Welding process is one of the joining methods of metals. It can be applied in the solid and fusion states. In the fusion state welding, the amount of the heat generated highly affects the quality of weldments from the mechanical properties point of view. To study this effect, three different fusion welding techniques were used to weld low carbon steel samples: Shield Metal Arc Welding (SMAW), Metal Inert Gas Welding (MIG), and Oxy Acetylene Welding (OAW). The mechanical properties of the welded joints were evaluated using mechanical tests such as tensile strength, hardness , and impact toughness. The results showed that MIG weldments have the best mechanical properties among the other welding techniques ,the reason is due to the amount of heat in the welding region in the (MIG) method is much less compared with other welding methods, which makes the size of the heat-affected zone (HAZ) less and thus obtaining smaller grains size in this area, which leads to an improvement mechanical characteristics of the welds.

Friction stir welding (FSW) has been used to join metallic and non-metallic materials without melting the base metal. this process employs a non-consumable rotary welding tool consist of a shoulder and a pin. the friction between the tool and the work piece generates heat which is coupled with the axial pressure on the tool contribute in the production of a permanent welding joint. this work reviews the influence of some operational and engineering parameters that may affect the performance of the friction stir welding and consequentially the mechanical properties of the welding joint..