Título

“CHARACTERISTICS OF MOULD FLUX FILMS FOR CASTING MC AND LC STEELS”

“CHARACTERISTICS OF MOULD FLUX FILMS FOR CASTING MC AND LC STEELS”

Autoria

Li, Zushi; Mills, Ken; Bezerra, Maria Carolina Campello

DOI

10.5151/2594-5300-0028

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Resumo

The characteristics of mould flux films developed while casting MC and LC steels taken from a continuous casting mould have been investigated. These characteristics include appearance, porosity, crystallinity, mineralogical phases, cross-sectional microstructure, and element distribution and thickness of solid/liquid layers. The following are discussed: (i) the effect of chemical compositions of mould fluxes on the characteristics of the films and (ii) the mechanisms responsible for crystallisation and porosity formation. Two mould flux films for casting MC and LC steel grades were taken at around 300 mm from the top of the mould in the end of casting. The crystallinity of flux films was investigated by direct observation of optical microscope and SEM. XRD was used to detect the mineralogical phases in the mould flux films. The microstructure and cross-sectional element distribution were studied by SEM/SEM-EDS. The porosity and appearance of flux films were determined by imagine analysis system. It was verified that the horizontal heat transfer between shell and mould is controlled by (i) thickness of the solid slag film and (ii) the surface roughness (equivalent to an air gap) formed when the initial glassy slag film crystallises. Both the surface roughness and the crystalline fraction (90%) of the slag film for casting MC grades were greater than those for casting LC grades. The crystalline fraction can be related to the flux composition by using the parameter “modified NBO/T”. The mechanism for the crystallisation and porosity formation of the flux films is discussed.

 

The characteristics of mould flux films developed while casting MC and LC steels taken from a continuous casting mould have been investigated. These characteristics include appearance, porosity, crystallinity, mineralogical phases, cross-sectional microstructure, and element distribution and thickness of solid/liquid layers. The following are discussed: (i) the effect of chemical compositions of mould fluxes on the characteristics of the films and (ii) the mechanisms responsible for crystallisation and porosity formation. Two mould flux films for casting MC and LC steel grades were taken at around 300 mm from the top of the mould in the end of casting. The crystallinity of flux films was investigated by direct observation of optical microscope and SEM. XRD was used to detect the mineralogical phases in the mould flux films. The microstructure and cross-sectional element distribution were studied by SEM/SEM-EDS. The porosity and appearance of flux films were determined by imagine analysis system. It was verified that the horizontal heat transfer between shell and mould is controlled by (i) thickness of the solid slag film and (ii) the surface roughness (equivalent to an air gap) formed when the initial glassy slag film crystallises. Both the surface roughness and the crystalline fraction (90%) of the slag film for casting MC grades were greater than those for casting LC grades. The crystalline fraction can be related to the flux composition by using the parameter “modified NBO/T”. The mechanism for the crystallisation and porosity formation of the flux films is discussed.

Palavras-chave

Mould flux, Slag Films.

Mould flux, Slag Films.