Research On Welding Technology Of Wear-resistant Alloy Steel Turnout For Modern Tram

The modern tram began in Europe and America in 1880 s.After a series of ups and downs,At present,there is a broad prospect in our country.The welding turnout technology of high quality and wear-resistant steel is a key technology for modern tram turnout.Traditional switch uses high manganese steel frog,And the welding method is flash butt welding or aluminum heat welding.Well then,High manganese steel frog has good integr it y,convenient maintenance.However,its large weight and complex section make its casting and heat treatment performance lower,and there are many phenomena of shrinkage,loose and coarse grain.The frog in the process of using the majority did not wear to limit because of cracks,so that has to be replaced.Further more,the energy concentration of aluminum heat welding and flash butt welding line,And the high manganese steel is poor in weldabilit y.I n order to achieve seamless and welded rail frog,This project adopts welding together better welding performance of NM400 alloy steel frog and rail,The welding method is combined with carbon dioxide gas shielded welding and manual arc welding.First,the NM400 series preheating/tempering experiment is designed in this paper.The ragular of the mechanical properties of NM400 with the change of preheating / tempering temperature are studied.In order to optimize the preheating / tempering temperature of NM400.At the same time,the SHCCT curve of NM400 steel was plotted by the thermal simulation test of Gleeble welding.And the influence of different heat input on the heat affected zone performance of NM400 steel was studied.The microstructure and Brinell hardness were analyzed,and the impact toughness of coarse grain HAZ in heat affected zone was also analyzed.The best welding process is obtained.Meanwhile,the changes of microstructure and properties of NM400 steel during welding are revealed.Subsequently,the welding procedure qualification test of typical joints of modern tram cars was carried out,and the welding inspection was completed.Combined with the mechanical performance test results,the impact joints and the microstructure of typical joints were studied,which further explained the rules of the experiments.A major innovation of this paper is that SYSWELD welding finite element simulation software.It can help to simulate welding temperature field and stress field of the turnout.Then It was simulated and compared the different stress field under the rigid restraint model,so as to optimize the method of rigid restraint,As we can see,this guides the production of modern tram special welding fixture.