The investigation of the mechanical properties and microstructure of the IF 7114 steel joined by friction stir welding

Friction stir welding is a solid state welding process that has been developed in the recent years. Friction stir welding has many advantages over the fusion welding methods and its use in the industry is increasing day by day. Today, for many applications where formability is needed, there is the need to join IF (Interstitial Free) steel by keeping its properties of strength and ductility. In this study, IF 7114 steel used for automotive industry has been joined under various welding parameters by using friction stir welding process. In the study performed, the mechanical properties of the samples joined under the tool press force changing in different rotation and welding speed; and the effects of the welding parameters used on the microstructure of the welding zone are examined. The temperatures in the stir zone reached during the welding process are recorded by using thermocouples. The microstructure emerging in the welding zone has become fine structure compared to the original grain size. The strength values of the welding zone turn out to be higher than the base metal. As a result, it is observed that mechanical properties and microstructure depend crucially on the welding conditions.