A method for the production of welded thick-walled steel tubes having a large diameter

摘要

PURPOSE:To obtain the macro shapes and high toughness of the weld zone of good inside and outside surfaces by forming asymmetrical grooves on the inside and outside surfaces of the large-diameter thick-walled steel pipe, submerged-arc-welding the inside surface and welding the outside surface in two layers through large-current MIG welding and submerged arc welding. CONSTITUTION:The asymmetrical grooves in which the sectional area of the inside groove 2 is smaller than that of the outside groove 3 are formed to the blank pipe 1 being a large-diameter thick-walled steel pipe of thicknesses about 32-50mm in general, formed by both processes of U-forming and O-forming. Next, the inner side of the blank pipe 1 is welded from the groove deep part up to the groove surface part by a multielectrode submerged arc welding machine 5a of AC using fused flux. On the other hand, the outside surface side is subjected to the 1-run welding of the 1st layer and 2nd layer respectively by a large-current MIG welding torch 4 and submerged arc welding machine 5b.