Prediction of hydrogen cracking in the wet welding of structural steels with ferritic stick electrodes down to 20 m

Abstract

Hydrogen cracking (cold cracking), both in the heat-affected zone (HAZ) and in weld metal (WM) is one of the main factors responsible for losses in ductility and toughness in wet welds. These losses make it difficult to comply with structural quality requirements for underwater wet welding. This work presents and discusses experimental results focusing on such cracks in ferritic weldments. The welding tests performed in the laboratory used a mechanized system operating at pressures corresponding to water depths from 0.3 m to 20 m. The relationships between diffusible hydrogen, chemical composition, hardness, and cracking incidences were assessed for both the weld metal and heat-affected zone. Boundary conditions for the occurrence of cracks are suggested. The influence of welding depth on cracking occurrence was also considered. The main contribution of this work is the proposition of limits on diffusible hydrogen, hardness, carbon content, carbon equivalent, and critical metal parameter (Pcm) to avoid hydrogen cracks both in the weld metal and in the heat-affected zone. Emphasis is placed on the estimation of conditions to avoid hydrogen cracking in the welding of structural ship steels. Suggestions for future studies are presented.

Keywords

• Hydrogen cracking
• Underwater welding
• Wet welding
• SMAW
• Diffusible hydrogen
• Oxyrutile electrodes