FIELD: metallurgy.
SUBSTANCE: invention relates to metallurgy, namely to production of sheet of electrical steel with oriented grain structure used as material of iron cores of transformers. Steel billet is hot-rolled with the following chemical composition, wt.%: from 0.030 to 0.100 of C; from 0.80 to 7.00 of Si; from 0.01 to 1.00 of Mn; from 0 to 0.060 in total of S and Se; from 0.010 to 0.065 of acid-soluble Al; from 0.004 to 0.012 of N; from 0 to 0.30 of Cr; from 0 to 0.40 of Cu; from 0 to 0.50 of P; from 0 to 0.30 of Sn; from 0 to 0.30 of Sb; from 0 to 1.00 of Ni; from 0 to 0.008 of B; from 0 to 0.15 of V; from 0 to 0.20 of Nb; from 0 to 0.10 of Mo; from 0 to 0.015 of Ti; from 0 to 0.010 of Bi, the rest is iron and impurities, with production of hot-rolled steel sheet. Obtained sheet is subjected to cold rolling and decarburizing annealing in atmosphere with PH2O/PH2 value of 0.18–0.80, at temperature of 750–900 °C and a holding time of 10–600 seconds, then, after reducing the temperature, the oxide layer is removed from the surface by etching in a mixed solution of hydrofluoric acid and sulfuric acid. Annealing separator comprising Al2O3 and MgO is applied on the decarbonized annealed steel sheet and dry at a value of MgO/(MgO+Al2O3) of 5–50 %, and an amount of hydrated water of 1.5 wt.% or less. Finishing annealing is performed at oxidation degree of 0.00010–0.2, when atmosphere includes hydrogen, or dew point equal to 0 °C or less, when atmosphere consists of inert gas without hydrogen. Excess annealing separator is removed from the sheet surface by washing with water using a solution with an inhibitor, which is at least one of triethanolamine, colophony amine or mercaptan, and the amount of iron hydroxide and iron oxide on the surface is controlled so that it is 0.9 g/m2 or less per side. Insulating coating is formed on the surface of the sheet by applying a solution containing phosphoric acid and a metal compound, in which the weight ratio of phosphoric acid and metal compound is from 2:1 to 1:2, and baking at 600–1,150 °C, and after reducing the application temperature of the solution containing phosphate and colloidal silica and not containing a metal compound, which is baked at 600–1,150 °C.
EFFECT: sheet has excellent magnetic characteristics and coating adhesion.
6 cl, 13 tbl, 1 dwg
