Research On The Pefrormance Of Domestic Base Metal For Welded Frame Of High-speed Train Bogie

Now the development of high-speed railway as a strategic emergingindustry has a high priority. Manufacture of the welded frame of high speedtrain bogie is a key technology of high-speed railway. The S355J2W weatheringsteel used for welded frame of CRH3were entirely dependent on imports. Weneed find out one kind of weathering steel with a nice weldability produced bythe steel company in our country, which can be compared with the steelproduced abroad on the performance of strength, toughness and corrosionresistance. This is very important for the cost-cutting and localization ofhigh-speed railway equipment manufacture technology in a high degree if wefind out this steel and choose a suitable welding material as well as weldingparameters to weld.According to the research about the weathering steel at home and abroadand the need during production, we selected the S355J2W steel and the09CuPCrNi-A steel by Baosteel Group Corporation as the weathering steelmaterial used to manufacture the welded frame of train bogie. In the method ofside welding molding, the S355J2W steel and weathering steel of09CuPCrNi-Awere welded with welding robot by metal active-gas are welding（MAG） usingdomestic welding wire of H08MnSiCuCrNiⅡ. Shielding gas was80%Ar and20%CO₂mixed gas. Tensile, bend, hardness and metallographic tests werecarried on the welded joints we got to study the mechanical properties andmicrostructures of those joints.The results show that those joints of two kinds of steel have wellmechanical property. The tensile strength of welded joints was better than basematerial as specimens all broke in the area far away from the welded seam, obvious plastic deformation appear on the specimens before the break happened.We did not find cracks show on the specimens during bend test and this meansthat the joints have well plasticity. The distribution of hardness just likes theshape of saddle. Tensile specimen fracture were observed by scanning electronmicroscopy and found that there are large number of dimples in the center andedge of fracture by the S355J2W steel for ductile fracture.09CuPCrNi-A steelcracks in the center of the specimen, the cleavage fracture exist around thecracks and a little far we can find a large number of dimples and small part ofthe quasi-cleavage, a large number of dimples exist in the fracture edge forductile fracture. Line scan revealed the existence of the segregation ofphosphorus and sulfur on the steel plate center, resulting in the cracking ofwelded joints tensile fracture from the middle. The favorable mechanicalproperty of domestic welding wire and base material can meet the requirementsof localization. The segregation of phosphorus exits in the middle part of09CuPCrNi-A steel plate causes that the specimens break from the middle first.The joints of two kinds of weathering steel have similar microstructure.The weld microstructure of S355J2W steel consists of lath and granularpro-eutectoid ferrite with a little pearlite and granular bainite in the grain whileacicular ferrite appears along the grain boundaries. A certain amount ofwidmanstatten structure appears in the surface of welding seam. There are moregranular ferrite and pearlite at the bottom of welding seam as well as fine grainsize because of heat treatment by the next weld pass. The weld microstructureof09CuPCrNi-A steel consists of lath and granular pro-eutectoid ferrite as wellas a little pearlite and granular bainite in the grain, but there are more acicularferrite in the surface and middle of welding seam than the S355J2W steel.