Numerical Study of a Direct Chill Slab Caster Fitted With a Porous Filter for Aluminum Alloy AA-2024

2014 ◽  
Author(s):  
Mainul Hasan
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Casting Process ◽  
Direct Chill ◽  
Mushy Region ◽  
Metal Mold ◽  
Melt Flow ◽  
Slab Caster ◽  
Porous Filter ◽  
Aa 2024

The present study is undertaken to model an industrial-sized vertical Direct Chill (DC) slab caster fitted with a porous filter near the melt entry region. The modeled alloy is a high strength aluminum alloy AA-2024 which is extensively used by the aerospace industry. The model has incorporated the 3-D turbulent aspect of the melt flow and heat transfer in the liquid sump and the mushy region solidification aspect of this long solidification range (136° C) alloy. The verified 3-D turbulent CFD in-house code is used to study the effects of various parameters of this casting process in order to gain some fundamental understanding of the melt flow and solidification behavior of the process. The studied caster consists of a popular ‘hot-top’ mold fitted with a porous filter above which molten aluminum alloy is delivered with a constant flow-rate across the entire hot-top. Because of two-fold symmetry, a quarter of the domain of the caster is modeled to save computational costs and time. A staggered control volume based finite-difference scheme is used to solve the non-dimensional modeled equations and the associated boundary conditions. The turbulent aspect of the flow in the porous filter is modeled using the latest suggested version of the Brinkman-Forcheimer extended form of Darcy equation for a porous media. The turbulent melt flow and solidification heat transfer in the clear fluid region are modeled using a low Reynolds number version of the k–ε eddy viscosity model. Computed results for the steady-state phase of the casting process are presented for four casting speeds, varying from 100 to 220 mm/min, for three metal-mold contact regions, varying from 20 to 50 mm and for three metal-mold convective heat transfer boundary conditions, varying from 1.0 to 4.0 kW/m2K and all for a fixed inlet melt superheat of 64° C. The permeability of the filter is also varied to ascertain its influence on the predicted results. Computed results of the velocity and temperature profiles, the sump depth and mushy region at the centre of the caster as well as the solidification shell thickness at the exit of the mold are provided and discussed. The present work can provide some useful guidelines in designing and optimizing a vertical DC slab caster for producing good quality casts for the common aluminum alloy AA-2024.

A Comparison Between 3-D Thermal Model and 3-D CFD Model for Vertical DC Casting of Rolling Ingots of Aluminum Alloy 7050

2014 ◽  
Author(s):  
Mainul Hasan ◽  
Latifa Begum
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Thermal Model ◽  
Casting Process ◽  
Direct Chill ◽  
Turbulent Heat Transfer ◽  
Mushy Region ◽  
Turbulent Heat ◽  
Cfd Model ◽  
Dc Casting

In this study, first a 3-D thermal model is developed for an open top, vertical direct chill (DC) casting process of rolling slabs (ingots) by taking into account the casting speed in the form of slag flow in the thermal connective-diffusion equation. The mushy region solidification characteristics of the process are accounted for through the implementation of the enthalpy porosity technique. The thermal model is later extended to a 3-D CFD model to account for the coupled turbulent heat transfer and solidification aspect of the process. Both models simulate an industrial-sized, hot-top type vertical Direct Chill (DC) slab caster for high strength aluminum alloy AA-7050. A staggered control volume based finite-difference scheme is used to solve the modeled equations and the associated boundary conditions. In the CFD model, the turbulent aspects of flow and solidification heat transfer are modeled using a low Reynolds number version of the k–ε eddy viscosity approach. Computed results for the steady-state phase of the casting process are presented for four casting speeds varying from 60 to 180 mm/min for a fixed inlet melt superheat of 32°C. Simulation results of the velocity and temperature fields and heat fluxes along the caster surface are presented for the CFD model and the shell thickness and sump depth are compared between the CFD and thermal models.

Industrial Direct Chill Slab Caster of Tin Bronze (C903) Using a Porous Filter in the Hot-Top

2017 ◽  
Vol 10 (2) ◽  
Author(s):  
Mainul Hasan ◽  
Latifa Begum
Keyword(s):  
Contact Region ◽  
Convective Heat Transfer Coefficient ◽  
Direct Chill ◽  
Cfd Modeling ◽  
Mushy Region ◽  
Slab Caster ◽  
Entire Cross Section ◽  
Porous Filter ◽  
Hot Top ◽  
Tin Bronze

A 3D computational fluid dynamics (CFD) modeling study has been carried out for the tin bronze (C903) slab of industrial size in a vertical direct chill caster. The melt is delivered from the top across the entire cross section of the caster. An insulated hot-top is considered above the 80-mm mold to control the melt level in the mold. A porous filter is considered in the hot-top region of the mold to arrest the incoming inclusions and homogenize the flow into the mold. The melt flow through the porous filter is modeled on the basis of the Brinkmann–Forchheimer-extended non-Darcy model. Results are obtained for four casting speeds varying from 40 to 100 mm/min. The metal–mold contact region, as well as the convective heat transfer coefficient at the mold wall, is also varied. In addition to the above, the Darcy number for the porous media is also changed. All parametric studies are performed for a fixed inlet melt superheat of 62 °C. The results are presented pictorially in the form of temperature and velocity fields. The sump depth, mushy region thickness, solid shell thickness (ST) at the exit of the mold, and axial temperature profiles are also presented and correlated with the casting speed through regression analysis.

Three-Dimensional Numerical Study of a Low Head Direct Chill Slab Caster for Aluminum Alloy AA5052

2015 ◽  
Vol 7 (2) ◽  
Author(s):  
Mainul Hasan ◽  
Latifa Begum
Keyword(s):  
Aluminum Alloy ◽  
Casting Speed ◽  
Numerical Study ◽  
Three Dimensional ◽  
Casting Process ◽  
Direct Chill ◽  
Slab Caster ◽  
Low Head ◽  
Liquid Depth ◽  
Effective Heat Transfer Coefficient

A 3D numerical study is carried out for a vertical direct chill (DC) rolling ingot caster for an aluminum alloy (AA-5052). The model incorporated the coupled turbulent melt flow and solidification aspects of the casting process. The caster consists of a low-head hot-top mold. The melt is assumed to have been delivered through the entire top cross section of the caster. The previously verified in-house computational fluid dynamics (CFD) code is used to investigate the effects of the important parameters such as casting speed, inlet melt superheat, and mold-metal contact effective heat transfer coefficient (HTC) on the low-head casting process. It is found that the sump depth (SD), liquid depth, and mushy thickness (MT) at the center of the ingot increase linearly with the casting speed while the shell thickness (ST) at the exit of the mold decreases linearly with the casting speed. Useful correlations concerning the above quantities with casting speed have been provided for the benefit of DC casting operators.

Effects of the Low Frequency Electromagnetic Field on the Centerline Macrosegregation of 7075 Aluminum Ingots

2011 ◽  
Vol 295-297 ◽  
pp. 1705-1708
Author(s):  
Dan Dan Chen ◽  
Hai Tao Zhang ◽  
Xiang Jie Wang ◽  
Jian Zhong Cui
Keyword(s):  
Electromagnetic Field ◽  
Steady State ◽  
Mushy Zone ◽  
Transition Region ◽  
Low Frequency ◽  
Casting Process ◽  
Direct Chill ◽  
Mushy Region ◽  
Chill Casting ◽  
Temperature Contour

The effects of the low frequency electromagnetic field on the macrosegregation of the 7075 aluminum ingots were investigated. The 7075 aluminum ingots with the diameter of 200 mm were prepared by the conventional direct chill casting and the low frequency electromagnetic field casting (LFEC) processes, respectively. The temperature during casting at steady state was measured, and the mushy region was observed from the temperature contour. The concentrations of the alloying elements were measured by the spectrograph. It was found that the transition region was broadened, but the mushy zone became narrower with presence of the low frequency electromagnetic field. The centerline macrosegregation of the ingots was alleviated by the low frequency electromagnetic casting process.

Primary Cooling Heat Transfer during the Direct-Chill Casting of Aluminum Alloy AA6111

2012 ◽  
pp. 1483-1492 ◽  
Author(s):  
Etienne Caron ◽  
Amir Baserinia ◽  
Rosa O. Pelayo ◽  
David C. Weckman ◽  
Mary A. Wells
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Direct Chill ◽  
Direct Chill Casting ◽  
Chill Casting

Primary Cooling Heat Transfer during the Direct-Chill Casting of Aluminum Alloy AA6111

2012 ◽  
pp. 1483-1492
Author(s):  
Etienne Caron ◽  
Amir Baserinia ◽  
Rosa O. Pelayo ◽  
David C. Weckman ◽  
Mary A. Wells
Keyword(s):  
Heat Transfer ◽  
Aluminum Alloy ◽  
Direct Chill ◽  
Direct Chill Casting ◽  
Chill Casting

Modelling of the Metal/Mould Interactions in the DC Casting Process for Aluminium and Magnesium

2010 ◽  
Vol 654-656 ◽  
pp. 783-786 ◽  
Author(s):  
Arvin Prasad ◽  
Ian F. Bainbridge
Keyword(s):  
Heat Transfer ◽  
Casting Process ◽  
Direct Chill ◽  
Heat Extraction ◽  
Small Scale ◽  
Wall Region ◽  
Wall Heat Transfer ◽  
Mould Wall ◽  
Dc Casting ◽  
Basic Features

The process of direct chill (DC) casting of aluminium and magnesium alloys is regarded as a mature technology. The thrust of more recent work to understand and upgrade the technology has been centred on developing models of the process, the most advanced of which (e.g., Alsim and Calcasoft) have been used to examine what may be considered macro-features of the process (macro-segregation, hot cracking, etc.). These models, being macroscopic, rarely elaborate on the role of mould-wall heat transfer in the DC casting process. As part of the work on DC casting being conducted at CAST, for the investigation of small scale features of the process (e.g. heat extraction through the mould wall), a 2D finite Difference model of the process near the mould-wall region has been developed. The basic features of the model are described and initial results outlined.In particular, the effect of mould-wall heat transfer on the solid shell formed during the steady state regime of DC casting will be presented.

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