METHOD FOR OBTAINING PLATE STEEL AND STEEL PIPES FOR ULTRAHIGH-STRONG PIPELINE Russian patent published in 2012 - IPC C21D8/02 C21D8/10 C21D9/08 C21D9/50 C22C38/58 

FIELD: metallurgy.

SUBSTANCE: plate steel for ultrahigh-strong pipelines is obtained from the steel containing the following components, wt %: C 0.03-0.08, Si 0.01-0.50, Mn 1.5-2.5, P 0.01 or less, S 0.0030 or less, Nb 0.0001-0.20, Al 0.0001-0.03, Ti 0.003-0.030, N 0.0010-0.0050, O 0.0050 or less, Fe and inevitable impurities are the rest; molten steel is poured into slab; slab is hot-rolled so that plate steel is obtained, and surface of plate steel is cooled at water flow rate of 0.6 m³/(m²·min) or less till the specified surface temperature of plate steel is higher than 540°C, and plate steel surface is cooled at water flow rate of 1.3 m³/(m²·min) or more. Pipe is formed of a plate using UO-press; submerged arc welding of adjacent plate section is performed on external and internal surfaces using welding wire and agglomerated or molten flux, and pipe is expanded.

EFFECT: providing ultimate tensile strength of 625 MPa and higher and excellent low-temperature impact strength.

9 cl, 3 tbl, 1 dwg