1180 MPa-grade precipitation strengthened hot rolled ultra-high-strength steel and manufacturing method thereof

Abstract

Provided are 1180 MPa-grade precipitation strengthened hot rolled ultra-high-strength steel and a manufacturing method thereof. The steel is prepared from, by weight, C 0.10-0.20%, Mn 1.5-2.0%, P smaller than or equal to 0.015%, S smaller than or equal to 0.005%, Al 0.02-0.08%, N smaller than or equal to 0.005%, O smaller than or equal to 0.003%, Ti 0.10-0.20%, Nb 0.03-0.06%, V 0.20-0.40% and the balance Fe and inevitable impurities, and meanwhile the conditions required to be met are as follows: the sum of Nb and Ti is greater than or equal to 0.16% but is smaller than or equal to 0.23%, and (Ti-3.42N-3S)/4+V/4.24+Nb/7.74 is greater than or equal to 0.065% but is smaller than or equal to 0.15%. The microstructure of the steel is ferrite, bainite and nanoscale precipitation carbide, wherein the equivalent grain size of the ferrite is smaller than or equal to 5 microns, the width of bainite battens is smaller than or equal to 0.5 micron, the tensile strength of the bainite battens is greater than or equal to 1180 MPa, the elongation is greater than or equal to 15%, the hole expansion rate is greater than or equal to 30%, and excellent strength, plasticity and burring matching are shown.

Description

technical field [0001] The invention belongs to the field of hot-rolled high-strength steel, and specifically relates to a 1180MPa-level precipitation-strengthened hot-rolled ultra-high-strength steel and a manufacturing method thereof. Background technique [0002] In the field of automobiles, especially passenger cars, high-strength thinning or lightweight automobile structures have become an important research direction for international automobile manufacturers. Different from the high-strength thinning and lightweight trends of passenger cars, the lightweight work of commercial vehicles is progressing very slowly. The main reason is that commercial vehicles are generally overloaded seriously, and the designers of commercial vehicles have a large design margin for the structure; at the same time, the commercial vehicles themselves and the load capacity are large, and sometimes the rigidity is difficult to guarantee after thinning with high-strength steel; On the one han...

AI Technical Summary

Problems solved by technology

Single ferrite or bainite structure has high hole expansion performance, but its strength is relatively low, and it is difficult to achieve ultra-high strength; while ferrite and martensite structure have low yield ratio and Higher strength, but due to the large difference in properties between ferrite and martensite, its hole expandability is the worst among high-strength steels of the same strength level and different structure types

In other words, it is often difficult to have both high strength and high hole expandability

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