Patent ID: 7967926
Filing Date: 2011-06-28
Classification: B21C,C21D,C22C,Y10T

Abstract:
1. A method of production of UOE steel pipe excellent in collapse strength, comprising successively C-ing, U-ing, and O-ing steel plate, seam welding the ends of the steel pipe, and expanding the pipe, said method of production of UOE steel pipe characterized by applying heat treatment after producing the UOE steel pipe, 0consisting essentially of, by wt %, C: 0.03 to 0.15%, 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, N: 0.001 to 0.01%, Mo: 0.6% or less, one or more of Ca: 0.01% or less, REM: 0.02% or less, and Mg: 0.006% or less, and a balance of Fe and unavoidable impurities, so that a heating temperature T 1 of the outside surface of said steel pipe and a heating time t 1 of the outside surface satisfy the following formula (1) and a heating temperature T 2 of an inside surface of said steel pipe and a heating time t 2 of the inside surface satisfy the following formula (2): where, T T