TUBE WORKPIECE FROM ALLOYED STEEL Russian patent published in 2012 - IPC C21D8/10 C22C38/18 C22C38/22 C22C38/42 

FIELD: metallurgy.

SUBSTANCE: hot-rolled tube workpiece is made from steel containing the following components, wt %: carbon 0.16-0.20, manganese 0.50-0.90, silicon 0.17-0.37, chrome 2.40-2.49, 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, when the following conditions are met: Cr_equiv>3.0, where: Cr_equiv=[Cr]+2[Mo]+5[V]+1.5[Nb]+1.5[Ti]. Steel is subject to modifying calcium treatment by means of additive on the basis of its introduction to metal for 0.0010-0.0030 wt %. Steel contains the following components as impurities, wt %: phosphorus not more than 0.015, hydrogen not more than 2 ppm, oxygen not more than 20 ppm. Steel has maximum values of properties as to macrostructure - up to 2 for each type: central porosity, spot non-homogeneity, segregation square, skin holes at the depth of not more than 2 mm, non-metallic inclusions: sulphides, line oxides, unstrained silicates with average value of not more than 2.5 and with maximum value of not more than 3.0, spot oxides, breakable silicates with average value of not more than 1.5 and with maximum value of not more than 2.0, plastic silicates, nitrides with average value of not more than 1.0 and with maximum value of not more than 1.5.

EFFECT: improving the complex of consumer properties of rolled stock and providing homogeneity of rolled stock macrostructure.

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