Determination of the Momentum of Droplets Impinging on the Pool during Aluminium GMAW

摘要

The purpose of this work was to raise the kinematics and dynamics characteristics of the droplets under transference during aluminium GMA welding and quantify the partial effect of the momentum on the weld bead formation. It is initially claimed that a better way of quantifying this effect would be through the mass flow rate of the droplets reaching the weld pool; calculated parameter denominated here as Effective Momentum. Bead-on-plate GMAW shielded with Ar, was carried out using an aluminium alloy wire. Three levels of current and two levels of arc length were employed in the experimental design. High-speed filming shadowgraphy, synchronized with the electrical signals, was used as measuring tool. Dedicated computational programs were employed to quantify arc lengths and size, frequency, acceleration and speed of the droplets. It was confirmed that in spite of the low values of the Effective Momentum for aluminium GMAW the momentum is one of the governing factor in developing bead penetration. The interaction between Effective Momentum and welding current and its effect on the aluminium GMAW bead geometry is discussed.