Study On Milling Process And Stress Corrosion Of Nuclear Austenitic Stainless Steel

Austenitic stainless steel is an important structural material for nuclear power equipment and is widely used in nuclear power plants.During the service of nuclear power plants,stress corrosion cracking of austenitic stainless steel structural components has been one of the core problems that have plagued the safe operation of nuclear power plants for many years,and surface cutting processing will affect its service in nuclear high temperature and high pressure water environment.As a difficult-to-machine material,the coupled thermo-mechanical effect of austenitic stainless steel during the cutting process determines the magnitude and nature of the surface residual stress,and the residual stress on the surface of the machining still lacks a deep understanding of the effect of stress corrosion resistance.In this paper,AISI304 austenitic stainless steel is taken as the research object.The combination of experiment and finite element simulation is used to analyze the influence of the interaction between thermal and mechanical effects of milling on surface residual stress,and the stress corrosion resistance of the machined surface is systematically analyzed.Firstly,the four-way piezoelectric dynamometer and infrared thermal imager are used to monitor the distribution of the milling force and the temperature field around the blade-to-chip contact area.The milling parameters and milling-to-chip are studied.The effect of the temperature field near the contact area.The indentation strain method was used to measure the residual stress of the machined surface,and the nature of the surface residual stress and its variation under the combined action of mechanical and thermal effects were qualitatively analyzed.Secondly,the finite element model of 3D milling is established by ABAQUS to study the milling process more intuitively.The distribution of transient temperature field,stress and strain field during the separation process between chip and workpiece is analyzed.Through multi-step sequential coupling analysis,after clamping,After the four processes of feeding,retracting and constraining conversion,the distribution of the residual stress field of the machined surface is obtained,and the experimental results are compared with the simulation results.Finally,the effect of milling on stress corrosion cracking of AISI304 austenitic stainless steel was studied in boiling magnesium chloride solution.In the whole dynamic evolution process of stress corrosion cracking from initiation-rapid growth-basic stagnant growth,the stress corrosion crack morphology,micro-corrosion product element composition and crack growth rate were studied.The correlation betweensurface residual stress and the growth rate of stress corrosion cracks was analyzed.