Research on Welding Repair for Tee Joint Crack of Final Superheater Header of 300MW Station Boiler
Through methods, such as microscope analysis, metallographic examination, the crack located nearby the fusion line between tee joint and outlet steam pipe of subcritical power station boiler final superheater header is reheat crack (the main crack occurred in the heat affected zone and extended along the fusion line and grain boundary in HAZ. There are many small cracks paralleling with main crack). The base metal material (12Cr1MoV) and excessive welding residual stress are the primary inducement of crack. In repair crack, the measures of reducing residual stress, such as lower welding heat input, reducing thickness of welding layer, hammer blowing, assigning reasonably heat treatment power ,lengthening holding time and so on, were taken. The welding repair succeeded greatly.
X. G. Niu et al., "Research on Welding Repair for Tee Joint Crack of Final Superheater Header of 300MW Station Boiler", Applied Mechanics and Materials, Vol. 235, pp. 96-100, 2012