PROCEDURE FOR HEAT TREATMENT OF FLATS OUT OF LOW CARBON FERRITE-PEARLITE STEEL Russian patent published in 2011 - IPC C21D8/02 C21D1/02 C21D1/26 

FIELD: metallurgy.

SUBSTANCE: there is performed preliminary deformation at temperature 1000-850°C at summary reduction 65-75 %, finish deformation with reduction per pass not less, than 12 % and summary reduction not less, than 60 %, hardening after roll heating at rate over 35°C/min to temperature 150±10°C, further - in air; and negative hardening at temperature 650±20°C with conditioning and successive cooling in air. Also, negative hardening at temperature 650±20°C is carried out with interval 3.5-6.0 min/mm of thickness, whereupon there is performed stabilising tempering at temperature 450±10°C, conditioning for 4-10 hours and following cooling to temperature 250±20°C at rate 100-200°C/hour, further - to temperature 150±20°C at rate not over 40°C/hour and successive cooling in air.

EFFECT: increased cold resistance of flat.

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