| In the industrial field,plasma arc has developed rapidly because of its arc column energy concentration,high temperature and excellent performance of almost penetrating any metal.In recent years,the research of plasma arc cutting technology tends to be mature,but the research of plasma arc cutting technology in high-pressure environment(greater than0.1MPa)is still in the embryonic stage,the research theory of plasma arc ionization behavior in high-pressure environment is not mature,and there is less research on plasma arc cutting technology in high-pressure environment.Based on the project "Research on robot plasma arc cutting technology of large buried depth and high water pressure shield cutterhead",this paper studies the plasma arc cutting technology suitable for high-pressure environment,explores the changes of plasma arc ionization behavior in high-pressure environment,and explores the plasma arc cutting technology in high-pressure environment.In this paper,high-frequency and high-voltage arc striking technology and non high-frequency arc striking technology are adopted.Through the improvement and optimization of the existing commercial plasma arc cutting machine,the arc striking cutting under 0.6MPa environmental pressure and 1MPa environmental pressure are realized respectively,which overcomes the problems of no arc striking and difficult arc striking under high-pressure environment.The research shows that the cutting quality becomes worse with the increase of environmental pressure.The effects of different process parameters on cutting quality were studied by controlling variable test.For the multi index problem of plasma cutting quality evaluation,the comprehensive scoring method is used to reasonably determine the weight ratio;Through orthogonal test and visual analysis,the optimal cutting process parameters under 0-0.7mpa high pressure environment are obtained.The research shows that when the power excitation energy meets the requirements,with the increase of environmental pressure,the air supply pressure becomes the main process parameter affecting the cutting quality.Using the welding camera system,the plasma arc morphology under different high pressure environment was studied.The analysis of arc morphology shows that the plasma arc stiffness decreases and the stability becomes worse with the increase of ambient atmosphere pressure.Combined with the orthogonal test data and comparing the appearance data of the front and back of the notch,it is found that the arc shrinks gradually,the length becomes shorter,and the notch width increases,but the trend is not very significant.In order to further analyze the relationship between the change of arc ionization behavior and cutting quality in high pressure environment,a magnetohydrodynamic model(MHD)of plasma arc was constructed.Using ANSYS fluent simulation software and its secondary development interface,the numerical simulation of arc model is completed.The calculation results show that the arc shrinks and the stability becomes worse with the increase of ambient atmosphere pressure and the distribution of arc temperature and velocity.From the change of workpiece temperature distribution,it can be concluded that the notch width increases and the trend is small,resulting in poor flatness and poor cutting quality.Therefore,the arc shrinks,but the notch widens,which is reasonably explained.The numerical simulation results are in good agreement with the experimental results. |
