METHOD OF PRODUCING COLD-ROLLED ISOTROPIC ELECTRICAL-SHEET STEEL Russian patent published in 1999 - IPC

FIELD: production of cold-rolled isotropic electrical-sheet steel with improved electromagnetic properties. SUBSTANCE: melted steel containing 0.2-1.5% of silicon, 0.1-0.5% of aluminum, 0.02-0.05% of carbon, 0.15-1.0% of manganese and 0.01-0.16% of phosphorus is subjected to hot and single cold rolling to final thickness, decarburizing annealing of cold-rolled metal within temperature range of 980-800 C. Annealing of cold-rolled steel at initial stage is started with heating and holding of metal in atmosphere of protective gas at temperature which is determined depending on content of silicon and aluminum in compliance with relation t_в = K1 + K2(Si-Al)±5^oC, where t_в is temperature of steel holding, C; K1 and K2 are experimentally determined coefficients, K1 = 915, and K2 = 30; Si is silicon content in steel, %; Al is aluminum content in steel, %; holding duration is selected depending on the sum of alloying elements of silicon and aluminum (Si+Al) = (0.30-1.0)% = 50-85 s; (Si+Al) = (1.1-1.5)% = 90-125 s; (Si+Al) = (1.6-2.0)% = 130-200 s. In the course of annealing, continuous transition from temperature of steel holding of 919-980 C for decarburizing of metal to carbon content of less than 0.005% in damp nitrogen-hydrogen atmosphere takes place with decrease of steel annealing temperature to 800-870 C at the final stage of heat treatment. EFFECT: improved electromagnetic properties of steel. 1 tbl