Toughness improvement in hot rolled HSLA steel plates through asymmetric rolling

Asymmetric hot rolling and conventional hot rolling were applied to a HSLA steel in order to improve the impact toughness of thick-gauge hot rolled plates. The asymmetric rolling condition was introduced by applying mismatched roll diameters. The diameter ratio between big and small rolls was 1.25. The rolling temperatures were between 900 °C and 1150 °C. The results show that asymmetric rolling produced a smaller average grain size at the centre layer of the hot rolled plate than symmetric rolling and brought a through thickness texture change. The impact toughness was increased and the toughness anisotropy was reduced in the asymmetric hot rolled plate in the ductile to brittle transition temperature range. The improved impact toughness in the asymmetric hot rolled plate is related to the fine grain structure and the lower toughness anisotropy is related to the reduced α-fibre texture.