特厚板差温轧制力学机理及缺陷消除判据研究

It is an essential problem to be solved to close the central defect of a continuous casting thick billet and curtail lateral double bulging during ultra-heavy plate rolling. The gradient temperature rolling is the effective method to solve the problem. However, because the modeling and calculation of the gradient temperature rolling are difficult, the corresponding defect elimination criterion and the quantitative relationship between the causal parameters are difficult to be obtained. From the standpoint of energy analysis, the present project intends to describe the temperature field and velocity field of the billet as well as the width spread function during the gradient temperature rolling and to establish the curtail criterion of double bulging by the theoretical analysis and finite element simulation as well as the experimental investigation. Simultaneously, the replacement method of specific plastic work rate will be adopted to solve for the rolling energy rate functional, and the rolling force model by the variational method and the subsequent defect closure criterion will be obtained. Based on these works, the parameters and their relationships between defect closure and double bulging shrinkage will be analyzed collaboratively, a comprehensive criterion that can eliminate the two mentioned defects will be obtained by the optimization of the feasible direction method, and the experimental validation and finite element comparison analysis will be carried out. By this project, the mechanical mechanism of gradient temperature rolling can be disclosed, and the inherent scientific law between the process parameter and the microstructures and mechanical properties can be clarified. The present result can be used to optimize the process parameters of gradient temperature rolling, and can provide the theoretical support for improving plate quality and yield.

对连铸厚坯芯部缺陷进行压合并缩减侧边双鼓形是特厚板轧制中必须要解决的问题。差温轧制是目前解决此问题的有效方法。然而，由于差温轧制的建模与求解困难，导致缺陷消除判据以及参数变化规律的研究欠缺。本项目从能量解析的角度出发，综合运用理论解析、有限元模拟以及实验的方法描述差温轧制的坯料温度场与速度场，构建宽展函数表达式，从而导出双鼓形缩减判据。同时，以比塑性功率取代法和共线矢量内积法解出轧制能率泛函，以变分法获得轧制力模型，并进一步导出缺陷压合判据。在此基础之上，协同分析影响缺陷压合与双鼓形缩减的各个参数及其相互关系，以可行方向法优化出两种缺陷消除的综合判据，并进行相应的实验验证与有限元对比分析。通过以上研究，将揭示差温轧制的力学机理，阐明工艺参数与板材组织力学性能间的内在科学规律。项目成果可用来优化差温轧制工艺参数，进而为提高板材质量和成材率提供理论支撑。

差温轧制技术能够有利于消除特厚板质量缺陷。然而，由于差温轧制过程属于复杂的热力耦合过程，其受热变形的物理场难以准确描述、多参数交互影响的非线性能率泛函难以积分求解，导致工艺优化用轧制力模型、缺陷消除判据难以准确建立，生产控制无据可依。项目以能量解析、有限元模拟以及对照实验相结合的方法分析了特厚板的热变形规律，建立了满足运动许可条件且具有光滑流动特性的速度场，构建了考虑温度梯度影响的能率泛函，提出了求解复杂非线性比塑性功率的两个独特方法，导出了轧制力的解析模型以及缺陷压合判据，定量揭示了主要工艺参数对模型与判据的影响机理，为提高板材质量提供了理论和技术支撑。.项目实施3年以来，发表基金资助SCI论文9篇、EI论文1篇，包含本领域一区TOP期刊Computers and Mathematics with Applications 1篇、二区Journal of Manufacturing Processes 1篇。研究成果被Materials Today、Journal of Alloys and Compounds、International Journal of Solids and Structures等高水平SCI期刊引用与肯定；出版基金资助专著1部；授权国家发明专利2项；受邀作分会场特邀报告3次；培养毕业研究生2名。.项目严格按照研究计划，圆满完成立项发表SCI/EI论文6-9篇、申请国家发明专利2-3项、出版专著1部的预期目标。已取得的主要创新成果及其科学意义如下：.（1）提出以特殊十二边形逼近Mises圆的新思想，导出了原创性的MS、CA屈服准则及其线性比能率，并由此提出比能率取代法，解决了非线性Mises比能率以常规方法难以求解的关键性难题，导出了比传统近似模型更加可靠的轧制力模型，提升了板材厚度的控制精度。.（2）以流线光滑的逻辑函数描述了变形区金属流动的运动学规律，数学表达了特厚板的厚向温度分布，成功导出了包含温度梯度影响的轧制能率泛函解析式，获得了差温轧制力解析模型，定量揭示了厚向温差、压下率、坯料尺寸等对模型与判据的影响机理，为工艺参数的优化提供了科学依据。.（3）提出从能量解析角度定量分析厚板中心缺陷压合行为的新路径，建立了含缺陷速度场，明确了缺陷演变的力学机理，导出了比现有估算式更加符合实际的压合判据，显著提升了板材质量。