Mechanical and micro structural properties of X60 steel welded with different methods

In this study, 24'' diameter pipes produced from API 5L X60 steel, used in crude oil and natural gas pipelines, were investigated after various welding applications. Three specimens were prepared using different welding plans. IWelding methods used in welding plans are SMAW and TIG. In the welding plan; all specimens were welded with four beads namely; root pass, hot pass, fill pass and cap pass. Root pass and hot pass are one bead, whereas fill pass was applied as two beads and cap pass was formed as three beads. Totally all specimens were welded with seven beads. In the first specimen the root pass and the hot passes were welded with cellulosic electrod, the fill pass and the cap passes were welded with basic electrod. The second specimen's root and hot passes were welded with TIG, the fill and the cap passes were welded with basic electrod, whereas the third specimen's all passes are welded with TIG method. After the weldments, non destructive testing (ultrasonic and radiographic testing) and destructive testing (tensile, hardness, micro, macro and impact testing) were applied for all specimens. All the welded samples and test results were examined to obtain the best method giving the superior mechanical properties. According to the experimental results; the tensile strength values changed between 603–625 MPa and the notch impact toughness values were found to be in the range of 48.4–76 J depending on the samples. In additon, the hardness values were obtained between 163.4–175.3 HV for the investigated samples. As a result; the specimen 2 exhibited better properties compared to the other two samples.