Welding is a permanent joining method by fusion, with or without the use of filler metal. It is an important fabrication process. Welding divided into two groups.
Fusion welding - In fusion welding, the metal being joined is melted and fuses together by subsequent solidification of molten metal. If necessary, a molten filler metal is also added.
E.g., Gas welding, arc welding, thermite welding.
Pressure welding- The metals being joined never melted, the union of metal obtained by application of pressure at welding temperature.
E.g., Resistance welding, forge welding.
Advantage of welding
1.Welded joint has high strength, sometimes more than the parent metal.
2.Different material can be welded.
3.Welding can be performed anyplace, no need enough clearance.
4.They give smooth appearance and simplicity in design.
5.They can be done in any shape and any direction.
6.It can be automated.
7.Provide a complete rigid joint.
8.Addition and modification of existing structures are easy.
Disadvantage of welding
1.Members may become distorted due to uneven heating and cooling during welding.
2.They are permanent joint, to dismantle we have to break the weld.
3.High initial investment