A flange fracture occurred during the installation of a traction transformer oil pump. The causes of the flange fracture were analyzed using physical, chemical, and finite element methods. The fracture surface shows expanded edges and a linear fracture source, indicating an overload fracture. No significant defects such as pinholes, looseness, or cracks were found in the internal structure, which contains elongated Si phases. The Si, Ti, and Zn content in the failure part does not meet standard specifications. The hardness of the failure part is HBW107.8, meeting standards, but the elongation at break is at the lower limit, suggesting higher material brittleness. Finite element analysis revealed a maximum tensile stress of 241.5 MPa on the flange, close to the yield strength, indicating a small safety margin. The flange fracture is related to high material brittleness and potential assembly anomalies. To prevent similar incidents, strict control of raw material quality, regular inspection of mechanical properties, and finite element analysis for structural optimization are necessary.
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