Welding is a process by which two materials, usually metals, are permanently joined together by coalescence, which is induced by a combination of temperature, pressure, and metallurgical conditions.

Advantages:

1). Provides permanent joint

2). The welded joint can be stronger than the parent materials

3). Low cost

Disadvantages:

1). Need skilled labor

2). Dangerous

3). Disassembly not possible

4). Heat related defects

Oxyfuel gas welding (OGW): refers to a group of welding processes that use, as their heat source, the flame produced by the combustion of a fuel gas and oxygen.

Arc welding (AW): is a fusion welding process in which coalescence of the metals is achieved by the heat from an electric arc between an electrode and the work.

Resistance welding (RW): achieves coalescence using heat from electrical resistance to the flow of a current passing between the faying surfaces of the two parts held together under pressure.

Laser beam welding (LBW): applies laser beam to achieve coalescence of metals.

Diffusion welding (DFW): two surfaces are held together under pressure at an elevated temperature and the parts coalesce by s0lid-state fusion.

Friction welding (FRW): is achieved by the heat of friction between two surfaces.

Ultrasonic welding (USW): is performed by applying a moderate pressure between the two parts and using an oscillating motion at ultrasonic frequencies in the direction parallel to the contacting surfaces.

Created by Dr. Wang