Papers by Author: Pascal Paillard

Abstract: This work deals with the study of a new aluminum brazing process, called Galluminium. This technique, consisting in using gallium as a solder, is advantageous since it enables to braze at ambient air without flux. Indeed if the gallium coating is done mechanically, it descales the alumina layer and acts as a barrier against further reoxidation. Nevertheless, liquid gallium causes a severe aluminum embrittlement since it penetrates into the aluminum grain boundaries. We will show in this paper that this phenomenon has only a little impact on the mechanical resistance of the brazed joints since the amount of deposited gallium is enough low to avoid a severe embrittlement and the heat treatment (from 200°C to 600°C during several minutes) during brazing process dissolves gallium in the bulk.

Abstract: In the present work, TIG and A-TIG welding were compared to show the arc constriction phenomena. A 2D axial symmetric model was developed to simulate the flow behavior in the melting pool. These results were compared to experiments carried out on a stainless steel disc (304L) melted by a stationary heat source. The influence of the Marangoni effect, arc constriction and type of flux is shown. The results point to the importance of the welding parameters and the use of a flux on the characteristics of the weld beads.