Twin-carbon arc welding is carried out with arc excitation between two carbon electrodes in a special holder. Two electrodes, after touching, are divorced, while the electric arc lights up and is maintained.
The size of the arc depends on the distance between the electrodes, the diameter of the electrodes and the welding current. The heat generated can be controlled by changing the size of the arc or the distance between the arc and the workpiece. After the arc has started, welding can be carried out in the same way as in the TIG process.
Dual carbon arc welding is recommended for AC power. With direct current, the positive electrode will degrade faster than the negative electrode, because two-thirds of the total heat is generated at the positive pole. This will lead to arc instability and require frequent electrode changes. When welding with alternating current, both electrodes will work the same way.
The amount of arc current required for welding depends on the diameters of both electrodes and the thickness of the workpieces. For example, with a diameter of 8 mm, a current of about 65 amperes is needed to weld mild steel sheet with a thickness of 3.5 mm and 80 amperes for welding a sheet with a thickness of 6 mm.
Double carbon arc welding has the advantage that the arc can be moved to any point on the workpiece without extinguishing it. In addition, the blanks are not part of the electrical circuit. With double carbon arc welding, metal loss is reduced - less fumes and spatter are formed.
