Development of a carbon equivalent formula for underwater wet welding

Abstract

Steel structures play a vital role in the marine industry for application in ships, platforms, wind turbines, bridges, or pipelines. This leads to challenges if parts made from higher strength steels have to be repaired underwater. Underwater wet welding is the most common underwater repair method and highly prone to hydrogen-assisted cold cracking, especially in higher strength steels. A common method to access this risk in dry welding is based on the calculation of the carbon equivalent (e.g., CE or CET) representing the behavior of the parent metal based on its composition. However, these formulas were not specifically developed for wet welding conditions, and the applicability of these formulas on the special requirements of wet weldments has not been validated. In the present study, the effectiveness of existing CE formulas for underwater wet welding was evaluated. It is demonstrated that the conventional approaches designed for conventional welding under dry atmospheric conditions are hardly applicable to underwater wet welding. Based on comprehensive experimental data, a mathematical model leading to improved hardness and CE formulas dedicated to underwater wet welding was developed. The new formulas demonstrated greater efficiency in predicting hardness and carbon equivalent within the analyzed data, when compared to the existing formulas used for welding under dry atmospheric conditions.