PURPOSE:To economically obtain a Cr-Mo steel for pressure vessels having excellent hydrogen erosion resistant characteristic and Sr crack resistant characteristic, by specifying a compsn. consisting of C, Si, Mn, Cr, Mo, B, Al, and Fe and controlling the content of S as impurities. CONSTITUTION:This Cr-Mo steel for pressure vessels having the excellent hydrogen erosion resistant characteristic and SR crack resistant characteristic consists of the compsn. contg. 0.07-0.18wt% C, 0.10% Si, 0.05-1.0% Mn, 0.6-6.0% Cr, 0.3-1.5% Mo, 0.0003-0.010% B, and 0.003-0.20% solAl, contains further at least one kind among =0.50% V, =0.20% Nb, =0.20% Ti, and =0.20% Zr at need and consisting of the balance substantially Fe and impurities, and is limited in the content of S as the impurity to 0.0010%. Said steel is adequate for use particularly in high-temp. high-pressure hydrogen environment.
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