Research On VP GMAW Welding System And Welding Process For Sheet Metal

With the improvement of technology level and the demand of lightweight products,sheet metal is widely applied in automobile,aerospace,container and other fields.However,the deformation of the metal sheet is easy to occur in the welding process,of which the stiffness and deformation resistance is small.What is more,the sheet will be burned through as long as the heat input is lightly higher.Compared to the traditional GMAW,variable-polarity GMAW welding technology is a good way to reduce the heat input and avoid the deformation.By tuning the welding current and the ratio of EP and EN time,the heat input of the sheet can be reduced.Therefore,it is necessary to build a stable and reliable variable polarity GMAW welding system.This paper first introduces the background and significance of the topic about current problems sheet metal welding and the development status of low heat input welding technology,based on which the variable-polarity GMAW welding system is constructed,the welding waveform control scheme is designed,and the dynamic welding simulation model is established.The simulation model includes variable polarity power supply model,dynamic arc load model and corresponding control system model,which can simulate the whole welding process completely and lay the foundation for hardware design and software design.The hardware part of the welding system mainly includes the design of two inverters topology of the main circuit and the analysis of the operation principle,as well as the design of the corresponding peripheral control circuit.The software part mainly includes the design of the whole control strategy of the welding system and the specific welding control process.In addition,the state-space average method is applied to establish the transfer function of the power supply,and further the design method of PI controller is introduced in detail.Finally,variable polarity GMAW welding system is built on the basis of the above analysis and design.And then,the performance test of the prototype is carried out to verify the feasibility,and the welding experiment is carried out on the 3mm thick low carbon steel plate to study the relating to the influence of various welding process parameters to the energy allocation.And another welding experiment is carried out on the 1mm thick sheet to verify the feasibility of the scheme.The experimental results indicate that the welding process of the welding system is stable,the workpiece deformation is little and the waveform control is accurate,which achieve the target of thin plate welding.