METHOD FOR THERMAL ROLLING OF COLD-ROLLED STRIP OF ISOTROPIC ELECTRICAL STEEL Russian patent published in 1997 - IPC

FIELD: ferrous metallurgy. SUBSTANCE: invention relates to producing cold-rolled stock 0.35-0.7 mm thick with high electromagnetic properties, with or without electrical insulation coating, designed for manufacturing parts for magnetic conductors free of barbs, cleavages, and other malformations from steel containing (in wt %): carbon, 0.02-0.06; silicon, 0.2-3.2; manganese, 0.1-0.5; phosphorus, at most 0.18; sulfur, at most 0.008; chromium and nickel, at most 0.06 each; copper, at most 15; aluminium, 0.2- 0.6; titanium, at most 0.02; and iron, the balance, in conformity with technology involving annealing in continuously operated plants. Invention is distinguished with that hot-rolled strips up to 2.5 mm thick, after or without heat treatment and after etching, are subjected to cold rolling to final thickness. Thereafter, strips are degreased, washed, and subjected to decarbonizing baking in pusher- type furnace at 800-1050 C in nitrogen-hydrogen atmosphere, while ratio of steam content to hydrogen content drops from maximum, 0.26, to minimum, 0.006, in the temperature range 800 to 1050 C. Cooling to intermediary temperature 750-780 C is performed at rate 60-90 C/min in moistened nitrogen-hydrogen atmosphere with above-mentioned ratio rising from minimum to close to maximum, whereupon cooling proceeds with arbitrary rate to ambient temperature. EFFECT: improved electromagnetic properties of product.. 2 cl, 4 tbl