| 摘要 |
PURPOSE: A steel which has an excellent outer surface SCC resistance for pipelines without deteriorating fundamental requirements as the pipeline material is provided. CONSTITUTION: A steel comprises 0.03-0.16% of C, 0.5-2.0% of Mn, 0.5% or less of Si,0.02% or less of P, 0.01% or less of S, 0.10% or less of Al, 0.1% or less of N, and at least an element selected from 0.005-0.1% of Nb, 0.005-0.1% of Ti, 0.001-0.1% of V, 0.03-0.5% of Mo, 0.1-0.6% of Cr, 0.1-0.8% of Ni, 0.1-0.8% of Cu, 0.0003-0.003% of B, and 0.001-0.01% of Ca. The surface smoothness of the steel is so controlled as to have a centerline average roughness Ra of 7 micrometer or less and have a maximum height Rmax of 50 micrometer or less. This surface smoothness is obtained by applying shot-blast to the surface.
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