钢铝复合车身曲面结构感应-滚压连接机理与工艺研究

With the continual improvement of the performance requirements on safety, environmental protection and energy saving for automobile, high-strength and light-weight become the main characteristics of automobile body, the applying of composite structure of steel and aluminum is a significant method to meet the requirement of automobile body combination properties. Because of the complicated curved surface and the thin thickness on the joint of steel-aluminum, the present welding method on dissimilar metal is hard to meet the requirement of stable quality and mass production connection on automobile body. A novel method of induction-rolling connection on hybrid structure of automobile body curved surface and steel-aluminum dissimilar metal is presented. The coupling mechanism between electromagnetic, temperature and thermal stress fields during the induction heating process and temperature, stress and strain fields during the rolling process in the case of steel-aluminum dissimilar metal, automobile body curved surface, electromagnetic and kinematics parameters of inductor, mechanics parameters of rolling device will be investigated. The mechanisms of the interfacial atomic diffusion and the intermetallic compound growth and the forming laws of microstructure, mechanical performance in the case of eddy current heating from the boundary between steel and aluminum will be revealed. The forming theoretical and process design method will be built for induction-rolling connection on hybrid structure of automobile body curved surface and steel-aluminum dissimilar metal. The research results will contribute to developing the methodology of digitization, low-cost and high adaptability for the components with complicated shape and thin thickness, which are of great significance in both academic field and engineering practice.

随着汽车节能、环保、安全性能要求的不断提高，高强度和轻量化成为车身结构的主要特征，使用钢铝混合结构是满足当前车身综合性能需求的重要途径。因车身钢铝连接处厚度薄且形状复杂，现有的焊接方法难以满足车身质量稳定、大批量的连接需求。项目提出钢铝复合车身曲面结构感应-滚压连接新方法，研究感应器空间非线性运动过程中钢铝异种材料、车身曲面结构、感应器电磁学及运动学参数、滚压装置力学参数等多因素作用下感应加热电磁场、温度场和热应力场以及滚压温度场、应力场和应变场之间的耦合作用机理，揭示钢铝界面涡流生热条件下界面原子的扩散机理、金属间化合物的生长机制以及滚压过程微观组织和力学性能的形成规律，建立钢铝复合车身曲面结构感应-滚压连接成形理论和技术设计方法。研究成果将为复杂形状的薄板件数字化、低成本、高适应性连接技术提供科学依据，具有重要的学术价值和工程实际意义。

本项目紧密结合汽车轻量化的重大需求，针对钢铝复合车身结构连接成形技术关键问题，突破传统异种金属连接成形技术，将数字控制技术、感应加热技术以及滚压技术相结合，提出钢铝复合车身结构感应-滚压连接成形新方法。通过理论分析、数值模拟、连接成形实验、组织性能测试等手段，围绕钢铝复合结构连接成形关键科学问题开展探索研究。建立了钢铝复合结构感应-静/滚压连接成形试验平台，形成了钢铝复合结构感应-静/滚压连接成形装备；研究了钢铝复合结构感应-静/滚压连接成形过程电磁场和温度场的分布规律，揭示了电源功率、移动速度等工艺参数对界面磁感应强度、温度分布及均匀性的影响规律，阐明了感应-静/滚压连接成形过程中钢铝界面的原子扩散机理和金属间化合物的形成机制，构建了感应-静/滚压连接成形界面金属间化合物厚度预测模型；研究了钢铝复合结构感应-静/滚压连接成形过程微观组织和力学性能的形成规律，揭示了不同合金元素及电源功率、滚轮压力等工艺参数对界面金属间化合物厚度及种类、强度及硬度等的影响规律，阐明了钢铝复合结构感应-静/滚压连接接头的断裂机制；在上述研究基础上，形成了钢铝复合结构感应-静/滚压连接成形理论与技术设计方法。研究成果可为钢铝复合车身结构连接技术以及钢铝复合板的成形制备提供重要科学依据，具有广阔的应用前景。