MARTENSITIC STAINLESS STEEL PRODUCT Russian patent published in 2020 - IPC C22C38/50 C21D8/00 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely to a martensite stainless steel product made, in particular, in the form of a pipe and used in oil and gas wells. Steel has chemical composition consisting of, wt%: C: 0.030 or less, Si: 1.00 or less, Mn: 1.00 or less, P: 0.030 or less, S: 0.005 or less, Al: 0.0010 to 0.0100, N: 0.0500 or less, Ni: from 5.00 to 6.50, Cr: from 10.00 to 13.40, Cu: from 1.80 to 3.50, Mo: from 1.00 to 4.00, V: 0.01 to 1.00, Ti: 0.050 to 0.300, Co: 0.300 or less, W: 0 to 1.50, the rest is iron and impurities. Steel has yield strength 724–860 MPa, and its composition satisfies the following ratios: 11.5≤Cr+2Mo+2Cu-1.5Ni≤14.3 and Ti/C≥7.5. Microstructure of steel contains martensite with volume fraction of 80 % or more, wherein size of each intermetallic compound and each Cr oxide in microstructure is 5.0 mcm² or less, and total fraction of area of intermetallic compounds and Cr oxides is 3.0 % or less.

EFFECT: manufactured product has high resistance to sulphide cracking under stress.

3 cl, 3 dwg, 2 tbl