Study On Microstructure And Properties Of Q345E And14NiCrMo106V Welded Joints

The drawbar is a connection device for railway vehicle body and bogie frame, It is notonly carrying devices but also activities joint. Drawbar and traction connected together bywelding, the welding drawbar and traction seat is between the connection of dissimilarmaterials of different intensity level, the quality of welded joints and joint performancedirectly affects the security and reliable operation of the vehicle. Therefore, selecting suitableframe materials and processes to improve welding quality for the safe operation will be ofimportant velocity carriage.In this paper, ER50-6solid wire and E551T1-Ni2flux cored wire was used to weldQ345E low-alloy steel and14NiCrMo106V low-alloy steel, then the mechanical propertiesand microstructure analysis of the corresponding joint were studied through tensile, bend,impact and hardness examination as well as the fatigue tests, and provide the basis for theactual production of the locomotive drawbar.The results showed that: under the technological conditions in this testing, both themicrostructures in the welded metal contains blocky proeutectoid ferrite, a small amount ofcarbon-free bainite which stretch from grain boundary into the grain, and acicular ferrite,pearlite and granular bainite within the grain. However, in the welded metal of ER50-6solidwire, there are more vast proeutectoid ferrite and some inequality widmanstaten structure. Thefusion zone of the side of Q345E low-alloy steel consists mainly of are the massive firsteutectoid ferrite, strips of ferrite distribution, a small amount of blocky pearlite and granularbainite mixed organizations; While14NiCrMo106V low-alloy steel side of the fusion zone ofmixed ferrite, lath martensite and granular bainite. Microstructure of Q345E low-alloy steelbase material is a long iron of ferrite and pearlite distribution;14NiCrMo106V low-alloysteel base material is tempering martensite, in which have a few small distribution ferrite,troostite and granular bainite.Whether ER50-6solid wire or E551T1-Ni2flux cored wire welded jionts are broken inthe base metal of Q345E low-alloy steel, its welded joint tensile properties. The welded jointsbending performance excellent, bending and back bending can obtain the bending angle of180°. Impact test at room temperature, weld impact energy is higher with E551T1-Ni2fluxcored wire, two welded joint heat affected zone is almost the same impact energy.The hardness test shows that hardness of E551T1-Ni2flux cored wire is higher20~50HVthan ER50-6solid wire, while the HAZ are quite.When welding by using ER50-6solid welding wire, condition fatigue value of butt jointsis197.5MPa, which life period assigned as2×106circulations and the degree of confidence is50%, as well as condition fatigue value of T-type welded joints is202.75MPa when Q345E bottom. The fatigue limit with E551T1-Ni2flux cored wire is lower than ER50-6solid wire12.5MPa and39MPa respectively. From the fatigue view, ER50-6solid welding wire shouldbe used for welding Q345E low-alloy steel and14NiCrMo106V low-alloy steel.