Failure Analysis on Fracture of Mandrel Used in Production of Seamless Steel Tube

The mandrel used in the production of a seamless steel tube fractured frequently at tail in use process. The causes of the fracture were analyzed by means of macro examination, chemical composition analysis, metallographic examination and mechanical property test. The results show that the fatigue bending caused by the abnormal stress at the mandrel tail was the external factor led to the fracture of the mandrel tail. The unreasonable structure of the mandrel caused the greater bending moment and stress concentration at the junction of the transition cone and the tailstock when the tail was stressed, and the severe banded segregation, low energy absorbed by lateral impact, poor toughness at the fracture of mandrel were the internal factors led to the fracture of the mandrel.