Investigation of microstructure and mechanical properties of 304 stainless steel under high-frequency vibratory arc conditions

Abstract

In traditional cross-coupled welding, the main arc swings with the polarity changes of the bypass arc, leading to uneven heat distribution and compromising the decoupling of heat and mass transfer. To address this issue, a new cross-coupled welding method based on high-frequency bypass arc was developed. When the bypass arc operates at a high frequency of over 20 kHz, the main arc does not significantly swing with the polarity shifts. Instead, it vibrates at a high frequency with a small amplitude. To verify whether this vibration behavior influences the molten pool flow and promotes grain refinement, a series of experiments were designed and conducted. The results showed that, under identical conditions, the weld width produced by cross-coupled welding with a 50 Hz bypass arc is greater than that of tungsten inert gas welding (TIG) welding. However, under high-frequency bypass arc conditions, the weld width is similar to that of TIG welding, indicating a more effective decoupling of heat and mass transfer in this method. Moreover, compared to TIG welding and low-frequency cross-coupled arc welding, the high-frequency bypass cross-coupled method refines the weld zone grains, enhances material toughness, and improves the tensile properties of the weld.