Low-yield ratio high-strength electric resistance welded steel pipe, steel strip for electric resistance welded steel pipes, and methods of manufacturing them

摘要

A low-yield ratio high-strength electric resistance welded steel pipe has a yield ratio of 80% or less and a TS of 655 MPa or more. A steel material has a composition containing 0.38% to 0.45% C, 0.1% to 0.3% Si, 1.0% to 1.8% Mn, 0.03% or less P, 0.03% or less S, 0.01% to 0.07% sol. Al, and 0.01% or less N on a mass basis.