W. (. Mazur, J. Francis, Commonwealth Scientific and Research Organisation, Woodville North, Australia

Summary: The effect of additions of fluorides and metals of low melting point and high vapour pressure to the wire flux on diffusible hydrogen content of weld metal deposited by flux cored arc welding was investigated.This paper reports on the effects of additions of fluorides (MnF3, CaF2, Na2SiF6, K2SiF6, Na3AlF6, and Li3AlF6) and metals (Zn, Mg, Ca, Al) to rutile flux cored wires for welding in CO2 on the diffusible hydrogen content of the deposited weld metal. It was found that the addition of ¡Ý4% Na2SiF6 can reduce the weld metal diffusible hydrogen content to 4.5 mL/100g. Additions of the other fluorides were less effective in reducing hydrogen levels. Zinc was the most effective of the metals tested, with a 5% addition to the wire flux reducing the diffusible hydrogen to 5.6 mL/100g. The combined addition of 4% Na2SiF6 and 5% Zn reduced the hydrogen content further to less than 3.2 mL/100g. The additions of fluorides and metal powders contributed to an 8-10 % increase in fume generation during welding.