METHOD FOR PRODUCTION OF PLATE STEEL FOR PRODUCTION OF ELECTRIC-WELDED PIPES OF UNDERWATER PIPELINES Russian patent published in 2020 - IPC C21D8/02 C22C38/00 B21B1/26 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, particularly, to production of plate-rolled products with thickness of up to 45 mm. To ensure high level of mechanical properties of rolled stock of strength category X65-X70, amount of viscous component at temperature from -10 to -30 °C not less than 85 % and value of absorbed energy at temperature from - 20 to -40 °C not less than 180 J, austenisation of workpiece from steel containing, wt.%: C 0.02÷0.08; Si 0.10÷0.35; Mn 1.10÷2.00; Cr 0.01÷0.30; Ni 0.01÷0.50; Cu 0.01÷0.30; Mo not more than 0.10; Al 0.02÷0.05; Nb 0.02÷0.06; V 0.001÷0.060; Ti 0.005÷0.030; S not more than 0.0030; P not more than 0.015; N 0.001÷0.008, Fe and unavoidable impurities – balance, wherein content of manganese corresponds to ratio where R_m – tensile strength, N/mm², wherein the austenitization temperature of the workpiece corresponds to the expression after which roughing the workpiece is performed with subsequent exposure of the rolled stock, finishing rolling at beginning temperature corresponding to and end at temperature of obtained sheet, (T_CP±25)°C, wherein T_CP=(A_e3-0.031⋅h²+0.411⋅h-38), then cooling the obtained sheet in a controlled cooling unit at a cooling rate of 10.0÷25.0 °C/s to 200÷550 °C and subsequent cooling of sheet separately or in stack in air.

EFFECT: high level of mechanical properties of rolled metal.

3 cl, 4 tbl