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By Y. H. Wang, S. Kou

"Three-dimensional weld pool convection was computer simulated using dimensionless variables. The electromagnetic force, the buoyancy force and the surface tension gradient on the pool surface were treated through the use of the dimensionless electromagnetic force, the Grashof number and the Marangoni number. Other typical dimensionless numbers such as the Prandtl number and the Peclet number were also used. The calculated and experimentally observed fusion boundaries were compared. The convection patterns were shown and the effect of the Marangoni number was demonstrated. IntroductionSeveral weld pool convection models have been developed by Oreper et al. (1,2), Chan et al. (3) and Kou et al. (4). These models describe two dimensional convection in stationary weld pools in a semi-infinite workpiece. Since the vast majority of arc welding practices involve a moving heat source and weld pool, and the workpieces are finite in thickness rather than semi -infinite, a 3-D convection model for a moving heat source and a workpiece of finite thickness is expected to be much more useful.Weld pool convection can strongly affect the structure and properties of the resultant welds. Variations in weld characteristics which are likely to occur from changes in weld pool convection are: weld penetration, macrosegregation, gas porosity, solidification structure, undercutting and surface smoothness. Apparently, the quantitative understanding of convection and heat flow in weld pools is of considerable practical interest. Mathematical models describing convection and heat flow in weld pools are essential, not only because of the quantitative understanding they provide, but also because of the difficulties associated with the experimental measurements of weld pool convection. These difficulties are mainly due to the fact that only surface flow, rather than the overall convection pattern in the weld pool, can be observed. In fact, due to arc glow even the observation of surface flow can be rather inconvenient."

Jan 1, 1986

By Dr. -Ing. Wolfgang Pietsch

Many primary metallurgical wastes are in the sh.-ape of turnings; borings, chips, dusts, and other particuletes. While such. materials can be easily segregated and/or upgraded to yield high quality ?secondary metals with often known composition for easy recirculation into the production? process; their particulate nature results in various problems. Roller presses are used in an ever increasing number for size enlargement and densification of primary particulate metallurgical wastes for secondary metal recycling. The paper will mention the areas of application from A(luminum) to Z(ink), also including Brass; Cast Iron, lead, and Stainless Steel, as well as dusts from all types of melting and ladle furnaces or converters. Typical systems using roller presses for size enlargement. will be discussed.

Jan 1, 1995

By Gregor Kücher

Lack of basic knowledge on the semi-direct recycling methods for hard metals hinders the application on an industrial scale. However, advantages like reduced expenses and lower environmental impact draw interest at future potentials. Consequently, this report aims to offer insight into the influence of varying bulky hard metal substrates during their lixiviation in acidic media with an oxidant. The statistical software Modde 11 assisted in the development of a design of experiments (DOE) for evaluation of the impact of average grain size, binder and tantalum carbide (TaC) content on the leaching characteristics. The other experimental parameters were constant. Among them were temperature, solution concentration and quantity, duration and substrate surface exposed to liquid volume. Eventually, prediction plots and factors of the computed model equation describe the effects of varying substrate qualities on leached binder metal and selectivity.

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 Marcio B. Fonseca

Nickel-cobalt laterite deposits have become the focus of attention for hydrometallurgical processing. Following the lessons of the second generation high pressure acid leach (HPAL) projects in Western Australia other Ni-Co laterite projects are now evaluating potential HPAL projects with a rigorous integrated approach that begins with geological modeling, resource estimation and metallurgical studies. The Vermelho nickel-cobalt laterite deposit has been under exploration and study for several years with investigations of various metallurgical processes. Recent HPAL studies have indicated that the nickel and cobalt laterite at this deposit is amenable to upgrading by silica rejection followed by pressure leaching. These studies have required a detailed geological investigation to generate a new resource model. The recent development of a sophisticated geological model integrated with a multi-element resource estimation for this complex tropical nickel laterite deposit in northern Brazil provides an example of the contribution of geology at the critical project stage where process technology decisions are made on relatively small samples of the total resource.\ Keywords: Ni Laterite, Geological Modeling, Resource Estimation

Jan 1, 2004

By K. Sarveswara Rao

The present paper firstly describes some recent trends from literature on energy management via process intensification to arrive at sustainable technologies for aqueous processing of minerals, metals and materials. Secondly, the energy saving measures practiced in leaching, solid-solution separation, solution purification, metal and material winning and environmental aspects have been discussed. The emerging importance of interdisciplinary nature of hydrometallurgy for practical applications is also highlighted. With the above background, the present paper describes an overview of energy conservation and autoclave processes with a special reference to hydrometallurgical research activities of our Laboratory.

Jan 1, 2008

By Hartmut Rossel

VAW aluminium AG has built a "Recycling-Technikum" (Recycling Research Centre) to add a new arm to the company's Corporate Research and Development Department. The Recycling Research Centre, a pilot plant for scientific research, has been in operation since September 1993. These state-of-the-art facilities allow the investigation and optimisation of recycling techniques in 'a global way and in detail. Research is concentrated on the unit operations - processing, melting and waste-gas purification - with the available installations making it possible to compare different alternative process combinations on a 100-kg scale. One of the main targets of VAW research is the development of recycling techniques for packaging. The paper presents an approach to recover the aluminium contained in flexible packaging materials using an integrated melting and waste-gas purification system.

Jan 1, 1995

By Tom Lewis

This report discusses the evaluation of the ENVIRO-CLEAN PROCESS, a technology developed by Lewis Environmental Services, Inc. for the recovery of metals such as chromium, mercury, copper, cadmium, lead, and zinc from surface and groundwater streams. This new heavy metal removal process (patent-pending) utilizes granular activated carbon with a proprietary conditioning pretreatment to enhance heavy metal adsorption combined with electrolytic metal recovery to produce a saleable metallic product. The process generates no sludge or hazardous waste and the effluent meets EPA limits. A 50 gpm system was installed for recovering hexavalent chromium from a ground water stream at a site located in Fresno, California. The effluent from the activated carbon system was reinjected into the ground water table with the hexavalent chromium concentration < 10 ppb. The system simultaniously removed trichloroethylene (TCE) to concentrations levels < 0.5 ppb. The activated carbon is regenerated off-site and the chromium electrolytically recovered. The full scale system has treated over 5 million gallons of ground water since installation.

Jan 1, 1996

By K. Krishnapisharody

The phenomenon of slag droplet formation under the action of gas-stirring in steel ladles has been analyzed with experiments conducted in a thin-slice room-temperature model using water and mineral oils as the working fluids. Visual and video investigations have been performed on the interface behaviour along with measurements of liquid velocities in both phases, using the Particle Image Velocimetry (PIV) technique. The measured velocity data and observations on the interface break-up establish that the droplet formation results primarily from an instability mechanism at the interface.

Jan 1, 2008

By H. -Peter Sattler

The laser sorting technique for replacing the handpicking of the non-ferrous metal scrap from auto shredders was first introduced 1990, The process is based on the use of atomic emission spectroscopy induced by lasers to identify the scrap particles and sort them with adequate systems into main fractions of Al-, Zn-and Cu-alloys, stainless steel and lead, In the meantime the handling technique for the scrap, i.e. the singling and sorting technique as well as the analytical detector were further developed for more efficiency and higher reliability, i,e. less maintenance, minor sorting errors etc. These developments were mainly based, on and initiated by operational experiences from the startup phase of a first production plant. Part of the on going research work was the development of an ,aluminium detector which makes it the first time possible to sort mixed aluminium scrap automatically into specific alloy fractions.

Jan 1, 1995

By Björn Lindquist

Boliden has developed a number of specialised technologies for smelter gas handling and effluent treatment. These technologies will be described. Special attention will be given to the high-pressure venturi, Editube wet electrostatic precipitator, mercury removal processes, and two-stage effluent treatment.

Jan 1, 2002

By Dariusz Kopyci ski, Józef Dorula

The study proves that by introducing the iron powder and disintegrated steel scrap to low-sulphur cast iron still before the inoculation carried out with a conventional graphitising inoculant, the mechanical properties similar to those obtained during the inoculation treatment carried out on cast iron with the recommended high sulphur content are achieved. The said operation increases the number of crystallisation nuclei for dendrites of the primary austenite. In this case, the iron particles act as substrates for the nucleation of primary austenite, due to a similar crystallographic behaviour of the regular face centred cubic lattice The more numerous are the dendrites of primary austenite, the less free space is available in the interdendritic spaces for the formation of graphite eutectic grains, which makes the structure more refined (more eutectic grains) and the mechanical properties higher.

Jan 1, 2016

By Yong-ming Chen, Chao-bo Tang, Yun Li, Long-gang Ye, Sheng-hai Yang, Hao-tian Xue

In order to achieve high recovery of Cu and Co during cobalt-bearing copper sulphide ore smelting process, reducing agent (coke) and sulphidizing agent (pyrite) were added into molten smelter slag for reducing-sulphidizing smelting to product Cu-Co matte. Effects of reductive atmosphere, pyrite dosage, smelting temperature and smelting duration on Cu, Co, Fe distribution behaviours were investigated. The results show that the distributions of Cu and Co are mainly enriched in Cu-Co matte, and the distribution ratio, LCu and LCo, improve with increasing of coke amount or pyrite addition, whereas above 6 wt.% coke or 20 wt.% pyrite, Cu and Co tend to transfer from matte to cleaned slag. A properly high temperature(1300) and smelting duration(3h) are beneficial to the enhancement of the distribution ratio of valuable metals, and under the given set of conditions, LCu > LCo generally. However, an undesired high Fe contents in matte limit further increase of LCu and LCo.

Jan 1, 2015

By Yongqi Sun, Zuotai Zhang

Our study investigated the influence of P2O5 and B2O3 on the viscosity and crystallization behavior of Ti-bearing blast furnace (Ti-BF) slags for the purpose of Ti extraction. The investigation of the crystallization behaviors were carried out using a single hot thermocouple technique (SHTT) and the viscosity was obtained by rotating cylinder method. For the viscosity, the results showed that P2O5 substantially increased the slag viscosity. P2O5 is a network-forming oxide, which increased the degree of polymerization of slags and accordingly increased the slag viscosity. However, both of slag viscosity and apparent activation energy for viscous flow remarkably decreased with B2O3 addition. As a typical network forming oxide, B2O3 was introduced into the network and existed dominantly as 2-D structure, BO3 triangular, which caused a simpler structure and a decreasing slag viscosity. As for the crystallization behaviors of Ti-BF slags, both P2O5 and B2O3 enhanced the crystallization trend of rod-shape rutile and suppressed the crystallization trend of dendrite CaTiO3. Therefore the added P2O5 and B2O3 caused the primary phase change from CaTiO3 to rutile. Additionally, it was found that the rod-shape rutile showed a 1-D growth, whereas the dendrite CaTiO3 showed a 3-D growth style.

Jan 1, 2015

By Cong Wang, Siyang Long, Pengcheng Zhang, Haibin Zuo

The present study describes central segregation of the High-carbon steel billets of 150mm square and its heredity to the following hot-rolled wire rods, whose sizes are 10mm and 6.5mm in diameter separately. The relationship between center segregation of the billets and solute element distribution of rods, the mechanical properties and microstructure of rods were studied experimentally. The results show that segregation index of C is higher than that of Mn. With the increase of central segregation, the stability of the mechanical property of the rods becomes worse. The formation of carbide network and central martensite in the rolled products can be attributed to the heredity of the as-cast central segregation. The 6.5mm-diameter-rod has higher tensile strength than that of 10mm diameter which might be due to bigger reduction ratio. Thermo Mechanical Control Process (TMCP) should be used together with Billet Centersegregation- controlling (BCSC) to improve the overall properties of rolled products effectively.

Jan 1, 2016

By Wenjun Duan, Qingbo Yu, Qin Qin, Junxiang Liu

In the study, the coke-oven gas (COG)-steam reforming process using hot blast furnace slag (BFS) as the heat carrier is explored for producing hydrogen and recovering high-grade waste heat of hot BFS. The method of the Gibbs energy minimization approach through Lagrange multiplier is adopted in the thermodynamic analysis of reforming process. The simulation is carried out to study the operation pressure, temperature and steam to carbon ratio (S/C) based on the chemical equilibrium calculations. The optimal operation conditions are determined to improve the yield and fraction of hydrogen in the COG-steam reforming process. The results suggest that the preferential operation conditions for COG-steam reforming process to produce hydrogen are achieved at 600ºC, 1.5MPa and S/C (5.0). Due to the CaO and other melts in BFS, CH4, CO and CO2 in COG are converted and removed efficiently, especially CO2. The hydrogen fraction reaches to 86.7% and its production is about 1.22mol with 1mol of the COG.

Jan 1, 2016

By Bart Blanpain, Tom Peter Jones, Muxing Guo, Liugang Chen, Huayue Shi

Fayalite based slag is formed during the smelting process of secondary copper resources. It was found that with the presence of high ZnO, the slag became viscous, causing a slag tapping problem. In the present paper, the phase relations of the slag system ZnO-“FeO”-SiO2-Al2O3- CaO (ZnO = 0-12 wt%, Al2O3% = 0-15 wt%, CaO = 0-1.5 wt%, with iron saturation) at 1150 °C is studied by using quenching technique followed by phase identification and compositional analysis of equilibrated samples. The dependence of FeO and Al2O3 solubility in the liquid slag on the chemical composition of slag is characterized. Based on the experimental data, the solid fraction of the slag, which may considerably, influences the slag viscosity, at the tapping temperature can be reasonably estimated and, therefore an appropriate modification of the slag composition can be made.

Jan 1, 2016

By Deepu Philip, Pratik Agarwal, Ajay Kumar Shukla, Ishani Shukla, G Rajesh

Steel plants generally employ static BOF end point control models to arrive at a given temperature and chemistry at the end of blow. These end point models have now been supplemented with chaos control models to steer the blowing process in the right direction while the blow is in progress. Merely arriving at the correct end point temperature is however not adequate because in the subsequent stages as well the temperature variations can be large and unpredictable. The present paper deals with an integrated model to take into account the effect of all parameters affecting temperature and composition from tapping to the start of casting to minimize the use of LF or aluminum heating, and also minimize grade mixing. The application of lean operations strategy is explained in which the previous “Push System’ is changed to a “Pull System”, minimizing the use of ladle furnace or aluminum heating during steelmaking.

Jan 1, 2014

By Nobuaki Sato, Tetsuo Fukasawa, Akira Kirishima

To apply the fluoride volatility process for the treatment of fuel debris formed in the damaged nuclear reactors, study on the fluorination behavior of main constituents, such as fuel and cladding is essential. The mixture of uranium and zirconium oxides is formed under severe conditions such as high temperature and oxidizing atmospheres. In this paper, fluorination and volatilization behavior of uranium and zirconium oxides have been studied by TG-DTA method in the presence of fluorine. From the TG-DTA result of UO2 in F2 atmosphere, the weight gradually increased up to 7% at 350 oC followed by rapid weight decrease with exothermic peak showing the vaporization of uranium as UF6. ZrO2 showed similar fluorination behavior to that of UO2. However, fluorination of UO2-ZrO2 seemed to be suppressed with increasing ZrO2 amount. This may be caused by the formation of solid solution.

Jan 1, 2016

By Qingyun Huang, Junyi Xiang, Xuewei Lv, Chenguang Bai

The extraction of vanadium from mechanically activated converter slag was studied in dilute sulfuric acid solution. The effects of roasting and leaching parameters were investigated. The results show that Ca/V mole ratio, roasting temperature, leaching temperature, liquid-solid ratio, and particle size all have significant effects on vanadium leaching efficiency from calcification-roasted converter slag.

Mar 1, 2017