The Research Of Underframe Weiding For SDA₂ Diesel Locomotive

The underframe plays an important role in the supporting of the diesel locomotives,which is made by welding of steel structures.Due to the particularity of the welding process,quality of welding will directly affect moving safety of the locomotives,therefore,the research on welding reliability of the underframe has an important significance for locomotive moving safety.In this paper,by using of the FCAW welding method,two groups of Q420E-12 mm plate butt welding test specimens were welded respectively under the predetermined conditions of two experiential welding parameters.Then with the aid of the finite element analysis software SYSWELD,from the temperature field,stress field,strain field and deformation of multiple aspects,the differences of results of characteristic point temperature curve,differences of equivalent residual stress and those of equivalent plastic strain were analyzed and compared under the two welding parameters.After that,a welding parameter of the specimens was selected as the better one.Then the rationality of the selected parameters is verified again from the Q420E-12 mm plate butt welding series tests(macroscopic metallography,macroscopic hardness test,low temperature impact test,fracture test),this parameter can be used to guide the welding operation of the underframe.Finally according to the fatigue test standard GB/T 3075-2008,respectively researched the parent metal and weld fatigue test,the paper concludes that the fatigue limit of the parent metal and welding line is 155 MPa and 110 MPa respectively,from the metallographic results contrast,found in the process of the fatigue test fracture location in the parent metal and HAZ,blowhole and slag defects in the weld is the fatigue source,fatigue performance will decline.It suggested to further control the composition of the basic material and the uniformity of microstructure,in order to improve weld quality.