Nippon Steel Sumitomo Metal Corporation

Nippon Steel Corporation

Kei Murata

Yuji Arai

Yasuyoshi Hidaka

Yukimasa Ueda

There is provided a seamless steel pipe for line pipe, wherein a chemical composition consists, by mass percent, of C: 0.03-0.10%, Si: &#x2266;0.50%, Mn: 1.0-2.0%, P: &#x2266;0.050%, S: &#x2266;0.005%, Cr: 0.05-1.0%, Mo: 0.01-0.30%, Al: 0.001-0.10%, N: &#x2266;0.01%, Ni: 0.04-2.0%, Ca: 0.0005-0.0050%, Cu: 0-2.0%, Ti: 0-0.05%, Nb: 0-0.05%, V: 0-0.10%, the balance: Fe and impurities, and satisfies the conditions of Cu+Ni: &#x2267;0.10%, and Mo+V: &#x2266;0.30%, wherein in a scale formed on the surface of the steel pipe, metal particles consisting mainly of Ni or Cu having an average circle-equivalent diameter of 0.1-5 &#x3bc;m exist, and a distance from a boundary between the base metal of the steel pipe and the scale to a region in which the metal particles do not exist is 20 &#x3bc;m or longer.

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Tokyo, Japan

Kei Murata