Research On The Heat Treatment Process And Performance Of 403 Stainless Steel Nuclear Power Forgings

Nuclear power forgings are the key components in the nuclear power plant.We are start an experiment and numerical simulation under unstable performance of 403 stainless steel nuclear power thrust bearing seat after quenching and tempering in Guizhou Aerospace Xinli Casting and Forging Limited Company.Physical properties and microstructure transformation parameters of 403 stainless steel are obtain by material performance experiment and calculation software.Using the numerical simulation of the heat treatment process of nuclear power thrust bearing seat,the temperature distribution,microstructure evolution and performance of thrust bearing seat are analyzed during heat treatment and study the effect of heat treatment process parameters on unstable performance.This study also give a reasonably explanation of unstable performance,which is the incomplete austenitization.Finally,the heating and cooling process of403 stainless steel forging are optimize and explore based on the simulation model,which provide the theoretical guidance for the optimization of heat treatment process of 403 stainless steel forging.Upon holding the furnace temperature at 970°C for 1.5 hours,403 stainless steel forging does not reach Ac₃ temperature thus not fully austenitization,and this region retains its initial microstructure of ferrite and carbides.Austenite transform into martensite at the edge of the forging section after quenching,but the austenite decompose into ferrite and carbides at two region of forging because the cooling rate is lower than the lowest critical cooling rate,giving rises to inhomogeneous microstructure and inferior properties.Finite element numerical simulation are employed in the study on heating process of 403stainless steel forging by coupled user subroutines.Simulation results show that the temperature of upturned forging is 20? higher than the upright at the same position after holding 1.5 hours.If holding time is expanded to 3.0 hours,temperature is vary between 873? and 952? from core to surface of the forging,and the residual ferrite and carbides are completely transformed into austenite.However,the forging temperature of surface and core can touch value between964? and 970? after holding 7.0 hours if the furnace have reached 970?.In the process of heating with the furnace,residual stress increased with the heating time and then decreased.The ways of entering the furnace have little effect on the distribution of equivalent stress.The residual stress peak is higher than other which the way of heating with furnace and appears in advance.The cooling process of 403 stainless steel forging is explore based on the simulation model.The study shows that austenite is transform into martensite distributing on the surface layer of the forging section,and ferrite and carbides are generated in the core of the forging section when the water spray intensity is vary from 10 L/?m²·s?to 90 L/?m²·s?.In addition,the cooling rate of the surface layer is greater with the higher of water spray intensity on the surface of the forging,but there is no obvious promotion on the area of the martensite in the surface layer of the forging section.The cooling rate in the core of the forging section are gradually increasing with the water spray intensity increasing from 10 L/?m²·s?to 50 L/?m²·s?.However,the cooling rate in the core of the forging section is keep constant once the water spray intensity over 50 L/?m²·s?.