TUBE STOCK OUT OF CORROSION RESISTANT STEEL Russian patent published in 2011 - IPC C22C38/58 C22C38/44 C21D8/00 

FIELD: metallurgy.

SUBSTANCE: invention can be utilised at fabrication of seamless tubes implemented in equipment of power machine building, including heat power and nuclear electric stations requiring large amount of stainless tubes for pipeline systems, and also for oil-gas complex for construction of oil-gas fields containing hydrogen sulphide, carbon dioxide and chlorides. Steel contains the following elements, in wt %: carbon 0.01 - 0.03, silicon 0.05 - 1.0, manganese 0.8 - 3.0, chromium 16.0 - 19.0, nickel 8.5 - 11.5, molybdenum 2.0 - 4.0, nitrogen 0.15 - 0.45, REE (rare earth elements) 0.01 - 0.03, iron and unavoidable impurities - the rest. The following ratio is maintained for the components: (Ni+0.5Mn+30C+27N)/(Cr+Mo+1.5Si) ≥ 0.86. Steel has tensile strength in hardened condition not less, than 650 H/mm² and macrostructure for central porosity, pointed non-uniformity, liquation square, general speckle segregation and pipe segregation not more, than 1 point for each kind, non-metallic inclusions for sulphides, pointed oxides, line oxides. Fragile silicates, plastic silicates, non-deformed silicates, nitrides and lined carbonitrides and nitrides and carbonitrides pointed not more, than 2.5 points for each kind.

EFFECT: increased mechanical and corrosion properties of tube stock out of non-magnetic austenite chromium-nickel steel facilitating increased service life, reliability and safety of pipelines made out of it at reduced cost due to efficient alloying with nickel, maintaining resistance against inter-crystalline corrosion and due to meeting requirements to quality of tube surface.

6 tbl