STEEL OF IMPROVED CORROSION RESISTANCE AND ELECTRIC WELDED PIPES MADE FROM IT Russian patent published in 2011 - IPC C22C38/42 

FIELD: metallurgy.

SUBSTANCE: steel contains carbon, manganese, silica, chrome, nickel, copper, phosphorus, sulphur, aluminium, iron and inevitable impurities, including oxygen, at the following component ratio, wt %: carbon 0.03 - 0.20, manganese 0.10 - 1.20, silica 0.01 - 0.40, chrome 0.05 - 0.80, nickel 0.05 - 0.30, copper 0.05 - 0.30, phosphorus of not more than 0.020, sulphur of not more than 0,006, aluminium of not more than 0.01 - 0.06, oxygen of not more than 0.003, iron and inevitable impurities are the rest. Steel can also contain niobium in quantity of 0.01 - 0.07 wt % and calcium in quantity of 0.0001 - 0.008 wt %. Steel has ferrite-pearlite structure with banded orientation of not more than 2, and maximum allowable density value of corrosion-active non-metallic inclusions N_CANI, inclusions/mm², is determined depending on chrome content in steel in compliance with the following condition: |N_CANI| ≤ 1 + 10|Cr|, where |N_CANI| - absolute density value of corrosion-active non-metallic inclusions, |Cr| - absolute value of chrome content, wt %.

EFFECT: steel corrosion resistance is improved and electric welded pipes made from it owing to providing the absence of local sections with reduced corrosion resistance, as well manufacturability and weldability is improved, and strength, viscosity, cold resistance and cost parameters are maintained.

6 cl, 1 tbl, 1 ex