A Study On Processing,Microstructures And Mechanical Properities Of 13MnNiMoR Pressure Vessel Steel Plate

13MnNiMoR is weldable fine-grained vessel steel used at medium temperature and medium pressure.It has excellent comprehensive mechanical properties and is widely used in manufacturing high pressure boiler steam bag,nuclear energy containers and other pressurized vessels and pipelines.In this paper,the chemical composition optimization,production process,microstructure and mechanical properties of heavy gauge 13MnNiMoR steel plate were theoretically analysed and experimentally stuided.And the prototype steel plate was obtained in laboratory which can meet the requirement of national standard GB713-2014.The main contents and results obtained in this thesis are summarized as follows:(1)With the JMatPro software,the precipitated phases in 13MnNiMoR steel were calculated.The effects of key element contents on the precipitation behavior were discussed.Based on the simulation results of the steel plate performance by JMatPro software,an optimal chemical composition(wt%)of the experimental steel has been designed as 0.12%C0.30%Si-1.38%Mn-0.28%Cr-0.80%Ni-0.37%Mo-0.018%Nb.(2)The static CCT curves of the steel and the SH-CCT curves of the heat affected zone were measured and depicted by using thermal expansion and metallographical methods with Formaster-FII dilatometer.The influence of cooling rate on the microstructure and hardness of the experimental steel was also studied and the results reveal that the full granular bainite microstructure could be obtained when the experimental steel was cooled at rate in the range of 0.25?2?/s.In such a case,the hardness reached up to 270HV.Partial martensite and bainite microstructure could be obtained when the cooling rate is lower than 20?/s,or t8/3>20s in the heat-affected zone(HAZ).(3)The flow stress curve of 13MnNiMoR steel deformed at elevated temperatures was obtained by a single-pass compression experiment in thermo-mechanical simulator.The influences of deformation conditions on the dynamic recrystallization and flow stress were studied.The results show that the higher the deformation temperature,the lower the strain rate,the greater the deformation,the more prone to dynamic recrystallization;and the rolling deformation temperature in non-recrystallization zone can be determined at 850-900?.(4)The effect of two important normalizing and tempering parameters on the microstructure and mechanical properties of experimental steel were studied by conducting laboratory hot rolling and heat treatment experiments.The appropriate parameters of hot rolling and heat treatment were established for 13MnNiMoR steel plate of 33mm in thickness(equivalent to the 105mm thick steel for the same compression ratio).The microstructure of the experimental steel is granular bainite and ferrite.The yield strength of experimental steel is 475MPa and the tensile strength is 670 MPa,while the elongation is 24.6%and the impact energy is 69J at 0?.The mechanical properties meet the requirements of GB713-2014 at elevated temperatures(<400?).