结晶器内钢水凝固传热数字描述的发展

计算机技术和数学理论的发展,结晶器内钢水凝固传热数学模型也从最初的解析法向数值计算法发展,综述了结晶器内钢水凝固各区及界面的传热数学模型的发展。     

基于反算热流的结晶器内流动--传热--凝固耦合模拟

基于Navier-Stokes动量方程和湍流低雷诺数k-ε方程,综合考虑能量守恒和钢液凝固与糊状区对流动过程的影响,建立了描述结晶器内钢液流动、传热及凝固过程的三维耦合数学模型.以实测温度和结晶器反问题模型计算出的热流为边界条件,模拟计算了结晶器内钢水的流动、传热和凝固行为.钢液流动决定结晶器内的温度和热流分布,铸坯凝固受钢液流动和结晶器热流双重因素的影响.建立的模型以及由此得到的铸坯凝固非均匀特征可为进一步考察浇铸过程中纵裂和其他表面缺陷提供借鉴和参考.      

方坯结晶器

1 前言 结晶器是连铸机中最重要的部件之一。从传热学角度讲,它是个热交换器,由流经它的冷却水带出钢水凝固潜热,使钢水凝固成具有一定厚度坯壳的铸坯。结晶器对铸坯表面质量优劣,连铸生产正常与否有着直接和重要的关系。 对结晶器的技术要求,主要包括以下几个方面: (1)传热性能好,冷却强度可调钢水在结晶器内凝固成坯壳,其传热路     

电磁搅拌结晶器钢液流场和温度场模拟仿真

建立了360 mm×450 mm方坯连铸结晶器电磁搅拌作用下结晶器内钢液流场和温度场的三维数学模型,并应用模型分析了结晶器内钢液流场、温度场的分布特征。结果表明,采用电磁搅拌后,从浸入式水口流出的钢水在电磁搅拌的有效区由垂直向下转变为水平旋转,形成旋转流动的主流区,且在主流区上方的钢水形成由中心向下和由凝固面一侧向上的环流,在主流区下方的钢水形成由凝固面一侧向下和由中心向上的环流。同时,钢水在电磁搅拌作用下流动方向由垂直向下变为水平旋转,使从浸入式水口流出的过热钢水的侵入深度变浅,轴向温度迅速降低,而径向温度升高,凝固前沿的温度梯度增大,有利于传热和促进凝固坯壳的均匀生长。     

薄板坯凝固过程数学模型及冷却参数的研究

由于高质量薄板坯连铸工艺对冷却条件要求非常严格,因此,以薄板坯连铸工艺为研究对象,建立了凝固传热过程的数学模型.定量地分析了各种工艺参数对结晶器内和二冷区钢水凝固过程的影响,以指导生产实践,也可作为进一步开发在线控制模型的基础.     

结晶器钢水注入和凝固新模拟方法的开发

过去几十年,对连铸结晶器的钢水注入和凝固过程的数学模型进行过许多研究,也开发出了许多模型。传统的结晶器钢水注入模型大多数都是基于显方案,而大多数凝固模型都基于隐方案的,钢水注入和凝固都是在结晶器内完成的。为了解决这个问题,开发了一种新的组合方法。     

结晶器钢水注入和凝固新模拟方法的开发

过去几十年，对连铸结晶器的钢水注入和凝固过程的数学模型进行过许多研究．也开发出了许多模型。传统的结晶器钢水注入模型大多数都是基于显方案．而大多数凝固模型都基于隐方案的．钢水注入和凝固都是在结晶器内完成的。为了解决这个问题，开发了—种新的组合方法。     

结晶器钢水注入和凝固新模拟方法的开发

过去几十年，对连铸结晶器的钢水注入和凝固过程的数学模型进行过许多研究，也开发出了许多模型。传统的结晶器钢水注入模型大多数都是基于显方案，而大多数凝固模型都是基于隐方案的，钢水注入和凝固都是在结晶器内完成的。为了解决这个问题，开发了一种新的组合方法。     

SPHC连铸结晶器内钢水凝固传热的研究与应用

为了适应唐山不锈钢厂2号连铸机拉速的提高,建立板坯连铸结晶器内钢水凝固传热模型,应用大型有限元软件ANSYS对钢水凝固传热过程进行模拟求解,描述了高拉速条件下凝固坯壳的温度分布、坯壳生长历程,分析各工艺因素对钢传热行为、凝固行为的影响,进而提出了合理的工艺参数并应用于连铸机,现场证明漏钢事故明显减少.     

H型钢连铸结晶器内钢水凝固传热的数学模拟

 为了解决H型钢连铸坯表面裂纹问题,结合凝固理论建立了H型钢连铸结晶器内钢水凝固传热模型,并应用大型有限元软件ANSYS对钢水凝固传热过程进行模拟求解,描述和分析了凝固坯壳的温度分布、坯壳生长历程及各工艺因素对钢传热行为、凝固行为的影响,为制定合理的工艺参数、提高铸坯质量、减少漏钢发生提供了理论依据。     

水平连铸过程热平衡实测与分析

本文通过水平连铸全过程钢水和铸坯温度变化及相关参数的实测，研究了水平连铸过程中钢的热平衡规律，并建立了铸坯凝固传热，中间包钢水温度，钢包钢水温度，包衬温度与吸热等数学模型。实测和分析表明，在该铸机上，钢水在钢包和中间包中分别损失了其热量的７％和１．２％，在结晶器和空冷段所传出的热量分别占１８％和２０％，切割时仍有５４％的热量保留在铸坯中。     

连铸结晶器内钢液凝固行为的计算机仿真

用计算机仿真的方法研究结晶器内钢液流动与传热，从而了解钢液的凝固行为。同时利用有效热容的概念来处理相变潜热源项，在程序编制过程中利用动态更新来实现凝固对物理量的影响。模型求解得到的凝固壳厚度与漏钢测试结果吻合，说明所采用的方法正确、实用。研究了拉速、水口插入深度、水口角度等因素对凝固壳厚度分析的影响。     

日本高速连铸技术的开发

通过对连铸结晶器内的钢液流动、润滑技术、热流与冷却、振动与凝固以及实机操作等的研究,证实中碳钢采用2m/min,低碳钢用5m/min 的铸速,可进行稳定的高速连铸。     

Surface Solidification Behaviour of Micro‐Alloyed Steels under Continuous Casting Conditions

Micro‐alloyed steels are important in steel industry with regard to their unique mechanical properties. Their characterisitcs are mainly caused by the refinement of ferrite grain size by controlled precipitation of nitrides during thermomechanical treatment in hot rolling. Uncontrolled precipitations of titanium nitrides in the surface region during casting and solidification can negatively influence the surface quality of continuously cast steel, particularly when casting, thermal soaking and hot rolling are carried out in a combined process chain. Focus of this work are experimental simulations and mathematical investigations of early solidification in a CC mould, primary precipitation of nitrides, and effects of different influences such as mould contact through casting flux or direct mould contact. A laboratory rig to lead solidification on liquid casting flux was developed. The carbon content of the steel melts was varied.     

Numerical simulation of fluid flow and solidification in continuous slab casting mould based on inverse heat transfer calculation

Abstract

A mathematical model based on an inverse heat transfer calculation was built to determine the heat flux between the mould and slab based on the measured mould temperatures. With K–? turbulence model, a mathematical model of three-dimensional heat transfer and solidification of molten steel in continuous slab casting mould is developed. Solidification has been taken into consideration, and flow in the mushy zone is modelled according to Darcy’s law as is the case of flow in the porous media. The heat flux prescribed on the boundaries is obtained in the inverse heat conduction calculation; thus, the effect of heat transfer in the mould has been taken into consideration. Results show that the calculated values of mould temperature coincide with the measured ones. Results also reveal that the temperature distribution and shell thickness are affected by the fluid flow and heat transfer of slab which is governed by the heat flux on the mould/slab interface.     

冒口对钢锭凝固过程固相转变影响的数值模拟

通过自建模型模拟研究了冒口材质和高度对大钢锭凝固过程中固相转变的影响。结果表明:钢锭凝固过程中,锭模及底座附近的钢液发生相转变的速率较快且固液共存区宽度较窄,而冒口附近的钢液发生固相转变的速率较慢且糊状区较宽。相比于传统的黏土砖,轻质砖和绝热板均有助于改善冒口的保温性能,且均可减缓冒口外表面温度上升的速率。冒口高于钢液上表面部分高度的变化对于钢锭凝固过程中冒口附近钢液相转变速率的影响较小。     

Challenge to control mould heat transfer during thin slab casting

Abstract

At the thin slab caster of Tata Steel, IJmuiden, mild cooling mould powders were introduced with the aim to control the mould heat transfer during casting. These mild cooling mould powders are characterised by specific values of basicity, solidification point and chemical composition. Application of these mould powders resulted in a redistribution of mould heat transfer during casting, i.e. a reduced and more stable mould heat transfer in the critical upper part of the mould and an increased mould heat transfer in the lower part of the mould. The average mould heat transfer and hence the shell thickness at mould exit are comparable to the standard powder. The application of mild cooling mould powders also resulted in improved solidification behaviour of the steel shell. A thinner chill zone with smaller thickness variations was observed. Furthermore, it was found that the mould taper required optimisation to match the changes in shrinkage behaviour to ensure uniform solidification. The use of mild cooling powders was observed to give an increase in mould friction. Mould thermal monitoring indicated that the solid slag films fractured (sheeting) in the upper part of the mould. However, no operational problems were reported, which indicate that the first 200 mm under the steel meniscus is essential for initial solidification and for the formation of a homogeneous steel shell. All these findings can be understood by considering the crystallisation properties of the mould slag, which include the cooling rate. Mild cooling has been shown to provide uniform heat transfer and adequate lubrication for high speed thin slab casting.     

高速方坯连铸结晶器冶金理论问题探讨

提出并论述了高速方坯连铸结晶器冶金中结晶器热流、钢的凝固收缩、结晶器变形、锥度设计和圆角半径等问题,重点讨论了拉速、碳含量及润滑剂对热流的影响,不同碳含量的钢凝固收缩和相变特征以及结晶器热变形规律,提出了不同钢种的凝固收缩和相变收缩的计算方法和结晶器锥度、圆角半径的设计思路.     

小方坯结晶器传热状况初探

通过对安钢第二炼钢厂小方坯结晶器热流密度、结晶器水速、凝固系数的计算,分析探讨了结晶器的冷却能力对生产过程的影响。