Microstructure of Welded Joints

Welding is a process of joining smaller pieces and components to build up bigger components. The joining is mostly done by creating a molten pool at the joints. Creation of molten pool is not always desired and thus joining in the solid state is sometimes done. Figure 1 shows the classification of the welding processes. In this
paper, discussion will pertain only to microstructures in welded joints made by creating a molten pool which solid-ifies to give the final joint. The heat input during melting and when the molten pool solidifies giving off the latent heat, and the temperature gradients created due to the heat sink effects by the solid metal surro-unding the molten pool affect the microstructure and introduces internal strain in the heat affected zone (HAZ) of the weld joint. There is a large number of books/handbooks which have been published in welding metallurgy in which microstructural aspects have been treated adequately. A few examples are given in References 1-5. The participants are requested to go through them.