环形零件铸辗复合成形新工艺裂纹缺陷与控制理论研究

The new casting-rolling compound process is a high efficient production process of metal ring parts with many merits such as saving energy, saving materials and reducing the emission of carbon dioxide. In the new process, a ring casting blank without forged is ring rolled directly on the ring rolling machine. Several challenges must to be solved. One of them is that cracks could occur during the ring rolling process. The production quality is affected severely. Theoretical analysis, numerical simulation and experimental research were organically combined to research deeply the initiation and propagation mechanics of cracks. The ring part in ring rolling process was analyzed mechanically. The load condition of the initiation is obtained. Fracture mechanics were used to analyze the initiation condition of the crack and its propagation process during ring rolling. Its mathematical model is built. Numerical Simulation and experiments are used to research the influence of microstructure, small defects of cast blank and the defects dislocation on the initiation and propagation of the crack. The influence rule of the rolling parameters including rolling temperature, the feed speed of core-roller, friction coefficient and rotate speed of the drive roller on the initiation and propagation of cracks are also investigated. The optimized rolling parameters are obtained. A method is obtained to control effectively the initiation and propagation of the cracks. Controlling theory on crack during hot ring rolling based on cast blank is build. The work will provide theory and technology support for the new casting-rolling compound process.

环形零件铸辗复合成形新工艺是一种高效、节约材料、节约能源、降低环境污染的新工艺。新工艺利用铸坯直接辗扩成形环形零件，存在诸多的科学问题需要解决，其中铸坯热辗扩过程中的开裂直接影响环件质量。本项目通过理论分析、数值模拟和实验研究有机结合的方法对铸坯热辗扩中的开裂问题进行深入的研究。对热辗扩过程环件力学分析，研究裂纹产生部位受力状态，获得裂纹产生的受力条件。运用断裂力学理论研究裂纹产生与扩展机理，建立裂纹产生及扩展的数学模型。对裂纹扩展过程进行数值模拟和实验，研究铸态组织、铸坯微缺陷、缺陷位置等对裂纹产生及扩展的影响；研究热辗扩工艺参数（如辗扩温度、辗扩进给量、摩擦系数、驱动辊转速等）对裂纹产生和扩展的影响规律，获得优化的热辗扩工艺参数。提出有效的热辗扩过程中裂纹产生和扩展的控制方法，建立铸坯热辗扩裂纹控制理论，为新工艺的推广应用提供理论技术支撑。

环形零件铸辗复合成形新工艺是一种高效、节约材料、节约能源、降低环境污染的新工艺。新工艺利用铸坯直接辗扩成形环形零件，存在诸多的科学问题需要解决。其中铸坯热辗扩过程中的开裂直接影响环件质量。项目通过理论分析、数值模拟和实验研究方法，对铸辗复合成形过程中裂纹产生与发展进行了研究。研究了离心铸造过程，获得了控制裂纹产生的离心铸造方法。研究了42CrMo钢热塑性行为，确定了铸态42CrMo钢的易裂敏感温度区间。对热辗扩过程环件力学分析，获得了裂纹产生部位受力状态。研究了热辗扩工艺参数（如辗扩温度、辗扩进给量）对微观组织，裂纹产生的影响规律，获得优化的热辗扩工艺参数。提出了有效的环坯铸造和热辗扩过程中裂纹产生和扩展的控制方法，为新工艺的推广应用提供理论技术支撑。