Abstract: After making life test for a product, and taking it apart, a fractured expansion ring was found. By means of fracture analysis, metallographic examination, hardness testing and so on, the fracture reason was analyzed. The results showed that the major reason for fracture of expansion ring was the raw material inclusion with more, especially the inclusion zone of subsurface reducing material’s plasticity and strength. In addition, repeated stress during the progress of life test, making the expansion ring broke finally. In order to avoid similar events, it can take strict control for the raw material inclusion.