Analysis on Cracking of a L360M Pipeline Steel Pipe during Hydraulic Burst Test

The causes of longitudinal cracking and transversal fracture of a L360M longitudinal submerged arc welding steel pipe during hydraulic burst test were analyzed by macro and micro fracture analysis,chemical composition analysis, mechanical property test, metallographic analysis and other test methods. The results show that the longitudinal cracking and transversal fracture of the steel pipe were mainly caused by the poor toughness of the pipe material which was related to the serious ferrite-pearlite banded structure, and the segregation of element manganese was the main reason for the serious banded structure. Measures such as controlling the element manganese content reasonably, reducing the final rolling temperature, increasing control cooling rate and micro alloying were suggested to reduce the banded structure grade of the steel plate used for making the pipe.