| 摘要 |
<p>The present invention provides a hot coil for line pipe use which can reduce deviation in ordinary temperature strength and improve low temperature toughness despite the numerous restrictions in production conditions due to the coiling step and provides a method of production of the same, specifically makes the steel plate stop for a predetermined time between rolling passes in the recrystallization temperature range and performs cooling by two stages after hot rolling so as to thereby make the steel structure at the center part of plate thickness and effective crystal grain size of 3 to 10 µm, make the total of the area ratios of bainite and acicular ferrite 60 to 99%, and make the absolute value of A-B 0 to 30% when the totals of the area ratios of bainite and acicular ferrite at any two portions are designated as respectively A and B.</p> |
