OIL COUNTRY TUBULAR GOODS EXCELLENT IN COLLAPSE CHARACTERISTICS AFTER EXPANSION AND METHOD OF PRODUCTION THEREOF

摘要

The present invention provides a method ofproduction of oil country tubular goods having a smalldrop in collapse pressure after expansion and having acollapse pressure recovering by low temperature ageing atabout 100°C and oil country tubular goods obtained by thismethod of production.This method of production comprises hot rolling asteel slab having amounts of addition of C, Mn, P, S, Nb,Ti, Al, and N in specific ranges and having a balance ofiron and unavoidable impurities and shaping the steelstrip coiled at a temperature of not more than 300°C as itis into a tube. Alternatively, it comprises heating steelpipe having amounts of addition of C, Mn, P, S, Nb, Ti,Al, and N in specific ranges and having a balance of ironand unavoidable impurities to a temperature of the Ac3[°C] to 1150°C, then cooling it in a range of 400 to800°Cat a rate of 5 to 50°C/second.