Perforation Failure Causes of Superheat Pipe for Boiler Water Wall

Since the water wall of a generator set was put into use, the superheat pipe perforation failure accidents occurred many times. The perforation failure causes of superheat pipe were analyzed by means of macroscopic observation, chemical composition analysis, tensile property test, hardness test and metallographic examination. The results show that the failure superheat pipe was in the high temperature state above 450 ℃ for a long time, and the local wall temperature reached 600 ℃, which made the superheat pipe endured high temperature and oxidation corrosion for a long time. The pearlite structure of the superheat pipe was obviously spheroidized and partially completely spheroidized, and there were more free cementite along the grain boundary. The deterioration of the microstructure made the strength and mechanical properties of the superheat pipe decrease. The corroded and thinned superheat pipe expanded and deformed under the action of pressure in the pipe, which eventually led to the perforation failure of the superheat pipe.