METHOD FOR PRODUCING ULTRA LOW CARBON COLD-ROLLED ELECTROTECHNICAL ISOTROPIC STEEL WITH HIGH COMPLEX OF MAGNETIC AND MECHANICAL PROPERTIES Russian patent published in 2021 - IPC C21C7/00 C21D8/12 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of ferrous metallurgy, namely to production of ultra low carbon cold-rolled electrotechnical isotropic steel used for manufacturing high-frequency engines for electric cars and electrotechnical apparatuses with high power efficiency. The method includes steel smelting, combined blowing of the steel melt in a converter, decarburisation of the steel melt in a vacuum, alloying of the steel melt by carbon-refined ferrosilicon, continuous casting of the steel melt into slabs, hot rolling of the slabs, normalisation annealing, etching, cold rolling, and final annealing with application of an electrical insulating coating. Duting the steel smelting, hot briquet iron is used as a solid metal charge with a consumption of up to 200 kg/t of steel. After the combined blowing in a converter, the steel melt is poured into concrete monolithic steel ladles with a slag belt made of periclase-carbon bricks with the content of carbon no more than 10% wt. Metallurgical lime and high-alumina materials with the content of Al₂O₃ of at least 70% wt. are used at a ratio of 1:1 for induction of slag in the steel ladle. After the decarburisation in a vacuum, the steel melt located in the steel ladle is alloyed with ferrosilicon with the content of carbon no more than 0.01% wt. in an amount ensuring the content of silicon in the melt within the range of 2.5 to 3.5% wt. The steel melt is cast into slabs through an intermediate ladle and a crystalliser, using an assimilating slag-forming mixture for the intermediate ladle with the content of carbon no more than 0.35% wt. and a slag-forming mixture for the crystallser with the content of carbon no more than 2.1% wt., resulting in steel slabs containing, % wt.: less than 0.005 carbon, 2.5 to 3.5 silicon, 0.05 to 1.00 manganese, 0.001 to 0.013 nitrogen, less than 0.015 sulphur, 0.1 to 1.5 aluminium, 0.01 to 0.10 antimony, less than 0.01 titanium, iron and inevitable impurities the rest. Cold rolling is executed to the final thickness with a degree of reduction of at least 70%.

EFFECT: production of sheet steel exhibiting a high complex of magnetic and mechanical properties is ensured.

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