| Steel castings are widely used in the manufacturing industry,especially high-speed railways,automobiles,construction machinery and other advanced manufacturing industries.With China's manufacturing industry gradually moving to the high end,improving the quality of steel castings has become an urgent issue to be solved.Heat treatment can improve the organization and reduce defects.It is a key step in improving the quality of steel casting production.It has become a crucial issue to improve the heat treatment process and the level and efficiency of making process.In recent years,numerical simulation technology has gradually become an effective method for studying the heat treatment of cast steel parts.Compared with the traditional methods,it can predict the organization and performance,change the blindness of heat treatment process formulation,ensure the quality of steel castings,and shorten production cycle,increase productivity.However,there are still some problems such as the lack of clear application scope of the calculation model and lack of experimental verification data.Therefore,based on the InteCAST system,according to different calculation models,the organization and performance prediction system was independently developed in this thesis.The heat treatment process of the cast steel specimens was simulated and verified by experiments to standardize the scope of the model and improve the calculation method,so that we can predict the organization and performance,help process technicians to improve the process,and guide the heat treatment production.The main research work is as follows:First,we independently developed the heat treatment organization and performance prediction system for steel castings.Based on the pre-processing of InteCAST,the grid was meshed;using the finite difference method,the heat-transfer differential equation was discretized into a differential equation set,and the initial temperature and the temperature change curve were calculated by iterative method based on the initial conditions and boundary conditions;Based on the characteristics of the diffusion type and non-diffusion type transitions,a transition model for phase transformation of steel castings was established based on the TTT curve using the superposition law.The hardness calculation model was established based on the weighted average of the hardness of each phase.Based on the development platform,Studio 2013,calculation program to predict the microstructures and performance for steel castings in heat treatment has been developed.In the calculation process,the physical parameters change with temperature,according to the material composition,obtained by the JMatPro software,the program is input in the form of coordinate points,and the parameter values at a certain temperature are obtained by interpolation;the calculation results are displayed in the Tecplot,and also It can output the file that can be displayed in China Casting CAE.Secondly,the heat treatment experiments of steel castings with different compositions under different insulation conditions and different cooling methods were carried out.Metallographic analysis and hardness tests were carried out.Simulations were performed using the developed calculation program and compared with the experimental results.The results showed that the prediction system can accurately reflect the type,content,and distribution of the microstructure in heat treatment process under different conditions,and the hardness prediction value is also relatively accurate,so the desired results is achieved.Finally,in cooperation with Guangweitong Company,more than two thousand actual heat treatment processes in the plant were sorted out.The heat treatment process was simulated using this calculation procedure and compared with the actual measurement results.The results show that the prediction results are accurate and the prediction system can play a guiding role in making process,can be applied in the actual heat treatment. |
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