HIGH-STRENGTH STEEL PIPE EXCELLENT IN FORMABILITY AND BURST CHARACTERISTICS

Title:

HIGH-STRENGTH STEEL PIPE EXCELLENT IN FORMABILITY AND BURST CHARACTERISTICS

Document Type and Number:

WIPO Patent Application WO/2001/094043

Kind Code:

A1

Abstract:

A method of producing, by a UOE method, a high-strength line pipe-use steel pipe having a steel-sheet strength exceeding 850 N/mm?2¿, the method producing a high-strength line pipe-use steel pipe having excellent formability and burst characteristics that prevent cracks or fractures in a seam-welded portion during a pipe expanding process and eliminate brittle-fracture originating at the seam-welded portion even under an inner-pressure load while the steel pipe is used. A method of producing, by a UOE method, a high-strength steel pipe having a tensile strength exceeding 850 N/mm?2¿, wherein the high-strength steel pipe has excellent formability and burst characteristics such that a ratio (R/r) of an average radius of curvature within a peripheral-direction 120- mm range including the welded portion of the steel pipe before pipe expanding during a pipe expanding process to a steel-pipe radius (r) after pipe expanding is 0.65-2.0 or alternatively a ratio (R/r) to a steel-pipe radius (r) is 0.90-2.0, and the steel pipe has excellent burst characteristics such that Vickers hardness Hv of a base metal, minimum Vickers hardness Hz at the HAZ portion, pipe body wall-thickness t, and welded portion peaking amount d of the steel pipe before pipe expanding during a pipe expanding process satisfy the following relation, (1 + 0.005 t &verbar $g(d) <) H¿z? ? 0.03584 H¿v??2¿ - 25.34 H¿v? + 4712.

Inventors:

TSURU EIJI (JP)
HARA TAKUYA (JP)
ASAHI HITOSHI (JP)
MIYAZAKI HIDEKI (JP)
YOSHIDA TATSUYA (JP)

Application Number:

PCT/JP2001/004877

Publication Date:

December 13, 2001

Filing Date:

June 08, 2001

Export Citation:

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Assignee:

NIPPON STEEL CORP (JP)
TSURU EIJI (JP)
HARA TAKUYA (JP)
ASAHI HITOSHI (JP)
MIYAZAKI HIDEKI (JP)
YOSHIDA TATSUYA (JP)

International Classes:

B21C37/08; B21C37/30; F16L9/17; (IPC1-7): B21C37/08

Foreign References:

JPS59199117A	1984-11-12
JPH0910850A	1997-01-14

Other References: