【作者】 李向阳；

【导师】 李自良；

【作者基本信息】 昆明理工大学 ， 机械工程（专业学位）， 2024， 硕士

【摘要】 诸如行李运输机辊子组件等结构常用不同的钢材制造其轴头和筒体零件,从而实现不同的性能要求。但由于异种钢在力学性能和化学性能上存在差异,常规焊接方法得到的焊接接头的质量难以控制,容易出现缺陷。连续驱动摩擦焊是一种成熟且高效的固态焊接技术,对异种材料焊接过程中的质量控制具有很大的优势。本文通过数值模拟与实验相结合的方法,对20钢和45钢的连续驱动摩擦焊进行了研究,深入分析焊接接头的组织性能及其形成机制,探讨最佳工艺参数,为提高焊接质量提供了科学依据,也为后续的数值模拟提供了参考。论文的具体工作内容及得到的结论如下:(1)采用相似理论构建辊子结构三维模型,利用Abaqus软件模拟20钢和45钢管形结构的连续驱动摩擦焊过程。该模型结合库伦摩擦模型和剪切摩擦模型来描述在不同摩擦阶段中的摩擦特性,展现了焊接不同阶段温度场、应力场和轴向缩短量的动态变化。之后通过对轴向缩短量和飞边形貌的筛选,选择出合适的工艺参数的范围。并对比合适的工艺参数范围内的模拟方案,综合分析温度场、应力场和轴向缩短量随时间变化的趋势和形成机制。(2)通过数值模拟筛选出的最佳工艺参数范围进行试验,对焊接过程中的扭矩与温度的关系进行论证,得出不同主轴转速产热能力的变化规律。将试验过程的温度与数值模拟过程的温度进行对比,发现数值模拟结果由于简化了部分热量交换条件,使得温度在不同时间段均略高于试验采集的温度。对比试验得到的轴向缩短量与数值模拟计算的轴向缩短量,由于数值模拟过程中的温度略高于试验,所得到的轴向缩短量结果也略大于试验,其中数值模拟结果与试验结果的最大的绝对误差为0.72 mm,相对误差为6.36%。说明所建立的连续驱动摩擦焊的有限元模型能够较准确的反映出焊接的实际过程。(3)对不同工艺参数范围内试验获取的焊件接头的外观形貌、显微硬度和抗拉性能进行分析,得出采用主轴转速为1300 r/min,摩擦压力为60 MPa、摩擦时间为8 s、顶锻压力为120 MPa以及顶锻时间为2 s时,工艺参数最佳。焊接接头的硬度呈现倒“V”型分布,其中焊缝区的硬度达到最高,热影响区的硬度次之,最高的硬度值达到253.6 HV。抗拉伸强度为523.9 MPa,超过了20钢母材的抗拉强度,达到了45钢母材抗拉强度的87.3%。对焊接接头的微观组织进行分析,焊缝区发生了再结晶和相变现象。通过对接头拉伸断裂处的扫描电镜观察(SEM),发现断口具有大量的韧窝,主要的断裂形式是韧性断裂。更多还原

【Abstract】 Structures such as roller assemblies for baggage conveyors often use different steels to manufacture their shaft heads and barrel parts to achieve different performance requirements.However,due to the differences in mechanical and chemical properties of dissimilar steels,the quality of welded joints obtained by conventional welding methods is difficult to control and is prone to defects.Continuous drive friction welding is a wellestablished and efficient solid-state welding technology that has great advantages for quality control during the welding of dissimilar materials.In this thesis,the continuous drive friction welding of 20 steel and 45 steel is studied by combining numerical simulation and experiment,and the microstructure and formation mechanism of welded joints are analyzed in depth,and the optimal process parameters are discussed,which provides a scientific basis for improving the welding quality and a reference for subsequent numerical simulation.The specific work content of the thesis and the conclusions obtained are as follows:(1)The three-dimensional model of the roller structure was constructed by using the similarity theory,and the continuous drive friction welding process of 20 steel and45 steel tubular structures was simulated by Abaqus software.The model combines the Coulomb friction model and the shear friction model to describe the friction characteristics in different friction stages,and shows the dynamic changes of temperature field,stress field and axial shortening in different stages of welding.Then,by screening the axial shortening amount and flash topography,the appropriate range of process parameters is selected.The trend and formation mechanism of temperature field,stress field and axial shortening with time are comprehensively analyzed compared with the simulation scheme within the appropriate process parameters.(2)The optimal range of process parameters screened out by numerical simulation is tested,and the relationship between torque and temperature in the welding process is demonstrated,and the variation law of heat production capacity of different spindle speeds is obtained.The temperature of the test process is compared with the temperature of the numerical simulation process,and it is found that the temperature of the numerical simulation results is slightly higher than the temperature collected in the experiment at different time periods due to the simplification of some heat exchange conditions.Comparing the axial shortening obtained by the test with the axial shortening calculated by numerical simulation,the axial shortening results obtained are slightly larger than those of the test because the temperature in the numerical simulation process is slightly higher than that of the test,and the maximum absolute error between the numerical simulation results and the test results is 0.72 mm,and the relative error is 6.36 %.It shows that the finite element model of continuous drive friction welding can accurately reflect the actual welding process.(3)The appearance,microhardness and tensile properties of the weldment joints obtained by the test within the range of different process parameters were analyzed,and it was concluded that the best process parameters were obtained when the spindle speed was 1300 r/min,the friction pressure was 60 MPa,the friction time was 8 s,the topforging pressure was 120 MPa and the top-forging time was 2 s.The hardness of welded joints presents an inverted "V" shaped distribution,in which the hardness of the weld zone reaches the highest,followed by the hardness of the heat-affected zone,and the highest hardness value reaches 253.6 HV.The tensile strength is 523.9 MPa,which exceeds the tensile strength of 20 steel base metal and reaches 87.3 % of the tensile strength of 45 steel base metal.The microstructure of the welded joint was analyzed,and recrystallization and phase transformation occurred in the weld area.Through scanning electron microscopy(SEM)observation of the tensile fracture of the joint,it was found that the fracture had a large number of dimples,and the main fracture form was ductile fracture.更多还原