【作者】 曹朝霞；

【导师】 刘书华； 王德庆；

【作者基本信息】 大连铁道学院 ， 材料加工工程， 2002， 硕士

【摘要】 搅拌摩擦焊(FSW)是近年来由英国焊接研究所(TWI)发明的一种新型固相连接技术。同传统的熔化焊相比，其接头不会产生与熔化有关的一些如裂纹、气孔及合金元素烧损等焊接缺陷；焊接过程中无须填充材料、保护气体；焊接前无须进行复杂的处理工作；焊接时能量消耗比传统焊接方法低。此外，焊接过程中无弧光辐射、烟尘和飞溅，噪音低，因而搅拌摩擦焊是一种高质量、高效率、低成本的“绿色焊接方法”，具有广阔的应用前景。 目前，工业发达国家铝合金的搅拌摩擦焊技术已进入商业化阶段，而我国在该技术领域中的研究才刚刚起步。因而本课题针对铝合金这种重要的工业材料，采用自制的搅拌摩擦焊设备，进行了搅拌摩擦焊工艺的探索与研究，旨在为搅拌摩擦焊技术早一日在我国工业领域推广应用提供理论和实践依据。 搅拌焊头的结构设计是搅拌摩擦焊技术的核心，本课题采用圆柱形搅拌焊头，通过改变其肩部及焊针的尺寸，分析其对焊接过程及焊缝质量的影响。试验结果表明：对于厚度为3mm的铝合金板材，圆柱形搅拌焊头的最佳设计尺寸是：焊针直径为3mm，肩部直径为9mm。 合理的焊接线能量即单位长度焊缝的热输入量是保证焊接接头质量的重要因素。对于搅拌摩擦焊，其热量主要来自摩擦产热，而搅拌焊头的尺寸、旋转速度、焊接速度及压力决定了摩擦产热的大小，对焊缝质量起重要作用。研究结果表明：在其它参数一定的情况下，焊接线能量取决于搅拌焊头的旋转速度与焊接速度之比(n／v)。在本试验条件下，当n／v为15～23时，焊缝的质量较好。 焊接接头的金相分析结果表明：搅拌摩擦焊焊缝区晶粒比母材晶粒细小，焊缝组织致密，无裂纹和气孔等缺陷，热影响区比熔化焊时窄，因而，搅拌摩擦焊接头的综合性能良好。更多还原

【Abstract】 Friction stir welding (FSW) is a patented new solid joining process, which was invented at TWI ten years ago. Unlike more conventional fusion welding, the friction stir weld remains solid state during welding, so there is no welding defect such as cracking, porosity and loss of alloying elements etc. There is no requirement for filler wire or shielding gas during welding process. No joint preparation is required before welding. Energy for friction stir welding is lower than conventional fusion welding. There are no radiation hazards, weld fume, splash and high noise during welding process. So friction stir welding is a "green joining process" with excellent mechanical properties of joints, high efficient and lower costs and its application is widely.At present, in developed countries the friction stir welding process is already in commercial use, but it is just beginning in our country. The study on friction stir welding of aluminum alloys sheet was conducted with self-made equipment. The study will provide the bases of theory and practice for wide application of friction stir welding in our country.The design of welding head geometry is the key for friction stir welding. The friction stir welding using cylindrical stir-welding head was conducted, and the effect of welding head on welding process and welding quality by changing the diameter of the shoulder and welding pin was analyzed. The results of experiments show that the optimal size of cylindrical stir-welding head for 3 mm thick aluminum alloys plate is that the diameter of shoulder is 9 mm and the diameter of welding-pin is 3 mm.Proper heat input is important factors on welding quality. In friction stir welding process, the friction heat between welding head and work-pieces is the source of energy. Welding quality depends on the size of welding head, rotating speed, welding speed and pressure. The study results show that heat input depends on the ratio of rotating speed and welding speed(n/v) when other parameters are constant. In this experiment, good quality weld can be achieved when n/v is in the range of 15 ~ 23 .The microscopic examinations reveal that the grain size of FSW weld is fine andthe heat affected zone is narrow than that of fusion weld. So the mechanical properties of FSW joint are good.更多还原