Effects of Intercooling Intensity on Temperature Field and Microstructure of Large-Scale 2219 Al Alloy Billet Prepared by Internal Electromagnetic Stirring Casting.

Yang Qiu,Xintao Li,Nan Zhou,Mingyang Liu,Kaihong Zheng

doi:10.3390/ma15051809

Yang Qiu, Xintao Li + Show 3 more

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https://doi.org/10.3390/ma15051809

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Abstract

Internal electromagnetic stirring is an advanced melt treatment method, which can be used in direct chill casting to prepare large-scale Al alloy billets. Intercooling intensity is a primary parameter of internal electromagnetic stirring; its effects on temperature fields and microstructures have been investigated via numerical simulations and industrial experiments, respectively. The simulated results show an increase in the intercooling affected area and a decrease in sump depth with an increase in the intercooling heat transfer coefficient. The heat transfer coefficient should not exceed 500 W/(m2 °C) because the solid fraction of the intercooling end bottom may exceed 50%. The experiment’s results demonstrate that the average grain sizes in the edge, 1/2 radius, and center are 151 ± 13 μm, 159 ± 14 μm, and 149 ± 16 μm, respectively, under a liquid nitrogen flow rate of 160 L/min, which is much finer than that of 80 L/min and more homogeneous than that of 240 L/min. Furthermore, an experimental liquid nitrogen flow rate of 80 L/min, 160 L/min, and 240 L/min approximately correspond to the simulated heat transfer coefficient of 200 W/(m2 °C), 300 W/(m2 °C), and 400 W/(m2 °C), respectively.

Highlights

Coarse and inhomogeneous microstructures always occur during conventional direct chill casting (DCC) of billets, an issue that usually worsens as the scale of the billet and range of solidification increases [1–4]
A large number of studies have shown that the abovementioned problems can be solved by using electromagnetic stirring (EMS) during DCC [12–15]
The intercooling intensity is a primary parameter of internal EMS (IEMS) DCC

Summary

Introduction

Coarse and inhomogeneous microstructures always occur during conventional direct chill casting (DCC) of billets, an issue that usually worsens as the scale of the billet and range of solidification increases [1–4]. Deformation processes, such as rolling and forging, can refine a microstructure, but cannot significantly improve its inhomogeneity [5]. Conventional EMS can only be applied to small-scale billets To solve this problem, the annular EMS method was proposed; inserting a core into the melt center [17,18]. Annular EMS does not fundamentally change the traditional heat transfer pattern (from outside to inside); the melt temperature field is always very inhomogeneous, especially in large-scale billets.

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