ANS:D - Resistance welding

Resistance welding is a welding process that joins metal parts together by applying pressure and passing an electric current through the area to be welded. The resistance to the flow of electricity at the interface between the parts generates heat, which melts and fuses the materials together. This process is widely used in manufacturing for its speed, efficiency, and reliability. Here's how resistance welding typically works:

1. Preparation: The metal parts to be welded are properly cleaned and positioned in the welding fixture.
2. Application of Pressure: Pressure is applied to the parts to be welded to ensure good contact and alignment between them. This pressure helps to create intimate contact between the surfaces, reducing electrical resistance and facilitating heat generation.
3. Passage of Current: An electric current is passed through the metal parts at the weld interface. The current flows through the path of least resistance, which is typically at the contact points between the parts. The resistance to the flow of electricity at these contact points generates heat due to the Joule heating effect.
4. Heating and Welding: The heat generated by the electrical resistance melts the metal at the weld interface, forming a molten pool. Once the metal reaches its melting point, pressure is maintained to ensure proper fusion between the parts. The current is then switched off, allowing the molten metal to solidify and form a strong weld joint.
5. Cooling and Solidification: After the current is turned off, the welded area is allowed to cool and solidify. The resulting weld joint is usually strong and durable, as the fusion occurs at the molecular level.

Resistance welding can take several forms, including spot welding, seam welding, projection welding, and flash welding, each suited to specific applications and materials. It is commonly used in industries such as automotive manufacturing, aerospace, electronics, and construction for joining metal components reliably and efficiently. Additionally, resistance welding is known for its ability to produce welds with minimal distortion and without the need for filler materials.