Research On Microstructure Evolution And Numerical Simulation Of 12%Cr Ultra Supercritical Rotor Steel

Heavy forgings manufacturing is a complex process,which includes ingot smelting,forging,and heat treatment.Two of the most important aspects are forging and heat treatment.The uneven grain and deformation of heavy forgings will affect the comprehensive performance of the products to a great extent,which will also lead to the product scrap.The temperature of deformation,the press measure and whether the deformation have effect on the complex microstructure evolution,the grain size and homogeneity of final products.If all of these parameters are not controlled properly,it will bring great trouble to the subsequent heat treatment.Therefore,it is a great significance to study the microstructure uniformity,the evolution of the internal microstructure and the grain size distribution in the forging process.In this paper,12%Cr ultra supercritical rotor steel was adopted.Firstly,the austenite grain growth law of the steel at different heating temperature and different holding time were obtained.And Combined with the nonlinear regression analysis and Arrhenius grain growth model,the growth kinetics equation of the austenite grain was attained.Secondly,using the method of scaling test and numerical simulation technology,the influence of the upper flat and lower V-shaped anvils with different ratios on 12%Cr ultra supercritical rotor steel microstructure evolution was analyzed.In this step,the distribution of garin size and the deformation homogeneity were obtained in different sections of the feature point.And the results of experiment and numerical simulation were compared.Compared to the results of numerical simulation and scaling test,it can be realized that uneven deformation increases when forging ratio gradually increases from 1.1 to 1.3 in the process of forging.However,the average grain size decreases in this process.And the forging microstructure inhomogeneity also had a steady improvement.Finally,with the use of DEFORM-3D numerical simulation technology,the forming characteristics of 12%Cr ultra supercritical rotor steel were studied under other three different anvil types of stretching,which are the upper and lower flat anvils(FM stretching),the upper flat and lower trapezoid anvils and the upper and lower trapezoid anvils.The advantages and disadvantages of the four kinds of anvil stretching were analyzed from the aspects of equivalent strain,equivalent stress,temperature field and percentage of dynamic recrystallization.The results show that the effects of retching are superior by the methods of the upper flat and lower V-shaped anvils and the upper flat and lower trapezoid anvils.