PROCEDURE FOR PRODUCTION OF PLATE IRON LOW-ALLOYED STRIP Russian patent published in 2010 - IPC C21D8/02 C22C38/38 

FIELD: metallurgy.

SUBSTANCE: continuous-cast work-piece is subject to austenisation at temperature 1170-1210°C during not less, than 6 hours, then it is roughed to thickness 4.0-7.5 of thickness of finished strip with temperature of finish rolling not below 900°C. Further there are performed cooling to temperature 780-820°C, finishing with shrinkage ratio per pass not less, than 12%, except for three last passes whereat shrinkage ratio is not less, than 2%, and accelerated cooling of the strip not later, than in 30 sec upon its coming out of a stand first to 320-620°C, and then to ambient temperature in a pile of not less, than five sheets. Upon strip cooling it is placed into a preliminary heated to 250-350°C furnace and conditioned during 1-5 hours, further it is cooled in air. Strips are produced out of steel containing, wt %: C- 0.04-0.1; Mn-1.60-1.90; Si-0.15-0.35; (Nb+V+Ti)-0.05-0.25; (Mo+Cr)-0.20-0.60; (Cu+Ni)-0.40-0.70; iron and impurities with contents of each impurity element less, than 0.03% - the rest. Also coefficient of fracture strength P_cm does not exceed 0.23%, while microstructure of the strip contains at least 70 vol. % of areas of bainite of lath morphology produced out of non-crystallized austenite with cross medium diametre (d^Y) of austenite grains not more, than 25 mcm.

EFFECT: upgraded strength properties at maintaining plasticity and cold resistance of strip of 15-30 mm thickness.

3 cl, 1 ex