6061铝合金双轴肩搅拌摩擦焊接扭矩特征

Torque feature in bobbin tool FSW of 6061 aluminum alloy

为了揭示6061铝合金BTFSW过程中焊接扭矩的特征,对扭矩进行了检测,分析了扭矩信号的频谱特征、扭矩峰值的变化特点、扭矩振荡与焊缝表面成形的关系.研究表明扭矩具有周期性,主要频率接近于2倍主轴旋转频率值,频差的存在说明了焊接区域存在搅拌头与不同速率的金属流之间挤压摩擦的叠加行为;当接触点温度小于500℃时,扭矩峰值随着焊接速度的提高而变大,随着旋转速度的提高而变小;正常较小的扭矩振荡不影响表面成形,但当接触点温度大于550℃、上下轴肩间距过小或焊接速度过小或旋转速度过大等时,扭矩易发生异常振荡.对进一步揭示深入研究BTFSW焊接机理、搅拌头三维受力特征及其与焊接参数、焊接质量的关系有着重要的推动意义.

To investigate the torque characteristics in bobbin tool friction stir welding( BTFSW) of 6061 aluminum alloy,the torque in BTFSW was measured,the frequency spectrum and the peak of torque were analyzed,and then the relationship between the torque oscillation and the surface shape of welded joint was also discussed. The research indicates that the torque in BTFSW is periodic. The major frequency of the torque is close to2 times of the spindle frequency. The frequency difference illustrates that the stacking behavior exists between the tool and the metal flow at different velocity. The experimental results indicated that the peak of torque increases with welding speed being increased and decreases with rotation speed being increased when interface temperature of tool and workpiece was lower than 500℃. Smaller torque oscillation will not affect the surface shape of welded joint,but if the interface temperature was higher than 550℃,the torque will appear abnormal oscillation under adverse condition,such as the too short distance between top and back shoulders,slow travel speed,high rotation speed. This research will be useful to indicate the mechanism of BTFSW,3-D force characteristics and the relationship between welding parameters and welding quality.