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Have to be used in AC welding Is
Coated electrode
Uncoated electrode
Both
Any
Coated electrode
In AC welding, a coated electrode is essential because the alternating current passes through zero twice per cycle, which can cause the arc to extinguish. The coating contains ionizing chemicals that stabilize the arc during the zero-crossings, ensuring the welding process remains continuous and stable.
In AC welding, a coated electrode is essential because the alternating current passes through zero twice per cycle, which can cause the arc to extinguish. The coating contains ionizing chemicals that stabilize the arc during the zero-crossings, ensuring the welding process remains continuous and stable.
VarcтАЛ=EiтАЛ+IaтАЛRaтАЛ
StabilityтИЭArc┬аGapIonization┬аPotentialтАЛ
The coating (flux) on the electrode performs several vital roles: it provides a gas shield to protect the molten metal from atmospheric contamination, adds slag-forming ingredients to protect the bead while cooling, and introduces low-ionization potential elements like potassium or sodium. These elements maintain the electrical conductivity of the arc gap even when the AC voltage momentarily drops to zero, preventing the arc from snapping out.
AC welding requires arc stabilizers to overcome zero-current periods.
Flux coatings are formulated with high-electron-emissivity compounds.
Uncoated electrodes (bare wire) are generally unsuitable for AC due to arc instability.
The welding transformer must provide a higher open-circuit voltage compared to DC welding.
Reduces magnetic blow effect compared to DC welding.
More economical equipment design for AC transformation.
Lower arc stability compared to DC welding.
Increased requirement for high-quality electrode coatings.
Heavy structural steel fabrication.
General maintenance and repair welding.
Welding thick ferromagnetic sections.
| Feature | Coated Electrode | Uncoated Electrode |
|---|---|---|
Arc Stability | High (due to Flux) | Poor/Unstable |
The arc length in AC welding must be kept short to assist in reignition after the current zero-crossing.
Option B is incorrect because uncoated electrodes lack the chemical stabilizers required to sustain an arc across the zero-voltage points of an AC supply.
A is correct тАФ Coated electrodes are mandatory for AC welding because their flux contains ionizing materials that sustain the arc through zero-current crossings.
Always remember that in electrical heating and welding, 'AC' usually implies the need for stabilizing agents (flux/coating) to compensate for the cyclic nature of the power frequency.