HIGH STRENGTH HOT ROLLED STEEL SHEET AND METHOD FOR PRODUCING THE SAME

摘要

A hot rolled steel sheet includes a composition including: C: 0.03% to less than 0.07%; Si: 0.3% or less; Mn: 0.5% to 2.0%; P: 0.025% or less; S: 0.005% or less; N: 0.0060% or less; Al: 0.1% or less; Ti: 0.07% to 0.11%; and V: 0.08% to less than 0.15% on a mass percent basis, such that Ti and V contents satisfy:;0.18≦Ti+V≦0.24;(where Ti and V are contents of the elements (by mass %)), the balance including Fe and inevitable impurities, a matrix having a ferrite phase with an area ratio of 95% or more; and a structure where fine carbide is dispersedly precipitated in the matrix, the fine carbide containing Ti and V has an average particle size of less than 10 nm, and a volume fraction of the fine carbide is 0.0020 or more, wherein the steel sheet has a tensile strength of 780 MPa or more.

主权项

1. A high strength hot rolled steel sheet, comprising:
a chemical composition comprising:
C: 0.03% or more to less than 0.07%;Si: 0.3% or less;Mn: 0.5% or more to 2.0% or less;P: 0.025% or less;S: 0.005% or less;N: 0.0060% or less;Al: 0.1% or less;Ti: 0.07% or more to 0.11% or less; andV: 0.08% or more to less than 0.15% on a mass percent basis, such that Ti and V contents satisfy Formula (1):
0.18≦Ti+V≦0.24   (1)(where Ti and V are respective contents of the elements (by mass %)),
the balance comprising Fe and inevitable impurities, a matrix having a ferrite phase with an area ratio of 95% or more with respect to an overall structure; and a structure where fine carbide is dispersedly precipitated in the matrix, the fine carbide containing Ti and V has an average particle size of less than 10 nm, and a volume fraction of the fine carbide is 0.0020 or more with respect to the overall structure, wherein the high strength hot rolled steel sheet has a tensile strength of 780 MPa or more.