Resistance welding — typical electrode pressure range In electric resistance welding (e.g., spot welding) of steel sheets, what is a typical range of applied electrode pressure required to form a sound nugget?

Introduction / Context:
In resistance spot welding, quality depends on three primary parameters: current, time, and pressure (force). Proper electrode pressure ensures intimate contact, controls current density, and forges the molten nugget during solidification.

Given Data / Assumptions:

• Mild steel or similar sheet metals of typical automotive thicknesses.
• Standard domed copper alloy electrodes.
• Industrial equipment with pneumatic or servo guns.

Concept / Approach:
Electrode pressure must be high enough to break surface films, maintain contact, and contain the molten pool, but not so high that it expels molten metal or starves the joint of heat. For common gauges, forces correspond to pressures around 5 to 10 MPa when referenced to electrode face area. Lower than 5 MPa risks arcing and expulsion; much higher pressures are reserved for special cases or thick stacks.

Step-by-Step Solution:
Relate typical electrode force to face area to estimate pressure.Consult standard practice: automotive schedules cluster around 5–10 MPa.Select “5 to 10 MPa”.

Verification / Alternative check:
Welding procedure specifications and textbooks tabulate recommended forces that, when converted to pressure, fall within this range for usual electrode diameters.

Why Other Options Are Wrong:

• 1 to 5 MPa: often insufficient; unstable contact and splash risk.
• 10 to 25 MPa or 25 to 55 MPa: too high for standard thin sheets; may cause indentation and expulsion.
• 0.1 to 0.5 MPa: far too low to maintain contact.

Common Pitfalls:
Confusing force (N) with pressure (MPa). Always normalise by electrode face area when comparing setups.

Final Answer:
5 to 10 MPa