| 摘要 |
An object is to provide a hot-rolled steel sheet for a high strength linepipe excellent in terms of HIC resistance which is suitably used as a raw material of a high strength electric resistance welded linepipe of X70 or more in accordance with API standards. A hot-rolled steel sheet for a high strength linepipe having a tensile strength of 540 MPa or more, the steel sheet having a chemical composition containing, by mass%, C: 0.02% or more and 0.06% or less, Si: 0.05% or more and 0.25% or less, Mn: 0.60% or more and 1.10% or less, P: 0.008% or less, S: 0.0010% or less, Nb: 0.020% or more and 0.060% or less, Ti: 0.001% or more and 0.020% or less, Al: 0.01% or more and 0.08% or less, Ca: 0.0005% or more and 0.0050% or less, one or more selected from among Cu: 0.50% or less, Ni: 0.50% or less, Cr: 0.50% or less, Mo: 0.50% or less, and V: 0.10% or less, and the balance being Fe and inevitable impurities, in which the relationships 0.60 ‰¤ CP ‰¤ 0.90 and CM ‰¤ 3.05 are satisfied. |
