Suppression of humping bead defects in high-speed triple-wire gas indirect arc welding through compensation gas

Abstract

Triple-wire gas indirect arc welding (TW-GIA) has significant advantages of high deposition rate and low heat input. However, the humping bead defects in high-speed TW-GIA welding limits the improvement of welding speed. In this article, the feasibility of compensation gas to suppress the humping bead in TW-GIA was explored, and the influence on molten pool flow and arc stability was revealed. The results show that the compensation gas with jet angle of 90 °has the ability to suppress the humping bead and reduces the oxygen content of the weld. When the compensation gas flow rate is less than 30 L/min, the decrease of arc pressure leads to the decrease of reverse flow velocity of liquid metal. And the vertical downward impact force caused by compensation gas can directly inhibit the uplift of the liquid metal, which is beneficial to suppress the humping bead. In addition, the compensation gas carry in high ionization energy gas, which reduces the welding current and increases the range of conductive channel. The low gas flow rate with the jet angle of 90° has little effect on the arc stability, but the flow rate exceeding 30 L/min significantly increases the degree of arc disorder.