热轧带钢轧后板形演变规律研究

发布时间：2018-06-25 08:30

本文选题：热轧 + 带钢　；参考：《北京科技大学》2017年博士论文

【摘要】：热轧带钢生产中时常存在精轧出口检测到的板形良好,在冷却后开卷时却出现浪形和横弯板形缺陷的情况。这种现象在采用快速冷却技术生产的热轧高强度带钢中更为突出,目前对其产生机理及演变规律缺乏统一认识。这个问题涉及轧后的层流冷却、钢卷冷却以及开卷等工序,既有宏观形变过程,又有微观相变过程,较为复杂。加之无在线检测仪表获得带钢、钢卷在冷却过程中的状态,大大增加了对此过程研究的难度。本文针对热轧带钢轧后出现的浪形缺陷和横弯缺陷,从不同工序对热轧带钢轧后两种板形缺陷产生的原因及其演变规律进行研究。本文主要内容和研究成果如下:(1)结合实际的冷却设备参数和冷却工艺,通过等温转变膨胀及动态CCT等实验及ABAQUS有限元软件的二次开发,精细考虑带钢初始温度分布、热物性参数、热交换边界条件及层流冷却过程中的相变及相变潜热等因素,建立了具有代表性的700 MPa级高强度热轧带钢层流冷却过程中温度、相变、应变/应力的多场耦合三维有限元模型,得到了快速冷却条件下带钢温度、相变、应力的演变规律及在带钢宽度方向上的分布。(2)以热轧带钢层流冷却耦合模型为基础,将卷后冷却过程加入模型,建立热轧带钢轧后冷却一体化模型,对热轧带钢从精轧温度冷却至室温过程中的温度、相变、应变/应力进行耦合求解。研究结果表明,卷后冷却过程对带钢浪形存在较大影响。利用热轧带钢轧后冷却一体化模型,对比分析了边部遮挡、稀疏冷却、微中浪轧制等多种手段对轧后带钢板形的改善效果,得到了与工业试验一致的最有效的板形优化工艺方案。(3)考虑温度及相变不均的影响,建立快速冷却条件下热轧带钢上下表面非对称冷却的多场耦合有限元模型,得到了层流冷却过程中带钢横弯的演变规律,系统分析了不同冷却工艺及参数对横弯的影响,改变了横弯是由层流冷却过程中带钢上下表面冷却不均导致的一般认识。在此基础上,建立了热轧带钢开卷过程的弹性力学解析模型和有限元模型,对带钢开卷过程中的力学变形行为进行分析,结合工业生产实测,得到了钢卷开卷过程中横弯产生的原因及其主要影响因素。
[Abstract]:In the production of hot rolled strip, the shape detected by finish rolling exit is good, but the wave shape and transverse bending shape defect appear when coiling after cooling. This phenomenon is more prominent in hot rolled high strength strip produced by rapid cooling technology. At present, there is a lack of a unified understanding of its formation mechanism and evolution law. This problem involves laminar cooling, coil cooling and unwinding after rolling, which is complicated by both macroscopic deformation process and micro phase transformation process. In addition, the steel coil is in the state of cooling process without on-line measuring instrument, which greatly increases the difficulty of studying this process. In this paper, the causes and evolution rules of the two kinds of strip defects after hot rolling are studied from different working procedures aiming at the wave shape defects and transverse bending defects after hot strip rolling. The main contents and research results are as follows: (1) considering the actual cooling equipment parameters and cooling process, the initial temperature distribution of strip steel is carefully considered through isothermal transformation expansion and dynamic CCT experiments and the secondary development of Abaqus finite element software. The temperature and phase transition during laminar cooling of 700 MPA grade high strength hot rolled strip steel were established by the parameters of thermal physical properties, boundary conditions of heat exchange, phase transition and latent heat of phase transition during laminar cooling. The multi-field coupled three-dimensional finite element model of strain / stress is used to obtain the strip temperature, phase transformation, stress evolution and width distribution under rapid cooling condition. (2) based on the laminar cooling coupling model of hot rolled strip. The integrated model of post-rolling cooling of hot rolled strip was established by adding the coiling process into the model, and the temperature, phase transformation and strain / stress of hot rolled strip from finishing temperature to room temperature were solved by coupling method. The results show that the cooling process after coiling has a great influence on the wave shape of strip. By using the integrated model of post-rolling cooling of hot rolled strip, the effect of edge occlusion, sparse cooling and micro-medium wave rolling on the improvement of the shape of the strip after rolling is compared and analyzed. The most effective optimization process scheme for strip shape is obtained in accordance with the industrial test. (3) considering the influence of temperature and phase change, a multi-field coupled finite element model for asymmetric surface cooling of hot rolled strip is established under the condition of rapid cooling. The evolution law of transverse bending of strip during laminar cooling is obtained. The influence of different cooling process and parameters on transverse bending is analyzed systematically, and the general understanding that transverse bending is caused by uneven cooling of upper and lower surface of strip during laminar cooling is changed. On this basis, the elastic mechanics analytical model and finite element model of strip uncoiling process are established, and the mechanical deformation behavior of strip uncoiling process is analyzed, combined with the actual measurement in industrial production. The causes and main influencing factors of transverse bending in the unwinding process of steel coils are obtained.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG335.56

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