Abstract: The spindle crank of a reducer fractured when it was assembled with the spindle for secondary service, and the fractured crank was analyzed by means of chemical compositions analysis, macroscopic observation, metallographic examination, mechanical properties test and scanning electron microscope (SEM) analysis. The results show that the fracture originated form inner subsurface of the crank, and there were two layers of hardfacing layer between the matrix and the inner subsurface. The fracture of the crank was mainly caused by the inner side repair welding and the improper repair welding technology. At the same time, the bad processing technic and the unqualified chemical compositions, mechanical properties and microstructure also accelerated the fracture.