Modeling heat-and-mass exchange processes in the Vanyukov furnace in specific operational conditions

A mathematical model of the Vanyukov furnace is developed. This model ensures the prediction of the behavior of the object during emergency operation, namely, if oxygen is turned off, and the construction of an effective system of additional heating, which dampens the consequences of the emergency mode and reduces the costs for furnace reactivation. The efficiency of the dynamic zone-node computation technique (the DZN or two-grid method) is shown, and the mathematical model is adapted to the existing production conditions, which are characterized by weak definiteness. A simulation made it possible to acquire a detailed pattern of complex gas-dynamic and temperature processes in all points of the furnace space. A system of the criteria of the quality of the emergency heating process is developed. Using our model, a variant of the structure and the parameters of the heating system making it possible to hold the surface of the quiet bath in the molten state for more than four days while being sufficiently effective is selected.     

Using acoustic field energy to decrease dust discharge from the working space of the Vanyukov furnace

To organize in-furnace dust settling in the Vanyukov furnace at OAO SUMZ (Revda, Russia), acoustic emitter technology is used. The emitter design includes a nozzle tube, an air nozzle, a resonator, and a focusing surface. Starting from the surface area of the furnace melt bath and recommended specific acoustic power for in-furnace dust settling, the summary acoustic field sound power is calculated and the optimal amount and arrangement places of acoustic emitters are determined. To form the acoustic field in the Vanyukov furnace for melting copper sulfide zinc-containing feedstock and deplete liquid converter slags, four acoustic emitters are mounted in the end wall through an inspection window, two on the apothecary side and two on the loading side of charge materials. In general, six pilot modes of testing the in-furnace dust settling system with various operational settings of acoustic emitters and one base mode for comparing performance characteristics are implemented. The duration of pilot periods varies from 5 to 18 days, and the total aggregate service time is 68 days. The presence of the acoustic field in the working furnace space at any emitter operation settings promote a decrease in the concentration of dust particles after the chain of gas purifiers (in the commodity point). It is revealed by the experimental data that the minimal summary acoustic field sound power, which decreases the dust concentration due to the coagulation of dust particles inside the furnace space, is 800 W.     

Cooling and solidification of slag melt in spherical packing

Physical modeling of the high-temperature cooling and solidification of slag melt that is penetrating into spherical packing permits assessment of the thermal and physical parameters of the slag as it cools in the spaces between the spheres. The chemical and phase composition of the broken slag is investigated, and its physicomechanical characteristics are determined. The data obtained permit the development of systems to convert slag melt to gravel and inert filler for concrete.     

Rapid solidification characteristics in melt spinning a Ni-base superalloy

The solidification kinetics involved in the process of melt spinning a Ni-base superalloy have been characterized. Through a correlation of ribbon thickness to melt puddle residence time, it was found that the solidification front velocity,V, is typically about 100 mm per second at the ribbon surface not in contact with the spinning wheel. The rate of solidification varies within the ribbon, increasing with decreasing distance,S, from the wheel-contact surface asV = 3.65S ^-1. Ribbon microstructure and texture characteristics are discussed in light of this kinetics result. The thickness-vs-time correlation was further analyzed to yield information about thermal history during ribbon formation. These thermal results are generally consistent with those deduced from dendrite arm spacing measurements. Formerly with General Electric Research and Development Center.     

Developing a model of fuzzy logic and a controller to control smelting of copper sulfide concentrate in the Vanyukov furnace

The development of a fuzzy controlling model for smelting copper sulfide concentrate in the Vanyukov furnace of the PV-2 complex of the Zapolyarnyi (Arctic) Branch of OAO GMK Norilskii Nikel’ Copper Plant is presented. A fuzzy model in the form of polynomials and the circuit of a fuzzy controller developed on its basis are given.     

Nonequilibrium solidification of undercooled melt of Ag-Cu alloy entrained in the primary phase

The solidification structure of undercooled melt of Ag-Cu alloy, entrained in its primary Cu-rich phase, has been investigated. The undercooling procedure consisted of equilibration of a Cu-13 pct Ag alloy in the two-phase liquid-solid region, followed by repeated thermal cycling of the liquid. Slow cooling of the sample in the present work established the ability to undercool the melt up to 70 K below the eutectic temperature of this alloy. The microstructure of the undercooled alloy indicated a complete absence of eutectic reaction on subsequent quenching of the melt directly from the equilibration temperature. The compositional analysis of the constituent phases by electron probe microanalysis (EPMA) technique provided evidence for the massive diffusionless solidification of the undercooled liquid. The X-ray diffraction study and electron microscopic examination indicated evidence for the spinodal transformation of the metastable solid solution phase. The composition of the phases formed on decomposition matched well with the calculated coherent spinodal boundaries in this system. The evolution of the metastable microstructure in the mushy-state quenching process of this alloy is discussed.     

Effect of the overheating of the gallium melt on its supercooling during solidification

The effect of overheating ΔT _L ⁺ of the gallium melt on its supercooling ΔT _L ^? during solidification is studied by cyclic thermographic analysis. The obtained data on ΔT _L ^? are used to calculate the thermodynamic and kinetic characteristics of gallium solidification.     

Metal loss and charge heating in the melt in an electric arc furnace

The heat exchange between a metallic melt and a slag with a charge is simulated with allowance for possible formation of a skull on the charge surface. It is shown that the charge melting rate in the melt is determined by the coefficient of heat transfer between the metal and the charge and the ratio of the mass of a charge fragment to its surface area interacting with the melt. A skull is found to form on the charge surface at a low coefficient of heat transfer between the metal and the charge. The main heat parameters, the control of which by an automatic control system ensures an increase in the charge melting rate in the melt and a decrease in the metal loss, are formulated.     

Boron removal by titanium addition in solidification refining of silicon with Si-Al melt

In order to effectively remove B from Si for its use in solar cells, a process involving B removal by solidification refining of Si using a Si-Al melt with Ti addition was investigated. For clarifying the effect of Ti addition on B removal from the Si-Al melt, TiB₂ solubilities in Si-64.6 at. pct Al melt at 1173 K and Si-60.0 at. pct Al melt at 1273 K were determined by measuring the equilibrium concentrations of B and Ti in the presence of TiB₂ precipitates. The small solubilities of TiB₂ in the Si-Al melt indicate the effective removal of B from the Si-Al melt by Ti addition. Further, solidification experiments of Si-Al alloys containing B by Ti addition were performed, and the effect of Ti addition on the solidification refining of Si with the Si-Al melt was successfully confirmed.     

Properties of titanium alloy VT6 fibers obtained by rapid solidification of the melt

We have studied the chemical, physicochemical, and technological properties of titanium alloy VT6 fibers in the initial state and after vacuum annealing for one hour at 500–1300°C. We have carried out fractographic, microstructural, and qualitative x-ray spectral microanalysis of the fibers. We have established that in the initial state, the fibers possess high values of the physicomechanical characteristics; the decrease in the properties of the fibers with a rise in temperature was determined by observing changes in the microscopic and macroscopic structure and the chemical composition. Vacuum annealing of VT6 fibers allows us to improve their compressibility with different combinations of hardness, strength, and conductivity characteristics.Institute of Problems in Materials Science, National Academy of Sciences of Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3–4, pp. 85–90, March–April, 1994.     

高炉风口回旋区系统的模拟

因为鼓风是预热、还原和熔化铁矿石所需要的热气体的来源,所以鼓风在各风口均匀分配是高炉顺行的重要前提.而回旋区产生的热气流在高炉边缘分布不必均匀.为了研究和分析风口参数和边界条件变化的影响,开发了一种用于风口回旋区系统的模型,对风量、风压、风口直径和喷吹还原剂的燃烧率等变量进行了研究.同时还开发了一种用于实时跟踪风口情况变化的模型在线版本.     

高炉铁口孔道侵蚀过程的模拟

从流体动力学的角度出发,建立高炉出铁口处流动的数学模型.基于对孔口出流出口处流线公式的推导并作适当修正,计算出铁时铁口孔道的侵蚀形状,并描述了侵蚀过程.通过水模型实验和模拟计算的方法分别模拟出侵蚀过程.实验与模型假设较为符合,可以为铁口区的维护以及推荐适宜的打泥量提供参考.     

Modeling of marangoni-induced droplet motion and melt convection during solidification of hypermonotectic alloys

A two-phase volume averaging approach to model Marangoni-induced droplet motion of the minority liquid phase and the convection in the parent melt during solidification of the hypermonotectic alloys is presented. The minority liquid phase decomposed from the parent melt as droplets in the miscibility gap was treated as the second-phase L ₂. The parent melt including the solidified monotectic matrix was treated as the first phase L ₁. Both phases were considered as different and spatially interpenetrating continua. The conservation equations of mass, momentum, solute, and enthalpy for both phases, and an additional transport equation for the droplet density, were solved. Nucleation of the L ₂ droplets, diffusion-controlled growth, interphase interactions such as Marangoni force at the L ₁-L ₂ interface, Stokes force, solute partitioning, and heat release of decomposition were taken into account by corresponding source and exchange terms in the conservation equations. The monotectic reaction was modeled by adding the latent heat on the L ₁ phase during monotectic reaction, and applying an enlarged viscosity to the solidified monotectic matrix. A two-dimensional (2-D) square casting with hypermonotectic composition (Al-10 wt pct Bi) was simulated. This paper focused on Marangoni motion, hence gravity was not included. Results with nucleation, droplet evolution, Marangoni-induced droplet motion, solute transport, and macrosegregation formation were obtained and discussed.     

Influence of melt temperature on Rapid solidification of Al-Y and Al-Si alloy system

Solidification behavior of Al-Y and Al-Si were investigated for different melt temperatures. Levitation casting technique was used to achieve a cooling rate of around ～2000K/s during the experiment. Light optical microscopy (LOM) and Scanning electron microscopy (SEM) were used to analyze the samples. An energy dispersive system (EDS) analysis of SEM was performed on the samples to identify the phases. Plate like structure of Al₈Y₃ primary phase was observed at low melt temperature with small percentage of peritectic transformation of Al₈Y₃ and liquid melt into Al₉Y₂. A pre-dentritic star like crystal of Al₃Y was observed in a fine eutectic matrix at very high melt temperature. Amount and number of primary Si crystals formed in a unit area during the solidification increases as the melt temperature increases. It is believed the melt temperature affects the solidification pattern by changing chemical short range order.     

To the theory of directional solidification with a mushy zone in the presence of convection and kinetics in the melt

The directional solidification of binary systems in a frontal mode and in the presence of a phase transition region (mushy zone) is theoretically studied with allowance for convective-kinetic heat-and-mass transfer mechanisms. Nonlinear mathematical models are developed for this process, and their analytical solutions corresponding to various values of the system parameters are obtained.     

Refining a complex ZhS32-VI nickel alloy from silicon and phosphorus by unidirectional solidification of the melt at low solidification front velocities

The possibility of decreasing the silicon and phosphorus contents in a high-temperature ZhS32-VI nickel alloy by directional movement of solidification front at a velocity V = 6 mm/h has been studied. As a result, the contents of the impurities have decreased as compared to those in the starting alloy; the decrease in the silicon and phosphorus contents is from 2 to 4 and from 14 to 20 times, respectively. Thus, nonmetallic inclusions, in particular, those containing silicon and phosphorus, are moved to the top of the ingot.     

Investigation on dendritic solidification and microsegregation in presence of melt convection using phase field simulation

Abstract

A phase field model has been used to simulate dendritic solidification of a binary alloy in the presence of forced melt convection. The influence of melt flow on morphology and solute distribution was investigated for various conditions. The results showed that incorporation of fluid flow causes asymmetric dendritic growth which is amplified by increasing fluid velocity. Moreover, it has been found that the effects of melt flow on the growth of different arms depend on the preferred growth orientation of the dendrite with respect to flow direction. Solid microsegregation study of the growing dendrite arm perpendicular to the flow direction indicated that the position of the arm axis varied almost linearly with flow velocity. Introducing an adjusting term called an antitrapping current in the concentration equation prevents solute from being highly trapped in the solid phase and causes the phase field simulations to be more realistic, especially for high undercoolings.

On a utilisé un modèle de champ de phase pour simuler la solidification dendritique d’un alliage binaire en présence de convection forcée du bain. On a examiné l’influence de l’écoulement du bain sur la morphologie et la distribution de soluté sous des conditions variées. Les résultats ont montré que l’incorporation de l’écoulement du fluide produisait une croissance dendritique asymétrique qui est amplifiée par l’augmentation de la vitesse du fluide. De plus, on a trouvé que l’effet de l’écoulement du bain sur la croissance de différentes branches dépendait de l’orientation préférée de la croissance de la dendrite par rapport à la direction de l’écoulement. L’étude de la microségrégation solide de la branche de dendrite en croissance perpendiculaire à la direction de l’écoulement indiquait que la position de l’axe de la branche variait presque linéairement avec la vitesse de l’écoulement. L’introduction d’un terme d’ajustement, appelé courant de contre-piégeage, dans l’équation de concentration empêche le soluté d’être trop piégé dans la phase solide et rend les simulations de champ de phase plus réalistes, particulièrement dans les cas de surfusions élevées.