Characteristics of microstructures and mechanical properties of laser welded API X-100 steel for line pipe

Abstract

The strength of materials for pipe line becomes higher, because that is increase the capacity of transportation such as oil or gas. The performance of those welds was decreased by increasing of alloy contents added to increase the strength.In this study, high strength API X-100 steel was welded with 10kW fiber laser on bead-on-plate. The process parameters such as laser output power, travel speed and focal position were changed to increase weld quality. To investigate the weld defects or bead shape, the cross sectional views were observed with optical microscope. Also it was welded with laser on I-butt joint with milled edge. The weld was evaluated with microstructure, hardness and mechanical test. From the results, the tensile strength was 700∼750MPa and the absorbed energy on Charpy’s impact test at -20℃ was achieved 180∼210J on weld joint.The strength of materials for pipe line becomes higher, because that is increase the capacity of transportation such as oil or gas. The performance of those welds was decreased by increasing of alloy contents added to increase the strength.In this study, high strength API X-100 steel was welded with 10kW fiber laser on bead-on-plate. The process parameters such as laser output power, travel speed and focal position were changed to increase weld quality. To investigate the weld defects or bead shape, the cross sectional views were observed with optical microscope. Also it was welded with laser on I-butt joint with milled edge. The weld was evaluated with microstructure, hardness and mechanical test. From the results, the tensile strength was 700∼750MPa and the absorbed energy on Charpy’s impact test at -20℃ was achieved 180∼210J on weld joint.