Experimental study of arc bubble growth and detachment from underwater wet FCAW

The bubble around the arc burning zone, defined as arc bubble, is the key factor to affect the process stability and joint quality in underwater wet welding. In this study, visual sensing of the bubble growth and detachment based on a high-speed camera in conjunction with a dysprosium lamp was realized. The extracted boundaries of a growing arc bubble were obtained via an image processing of the captured raw images. The bubble geometries were then calculated and determined. The relationships between the bubble geometries and welding heat input were experimentally investigated. Three distinct stages, including the formative stage, the elongation stage, and the detachment stage, were defined to describe the bubble growth along with a neck’s evolution. The variation trends of bubble geometries under different heat inputs were discussed to elucidate the bubble dynamic effect. For underwater wet welding, this provides a new orientation to promote the development of wet welding technology by sensing bubble growth.