Research Of Process Stablity And Distribution Temperature Field In Triple-wire High Speed GMAW

With the development of the society, the field of high-efficient welding has become an important direction of welding subject. When improving the welding speed,the most important issue is the instability of the process and the subsequent weld geometric defects such as undercut and humping . In this paper, triple-wire automatic welding systems, data acquisition and analysis systems, and high-speed camera system has established a complete set of triple-wire GMAW welding test platform, then the arc shape and the electrical signal was analyzed to achieve the comprehensive analysis of the stability during triple-wire GMAW welding process.In order to get a further understanding of the arc stability and study the regular phenomenon of arc interruption during the twin-wire welding process, a series of experiments (arc voltage matching,welding current matching and inter-wire distance matching) are designed , then synchronous high-speed camera system is used to take a picture of arc shape and data acquisition system based on Labview is used to collect current and voltage waveforms simultaneously during the welding process. Then histogram is used to analyse the arc stability and the above-mentioned experiments come to nearly the same conclusion: decreasing the voltage of trailing arc, decreasing the current ratio between trailing arc and leading arc and increasing the inter-wire distance will enhance the leading arc stability;decreasing the current ratio between leading arc and trailing arc,decreasing the voltage of trailing arc and increasing the inter-wire distance will decrease the frequency of interruption of the trailing arc.Finally, Combine the captured images of the arc with the acquisition of current,voltage waveforms and analyse the arc interruption phenomenon occurred in the welding process.After that,the experiment of arc stability of triple-wire GMAW was performed. The results show that there is no arc interruption of triple-wire GMAW by properly selection of interwire distance and welding current ratio on a base of twin-wire welding experiments and theoretical analysis. Moreover, according to displacement formula derived through the twin-wire model and the theory of superimposition principle of electromagnetics, a displacement formula of triple-wire model are deduced with different polarities combinations.Analyses the symbol of displacement and get the conclusion: polarity combination of leading wire/DCEP-middle wire/DCEN-trailing wire/DCEP(P-N-P combination for short) and leading wire/DCEN-middle wire/DCEP-trailing wire/DCEN(N-P-N combination for short) are best polarity combinations.Then a series of experiments of different polarities combinations are designed. Finally, combining the captured images of the arc with the acquisition of current,voltage waveforms and formation of weld ,analyse the best polarity combinations synthetically and come to an conclusion:the polarity combinations of P-N-P and N-P-N get a better arc stability,formation of weld and less welding spatter than others. The problem of process stability is solved successfully.Eventually,a calculating formula of Gaussian model in triple-wire welding is derived according to arc shap and the superimposition principle of heat resource, and the proper finite element model is constructed. at the same time, the motions of welding heat resource are actualized by the means of programming with APDL of ANSYS . Then the transient change of temperature field of T-joint is simulated in triple-wire high speed welding process with the boundary conditions of convection,radiation,evaporation,fluid flow and latent heat of phase change being fully considered. Finally, the simulated results are being analyzed and checked out with experiment, which has also validated the dependability of the above-mentioned mode1.