The Influence Of Neutron Irradiation Simulation On The Mechanical Properties And Magnetic Properties Of Reactor Pressure Vessel Steel

The magnetic nondestructive testing(NDT)of mechanical properties of reactor pressure vessel(RPV)is benifial to the assement of RPV’s neutron irradiation damages.Since neutron irradiation is difficult to obtain and the samples are radioactivity after neutron irradiation,simulation experiments are always adopted in the studies of neutron irradiation damages.In this paper,to simulate the matrix damages and Cu-rich clusters caused by neutron irradiation,RPV steel is cold rolled or fast cooled from 700 ℃ to produce the martrix damages,and the Cu-rich RPV steel is thermal aged to produce the Cu-rich clusters.Mechanical properties and magnetic properties of simulation experiments are studied.Then the correlations between mechanical properties and magnetic properties are discussed on the basis of the microstructures so as to study the feasibility of magnetic NDT of mechanical properties of RPV steel.The tampered Cu-rich RPV steel is thermal aged at 370 ℃ and 440 ℃.It is found that there produces Cu-rich clusters at the end of thermal aging.The hardness and coercivity both exhibit aging peaks during thermal aging,moreover,the variations of hardness and coercivity of the aging peaks at the two temperature are fairly close.Besides,it is found that there is a good proportional correlation between △HV and △Hc,and the fitting slopes of △HV-△Hc at 370 ℃ and 440 ℃are fairly close.The normalized Cu-rich RPV steel is thermal aged at 440 ℃.During the thermal aging,neither visible Cu-rich clusters is found,nor mechanical properties and magnetic properties does change.Cold working introduces dislocations into RPV steel.As the deformation increase,the hardness and strength both increase.The remanence drops suddenly after 0.75%deformation,then it decreases slightly as the deformation increase.The coercivity exhibits two-stage growth.For the samples of 0～4.13%deformation,the coercivity increases fast as the deformation increases.While for the samples of 5.8%～40.3%deformation,the coercivity increases slowly as the deformation increases.Besides,it is found that there is a good two-stage linear correlation of △HV-AHc and △σs-△Hc,which fitting slopes are larger at lower deformation and smaller at higher deformation.After heated at 700 ℃ and fast cooled,a large mumber of dislocation networks and stress waves appear in RPV steel.After fast cooling,the hardness and yield strength both increase and the impact energy at room tmeperature drops remarkably.Moreover,the remanence dorps remarkably and the coercivity increases remarkably after fast cooling.Overall,the matrix damages and Cu-rich clusters introduced by simulation experiments could alter the mechanical properties as well as the magnetic propertis of RPV steel,and there exists correlations among the yield strength,Vicker hardness and coercivity.Moreover,it is found that the fitting slopes of△HV-△Hc and △σs-△Hc are biggest in the less deformed RPV steel,medium in the thermal aged tempered Cu-rich RPV steel,and smallest in the highly deformed RPV steel.