Tweco Tri-Arc Serie - Manual (Page 5)

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SECTION 1: INTRODUCTION
1.01 Air Carbon-Arc Cutting/Gouging
The air carbon-arc process (CAC-A) removes metal physically, not chemically as in
oxy-fuel cutting (OFC). Gouging or cutting occurs when the intense heat of the arc
between the carbon electrode and the workpiece melts part of the workpiece. Simulta-
neously, air passes through the arc quickly enough to blow the molten material away.
The air carbon-arc process does not require oxidation to maintain the cut, so it can
gouge or cut metals that the OFC process cannot. Most common metals (e.g., carbon
steel, stainless steel, many copper alloys and cast irons) can be cut using the air
carbon-arc process. The metal removal rate depends on the melting rate and how
efficiently the air jet removes molten metal. In the process, the air must lift the molten
metal clear of the arc before the metal solidifies.
1.02 History
Air carbon-arc gouging began in the 1940's, evolving from the existing carbon-arc cut-
ting process. Myron Stepath, a welding engineer, developed air carbon-arc gouging to
remove several hundred feet of flat, cracked, stainless steel weld.
Previously, carbon-arc cutting removed overhead and vertical defective welds and rivet
heads. The carbon-arc melted the metal, then gravity moved the molten metal away.
Stepath reasoned that an air jet could provide the force to remove metal lying flat. So
he tried a direct-current, electrode-negative carbon-arc with a second operator direct-
ing an air blast via air nozzle at the molten pool. However, this attempt was unsuc-
cessful because the arc was less stable than a carbon-welding arc. So, Stepath tried a
direct-current, electrode-positive arc, and the result was air carbon-arc gouging.
In 1948, Myron Stepath introduced the first air carbon-arc torch to the welding indus-
try. In 1949, Stepath and two associates founded the Arcair ® Company.
Two operators were no longer needed. The compressed air now passed through the
torch and exited beneath the electrode. This new tool saved time on weld backgouging,
crack removal, and weld defect repair on carbon, alloy, and stainless steel. Previously,
these tasks were performed by grinding or chipping.
Today, the basic principle remains the same, but with improved equipment and an
expanded number of applications.