METHOD OF PRODUCTION STRIPS FOR PIPES OF MAINS Russian patent published in 2010 - IPC C21D8/02 C22C38/08 C22C38/42 

FIELD: metallurgy.

SUBSTANCE: invention refers to production of strip steel for mains of up to 1420 mm diametre, not less, than 20 mm and not more, than 40 mm thickness. Steel of certain chemical composition is melt in a converter, continuously cast to work pieces, subject to austenisation at temperature 1170-1220°C during 4-8 hours and preliminary deformed with summary reduction ratio 40-60 % and with specified swaging not less, than 14 % per run at temperature 1000-900°C; further a semi-finished rolled product is subject to accelerated cooling by two runs in the installation of accelerated cooling (IAC); notably, canting of the semi-finished rolled product is performed after the first run. Successively there are performed sub-cooling in air at 3-5 sec/mm, finish deformation at temperature 820-730°C with summary reduction ratio 40-50 % and not less, than 12 % per run, cooling in IAC to temperature 500-350°C, retarded cooling in a caisson to temperature not above 150°C and cooling in air.

EFFECT: upgraded strength properties and resistance to brittle fracture at temperature to -20°C at maintaining high processability with the ratio σ_T/σ_T≤0,90.

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