Factors Affecting Hydrogen Assisted Cracking in Wet Welding of Ferritic Steels with Covered Electrodes

Hydrogen assisted Cracking (cold cracking) in the heat affected zone and weld metal is one of the most important factors responsible for ductility and toughness losses in wet welds. Consequently, full structural quality in underwater wet welding repairs have been hardly achieved. Recent experimental results and also related data collected in the literature focusing the occurrence of this type of cracks in ferritic weldments are presented and discussed. Influences of the nature of electrodes coatings on the cracking susceptibility are quantitatively presented. Welding trials were performed in laboratory using a mechanized wet welding system operating at 0,5 m, 10 m and 20 m simulated water depth. The relationship between diffusible hydrogen content and cracking incidence was assessed for both weld metal and heat affected zone using quantitative metallographic techniques. Weldability tests results varying diffusible hydrogen and carbon content allowed to establish boundary conditions for the occurrence of cold cracks. Oxidizing type electrodes presented the best conditions to mitigate the cold cracking phenomenon. The influence of welding pressure was also assessed.  Increasing pressure resulted in the decrease of cracks incidence. The responsible mechanisms for cracking seem to be influenced by the decrease in the diffusible hydrogen and increasing porosity with increasing pressure. Suggestions for future developments to avoid hydrogen cracks in wet welds are presented.