Patent ID: 8512487

Claim:
A seamless expandable oil country tubular article comprising: on a mass percent basis, about 0.010% to less than about 0.10% of C, about 0.05% to about 1% of Si, about 2.21% to about 4% of Mn, about 0.03% or less of P, about 0.015% or less of S, about 0.01% to about 0.06% of Al, about 0.007% or less of N, and about 0.005% or less of O; at least one of Nb, Mo, and Cr which are contained in the range of about 0.01% to about 0.2% of Nb, about 0.05% to about 0.5% of Mo, and about 0.05% to about 1.5% of Cr, so that equations (1) and (2) are satisfied; and Fe and unavoidable impurities as the balance: Mn+0.9Cr+2.6Mo≧2.0 (1) 4C−0.3Si+Mn+1.3Cr+1.5Mo≦4.5 (2) wherein the steel article has a microstructure that contains soft ferrite at a volume fraction of about 5% to about 70% and the balance substantially composed of bainite, martensite, bainitic ferrite, or a mixture containing at least two thereof and wherein the steel article has a yield ratio of no more than 74% and uniform deformation during expansion at an expansion ratio of 30% or more.