In welding, gouging has been a requirement for many years in several industries and applications, and is one method to explore. Especially in maintenance and repair, the ability to gouge or groove metal is critical and deserves full consideration. Gouging electrodes are made of artificial graphite and have a pure copper coating. The gouging electrodes are available in a variety of shapes and diameters to meet the various applications.

Gouging is commenced by striking the electrode tip on to the workpiece surface to initiate the arc. Unlike Manual Metal Arc (MMA) welding the electrode tip is not withdrawn to establish arc length. Molten metal directly under the electrode tip (arc) is immediately blown away by the air stream.

Table of Contents

• Introduction
• Features of Gouging Electrodes
• Methods of Gouging

        Plasma gouging

       Air Carbon-Arc Gouging

• Types of Carbon Electrodes
• Frequently Asked Questions about Gouging Electrodes
• Conclusion

Gouging electrodes are made of carbon and have a copper coating. Gouging carbon rods are used for metal removal at fast rates with low power consumption. It is generally used to remove welding defects, excess welds and foundry risers from cast products.

Features of Gouging electrode

• Pure copper coated – good electric conductivity.
• High density (made of artificial graphite) –leads to high metal removal rate.
• Less consumption of electrodes – cost reduction.
• Constant quality – for a safe process.
• High metal removal rate – effective process.
• Extreme low burn back rate.

Methods of Gouging 

Two of the most common methods of gouging are:

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.

Applications of Gouging

Plasma gouging was developed as a tool for weld removal and weld preparation. Back gouging was used to remove metal from the reverse side of arc-welded joints to eliminate defects and improve strength. Weld defects such as cracks, porosity, and lack of fusion could be gouged out using a plasma torch and then repaired with a new, sound weld.

Today plasma arc gouging has wider industrial applications, from shipbuilding and maintenance, to heavy equipment manufacturing and repair, to manufacturing of truck bodies, tanks, and steel structures. Plasma gouging removes strong backs, lifting lugs, temporary brackets, tack welds, and rivets. It is also suitable for demolition or salvage operations to disassemble welded structures. In foundries, it removes excess material from castings. Anywhere surplus metal, excess weld, or defects need to be removed, plasma gouging can be used.

Types of Electrodes

There are three types of carbon electrodes:

• AC coated electrodes (for use with AC power sources),
• DC plain electrodes and
• DC copper-coated electrodes.

The latter is most widely used because of their comparatively long electrode life, stable arc characteristics and groove uniformity.

This process is the best alternative to traditional gouging more particularly when precision and safety are priorities. With a removal capability of up to 8 kg/h, Plasma gouging improves operating conditions by reducing noise and fumes.

Using the same process as plasma cutting, it enables the removal of metal efficiently, precisely and cleanly.

Efficiency

The plasma arc produces a very accurate groove.

Suitable for application on all ferrous and non-ferrous materials.

• Easy to use.
• Gouge all conductive materials.
• No carbon filler.
• Heated area reduced.
• Instantaneously wieldable without preparing the edges.
• Less noise and fumes.
• Professional finishing.
• Higher consumable life

Frequently Asked Questions about Gouging Electrodes

Q1- What are gouging electrodes made of?

 Gouging electrodes are made of carbon and have a copper coating.

Q2- What are the uses of gouging carbon rods?

 It is used to remove welding defects, excess welds and foundry risers from cast products

Q3- What is the gouging process?

 The gouging process is characterized by the large amount of gas which is generated to eject the molten metal.

Q4- How does arc gouging work?

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Conclusion

The importance of gouging in the field of welding cannot be overemphasized. These gouging electrodes are made of carbon and have a copper coating. The gouging carbon rods play a major role in metal removal at fast rates with low power consumption. It is generally used to remove welding defects, excess welds and foundry risers from cast products.

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