Crystallisation of slag films formed in continuous casting

Lee, Courtney; Nuortie-Perkkiö, S.; Valadares, Cláudio Antônio Goulart; Richardson, M.J.; Mills, K C

doi:10.1179/irs.2001.28.5.412

Cited by 9 publications

(12 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Slower cooling therefore allowed more time for crystal formation during solidification representing cooling-rate-2 (figure 3.6) (Courtney et al, 2001). Crystals found next to the steel shell are much bigger compared with the crystals found closer to the mould.…”

Section: Cooling Rate 3 -Crystalline Structurementioning

confidence: 99%

Heat transfer through mould flux with titanium oxide additions

Bothma¹,

Pistorius²

2007

Ironmaking & Steelmaking

View full text Add to dashboard Cite

KEY WORDS:continuous casting, crystallisation, cuspidine, heat transfer, heat barrier, mould flux, perovskite, slag, stainless steel, titanium. Mould powders are synthetic slags that contain mixtures of silica (SiO 2 ), lime (CaO), particles were also found in a slag rim sample taken during the industrial casting of 321-titanium stabilised stainless steel using SPH-KA1 mould powder. -HEAT TRANSFER THROUGH MOULD FLUX WITH TITANIUM OXIDE ADDITIONS - J.A. BOTHMA -MASTER OF ENGINEERING (METALLURGY) -UNIVERSITY OF PRETORIA -2006iv Further investigations of the crystalline flux layers showed the entrapment of many tiny gas bubbles during solidification. This porous structure acted as a thermal heat barrier limiting horizontal heat transfer. Experimental testing on 3.0 and 6.0mm flux thickness revealed that the overall thermal conductivity of mould flux decreased as the flux porosity increased. Larger amounts of gas entrapment (in the solid flux structure) resulted in higher thermal resistances which ultimately reduced the heat transfer capabilities of the flux.A second heat barrier, which has a far more dominating effect on the overall heat transfer, is created on mould surface during flux solidification. This thermal contact resistance is also found to be the result of entrapped gas bubbles. Experimental results concluded that the effect of titanium pickup on heat transfer is primarily overshadowed by the larger effect of the thermal contact resistance that is formed during mould flux solidification. The contact resistance in combination with gas entrapment in the solid crystalline structure is considered to be the key factors preventing horizontal heat transfer during continuous casting. -HEAT TRANSFER THROUGH MOULD FLUX WITH TITANIUM OXIDE ADDITIONS - J.A. BOTHMA -MASTER OF ENGINEERING (METALLURGY) -UNIVERSITY OF PRETORIA -2006v ACKNOWLEDGEMENTS

show abstract

Section: Cooling Rate 3 -Crystalline Structurementioning

confidence: 99%

Heat transfer through mould flux with titanium oxide additions

Bothma¹,

Pistorius²

2007

Ironmaking & Steelmaking

View full text Add to dashboard Cite

show abstract

“…Reasonable estimates can be obtained using partial molar volumes (V) for the various slag constituents but special procedures are There are few reported data for the density of mould slags. Values have been reported for the glassy phase [14][15][16] the liquid state 17,18) and for some slag films.…”

Section: Density (ρ) Thermal Expansion Coefficient (α)mentioning

confidence: 99%

Calculation of Physical Properties for Use in Models of Continuous Casting Process-Part 1: Mould Slags

et al. 2016

View full text Add to dashboard Cite

Physical properties of both steels and mould slags are needed as input data for the mathematical modelling of the continuous casting process. Routines for calculating the properties of mould slags and for estimating steel properties have been developed and are described in Parts 1 and 2, respectively. Many mould powders, with differing compositions, are used in casting practice and their properties vary significantly. Reliable models have been developed to calculate these property values as a function of temperature from their chemical composition since this is available on a routine basis. Models have been developed to calculate the following properties: heat capacities, enthalpies, thermal expansion coefficient, density, viscosity, thermal conductivity and surface tension. Solid mould slags can exist as glassy or crystalline phases or as mixtures of the two (i.e. slag films) and the properties for the various phases can vary considerably; methods have been developed to calculate property values for these various states. The software used to calculate the properties is available via the link (i) http://www.mxif.manchester.ac.uk/ resources/software (ii) https://sites.google.com/site/shyamkaragadde/software/thermophysical-properties.KEY WORDS: mould slags; continuous casting; thermophysical properties; steels.carbonates decompose to form CO 2 (g) (ii) Carbon particles in the powder start to oxidise (iii) the oxide components sinter and (iv) then melt when the carbon is consumed, and molten globules mix to form a molten slag pool. Slag from the molten pool then infiltrates into the channel between the steel shell and the mould to form a slag film (Fig. 1); this consists of (i) a liquid layer (ca. 0.1 mm thick) and (ii) a solid layer (ca. 1-2 mm thick). The heat flux between shell and mould is determined, principally, by the thickness of this solid layer (and the amount of crystalline phase present) and the lubrication supplied to the shell is determined by the thickness of the liquid layer. Lubrication involves the following properties: viscosity (η), density (ρ) surface tension (γ) and break (or solidification) temperature (T br ). The heat flux involves the following properties of the mould slag: thermal conductivity (k), T br , the fraction of crystalline phase formed in the slag film (f crys ) and the optical properties of the mould slag.The objective of this study was to develop routines to provide reliable values of the thermo-physical properties of mould slags from their chemical compositions, for input into the model of the continuous casting process. The other aim was to make these routines available as Excel software; open access is provided at (i) http://www.mxif.manchester. ac.uk/resources/software (ii) https://sites.google.com/site/ shyamkaragadde/software/thermophysical-properties. Effect of Structure on Slag PropertiesThe properties of slags are principally determined by the structure of the slag. In silicate slags the basic building ISIJ International, Vol. 56 (2016)block is the Si-O tetrahedron, i...

show abstract

“…Crystallisation occurs in the same temperature region as T d and is accompanied by a sharp decrease in α. 48) There are no density values available for mould slags for T > T d and data are needed.…”

Section: Dissolution Of Al2o3mentioning

confidence: 99%

“…The experimental data for the density 44,[49][50][51][52][53][54][55] and linear expansion coefficient 43,48) are summarised in Table 2. The densities can be estimated from partial molar relations involving the molar volume (V) but V for the SiO 2 and Al 2 O 3 components are expressed as polynomials 117) indicating that the structure does have some effect on the density of the slag.…”

Section: Density (ρ) and Thermal Expansion Coefficient (α)mentioning

confidence: 99%

See 1 more Smart Citation

Structure and Properties of Slags Used in the Continuous Casting of Steel: Part 1 Conventional Mould Powders

Mills

2016

ISIJ International

116

View full text Add to dashboard Cite

The physical properties of mould slags are key to their performance in the continuous casting process. The magnitudes of key properties (viscosity, break temperature, f cryst and optical properties) are determined by the mould dimensions, casting conditions and the steel grade being cast. However, a range of other properties (e.g. interfacial tension, density) are needed to minimise defects and process problems. The extant data for thermo-physical properties of conventional mould slags are reviewed here and those for specialist powders (e.g. F-free or for casting TRIP steels) are reviewed in Part 2. It was concluded that there is a need for (i) resolution of the huge differences in thermal conductivity of mould slags for T > 1 050 K obtained with the LP and THW methods (ii) more data for some properties (e.g. C p and density) and more accuracy for others (viscosity, surface tension) (iii) standardised procedures for the determination of f cryst and (iv) characterisation of the porosity in slag films. It was also concluded that (i) gaseous convection makes a significant contribution to the heat transfer in the powder bed and (ii) glassy slag films are probably optically-thin.

show abstract

Crystallisation of slag films formed in continuous casting

Cited by 9 publications

References 0 publications

Heat transfer through mould flux with titanium oxide additions

Heat transfer through mould flux with titanium oxide additions

Calculation of Physical Properties for Use in Models of Continuous Casting Process-Part 1: Mould Slags

Structure and Properties of Slags Used in the Continuous Casting of Steel: Part 1 Conventional Mould Powders

Contact Info

Product

Resources

About