Strength, steel and its production manner for ductile satisfactory line flexible pipe

摘要

As for this strength and steel for ductile satisfactory line flexible pipe, mass % with, C: 0.07 - 0.15%, Si: 0.05 - 0.60%, Mn: 0.80 - 1.80%, P: 0.010 Below, S: 0.007% or less, V: 0.05 - 0.12%, Nb: 0.005 - 0.070%, Al: 0.005 - 0.08%, Ti: 0.005 - 0.030%, Ca: 0.0005 - 0.0035%, N: 0.0020 - 0.0060%, O: 0.0030% or less is contained, the remainder consists of the iron and the inevitable impurity, system is quarter-phase system of ferrite and the pearlite, surface integral factor of island shape martensite is under 1.5%, board thickness is above 18mm, yield strength is above 450MPa.