High-strength structural steel having excellent cold bendability, and manufacturing method therefor
AssigneePosco
InventorsJae-Young CHO, Il-Cheol YI, Sang-Deok KANG
Life of this patent
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Abstract
A high-strength structural steel having excellent cold bendability, according to one embodiment of the present invention, comprises, by wt %, 0.02-0.1% of C, 0.01-0.6% of Si, 1.7-2.5% of Mn, 0.005-0.5% of Al, 0.02% or less of P, 0.01% or less of S, 0.0015-0.015% of N, and the balance of Fe and other inevitable impurities, wherein an outer surface layer part and an inner central part thereof are microstructurally divided in a thickness direction, the surface layer part can comprise tempered austenite as a matrix structure, and the central part can comprise bainitic ferrite as a matrix structure.
Claims15
A high-strength structural steel having excellent cold bendability, comprising:
- by weight %, 0.02-0.1% of C, 0.01-0.6% of Si, 1.7-2.5% of Mn, 0.005-0.5% of Al, 0.02% or less of P, 0.01% or less of S, 0.0015-0.015% of N, a balance of Fe, and other unavoidable impurities, wherein the high-strength structural steel is microstructurally divided into an outer surface layer part and an inner central part in a thickness direction,
- wherein the surface layer part comprises tempered bainite as a matrix structure, and
- the central part comprises bainitic ferrite as a matrix structure.
A method of manufacturing a high-strength structural steel having excellent cold bendability, the method comprising:
- reheating a slab at a temperature ranging of 1050 to 1250° C., the slab including, by weight %, 0.02-0.1% of C, 0.01-0.6% of Si, 1.7-2.5% of Mn, 0.005-0.5% of Al, 0.02% or less of P, 0.01% or less of S, 0.0015-0.015% of N, a balance of Fe, and other unavoidable impurities,
- rough rolling the slab in a temperature range of Tnr to 1150° C. to provide a rough-rolled bar,
- first cooling the rough-rolled bar to a temperature ranging from Ms to Bs° C. at a cooling rate of 5° C./s or more,
- maintaining a surface layer part of the first cooled rough-rolled bar to be reheated to a temperature ranging from (Ac1+40° C.) to (Ac3−5° C.) by heat recuperation,
- finish rolling the rough-rolled bar subjected to a heat recuperative treatment, and
- second cooling the finish rolled steel to a temperature of Bf ° C. or less at a cooling rate of 5° C./s or more.
Dependencies are inferred from the claim text.