Research And Development Of EH40High Strength Shipbuilding Steel

In order to adapt to the needs of development of marine industry, the shipbuilding plate，which owns high strength, good low-temperature impact toughness and good extensionperformance，is developed. Through composition design, simulating smelting and simulatingrolling, the EH40shipbuilding plates are produced in the lab. In two times of simulating rolling，the metallurgical structure and properties of different kinds of rolling schedules are analyzed andthe optimum process of producing EH40shipbuilding plates is found which the variousperformances meet the requirement of GB. The main conclusions of this paper are given asfollows.(1) The composition of EH40shipbuilding plates are designed and then simulating smeltingin vacuum induction furnace. Three EH40steel ingots which the composition meet the targetrequirement are got. The composition are average for:0.081wt%C,0.309wt%Si,1.332wt%Mn,0.0060wt%P,0.0040wt%S,0.0250wt%Als,0.034wt%Nb,0.014wt%Ti.(2) The four different kinds of processes in two times rolling are compared and analyzed,and the optimum process could be found that1200℃for heating temperature, and1180℃for open rolling temperature, and the thickness of plate is rolled from170mm to40mm bymulti-channel times deformation in recrystallization region and from40mm to15mm innon-recrystallization region, and980℃for waiting temperature, and830℃for finishingrolling temperature, and12℃/s for cold speed with laminar cooling, and600℃for the finalcooling temperature.(3) The properties of EH40shipbuilding plates which produced by the optimum processmeet the requirement of GB very well. The yield strength are540MPa both in crosswise andlengthways, and the tensile strength are620MPa in crosswise and622MPa in lengthways, andthe elongation are25%in crosswise and29.5%in lengthways, and the Akv are196J at-20℃,184J at-40℃,159J at-60℃in the crosswise and243J at-20℃,259J at-40℃,223J at-60℃in the lengthways. And the microstructures are main polygons or quasi polygons ferrite, a smallacicular ferrite and pearlite. Fracture morphology of low-temperature impact are all typicalductile fracture.