【作者】 张小剑；

【导师】 刘小文；

【作者基本信息】 西北工业大学 ， 材料加工工程， 2004， 硕士

【摘要】 搅拌摩擦焊(FSW)是一种新型的固态焊接方法，被誉为“继激光焊后最为革命性的连接技术”。与传统的焊接方法相比，FSW方法完成的焊接接头性能优异，焊接变形小，残余应力小。因此，人们对许多材料进行了FSW焊接试验，希望能用FSW方法获得性能更加优异的焊接接头。由于铜及其合金具有很高的导热系数，使用传统的熔焊方法焊接通常是很困难的，焊接过程中需要很高的能量输入，而且焊接速度较低。因而，研究铜及其合金的FSW工艺将具有重要意义。本文针对3mm厚紫铜(T2)板与黄铜(H62)板异种材料的FSW进行了大量工艺试验，通过对接头外观成形、微观组织、拉伸弯曲性能及硬度等实验测量结果的分析，优化了搅拌头材料、形状尺寸以及旋转速度、压力、焊接速度等工艺参数。结果显示，焊合区为细小的等轴晶粒，其硬度介于紫铜与黄铜母材之间，接头拉伸强度等强甚至超强于紫铜母材。 FSW传热过程直接决定工件所经历的热循环，进而影响焊接接头的微观组织和力学性能。同时温度场的分析对于预测接头残余应力和变形，以及焊缝区硬度都具有重要意义。本文在前面的工艺研究基础上，分析了FSW的产热过程；根据搅拌头形状与尺寸，建立了FSW三维传热有限元模型。使用ANSYS有限元分析软件，结合有限几个测量点温度变化的实验数据，对6mm厚度紫铜板FSW焊接过程的温度场进行了有限元分析和计算，获得了该焊接过程的温度场分布与变化规律。计算过程中考虑了工件下表面与支撑板接触热传导对温度场的影响，以及温度对紫铜材料热传导系数的影响，有限元计算结果与实验测量结果接近。更多还原

【Abstract】 Friction Stir welding (FSW) is a relatively new solid state joining process. It is said to be "the most revolutionary joining method after Laser Welding". Compared with the conventional welding processes, friction stir welds show little deformation and low residual stress, and has good mechanical properties. Therefore, a lot of FSW experiments on many materials were carried out to obtain more powerful welds. Because of high thermal conductivity, welding of copper and its alloys is usually difficult by conventional fusion welding processes. The heat input required is much higher than that in almost other materials, and the welding speed is quite low. Thus, studying the feasibility of FSW for joining copper and its alloys is of great importance. In the study, pure copper (T2) and brass (H62) which has 3mm in thickness were welded by FSW. With the microstructure of the welds, micro hardness profile through the weld zone and corresponding tensile strength test data, the shape and dimension of the tool, the travel speed, the tool rotation speed and the welding pressure were optimized. The stir zone showed fine and equaxied grain structure, and the tensile strength of the weld is equal or higher than that of the pure copper base metal.The heat transfer process determines the thermal cycles in the work piece during the FSW, which affects the microstructure and mechanical properties. A good understanding of the heat transfer process in the work piece can be helpful in predicting the residual stress in the welding work piece and the hardness in the weld zone. A three-dimensional heat transfer model based on the tool shape for FSW is present in this paper. With the ANSYS finite element software and the limited measured temperature data, the temperature distribution of 6mm thick pure copper (T2) friction stir weld was analyzed. Heat transfer at the bottom surface of the welding work piece and the temperature-dependent thermal conductivity of the material were considered in the model. The numerical results are in good agreement with the experimental results.更多还原