Factors affecting the stability of the welding arc

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The main factors affecting the stability of the welding arc are as follows: (1) Welder’s operating skills and the ability to automatically regulate the arc length in automatic welding. The welder’s operating skills are a crucial factor determining arc stability. During actual welding, the welder must use appropriate hand movements when manipulating the welding torch or electrode, striving to keep the arc length constant; otherwise, fluctuations in welding current or even arc extinction may occur. The angles between the welding wire and the workpiece, as well as between the welding torch and the workpiece, must be appropriate in order to achieve proper penetration, prevent welding defects, and maintain the molten pool. For automatic welding, it is required that the arc length can be adjusted automatically to keep it constant during the welding process, thereby ensuring consistency in the welding parameters. (2) Arc welding power supply ① Types of arc welding power supplies: DC arc welding power supplies and square-wave AC arc welding power supplies provide better arc stability compared to sine-wave AC arc welding power supplies. Pulse arc welding power supplies have better stability; therefore, they are typically used for welding at low currents. ②The external characteristic of the arc welding power supply should meet the requirements for stable arc combustion of the corresponding welding method. In gas metal arc welding, fine wires are generally used (with a wire diameter of no more than 3.2 mm), and a power supply with a gradually decreasing external characteristic is required; otherwise, the welding arc becomes unstable. In high-current gas metal arc welding, thicker wires may sometimes be used, and in such cases a power supply with a sharply decreasing external characteristic is necessary. ③During the short-circuit transition in the dynamic characteristics of the power supply, the CO2 welding arc burns and goes out periodically; this requires a fast rise rate of the no-load voltage from the power supply, as well as a moderate rise rate of the short-circuit current. ④The no-load voltage of arc welding power sources: The higher the no-load voltage, the easier it is to strike an arc, and the more stable the arc combustion becomes. However, excessively high no-load voltage can pose a risk to the welder’s personal safety. (3) Welding current: The greater the welding current, the higher the temperature of the arc. This leads to a stronger degree of gas ionization and thermionic emission in the arc zone, thereby making the arc more stable. (4) Arc voltage: The arc voltage should be appropriately matched to the welding current; as the welding current increases, the arc voltage should also increase. When the welding current remains constant, an excessively low arc voltage can easily lead to a short circuit; on the other hand, an excessively high arc voltage causes the arc to oscillate violently, thereby disrupting the stability of the welding arc. (5) Workpiece surface condition, gas flow, and magnetic deflection: If the workpiece surface is not clean, with oil, rust, moisture, etc. present, arc initiation and arc stability are compromised. Similarly, an unstable protective gas flow or magnetic deflection also leads to unstable arcs.