Research on the arc stability of dry hyperbaric GMAW from the perspective of arc energy and electrical conductivity

Abstract

As the environmental pressure increases, the arc plasma of dry hyperbaric gas metal arc welding (DH-GMAW) contracts. This phenomenon leads to decreased arc stability or even arc extinguishment, which severely affects the welding quality. In essence, the dynamic behaviour of arc plasma is influenced by its electrical conductivity. Furthermore, changes in electrical conductivity depend on changes in arc energy transport. To study changes in arc energy transport, the energy dissipated from the arc to the external environment was measured. The arc voltage drop was measured, and the arc conductivity was calculated. A water heat exchange system was used to collect the energy dissipated from the arc to the external environment. A double passive tungsten probe was used to measure the voltage drop of the arc column. Comparative research on arc energy dissipation and conductivity under different environmental pressures was conducted to analyse their effects on arc stability. The experimental results show that as the environmental pressure increases, the arc energy dissipation increases, and the arc column voltage drop decreases. The electrical conductivity decreases with increasing environmental pressure, indicating that the internal energy of the arc decreases. The conductivity can be improved by increasing the welding current. However, this improvement gradually diminishes with increasing pressure. The energy dissipation near the cathode increases with pressure, leading to further contraction of the arc. The reverse plasma jet force increases with pressure. This phenomenon increases instability in the welding process. Clearly, changes in arc energy transport and conductivity have crucial effects on arc stability. In conclusion, increasing the arc energy input or reducing the arc energy dissipation is beneficial for suppressing arc contraction and improving arc stability.