Determination of the Momentum of Droplets Impinging on the Pool during Aluminium GMAW (Determinação do Momentum das Gotas Impingindo sobre a Poça durante Soldagem GMAW

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. Key-words: Physics of Welding Arc; momentum; metal transfer; aluminium Resumo: O objetivo deste trabalho foi o de levantar as características cinemáticas e dinâmicas das gotas em transferência durante a soldagem de alumínio pelo processo GMAW e quantificar o efeito parcial do momentum sobre a formação do cordão. Foi inicialmente atribuído que a melhor maneira de se quantificar este efeito seria através do fluxo de massa das gotas alcançando a poça de fusão, parâmetros calculando e denominado aqui como Momentum Efetivo. Foram realizadas soldagens de simples deposição sobre chapa