Self-Gathering Effect of the Hydrogen Diffusion in Welding Induced by the Solid-State Phase Transformation

Area of Science:

• Materials Science
• Metallurgical Engineering
• Computational Mechanics

Background:

• Hydrogen embrittlement is a critical concern in welded structures.
• Understanding hydrogen diffusion dynamics is crucial for preventing weld failures.
• Previous models often simplified the complex interplay of thermal, mechanical, and diffusion processes.

Purpose of the Study:

• To investigate hydrogen diffusion during welding using advanced computational methods.
• To identify and characterize the self-gathering effect of hydrogen.
• To analyze the impact of this effect on hydrogen distribution and cold cracking susceptibility.

Main Methods:

• Utilized thermal-mechanical-hydrogen diffusion sequential coupled procedures.
• Employed the finite element method for numerical simulations.
• Analyzed hydrogen concentration changes during single and multi-pass welding.

Main Results:

• Discovered a self-gathering effect of hydrogen induced by solid-state phase transformation.
• Observed hydrogen accumulation in weld metal exceeding initial molten pool concentrations.
• Demonstrated redistribution of hydrogen in the heat-affected zone.
• Identified inter-pass hydrogen accumulation in multi-pass welding, heightening cold cracking sensitivity.

Conclusions:

• The self-gathering effect significantly impacts hydrogen distribution in welds.
• Multi-pass welding exacerbates hydrogen accumulation and cold cracking risks.
• Control strategies are necessary to mitigate hydrogen accumulation.
• Welding stress evolution has a minor influence on hydrogen diffusion.