Friction stir welding is a solid state joining technique, where a non-consumable rotating tool with a specially designed pin and shoulder is plunged into the abutting edges of a sheet or plate and simultaneously traversed along the joint line. The physical understanding of the process is described by the combined effort of experimental examination and modelling of the same. The primary thing in the process is to understand the temperature distribution as well as the material flow in and around the tool. The process is a combination of both thermal as well as mechanical work i.e it is a coupled thermo-mechanical process. To obtain a complete knowledge of the process as well as the physics underlying it, numerical simulations are very much essential. In the present work a model based approach is adopted in order to study the heat transfer and material flow during the process.