HOT ROLLED STEEL SHEET WITH HIGH HOLE EXPANSION RATIO AND MANUFACTURING PROCESS THEREOF

摘要

A hot rolled steel sheet having a chemical composition comprising, in weight %: 0.15% ≤ C ≤ 0.20%, 0.50% ≤ Mn ≤ 2.00%, 0.25% ≤ Si ≤ 1.25%, 0.10% ≤ Al ≤ 1.00%, with 1.00% ≤ (Al+Si) ≤ 2.00%, 0.001% ≤ Cr ≤ 0.250%, P ≤0.02%, S ≤ 0.005%, N ≤ 0.008%, and optionally one or more elements among: 0.005% ≤ Mo ≤ 0.250%, 0.005% ≤ V ≤ 0.250%, 0.0001% ≤ Ca ≤ 0.003% and 0.001% ≤ Ti ≤ 0.025%, the remainder being Fe and unavoidable impurities, and wherein the microstructure comprises in surface fraction, ferrite and bainite, the sum of which being greater than 5% and strictly lower than 20%, the remainder consisting of tempered martensite.