Melt flow in deep penetration welding Available to Purchase

The roles of melt flow in determining the operating characteristics of deep penetration welding are described. The flow refers to the flow of the layer of molten metal lining the keyhole wall. As the workpiece moves in a direction transverse to the laser axis, the heat of the laser first melts a layer of the metal. Subsequent vaporization of a fraction of this metal creates a recoil pressure in the melt, propelling the molten metal around the hole, which eventually solidifies downstream of the keyhole. This mechanism requires only a fraction of the power, as compared to the power which would have been required if the keyhole had been formed entirely by evaporation. While the present theory is not intended to address the issue of plasma enhancement in keyhole formation, it is important to note that the presence of the plasma is not a necessary feature of the mechanism invoked. The theory clearly explains why keyhole formation is considerably easier in reduced pressures, and why high optical quality is of the primary importance.