AUSTENITIC HIGH-STRENGTH CORROSION-RESISTANT NON-MAGNETIC NITROGEN-CONTAINING STEEL “ЗИ135” Russian patent published in 2024 - IPC C22C38/58 C22C38/44 C22C38/42 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to austenitic high-strength corrosion-resistant non-magnetic steel used for production of products for underwater extraction of hydrocarbons, in particular, heavy drill pipes. Steel contains components at the following ratio, wt.%: carbon not more than 0.05, chromium 17.0–19.0, nickel 3.0–4.2, manganese 18.5–20.5, molybdenum 1.5–2.5, nitrogen 0.40–0.55, silicon is not more than 0.6, copper is not more than 0.6, sulphur is not more than 0.010, phosphorus is not more than 0.030, iron and unavoidable impurities are the rest. Steel contains non-metallic inclusions, among which fine sulphides do not exceed point of 0.5, thin oxides — the first point, thin silicates — 1.5 points, thin globular inclusions — the first point, and thick sulphides, thick oxides, thick silicates and thick globular inclusions are not detected. Magnetic permeability of steel does not exceed 1.001 G/Oe, and equivalent number of resistance of steel to pitting corrosion PREN is ≥29, where PREN = %Cr+3.3%Mo+16%N.

EFFECT: providing high tensile strength and yield strength, lower magnetic permeability while maintaining impact viscosity and corrosion resistance, as well as high structural stability and manufacturability.

1 cl, 1 dwg, 2 tbl