Abstract
Automatic gouging by air carbon-arc method has been widely used as a step in welding work and in consequence the demand for all-position operation is mounting. The automatic gouging devices are classified into two types from the standpoint of electrode feed speed control: one type utilizing arc voltage for the control purpose and the other utilizing constant feed rate. The latter is one recently developed and is found appropriate for operating in all positions because of its light weight and easy operation.
In this report, gouging in flat position of steel plate was tried, using the above constant electrode feed type device as the first step to application of this method to circumferential pipe welds. Then the effects of various gouging conditions (characteristics of electric power source, gouging speed, electrode feed speed, electrode diameter and shape of cross section, and torch angle) on arc voltage, gouging current, arc stability (continuity), heat input, groove shape, amount of removed metal and melting efficiency were studied.
The main results are as follows:
1) The stability of arc largely depends on the characteristics of electric power source and the amount of fed electrode per unit gouge length (Wr).
2) The heat input (H) and removed metal per unit gouge length (Wm), ratio Wm/H and that of groove depth to groove width (d/w), an index of groove shape, are affected by gouging speed (Vg) and Wr. The ratio d/w is also affected by torch angle and the shape of electrode section.
3) If Vr and Vg are varied under constant ratio Vr/Vg as in practical use, Wm and melting efficiency (η, ratio of heat content of molten metal to heat input) are held almost constant except for smaller values of Vg (and Vr), Vr being the feed speed of electrode.
4) Linear regression analyses are made of data obtained under constant Vg, showing that there is close relation between Wr and Wm as well as between ratio d/w and η.
