Correlation between wire feed speed and external mechanical constraint for enhanced process stability in underwater wet flux-cored arc welding

Abstract

It is a great challenge to improve the process stability in conventional underwater wet welding due to the formation of unstable bubble. In this study, mechanical constraint method was employed to interfere the bubble generated by underwater wet welding, and the new method was named as mechanical constraint assisted underwater wet welding. The aim of the study was to quantify the combined effect of wire feed speed and condition of mechanical constraint on the process stability in mechanical constraint assisted underwater wet welding. Experimental results demonstrated that the introduction of mechanical constraint not only suppressed the bubble without floating but also stabilized the arc burning process. The degree of influence of mechanical constraint, which changed with wire feed speed, played an important role during the mechanical constraint assisted underwater wet welding process. For all wire feed speeds, the fluctuations of welding electrical signal were decreased through introduction of mechanical constraint. The difference in the proportion of arc extinction process between underwater wet welding and mechanical constraint assisted underwater wet welding became less with increasing wire feed speed. At wire feed speed lower than 7.5 m/min, the improvement of process stability was very significant by mechanical constraint. However, the further improvement produced limited effect when the wire feed speed was greater than 7.5 m/min. The observation results showed that a better weld appearance was afforded at a large wire feed speed, corresponding to a lower variation coefficient.

Effect of Electrode Waterproof Coating on Quality of Underwater Wet Welded Joints

“…These three types of electrodes caused the highest values of hardness in HAZ ( Section 3.3 ). Obtained results confirmed literature information [ 5 , 13 , 34 , 35 , 36 ], that high hardness increases the susceptibility of steel to cold cracking. The lowest number of parallel cracks in HAZ were observed in specimens welded by electrode with impregnate for concrete ( Figure 9 c).…”

“…The usage of paraffin wax caused hardness reducing by 20-40 HV10 in HAZ in comparison to electrode without additional hydrophobic layer and by 40-50 HV10 in comparison to underwater electrode. Expected hardness reducing in HAZ (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40) was also observed in specimens welded with electrodes with concrete impregnate. The significant differences were found in the weld.…”

“…Chen et al [32] and Wang et al [33] proposed ultrasonic-assisted welding, which improves the quality of underwater joints. Wang et al [34,35] proved also that external mechanical constraint caused improvement in stability of process, which affects the size of the bubble around the arc burning zone. The larger heat input provides a large possibility for a better protective effect and a larger weld penetration.…”

Weldability of Underwater Wet-Welded HSLA Steel: Effects of Electrode Hydrophobic Coatings

“…This lowers the quality of the welded joints. Wang et al [ 14 ] stated that stability of the welding arc depends on the welding parameters. They found that lower welding current values increased the stability of the welding arc in wet welding conditions.…”

Plasticity of Bead-on-Plate Welds Made with the Use of Stored Flux-Cored Wires for Offshore Applications

“…Despite the great practical significance of problems associated with the storage of welding consumables, this topic is relatively rarely discussed in the literature. Previous works mainly concerned the impact of wire construction and storage conditions on the diffusible hydrogen amount in weld metal [ 18 , 22 , 38 ] and the influence of welding parameters and conditions on the quality and properties of welded joints [ 20 , 39 , 40 , 41 , 42 ]. Accordingly, the purpose of the work was to analyze the impact of storage conditions of seamless, copper plated flux-cored wires on the plasticity of the bead-on-plate welds made with these wires.…”