HIGH-STRENGTH HOT-ROLLED STEEL SHEET

摘要

This high-strength hot-rolled steel plate contains specific amounts of C, Si, Mn, Al, V and also Ti and/or Nb so as to fulfill C−12(V/51+Ti/48+Nb/93)>0.03, and the rest consists of iron and unavoidable impurities. Ferrite is the main microstructure, the remaining microstructure is one or more selected from the group consisting of bainite, martensite and retained austenite, wherein the average particle diameter of precipitated carbides (the total content of V, Ti and Nb is 0.02% or greater) in the ferrite is less than 6 nm.

主权项

1. A high-strength hot-rolled steel sheet, comprising, by mass %:
C. 0.05 to 0.20%; Si. 2.0% or less; Mn. 1.0 to 2.5%; Al. 0.001 to 0.10%; V. 0.0005 to 0.10%; iron; and inevitable impurities,and further comprising at least one of:
Ti. 0.02 to 0.20% and Nb. 0.02 to 0.20%, wherein: the steel sheet has a microstructure comprising, by area ratio based on the total microstructure: ferrite. 50 to 95%; and one or more microstructures selected from the group consisting of bainite, martensite, and retained austenite; an average particle size of precipitated carbides present in the ferrite is less than 6 nm; a total content of V, Ti, and Nb forming the precipitated carbides is 0.02% or more; and the steel sheet satisfies the following Expression 1:
C−12×(V/51+Ti/48+Nb/93)>0.03,where element symbols in the Expression 1 correspond to mass %.