STEEL PLATE EXCELLENT IN SOUR RESISTANCE AND STEEL PIPE FOR LINEPIPES

摘要

Provided are a steel plate excellent in sour resistance and a steel pipe for linepipes.  The steel plate and the steel pipe are characterized by containing by mass C: 0.01 to 0.08%, Si: 0.10 to 0.50%, Mn: 1.00 to 1.50%, Ti: 0.005 to 0.030%, Nb: 0.01 to less than 0.04%, Ca: 0.0010 to 0.0040%, P: 0.015% or less, S: 0.0008% or less, O: 0.0020% or less, Al: 0.040% or less, with the balance being Fe and impurities, and are characterized in that the contents (in mass%) of Al and Si satisfy the relationships: Al 0.005% and 0.25% Si, or the relationships: Al 0.005 and Al + 0.1Si 0.03% and the contents (in mass%) of S, O, Si, and Ca satisfy the relationships: S/Ca 0.33 and O/Si 0.005.