Inclusion characterisation – tool for measurement of steel cleanliness and process control: Part 1

Abstract

Owing to increasing demand for high surface and internal quality finished steel products, it is imperative to study the factors that limit the production of such steels. In particular, non-metallic inclusions affect steel cleanliness and cause defects leading to worsening of desired mechanical properties and service life of steel products. Other detrimental effects of inclusions are poor steel castability often resulting in slab downgrades and rejections, increased costs associated with recycling of liquid steel and refractories, and even shut down of the caster. Inclusion engineering is thus important to achieve process and quality control on a daily production basis. This article, in two parts, addresses inclusion characterisation as a tool for understanding and improving process conditions, minimising nozzle clogging and reducing sliver rejections in Ti stabilised ultra low carbon steels, Ca treated low carbon Al killed steels and advanced high strength steels. The paper begins with a survey of techniques followed by examples of use of techniques to resolve steelmaking and casting issues that affect quality of steel. Part I explains the use of an automated scanning electron microscope to correlate inclusion data with industrial process conditions. Examples include effect of different samplers, influence of ferroalloy quality and temperature control practices, ratio of elemental chemistries, ladle stirring etc. on quality of steel.