HIGH-STRENGTH STAINLESS STEEL FOR OIL WELLS AND PIPE MADE THEREOF Russian patent published in 2014 - IPC C22C38/44 

FIELD: metallurgy.

SUBSTANCE: proposed composition contains the following substances, in wt %. C: not over 0.05, Si: not over 1.0, Mn: not over 0.3, P: not over 0.05, S: less than 0.002, Cr: over 16 and not over 18, Mo: 1.5-3.0, Cu: 1.0-3.5, Ni: 3.5-6.5, Al: 0.001-0.1, N: not over 0.025 and O: not over 0.01, Fe and impurities making the rest. Steel features microstructure including martensite phase, 10-48.5 wt % of ferrite phase and not over 10 wt % of residual austenite phase. Steel yield point makes at least 758 MPa while uniform elongation makes at least 10%.

EFFECT: high corrosion resistance, high SSC-corrosion resistance at normal temperature and good machinability.

5 cl, 4 tbl, 1 ex