Investigation of Fracture behaviour of API X70 Pipeline Steel

Abstract

Oil and gas production has significantly increased over the years in order to meet future demands for oil and gas products, regardless of the unstable price being experienced by producing nations. The use of pipelines for the transportation of these products has been the globally recognized solution. These pipelines are fabricated by welding and their fracture properties depend on a number of factors which include temperature, particularly for pipelines operating in cold environment such as deeper water depths. Therefore, information of fracture behaviour of welded pipelines located in cold regions is therefore important for reliable design for service. In this paper, fracture behaviour of welded x70 pipeline steel was investigated using charpy v-notch specimens. Impact tests were carried out on weld and parent materials at temperatures -10°C, -20°C, -40°C, -60°C, -80°C, -100°C, -120°C, -160°C, 0°C, 10°C and 20°C. Results revealed that higher energy was absorbed in the weld than in parent materials regardless of the test temperature used. results implied that the fracture behaviour of the material could be significantly influenced by temperature, welding and the notch sensitivity of the materials.