Reasons for cracking of boiler heat exchange tubes

Cracks appeared in a certain boiler heat exchange tube during assembly, located at the weld joint position of the tube plate welding joint. The reasons for the cracking of the heat exchange tube were analyzed by macroscopic observation, chemical composition analysis, metallographic examination, hardness testing, scanning electron microscopy analysis. The results show that there were welding defects such as incomplete penetration, incomplete fusion, and cracks in the weld seam of the heat exchange tube. The heat affected zone of the weld seam showed hardened martensite, which eventually led to cracking of the heat exchange tube with increasing assembly stress.