SHEET FROM UNSTRUCTURED ELECTRICAL STEEL AND METHOD OF MAKING SLAB USED AS MATERIAL THEREFOR

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FIELD : metallurgy. SUBSTANCE : invention relates to metallurgy, namely to production of slab used as material for sheet from unstructured electrical steel. Method includes refining molten steel tapped from a converter or an electric arc furnace using a vacuum degassing device, and continuous casting of molten steel using a continuous casting machine to produce a slab. In the process of refining, metal Si or Si-containing alloy is added by means of a device for vacuum degassing for deoxidation of molten steel by using Si. To molten steel, deoxidized by using Si, during refining, performed by means of a vacuum degassing device, or after refining performed by means of device for vacuum degassing, rare-earth metal-containing alloy is added, and then Ca-containing alloy is added to molten steel in ladle. Slab has a chemical composition which includes the following, wt. % : 0.0050 or less C, 1.5 to 5.0 Si, 0.2 to 3.0 Mn, 0.0030 or less sol. Al, 0.2 or less P, 0.0050 or less S, 0.0040 or less N, from 0.0010 to 0.0080 T.Ca, 0.0100 or less T.O, from 0.0001 to 0.0050 REM, the rest is Fe and unavoidable impurities. Slab can additionally contain at least one of elements of groups AC : group A consists of one or both elements selected from Sn and Sb, each in amount from 0.01 to 0.1 wt. %, group B consists of Mg in amount of from 0.0001 to 0.0050 wt. % and group C consists of at least one element selected from Cu, Ni and Cr, each in amount of 0.01 to 0.5 wt. %. In the slab, the value of the fractional expression ((T.Ca + REM)/(T.O + S)), which is an expression of the ratios of the weights of the four components, including T.Ca, REM, T.O and S, is 0.4 or more, fractional expression value ((wt. % CaO + wt. % REM oxides)/(wt. % CaO + wt. % REM oxides + wt. % SiO2 + wt. % Al2O3)), which is an expression of the ratio of concentrations of CaO and oxides of rare-earth metals to concentrations of inclusions based on oxides, is 0.50 or more, and fractional expression (wt. % Al2O3/(wt. % CaO + wt. % REM oxides + wt. % SiO2 + wt. % Al2O3)), which is an expression of the ratio of concentration of Al2O3 to concentration of said inclusions based on oxides is 0.20 or less. EFFECT : sheets of unstructured electrical steel obtained from the slab have high density of magnetic flux and low loss in iron. 4 cl, 4 tbl, 2 ex