Low-alloy steel having a high yield strength and a high sulphide-induced stress cracking resistance

Abstract

Steel containing, by weight: 0.3 to 0.5% C; 0.1 to 1% Si; 1% Mn or less; 0.03% P or less; 0.005% S or less; 0.3 to 1% Cr; 1 to 2% Mo; 0.3 to 1% W; 0.03 to 0.25% V; 0.01 to 0.15% Nb; 0.01 to 0.1% Al, the balance of the chemical composition of the steel consisting of Fe and impurities or residuals resulting from or as a necessary consequence of the smelting and casting processes carried out on the steel. The steel serves for manufacturing weldless pipes for hydrocarbon wells, the yield strength of the steel after heat treatment being equal to or greater than 862 MPa, or even equal to or greater than 965 MPa.

Description

Technical field [0001] The present invention relates to a low-alloy steel with high yield strength (limite d'élasticité), which has excellent resistance to sulfide stress cracking. The present invention is particularly suitable for containing hydrogen sulfide (H 2 S) Tubular products for hydrocarbon wells. Background technique [0002] With higher and higher pressure, higher and higher temperatures and in increasingly corrosive media (especially when it is loaded with hydrogen sulfide), deeper and deeper exploration of hydrocarbon wells And development, the demand for the use of low-alloy steel pipes that have both high yield strength and high resistance to stress cracking caused by sulfides is increasing. [0003] This is because hydrogen sulfide H 2 The presence of S is the cause of the dangerous cracking form of low alloy steel with high yield strength. The cracking is known as Sulfide Stress Cracking or SSC (Sulfide Stress Cracking), which may affect both casing and casing. A...

AI Technical Summary

Problems solved by technology

However, since there is thereby a risk that the yield strength of the steel will drop due to the high tempering temperature, patent application EP1862561 proposes to increase

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