Through the macroscopic examination

metallographic examination

tensile test

the causes of the T23 tube burst of final superheater of a power plant are analyzed. The analysis results show that the burst of the tube is characterized by long overheating and material compliance with the standard requirements

but the metallurgical structure is seriously aging. The tensile strength of the tube section near the burst is obviously lower than that of the ASME standard. To sum up

the final superheater tube is running over temperature for a long time

resulting in its accelerated creep speed

dilated tube diameter and aging

resulting in creep holes

creep microcracks

and gradual expansion of micro cracks

leading to fracture of the whole tube.