High Permeability Rolling Process And Homogenization Control Of SA738 Gr.B Extra-Thick Steel Plates For Nuclear Reactor Containment

SA738 Gr.B wide and thick steel plate is the main material of the third generation nuclear reactor type AP1000 nuclear reactor containment.The thickness of the steel plate is large.Due to the complex working conditions encountered during the service of the steel plate and the steel plate withstands various loads,it is required that the steel plate has a good strength and toughness,meanwhile,the material has much higher requirements on the uniformity of structure and performance than other materials.With the development of large-scale nuclear power plants,the containment of nuclear reactors has also increased and thickened.The equipment inlets and air locks on containments must use 100mm thick extra-thick plates.As the thickness increases,the low temperature toughness index of nuclear power steel gradually increased.At the same time,due to the limitations of continuous casting and rolling conditions,SA738 Gr.B extra-thick plates generally suffer from insufficient core deformation,leading to coarse structures,insufficient low-temperature toughness,and poor uniformity of thick-section microstructure properties.In order to solve these problems,this article relies on the national"Thirteenth Five-Year Plan" key research and development project "New generation of pressurized water reactor nuclear island steel and hydrogen chemical large single heavy plate"(2017YFB0305300),SA738 Gr.B for nuclear reactor containment Ultra-thick steel plate is the research object.The method of numerical simulation and laboratory hot-rolling verification is used to study the plastic deformation behavior of metal and its influence on deformation permeability during high-infiltration rolling process.In this paper,the material model of experimental steel SA738 Gr.B was established by experimental methods;the microstructure of the experimental steel was observed and analyzed by metallographic microscope,scanning electron microscope,and electron probe;The austenite grain boundary was corroded by saturated picric acid solution;the mechanical properties of the experimental steel are tested by tensile and pendulum impact experiments;and the material impact fracture is analyzed by scanning electron microscopy;The influence of high permeability rolling process on the thickness microstructure and strength and toughness of experimental steel was studied.The main research work of this paper includes:(1)The effects of different cooling and rolling parameters on the thickness temperature field,transverse metal flow,and internal equivalent stress and strain of SA738 Gr.B extra-thick steel plate under high-infiltration rolling process were studied through single-pass numerical simulation experiments.At the same time,based on the orthogonal experiment,the influence of each influencing factor on the equivalent strain of the steel plate core was studied by simulation,and they were sorted according to importance;(2)The method of combining numerical simulation with three times of laboratory hot rolling was used to study the influence of high penetration rolling process on the macro deformation of SA738 Gr.B extra thick plate.The results show that the high-infiltration rolling process can increase the degree of metal deformation in the core of SA738 Gr.B extra-thick plate,and at the same time can make the metal flow in each layer more uniform.In order to obtain the same deformation effect,the reduction rate required for the high-infiltration rolling process smaller;(3)Using a combination of multi-pass numerical simulation and laboratory hot-rolling experiment verification,systematic research and obtained the influence of rolling process strategy on thickness deformation permeability of SA738 Gr.B extra-thick plate with different cooling gradients during thick rolling and high penetration during cooling at different phases;(4)A high-permeability controlled rolling experiment under industrial conditions was performed,and the effects of conventional rolling and high-permeability rolling processes on the microstructure and strength and toughness of SA73 8 Gr.B extra-thick steel plates at different locations were compared and analyzed.The results show that The high-permeability rolling process can not only significantly improve the quality of the 1/4 place and the core,improve the low-temperature impact toughness of the core of the steel plate and the uniformity of the cross-section structure performance,at the same time can avoid the formation of side double drums,reduce the amount of steel plate cutting,and accelerate rolling control the rhythm and improve production efficiency.Completed the industrial trial production of the ultra-wide 4600mm and ultra-thick 100mm SA738 Gr.B steel plates for nuclear reactor containment,and achieved good industrial application results.