Mechanical Properties Distribution through the Thickness of Heavy Gauge Steel Plate Rolled in Intercritical Region

Abstract

Controlled rolling in intercritical region (austenite and ferrite two phase region) is one of the effective processes both to strengthen the steel plate and to improve toughness. In this study mechanical properties of experimentally controlled rolled heavy thickness steel plate were investigated. In case of heavy thickness steel plate, toughness enhancement by controlled rolling in intercritical region was small, because ferrite grain refinement is insufficient due to limitation of amount of thickness reduction in controlled rolling. In addition, Charpy transition temperature at the 1/4 t position increased as lowering the finishing rolling temperature in intercritical region. Toughness dependence on thickness position was considered in terms of texture. The main component of texture at 1/2 t position is {001} <110> and {113} <110>, whereas that at 1/4t position is {110} <001>, which is formed by shear strain in controlled rolling. The effect of texture on toughness difference in thickness position and anisotropy was analyzed using crystallite orientation distribution function. Calculated brittleness parameter was evaluated, which is relationship between direction of stress axis that induces brittle fracture and (100) cleavage plane distribution. It was revealed that texture is an important factor to control the toughness of heavy thickness controlled rolled steel plates.