Abstract
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.
Highlights
With the fast-developing exploitation of marine resources, underwater welding technology is becoming more and more important [1,2]
We investigated the effect of pulsed wire feeding on the droplet transfer process of underwater welding under different pulse frequencies and pulse duty ratios, and explored the control method of droplet transfer to improve the quality of underwater wet welding
In order to further suppress the proportion of the transition process and improve the stability of the welding process, the wire feeding process can be introduced on the basis of the pulsed wire feeding technology, and the wire feeding mode of “one delivery, one stop” is converted into the “one delivery-one pumping and one stop” mode to speed up the droplet transfer process
Summary
With the fast-developing exploitation of marine resources, underwater welding technology is becoming more and more important [1,2]. Underwater welding technologies based on traditional fusion welding methods in air have developed greatly in recent years, but trials and engineering applications demonstrate that troublesome issues still remain with underwater wet fusion welding, especially in the deep sea, such as hydrogen embrittlement, arc instability, etc. The underwater wet FCAW-S welding technology has attracted more and more attention because of its high welding efficiency and its applicability to automatic welding [7]. Sun et al developed ultrasonic-assisted underwater wet welding equipment, including a welding system, an ultrasonic system, and a composite torch. Kong et al introduced in detail a method for measuring the fluid discharge of diffusible hydrogen in weldments.
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