Microstructure And Mechanical Properties Evolution And Finite Element Analysis Of Stainless Steel During Hot Processing

With the continuous development of China's stainless steel industry,stainless steel is increasingly used in daily life,industrial production and other fields.Continuous improvement of its production and preparation technology is a basic requirement for researchers,and ensuring and improving its performance is the ultimate goal pursued by researchers.In this paper,316H austenitic stainless steel and 2101 duplex stainless steel were studied.The high temperature hot deformation behavior of 316H austenitic stainless steel and the intergranular corrosion resistance under different initial conditions were studied by single pass compression thermal simulation experiment and cyclic soak corrosion test.The AN SYS finite element software was used to analyze the variation of instantaneous temperature and stress distribution of 316H austenitic stainless steel thick slab and 2101 duplex stainless steel thick slab with heating process.The LS-DYNA finite element software was used to analyze the difference of strain between two phases of 2101 duplex stainless steel thick slab during rolling.To provide theoretical basis and reference basis for industrial production and performance improvement of 316H austenitic stainless steel and 2101 duplex stainless steel.The main contents and innovations of this paper are as follows:(1)The rheological behavior and microstructure evolution of 3 16H austenitic stainless steel under different deformation conditions were studied by single pass compression thermal simulation experiments.The results show that the deformation resistance of 316H is higher than that of 316L under the same conditions due to the increase of C content.Based on the flow stress curve,the deformation resistance model is established by the coupled strain Arrhenius equation,it can better predict the rheological behavior during thermal deformation.By combining the laws of microstructure evolution,the main softening mechanism of 316H is dynamic recrystallization.Dynamic recrystallization nucleation mainly relies on discontinuous dynamic recrystallization to produce a "necklace"structure.As the deformation temperature increases,the deformation rate decreases,and the degree of recrystallization increases.(2)The effects of solution treatment time on the grain size of 3 16H austenitic stainless steel,the chromium-depleted zone,the precipitation at the grain boundary and the resistance to intergranular corrosion were studied by solution treatment experiment,sensitization treatment experiment and cyclic soak corrosion test.The results show that the longer the solution treatment time is,the larger the grain size is.The distribution of chromium carbide precipitates such as M23C6 and M6C at the grain boundary is more dispersed and less in the grain boundary,and the weight loss rate is lower after the cyclic soak corrosion test.The higher the resistance to intergranular corrosion.The solution treatment time has little effect on the grain boundary distribution,which mainly affects the grain size.The larger the grain size,the smaller the number of grain boundaries,the less nucleation and enrichment of precipitates.At the same time,the carbon atoms diffuse into the crystal.The slower the vicinity of the boundary,the less the chromium carbide precipitates at the grain boundary,and the lighter the chromium deficiency,resulting in an increase in the resistance to intergranular corrosion.(3)The transient temperature and stress distribution of 316H austenitic stainless steel and duplex stainless steel slab during reheating were analyzed based on ANSYS finite element method,and the variation law with process parameters was analyzed.In the reheating process of 316H,considering the factors of improving heating efficiency and reducing the risk of hot cracking,the total heating time can be appropriately reduced.Considering the high temperature strength,plasticity state and strain distribution of austenite and ferrite phases,the phase boundary cracks of 2101 duplex stainless steel are mostly derived from the phase boundary and extend to the ferrite phase region.(4)Based on the ANSYS/LS-DYNA finite element method for the analysis of 2101 duplex stainless steel rolling process,the deformation of the austenite phase zone is significantly smaller than that of the ferrite phase zone due to the difference of the two-phase material constant and high temperature strength,and the strain occurs at the phase interface.Sudden rise or fall changes,and significant strain gradients induce crack initiation at the interface.When the rolling temperature is lowered from 1150 ? to 950?,the temperature becomes lower,and the difference between the two corresponding ratios becomes larger,and cracks are more likely to occur.