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Abstract

A high-strength UOE steel pipe which has excellent deformability and excellent low-temperature toughness in its heat affected zone and which is suitable for use in a pipeline installed on permafrost in extremely cold regions or in earthquake-prone regions, for example, is provided. The UOE steel pipe has a steel composition consisting essentially of C: 0.03-0.07%, Si: 0.05-0.50%, Mn: 1.6-2.2%, P: at most 0.020%, S: at most 0.003%, Cu: 0.20-0.60%, Cr: at most 0.10%, Ni: 0.20-0.80%, Nb: 0.005-0.030%, Ti: 0.005-0.030%, N: at most 0.0070%, Al: 0.005-0.060%, and a remainder of Fe and impurities, the hardenability index Pcm is at most 0.22%, Cu+Cr+Ni is 0.4-1.5%, Nb+Mo+V is at most 0.05%. The pipe has a yield strength in the longitudinal direction of at least 480 MPa with a yield-tensile ratio of at most 85% and a Charpy absorbed energy of the heat affected zone at −40° C. of at least 40 J.

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