大型轴类零件快锻精密成形理论与实验研究

Based on the disadvantage of current processing techniques for heavy shaft forging such as large machining allowance, low dimension accuracy, materials and energy consumption, a new precision high-speed forging forming process where heavy shaft is clamped by two manipulators is proposed. By theory analysis, numerical simulation and experiment research, metal flow rule and the deformation mechanism during high-speed forging of heavy shaft forming are elaborated . Plastic deformation behavior and microstructure evolution mechanism of the billet during the thermal-mechanical couple deformation are studied by thermal simulation experiment. Effect of high-speed forging process parameters on forming quality of heavy shaft is researched and the process parameters are optimized in order to improve forming precision and decrease machining allowance.Numerical model and physical model are established during the forging process.Defect production and evolution mechanism is analyzed. Effect of distribution of stress and strain on inner defect closure is revealed so as to realize grain refinement and eliminate organization defects. Parameter matching between high-speed forging hydraulic machine and manipulators is also discussed. The influence mechanism of heavy shaft forming quality under different equipment parameters is researched and methods to improve the forming quality are put forward. Precision forming process theory of heavy shaft is established in order to increase productivity and reduce production cost. A new and high efficiency theory, process and method are provided for precision forming and mass production of heavy shaft parts.

针对大型轴类零件成形过程存在的加工余量大、尺寸精度低、浪费能源和材料等问题，提出一种双操作机夹持大型轴类零件快锻精密成形新工艺。采用理论分析、数值模拟和实验研究相结合的方法，研究轴类件快锻工艺中金属流动过程揭示其变形机制。采用热力模拟实验，探明钢坯在热力耦合变形过程中的塑性变形行为和组织演变机理；分析快锻工艺参数对轴类件成形质量的影响，优化工艺参数，达到提高轴类件成形精度，减小加工余量的目的；建立锻造过程中轴类件缺陷数值模型及物理模型，分析轴类件快锻过程缺陷产生及演变机理，揭示锻造过程中应力应变分布对心部缺陷焊合的影响，实现细化晶粒，消除组织缺陷的目的；分析快锻机与双操作机之间的参数匹配，提出轴类件精密成形过程中设备参数对轴类件质量的影响机理及提高质量的方法。建立大型轴类件快锻精密成形工艺理论，提高生产效率、降低生产成本，为大型轴类零件精密成形和批量生产提供一套新的高效的理论、工艺与方法。

针对大型轴类零件成形过程中存在的加工余量大、尺寸精度低、浪费能源和材料等问题，提出一种列车车轴快锻精密成形新工艺。通过热模拟实验，研究了车轴钢热成形过程中的金属流动特性、变形行为及动态再结晶。建立了车轴钢的本构模型、确定了特征应力应变及动态再结晶模型。构建了车轴钢热加工图，为工艺参数选择奠定了基础。分析了热成形过程中的动态再结晶动力学，探明了工艺参数对动态再结晶的影响规律，深入分析了Zener-Hollomon参数对动态再结晶影响机理。针对列车车轴快锻加工工艺，建立了有限元模型，分析了型砧结构形状对成形质量的影响，以锻件内部应变状态及应力分布为依据，优化了型砧结构。对锻造过程中工艺参数对锻件成形质量的影响进行了分析，以锻件成形质量为目标对锻造工艺进行了优化。基于物理冶金学及曲率驱动机制，建立了车轴钢热加工过程中的元胞自动机模型，研究了车轴钢加热过程中晶粒长大及热变形过程中动态再结晶微观组织演变机理。 以位错密度随应变的变化为主线，模拟获得了不同变形量、应变速率、变形温度及初始晶粒尺寸条件下LZ50钢的流变行为及动态再结晶行为，并与实验结果做对比，揭示了车轴钢热加工过程中的微观组织演变机理。建立了大型轴类零件快锻精密成形工艺的基本理论，为提高生产效率、降低生产成本提供理论依据。