CORROSION RESISTANT STEEL FOR OIL-GAS EXTRACTING EQUIPMENT Russian patent published in 2011 - IPC C22C38/50 C22C38/28 

FIELD: metallurgy.

SUBSTANCE: steel contains carbon, silicon, manganese, chromium, molybdenum, vanadium, niobium, titanium, aluminium, calcium, nickel, copper, sulphur, phosphorus, nitrogen, hydrogen, oxygen, iron and unavoidable additives at following ratio of components, wt %: carbon 0.14 - 0.23, silicon 0.14 - 0.40, manganese 0.50 - 0.90, chromium 0.60 - 1.10, molybdenum 0.10 - 0.30, vanadium 0.05 -0.17, niobium 0.02 - 0.08, titanium 0.005 - 0.030, aluminium 0.020 - 0.050, calcium 0.0010 - 0.0030, nickel not over 0.30, copper not over 0.30, sulphur not over 0.010, phosphorus not over 0.015, nitrogen not over 0.010, oxygen not over 20 ppm, hydrogen not over 2 ppm, iron and unavoidable impurities - the rest. Chromium equivalent of steel meets the condition 1.6≤Cr_equiv≤2.5, where Cr_equiv=[Cr]+2·[Mo]+5·[V]+1.5·[Nb]+1.5·[Ti].

EFFECT: raised corrosion resistance of pipes for wells with mediums saturated with acid gases at ratio without decrease of cold resistance and strength characteristics.

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