Evolution of texture in ultra-fine grained ferrite through warm-rolling and intercritical annealing

Abstract

The ferrite grain size refining is the unique mechanism for increasing both mechanical strength and formability of steels. Steel with an ultra-fine ferrite grained structure must show a good relation between mechanical strength, ductility and toughness, while the low carbon content enhances good welding characteristics. The objective of this work is to investigate the influence of warm rolling on the evolution of texture in a microalloyed low carbon-manganese (0.11%C, 1.41%Mn, 0.028%Nb and 0.012%Ti) steel with ultra-fine grains produced through out quenching, warm rolling, followed by sub and intercritical annealing. The evolution of restoration process recovery and recrystallization - was followed by optical and scanning microscopy. After subcritical annealing, the microstructure was formed by spheroidal iron carbides and a ferritic recovered matrix. Otherwise, after intercritical annealing, the microstructure was composed mainly by ultrafine grain polygonal ferrite, MA (martensite-austenite) constituent and carbides. The mechanical behaviour of the steel was evaluated using tensile tests. The mechanical properties have been correlated with the evolution of texture in the ultra-fine grained ferrites.