Causes of cracking of 12Cr1MoV steel superheater tube

The 12Cr1MoV steel superheater tube in service of a company cracked in a short time. The fracture reasons were analyzed by means of macroscopic observation, chemical composition analysis, hardness test, hydrogen content analysis, scanning electron microscope analysis and metallographic examination. The results show that the defects were located on the inner wall of the steel tube after perforation rolling due to the original loose defects inside the tube blank. During the service process, the excessive hydrogen molecules in the boiler gas diffused into the pipe wall and enriched at the internal defects. There was a large residual stress in the elbow section of the heat pipe, which caused hydrogen－induced stress corrosion cracking at the defects, and finally led to superheater tube cracking.