An electric arc is an arc discharge that occurs between two electrodes or an electrode and a workpiece and which allows the connection of two or more parts 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 the vapor of the metal of the welded parts and the material of the electrodes. A closed arc, in turn, burns under a layer of flux. 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, an electric arc flows through metal vapors and flux additive ions. An arc that burns in a protective gas environment flows through the ions of this gas and metal vapor. It also helps to prevent oxidation of parts, and, therefore, to increase the reliability of the formed compounds.
The electric arc differs by the type of input current - alternating or constant - and by the duration of burning - pulsed or stationary. In addition, the arc may have a direct or reverse polarity.
According to the type of electrode used, non-melting and melting ones are distinguished. 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 fused to the original workpiece.
The arc gap can be divided into three characteristic sections: cathode, anode, and also the trunk of the arc. Moreover, the last section, i.e. the arc barrel has the longest 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. The length of the arc. This refers to the total distance of the near-cathode and anode regions, as well as the arc shaft.
2. Arc voltage. It consists of the sum of the voltage drops in each of the areas: trunk, cathode and anode. In this case, the voltage change in the near-electrode regions is much larger than in the remaining region.
3. Temperature. An electric arc, depending on the composition of the gaseous medium, the material of the electrodes and the current density, can develop temperatures up to 12 thousand degrees Kelvin. However, such peaks are not located along the entire plane of the electrode end. Since even with the best processing on the material of the conductive part, there are various irregularities and tubercles, due to which there are many discharges that 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 input current. For example, if you increase the current value, then, accordingly, the temperature value also increases.
And finally, the current-voltage characteristic or the current-voltage characteristic. Represents the dependence of voltage on the length and magnitude of the current.