Methods of Gouging

Plasma gouging

Air carbon-arc gouging electrode.

Plasma gouging is a variation of plasma cutting, in which the arc is "defocused" slightly by increasing the whole size in the constricting orifice. A cutting arc is directed downward through the metal to blow the molten metal down and out through the kerf, forcing the two pieces of metal to separate. In plasma gouging, the torch is inclined at an angle to the work piece, and the arc plows out a groove on the metal surface and blows the molten metal off to the side. A more intense cutting arc causes a groove too deep and narrow for most applications, so the defocused arc is used for gouging.

The plasma cutting process was invented in 1954 at the Tonawanda Laboratory of the Linde Division of union   Carbide. A young scientist, Robert Gage, discovered that by forcing a gas tungsten arc through a small orifice in a process similar to focusing a beam of light through a lens, the temperature and intensity of the arc could be increased. By passing a fairly high gas flow through this focused arc, it could cut metal.

Air Carbon-Arc Gouging

The main goal of air arc gouging is to remove defective or old welds to repair or dismantle equipment. Unlike oxy-fuel cutting, air arc gouging avoids the need for oxidation of the metal to cut. The rate of metal removal depends on the efficiency of the air jet in removing molten metal and the melting rate. The process of air carbon-arc gouging is generated between the tip of a carbon electrode and the work piece. The metal becomes molten and a high velocity air streams down the electrode to blow it away and thus leaves a clean groove. It is a simple process to apply, has a high metal removal rate, gouge profile and it can be closely controlled.

However, there are disadvantages: the air jet causes the molten metal to be ejected over quite a large distance and, because of high currents (up to 2000A) and high air pressures (80 to 100 psi), it can be very noisy.

This type of gouging can be applied to a wide range of metals. DC (electrode positive) is normally preferred for steel and stainless steel, but AC is more effective for cast iron, copper and nickel alloys. Typical applications include back gouging, removal of surface and internal defects, removal of excess weld metal and preparation of bevel edges for welding.