Long-term Use Of Cr-mo Steel Tube Of Organizational Performance And Remaining Life

Study on the structures, performance and residual life of Cr-Mo steel is of considerable industrial importance. Vary accidents happen to CrSMo heat-resistant steel furnace tubes, which are widely applied in our petrochemical field, but we haven't had a comprehensive and systematic investigation about the problems. The designed life of common equipments running under the high temperature is 100,000 hours. The CrSMo furnace tube in our country have or will run out of time. Presently, the running situation, the possible damage of kept running and the residual life of the heating furnace tube are concerned by the factories. The structure, performance and creep residual life of reformer furnace tubes which have run for 10 years in Karamay Complex have been investigated using many equipments such as OM, XRD,SEM/EXD and EPMA. A reasonable and practical residual life evaluation method is found by the experiments to keep the furnace tubes running as before.The experimental results show that the microstructures of CrSMofurnace tubes have been changed after a ten-year running. The changes include spherical pearlites, changes of shapes, quantity and distribution of carbides. There are no cavities and cracks. The inner and outer surface of the furnace tubes are oxides. The maximum thickness of the oxide scale layer is about 0.12mm.With the high temperature, the time will influence the strength of the materials. High temperature strength testing of the materials is a direct and reliable way to determine the mechanical performance of the high-temperature materials, 24 specimens of reformer 101,3 01 furnace tubes are used to test high-temperature persistent performance. The creep rupture test results show that although the strength of these two tubes are decreased in some sense, the residual life is more than 100,000 hours if kept running in service condition. Meanwhile, according to the microstructure, performance and residual life of CrSMo furnace tubes, the relationship of the structures and high-temperature persistent performance is established to estimate the residual life in terms of the changes of the microstructures during the industrial production.