How does resistance spot welding create heat?

How does resistance spot welding create heat?

• A. By arc heating
• B. By flame heating
• C. By laser heating
• D. By electrical resistance between two metal sheets under pressure

Answer: (D)

Heat in resistance spot welding comes from electrical resistance at the interface where the two overlapping metal sheets are pressed together by the electrodes. A very high current flows through that small contact area, and the energy dissipated there as I^2R heating raises the temperature rapidly. This localized heating melts the metal surfaces so they can fuse together to form a weld nugget as the current is stopped and the pieces are pressed together. The pressure is essential: it creates intimate contact for a consistent current path and concentrates the heat at the intended spot, while also aiding metal flow and solidification into a strong joint. This process relies on converting electrical energy directly into heat at the contact interface, unlike arc, flame, or laser heating, which use an external heat source.

Heat in resistance spot welding comes from electrical resistance at the interface where the two overlapping metal sheets are pressed together by the electrodes. A very high current flows through that small contact area, and the energy dissipated there as I^2R heating raises the temperature rapidly. This localized heating melts the metal surfaces so they can fuse together to form a weld nugget as the current is stopped and the pieces are pressed together. The pressure is essential: it creates intimate contact for a consistent current path and concentrates the heat at the intended spot, while also aiding metal flow and solidification into a strong joint. This process relies on converting electrical energy directly into heat at the contact interface, unlike arc, flame, or laser heating, which use an external heat source.