METHOD OF HEAT TREATMENT OF COLD-ROLLED CARBON STEEL Russian patent published in 2006 - IPC C21D9/663 C21D9/48 

FIELD: ferrous metallurgy; heat treatment of rolls of cold-rolled product in bell-type furnace.

SUBSTANCE: proposed method consists in single-stage heating of rolls of cold-rolled sheet in bell-type furnace in shielding atmosphere to 620-660°C, holding the product in furnace during period of time depending on mass of lower layer of charge which is determined by the following formula: δ_hold=14.65+exp(-3.64+0.27M_low.roll-0.00309M² _low.roll), where δ_hold is holding time; M_low.roll is mass of lower roll in charge; then heating is switched off and product is cooled down in furnace to temperature of 550-610°C, after which bell is removed and product is cooled under muffle to temperature not above 140°C. Proposed method makes it possible to reduce sorting-out the product by fracture and sticking defects due to reduced duration of annealing and optimization of holding time.

EFFECT: increased output of furnace; reduced power requirements.

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