STEEL PLATE HAVING HIGH STRENGTH AND EXCELLENT LOW-TEMPERATURE IMPACT TOUGHNESS AND METHOD FOR MANUFACTURING THEREOF

    公开(公告)号:EP4056725A1

    公开(公告)日:2022-09-14

    申请号:EP20884059.5

    申请日:2020-10-26

    申请人: POSCO

    摘要: Provided are high strength steel having excellent low-temperature impact toughness, and a method for manufacturing same. The high strength strength steel having excellent low-temperature impact toughness of the present invention comprises, in percentage by weight, 0.04-0.12% of carbon(C); 0.1-0.5% of silicon(Si); 1.2-2.5% of manganese(Mn); 0.01% or less of phosphorus (P); 0.01% or less of sulfur(S); 0.01-0.08% of Aliminum(Al); 0.01-0.08% of niobium(Nb); 0.01-0.5% of chromium(Cr); 0.4-1.0% of nickle(Ni); 0.5% or less of copper(Cu); 0.01-0.5% of molybdenum(Mo); 0.05% or less of vanadium(V); 0.005-0.02% of titanium(Ti); 0.001-0.0025% of boron(B); 0.002-0.01% of nitrogen(N); the balance being Fe and inevitable impurities, wherein the high strength steel has a Ceq value less than 0.55 represented by Relational expression 1 below, has an internal microstructure consisting of 80% or more of banitic ferrite and balance granular bainite in an area fraction at a point of 1/4t of the thickness thereof, and has an aspect ratio of a prior austenite grain boundary of 3.0 or greater and a thickness of 60 mm or greater and 100 mm or less.