基于全幅宽残余应力分布的大宽厚比板带热轧板形基础模型研究

A large width-thickness ratio and zero residual stress are the goals of the strip production. The larger the width-thickness ratio is, the more complex the deformation behaviors of strip rolling and buckling are, the more difficult the shape control will be. In order to solve the problems of complex shape defect in shape control of hot-rolled strip with a width-thickness ratio greater than 700, considering the uneven temperature distribution along width, and also the phase transformation and property difference resulted from the uneven temperature distribution, a strip/roll stack integrated deformation model and a strip buckling model are established respectively. A full coupled rolling/buckling model is realized by Arlequin algorithm to set up the efficacy functions of flatness actuators to the residual stress distribution. Using Hamilton symplectic method, the analytical model of quantitative relationship between the strip residual stress distribution and manifested flatness is established. A target curve of the residual stress distribution which considers laminar cooling and the requirements of subsequent process is compared to the actual residual stress distribution curve gained by the manifested flatness measured on-line out of the bite, and the residual stress distribution deviation curve throughout the strip width is obtained. By the efficacy functions multiplier and optimization algorithm, the value of flatness actuators can be finally determined. These research work sets up the basic shape models for hot-rolled strip with large width-thickness ratio based on the residual stress distribution throughout the strip width, which provide theoretical support for the production of high quality steel plate without the residual stress.

大宽厚比、零残余应力是板带生产追求的目标。宽厚比越大，板带轧制和屈曲变形行为越复杂，板形控制越难。为了解决宽厚比大于700的热轧板带生产中存在复杂板形缺陷的问题，考虑板带宽度方向温度分布不均及由此而带来的相变组织及性能差异，分别建立辊系-轧件一体化变形模型和板带屈曲变形模型，通过编写Arlequin算子程序，实现板带轧制-屈曲变形行为的完全耦合，建立板形调控机构对残余应力分布的功效函数；利用Hamilton辛求解方法建立轧后板带残余应力分布和浪形转化解析模型，得到浪形特征与残余应力分布定量关系；建立考虑层流冷却及后续工序要求等的残余应力分布目标曲线，与利用轧后实测浪形转化而得的残余应力分布曲线比较，得到板带全幅宽残余应力分布偏差曲线，乘以功效函数并经优化后可得板形调控机构执行值。本项目建立了基于全幅宽残余应力分布的大宽厚比板带热轧板形基础模型，为生产无残余应力高品质板带产品提供了理论支撑。

大宽厚比板带是具有很高附加值的产品，是非常重要的工业基础原材料。宽厚比大于700的板带轧制过程中板形控制难度大，轧后板形质量异议多，相关理论还需完善。对大宽厚比板带生产过程各个环节中的板形产生机理进行深入研究，对提高板带产品质量和实现板带全幅宽的综合板形质量控制、实现无残余应力的高端板带生产具有重要意义。本课题通过对热精轧过程、轧后冷却过程、平整机轧制过程和板带纵切过程中存在的板形问题进行较为系统的理论研究，部分成果得到工业验证和应用，丰富和发展了大宽厚比板带在整个生产流程中的板形控制理论，主要研究内容和成果包括：建立了大宽厚比板带轧制的辊系-轧件一体化耦合变形模型，揭示了相变组织、相变潜热、热膨胀、相变膨胀和板带初始内应力对横断面轮廓的影响以及板带横向温度不均和相变不均对热精轧屈曲行为的影响；建立了考虑机架间轧件变形的板带内应力演变快速计算模型，揭示了机架间板带弹性回复和应力松弛对精轧板带板形的影响，并在此基础上开发了电工钢板形控制的锥形辊技术和相应的窜辊策略，显著提升了其板形质量；开发了热轧轧后冷却多尺度耦合仿真模型，揭示了精轧出口层流冷却工艺及卷后冷却过程对板带板形的影响；建立了小辊径、大长径比工作辊热轧平整机的辊系-轧件一体化耦合模型，获得了不同工况下平整机的板形调控特性，为改善高强钢平整过程出现的复杂板形问题奠定了理论基础；建立了高强钢板带纵切过程有限元仿真模型，揭示了残余应力分布形式、纵切条数和不同切边量对纵切后板带侧弯的影响规律；建立了基于Hamilton体系的板带局部纵向屈曲和内应力场求解的辛弹性力学解析模型，新模型求解精度大于传统能量法和半逆解法，求解时间远小于有限元法。通过对大宽厚比板带全流程生产过程的不同生产工序中板形问题的研究，建立了考虑全幅宽残余应力分布演变的大宽厚比板带的板形基础模型，为生产无残余应力的高品质板带产品提供了重要的理论支撑。