Q1: Filler metal is not used in the __________ welding.

ANS:D - all a, b & c

1. Seam Welding:
   • Seam welding is a process used to join two overlapping sheets or components along a continuous seam.
   • It is commonly used in the automotive industry for manufacturing fuel tanks, drums, and other cylindrical components.
   • In seam welding, a continuous weld is formed along the entire length of the seam.
   • Filler metal may be used in seam welding to ensure complete fusion and integrity along the seam. However, in some cases, it can be performed without filler metal.
2. Electric Spot Welding:
   • Electric spot welding is a resistance welding process used to join overlapping sheets or components at discrete points.
   • In spot welding, two electrodes apply pressure and pass a high electric current through the sheets at the desired weld points.
   • The resistance heating causes the metal to melt and form a weld nugget at the interface between the sheets.
   • Filler metal is not used in spot welding; instead, the weld nugget is formed solely from the base metal.
3. Projection Welding:
   • Projection welding is another type of resistance welding process used to join components with raised features or projections, such as studs or nuts, to a base material.
   • The raised features concentrate the current and provide localized heating, facilitating the welding process.
   • As with spot welding, filler metal is typically not required in projection welding, as the raised features ensure proper fusion between the components.

In summary, while seam welding may sometimes use filler metal to ensure complete fusion along the seam, electric spot welding and projection welding do not typically require filler metal. In spot welding, the weld nugget is formed solely from the base metal, while in projection welding, the raised features facilitate localized heating and fusion between the components.