HOT-ROLLED STEEL SHEET FOR THICK-WALLED HIGH-STRENGTH MAIN PIPELINE, WELDED STEEL PIPES FOR THICK-WALLED HIGH-STRENGTH MAIN PIPELINE AND METHOD OF WELDED STEEL PIPE MANUFACTURING Russian patent published in 2019 - IPC C21D8/02 C22C38/58 C21D9/46 C21D8/10 

FIELD: metallurgy.

SUBSTANCE: disclosed is hot-rolled steel sheet for thick-walled high-strength main pipeline, having high strength class API X60 - X80, yield point YS higher than 415 MPa, tensile strength TS above 520 MPa and resistance to brittle fracture. Proposed are a welded steel pipe made of hot-rolled steel sheet and a method of manufacturing a welded steel pipe. To achieve technical result, hot-rolled steel sheet has chemical composition in wt%: C 0.02–0.20, Mn 0.80–2.10, Si 0.01–0.50, P: 0.034 or less, S 0.0050 or less, Nb 0.01–0.15, Ti 0.001–0.030, and Al 0.001–0.080, Fe is the rest and by-impurities, wherein the sheet has a microstructure, in which the main phase is a conversion structure at continuous cooling (Zw) and in which grain {001}_α in the plane, the normal direction of which is the sheet width direction, is a portion of area of 10 % or less and has a total size of 10 mcm or less, expressed as the average grain diameter of the area share, wherein the hot-rolled steel sheet has a tensile strength of 520 MPa or more and in the drop weight test (DWTT) temperature at which the percentage of ductile failure reaches 85 % is -25 °C or lower.

EFFECT: disclosed is hot-rolled steel sheet for thick-walled high-strength main pipeline.

7 cl, 3 tbl