| abstract |
The present invention provides steel plate for line pipe excellent in strength and ductility and a method of production of the same. The steel plate has a steel composition containing, by mass%, nC: 0.04 to 0.15%, nSi: 0.05 to 0.60%, nMn: 0.80 to 1.80%, nP: 0.020% or less, nS: 0.010% or less, nNb: 0.01 to 0.08%, and nAl: 0.003 to 0.08%, nhaving a balance of iron and unavoidable impurities, and having a value of Ceq shown by the following formula <1> of 0.48 or less, comprised of a mixed structure of ferrite and pearlite or ferrite and pearlite partially containing bainite in which a ferrite percentage is 60 to 95%, having a yield strength of 450 MPa or more, and having an amount of hydrogen contained in the steel of 0.1 ppm or less: Ceq = C + Mn / 6 + Cu + Ni / 15 + Cr + Mo + Nb + V + Ti / 5 + 5 B |