| abstract |
The present invention provides hot rolled steel plate for spiral pipe superior in low temperature toughness, thick in gauge, for example, having a plate thickness of 14 mm or more, and having a high strength of the API-X65 standard or more spiral pipe and a method of production of the same, that is, steel plate containing, by mass %, C: 0.01 to 0.1%, Si: 0.05 to 0.5%, Mn: 1 to 2%, P≦0.03%, S≦0.005%, O≦0.003%, Al: 0.005 to 0.05%, N: 0.0015 to 0.006%, Nb: 0.005 to 0.08%, Ti: 0.005 to 0.02%, N−14/48×Ti>0%, Nb−93/14×(N−14/48×Ti>0.005%, Mo: 0.01% to less than 0.1%, Cr: 0.01 to 0.3%, and Cu: 0.01 to 0.3%, and having a balance of Fe and unavoidable impurities, characterized in that an elongation rate of a microstructure unit in a cross-section in the pipe circumferential direction after pipemaking is 2 or less. |