Lean 3rd generation hot-rolled steel strip and method of manufacturing the same

Abstract

A hot-rolled steel strip, having a yield strength of at least 600 MPa and an ultimate tensile strength of at least 1200 MPa, comprising a composition consisting of, in terms of weight percentages, wt.%: C 0.15 - 0.4, Mn 1 - 3, Si 0 - 1, Al 0.3 - 1.5, Ni 1 - 3, Mo 0.2 - 1, Ti 0 - 0.2, Nb 0 - 0.1, V 0 - 0.3, B 0 - 0.005, Ca 0 - 0.006, remainder being Fe and inevitable impurities, wherein P 0 - 0.05, S 0 - 0.01, N 0 - 0.01, and wherein the sum of Mn and Ni is 3 - 6 wt. The microstructure of the strip consist of >50% of fresh and tempered martensite and 5 - 20% of retained austenite, while the retained austenite carbon content is 0.5 - 1 wt %, and wherein a balance is intercritical ferrite.

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