Causes of engine bracket fracture and improvement measures

The fracture phenomenon of an engine bracket was analyzed by macroscopic observation, scanning electron microscope analysis, chemical composition analysis, metallographic examination and other methods. The results show that the content of C and Si elements in the material was close to the lower limit of the technical requirements, and the wall thickness of the casting was thin, so that the matrix graphite of the casting was E－type, which did not meet the technical requirements of the product, resulting in the fracture of the engine bracket under alternating load. It was recommended to add silicon carbide to the material to increase the content of C and Si elements. After the test, the graphite morphology of the casting was A－type, the length grade was 4, and the matrix structure was pearlite. The rest of the performance indicators met the design requirements.