Forge and heat-treatments in micro-alloyed steels

Abstract

Improved designs, mostly for light weight component manufacturer have been improvement of forging designs and heat-treatment techniques. Low temperature precipitation strengthening and resistance to austenite grain size coarsening at reheat temperature for forging have been property improvement technique in these microalloyed steels. Studies of peak strain and flow stress at 1123-1423 K have showed increase in peak strain, peak stress and increment in mean flow stress in austenite phases in presence of vanadium. Partial vanadium alloying (1part V substitute for 2 parts Mo) by substituting molybdenum has improved hardenability properties of conventional steels. Ultrafine grained steels have showed strain hardening effects from severe deformation by equal channel angular pressing (ECAP) followed by annealing. The strain induced precipitation of nano-metric sizes have pinned dislocations for strain hardening. Estimation of remaining life for reactor components have been done by simulated experiments under similar conditions as the service exposure. Vanadium in ferritic stainless steel has showed competitive performance, e.g. chloride environment. This has showed equivalent effects like nickel. In welding of microalloyed steel inter-critical grain coarsened heat affected zone (IC GC HAZ) has martensite austenite (M-A) blisters to yield poorest toughness.