Investigation of the microstructure and mechanical properties of X70m steel used in petroleum pipelines welded with submerging welding

In general, without the pipelines, we cannot afford the world's demands of oil and gas. Furthermore, the pipelines are safely energy transmission methods. Spiral welded steel pipes are widely used in oil and natural gas transmission lines. The welding parameters and the properties of the materials used play an important role in the quality of the pipeline. In this study, it was aimed to determine the microstructure and mechanical properties of X70M steel used in oil pipelines combined with submerged arc welding. To achieve this goal, the welded joint and the main material were subjected to tensile, hardness and notch impact tests. Optical microscopy (OM) and scanning electron microscope (SEM) were used for micro structural characterization processes. According to the tensile results obtained, the breakage was become on the main material and the strength of the welded joint was found to be higher than the main material. However, compared with the main material, the hardness of the weld metal was higher and the toughness was lower.