Research And Analysis Of Grain Size Of 304 Austenitic Stainless Steel Under Different Extrusion Processes

Due to its good formability and corrosion resistance,austenitic stainless steel has become one of the most widely used materials in engineering applications.However,the low strength and hardness of austenitic stainless steel has become a "bottleneck" restricting its wide application.In order to improve the strength and hardness of austenitic stainless steel and improve the quality of products,this article uses the equal channel corner extrusion pressing(ECAP)to strengthen 304 austenitic stainless steel materials,designing three new equal channel corner extrusion dies,combined with the existing research,the finite element analysis is carried out on the extruded specimen,and a method of combining simulation and experiment is adopted to obtain an effective strengthened mold.The main research contents of this article are as follows:(1)Using three-dimensional software to design three different extrusion process equal channel corner extrusion die,using simulation software to perform finite element simulation of the specimen obtained by extrusion,study the load curve,equivalent stress and strain and cross section during extrusion equivalent strain,and damage analysis.The results show that the change of the extrusion method will not affect the size of the punch load.The equivalent stress value of the equal channel corner extrusion died rotating 90° process is the smallest,and the equivalent strain value is the largest.The structure optimization and simulation analysis of the experimental die show that the optimized die extrusion can not only remove the cracks on the surface of the test piece after extrusion,but also meet the experimental requirements well.(2)Based on the theoretical model of plastic deformation,the grain structure of the specimens extruded by three different processes was simulated,and the size,dislocation density and grain boundary distribution of the grains during the extrusion process were analyzed.It is concluded that the angle of the slip surface of the 90° rotating extrusion process is closest to the theoretical value of the ideal state,and the grain boundaries are evenly distributed and the grain refinement effect is obvious.(3)The optimized die was used for the preparation of the extruded parts.In order to verify the optimal performance of the extruded parts,multiple passes of extrusion were performed during the preparation of this experiment,and the hardness distribution measurement of the test piece after the extrusion was completed.Calculation of standard deviation of hardness and analysis of metallographic structure of specimen.Experiments show that the uniformity of the test piece is significantly improved after the die is rotated by 90°,and the grains are refined,which is consistent with the simulation results.In this paper,through the combination of simulation analysis and experiment,it is obtained that the rotating 90° extrusion die is selected for 8 passes extrusion,and the stainless-steel material with the best refinement effect and the most uniform distribution can be prepared.