冷轧高强钢板带热处理过程板形变化规律研究

发布时间：2018-09-07 11:56

【摘要】：高强度钢在建筑、交通、桥梁、船舶、工程机械、输油气管道、大型塔架结构以及国防装备等众多领域具有广泛应用前景。冷轧高强钢板带热处理过程的板形问题是制约其进一步提高质量的主要生产技术难题。因此,本文依托国家自然科学基金面上项目“超高强度钢板平整与矫直加工过程残余应力控制的基础研究”,对有初始板形缺陷冷轧高强钢板带热处理过程的板形变化规律进行研究,揭示热处理过程板形演变机理,获得热处理过程的板形变化规律,提出高强钢板带热处理过程板形控制策略,为冷轧高强钢板带热处理生产工艺优化提供理论支持。本文的主要内容和研究成果如下。 (1)对DP780钢和22MnB5钢进行了等温拉伸实验,建立了一种耦合应变硬化效应和温度软化效应的改进Johnson-Cook本构模型,将该本构模型进行数值实现并基于ABAQUS软件进行了数值模拟,对典型拉伸实验过程进行建模及仿真再现,模拟结果与实验结果吻合较好。 (2)建立以上两种高强钢考虑应力影响的相变动力学及相变塑性模型和考虑相变及温度影响的弹塑性本构模型,并通过对ABAQUS软件二次开发,实现了针对以上两种高强钢热处理过程的温度场与组织场及应力应变场多场耦合的数值模拟,通过22MnB5钢淬火、DP780退火的热模拟实验,验证了两种热处理过程多场耦合有限元模型。 (3)针对已瓢曲22MnB5板带,仿真研究了板形瓢曲缺陷在热处理过程中的演变机理,发现带钢宽度方向上的温度梯度和依先后顺序相变引起了带钢宽度方向的纵向延伸不均进而导致了板形瓢曲的改变,获得张力、初始横向温差等工艺参数对其板形变化的影响规律,提出了相应板形控制策略。 (4)针对已翘曲22MnB5板带,仿真研究了板形翘曲缺陷在热处理过程中的演变机理,发现带钢厚度方向上的温度梯度和依先后顺序相变引起了带钢厚度方向的纵向延伸不均进而导致了板形翘曲的改变,获得张力、初始厚向温差等工艺参数对其板形变化的影响规律,提出了相应板形控制策略。 (5)在实验室条件下,设计搭建了淬火实验系统,分别对有瓢曲和有翘曲22MnB5钢板进行了淬火实验,研究了淬火对瓢曲和翘曲的影响,实验较好验证了仿真模型及结果。
[Abstract]:High strength steel is widely used in many fields, such as construction, transportation, bridge, ship, construction machinery, oil and gas pipeline, large tower structure and national defense equipment. The flatness of cold rolled high strength steel strip during heat treatment is the main technical problem restricting the further improvement of its quality. Therefore, this paper relies on the project of National Natural Science Foundation of China, "basic research on residual stress control in the process of leveling and straightening of ultra-high strength steel plate". In this paper, the shape changing law of cold rolled high strength steel strip with initial shape defect is studied, and the shape evolution mechanism of heat treatment process is revealed, and the shape change law of heat treatment process is obtained. The flatness control strategy during heat treatment of high strength steel sheet and strip is put forward, which provides theoretical support for optimization of heat treatment process of cold rolled high strength steel sheet and strip. The main contents and results of this paper are as follows: (1) the isothermal tensile tests of DP780 and 22MnB5 steels are carried out, and an improved Johnson-Cook constitutive model coupled with strain-hardening effect and temperature-softening effect is established. The constitutive model is numerically realized and simulated based on ABAQUS software. The typical tensile experiment process is modeled and simulated. The simulation results are in good agreement with the experimental results. (2) the transformation kinetics and transformation plasticity model of the two kinds of high strength steels are established, and the elastoplastic constitutive model considering the effect of phase transition and temperature is established. Through the secondary development of ABAQUS software, the numerical simulation of the coupling of temperature field, microstructure field and stress-strain field in the heat treatment process of the two kinds of high strength steels is realized, and the thermal simulation experiment of 22MnB5 steel quenched with DP780 annealing is carried out. The multi-field coupling finite element models of two kinds of heat treatment processes are verified. (3) the evolution mechanism of plate shape curling defects in heat treatment process is simulated and studied for the 22MnB5 plate and strip that have been curled. It is found that the temperature gradient in the width direction and the phase transformation in sequence lead to the uneven longitudinal extension in the width direction of the strip, which leads to the change of the shape of the strip, and the tension is obtained. The influence of process parameters such as initial transverse temperature difference on the shape of the strip is studied, and the corresponding shape control strategy is proposed. (4) the evolution mechanism of the shape warping defect in the heat treatment process is studied by simulation for the 22MnB5 strip. It is found that the temperature gradient in the direction of strip thickness and the phase transformation in sequence lead to the uneven longitudinal extension in the direction of strip thickness, which leads to the change of the shape warpage of the strip, and the tension is obtained. The influence of the process parameters such as initial thickness temperature difference on the shape change of the plate is presented. (5) the quenching experiment system is designed and built under the laboratory conditions. The effects of quenching on the bending and warping of 22MnB5 steel plate were studied, and the simulation model and results were verified.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG162.8;TG335.5

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