Gazi Üniversitesi Fen Bilimleri Dergisi (Jan 2017)
Microstructure and Mechanical Properties of API 5L X70 Grade Steel Pipes Produced by Submerged Arc Welding Method
Abstract
In this study, API 5L X70 steel roll materials welded via submerged arc welding technique (SAW). Macrostructure, microstructure and mechanical properties of welded samples were investigated. Tensile, hardness, Charpy impact and bending tests were performed to determine of mechanical properties. Macrostructure analyses showed that full penetration was achieved on welded parts. Microstructure images showed that fine grain structures were formed in weld metal, large, complex and amorphous grain structures were dominated in the coarse grain region, whereas homogeneously distributed coaxial grain structures were dominated in the fine grained region in HAZ. In addition, it was observed from tensile test that yield and maximum tensile strength values of welded parts were higher than the main metals. According to the hardness tests, the highest hardness values were measured on the weld metal. Charpy impact tests showed that the highest fracture toughness values were measured on the main material, the lowest fracture toughness values were measured on the welded metal.
