TUBE WORKPIECE FROM ALLOYED STEEL Russian patent published in 2013 - IPC C22C38/50 C21D8/10 

FIELD: metallurgy.

SUBSTANCE: workpiece is made from alloyed steel containing the following components, wt %: carbon 0.16 - 0.20, manganese 0.50 - 0.90, silicon 0.17 - 0.37, chrome 2.50 - 3.00, nickel 0.05 - 0.25, molybdenum 0.15 - 0.25, vanadium 0.05 - 0.10, niobium 0.03 - 0.06, titanium 0.005 - 0.030, aluminium 0.020 - 0.050, copper 0.10 - 0.30, sulphur 0.0001 - 0.010; nitrogen 0.001 - 0.008; iron and inevitable impurities are the rest. Steel contains the following components as impurities, wt %: phosphorus 0.001 - 0.015, hydrogen of not more than 2 ppm, oxygen of not more than 20 ppm, and its components meet the following ratio: Cr_equiv. > 3.0, where: Cr_equiv=[Cr] + 2[Mo] + 5[V] + 1.5[Nb] + 1.5[Ti]. Casting has maximum values of properties as to macrostructure - up to 2 for each type: central porosity, point non-homogeneity, liquation square, subsurface pinholes to the depth of not more than 2 mm, and content of non-metallic inclusions for sulphides, line oxides, non-deformable silicates as to an average point - not more than 2.5 and as to maximum point - not more than 3.0, for line oxides, brittle silicates as to an average point - not more than 1.5 and as to maximum point - not more than 2.0; for plastic silicates, nitrides as to an average point -not more than 1.0 and as to maximum point - not more than 1.5.

EFFECT: increasing homogeneity of rolled steel macrostructure and reducing the content of non-metallic inclusions, which lead to improvement of a set of consumer properties.

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