OIL COUNTRY TUBULAR GOOD FOR EXPANSION IN WELL AND DUPLEX STAINLESS STEEL USED FOR OIL COUNTRY TUBULAR GOOD FOR EXPANSION

摘要

An oil country tubular good for expansion according to the inventionis expanded in a well. The oil country tubular good for expansionaccording to the invention is formed of duplex stainless steel having acomposition containing, in percentage by mass, 0.005% to 0.03%C, 0.1% to1.0% Si, 0.2% to 2.0% Mn, at most 0.04% P, at most 0.015% S, 18.0% to27.0% Cr, 4.0% to 9.0% Ni, at most 0.040% Al, and 0.05% to 0.40% N, andthe balance consisting of Fe and impurities, a structure including anaustenite ratio in the range from 40% to 90%. The oil country tubular goodfor expansion according to the invention has a yield strength from 256 MPato 655 MPa, and a uniform elongation more than 20%. Therefore, the oilcountry tubular good for expansion according to the invention has a highpipe expansion characteristic.