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Arc cutting and gauging methods can be classified mainly in two
groups:
Cutting and Gouging with Carbon Electrodes (Arc-Air Method)
Copper-coated graphite electrodes are used with DC (+) to produce
the arc. compressed air blows the molten metal away. This method
is mostly used for cutting or piercing of scrap and removing faulty
welds. In small jobs were compressed air is not available, cutting
is
still possible with the carbon electrode but the cut rate is slow,
the
cut surface is rough and there is a carbon absorption in the heat
affected zone. Cutting and gauging with Coated Electrodes
Specially produced acidic, rutile, cellulosic and iron powder electrodes
4 to 6 mm in diameter produce a cutting or gauging arc with a current
intensity of 60-70 A/mm. Electrode holders should be specially
designed to withstand such high currents. The arc produced by these
electrodes releases a high pressure gas stream from the fast burning
of the material in the coating, this gas stream removes the molten
metal. The cut edges are rough and need scale removal and machining
afterwards. Cutting with the Oxy-arc Method This method is similar
to oxygen cutting but here the preheating flame is replaced with
the arc that forms between the electrodes and the work piece. After
the arc formation, compressed oxygen that goes through the tabular
graphite electrode starts combustion, thus cutting the piece. Today,
this method is employed in underwater cutting processes.
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