高速列车转向架用耐寒焊丝研制及接头组织性能

Development of cold-resistant solid wire and microstructure of high speed train bogies

在我国东北以及俄罗斯等极寒地区要确保高速列车的安全可靠运行,高速列车转向架焊接接头必须具备广域环境条件下的服役能力,因此开发耐寒高韧性转向架焊丝至关重要。采用微合金化设计,研制了一种新型耐寒高韧性焊丝55GⅡ。利用高速摄相系统观察熔滴过渡行为,测试熔敷金属力学性能,利用扫描电镜观察冲击断口形貌,研究焊缝金属耐腐蚀性能和疲劳极限。结果表明:55GⅡ焊丝在250 A和150 A电流条件下具有优异的电弧稳定性,短路或爆断次数少、飞溅颗粒小;其焊缝组织主要为贝氏体、珠光体及铁素体的混合组织,-40℃平均冲击功达到129 J,-60℃平均冲击功达96 J以上;1 000 h周浸腐蚀失重比3.56%;在4应力级条件下经1×107次循环,焊接接头疲劳极限为374 MPa。

To ensure the safe and reliable operation of high-speed trains,the welded joints of bogies must have the ability to serve in wide area,such as the extremely eold regions of Northeast China and Russia. Therefore,it is increasingly important to develop the welding material for bogie with cold resistant and high toughness. In this paper,a new type of 55G Ⅱ solid wire with high cold resistant and toughness was developed by using microalloying design. The transition behavior of droplets was observed by using high speed phase system. The mechanical properties of weld metal were tested and the fracture morphology of tbe specimens were observed by scanning electron microscope （SEM）. Besides,the corrosion resistance and fatigue limit of the weld metal were studied. The results showed that, the newly developed solid wire has excellent arc stability under 250 A and 150 A current conditions,such as short circuiting or breaking times and small spatter particles. The mierostructure of the weld metal is mainly composed of bainite,pearlite and ferrite. The maximum impact energy at -40℃ is 129 J while the average one is 96 J at -60℃. The weight loss of 1 000 h alternate immersion corrosion is 3.56% and the fatigue limit of the welded joint is 374 MPa through 1×10^7 cycles under the 4 stress level.