THE MANUFACTURING METHOD FOR100KG/MM2 HIGH STRENGTH THICK STEEL PLATE WITH EXCELLENT HIGH HARDNESS AND LOW TEMPERATURE THOUGHNESS

摘要

PURPOSE: Provided is a method for manufacturing superhigh tensile strength steel plates (tensile strength: 100kg) having high hardness and ductility at low temperature for the application to bulletproof materials. CONSTITUTION: The superhigh tensile strength steel plate is manufactured by heating an ingot comprising C 0.10-0.19wt.%, Si 0.15-0.35wt.%, Mn 0.10-0.40wt.%, P 0.012wt.% or less, S 0.005wt.% or less, Ni 2.75-3.50wt.%, Cr 1.30-1.80wt.%, Mo 0.35-0.45wt.%, V 0.010-0.025wt.%, a balance of Fe and inevitable impurities at the rate of 50-70deg.C/Hr; rolling the ingot in the form of bloom; furnace cooling the bloom; rolling the bloom in a plate mill; quenching the plate in the temperature range of 900 to 920deg.C; and then tempering it in the temperature range of 470 to 580deg.C.