Effect of the water depth on the hydrogen content in SMAW wet welded joints

Jan Klett,Hans Jürgen Maier,Vitali Hecht-Linowitzki,Emily Schmidt,Oliver Grünzel,Thomas Hassel

doi:10.1007/s42452-020-3066-8

Abstract

Hydrogen-induced cold cracking is a huge challenge in underwater wet welding. In the present study, the influence of water depth on the diffusible and residually stored hydrogen content is investigated for the case of underwater wet shielded metal arc welding. The welding is carried out in a simulated water depth of 5, 20, 40, and 60 m with four stick electrodes specifically developed for underwater wet welding. The influence of the welding current, the arc voltage and the electrode’s composition on the diffusible hydrogen content are considered. To obtain reproducible welding conditions, a fully automated multi-axis welding system is used inside a pressure chamber. The water depth is simulated by setting the internal pressure up to 6 bar, equivalent to 60 m water depth. A large amount of samples are analysed and statistical method are used to evaluate the results. The results show a significant reduction of the diffusible hydrogen and an increase of residual hydrogen in the joining zone with increasing water depth.

Highlights

Hydrogen induced cracks are the main risks in underwater wet welding since they may occur delayed, up to weeks after welding
It has to be stated that only 2 samples were analysed by da Silva et al, which may explain the difference, because the variance in the residual hydrogen contents might be rather large at higher water depth (Fig. 8)
The results of this study show that the variance in hydrogen content (HD) is large in the wet welding process

Summary

Introduction

Hydrogen induced cracks are the main risks in underwater wet welding since they may occur delayed, up to weeks after welding. In the arc column the hydrogen is dissociated and ionized It returns to the atomic state in the colder arc areas and on the surface of the liquid metal. These conditions promote hydrogen diffusing into the weld metal. The materials commonly used in the offshore industry are ferritic-perlitic steels In these steels atomic hydrogen is able to diffuse rapidly even below room temperature [3]. The high cooling rates in the wet welding process promote high hardness in the heat affected zone (HAZ). This hardness usually rises with increasing yield strength, making higher strength steel prone to failure [5]. Even without external load, the weld seam presents a risk of failure

Methods

Results

Discussion

Conclusion