METHOD OF PRODUCING SHEETS FROM LOW-ALLOY TUBE STEEL OF K65 STRENGTH CLASS Russian patent published in 2013 - IPC C21D8/02 C22C38/38 C22C38/42 

FIELD: metallurgy.

SUBSTANCE: steel is made containing the following elements in wt %: carbon 0.05-0.07, manganese 1.60-1.70, silicon 0.20-.032, sulfur 0.001-0.002, phosphors 0.003-0.012, nickel 0.15-0.25, chromium 0.15-0.25, copper 0.10-0.20, aluminium 0.025-0.045, niobium 0.075-0.095, titanium 0.01-0.02, vanadium 0.01-0.03, molybdenum 0.15-0.25, nitrogen 0.001-0.006, iron making the rest with carbon equivalent Ceq≤0.45% and cracking resistance in welding Pct≤0.23%. Note here that final deformation is started for final sheet thickness of 23-25 mm at rolling end temperature of 810±15°C and terminated at 810±10°C. In the case of final rolled sheet thickness of 25.1-28 mm it is started at rolling end temperature of 800±20°C and terminated at 790±10°C. Accelerated cooling rolled sheets is performed at two steps by turbulent water jets to cool surface of 23-25 mm-thick to rolling end temperature of 675±10°C at the rate of 20-30°C/a, and then by lamina water jets for 23-25mm-thick sheets to rolling end temperature of 505±15°C at the rate of 17-23°C/s, while for 25.1-28 mm-thick sheets to rolling end temperature of 495±15°C at the rate of 18-24°C/s

EFFECT: required mechanical properties.

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