyl ester resin which is either combined with aggregate to form polymer concrete or used to line various acid containment vessels and ·surfaces. ill comparison to some Asian, European, and African copper refineries, the North and South American copper industry has recently embraced quite heavily in the use of polymer concrete electrolytic cells and process vessels, such as electrolyte storage tanks, and in the use of vinyl ester resin for corrosion protective surface sealing 'systems in lieu of epoxy, acrylic and other materials because of its combination of higher corrosion resistance and superior flexibility.Electrolytic cell construction has undergone a transformation from a multiple part configuration to a single piece moulded/cast unit. ·The one piece moulded polymer concrete cell, which has been patented by Corrosion Technology International, with the overflow, decant, inlet, fast fill and segregation systems integrally designed is now the industry standard.. The combination of a wood, steel, or concrete frame with a lining made of lead, asphalt, rubber or plastic has been historically successful in providing limited protection from chemical and mechanical attack in electrolytic cells and electrolyte storage tanks all over the world. These combinations have now become obsolete as materials such as polymer concrete provide exceptional corrosion and mechanical protection with greatly reduced maintenance requirements and improved efficiency and productivity for the tankhouse. ill addition, polymer concrete can be disposed of in a regular land fIll which is much less costly than disposing of contaminated concrete that is normally associated with conventional lined concrete cells."

Jan 1, 1997

By Jie Li, Shu Yang, Zhongliang Tian, Xun Hu, Yanqing Lai

The purity of the electrolyte has an important influence on the content of the impurities in electrodeposited silicon. In this paper, effects of electrolysis temperature, current density and the time on the concentrations of two important impurities: phosphorus and iron in the electrolyte were investigated during the purification of Na3AlF6-10%K2SiF6-AlF3 melt. It was observed that the concentrations of P and Fe in the electrolyte decreased with the electrolysis temperature, current density and the electrolysis time increasing. X-ray fluorescence (XRF) of the electrolyte shows that the concentrations of P and Fe decrease from 4.2ppmw to 1.3ppmw and 204.0ppmw to 42.6ppmw, respectively. The removal rates of P and Fe are 69.08% and 79.12% when the electrolysis was performed for the duration of 3 hours and at a current density of 20mA·cm-2 while the operating temperature was 1225K.

Jan 1, 2015

By Sun Ying, Zhang Jing, Li Qiuju

A new process of enrichment Cu in molten copper slag under electric field is presented in this article. The experiments were carried out in the laboratory on a kilogram scale. The mobility of copper slag was improved by the technique of carbon reduction. The effects of temperature, electric field strength and intermittent feeding speed were investigated on Cu migration. The results showed that the best experimental conditions were the temperature at 1523K, electric field strength was 1.5V•cm-1 and feeding rates was 15 g•(10min)-1. The copper content of the slag decreased below 0.6wt%. The process was compared to the traditional electric furnace process of slag cleaning, there was reduced the energy consumption and heat loss, and also harmful gas emissions such as SO2 and CO2, accompanied by improved the efficiency of slag cleaning.

Jan 1, 2016