The main advantage of manual metal arc (MMA) gouging is that the same power source can be used for welding, gouging, or cutting, simply by changing the type of electrode.
As in conventional MMA welding, the arc is formed between the tip of the electrode and the workpiece. MMA gouging differs because it requires special purpose electrodes with thick flux coatings to generate a strong arc force and gas stream. Unlike MMA welding where a stable weld pool must be maintained, this process forces the molten metal away from the arc zone to leave a clean cut surface.
The gouging process is characterised by the large amount of gas which is generated to eject the molten metal. However, because the arc/gas stream is not as powerful as a gas or a separate air jet, the surface of the gouge is not as smooth as an oxyfuel gouge or air carbon arc gouge.
MMA gouging is used for localised gouging operations, removal of defects for example, and where it is more convenient to switch from a welding electrode to a gouging electrode rather than use specialised equipment. Compared with alternative gouging processes, metal removal rates are low and the quality of the gouged surface is inferior.
When correctly applied, MMA gouging can produce relatively clean gouged surfaces. For general applications, welding can be carried out without the need to dress by grinding. However, when gouging stainless steel, a thin layer of higher carbon content material will be produced; this should be removed by grinding.
According to the size of gouge specified, there is a wide range of electrode diameters available. These grooving electrodes are also not just restricted to steels, the same electrode composition may be used for gouging stainless steel and non-ferrous alloys.
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