Study On Weld Formation, Melting Rate And Weld Parameters Optimization For Variable Polarity Submerged Arc Welding

TANDEM submerged arc welding (TANDEM SAW) has been widely applied in thick plate steel structure due to its high efficiency and better weld joint. However, the superiority of TANDEM SAW was based on excessive energy, which can result in coarse grains in the weld and heat affected zone (HAZ) and poor mechanical properties of weld joint, especially toughness. Therefore, how to control the energy and high efficiency in TANDEM SAW is a key point the bottleneck in the production and further promotion, which can be solved by using the variable polarity SAW. In this paper, we can provide guidance to optimize the process parameters of the lead/ trail arc in TANDEM SAW by studying the effect of frequency, duty cycleβand offsetαof variably polarity SAW on the weld forming performance and the wire melting rate (WMR), and make the variable polarity power source apply in TANDEM SAW.The results showed that in the low frequency regime, that is below 50Hz, the frequency showed obvious effect on the weld forming performance. The penetration increased with the increase of frequency, but weld width showed opposite tendency. In the high frequency regime, which was over 50Hz, its effect on the weld forming performance was very slight. The effect of duty cycleβon weld forming performance had a lot common with offsetα. The penetration increased with the increase of duty cycleβand offsetα, and weld width was opposite with penetration. The experiment of the lead arc adopted super low voltage in TANDEM SAW was carried out and the results demonstrated that the greater penetration and the same weld performance were achieved by using this model, which had some practical value.A new mathematical model of wire melting rate (WMR), which considered the effects of duty cycleβand offsetα, was established for the variable polarity SAW. The experiments indicated that the error of the new model was no more than 9.6%. This model can be used to calculate the wire melting rate in actual industrial application. At the same time, WMR of the lead and trail arc in TANDEM SAW was measured. And the range of correction factor of this new model was given, which was applied in TANDEM SAW to be more accuracy. In addition, a multi-layer multi-channel interface of single (double) wire SAW has been developed using VB language, which can offer good guide to the technician in designing the optimization process parameters. And it was proved that the interface was practical with an example.