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Type of resistance Welding
spot welding
Seam welding
Projection welding
All of the above
All of the above
Resistance welding is a thermo-electric process where coalescence is produced by the heat obtained from the resistance offered by the workpieces to the flow of electric current. Spot, seam, and projection welding are all primary variations of this process based on the geometry of the electrodes and the contact surface.
Resistance welding is a thermo-electric process where coalescence is produced by the heat obtained from the resistance offered by the workpieces to the flow of electric current. Spot, seam, and projection welding are all primary variations of this process based on the geometry of the electrodes and the contact surface.
H=I2Rt тАФ Heat generated in Joules
I=ZVтАЛ тАФ Welding current calculation
The principle is based on Joule's law of heating, where heat H=I2Rt is generated at the interface of the metals to be joined. The current flows through the material under high pressure from the electrodes, causing the metal to reach a plastic or molten state at the point of contact, followed by forging pressure to form a weld nugget.
Resistance welding does not require filler metals.
The process is highly automated and suitable for mass production in the automotive industry.
Electrical power is supplied via a step-down transformer to provide low voltage and high current.
Materials with low electrical resistance require higher welding currents.
High speed and efficiency
Suitable for high-volume production
No external filler material required
High initial equipment cost
Difficult to weld thick sections
Limited to lap joints for most types
Automotive car body manufacturing
Sheet metal fabrication
Container and radiator manufacturing
| Feature | Spot Welding | Seam Welding |
|---|---|---|
Contact Geometry | Point contact | Roller/Wheel contact |
Spot welding joins two sheets at discrete points.
Seam welding produces a continuous leak-proof joint using roller electrodes.
Projection welding uses embossed projections to concentrate current for multiple simultaneous welds.
D is correct тАФ Spot, Seam, and Projection welding are all distinct sub-types of the resistance welding process.
In resistance welding, remember that heat is inversely proportional to resistance; therefore, metals with higher electrical conductivity (like Copper) are more difficult to weld compared to Steel.