Hydrogen-assisted cracking is a major challenge in underwater wet welding of high-strength steels with a carbon equivalent larger than 0.4 wt%. In dry welding processes, post-weld heat treatment can reduce the hardness in the heat-affected zone while simultaneously lowering the diffusible hydrogen concentration in the weldment. However, common heat treatments known from atmospheric welding under dry conditions are non-applicable in the wet environment. Induction heating could make a difference since the heat is generated directly in the workpiece. In the present study, the thermal input by using a commercial induction heating system under water was characterized first. Then, the effect of an additional induction heating was examined with respect to the resulting microstructure of weldments on structural steels with different strength and composition. Moreover, the diffusible hydrogen content in weld metal was analyzed by the carrier gas hot extraction method. Post-weld induction heating could reduce the diffusible hydrogen content by −34% in 30 m simulated water depth.

The European standard ISO 3690 regulates the measurement of diffusible hydrogen in arc-welded metal. It was designed for different welding methods performed in dry atmosphere (20% humidity). Some details of the standard are not applicable for wet underwater welding. The objective of this study was to extend the applicability of DIN EN ISO 3690:2018-12 to underwater wet-shielded metal arc welding (SMAW). Four different aspects regulated within the standard were accounted for: (1) sample dimensions and number of samples taken simultaneously; (2) time limitations defined by the standard regarding the welding and the cleaning process; (3) time, temperature, and method defined for analysis of the diffusible hydrogen content; (4) normalization of the hydrogen concentration measured. Underwater wet welding was performed using an automated, arc voltage-controlled welding machine. The results are discussed in light of standard DIN EN ISO 3690, and recommendations are provided for the analysis of diffusible hydrogen content upon underwater wet welding.

One promising approach to keep the residual oxygen level in welding at extremely low levels is to add monosilane to the argon shielding gas. However, its effect on the plasma itself is not clear, and thus this study examines the influence of a silane‐doped argon atmosphere on the chemical components and temperature within a nontransferring, thermal argon plasma in comparison to an atmosphere of pure argon and air. For this purpose, the emitted radiation of the plasma was analyzed using optical emission spectroscopy. The spectra show that the Ar I lines are most prominent in all atmospheres. Compared to the air atmosphere, the plasma in the argon atmosphere exhibits a stronger H I line and an OH emission band. A slight doping of the argon atmosphere with silane (0.01 vol.%) leads to strongly pronounced Si I and H I lines and a clearly recognizable H ₂ emission band. The high amount of free electrons resulting from the stepwise ionization and dissociation of the silane molecule leads to an increase in plasma temperature from about 7,600 to 9,000 K.