智能算法在双辊铸轧过程铸轧力计算中的应用

在双辊铸轧过程中,铸轧力的控制是铸轧过程稳定进行和提高薄带质量的关键.为了控制铸轧力,必须建立铸轧力计算数学模型,本文采用了一种基于贝叶斯方法的前向神经网络训练算法以提高网络的泛化能力,在网络的目标函数中引入了表示网络结构复杂性的惩罚项,融入"奥克姆剪刀"理论,避免了网络训练的过拟合.将上述网络应用于铸轧过程的铸轧力计算,具有很高的计算精度,同时在收敛速度、稳定性和泛化能力方面都优于传统的BP神经网络.     

The future of the twin-roll strip casting and rolling process

Twin-roll strip casting and rolling is a typical near-net-shape steel manufacturing process. The twin-roll strip casting and rolling of low-carbon steel strips has made a number of breakthroughs and achieved significant results during the past 20 years. Baosteel has been paying close attention to the development of this technology and set up a research and development project focused on its industrialization in 2001. The Ningbosteel-Baosteel strip casting industrialization demo project( NBS),which was launched in 2016,marks the strip-casting technology( registered as Baostrip) developed by Baosteel as having reached an advanced international level after 15 years of effort. This paper summarizes the results obtained in the industrialized demonstration plant and considers the future development of strip casting and rolling.     

Computer modelling for thin strip twin-roll casting

In twin-roll casting, the influence of the heat-transfer rate at the metal–mold boundary on the thickness and the proportion of solidifying metal at the exit from the water-cooled roller mold is analyzed. The corresponding analytical curves are plotted for the production of moderate-carbon and stainless steel strip (thickness 1–6 mm). The proposed method may be used in the development of twin-roll technology and equipment.     

双辊薄带连铸用结晶辊套温度场及其热变形

利用非线性热力耦合有限元方法,对浇铸过程中结晶辊辊套的温度场分布进行了研究,并同时计算出了结晶辊的热变形.给出了浇铸稳定阶段的结晶辊温度场分布和热变形规律;分析了浇铸速度对结晶辊温度场和热变形的影响.通过分析得出,在浇铸稳定阶段结晶辊温度只在表层区域发生周期性变化,内部保持基本稳定,浇铸速度越低,周期性变化幅度越大.     

Two-dimensional model for twin-roll continuous casting

A numerical algorithm for the two-dimensional solidification problem in the twin-roll continuous casting system is presented in this paper. Attention is focused on the elucidation of heat transfer and flow characteristics in both the liquid and the solid phases. The present mathematical model can be applied to general full Navier-Stokes and energy equations, thereby covering the wide range of twin-roll casting conditions. The boundary fixing method (BFM) is adopted to handle the moving boundary, and the resultant transformed governing equations for the solid and liquid regions are solved separately by using a usual explicit-type finite difference method. In this paper, a general numerical methodology is presented, and the quantitative relationships between the important control parameters in continuous casting of twin-roll type (such as the roll speed, the roll gap, the initial temperature of molten materials, the material properties, the solidification profile, and the endpoint of solidification) are clarified in detail. The present numerical results have been compared with experimental results obtained separately to check the validity of the proposed method.     

双辊铸轧薄带钢工艺参数检测系统的建立与结果分析

设计和建立了双辊铸轧机的工艺参数在线检测系统，介绍了数据处理方法并对测量数据进行了分析处理，其结果对双辊铸轧薄带钢的过程控制和薄带质量的提高提供了可靠的依据。     

Mathematical modeling of fluid flow and level profile during twin-roll strip casting process

In twin-roll strip casting process,transport phenomena of fluid in the molten pool directly affect the process stability and the quality of products.In order to elucidate the fundamental transport phenomena in twin-roll casting,a commercial software called ProCAST was employed to simulate the transient fluid flow and level profile behaviors during the early stage of the process in this study.The coupled set of governing differential equations for mass,momentum and energy balance were solved with the finite element method and the transient free surface problem was treated with a volume of fluids(VOF) approach.The effect of different delivery systems configuration on flow pattern,level profile in the pool was studied and analyzed in this paper. The new wedge metal delivery systems have been optimized for the twin-roll strip caster.It was shown that new type metal delivery systems had a preferable effect on the uniform distribution of fluid and level fluctuation in the pool.The simulation results also provide a valuable basis for the optimization of delivery system and process parameters during the initial pouring stage.     

待定系数法确定双辊薄带铸轧中的边界热流

熔池与铸轧辊接触的边界热流是进行双辊薄带铸轧数值模拟研究的重点,通过铸轧过程中金属凝固机制和传热过程的研究,提出结晶辊和熔池接触的边界热流分布函数形式,利用凝固初始位置、薄带坯出坯厚度,再结合能量守恒原理进行求解,确定函数中的待定参数,避开传统方法需要求解坯壳和铸轧辊间气隙热阻的难题;通过施加所提出的边界热流函数对某试验铸轧辊温度场进行求解,结果与实测结果相吻合,这表明文中提出的边界热流分布函数形式与实际相符合。     

Mechanical properties of type 304 stainless steel sheet produced by twin-roll strip casting process

Tensile properties and formability of type 304 stainless steel sheets which were cast by a twin-roll type strip caster and thereafter cold-rolled are examined and compared with those of conventionally processed sheets. The results exhibit that the strip casting processed sheets have mechanical properties almost equal to the conventional ones. Furthermore, it is found that the degree of plastic anisotropy caused by crystallographic anisotropy in the present sheets is weaker than that in the conventional ones.     

Wear analysis of a side dam in twin-roll strip casting

Reducing wear on a side dam can prolong the casting operation life of a twin-roll strip casting process,thus reducing production cost and improving casting stability. To lengthen the service life of the side dam,it is necessary to understand the wear performance of the side dam material. To investigate the wear behavior mechanism of the side dam,in this study,the UMT-2 friction and wear tester was used to determine the relationship between the wear rate of the side-dam material and various parameters. Based on the roughness of the contact area between the side dam and the end of the casting rolls as well as on the amount of deformation of the side dam,which was derived using a thermal-deformation simulation model,the reasons for the uneven wear of the side dam were obtained.     

铝带坯双辊铸轧过程瞬态传热数学模型

采用拉格朗日随体坐标建立了铝双辊铸轧过程瞬态传热数学模型。模型考虑了金属凝固动力学条件和采用试验测定的辊／铝带坯界面接触换热系数边界条件，用有限差分方法对控制方程进行了数值求解，并由现场测试数据验证了传热数学模型的正确性。     

双辊薄带钢铸轧机在线监测及过程模型的建立

分析双辊铸轧薄带钢过程中在线监测系统及后续参数分析的重要性和实用性,阐述了系统的构成、硬件和软件配置、功能。针对双辊铸轧实验轧机建立了相应的在线监测和数据分析系统,为研究双辊铸轧技术提供准确的数据和优化参数,同时利用神经网络及机理模型相结合的建模方式,采用高斯基函数修正模型自适应增益系数方法,提高过程模型的计算精度。     

Analysis of surface microcracks in low-carbon steel produced via twin-roll strip casting

In this study,morphological and microstructural analyses were conducted on net-shaped microcracks appearing on the surface of low-carbon steel manufactured via twin-roll strip casting. The fractograph and microscale distribution of elements in the cracked region were also analyzed. Results revealed that the cracked surfaces were characterized by slight pits,along with inclusions composed of manganese and silicon oxide distributed along both the sides of the cracks. Fractograph analysis revealed that the crack and smooth dendrite surfaces were oxidized. These phenomena indicate that microcracks on the cast strip surface form at the hightemperature stage of the solidification process during twin-roll casting and rolling. Microcracks were present in each region with pits in the cast strip and extended along the dendrite interface because of the combined effects of phasechange stress,thermal stress,mechanical stress,and fractional crystallization during the solidification process.     

双辊薄带钢连铸侧封技术研究

侧封问题是双辊薄带连铸技术的一个关键性问题。分固体板侧封和电磁侧封两个方面综述了侧封技术的发展状况,分析了它们的优缺点。     

Study of measurement and control of free loop of hot steel strip in twin-roll strip casting

In the twin-roll strip casting process,hot cast strips can be broken or torn if the casting speed does not match the rolling speed.Usually,a certain length of hot steel strip is hung freely between the caster and rolling mill to deal with the effect of this speed difference.In this paper,the freely hanging hot steel strip is referred to as the free loop of hot steel strip.Accurately measuring and controlling the height of this free loop is the key factor in maintaining a stable casting operation.Several methods for measuring the loop height of a steel strip are discussed and a method for accurately measuring and controlling the free loop height of hot steel strip is presented.Based on the results of the casting loop quantity change curve,this control method is confirmed to be effective and able to meet the requirements of continuous casting strip production.     

A unified computational model for surface texturing process of strip casting rollers

A new unified computational method is proposed for modeling the relationship between the parameters of the high-speed particle-impact texturing process and the final surface morphology of the casting roller. The whole surface-texturing process is divided into three parts. The first part is the acceleration process of particles inside and outside the nozzle,which can be analyzed using the computational fluid dynamics method to obtain the particle impact velocities. The second part is a simulation of the bombardment process of particles onto the roller surface using the LS-DYNA software as the analysis tool and the results obtained in the first part as input parameters. The last part is the continuously random impact process of particles on the casting roller surface to form a functional surface,which is characterized by a simplified roughness model. Finally,the above three parts are combined to establish a unified computational model,the performance of which is successfully verified in a series of experiments.     

双辊薄带连铸侧封装置探讨

结合已公开的文献资料及专利,对国际上领先的Castrip、Eurostrip、新日铁等几家薄带连铸的侧封装置进行技术特点分析,着重介绍了Castrip侧封装置的技术演变。通过分析各家侧封装置的技术共性与特性,对侧封装置的设计思路进行了探讨。     

Three-dimensional thermal model for vertical direct chill slab casting process

To aid in the designing of an automatic control system, a steady state three-dimensional (3D) thermal model is developed to predict the temperature distributions for an industrial scale vertical direct chill (DC) slab caster for aluminium alloy AA-1050. A single domain approach for the liquid, mushy and solid regions is used by employing the enthalpy porosity technique. The convective heat transfer in the liquid region is taken into account by assuming a slag flow velocity field equal to the casting speed. The predicted thermal field is verified with the numerically predicted temperature field available in the literature and a reasonably good agreement is found. Detailed parametric study is carried out by varying important parameters of this process. Results of the temperature field, sump depth, mushy zone thickness, shell thickness and local surface heat flux are presented and discussed.

Afin d’aider à la conception d’un système de contrôle automatique, on a développé un modèle thermique à 3D en régime permanent pour la prédiction des distributions de température d’une machine de coulée verticale de brames par refroidissement intense et continu (DC) à l’échelle industrielle, pour l’alliage d’aluminium AA-1050. On utilise une approche à domaine unique pour la région liquide, la région pâteuse et la région solide au moyen de la technique d’enthalpie et porosité. On tient compte du transfert de chaleur par convection dans la région liquide en assumant un champ de vitesse d’écoulement de laitier égal à la vitesse de coulage. On vérifie le champ thermique prédit au moyen du champ de température prédit numériquement dans la littérature et l’on obtient un accord raisonnable. On effectue une étude paramétrique détaillée en faisant varier les paramètres importants de ce procédé. On présente et discute les résultats du champ de température, de la profondeur du refoulement, de l’épaisseur de la zone pâteuse, de l’épaisseur de la coquille, et du flux thermique local à la surface.     

宽1500 mm的镁合金双辊连铸铸嘴结构的研究

铸嘴结构是形成镁合金熔体流场的决定因素,其出口处流体速度分布的均匀与否直接影响铸坯质量的优劣。以宽度1500 mm的镁合金水平双辊连铸铸嘴结构为研究对象,对不同型式铸嘴结构内镁合金熔体的流场进行数值模拟计算,分析铸嘴长度、侧壁形状、尾迹区长度对铸嘴出口处流体速度分布均匀性的影响。结果表明：长度越长,铸嘴出口处流体速度分布越均匀;采用渐扩式侧壁的铸嘴结构能获得更均匀的流体速度分布;尾迹区越长,流体速度分布越均匀。