Evaluation of Secondary Steelmaking Slags and Their Relation with Steel Cleanliness
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CARDOSO DA ROCHA is with the PPGE3M (Graduate Program in Mines, Metallurgical and Materials Engineering), UFRGS (Federal University of Rio Grande do Sul), Technology Center, Porto Alegre, Rio Grande do Sul 91501-970, Brazil, and also with LaSid (Ironmaking and Steelmaking Laboratory), UFRGS (Federal University of Rio Grande do Sul), Technology Center. Contact e-mail: [email protected] JULIO A.M. PEREIRA is with the LaSid (Ironmaking and Steelmaking Laboratory), UFRGS (Federal University of Rio Grande do Sul), Technology Center. AYUMI YOSHIOKA is with the Research and Development Department, Gerdau Charqueadas, Charqueadas, Rio Grande do Sul, 96745-000, Brazil. WAGNER V. BIELEFELDT and ANTOˆNIO C.F. VILELA are with the LaSid (Ironmaking and Steelmaking Laboratory), UFRGS (Federal University of Rio Grande do Sul), Technology Center. Manuscript submitted May 30, 2016. Article published online February 24, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
The steel industry has evolved considerably in recent decades. In the area of inclusions engineering, the application of computational thermodynamic software has become fundamental for the study of slags and inclusion cleanliness of specials steels.[1] Inclusion engineering deals with the control, size distribution, composition, and physical properties of nonmetallic inclusions (principally oxides and sulfides) formed in liquid steel during the process of refining and solidification.[2] Research[3–7] related to slags and inclusion cleanliness is the subject of a large effort to achieve production of high-purity steels. The formation of nonmetallic inclusions during steelmaking is an inevitable physical–chemical consequence through metallurgical reactions,[8] and refining slags have great effects in the efficiency of inclusion removal and steel cleanliness.[9] Part of the steps of inclusion engineering occur during refining.[10] Therefore, inclusion removal can be performed in the ladle (secondary metallurgy) or still in the tundish and mold (continuous casting) by migration of inclusion at the slag/steel interface, separation at the interface, and inclusion dissolution by slag.[11,12] A partnership between industry and academia made it possible to link melt shop data with specific research tools, such as ASPEX equipment and computational thermodynamics, that when properly used can bring important results related to steel quality (inclusion population, inclusion chemical composition, and solid and liquid fraction of slags and their viscosities), helping the steelmaker to achieve better products. In order to observe the removal efficiency of nonmetallic inclusions through slag, this work carried out a thermodynamic study in a group of two slags, namely, slags A and B, with chemical compositions provided from an industrial plant. This thermodynamic analysis was based on software FactSage (version 6.4) to determine the values of effective viscosity, solid fraction, composition of the liquid fraction, and slag saturation degree. More information about the software and its databas
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