FIELD: metallurgy.
SUBSTANCE: invention relates to metallurgy, namely to production of electrotechnical steel sheet 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, so that hot-rolled steel sheet is obtained, which is subjected to cold rolling. Decarbonization annealing is carried out in an atmosphere with an oxidation degree of PH2O/PH2 of 0.01–0.15 at temperature of 750–900 °C and holding time of 10–600 s. Annealing separator is applied on the sheet, which includes MgO and MCl, which is at least one of chlorides of an alkali metal, an alkali-earth metal and Bi, with MCl/MgO value making 2–40 %, and its drying is performed. Finishing annealing is carried out at an oxidation degree of 0.00010–0.2, in the case of an atmosphere which includes hydrogen, or at dew point equal to 0 °C or less, in the case of an atmosphere consisting of an inert gas without hydrogen. Excess annealing separator is removed and an insulating coating is formed by applying a solution containing phosphoric acid and a metal compound in a weight ratio of phosphoric acid to a metal compound of 2:1 to 1:2, which is baked at 600–1,150°C. After reducing the temperature, a solution containing phosphate and colloidal silica and not containing a metal compound is applied, which is baked at 600–1,150°C.
EFFECT: sheet has excellent magnetic characteristics and coating adhesion.
6 cl, 1 dwg, 10 tbl
