Fracture Reason Analysis on Tubes of a Boiler Heat Exchanger

Instruments such as optical microscope, scanning electronic microscope, energy spectrometer, tensile testing machine and direct reading spectro meter were used to analyze the fracture reason of tubes of a boiler heat exchanger which fractured after being put into operation only for 2 h. The results show that there were original cracks and mechanical damage on the surface of the tubes before their running. Stress concentration formed at the defect positions and lower service temperature together resulted in the early brittle fracture of the heat exchange tubes after 2 h operation. Some suggestion for producing the heat exchange tubes was proposed finally.