Cast Shop Technology: Melt Treatment
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Stephen Instone, Speira Gmbh; Mertol Gokelma, Izmir Institute of Technology; Samuel Wagstaff, Oculatus Consulting; Dmitry Eskin, Brunel University
Tuesday 8:00 AM
March 1, 2022
Location: Anaheim Convention Center
Session Chair: Gerd-Ulrich Gruen, Speira GmbH
Performance of Regular and Modified Ceramic Foam Filters (CFFs) during Aluminium Melt Filtration in a Pilot Scale Setup: Are Bergin1; Claudia Voigt2; Robert Fritzsch3; Shahid Akhtar4; Lars Arnberg3; Christos G. Aneziris2; Ragnhild E. Aune3; 1Norwegian University of Science and Technology & Hydro Aluminium AS; 2Technische Universitšt Bergakademie Freiberg; 3Norwegian University of Science and Technology; 4Hydro Aluminium AS
Liquid metal filtration through a ceramic medium has proven to be an efficient way to secure the removal of inclusions and bifilms from molten aluminium. With an increasing focus on recycling of metal values throughout the metallurgical industry, improvements in filter performance and efficiency is currently sought-after but hard to achieve. In the present study, a series of pilot scale filtration trials have been performed using 30 ppi Ceramic Foam Filters (CFFs) with different surface chemistry and roughness. The trials were carried out with a commercial 6xxx aluminium alloy both with and without additions of grain refiners (AlTi5B1). The filter performance was evaluated by using the change in metal level over the filter to indicate the pressure drop, as well as by analysing LiMCA and PoDFA results. Moreover, microstructural analysis by LOM and SEM/EDX were carried out on spent filters, and current filtration theory used to explain the observed results.
Effect of Flow Management on Ultrasonic Melt Processing in a Launder upon DC Casting: Tungky Subroto1; Dmitry Eskin1; Christopher Beckwith2; Dan Roberts3; Iakovos Tzanakis4; Georgi Djambazov2; Koulis Pericleous2; 1Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University London; 2University of Greenwich; 3Constellium UTC; 4Oxford Brookes University
A promising strategy to upscale ultrasonic melt treatment (UST) is a strategically-placed flow management system in a direct-chill (DC) casting launder. This aims to improve the melt residence time and acoustic pressure distribution, which ultimately optimizes the treatment efficiency. This work focuses on observing the effect of partitions on acoustic pressure generated by ultrasonic sonotrode and on the resultant grain refinement upon DC casting of an AA6xxx aluminum alloy with Zr additions. Billets were cast in a pilot-scale DC casting facility: cases with and without partitions and with and without UST are compared. The effect of partitions on the ultrasonic melt treatment efficiency is quantified through grain size analysis and acoustic pressure measurements. The experimental results are supported by the output from a 3D numerical model of acoustic pressure and melt flow in the launder. The positive impact of partitions on the grain refinement and acoustic pressure are demonstrated.
Chlorine Free Degas System for Aluminum Slab Casting and Its Effect on Sheet Products: Sandrella Samaha1; Tao Wang1; Patrice Robichaud1; Pascal Gauthier1; Josee Colbert1; Ginny Hammersmith2; Peter Evans3; 1Rio Tinto; 2Logan Aluminum ; 3Novelis Corporation
The chlorine in-line degasser technology is one of the metal treatment methods utilized in aluminum industry to produce high quality products. However, the chlorine gas used in the system increased the environmental, health and safety (EHS) risks. At Rio Tinto, the chlorine-free salt ACD (Aluminum Compact Degasser) has been implemented to not only mitigate the EHS risks but also improve the product quality. The salt ACD demonstrates better or equivalent metal treatment performance in terms of metal cleanliness, alkali and hydrogen removal compared to the chlorine degasser. The 5xxx and 6xxx alloy products were cast using both degassing systems and subsequently rolled and heat treated for their end uses. In this paper, the metallurgical properties, such as microstructure, strength and ductility, and inclusion populations, were compared between the products produced with regular and salt degassers. The chlorine-free salt ACD meets all the requirements regarding downstream processing and final product attributes.
Aluminothermic Reduction of Sulfides via Reactive Vacuum Distillation: Caspar Stinn1; Spencer Toll1; Antoine Allanore1; 1Massachusetts Institute of Technology
Master alloys containing elements ranging from manganese to silicon to rare earths such as scandium are critical feedstocks for aluminum alloy production, yet their manufacture is often complicated by factors ranging from low yields in the alloying process to challenges with upstream reduction of the alloying element. Meanwhile, recent innovations in metal oxide sulfidation chemistry supports deploying new metal sulfide feedstocks for use in emerging, sustainable, metal reduction technologies. Herein, we present a novel metal sulfide aluminothermic reduction process for aluminum master alloy production via reactive vacuum distillation. We demonstrate its principles and efficiency for aluminum-manganese, aluminum-silicon, aluminum-zirconium, and aluminum-rare earth master alloy production. Supported by an integrated thermodynamic, kinetic, and mass-transport framework, we define a path to predict master alloy product yield, and explore the propagation of impurities such as sodium, iron, oxygen, sulfur, and halides through the process.