LOW ALLOY STEEL FOR OIL COUNTRY TUBULAR GOODS AND SEAMLESS STEEL PIPE

摘要

The invention aims at providing a low alloy steel for the pipe for oil well use and a seamless steel pipe which are excellent in the resistance to sulfide stress cracking. A low alloy steel for the pipe for oil well use which exhibits a yield strength of 654 to 757MPa, characterized by having a composition which contains by mass C: 0.10 to 0.60%, Si: 0.05 to 0.5%, Mn: 0.05 to 3.0%, P: 0.025% or below, S: 0.010% or below, Al: 0.005 to 0.10%, O (oxygen): 0.01% or below, Cr: 3.0% or below and Mo: 3.0% or below in a total amount of Cr and Mo of 1.2% or above with the balance consisting of Fe and unavoidable impurities and by 10 or fewer non-metallic inclusions of 10µm or above in length per mm2 as determined by observation of the section.