| 摘要 |
<p>A steel for steel pipes excellent in sour resistance which contains C, Mn, Si, P, S, Ti, Al, Ca, N, O and, if necessary, one or more of Cr, Ni, Cu, Mo, V, B and Nb in prescribed amounts, in which the inclusion of the steel comprises Ca, Al, O and S as the main components and in which the CaO content of the inclusion is 30 to 80% with the ratio of N content (ppm) of the steel to CaO content (%) of the inclusion falling within the range of 0.28 to 2.0 and the CaS content of the inclusion is 25% or below; and a process for manufacturing the steel for steel pipes which comprises adding Ca in such a way that the ratio of N content (ppm) of steel to the quantity (kg/t) of Ca added to molten steel falls within the range of 200 to 857. The process can optimize slag composition, temperature raising of molten steel, stirring of molten steel and slag, and addition of Ca, thus enabling stable production of high-strength and HIC-resistant steel for steel pipes having excellent sour resistance and cleanliness.</p> |
