Abstract:  In order to solve the problems of welding failures caused by the traditional stirring head which easily fell into the welded plates under the conditions of non rigid support， the stationary shoulder welding structure was designed and developed. By establishing the finite element simulation model and using the thermal infrared imager to monitor the welding surface temperature in real time， the changes of temperature fields during stationary shoulder friction stir welding under different processing parameters were analyzed. The stationary shoulder friction stir welding designed and developed were used for field tests， and the tensile tests were carried out to compare the welds without defects on the welded surfaces with the base metal， the mechanical strength of the welds was detected， and the microstructure of the fracture was analyzed. The results show that in the welding processes of stirring head with stationary shoulder， the heat generation mainly comes from the friction heat generated by the shoulder and the end of the stirring needle， and the side friction heat generated by the stirring needle and the friction heat generated by the stationary shoulder account for a small proportion. The spindle pressure and spindle speed have great influences on heat production， and the C-axis speed has little influences on heat production. Under the processing parameters of spindle pressure of 2940～3430 N， spindle speed of 1000 r/min and C-axis speed of 0.05 r/min， the surface of the welded seams is smooth without flash， there are no groove and tunnel defects inside， the tensile property of the welds reaches about 71.5% of the base metal. There is delamination in the weld fracture. The upper layer near the welding surface shows brittle fracture characteristics， and the lower layer shows ductile fracture characteristics. Compared with the base metals， the elongation and tensile strength of the weld specimens are reduced. 

Key words: stationary shoulder, friction stir welding, processing parameter, temperature field, experimental research

摘要： 为了解决非刚性支撑条件下传统搅拌头易陷入被焊接板材而导致焊接失败的问题，设计研发了静轴肩焊接结构。通过建立有限元仿真计算模型，并使用热红外成像仪对焊接表面温度进行实时监测，分析不同工艺参数下静轴肩摩擦搅拌焊焊接过程中的温度场变化情况。使用设计研发的静轴肩摩擦搅拌焊进行现场试验并对完成焊接表面无缺陷的焊缝与母材进行拉伸试验对比，检测其焊缝机械强度，并对断口进行微观组织分析。结果表明：在使用静轴肩搅拌头焊接过程中，产热量主要来源于搅拌针轴肩的摩擦生热和搅拌针端部的摩擦生热，搅拌针的侧面摩擦生热和静轴肩的摩擦生热占比较小；对产热量影响较大的是主轴压力和主轴转速，C轴转速对产热量影响不大；在主轴压力为2940～3430 N，主轴转速为1000 r/min，C轴转速为0.05 r/min的工艺参数下，完成焊接的焊缝表面光滑无飞边，内部无沟槽隧道缺陷，焊缝抗拉性能达到母材的71.5%左右；焊缝断口存在分层现象，靠近焊接表面的上层呈脆性断裂特性，下层呈延性断裂特性，与母材相比，焊缝试样的延伸率和抗拉强度均有所降低。

关键词: 静轴肩, 摩擦搅拌焊, 工艺参数, 温度场, 试验研究