A Predictive Electrochemical Model for Weld Metal Hydrogen Pickup in Underwater Wet Welding Academics Research About
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A Predictive Electrochemical Model for Weld Metal Hydrogen Pickup in Underwater Wet Welding

               Introduction
  • Underwater wet welds pick up hydrogen from the surrounding water.
  • Hydrogen is detrimental to weld metal integrity because of HAZ cracking and weld metal microfissuring.
  • Methods to minimize hydrogen pickup include flux composition modification and hydrogen gattering.
  • Oxidizing fluxes with adjusted CaO/SiO2 (Basicity) ratios used in this work to reduce hydrogen pickup.
  • Electrochemical reactions determine hydrogen pickup in underwater wet welds.

Optimized fluxes minimized wet weld hydrogen pickup, lowering its level to an astonishing
13 ml/100g

Slag hydrogen content reflected similar behavior of hydrogen reduction with FeO addition to the flux

Effect of DCEP & DCEN (polarity) on hydrogen pickup indicating the influence of electrochemical reactions

Direct correlation between weld metal hydrogen and slag hydrogen content

Electrochemical model of hydrogen pickup as a function of partial pressure of water vapor and activity of FeO n the slag

               Conclusions
  • Both weld metal hydrogen content and slag hydrogen content were dependent on the phases present in the slag.
  • Mössbauer spectroscopy indicated that Fe+2 was the only valence state present in the slag for the entire range of hematite additions in the electrode coating.
  • Minimum hydrogen (13.2 ml/100g) was obtained with the presence of fayalite (2FeO.SiO2) in the slag.
  • Lower weld metal hydrogen contents were obtained using DCEN (CC-) in wet welding.
  • Hydrogen was transported through the slag in the form of OH- ion and the amount of OH- ions present in the slag determined the weld metal hydrogen content. (Not demonstrated in the 5 figures presented here)


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Last modified: March 31, 2000