Shanu

■ 31.8 ARC CUTTING

Virtually all metals can be cut by some form of electric arc. In these processes the material is

melted by the intense heat of the arc and then permitted, or forced, to flow away from

the region of the slit or notch (kerf). Most of the techniques are simply adaptations of

the arc-welding procedures.

Each has its inherent characteristics and capabilities, including tolerance, thickness capability, kerf width, edge squareness, size of the heat-affected zone, and cost.

Selection depends upon factors such as tolerance requirements, the subsequent processes that will be performed on the cut part, and the end use of the product.

CARBON ARC AND SHIELDED METAL ARC CUTTING

The carbon arc cutting (CAC) and shielded metal arc cutting (SMAC) methods use the

arc from a carbon or shielded metal arc electrode to melt the metal,which is then removed

from the cut by gravity or the force of the arc itself.These processes are generally limited

to small shops, garages, and homes, where there is limited investment in equipment.

AIR CARBON ARC CUTTING

In air carbon arc cutting, the arc is again maintained between a carbon electrode and the

workpiece, but high-velocity jets of air are directed at the molten metal from holes in the

electrode holder.While there is some oxidation, the primary function of the air is to

blow the molten material from the cut.Air carbon arc cutting is particularly effective for

cutting cast iron and preparing steel plates for welding. Speeds up to 0.6 m/min are possible,

but the process is quite noisy, and hot metal particles tend to be blown over a substantial

area.

OXYGEN ARC CUTTING

In oxygen arc cutting (AOC), an electric arc and a stream of oxygen are combined to

make the cut.The electrode is a coated ferrous-metal tube.The coated metal serves to

establish a stable arc, while oxygen flows through the bore and is directed on the area of

incandescence.With easily oxidized metals, such as steel, the arc...