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Underwater wet welding technology is widely used. Because the stability of droplet transfer in underwater wet welding is poor, the feasibility of improving the droplet transfer mode has been discussed from various technical directions. In this work, the characteristics of pulsating wire feeding were studied in the pulsating wire feeding mode by investigating the effects of changing the pulsating frequency, the wire withdrawal speed, and the wire withdrawal quantity on the droplet transfer process and the welding quality. With the aim of improving weld forming and welding stability, the authors selected the coefficient of variation and the ratio of unstable droplet transfer as the indexes to evaluate the effect of droplet transfer control. The pulsating wire feeding process of underwater wet flux-cored wire was analyzed in depth, and the following conclusions were drawn: using the pulsating wire feeding mode and after comparing and analyzing the pulsed wire feeding process under the same frequency condition, the authors found that the forming and stability were better under the conditions of slower withdrawal speed and smaller withdrawal quantity. The short-circuit transition ratio decreased steadily with the increase of pulsating wire feeding frequency, the rejection transition ratio first rose and then decreased, and the splash ratio first decreased and then rose. [ABSTRACT FROM AUTHOR]

To determine the arc stability during underwater wet welding in boric acid solutions with various concentrations, a real-time electrical signal acquisition system is established. Four methods for determining the arc stability, i.e., dynamic characteristics, probability distribution of voltage and current, current and voltage cyclograms, and coefficients of variation of voltage and current, were adopted. There were two short-circuited modes, which referred to the long-periodic short-circuits model and the short-periodic short-circuits model. Metal transfer images of the two modes were obtained, and the proportion of the long-periodic model increased with the concentration of boric acid in aqueous solution. The arc stability during underwater wet welding deteriorated with increasing the boric acid concentration. [ABSTRACT FROM AUTHOR]

The metal transfer process of underwater flux-cored wire wet welding is successfully observed by an X-ray transmission method. The relatively large retention forces acting on the droplet induced by the electromagnetic force, vaporization force, surface tension resultant force and gas flow drag force make the transfer mode as a combination of globular repelled transfer mode and short circuit transfer mode with the average transfer frequency of 4.3 Hz with arc voltage of 24 V and welding current of 240 A. [ABSTRACT FROM AUTHOR]