Numerical Simulation Of Heat Treatment Process Of SA508-3 Nuclear Power Large Forging Steel

As the last step to improve the performance of the workpiece,heat treatment occupies an irreplaceable position in mechanical processing,especially for the heat treatment of large forgings.The heat treatment of large forgings is a complicated process.Due to its many influence factors and complex boundary heat transfer conditions,it has many uncontrollable aspects in heat treatment.With the development of technology,the performance requirements of large forgings are getting higher and higher,which requires in-depth research on its heat treatment.However,due to the lack of a performance database for large forgings and the variable changes during heat treatment cannot be observed in real time,this work is somewhat difficult.Therefore,it is of great significance to study the numerical simulation of heat treatment of large forgings.This paper took the domestic SA508-3 nuclear power forging steel as the research object,and studied the transient temperature changes,microstructure evolution,stress changes,and performance distribution after heat treatment of the forging during heat treatment.In this paper,the numerical simulation model of SA508-3 steel heat treatment is developed based on ABAQUS and Python software.In this paper,the TTT curve of SA508-3 steel,the transformation temperature of each phase and the specific pressure specific heat of martensite are calculated by JMat-Pro software.The constant pressure specific heat of martensite is obtained through experiments,and the two agree well with the calculated data.Furthermore,the calculated data is compared with the existing experimental data to verify the reliability of the calculated results.On this basis,the thermal physical parameters of SA508-3 steel such as density,specific pressure specific heat,thermal conductivity and phase change latent heat,as well as mechanical property parameters such as yield strength,Poisson's ratio,linear expansion rate,and Young's modulus and trimming modulus.Established a relatively complete SA508-3 steel heat treatment performance library.The Jominy end-quench test and its influence on microstructure of the SA508-3 steel was studied using numerical and experimental techniques.Finite element simulations of this test were measured including temperature field distribution and phase transformations modelling.These models were implemented in FLIM and UMATHT programming subroutine and metallographic transformations during the Jominy end-quench test.Distributions of the Microstructural in the sample after the tests were determined.The microstructure of the quenched samplescontinuously changes from martensite to bainite and small amount of retained austenite with increasing distance from the water cooled surface,no ferrite and perlite were observed in the samples after quenched and the half-martensite distance is arrest in 9 mm from the quenched end.The calculated results are in good agreement with results of the metallographic observation.The simulation results of hardness and tissue evolution are in good agreement with the experimental results.This verified the accuracy of the established numerical model.Then this paper uses the numerical model established and verified in the previous work to simulate the heat treatment process of a large nuclear power forging of SA508-3 steel.The temperature changes and microstructure evolution of large forgings during heating and spray quenching are given.The stress changes at the five positions from the surface to the core during heating and the distribution of the final residual stress are also given.The results of the study indicate that there is a risk of cracking during heating of this large forging.The final residual stress is large and it should be tempered immediately.Finally,reasonable suggestions for optimizing the heat treatment process of large forgings are given.The research results of this paper can be used to provide guidance for the formulation and optimization of the heat treatment process of SA508-3 steel large forgings.