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.316 Ln Stainless Steel Forging Process Grain Evolution Law Of The Experiment And Simulation Studies

Posted on:2011-01-23Degree:MasterType:Thesis
Country:ChinaCandidate:M M ChenFull Text:PDF
GTID:2191360308471779Subject:Materials Processing Engineering
Abstract/Summary:PDF Full Text Request
316LN austenitic stainless steel, which show good mechanical properties and resistance to intergranular stress corrosion, has been a candidate for the key pieces of nuclear materials. But it seriously affect the mechanical properties of forgings when the quality problems about the existence of coarse grain and mixed grain on heavy forging.Thus,it is of significance importantly on a systematical study of the grain evolution of 316LN austenitic stainless steel in the heavy forging process to provide experiment basis for predicting the grain during the actual forging process,to lay the theoretical foundation for the preparation of the key technologies of heavy forging and to develop the microstructure simulation technology.The evolution law of grain and the technology of microstructural simulation were investigated by means of the combination of physical experiments and numerical simulation. Establishing a microstructural model is the core issue of the technology of microstructural simulation,thus this arctice carry out the basis research on the grain growth,dynamic recrystallization,static recrystallization and metadynamic recrystallization.The main conclusions are as follows:(1)Grain growth model was proposed when the regression error sum of squares was minimized and this model can predict accurately the grain growth during the heat treatment process.(2) The flow behavior of 316LN stainless steel during hot compression deformation was studied by Gleeble-1500D thermal mechanical simulator. This results show the relationship between the temperature, strain rate and the flow stress can described by the hyperbolic optional sine function based on the experimental data.Based on the method which was proposed by Poliak and Joans, the dynamic recrystallization of the critical strain was determined and the dynamic recrystallization kinetics equation was established.(3)The static softening behaviors were investigated by two-pass hot compression tests.The results show static recrystallization and meta-dynamic recrystallization softening curves are consistent with Avrami equation, showing the typical S-curves.Static recrystallization was affected larger by strain than strain rate, however, meta-dynamic recrystallization was on the contrary. The different deformation parameters was studied to obtain that the greater the strain was, the larger the fraction of static recrystallization was and the higher the strain rate was,the larger the dynamic Asia recrystallized fraction was.(4)Based on the coupling technology of macro-thermodynamic behavior and microstrcture evolution ,the established models wre inputted in DEFORM 2D software and the actual process of forging of the different repeated firings was simulated .The comparison of results by the simulation with the experiment show that the error was very small which verifies the reliability of the microstructure model.According to the results of forging of the different repeated firings , static recrystallization not only made the grain more refinement, but also made grain size distribution more uniform.While the results are verified by the numerical simulation, and then it proved the reliability of the microstructure model. Finally, based on DEFORM 3D software,a firings of stretching for pipe blake was simulated ,and the numerical simulation results predicted that the grain size of the maximum deformation area can reach between 59μm and 98μm .
Keywords/Search Tags:316LN stainless steel, Heavy forging, The evolution law of grain, The technology of microstructural simulation
PDF Full Text Request
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