Thermomechanically controlled rolled higher strength microalloyed structural plate steels

摘要

A series of Nb microalloyed steels weresubjected to industrial scale thermomechanical controlledrolling to a range of plate thicknesses with a view todeveloping a 450Mpa yield strength structural plate steel. Thebase steel was of a low C 1.6%Mn-0.04%Nb-0.015%Ti typewith variants alloyed with Cu and Ni or Mo. The mechanicalproperties are discussed in terms of the chemical composition,rolling conditions and microstructure. In particular the yield totensile strength ratio is discussed. The application of a lowtemperature ageing heat treatment to the Mo bearing steelproduced a marked increase in yield strength of about 100Mpaassociated with age hardening and a change from continuousto discontinuous yielding phenomenon.