An electric arc is an arc discharge that occurs between two electrodes, or an electrode and a workpiece, and which allows two or more parts to be joined by welding.
The welding arc, depending on the environment in which it occurs, is divided into several groups. It can be open, closed, and also in the environment of protective gases.
An open arc flows in the open air through the ionization of particles in the combustion area, as well as due to metal vapors of the welded parts and electrode material. The closed arc, in turn, burns under the flux layer. This allows you to change the composition of the gaseous medium in the combustion area and protect the metal of the workpieces from oxidation. In this case, the electric arc flows through metal vapors and ions of the flux additive. The arc that burns in a protective gas environment flows through the ions of this gas and vapormetal. This also helps to prevent oxidation of parts, and, consequently, to increase the reliability of the connection formed.
The electric arc differs in the type of current supplied - alternating or constant - and in the duration of burning - pulsed or stationary. In addition, the arc can have direct or reverse polarity.
According to the type of electrode used, there are non-consumable and consumable electrodes. The use of one or another electrode directly depends on the characteristics that the welding machine has. The arc that occurs when using a non-consumable electrode, as the name implies, does not deform it. When welding with a consumable electrode, the arc current melts the material and it is deposited on the original workpiece.
The arc gap can be conditionally divided into three characteristic sections: cathode, anode, and the arc shaft. In this case, the last section, i.e. the arc stem has the greatest length, however, the characteristics of the arc, as well as the possibility of its occurrence, are determined precisely by the near-electrode regions.
In general, the characteristics that an electric arc has can be combined into the following list:
1. Arc length. This refers to the total distance of the cathode and anode regions, as well as the arc shaft.
2. Arc voltage. It consists of the sum of voltage drops in each of the areas: trunk, near-cathode and near-anode. In this case, the change in voltage in the near-electrode regions is much larger than in the remainingarea.
3. Temperature. An electric arc, depending on the composition of the gaseous medium, the material of the electrodes and the current density, can develop a temperature up to 12 thousand degrees Kelvin. However, such peaks are not located over the entire plane of the electrode end face. Since even with the best processing, there are various irregularities and bumps on the material of the conductive part, due to which many discharges occur, which are perceived as one. Of course, the temperature of the arc largely depends on the environment in which it burns, as well as on the parameters of the supplied current. For example, if you increase the current value, then the temperature value will increase accordingly.
And, finally, the current-voltage characteristic or VAC. It represents the dependence of voltage on the length and magnitude of the current.
