Study On The Grain Evolution Of 316LN Steel During Thermal Deformation And Solution Treatment

As a key component of nuclear power,316 LN austenitic stainless steel has good mechanical properties and resistance to intergranular stress corrosion.The third-generation nuclear power technology AP1000 main pipeline adopts integrated forging shape,which greatly improves the difficulty of manufacturing and processing.Therefore,the main pipeline of nuclear power often has quality problems such as mixed crystal or abnormal grain growth during hot processing,which seriously affects the mechanical property of forgings.In this paper,316 LN austenitic stainless steel was used as the research object,the different microstructure of 316 LN was obtained by wedge blank forging test.The effects of different strain on the dynamic recrystallization fraction and grain size distribution of 316 LN austenitic stainless steel and the evolution behavior of orientation difference and special grain boundaries of 316 LN after thermal deformation process were studied by numerical simulation based on DEFORM.According to the microstructure of different dynamic recrystallization fraction after thermal deformation of 316 LN austenitic stainless steel,EBSD technique was used to study the evolution behavior of grain size,orientation difference and special grain boundaries during solution treatment.After the thermal deformation,the grain evolution rules on dynamic recrystallization fraction of 14%,50% and 95% during the solid solution is obtained,and under the same solid solution process,effects of different dynamic recrystallization structure s on grain size,orientation difference and special grain boundary evolution after solid solution is obtained.According to the microstructure with same dynamic recrystallization fraction and different thermal deformation parameters of 316 LN after thermal deformation,the change behavior of grain size and distribution under the same solid solution process was studied.Based on the experimental data and the numerical simulation based on DEFORM,the grain size distribution map of 316 LN after solid solution was established.The relationship between the thermal deformation parameters ?,lnZ and the average grain size after solid solution was delineated,and the region with abnormal grain growth is easy to occur after the solid solution is obtained.