Abstract: Hinge beam ears were fractured in the process of use. The fracture reasons for the hinge beam ears were analyzed by macroscopic analysis, chemical composition analysis, mechanical property test, metallographic examination and fracture SEM analysis. The results show that the residual aluminmm content and nitrogen content in the hinge beam were high, and the cooling rate was too slow in the summer, which made the grain boundary embrittlement due to the precipitation of AlN inclusions on the austenite grain boundary. At the same time, a large number of as-cast MnS and Al₂O₃ inclusions on grain boundary also aggravate the grain boundary embrittlement, and the intergranular brittle fracture of the hinge beam occurred in the process of use.