Bubble Evolution Behaviors Induced by CaO–Al2O3–SiO2–CaF2 Fluxes Subjected to High Heat Input Submerged Arc Welding

Bubble evolution behaviors have been thoroughly documented from the solidified slags detached from EH36 shipbuilding steel weld metals processed by CaO–Al2O3–SiO2–CaF2 fluxes. As the CaF2 content decreases, bubble retention tendency attenuates, which is largely rendered by the disappearance of fluorite and cuspidine and the formation capacity of amorphous phases. Thermodynamic calculations show that bubbles are mostly induced by the synergistic effect of decreased amount of CaF2(g) and increased amount of SiO(g).