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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.

The research presented in this series of articles is a summary of inclusion characterisation techniques in routine to support the process improvement needs of internal customers of ArcelorMittal Global R&D, East Chicago. This paper highlights the use of characterisation techniques including total oxygen analysis, cathodoluminescence microscope on remelt buttons and clogging materials, and pulse discrimination analysis to study steelmaking and casting issues that affect productivity and quality of steel at ArcelorMittal USA. Use of cathodoluminescence microscope for examination of remelt buttons to correlate the nature of inclusions to castability for Ca treated steel grades is explained. Example results of application of total oxygen analysis and pulse discrimination analysis on Ti stabilised ultra low carbon, advanced high strength steels and transformation induced plasticity steels are shown. Formation of spinel inclusions and their impact on castability for desulphurised non-Ca treated versus Ca treated grades is also discussed.

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Improving steelmaking and casting processes to adapt to the requirements of internal and external customers involves continuous monitoring and evaluation of existing and development of new steel refining practices. Internal quality control of semifinished products requires tools that can correlate product defects to process anomalies. This article focuses on use of techniques such as measurement of complete steel and slag chemistry, inclusion analysis, process analysis and thermodynamics to assess the influence of process conditions on product properties. Examples from both long and flat products, including low carbon aluminium killed steels, medium carbon aluminium killed steels, advanced high strength steels and free machining steels, are presented to explain the benefit of using these tools to understand the process conditions necessary for clean steelmaking and thus improve product quality.