浸没在金属熔池中固体颗粒熔化过程的数学模型

建立了金属熔池中固体颗粒熔化过程的数学模型。该模型包括颗粒熔点高于、等于和低于熔池中金属熔点的情况。用冰块在水中及铝颗粒在铝熔池中熔化过程的实验数据检验了模型的可靠性，并分析了颗粒尺寸、熔池温度及颗粒相对金属熔体的滑移速度等因素对熔化过程的影响。     

Heat Transfer and Melting Characteristics of Calcium-Cored Wire in Molten Steel

To accurately describe the heat transfer and melting characteristics of a calcium-cored wire in molten steel, the finite difference method is used in theoretical calculations to solve the relationship between the melting temperature, radius, and time. Numerical simulations are performed using the Eulerian–Eulerian method to characterize the temperature distribution at different periods. The results show that the radius of the calcium wire and steel shell both decrease and the melting rate gradually increases. The calcium-cored wire has a fish-scale temperature distribution, with the temperature decreasing from a maximum at the front down to the tail end and increasing outward from the center axis. The temperature of the wire core is 1120 K at 0.272 s, indicating the complete melting of the pure internal calcium. The temperature of the calcium wire–steel shell interface reaches 1793 K at 0.979 s and remains from 1645 to 1757 K at the front of calcium wire. The steel shell melts through, and calcium flows into the molten steel in liquid form. The numerical simulation results generally agree with the theoretical calculations, and the reliability of the model is verified by comparison with published studies.     

Redistribution of Extraneous Solid Particles Suspended in Molten Metal during Passage of an Electric Current

Redistribution of nickel-base heat-resistant alloy suspended in molten tin under the action of a direct electric current is studied by experiment and analyzed. It is established that there is an increase in solid particle concentration over the height and in the radial direction under the action of a current passing along the container axis. This is explained by the simultaneous effect of thermal convection and Lorentz contraction electromagnetic forces directed radially.     

镁热法生产海绵钛还原过程反应熔池的传热模型

利用VOF多相流模型、能量方程、RNGk-ε方程及其边界条件,建立镁热法生产海绵钛还原熔池的传热模型。结果表明,计算得到的温度场分布与实测值吻合较好。     

Stereological Analysis of Nonspherical Particles in Solid Metal

We review in this article the stereological theory of particles and perform stereological analysis of nonspherical TiB₂ particles dispersed in solid aluminum. The two-dimensional (2D) particle size distribution (PSD) obtained from a projected area (PSDP) of TiB₂ powder and the three-dimensional (3D) PSD based on the volume of particles were independently measured by optical microscopy and the electrical sensing zone method, respectively. The results obtained by the two methods were compared by transforming between them, using a fitted fractal dimension for the particles. The probability mass function of the cross-sectional areas (CSAs) of single nonspherical particles was measured by sectioning 3D reconstructions of particles obtained from a series of X-ray micro-CT images. The transformation from 3D PSD to 2D PSD according to the CSA (PSDC) was performed based on the stereological model. The inverse problem for the transformation from the 2D PSDC to 3D PSD is discussed.     

转炉使用低硫铁水冶炼时熔池硫含量变化规律

分析了某厂300t转炉使用低硫铁水冶炼时熔池硫含量的变化规律及影响因素,结果表明：废钢的熔化是熔池硫含量升高的主要原因,钢渣间的脱硫反应主要发生在吹炼的后期,降低废钢比,保持吹炼后期炉渣较高的碱度及较低的氧化铁量有利于得到较低的熔池终点硫含量。     

DC-EAF熔池电磁搅拌与传热的数值计算

本研究应用Spalding数值计算方法,移植顶吹转炉成功的数模与计算软件,加入电磁场洛仑兹力,在理论分析的基础上研制了30t底电极直流电弧炉熔池电磁流场温度场数学模型,开发了计算软件,计算了流场、温度场。     

Heat Transfer Characteristic of Molten Pool for Twin-Roll Strip Casting

Body-fitted coordinate transformation equation was deduced and used to generate the body-fitted grids of molten pool for twin-roll strip casting. The orthogonality of the grids on the boundary was modified by adjusting source item. The energy equation and the boundary conditions were transformed from physical space to computational space. The velocity field model proposed by Hirohiko Takuda was used to calculate the temperature field of molten steel, and the influence of technical factors was also discussed.     

Heat Transfer Modelling of a Blast Furnace Hearth

This paper describes the development of a heat transfer model with the purpose of studying the heat flows in the hearth of an operating blast furnace. Temperature profiles were calculated for a period of time to study the transition from steady blast furnace operation to an unsteady period, and back to a steady period. This total time period had the highest lining temperatures registered since the beginning of the current campaign. It was concluded that no part of the lining had an inner temperature higher than the critical temperature of 1150 °C. Thus, no refractory could have been in direct contact with slag or iron. The corner between the wall and the bottom was identified to be the most sensitive part of the lining. It is suggested that thermocouples are installed in this area, to improve the temperature control.     

喷涂粒子在等离子体射流中的加热历程及熔化状态研究

本文通过对水中收集的等离子喷涂熔融粒子进行粒度分析及形貌观察,研究了喷涂粒子在普通大气等离子喷涂(APS)及超音速大气等离子喷涂(SAPS)射流中的加热历程及熔化状态。实验观察到氧化钇部分稳定的纳米颗粒团聚造粒的氧化锆(Y-PSZ)球形粉末颗粒在APS及SAPS射流中传热传质过程中的熔融与"细化"现象有明显不同:在SAPS射流中,尺寸较大(粒径在几十微米)的颗粒大部分形成了十分细小的(小于5μm)颗粒;相对而言,APS中的熔融粒子仍以十几微米以上较大粒径的半熔融粒子为主。进一步研究表明,大尺寸粒子在等离子射流中先从表层熔化,逐渐向颗粒内部扩展,形成柱晶熔区,属典型的梯度熔化模式,最终芯部存留大量细小未熔一次粒子,即所谓半熔融状态;相应的SAPS中大量粒径小于5μm的小颗粒在超音速等离子体射流中整体迅速熔化(即所谓等温熔化模式)。对熔融或半熔融粒子撞击基体后的扁平化过程进行分析表明:在APS射流中扁平粒子的直径一般在100μm以上,且周围飞溅较多,导致典型的层状多孔的粗大组织结构,层间出现较多平行横向裂纹;而SAPS大量细小熔滴撞击基体后,冷却更快,多呈无明显飞溅的直径约10～30μm圆盘状,形成大量细密柱晶交错堆垛而成的、无明显分层的特殊结构。对收集粒子进行X-射线衍射相分析表明,APS及SAPS两种工艺下的熔融粒子均未发生明显相变,相组成主要为室温下非转变四方氧化锆(t’-ZrO2),说明喷涂粒子在高温等离子射流的加热历程中,其晶体结构和化学成分未发生明显变化。     

Performance of Flow and Heat Transfer in a Hot-Dip Round Coreless Galvanizing Bath

Metallurgical and Materials Transactions B - Flow field in a coreless hot-dip galvanizing pot was investigated through a water modeling experiment. The corresponding velocity vector was measured...     

Metastable Phases of Dross Particles Formed in a Molten Zinc Bath and Prediction of Soluble Aluminum During Galvannealing Processes

The morphology, chemistry, and crystallographic characteristics of metastable dross particles were identified. These particles are formed during the initial stage of precipitation. The particles had aluminum concentrations of 15 to 80 mass pct, with values that decreased gradually as particle size increased. These metastable dross particles were a mixture of the crystalline phase of FeZn₁₀, which is called the “delta phase,” and the high-aluminum amorphous phase, which covered the surface of the crystalline phase. The new “meta Q” concept was proposed to predict the amount of soluble aluminum in the zinc bath by considering nucleation kinetics and particle growth. The results calculated using the “meta Q” concept were compared with the values measured by the aluminum sensor, which were taken during the same period at the commercial galvanizing line. The mean of the absolute values of the differences between the calculated and measured values was 9.7 ppm.     

Wetting Transition in a Molten Metal and Solid Substrate System in High Magnetic Fields

Metallurgical and Materials Transactions A - Wetting transitions between molten metals and different solid substrates were investigated using the sessile drop method to evaluate the possibilities...     

Modeling of an Impinging Oxygen Jet on Molten Bath Surface in 150 t EAF

 A transient three-dimensional mathematical model has been developed to analyze the three-phase flow in a 150 t EAF (electric arc furnace) using oxygen. VOF (multiphase volume of fluid) method is used to simulate the behaviors of molten steel and slag. Numerical simulation was conducted to clarify the transient phenomena of oxygen impingement on molten bath. When oxygen jet impinges on the surface of molten bath, the slag layer is broken and the penetrated cavity in molten steel is created. Simultaneously, the wave is formed at the surface of uncovered steel on which the slag layer is pushed away by jet. The result of numerical simulations shows that the area and velocity of uncovered steel created by impingement, jet penetration depth change from 0.10 m2, 0.0125 m/s, 3.58 cm to 0.72 m2, 0.1445 m/s, 11.21 cm, when the flow rate of an oxygen lance varies from 500 to 2000 m3/h. The results have been validated against water model experiments. More specially, the relation between the penetration depth and oxygen flow rate predicted by numerical simulation has been found to agree well with that concluded by water model.     

铁水熔池中钛和硅的扩散能力

采用毛细管—熔池法测定及分析了铁水中钛、硅的扩散系数和铁水中钒对钛扩散系数的影响。结果表明，钛和硅的扩散活化能为ＥＤＴｉ＝４４２３０４Ｊ／ｍｏｌ，ＥＤＳｉ＝４９７６６Ｊ／ｍｏｌ；扩散系数与温度的关系为ＤＴｉ＝７．７６×１０８ｅｘｐ（－５３２２５．５／Ｔ）ｃｍ２／ｓ，ＤＳｉ＝１．８４×１０－３ｅｘｐ（－５９８８．７／Ｔ）ｃｍ２／ｓ。铁水中的钒会降低钛的扩散能力，这有利于抑制钒钛磁铁矿冶炼时钛的还原     

Computational Modelling of Heat/Mass Transfer Near the Liquid-Solid Interface During Rapid Solidification of Binary Metal Alloys Under Laser Treatment

Abstract

This paper presents the results of an investigation into the problem of planar solid-liquid interface stability during rapid solidification of binary metal alloys under laser treatment. A new quantitative model is proposed. This model describes the self-organized development of stable spatially-periodic vortices in the melt near the solid-liquid interface due to concentration- (or thermal) capillary effects) together with effects due to the influence of normal concentration or temperature gradients directed from the interface towards the melt. These vortices give rise to a cellular structure at the solid-liquid interface of rapidly frozen melts.

A computer code was developed to solve the set of second-order linear differential equations which describe heat and mass transfer at the liquid-solid interface. This model allows calculation of the liquid phase velocity field, the second component concentration field in the melt, as well as the temperature field in the liquid and solid phases near the solid-liquid interface at a given solidification rate. © 1998 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved.

Résumé

Ce document presenté les résultats de l'etude du problème de stabilité de l'interface solide-liquide plane lors de la solidification rapide d'alliages metalliques binaires par traitement au laser. On propose un nouveau modèle quantitatif. Ce modele decrit le développement auto-organisé de tourbillons stables,périodiques dans l'espace, dans le bain fondu près de l'interface solide-liquide. Ces tourbillons sont dus aux effets1 capillaires de concentration (ou thermiques) ainsi qu'à l'influence de la concentration normale ou des gradients de températures diriges de l'interface vers le bain fondu. Ces tourbillons donnent naissance à une structure cellulaire a l'interface solide-liquide des bains fondus rapidément solidifiés.

On a développé un code d'ordinateur pour resoudre l'ensemble d'equations differentielles lineaires de second ordre qui decrivent le transfert de chaleur et de masse à l'interface liquide-solide. Ce modèle permet le calcul du champ de vitesse de la phase liquide, du champ de concentration de la seconde composante dans le bain fondu, ainsi que du champ de temperature dans la phase liquide et la phase solide près de l'interface solide-liquide, à un taux donné de solidification. © 1998 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved.     

金属凝固前沿热传递系数变化规律的探讨

分析了金属凝固过程中界面热传递的4个阶段及在各阶段热传递的机理,推导出界面热传递系数在各个阶段的表达式。通过分析文献实验数据,得出了在整个凝固过程中热传递系数与空气隙成反比的半径经验耦合表达式。     

超大型侧吹熔池熔炼余热锅炉烟气流动及烟尘黏附研究

富氧侧吹熔池熔炼广泛应用于铜、铅、锌等有色金属的提取,其后端的余热锅炉承载着余热回收利用、沉降烟尘的重要作用。但在实际生产过程中,炉内烟气流场混乱、烟尘易黏附积灰、炉壁与部件磨损严重等,导致了余热回收效率降低、低负荷运行甚至被迫停机。针对上述问题,采用多相网格质点方法,对年处理150万吨精矿超大型富氧侧吹熔池熔炼余热锅炉内烟气流动特性、烟尘沉降与黏附开展数值模拟研究。结果表明,炉内的烟气涡旋会导致烟尘回流至入口烟道;挡板前移会导致挡板受击与堵塞情况加剧;增大挡板间距能有效减小挡板的堵塞;增大辐射室空间能大幅度减小挡板受到的冲击。