Patent ID: 7459033
Filing Date: 2008-12-02
Classification: B21C,C21D,C22C,Y10S

Abstract:
1. Oil country tubular goods excellent in collapse characteristics after expansion consisting essentially of, by wt %: C: 0.03 to 0.3%, Si: 0.8% or less, Mn: 0.3 to 2.5%, P: 0.03% or less, S: 0.01% or less, Nb: 0.01 to 0.3%, Ti: 0.005 to 0.03%, Al: 0.1% or less, and N: 0.001 to 0.01% and a balance of Fe and unavoidable impurities, characterized in that a ratio of collapse pressure after expansion and collapse pressure before expansion is in the range of a/b: 0.85 to less than 1.0, where a: collapse strength (MPa) after expansion 10 to 20% and b: collapse strength (MPa) of unexpanded steel pipe of same dimensions as steel pipe measured for a, said oil country tubular goods has a hot rolled structure having a low temperature transformation phase of only bainitic ferrite or bainite alone or combined.