Mechanical Property And Deterioration Analysis Over Main Steam Piping Material

Generally, the design life of power plant is 30 years. The main steam pipe in power plant is working under high temperature and high pressure, which can lead to the increase of atomic diffusion, as well as the microstructure changed. Also, creep damage, creep voids, carbide spheroidization, aggregation, growth and grain boundary cracks may occur. From Baogang steel power plant put into operation in 1982 so far, the running time has reached the design life, so the unit needs to be important components of high temperature metal state assessment, to establish a reasonable solution strategy and life extension. The steels of Baogang thermal power plant main steam pipeline was STPA24, but the research about steel STPA24 is not enough in domestic, so this paper can enrich the instance of STPA24 research.In this paper, the development of the main steam pipe in power plant is discussed, and the method for analyzing the performance of the main steam pipe is also summarized. This paper is divided into two parts, analysis mechanical properties at normal temperature and the study of degradation mechanism for STPA24 of ruined 200,000 hours. Normal temperature mechanical properties tests include normal temperature hardness test, tensile test at room temperature, impact test and fracture morphology analysis indicated that the toughness of STPA24 steel after long running is serious and the embrittlement temperature increases greatly. The study on degradation mechanism including chemical components analysis, metallographic analysis, SEM and EDS analysis shown that chemical constituents have been no significantly changing. However carbide spheroidization reached level 3-4, and the pipeline hardness increased, as the gathering of carbide of Cr and Mo in the boundary, Tensile and impact toughness decreased obviously, but it is still in the normal range of safe operation, which need to pay attention to the role of impact load.Organization structure analysis and normal temperature mechanical properties testing of steel STAP24 can analysis the mechanism of long-term running main steam pipeline deterioration and get the degree, Which play an active role in power plant safety production.