STEEL MATERIAL AND EXPANDABLE PIPES USED IN OIL INDUSTRY Russian patent published in 2019 - IPC C22C38/16 C22C38/38 C22C38/58 

FIELD: metallurgy.

SUBSTANCE: invention relates to steel material used in oil and gas wells. Material has the following chemical composition, consisting of, wt. %: C from more than 0.6 to less than 1.8, Si from 0.05 to 1.00, Mn greater than 25.0 and 45.0 or less, Al from 0.003 to 0.06, P 0.03 or less, S 0.03 or less, Cu from 0.5 to 3.0, N 0.10 or less, V from 0 to 2.0, Cr from 0 to 3.0, Mo from 0 to 3.0, 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, REM from 0 to 0.01, B from 0 to 0.015, the rest is iron and impurities. Content C and V satisfy the condition: 0.6 < C−0.18 < 1.44. Microstructure of material consists of single phase of austenite.

EFFECT: material has high uniform elongation of 40 % or higher, yield point of 241 MPa or higher, and excellent resistance to sulphide cracking under stress after cold treatment.

7 cl, 2 dwg, 4 tbl, 2 ex