The air-gap formation process at the casting-mold interface and the heat transfer mechanism through the gap

Nishida, Yoshihiro; Droste, Werner; Engler, S.

doi:10.1007/bf02657147

Cited by 171 publications

(70 citation statements)

References 6 publications

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“…Figure 7 show that a highly transient regime took place during the first 50 ms. The two physical phenomena that have been attributed to this regime are contact of the liquid metal with the substrate and nucleation of crystals [38][39][40]. After 50 ms, the heat flux is considerably reduced and the variation is small.…”

Section: Resultsmentioning

confidence: 99%

Dynamic wetting and heat transfer at the initiation of aluminum solidification on copper substrates

et al. 2009

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Section: Resultsmentioning

confidence: 99%

Dynamic wetting and heat transfer at the initiation of aluminum solidification on copper substrates

et al. 2009

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“…[40] By comparison, in the air gap, the heat-transfer coefficient may be as low as 150 W m Ϫ2 K Ϫ1 . [41] In DC casting, the molten aluminum quickly freezes at the meniscus to form a thick solid shell, owing to the higher thermal conductivity, thermal diffusivity, and contraction coefficient of aluminum, relative to steel. As mentioned earlier, the low Péclet number in DC casting allows the chill water below the mold to remove heat from aluminum still inside the mold.…”

Section: A Mold (Or Primary) Coolingmentioning

confidence: 99%

The use of water cooling during the continuous casting of steel and aluminum alloys

Sengupta

Thomas

Wells

2005

Metall Mater Trans A

114

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In both continuous casting of steel slabs and direct chill (DC) casting of aluminum alloy ingots, water is used to cool the mold in the initial stages of solidification, and then below the mold, where it is in direct contact with the newly solidified surface of the metal. Water cooling affects the product quality by (1) controlling the heat removal rate that creates and cools the solid shell and (2) generating thermal stresses and strains inside the solidified metal. This work reviews the current stateof-the-art in water cooling for both processes, and draws insights by comparing and contrasting the different practices used in each process. The heat extraction coefficient during secondary cooling depends greatly on the surface temperature of the ingot, as represented by boiling water-cooling curves. Thus, the heat extraction rate varies dramatically with time, as the slab/ingot surface temperature changes. Sudden fluctuations in the temperature gradients within the solidifying metal cause thermal stresses, which often lead to cracks, especially near the solidification front, where even small tensile stresses can form hot tears. Hence, a tight control of spray cooling for steel, and practices such as CO 2 injection/pulse water cooling for aluminum, are now used to avoid sudden changes in the strand surface temperature. The goal in each process is to match the rate of heat removal at the surface with the internal supply of latent and sensible heat, in order to lower the metal surface temperature monotonically, until cooling is complete.

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“…When the chemical composition and thermal conductivity (k) of the air/gas mixture is known, the interfacial HTC (h) between casting and mold can be simply estimated by h ¼ k=x. [1][2][3] The major disadvantage of this method is that the accurate value of k, which is the thermal conductivity of the air/gas mixture, is difficult to obtain. The second method for obtaining the interfacial HTC is to use the Inverse Method, which was developed by J. V. Beck.…”

Section: Introductionmentioning

confidence: 99%

Effects of Solid Fraction on the Heat Transfer Coefficient at the Casting/Mold Interface for Permanent Mold Casting of AZ91D Magnesium Alloy

2006

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The interfacial heat transfer coefficient (HTC) between the steel mold and AZ91D magnesium (Mg) alloy that cast under various initial solid fractions were investigated in this study.The interfacial HTC was determined by using an Inverse Method with measured temperature data and known thermo-physical properties. A Computer Aided Cooling Curve Analysis technique was used to determine the solid fraction versus temperature relationship. To comply with the requirements of the Inverse Method, a one-dimensional heat transfer system from the casting to the mold was designed for the permanent mold casting of AZ91D Mg alloy in molten and semisolid states.Experiments were conducted with different initial solid fractions of 0, 30, and 50%. The results indicate that the HTC profile of molten AZ91D during solidification can be divided into five stages, while casting with semisolid AZ91D only into three. During each stage, the casting/ mold interfacial conditions vary, which in turn causes the HTC values to vary. These data are critical for any solidification model of permanent mold casting and semisolid casting to obtain a reliable prediction of the thermal profile inside the solidifying casting and its freezing time.

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The air-gap formation process at the casting-mold interface and the heat transfer mechanism through the gap

Cited by 171 publications

References 6 publications

Dynamic wetting and heat transfer at the initiation of aluminum solidification on copper substrates

Dynamic wetting and heat transfer at the initiation of aluminum solidification on copper substrates

The use of water cooling during the continuous casting of steel and aluminum alloys

Effects of Solid Fraction on the Heat Transfer Coefficient at the Casting/Mold Interface for Permanent Mold Casting of AZ91D Magnesium Alloy

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