HIGH-STRENGTH STEEL MATERIAL FOR OIL WELL AND PIPES USED IN OIL INDUSTRY Russian patent published in 2019 - IPC C22C38/58 C22C38/38 C22C38/12 C21D8/10 

FIELD: metallurgy.

SUBSTANCE: invention relates to high-strength steel material for oil wells. Material has the following chemical composition, wt. %: C: from 0.70 to 1.8, Si: from 0.05 to 1.00, Mn: from 12.0 to 25.0, Al: from 0.003 to 0.06, P: 0.03 or less, S: 0.03 or less, N: 0.10 or less, V: more than 0.5 and 2.0 or less, Cr: from 0 to 2.0, Mo: from 0 to 3.0, Cu: from 0 to 1.5, Ni: from 0 to 1.5, Nb: from 0 to 0.5, Ta: from 0 to 0.5, Ti: from 0 to 0.5, Zr: from 0 to 0.5, Ca: from 0 to 0.005, Mg: from 0 to 0.005, B: from 0 to 0.015, the rest is iron and impurities. Content of C, V and Cr satisfy the following condition: 0.6≤C–0.18V–0.06Cr<1.44. Microstructure of material consists of austenite phase less than 0.1 vol. % α'-martensite and ferrite and 10 vol% or less ε-martensitic structure of HCP. Vanadium carbides having diameters of equivalent circle from 5 to 100 nm are present with numerical density of 20 pc/mcm² or higher, and yield point is 654 MPa or more.

EFFECT: material has excellent resistance to sulphide cracking under stress in medium of oil and gas wells containing hydrogen sulphide.

8 cl, 2 dwg, 2 tbl, 1 ex