Inclusion Evaluation for Calcium Treated Steel and Its Relation to Caster Behavior in Industry

Abstract

Undesirable solid oxides and sulphides, known as inclusions, are an inherent product of the steelmaking process that can clog the steel flow during casting. Caster operators can break up the clogged material to improve flow, but this reduces steel quality and yield. Modifying these inclusions using calcium treatment and its effects on industrial processing conditions are the focus of this study. To effectively improve calcium treatment, experimental and industrial data are required to develop models to predict inclusion behaviour. The advantage of experimental testing is that the precise control of chemistry, temperature, alloying elements, and sampling can help identify the effects of each variable. The difficulty, however, is correlating experimental results to real-time industrial processing, where these variables are difficult to control individually. In industry, indirect observations of caster behaviour may give an idea of the effectiveness of the treatment, but this is after the fact. In this study, liquid steel samples were taken at different processing steps without any modification to the process itself to ensure normal shop conditions. The inclusion analysis was conducted using an automated Scanning Electron Microscope (SEM) and AZtech feature analysis software to determine inclusion characteristics, including population, composition, and size. This study shows 8 sequential calcium-treated steel heats in an industrial setting and their associated clogging behaviour during a cast. The study indicated that a few heats with undermodified alumina inclusions immediately or subsequently affected the casting process leading to a severe clogging event.