STEEL PIPE HAVING HYPER STRENGTH AND EXCELLENT LOW TEMPERATURE TENACITY OF SEAM WELDED PART AND METHOD FOR MANUFACTURING THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a line pipe having an excellent tenacity at low temperature and a hyper strength whose tensile strength is 900 MPa or higher (larger than X100 at API Standard), and which is easily welded at a job site, and a method for manufacturing therefore. ;SOLUTION: In the hyper strength seam welded steel pipe having an excellent low temperature tenacity, the a tensile strength of the base material is 900 MPa or larger, and the difference between the tensile strength of a welded metal portion and that of a base metal is -100 MPa or larger, the cap between an inner face welded metal portion formed by a regular welding executed after a tack welding of a butted portion of a steel plate in a pipe manufacturing process and an outer face welded metal portion is 0 mm or greater at the said welded metal zone of the seam welded steel pipe. The steel pipe is characterized by the overlapping of each of the inner face welded metal zone and the outer welded metal zone with a tack welded metal zone formed by the said tack welding.;COPYRIGHT: (C)2001,JPO