Spot and seam welding basics: In electric resistance welding (ERW), what is the typical voltage range required at the electrodes to generate the necessary heating at the faying surfaces?

Introduction / Context:
Electric resistance welding relies on the heat generated by I^2 * R at the interface of sheets under force. Correct electrical parameters ensure a small, controlled weld nugget without excessive expulsion or electrode damage.

Given Data / Assumptions:

• Power from a line supply is stepped down by a transformer near the gun.
• High current, very low voltage is applied at the electrodes.
• Process examples: spot, projection, and seam welding.

Concept / Approach:
Transformers in ERW deliver enormous currents (often several kiloamperes to tens of kiloamperes) at very low voltage, typically a few volts. The low voltage increases safety and focuses heating at high-resistance contact points. Typical electrode voltage is about 1–5 V, depending on material, thickness, and contact resistance.

Step-by-Step Solution:
Recall heat input relation: Q ~ I^2 * R * t; ERW emphasises high I and contact R.Know transformer function: step-down voltage to a few volts, step-up current massively.Match typical practice: 1–5 V at electrodes for most sheet gauges.Select “1 to 5 volts”.

Verification / Alternative check:
Equipment datasheets list secondary open-circuit voltages typically under 10 V, with loaded voltages in the 1–5 V band.

Why Other Options Are Wrong:
Higher voltages (6–10 V and above) are atypical and risk arcing; 50–100 V or mains-level values are not used at electrodes.

Common Pitfalls:
Confusing primary line voltage with secondary electrode voltage; overlooking contact cleanliness and force that influence effective resistance and heat generation.

Final Answer:
1 to 5 volts