High-strength steel material for oil wells, and oil well pipe

Abstract

This high-strength steel material for oil wells has a chemical composition which includes, in mass%, 0.70-1.8% of C, 0.05-1.00% of Si, 12.0-25.0% of Mn, 0.003-0.06% of Al, not more than 0.03% of P, not more than 0.03% of S, not more than 0.10% of N, over 0.5% but not more than 2.0% of V, 0-2.0% of Cr, 0-3.0% of Mo, 0-1.5% of Cu, 0-1.5% of Ni, 0-0.5% of Nb, 0-0.5% of Ta, 0-0.5% of Ti, 0-0.5% of Zr, 0-0.005% of Ca, 0-0.005% of Mg, and 0-0.015% of B, the remainder comprising Fe and impurities, and which satisfies [0.6< / =C-0.18V-0.06Cr<1.44]. The metallographic structure substantially comprises an austenite single phase. V carbides having a circle-equivalent diameter of 5-100 nm are present in a number density of at least 20 / [mu]m2. The yield strength is at least 654 MPa.

Description

technical field [0001] The present invention relates to high-strength oil well steel and oil well pipe, especially relates to the steel containing hydrogen sulfide (H 2 S) A high-strength steel material for oil wells excellent in sulfide stress crack resistance used in oil well and gas well environments, etc., and oil well pipes using the same. Background technique [0002] Contains H 2 Oil wells and gas wells of crude oil, natural gas, etc. of S (hereinafter, oil wells and gas wells are collectively referred to as "oil wells") have a problem of sulfide stress cracking of steel in a wet hydrogen sulfide environment (hereinafter, referred to as "SSC") , so oil well pipes with excellent SSC resistance are required. In recent years, there has been progress in increasing the strength of low-alloy acid-resistant oil well pipes for casing applications. [0003] The SSC resistance drops sharply as the strength of steel increases. Therefore, in the past, under the general evalua...

AI Technical Summary

Problems solved by technology

However, austenitic steels are generally solution-treated and are low-strength

In addition, in order to obtain a stable austenite structure, it is usually necessary to add a large amount of expensive constituent elements such as Ni, which significantly increases the manufacturing cost of the steel.

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