Influence of Rate of Heat Removal on Uneven Solidification in Continuous Casting Mould

Sugitani, Yasuo; Nakamura, Masanobu; Watanabe, Tadao

doi:10.2355/tetsutohagane1955.67.9_1508

Cited by 27 publications

(18 citation statements)

References 2 publications

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“…In any way, mild cooling has been considered to be an effective countermeasure against the uneven solidification. 12) So, the mild cooling of initial solidification has been tried by means of fine grooves on the surface of mold, 13,14) application of materials of low thermal conductivity to the mold, 15,16) decrease of coolant flow rate in the mold, 17) crystallization of the film which mold flux forms after infiltration along the mold. 11,[18][19][20] It is necessary to estimate solidification parameters of the solidified shell in order to understand and improve the initial solidification in the mold.…”

Section: Introductionmentioning

confidence: 99%

Growth of Solidified Shell Just below the Meniscus in Continuous Casting Mold

Hanao¹,

Kawamoto²,

Yamanaka³

2009

ISIJ Int.

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In the high speed continuous casting of hypo-peritectic steel slabs, growth of solidified shell just below the meniscus in the mold was researched. Rate of cooling and solidification was estimated on the basis of experimental results of thickness profiles of solidified shell, heat flux in the mold and dendrite arm spacing in the solidified structure beneath the surface of the slabs cast at 3-5 m/min.As a result, it was found that there is a delaying period of solidification growth at the beginning, till the shell grows up to about 1 mm thick. After that, it grows in linear relation to square root of solidification time. Dealing with the thickness profiles as a function of solidification time and solidification rate was obtained by differential. Furthermore, cooling rate of the shell was estimated with this solidification rate and heat flux in the mold. This cooling rate showed good agreement with that estimated from dendrite secondary arm spacing of the slabs.Estimated cooling rates were compared with the slabs by conventional continuous caster at 1.1-1.6 m/min and the influence of casting speed was discussed. It resulted in that cooling rate increases with casting speed and the difference by casting speed begins to be remarkable in the period of 0.1-1 s for solidification time, when uneven solidification just begins to occur. This agreement was considered to be one of the reasons why uneven solidification or longitudinal surface cracking of slabs tends to occur with increase of casting speed.

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Section: Introductionmentioning

confidence: 99%

Growth of Solidified Shell Just below the Meniscus in Continuous Casting Mold

Hanao¹,

Kawamoto²,

Yamanaka³

2009

ISIJ Int.

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“…1,2) To prevent surface defects such as longitudinal cracking, it is necessary to provide uniform heat extraction from the shell, which can be attained by reducing the heat transfer across the mold flux layer. 3,4) In practice, this reduction in heat transfer is being made by forming crystals of cuspidine (3CaO · 2SiO 2 · CaF 2 ) in the flux film 5) and, for further improvements of mold flux, it is very important to know how crystallization of mold flux reduces the heat transfer.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Heat Transfer Reduction by Crystallization of Mold Flux for Continuous Casting

et al. 2008

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The mechanism by which crystallization of mold flux reduces the heat transfer between the steel shell and the mold has been investigated from the viewpoint of physical properties and characteristics of mold flux and air gap on the basis of a heat transfer model involving conduction and radiation processes. It has been found that, in mold fluxes for medium carbon steel, the reflectivity of the crystalline slag layer formed in mold flux film is an efficient factor for further reducing the total heat flux in the film. The heat transfer reduction based on this finding would be possible according to the following mechanism: Crystallization of mold flux film increases the reflectivity of the crystalline slag layer in the film owing to enhanced scattering of light by introduction of crystal grain boundaries, and thereby more radiation energy returns from the crystalline slag layer to the steel, leading to reduction in the total heat flux across the film.

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“…1,2) To avoid such a situation, mild cooling is required because it is effective for improving homogeneity. 3) From the viewpoint of mild cooling by mould flux modification, many studies have been made and reviewed by Mills and Fox: 4) Namely, crystallisation of mould flux leads to heat transfer reduction across the mould flux from the steel shell to the mould, 5,6) where heat is transferred by both thermal conduction and radiation, the former contributing to the greater part of heat flux. [7][8][9] The magnitude of conductive heat flux is affected by thermal conductivity of mould flux, which usually increases by crystallisation.…”

Section: Introductionmentioning

confidence: 99%

Effects of Valence Control of Iron Ions on Radiative Heat Transfer in Mould Flux

et al. 2013

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The present study aims to investigate the possibility of reduction of radiative heat flux in the continuous casting process by valence control of iron ions in mould flux. The compositions of samples were designed on the basis of a practical mould flux, where the basicity defined as CaO/SiO2 was also varied from 0.6 to 1.4 to change the valence of iron ions. Mixtures of oxide and fluoride powders were melted in platinum crucibles in air and then the melts were quenched into brass moulds to obtain glassy samples. In addition, graphite crucibles were also used to melt samples having the basicity of 1 at lower partial pressure of oxygen. Some glassy samples were heat-treated for crystallisation. Glassy and crystallised samples were subjected to chemical analyses and optical measurements of apparent reflectivity and transmissivity. The concentration ratio of Fe 3+ /Fe 2+ increased with increasing basicity but decreased by melting in graphite crucibles. Increasing concentration ratio of Fe 3+ /Fe 2+ leads to an increase of radiative heat flux for the glassy samples but to a decrease for the crystallised samples: the effect of valences of iron ions is more prominent in the glassy samples. In the crystallised samples, on the contrary, the degree of crystallinity affects radiative heat flux more strongly than the valence of iron ions.KEY WORDS: mould flux; mild cooling; basicity; valence of iron ions; degree of crystallinity.

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Influence of Rate of Heat Removal on Uneven Solidification in Continuous Casting Mould

Cited by 27 publications

References 2 publications

Growth of Solidified Shell Just below the Meniscus in Continuous Casting Mold

Growth of Solidified Shell Just below the Meniscus in Continuous Casting Mold

Mechanism of Heat Transfer Reduction by Crystallization of Mold Flux for Continuous Casting

Effects of Valence Control of Iron Ions on Radiative Heat Transfer in Mould Flux

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