Cause of Porosity in Weld Metal by Moistened Low-Hydrogen Type Electrode

Abstract

This study aims to clarify the reason why a low-hydrogen lime type electrode is sensitive to hydrogen porosity of weld metal in spite of its low diffusible hydrogen content. Metal transfer, viscosity of molten slag, and the difference of features of bubble through molten slag are studied by various kinds of electrode fluxes dried or moistened.
The experimental results were as follows:
1) From the lower viscosity of molten slag, porous solidified slag and quietly wavy molten pool by low-hydrogen electrode, it was deduced that saturated gas in molten metal might consistently generate to form bubbles and easily escape through covered molten slag before and during solidification period of molten metal.
2) Saturated gas in molten metal with other types of electrodes seemed to escape hardly through molten slag with higher viscosity. And gas under viscous molten slag formed larger blisters on slag surface just after solidification of molten metal and explosively escaped after completion of so.idification of molten metal.