The Hot Deformation Behavior And Crack Propagation Study Of Nuclear Power Carbon Manganese Steel

Seamless steel pipe is one of the important raw materials used for the construction ofnuclear power plants and the manufacture nuclear power equipments. The carbonmanganese steel is mainly used for pipelines of nuclear steam system and auxiliary system.Nuclear safety level as well as the material level in the RCC-M specification is generallynuclear grade2. For the steel pipe, not only the requirement of dimension accuracy andsurface quality is very high, but also it should have good hot strength, impact toughnessand FAC resistance performance. But at present, the research of the nuclear power steel isvery poor.This article has got the real stress-strain curves of P280GH nuclear power steel by thehot compression deformation experiments, and calculated the dynamic recrystallizationactivation energy, established mathematical models of deformation temperature, strain rateand peak strain, and established the constitutive equation of P280GH steel by theintroduction of the Zener-Hollomon parameter. At the same time, kinetics model ofdynamic recrystallization is established. Finally, the article has completed metallographicexperiment by taking thermal compressed sample and studied the impact law of the strainrate, deformation temperature to dynamic recrystallization. And thermal processing figurehas been constructed based on Dynamic material model and stress-strain curves, whichcan determine the best thermal processing range of P280GH steel and the parameter ofinstability defects which can provide proper technological parameters for hot rolling.Through the expansion method, metallographic experiment and hardness test,continuous cooling transformation curve (CCT curve) of P280GH steel has beendetermined and plotted. Further, Transformation products of different cooling rate and theirmicrostructure morphology have been studied. Combined with the TTT curve, the articlehas simulated the changes in microstructure of P280GH steel under different coolingconditions, by the DEFORM finite element software. And the different position of eachtissue percentage and the rule of temperature change have been researched which havecertain guiding significance to the actual heat treatment process. In the end, the article hasestablished the finite element model of crack propagation, and simulated the crack propagation laws of I and I-II mixed mode crack, by the ABAQUS finite element software.And the article has researched the effect of different fracture toughness to the crackpropagation and calculated stress intensity factor of the typical crack, which is importantpractical significance to improve the finished product rate and the comprehensiveperformance of the material.