Numerical and experimental modelling of two-dimensional unsteady heat transfer during inward solidification of square billets

Author(s)

Bertelli, Felipe ^{[1, 2]} ; Faria, Jonas D. ; Goulart, Pedro R. ^[3] ; Brito, Crystopher ^[4] ; Cheung, Noe ^[4] ; Garcia, Amauri ^[4]

Affiliation

^[1] Santa Cecilia Univ UNISANTA, Dept Mech Engn, Santos - Brazil

^[2] Santa Cecilia Univ UNISANTA, Postgrad Program Mech Engn, Santos - Brazil

^[3] Fed Inst Educ Sci & Technol Sao Paulo IFSP, Itapetininga - Brazil

^[4] Univ Campinas UNICAMP, Dept Mfg & Mat Engn, Campinas, SP - Brazil

• Document type: Journal article
• Source: APPLIED THERMAL ENGINEERING; v. 96, p. 454-462, MAR 5 2016.
• Web of Science Citations: 7

Abstract

The development of air gaps between the solidifying shell and the mould is an inherent phenomenon in both continuous and static casting processes, and is one of the major factors affecting not only the microstructure formation but also the resulting properties and surface quality of castings. The heat flux transients at the casting/mould interface therefore attracted many attempts of mathematical modelling. In this study, an explicitly solved unsteady-state two-dimensional finite difference heat transfer model was used for the solution of the inverse heat conduction problem. The overall heat transfer coefficient between the casting surface and the cooling fluid (h(g)) - which is affected by a series of thermal resistances such as those from water, mould and air gap formed between the metal surface and the inner mould surface - is determined for the inward solidification of a hypoeutectic Al-Fe alloy casting in a water-cooled steel mould. Thermocouples were inserted into the casting with a view to continuously measure temperatures during solidification, which is necessary to furnish thermal information to be compared with simulations, and an automatic search selected the best theoretical-experimental fit from a range of transient heat transfer coefficient profiles. The microstructural cellular spacing was measured in order to permit correlations with the cooling rate ((T)over dot) at different positions from the metal/mould interface to be established. It is shown by numerical heat transfer simulations that the cooling rate decreases from the casting surface, and after reaching a minimum value, starts to increase characterising a reversal trend towards the centre of the casting. It is also shown that the cellular spacing accompanies the trend in the cooling rate. The obtained results - transient (h(g)) profiles and growth laws relating the cellular spacing to () - can contribute to a better understanding of transport phenomena and microstructure evolution of more complex processes involving transient solidification. (C) 2016 Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 12/08494-0 - Thermal and Microstructural Parameters in the Transient Solidification of Al-Mg and Al-Mg-Si Alloys and Correlation with Mechanical and Corrosion Resistances
• Grantee: Crystopher Cardoso de Brito
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 13/23396-7 - Effects of solidification MicrostructureParameters of Aluminum-based multicomponent alloys (Al-Mg-Si; Al-Sn-Cu; Al-Zn-Mg) on the resistances to Corrosionand tribocorrosion degradation
• Grantee: Amauri Garcia
• Support Opportunities: Regular Research Grants
• FAPESP's process: 12/16328-2 - The Correlation between Solidification Microstructures and Mechanical and Tribological Properties of Al-Sn-Cu and Al-Sn-Si Alloys
• Grantee: Felipe Bertelli
• Support Opportunities: Scholarships in Brazil - Post-Doctoral