Welding is a technique of joining metals. It is widely used in fabrication as an alternative method for casting or forging and as a replacement for bolted and riveted joints. It is also used as a repair medium e.g., to reunite metal at a crack, to build up a small part that has broken off such as gear teeth or repair a worn surface as a bearing surface.A welded joint is a permanent joint which is obtained by the fusion of the edges of the two parts to be joined together, with or without application of pressure and filler material.Every welding process is not equally for each metal, type of joint or application.The skill of the welding engineer consists in the recognition of the essential requirements which a particular weld must satisfy and the choice of the appropriate process.
Basic requirements in welding:
Following are the must fulfill four requirements in welding process.
1) A supply of energy to create a union by fusion or pressure or both,
2) A mechanism for removing superficial contamination from the joint faces,
3) Avoidance of atmospheric contamination or its effects, and
4) Control of weld metallurgy.
Advantages of Welded Joints over Riveted Joints:
Following are the advantages of welded joints over riveted joints.
1) The welded structures are usually lighter than structures.
2) Alterations and additions can be easily made in existing structures.
3) A welded joint has a great strength.
4) The welded joints provide maximum efficiency.
5) As the welded structure is smooth in appearance, therefore it looks
pleasing.
6) The welding provides very rigid joints.
7) The process of welding takes less time than the riveting.
8) In welded connections, the tension members are not weakened as in the
case of riveted joints.