MANUFACTURING METHOD OF ROLLED STEEL PLATE FROM LOW-ALLOY STEEL Russian patent published in 2013 - IPC C21D8/02 C21D9/46 C22C38/38 B21B1/26 

FIELD: metallurgy.

SUBSTANCE: method involves steel making with the following component ratio, wt %: C 0.04-0.08, Si 0.1-0.25, Mn 1.2-1.6, Ni 0.3-0.5, Mo 0.15-0.25, Cr<0.12, Cu 0.15-0.45, Al≤0.05, V 0.03-0.06, Nb 0.02-0.05, Ti 0.01-0.03, iron and impurities are the rest at content of each of them of less than 0.03% and with parameter of resistance to cracking, which is P_cm<0.23%; steel is poured into workpieces and heated and roughing-down is performed at the temperature of its beginning of not lower than 970°C with transition from longitudinal to transverse rolling with breakdown of width and with relative reductions per pass of not less than 10% to the thickness that is 3.5-5.2 of thickness of a ready-made plate; then, finishing is performed at the temperature of its beginning of not lower than 740°C, at first passes of which there performed is width breakdown with reduction of not more than 10% and finishing is ended with a planishing pass at the temperature of not lower than 720°C; after that, enhanced cooling of the plate is performed to the temperature determined from the following ratio: T=(717°C-0.11*h²)±15°C, where: 0.11 - empirical coefficient, °C/mm²; h - thickness of a ready-made plate, mm.

EFFECT: increasing strength properties of a plate with thickness of 30-40 mm to level DNV 485 IFD at maintaining sufficient ductility and cold resistance.

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