Average Heat Quantity of Molten Droplets in Narrow-gap MAG Welding

Effect of Groove Width

Abstract

In previous papers, the authors have made it clear that wire melting rates are'not affected by groove widths in electrode positive narrow-gap MAG wleding but that, on the other hand, in the case of electrode negative, the wire melting rate decreases with decreasing the groove width.
It was proposed that, some change in the electric input energy with changing groove width was the cause of this phenomenon in the case cf electrode negative MAG welding.
This paper attempts to verify the above proposition by measuring both the heat quantity of the molten droplets. and the wire melting rates at different groove widths and calculating the equivalent wire melting voltage.
The experimental results were as follows;
With the electrode negative, the arc ignited between the conical surface of the wire tip and the groove side walls, and both the heat quantity.of molten droplets and the wire melting rate decreased with decreasing the groove width. Moreover, the calculated equivalent wire melting voltage also decreased with decreasing groove width.
On the other hand, with the electrode positive, the heat quantity of molten droplets and the wire melting rate were both not affected by the groove width.
It was concluded from the experimental results that, in electrode negative narrow-gap MAG welding, the phenomenon of the decrease of wire melting rate with decreasing groove width, is attributable to a decrease in the equivalent wire melting voltage.