| P280GH carbon manganese steel is mainly used in seamless steel pipe of production for pressurized water reactor. It is RCC-M specification high temperature characteristics of carbon steel and has a good comprehensive mechanical properties.The steel is widely used for steam system and auxiliary system in nuclear power plant. But with the increase of service time, the performance of P280 GH steel will be gradually deteriorated and appear aging. That seriously affects the safe operation of nuclear power plants. Therefore, it has great practical significance to study the aging mechanism and fatigue life of P280 GH steel for nuclear power plant.In this paper, the P280 GH steel is accelerated aging in 400 degrees Celsius and the time was 0h(original), 300 h, 3000 h, 5000 h,10000h. Then, P280 GH steel was studied by optical microscope, transmission test, scanning electron microscope, hardness test, tensile test and impact test. The microstructure and mechanical properties of the steel during aging were systematically analyzed.The P280 GH steel has irregular ferrite phase and strip or lace pearlite phase by microscopic observation.With the extension of aging time, metallographic observation found that the organization change is not obvious. But the pearlite has happened spheroidizing and the precipitates are found in the ferrite phase and phase boundary by transmission electron microscope.And the dislocation density becomes smaller.By the related experiment, the hardness, impact toughness, tensile strength and yield strength of the P280 GH steel has dropped. The P280 GH steel shows the characteristics of aging(weakening). The microstructure of tensile and impact fracture was ductile and the plasticity was slightly increased. Second phase particles appear at the bottom of the tough nest.Based on the material parameters obtained by experiment, the P280 GH steel tube model was established by using ABAQUS. And the stress changes of the whole tube and the defect(stomatal) under different internal pressure were studied. And The fatigue life is calculated by the fatigue analysis software. The fatigue life of the Integrity tube and different defects tubes were calculated respectively.That provides a theoretical basis for the safety service cycle of P280 GH steel tube. |
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