Determination of momentum as a mean of quantifying the mechanical energy delivered by droplets during MIG/MAG welding

Federal University of Uberlândia, Mechanical Engineering Faculty, Laboratory for Welding Process Development, P.O. Box 38400-902, Uberlândia, MG, Brazil

Corresponding author: ascotti@ufu.br

Received: 30 May 2008
Revised: 3 September 2008
Accepted: 22 October 2008
Published online: 16 January 2009

Abstract

The objective of this work was to propose and assess, under the light of modern techniques for arc visualization and welding parameter monitoring, a parameter that would quantify properly the effect of the droplets reaching the pool over the bead penetration during MIG/MAG welding (GMAW). High-speed filming shadowgraphy, synchronized with the electrical signals, was used. Dedicated computational programs were employed to measure arc lengths and size, frequency, acceleration and speed of the droplets. Calibration of the system by employing metallic spheres was used to guaranty the performance of the image recording and measurement programs. Statistics were employed for sampling size determination. A non-common approach to correlate Momentum to bead geometry is propose and discussed. The methodology was assessed through MIG/MAG bead-on-plate welds shielded with an Ar+5%O₂ blend, at three levels of currents and arc lengths. It was concluded that the proposed parameter denominated in this paper as “Effective Momentum” is the one which better represents the action of the droplets over bead formation.