Simulation Of Gas Quenching Process And Its Multi-objective Optimization

The heat treatment process can improve the integrative mechanical properties of the materials and make up for the defects of the material itself. With the continuous improvement of material properties, the heat treatment process also needs to be improved. There exist some defects such as large residual stress, in the traditional quenching process of liquid medium, which seriously affect the performance of the material. In this paper, the gas was used as the quenching medium, which avoids the defects of the traditional quenching process. The paper focused on the influential factors of gas quenching process by numerical simulation, conducted multi-objective optimization by coordinated simulation, and checked the reliability of the simulation results by experiments.First of all, the numerical heat transfer principle of gas quenching cooling process simulation was described. Through the study on the interactive effects between the parameters and the influential factors of the jet impingement heat transfer, the paper reckoned that nozzle gas velocity is the most influential factor to the cooling rate, while the effect of height(h) and center distance(s) of nozzles on the cooling rate is interactive. The simulation model of the gas quenching process of variable thickness disk was established. Through simulation, some defects were found in the process of gas quenching, so multi-objective optimization of gas quenching cooling system was proposed.Secondly, the parameters which affect the cooling effect of gas quenching were divided into the structural parameters and the velocity of flow parameters, and the evaluation index of the effect of gas quenching was established. The global nondominated sorting genetic algorithm II(NSGA-II) was used as a multi-objective optimization algorithm for the gas quenching process. Based on Isight which is a software used as computer aided optimization(CAO) integrated FLUENT and other software to carry out the coordinated simulation and optimization, the simulation and optimization of gas quenching process was established, through the optimization, structural parameters and velocity of gas flow were optimized, the cooling effect has been improved, and the Pareto front edge of multi-objective optimization was obtained. Due to the low calculation efficiency through Isight direct drive FLUENT and other software to coordinated simulation and optimization, the optimal Latin hypercube experimental design by means of Isight for the simulation of gas quenching process, the neural network model of the gas quenching process was established by the simulation results. Based on this model, the multi-objective optimization of the gas quenching process was conducted, and the optimization efficiency was improved.Finally, the control network with single master node and multi slave nodes of the inverter was established based on RS-485 bus, the open loop control program was written by Lab VIEW, which solved the problem of data conflict in RS-485 communication network, and established the air supply system of air quenching experiment. The nozzle layout and velocity of flow were provided according to the results of simulation and optimization, the temperature data inside the disk was collected during the gas quenching cooling experiment by thermocouple, and compared with the simulation data, the error was below 7%, which verified the reliability of simulation and optimization results of variable thickness disc air quenching cooling process.