HIGH STRENGTH STEEL PLATE AND MANUFACTURING METHOD THEREOF

摘要

A high strength steel plate having excellent anti-chipping, low YP, high BH, and high El, and further having reduced material variability in the coil, and a manufacturing method thereof are provided. This high strength steel plate contains, in mass%, C: more than 0.015 and less than 0.100,Si: less than 0.50, Mn: more than 1.0 and less than 2.0,P: 0.05 or less,S: 0.03 or less,soluble Al: 0.01-0.3,N: 0.005 or less,Cr: less than 0.35,B: 0.0010-0.0050,Mo: less than 0.15,Ti: less than 0.030, fulfills 2.1@[Mneq]@3.1, the remaining part being iron and unavoidable impurities, and has ferrite and a second phase, wherein the volume ratio of the second phase is 2.0-12.0%, the volume ratio of martensite and residual gamma in the second phase is 60% or higher, the number of carbides present in the ferrite particles and having an aspect ratio of 3.0 or less and a diameter of 0.25-0.90mum is 10000/mm2 or less. Represented by [Mneq]=[%Mn]+1.3[%Cr]+3.3[%Mo]+8[%P]+150B*, with B*=[%B]+[%Ti]/48×10.8×0.9+[%Al]/27×10.8×0.025, when B*>=0.0022, then B* is set to B*=0.0022.