大径パイプライン継手の全姿勢電子ビーム溶接に関する研究 １ 全姿勢電子ビーム溶接における溶接姿勢と適正溶接条件の関係

Abstract

Conventionally, the site welding of large diameter natural gas line pipes have been performed by using arc welding processes, including shielded metal arc welding and. gas metal arc welding. In order to achieve a drastic improvement of the productivity, authors have executed fundamental study on the application of the electron beam welding process to the site welding of line pipes.This paper, as the first report, describes the influence of the welding position to the proper electron beam welding parameters in API-5L X65 line pipe steel of 19 mm thick. As a result of welding trials in various welding positions, it was clarified that the beam focusing condition and the welding speed should be properly controlled according to the welding position to obtain satisfactory weld bead shape. In the flat position, to prevent the under-fill on the surface, the beam focus had to be located under the plate surface. On the contrary, in the over-head position, the proper weld bead was obtained by positioning the beam focus outside the plate surface. In the vertical upward position, welding speed had to be kept lower to prevent the humping bead formation.On the basis of above investigation, it has been basically confirmed that the all-position circumferential welding of large diameter line pipes can be performed with the electron beam welding process.