Comprehensive evaluation of microstructure and property for 12 CrMo 910 main steam piping No1 of unit No4 having been operating 146967 hours in Niangziguan Power Plant has been carried out by using numerous methods

such as chemical component analysis

mechanical test under room temperature

carbide feature and its variation analysis

metallurgical and electronic microscope analysis

creepage damage observation

and persitent strength test etc.. Test results show that the microstructure state and mechanical property of said main steam piping are still perfect after having been operating 149967 hours

satisfying the German standard

can be continuously operating in safety.