Abstract: A high-Cr martensite steel pipe having excellent pitting resistance and method for manufacturing the same, which involves forming a pipe of steel including C: about 0.03 wt % or less, Si: about 0.5 wt % or less, Mn: about 0.5-3.0 wt %, Cr: about 10.0-14.0 wt %, Ni: about 0.2-2.0 wt %, Cu: about 0.2-1.0 wt % and N: about 0.03 wt % or less with the balance being Fe and incidental impurities, and having a value X shown as defined in the following formula (1) of about 12.2 or more. The pipe is quenched after austenitizing it at a temperature substantially equal to an A.sub.C3 point or higher, and the pipe is annealed in a temperature range from about 550.degree. C. or higher to a temperature lower than an A.sub.C1 point.

Abstract: A martensitic steel for a line pipe having excellent corrosion resistance and weldability is disclosed. The martensitic steel contains about:0.02 wt % or less of C, 0.50 wt % or less of Si,0.2 to 3.0 wt % of Mn, 10 to 14 wt % of Cr,0.2 to 7.0 wt % of Ni, 0.2 to 5.0 wt % of Mo,0.1 wt % or less of Al, 0.07 wt % or less of N, andthe balance being Fe and incidental impurities; andthese elements satisfy substantially the following equations:(Cr %)+(Mo %)+0.1(N %)-3(C %).gtoreq.12.2,(Cr %)+3.5(Mo %)+10(N %)+0.2(Ni %)-20(C %).gtoreq.14.5, and150(C %)+100(N %)-(Ni %)-(Mn %).ltoreq.4.The martensitic steel may further contain at least one element selected from the group consisting ofabout 2.0 wt % or less of Cu, about 0.15 wt % or less of Ti, about 0.15 wt % or less of Zr, about 0.15 wt % or less of Ta andabout 0.006 wt % or less of Ca, andthese elements satisfy substantially the following equations:(Cr %)+(Mo %)+0.1(N %)+3(Cu %)-3(C %).gtoreq.12.2,(Cr %)+3.5(Mo %)+10(N %)+0.2(Ni %)-20(C %).gtoreq.14.

Abstract: A high-Cr martensitic steel pipe having excellent pitting resistance and method for manufacturing the same, which involves forming a pipe of steel including C: about 0.03 wt % or less, Si: about 0.5 wt % or less, Mn: about 0.5-3.0 wt %, Cr: about 10.0-14.0 wt %, Ni: about 0.2-2.0 wt %, Cu: about 0.2-1.0 wt % and N: about 0.03 wt % or less with the balance being Fe and incidental impurities, and having a value X shown as defined in the following formula (1) of about 12.2 or more. The pipe is quenched after austenitizing it at a temperature substantially equal to an Ac.sub.3 point or higher, and the pipe is tempered in a temperature range from about 550.degree. C. or higher to a temperature lower than an Ac.sub.1 point.