Introduction Of Welding Technology

Welding Definition:

Welding is the process of joining two metallic components for the desired purpose, can be defined as the process of joining two similar or dissimilar metallic components with the application of heat, with or without the application of pressure and with or without the use of filler metal.

Welding is a process for joining two similar or dissimilar metals by fusion. It joins different metals/alloys, with or without the application of pressure and with or without the use of filler metal. The fusion of metal takes place by means of heat. The heat may be generated either from combustion of gases, electric arc, electric resistance or by chemical reaction. During some type of welding processes, pressure may also be employed, but this is not an essential requirement for all welding processes. Welding provides a permanent joint but it normally affects the metallurgy of the components. It is therefore usually accompanied by post weld heat treatment for most of the critical components. The welding is widely used as a fabrication and repairing process in industries. Some of the typical applications of welding include the fabrication of ships, pressure vessels, automobile bodies, off-shore platform, bridges, welded pipes, sealing of nuclear fuel and explosives, etc. Most of the metals and alloys can be welded by one type of welding process or the other. However, some are easier to weld than others. To compare this ease in welding term ‘weldability’ is often used. The weldability may be defined as property of a metal which indicates the ease with which it can be welded with other similar or dissimilar metals. Weldability of a material depends upon various factors like the metallurgical changes that occur due to welding, changes in hardness in and around the weld, gas evolution and absorption, extent of oxidation, and the effect on cracking tendency of the joint. Plain low carbon steel (C-0.12%) has the best weldability amongst metals. Generally it is seen that the materials with high castability usually have low weldability. of the plate. The top vee angle is either 60° or 80°, while the bottom angle is 80°, depending on the technique being used.

welding terminology 

Welding Terminology:

The terminological elements of welding process used with common welding joints such as base metal, fusion zone, weld face, root face, root opening toe and root are depicted in Fig.

Different Types Of Welding Joint:

Lap Joint

1.Single-Lap Joint:This joint, made by overlapping the edges of the plate, is not recommended for most work. The single lap has very little resistance to bending. It can be used satisfactorily for joining two cylinders that fit inside one another.

2.Double-Lap Joint: This is stronger than the single-lap joint but has the disadvantage that it requires twice as much welding.

3.Tee Fillet Weld: This type of joint, although widely used, should not be employed if an alternative design is possible.

Butt weld joint

1.Single-Vee Butt Weld: It is used for plates up to 15.8 mm thick. The angle of the vee depends upon the

technique being used, the plates being spaced approximately 3.2 mm.

2.Double-Vee Butt Weld: It is used for plates over 13 mm thick when the welding can be performed on both sides

There Are different Types Of Welding Position:

1.Flat or Down hand Welding Position:

2.Horizontal Welding Position:

3. Vertical Welding Position:

4.Overhead Welding Position: