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By Ping-Ping Fan, Yong-Quan Wu

The polarized Brillouin scattering spectra were systematically measured to study the elastic properties of bulk hexagonal close-packed (hcp) ZnO single crystal in this paper. The peak polarizations of all modes in spectra were analyzed firstly. The elastic properties, such as the whole set of Elastic constants were accordingly calculated and compared with the previous literatures. Also investigated were the effects of the rotation of the sample in the (0001) plane perpendicular to the z axis on different acoustic modes. The results show that the quasi-longitudinal and quasi-transverse modes perpendicular to the (0001) plane act as the expected trigonometric function of the rotation angle,while the longitudinal and transverse modes on the (0001) plane remain constant.

Mar 1, 2017

By Shanlu Yang

In this study, laser-GTAW hybrid welding was used to the lap joint of galvanized dual-phase (DP) 980 steel in a gap-free configuration. The effects of welding parameters such as the laser power, the distance between the laser beam and the electrode torch, the arc current on the quality of hybrid welds were fully studied. The reason for the formation of different weld defects arises from the development of the highly-pressurized zinc vapor at the interface of two metal sheets. Experimental results demonstrated that the elongated molten pool introduced by the GTAW can suppress the formation of spatters to some extent. However, the hybrid laser-arc welding process still suffers from a large amount of spatters that degrade the weld quality. Furthermore, it was found that the weld quality was enhanced with the increase in the laser beam-arc distance and welding current.

Jan 1, 2009

By Chuandong Wei, Mao Chen, Baojun Zhao, Zhixiang Cui

The first bottom blown copper smelting furnace (BBF) has been successfully operated for 10 years at Dongying Fangyuan Nonferrous Metals. In addition to many advantages of the BBF reported previously, stable operation with spinel-containing slags enabled the BBF refractories to achieve three-year campaign life. Understanding of the degradation mechanisms of the magnesia-chromite refractory will be able to further prolong the service life of the refractories and develop new refractories. In the present study, the post-mortem refractories were collected from different locations of the BBF during the annual maintenance. It is the first systematic study for the used refractories of a BBF. The phases present in the refractories and their compositions have been determined by Electron Probe X-Ray Microanalysis. The degradation mechanisms of the refractories are discussed based on the analyses. The results will be used to optimize the operation and select proper refractories in the furnaces.

Mar 1, 2018

By S. N. Monteiro, E. B. Zanelato, J. Alexandre, M. T. Marvila, A. R. G. Azevedo, G. C. Xavier

One of the parameters used in the study of mortars is the adhesion resistance, which indicate show much the mortar adhered to the substrate. The usual study is done at 28 days, to worldwide standardization. Few researchers study the adhesion of mortars to ages other than 28 days. In this scenario, the adhesion strength tests of conventional mortar with a 1:1:6 mass scale (cement, and sand) at 7, 14, 28, 56, 91, 182 and 364 days were performed in order to understand the behavior of this material. The usual characterization tests of the mortars were carried out to correlate the values obtained with the adhesion results. The obtained results demonstrate that the mortar continues to gain resistance with the passage of time. For the trait studied the gain was considerable, indicating that over time the cement continues to hydrate, reacting and contributing to the strength of the material.

Mar 1, 2018

By Shusen Cheng, Kun Yan

An elastic-plastic stress mathematical model of hot blast stove shell has been established in order to investigate the stress distribution and deformation of the shell. The results show that stress concentration happens along the intersection line of hot blast stove body and the hot blast manifold. The plastic deformation occurs on the hot blast outlet in blast period. The deformation degree of the hot blast shell near the blast outlet in blast period is much larger than that in combustion period. In blast period, the shell near the blast outlet elongates along the horizontal direction and shortens along the vertical direction, the shell near the outlet deforms into an oval. And in combustion period, its deformation isn’t obvious. The repeated deformation of the shell near the outlet between different periods may cause the refractory brick damage and be harmful to the long campaign life of hot blast stove.

Mar 1, 2017

By Carlos Maurício F. Vieira, Gabriel Oliveira Glória, Maycon Sidney Gomes de Camargo, Sergio Neves Monteiro, Fábio da Costa Garcia Filho, Maria Carolina Andrade Teixeira, Frederico M. Margem

The society is increasingly the concern about the ambiental impacts, and demand for eco-friendly materials. The composites reinforced with synthetic fibers are been replaced by composites reinforced with natural fibers because of the environmental advantages. Besides the environmental advantages, those fibers have economical and properties advantages, like the low density and cost. Composites with up to 30%of PALF fibers were tested. The analyzed parameters were the loss modulus, the storage modulus and the delta tangent. The test was conducted in the temperature interval from 25 to 195 °C in a DMA equipment operating at 1 Hz of frequency under a nitrogen flow. The results showed that the incorporation of continuous and aligned PALF fibers tends to increase the viscoelastic stiffness of the epoxy matrix. Contrasting this, minor changes occurred in both the glass transition temperature and the damping capacity of the structure as measured by the tan delta peaks.

Mar 1, 2018

By A. Raraz

The optimization of the plutonium electrorefining process has been studied on the basis of modeling and model materials. The plutonium electrorefining process has been reviewed and the basics of the electrorefining process with molten salts as electrolytes and under forced convection has been presented. The definition of the problem in plutonium electrorefining has been related to three factors and this research has addressed these three factors to provide an insight to this process. The hydrodynamic factor gives information on the behavior of the mechanically stirred system. The chemical stability and solidification factor shows the interactions among the components of the electrorefining cell. The electrochemical factor is oriented to study the efficiency of the electrorefining process on the basis of limiting current density, stirring rate and configuration cell. As a result of this study the optimization of plutonium electrorefining implies mainly a re-design of the cell.

Jan 1, 1995

By Xinhua Wang, Qiangqiang Wang, Yubin Li, Shusen Li, Lifeng Zhang

"Numerical simulation on the fluid flow in a Flow-Control Mold (FC-Mold) were performed. The motion of inclusions were calculated. With FC-Mold, the flow pattern and surface velocity become more symmetrical, and at higher casting speed the velocity of liquid steel in the top region of the mold was largely reduced with the highest velocity of the meniscus reducing from 0.65 mis to 0.4 mis, and the meniscus shape became flatter. With FC-Mold, more inclusions approached to the surface of the slab and the amount of inclusion in the center of mold became fewer. Larger inclusions were easier to remove, however, the EM filed of the FC-Mold could hardly improve the removal of inclusions from the molten steel.IntroductionElectromagnetic brake technology is an effective method to control the flow pattern within continuous casting mold, together with other casting parameters, nozzle design and mold geometry [1-5]. Due to the interaction between the applied magnetic flux and the conductive molten steel inside the mold cavity, a force is generated in the direction opposite to the jet flow, which can decelerate the high speed steel jet from the SEN ports. The potential benefits include fewer surface and internal defects, fewer inclusion especially at higher casting speed. However if used imperfectly, electromagnetic forces can have opposite effect [6]. Numerical models are the best tool to optimize electromagnetic flow control. In the current study, numerical simulation was performed to investigate the flow field in a continuous casting FC-Mold, and the effect of different operation parameters on the flow, surface level and velocity in FC-Mold were discussed."

Jan 1, 2013

By Laszlo Kadar, J. D. Lavers

"In the continuous casting of aluminum killed steel, the tundish nozzle often experiences clogging problems. Water model studies have shown that the clogging problem is dependent on the flow pattern in the nozzle entry region. In particular, the flow can separate at the entrance to the nozzle, leading to the development of a recirculation region. Although a nozzle can be designed such that no recirculation develops, even a small misalignment from the vertical positioning of the nozzle may render the design ineffective.To reduce the possibility of nozzle clogging, the recirculation zone must be reduced or eliminated. This may be achieved by moving the fluid downwards or raising the turbulence level in the separation region. In the case of a tundish nozzle, it is proposed that this can be achieved by using electromagnetic forces.To generate the required electromagnetic force, two systems are considered. The first is based on injecting a DC current; the second by using electromagnetic induction. Both methods are described in this paper. Order of magnitude calculations are provided to illustrate that both methods are essentially feasible. The performance of each method in terms of modifying the turbulent flow characteristics in the nozzle entry region is then examined using a numerical model. It is shown that both methods can greatly reduce the recirculation zone. A cylindrical nozzle was chosen for the model studies since it represents a worst case situation.On the basis of the model studies, it can be concluded that whereas both of the proposed methods have the potential to reduce the troublesome recirculation zone, the induction method appears to be simpler in terms of practical implementation."

Jan 1, 1999

By Tian Sugui

By means of the measurement of the enduring property and microstructure observation, an investigation has been made into the influences of the element Re and TCP phase on the enduring property of the single crystal nickel base superalloys. Results show that the needle-like TCP phase is precipitated along the <110> orientation on {111} planes in Re-containing/free superalloys during the long term aging, the TCP phase is identified as µ phase, and the precipitated µ phase in 4.5%Re alloy is gradually spheroidized during aging. Thereinto, the needle-like µ phase may obviously decrease the enduring lifetimes of the alloys due to the consumption of the refractory elements and the effect of the stress concentration. But the stress concentration is not easily generated in the regions near the spherical-like µ phase, which is a main reason of reducing the enduring lifetime of 4.5%Re alloy to a small extent.

Jan 1, 2010

By J. L. Liow

Studies have been carried out on the causes and effects of slopping in an annular cylindrical geometry such as the top submerged combustion reactor. Properties of standing waves formed such as the wave profile, period, pressure distribution and velocity have been derived analytically. The wear profile due to wave erosion was calculated based on the assumption of linear motion and that the wear is a dissolution process. The use of the j, factor showed that the wear was proportional to the square root of the wave velocity at any point. Using the dimensions of the lsasmelt reactor given by Errington et al. (1987)[11, the wear profile due to wave erosion was calculated using the analytical solution. The wear profile calculated was shown to have a maximum just below the initial bath surface. The wear was found to be concentrated in the region where the first asymmetric standing wave was most active. The results showed that the refractory near the bath surface will be affected by wave erosion, more so than any other parts of the reactor. The contribution of wave erosion on wear must be accounted for in assessing the total refractory wear of a vessel in which slopping exists.

Jan 1, 1991

By Uday B. Pal

In the electrochemical vapor deposition (EVD) process, gaseous cation precursors are passed over one side of a porous substrate, and oxygen is passed on the other side of the substrate. The gases diffuse and react within the porous substrate, and the pores get filled with the desired solid oxide. Subsequent solid state electrochemical transport through the solid oxide in the pores continues the reaction, and the film grows over the porous substrate. The EVD process has been used to deposit lanthanum chromite interconnection films and yttria stabilized zirconia electrolyte films over porous air electrodes. The EVD growth of these solid oxide films is found to be parabolic in nature, which indicates that the solid state transport (diffusion) of ions through the film controls the growth. This solid state transport can be analyzed using Wagner&apos;s treatment of the electrochemical transport. Conductivity measurements and the information on the defect structure of the oxide can be combined with the EVD growth rate measurements to calculate the solid state transport properties (transport numbers and partial conductivities) of the rate-controlling minority species in the oxide. Using this approach, the EVD growth of other electronic, mixed conducting and ionic solid oxide films can also be analyzed.

Jan 1, 1992

By Ian Masters, Saul B. Davies, David T. Gethin

The purpose of this model is to simulate and analyze the energy flows within a rotary aluminum recycling furnace, using the global properties of its main components, the gas, metal and refractory walls. The model will simulate a series of operations such as loading, heating and stirring which will constitute the processing of a batch. Each main component of the furnace is treated as a one-dimensional heat transfer medium, the thickness and area of each medium being calculated from the actual geometry of the furnace. The physical properties are taken as the weighted average of those for the various layers forming the medium. Incorporated into the model are elements describing the radiative exchange within the furnace, melting of the charge, and forced convection in the melt due to the rotation of the furnace. This approach has produced a model with a reasonable computing time that can be used to run a whole series of simulations for the prediction and comparison of the furnace performance under different operating conditions.

Jan 1, 2000

By Susumu Okabe

Mitsubishi Continuous Copper Converter employs the top blowing lance system for the continuous supply of reaction gases into the molten bath. In order to avoid the excessive refractory wear caused by the melt splash without loss of the reaction efficiency, the furnace design and the blowing condition should be optimized. Empirical equations which correlate the splashing rate on the&apos; side wall with the dimensions of the furnace, lance position, lance size, gas velocity and bath properties were obtained by by the physical model study, and compiled into a computer program. The computer program is effectively utilized for the analysis of the actual operation and for the optimum design of new furnaces.

Jan 1, 1998

By Kent D. Peaslee, Lifeng Zhang, Edith Martinez, Yufeng Wang

The current study investigated the multiphase fluid flow, heat transfer, solidification of the steel, and the motion and entrapment of inclusions during the centrifugal casting process using FLUENT software. User-defined functions (UDFs) were developed to add velocity with a value related to the rotation speed and radial distance to the solidified steel, to exert a centrifugal force to the motion of inclusions, and to add the entrapment condition of inclusions at the solidifying shell and export the entrapment locations of the inclusion. The calculation shows that there are two peaks of inclusions along the thickness of the produced tube: one at close to outer surface and another one close to the inner surface of the tube. With a larger rotation speed, inclusions tend to be entrapped more towards the inner surface. The calculation agrees well with the industrial measurements.

Jan 1, 2012

By Greg Dowling, Jun Ge, George Shannon, Shufeng Yang, Yongfeng Chen, Lifeng Zhang

"Inclusions in 316L stainless steel ingots poured using two different upgate designs – a traditional upgate and a swirl upgate - were investigated using SEM and ASPEX automated inclusion analysis. The main inclusions were high SiO2 inclusions, MnS inclusions and SiO2-Al2O3-CaO inclusions. More inclusions were detected at the top of the ingot than other places in vertical direction, and more inclusions were at the edge of the ingot than other place in the radial direction. With swirling upgate there were more K- and Na- bearing inclusions than that with the traditional upgate indicating possible more serious flux entrainment with the swirl upgate.IntroductionIngot casting still is very important for production of special steel grades including high carbon chromium bearing steel, thick plate, seamless tube, forgings, bars, and wire rods [1] . During the bottom teeming process, molten steel enters the trumpet and passes through the spider into the runners. Molten steel then enters the ingot mold through an upgate near the end of the runner. In the early stages of filling a mold, a mold flux bag hung in the mold were burnt and the mold flux will cover the top of the rising steel to protect the steel from being reoxidized, acting as well as act as a thermal insulator. So far, some efforts on studying inclusions characteristics in the ingot have been reported. A review paper on the control of inclusions during steel ingot casting was published by Zhang et al. [2] Zhang also studied Inclusions in bottom-teemed ingots of plain carbon steel and found that the >20µm inclusions originated from either the entrainment of mold flux of the reoxidation during teeming process. [3] The results of Nagendra and Du showed that there were more inclusions in the centre part of the ingot [4]. Eriksson et al reported that the composition of inclusions was more complex in the mold samples in comparison to the ladle samples, and more inclusions in the mold were found than in ladle because of the reaction between the mold flux and the molten steel [5]. It was reported that SiO2-CaO-Al2O3 inclusions originating from mold powder with reoxidation product Al2O3 as a part, and there were more inclusions close to the side wall than the center of the ingot in the radial direction. [6]. A more recent investigation showed that four main types of inclusions in runner samples were classified: oxides, sulfides, complex and carbon-nitrides. [7] The flow pattern in the mold during filling has been found to be an important factor regarding inclusions in the ingot. In the early stages offilling a mold, steel enters the mold through the entry nozzle at a high velocity. The effect of the resulting turbulence on the meniscus can lead to the entrainment of mold flux. Efforts have been paid over the years to find methods to reduce the velocity of the molten steel entering the mold, such as using opening angle of the inlet nozzle [8], using swirl blade at the runner [9], using a divergent nozzle combined with a swirling flow generated in the nozzle [10-11]."

Jan 1, 2012

By Gerald Onyedika, Tochi Onwumere, Martin Ogwuegbu

"The kinetic study for the leaching of iron from cassiterite ore in KOH solution was studied. The effects of KOH concentration, particle size and reaction temperature on the leaching rate of iron were also examined. The results of leaching studies showed that the leaching of iron from cassiterite ore in KOH solution is significantly influenced by the reaction temperature, KOH concentration, and decrease in particle size. The study showed that 90.62% of iron ore was leached in 8M KOH solution at 80°C within 120 minutes. The experimental data were well evaluated using the shrinking model for surface chemical reaction and diffusion control through the product layer. The activation energies for the iron ore dissolution using the two models were calculated to be 32.06KJmor1 and 97.97 KJmor' respectively.IntroductionIn recent times, there has been increasing attention on the kinetic study of mineral dissolution. In most of these studies, the experimental results were analyzed with a suitable shrinking core model under the assumption that the ore is a homogeneous spherical solid phase [1-4]. A study of the dissolution kinetics of a Nigerian cassiterite ore by hydrochloric acid showed that increase in the hydrochloric acid concentration is accompanied with increase in the amount of cassiterite ore dissolved at various times [4]. The optimal concentration was found to be 4.0M HCl, after which there was a decline in the amount of the ore dissolved, which showed that the concentration of the reagent has a significant effect on the leaching rate of the ore. Also in studying the effect of stirring speed on the rate of cassiterite ore dissolution while keeping other conditions constant for 120 minutes, the result showed that the rate of cassiterite ore dissolution was dependent on the stirring speed over a range of 0 to 630 rpm. Above 360 rpm, the stirring speed no longer had any effect on the solid dissolution. The dissolution rates of cassiterite were analyzed using a suitable shrinking model. The results showed that the reaction was controlled by the diffusion of tin through the porous product layer, a reaction order with respect to hydrogen ion concentration of 0.92 M and activation energy of 50.05KJmor'. In another kinetic study on the leaching of a low grade niobium-tantalum ore with concentrated KOH solution the effect ofreaction temperature, KOH concentration, agitation speed, particle size and alkali-to-ore mass ratio on the dissolution rate of niobium were examined [5]. The result of niobium leaching from low grade niobium-tantalum ore with concentrated KOH, solution at different agitation speeds showed that the dissolution rate increased with increase in agitation rate. In the case of particle size effect, the results show that small particles require much shorter time for complete dissolution than the large ones."

Jan 1, 2013

By Andre Krzysik

"Fluidized bed technology has been used in the industry for almost 100 years. To fully understand the process hundreds if not thousands of researchers were and are involved in finding the way to predict the behavior of the solids when subjected to the flow of media through them and the conditions of the solids in the fluidized state. The difficulties in predicting the behavior of solids in the fluidized state stem from the complexity and abnormality of the parameters related to the solid particles. Theoretical calculations can in some degree account for some of them. Particle size distribution, their shape, density, moisture content and physical and chemical reaction that may exist in the fluidized bed reactor play an extremely important role and influence the behavior of the fluidized bed. This paper focuses on the practical examples of the fluid bed equipment and the use of different conditions to process various products.IntroductionEach process application has its own unique requirements and the designers of the equipment must take into consideration specific process requirements, specific properties of the material to be processed (both physical and chemical), and physical and chemical reactions/changes that are taking place in the reactor (heat and mass exchange, chemical reactions, isomorphic change etc.). Each individual piece of equipment must also satisfy specific requirements/ preferences of the client that will operate and maintain the equipment. Those often represent greater challenges than the process on its own, and are equally important to the satisfactory operation of the plant. That includes aspects like location of the equipment, environmental effects, and expected life of the equipment, process control, access, maintenance, and many others.Over the period of time a great deal of research, both theoretical and practical have been carried out and the results of that work are available for equipment designers. For the simple applications that information is usually sufficient and the selection of a suitable solution is relatively simple. In many instances, the available information is not sufficient, and often specialized test work needs to be conducted to obtain additional data. In many cases a pilot installation is built in which the required process is tested. Only then the commercial equipment is designed. The following deal with specific installations that were designed to satisfy specific requirements. In some instances, additional problems were discovered during the commissioning of the equipment that required on site modification. The continuous monitoring of the equipment that was supplied to the various clients allowed us to further develop and improve our designs."

Jan 1, 2014

By Sergey Komarov, Manuela Diaz, Sano. Masamichi

"Mixing time, bubble behavior and absorption rate of gas injected into a liquid bath through rotary L-shaped lances have been studied by cold models with an effort to improve refining characteristics of metallurgical processes. Two kinds of the rotary lances were tested, namely the single-hole lance and the multi-hole lance. The effects of gas flow rate, bath depth and rotation speed were examined.It is found that when gas is injected through the rotary lances, the mixing intensity and the gas absorption rate are larger than that for the gas injection through stationary lances. The effect of rotation speed decreases as the bath depth and the gas flow rate increase.The multi-hole lance produces much smaller bubbles, which lead to an increase in the volumetric mass transfer coefficient by 3-4 times as compared with the single-hole lance. However, the effect of rotation speed is smaller for the multi-hole lance. The obtained results are explained in terms of the bubble coalescence and fragmentation, the rate of which depends on the departure bubble size and the power supplied to the liquid bath.IntroductionIn recent years, there has been a growing interest in the development of gas injector for metallurgical processes. The majority of the previous work was focused on modification to the injector design to improve mixing and to increase the of chemical reaction rate. These two goals can not be necessarily achieved by the same way. Bottom nozzles and stationary immersed top lances, which have been widely applied to steelmaking processes, are effective for the bath mixing, but have a limit to decrease in the bubble size. This results from a vigorous coalescence occurring between the bubbles when they rise in the molten bath as a bubble swarm.One of the ways to ensure the small bubble size and the effective bath stirring is the gas purging through rotary injectors. A number of studies have been undertaken to improve the refining characteristics by using rotary injectors. All of them are related to aluminum refining. The SNIF equipment (The Spinning Nozzle Inert Flotation) has significantly improved the quality of aluminum products at National Luxemburg Aluminum [1]. Rotary injectors made in the form of a disc have been applied to the Alcoa 622 [2] and the GBF processes [3]. A study of the gas injection by a rotary impeller has been carried out by C. Leroy and G. Pignacelt [4]. All researchers note the significant improvement in removal of sodium, calcium, hydrogen and non-metallic inclusion."

Jan 1, 1996

By E. Saez, M. Bellet, T. Coupez, O. Jaouen

"The paper presents a 3D finite element solver for non-steady state fluid flow. The thermomechanical simulation package REM3D® has been initially developed to model Stokes' flow for polymer injection. The mechanical module is based on a Eulerian velocitypressure formulation. The spatial discretization uses P 1+IP1 tetrahedral elements. The front tracking module consists of the resolution of a transport equation, thanks to a space-time discontinuous Galerkin formulation. It includes mesh adaptation, which permits a dynamic refinement at the front, thus controling the numerical diffusion. The same approach is used to solve heat transfer. In this paper, we focus on the specific adaptations done to treat Navier Stokes flow. The treatment of inertia is detailed, as well as the implementation of sliding conditions at mould surface, using conservative normals. Industrial applications are presented.IntroductionThe study of the mould filling stage in casting processes requires the ability to simulate complex non steady-state three-dimensional flows. Most commercial software use the volume of fluid (VOF) method, associated with a Eulerian formulation, see for instance the series of conferences ""Modelling of Casting, Welding and Advanced Solidification Processes"" [1-3]. The VOF method [4] consists in solving the conservation equation dF / dt = 0 for a variable F - the volumic fraction of fluid - whose value is 1 in filled regions and 0 elsewhere. Two fluids are actually considered: the molten alloy and a gas in the empty regions. This method suffers generally from numerical diffusion in the resolution of the free surface tracking equation, which is of pure advective type. The precision of the computation is then strongly dependent on the mesh density. Since the mesh is fixed (Eulerian formulation) this implies that in case of complex flow the user must have a priori a fairly good idea of the flow characteristics in order to capture properly the critical features of the flow. In addition, the method can hardly handle the discontinuity of the material viscosity at the interface. To prevent this difficulty, the viscosity value is smoothed around the interfuce, adding once again some inaccuracy. Since the value F = ½ is supposed to represent the free surface, it results in a smeared fluid surface. An alternative to the fixed mesh methods are the methods in which the mesh covers the fluid domain only, as proposed by Navti and Lewis [5-6], or Gaston and Bellet [7]. Based on updated Lagrangian schemes, they must be associated with an ALE formulation (arbitrary LagrangianEulerian) in order to reduce the number of full remeshing operations."

Jan 1, 2004