MANUFACTURING METHOD OF SHEET OF GRAIN-ORIENTED ELECTRIC STEEL WITH EXCEPTIONALLY HIGH MAGNETIC PROPERTIES Russian patent published in 2010 - IPC C21D8/12 C21D9/46 C22C38/60 H01F1/16 

FIELD: metallurgy.

SUBSTANCE: it is implemented heating of steel slab, containing in wt %: C from 0.025 up to 0.09, Si from 2.5 up to 4.0, soluble in acid Al from 0.022 up to 0.033, N from 0.003 up to 0.006, S and Se in the form of Seq equivalent S: Seq = S+0.405 Se from 0.008 up to 0.018, Mn from 0.03 up to 0.10, Ti < 0.005 and Fe and unavoidable admixtures are the rest, up to 1280°C or higher, hot rolling of slab with receiving of strip, regulation of velocity, at which N is extracted in the form of AlN up to extraction range 20% or lower, annealing of strip, cold rolling with final reduction ratio from 83 up to 92%, decarburisation annealing in aggregate with primary recrystallisation at early stage in the atmosphere at a ratio PH₂O/PH₂ from 0.30 up to 0.7 and then at the later stage in atmosphere at a ratio PH₂O/PH₂, equal to 0.2 or less with receiving of arbitrary diametre of equivalent circle of primary recrystallisation grains from 7 up to less than 18 mcm, azotising of sheet at its passing in mix gas made of hydrogen, nitrogen and ammonia, control of oxygen concentration So in steel strip before the secondary recrystallisation annealing from the calculation for thickness of strip 0.30 mm from 450 up to 700 h/mln inclusive, coating deposition annealing separator, implementation of secondary recrystallisation annealing in such atmosphere that in case when temperature of the hottest point of external periphery of roll are in the range of room temperature up to 950°C, is controlled so that it corresponds hydrogen with 25-75% of nitrogen, and ratio PH₂O/PH₂ would consist from 0.01 up to 0.15.

EFFECT: sheet with well formation of glass film and excellent magnetic properties.

6 cl, 2 dwg, 3 ex, 1 tbl