Failure analysis of bainitic steel pipe - Failed during cold working process

Cracked thin wall steel pipe was received for failure analysis. The samples of the cracked pipe, un-cracked pipe and starting material were subjected to different experiments. In this regard, optical and electron microscopes, universal testing machine and hardness tester were utilized for characterization. A series of heat treatment made on starting material to obtain the similar mechanical properties and microstructure as that of cracked pipe. The surface of the opened cracks were observed in scanning electron microscope and revealed high concentration of non-metallic inclusions. Finite element model was utilized for the confirmation of different stress conditions during the fabrication process.