Análise do paradoxo da polaridade na soldagem subaquática com eletrodos revestidos oxi-rutílicos

Abstract

In atmospheric welding with consumable electrodes, using reverse polarity results in greater penetration of the weld bead, while using straight polarity leads to a higher melting rate. However, underwater welding works differently due to the hydrostatic pressure that affects the arc's structure in the stick electrode process. This pressure redistributes the energy in the sum of the voltage fall in the anode and cathode, as well as in the voltage fall in the arc column. As a result, the power distribution in the arc regions changes, causing a loss of melting efficiency in the base metal for reverse polarity. This results in a shallow weld bead penetration. Additionally, straight polarity experiences a reduction in melting rate, leading to shorter arc lengths and reduced welding speed. Consequently, the fusion efficiency remains almost unchanged with increasing depth. This thesis identifies the phenomena and mechanisms responsible for the polarity paradox in underwater wet welding with stick electrodes. It also offers a descriptive model that clarifies misconceptions surrounding the transfer of mass and energy in this underwater operation.