镁合金宽幅板带轧制的温度/形变协调控制机理研究

Wide magnesium alloy sheets are potential structural materials applied to lightweight vehicles of transportation, and ingot casting and rolling process is an efficient procedure to produce them on a large scale at present. Because magnesium alloys are poor in plastic deformation coordination and excessively sensitive to strain rate and temperature, the smoothness of rolling procedure, the control over microstructures, properties, and sheet shapes are related to the high accurate control over heating/cooling between sheets and rollers and coordination with deformation. However, the systematic research of wide magnesium alloy sheets on thermal behavior during deformation, as well as the interplay between the thermal behavior and deformation, is limited so far. Based on the magnesium alloy sheets with 1500mm width, this project is aimed to identify the influencing factors, as well as variation laws, on temperature fields between the sheets and rollers by studying the thermal behaviors during each key process and between adjacent procedures. Simultaneously, a few influencing factors (e.g., the initial status of sheets, deformability characteristics, thermal effects, interface friction and lubrication) on sheets are taken into account so as to identify the effect of couple temperature fields between sheets and rollers, coupling relations, and other rolling conditions on tendency change of temperature in deformation zone and microstructures. Finally, the work will provide some basic data and models for realizing the control of microstructures, properties and shapes of wide magnesium alloy sheets by coordinating temperature and deformation parameters.

宽幅镁板带是交通工具轻量化的重要潜在基础结构材料，铸扁锭-轧制法是其目前能够大规模生产的高效工艺方法。由于镁合金的塑性变形协调能力差以及对变形速率及温度极其敏感的特点，决定了其轧制过程的顺利进行及其组织性能与板形控制，离不开对轧辊与板坯的加热/冷却的精准控制以及与变形的协调匹配，但目前缺乏对宽幅镁板带变形过程热行为及其与形变交互作用影响的系统研究。为此，本申请以宽幅1500mm镁合金板带各制备环节中的热行为及其在相邻工序间的交互作用为主线，明确宽幅板坯与轧辊的初始温度场的影响因素与变化规律，综合考虑铸造板坯初始冶金状态、金属塑性变形特性及其热效应、界面摩擦与润滑与传热特性等影响因素，明确板坯与轧辊的耦合温度场和其它轧制变形条件及其耦合关系对轧制变形区温度动态变化及其对微观组织结构的影响，为通过温度与变形工艺参数的协调匹配实现宽幅镁板带组织性能与板形的主动控制提供基本数据与模型。

扁铸锭-轧制法是目前能够大规模生产宽幅镁板带的高效工艺方法，然而镁合金的塑性变形协调能力差以及对变形速率和温度极其敏感，导致其轧制过程的顺利进行及其组织性能与板形控制，离不开对轧辊与板坯温度的精准控制以及其与变形的协调匹配，但目前缺乏对宽幅镁板带变形过程热行为及其与形变交互作用影响的系统研究。本项目采用热压缩实验以及轧制过程轧件温度跟踪与轧制力检测实验，采用空冷实时测温实验，采用镁合金轧制与矫直过程的实验与模拟，建立了轧制热力耦合有限元模型，并根据界面摩擦影响系数确定了镁板轧制力预报模型；根据镁合金的热变形行为及其在冷辊热轧过程中的传热行为和摩擦行为，揭示了宽幅镁合金板材轧制时轧件和轧辊的温度、变形分布与变化规律；根据镁板在辊道输送空冷过程中的温度行程及表观黑度模型，制定了有效控温(补热与降温)方法和板形调控策略，确定了近恒温轧制工艺；表征了镁合金弹塑性变形本构方程，改进了大压下轧制工艺；研究了轧制工艺对镁板边裂的影响，构建了镁合金轧制边裂的失效预判模型；探明了镁合金中厚板弯曲时的组织与织构特征，发展了宽幅镁板的辊式矫直工艺；明确了镁合金宽幅板带轧制温度/形变协调控制机理，为宽幅1500mm的镁合金板带的高质量、高精度、高成品率连续轧制提供了基础数据。