低合金高强钢螺纹孔摩擦塞补焊修复接头的组织与性能研究

Microstructure and Mechanical Properties of Friction Plug Repair Welding Joint on Low Alloy High Strength Steel Threaded Hole

针对轨道车辆零件螺纹孔摩擦塞补焊修复工艺及性能进行了研究。在优化的塞孔/塞棒几何参数和焊接工艺参数下制备了无缺陷的焊接接头,并分析焊接接头的微观组织、拉伸性能、冲击韧性和疲劳性能。结果显示,当轴向压力过大,接头界面处会形成未焊合缺陷。在转速为7 000 r/min、轴向压力35 kN、顶锻压力40 kN、塞棒进给量18 mm的参数下,可以获得成形良好的无缺陷接头。靠近结合界面的微观组织主要为珠光体、铁素体和部分板条状贝氏体。焊缝中的微观组织为针状铁素体和大量晶界铁素体,以及少量的板条状贝氏体。焊接接头具有优良的力学性能,其拉伸性能与母材相当,室温拉伸试验中,接头断裂位置均位于母材;疲劳实验中,螺栓外螺纹总是先于修复螺纹孔内螺纹发生疲劳断裂,修补螺纹的500万次疲劳强度达到142 MPa。

In this paper,the friction plug repair welding process and mechanical properties for the threaded hole on rail vehicle part were studied.The defect-free repair welding joints with optimized geometries of the plug/hole and welding parameters were obtained,and their microstructure,tensile properties,impact toughness and fatigue properties were analyzed.The results showed that incomplete penetration occurred in the bonding interface at high axial force.The defect-free joints were obtained with a rotation speed of 7000 r/min,axial force 35 kN,thrust force 40 kN,and the plug feeding 18 mm.The microstructure near the bonding interface consists of pearlite,ferrite and some lath bainite,at the nugget zone is acicular ferrite,a large amount of grain boundary ferrite and a small amount of lath bainite.The defect-free joint has excellent mechanical properties,the tensile properties are equivalent to that of base metal,the fracture position of the joints are all located in the base metal at room temperature tensile test.In the fatigue test,the external thread of bolt always cracked precedes that of the internal thread of repair thread hole,The five million cycles fatigue strength of repair thread by plug welding reaches 142 MPa.