目的 提高焊接接头的表面质量。方法 采用超声冲击方法对 16MnR 十字接头焊趾处进行冲击处理，对原始焊态及不同冲击工艺参数下的焊趾表面质量进行了对比测试及比较分析。结果 冲击后，焊接接头焊趾处过渡半径增大，母材与焊缝过渡趋于平缓。焊趾表面组织得到明显细化，细化层深度及细化程度随冲击工艺参数的变化而变化。冲击后焊趾处由焊态的拉应力状态转变为压应力状态，表面显微硬度大幅提高。在 1.5 A/20 min 冲击工艺下，焊趾处的残余压应力最大（为 269.8 MPa），表面显微硬度最高（为 340.5HV）。同时，经超声冲击后，表面粗糙度有增大的趋势，而且不当的冲击会使接头表层出现不同类型的缺陷，从而影响焊接接头整体的表面质量。结论 接头表面质量不仅取决于冲击时间、冲击电流，还取决于单道冲击过程中冲击点与冲击点之间及多道往复冲击过程中冲击道与冲击道之间的位置及连接的紧密程度，而且并不是所有表面质量指标都与超声冲击参数正相关或线性相关。

The work aims to improve surface quality of welded joints. Ultrasonic impact treatment (UIT) was applied to weld toes of 16 MnR cross joint, and comparison test and comparative analysis were applied to surface quality of weld toes as-welded and treated under different UIT parameters. After UIT, transition radius at weld toes of welded joint increased, and transition from base metal to weld became smooth. Surface microstructure of weld toes was significantly refined, and refined depth and refining degree varied with UIT parameters. Tensile stress state of the weld toe as-welded transformed compressive stress state, surface microhardness increased greatly after UIT. The compressive stress was the maximum (269.8 MPa) and surface microhardness was also the maximum (340.5HV) under the effect of 1.5 A/20 min UIT. Meanwhile, surface roughness tended to increase after UIT, and improper UIT would lead to different kinds of defects on the surface of welded joint, thus affecting overall surface quality of welded joint. Surface quality of joint depends on not only impact time and impact current, but also location among impact points during single-channel impact and impact channels during multi-channel reciprocating impact as well as tightness of connection. Not all surface quality indicators are positively related to or linearly dependent on ultrasonic impact parameters.