Pipeline systems are used as the most economical solution for the transportation of the media used in the oil and gas industry. The major fabrication process representing the period elapsed from production of the pipes to service installation is welding. The weld zone represents the most critical zone in terms of the material properties in the respective pipeline components. In addition to the chosen welding method, selection of the steel material and welding consumables appropriate for the selected material are of significant importance. Today, most of line pipes are manufactured according to API standards. Cost savings have been achieved by the reduction of the wall thickness, transportation and the welding processes. In this study, the mechanical properties of welded microalloyed X42, X52, X60, X65, and X70 steels, which are generally used in the oil and gas industry based on API standards, were examined by taking into consideration their microalloying elements and the carbon content. Then, these steels were joined by using submerged arc welding (SAW). The weld zones and changes in the post-weld mechanical properties were investigated. As expected, while tensile and hardness values were increased compared to base material, the toughness values decreased.