Cast Shop Technology: Metal Cleanliness
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Samuel Wagstaff, Oculatus Consulting
Wednesday 8:30 AM
March 17, 2021
Room: RM 29
Location: TMS2021 Virtual
Session Chair: Gerd-Ulrich Gruen, Hydro; Kumar Sundaram, Novelis
8:30 AM
Automated Metal Cleanliness Analyzer (AMCA) – An Alternative Assessment of Metal Cleanliness in Aluminum Melts: Hannes Zedel1; Robert Fritzsch1; Ragnhild Aune1; Shahid Akhtar2; 1NTNU; 2Norsk Hydro
The established industry standards for assessing the cleanliness of aluminum melts are PoDFA (Porous Disc Filtration Apparatus) and LiMCA (Liquid Metal Cleanliness Analyzer) analyses. PoDFA provides the necessary qualitative and quantitative differentiation between the inclusions present in the molten metal, but it is slow and subject to human biases. LiMCA provides real time data without sufficient differentiation, limiting its usefulness for metal quality and process control. Complementary solutions are in demand that can provide similar quality results as PoDFA at the speed of LiMCA.With the Automated Metal Cleanliness Analyzer (AMCA), an alternative solution is suggested that combines the strengths of both established approaches by standardized on-site sampling and automated image analysis for real time quality control. The present study shows a validation of the image analysis method by replicating the main cleanliness indicator of PoDFA in real industry samples at high precision.
8:50 AM
Overview of the Possibilities and Limitations of the Characterization of Ceramic Foam Filters for Metal Melt Filtration: Claudia Voigt1; Jana Hubálková1; Are Bergin2; Robert Fritzsch2; Ragnhild Aune2; Christos G. Aneziris1; 1Institute of Ceramic, Glass and Construction Materials; 2Norwegian University of Science and Technology
The filtration of molten metal using ceramic foam filters (CFF) is a purification method often used in the aluminum industry to meet the increasing demands in regards to melt quality. CFFs are in most cases produced by the replica method using polyurethane foam scaffolds, which are coated with a ceramic slurry of specific composition before being sintered into its final structure. Despite the key role of CFFs in view of metal cleanliness, only a few quality parameters exist.In the present study an overview of the different material properties of importance in regard to CFFs, their determination and limitations are presented. The properties covered are the density and the thermal expansion coefficient measured with the aid of dilatometer, as well as the filter porosity and microstructure through mercury intrusion porosimetry and computer tomography respectively. The Youngs Modulus, as well as the crushing- and bending strengths are also measured and discussed.
9:10 AM
Compression Testing of Ceramic Foam Filters (CFFs) Submerged in Aluminium at Operating Temperature: Are Bergin1; Robert Fritzsch2; Shahid Akhtar3; Lars Arnberg2; Ragnhild E. Aune2; 1Norwegian University of Science and Technology & Hydro Aluminium AS; 2Norwegian University of Science and Technology; 3Hydro Aluminium AS
Particles and inclusions are commonly removed from molten aluminium with the use of ceramic foam filters (CFF). The mechanical properties of CFFs are of great importance not only during transportation, storage and mounting, but also in view of securing the integrity of the filters during operation. Data on the compression strength of CFFs at room temperature are available in literature, but this is not the case for their performance under operating conditions. The main goal of the present study has been to measure the compression strength of conventional CFFs from different manufacturers, geometry and pore densities at elevated temperatures and different holding times both before and after being submerged into molten aluminium. Preliminary results indicates that at room temperature the compression strength were more or less unaffected, while a significant decrease was observed for the CFFs exposed to operating conditions. The effect of the holding time was inconclusive.
9:30 AM
The Effect of Grain Refiner on Aluminium Filtration: Sarina Bao1; Jiawei Yang2; Shahid Akhtar3; Stig Tjøtta3; Ulf Tundal3; Tanja Pettersen4; Yanjun Li2; 1SINTEF Materials & Chemistry; 2Norwegian University of Science and Technology; 3Norsk Hydro; 4SINTEF Manufacturing
Grain refinement of aluminium and its alloys is a common industrial practice. Fine equiaxed, grain structure leads improved castability, strength, machinability, formability, and good surface finish. Filtration is one of the widely used technologies to remove inclusions from the melt. Ceramic Foam Filters (CFFs) are commonly used to clean the aluminium melt before the casting process. However, at a high inclusion load and with grain refiner addition, reduced filtration efficiency is well known to occur. In the current work, the filtration behaviour of CFFs with three different levels of inclusions and grain refiner has been systematically studied in plant scale pilot trials at Hydro's reference centre in Sunndalsøra, Norway. The results show that oxide films capture grain refiner particles. Grain refiners tends to agglomerate heavily with inclusions at higher inclusion content. These heavy and compacted small clusters are more likely to be released from the CFF during the filtration process. Little effect from grain refiner addition on filtration efficiency is observed when the level of grain refiner and chips addition is relatively low or when both are high, but not with high grain refiner addition with middle level of inclusion load. The threshold of the grain refiner addition effect is further discussed in this paper.
9:50 AM
Next-generation Electrical Preheating System for Filter Boxes: Jochen Schnelle1; Markus Byczek1; 1Drache Umwelttechnik GmbH
Filter boxes for ceramic foam filters in Aluminum casthouses are typically preheated by gas-fired systems, as they are faster and more versatile than existing electrical preheating solutions. The Drache Flow Heater is a next-generation electrical preheating system which has the efficiency of a gas-fired system, combined with the ease of use of an electrical system. In this paper, a brief introduction to the technology of the Flow Heater is given. A comparison is made between the Flow Heater, a gas-fired preheating system and existing electrical heating solutions, showing the individual advantages of each system. Performance data for preheating ceramic foam filters with the Drache Flow Heater is shown. Furthermore, an outlook on the future development of the Flow Heater system is given.
10:10 AM
Reduction of Impurity Elements by Applying Electromagnetic Stirring in Fractional Crystallization: Yuichiro Murakami1; Naoki Omura1; 1National Institute of Advanced Industrial Science and Technology
Aluminum smelting results in extremely high greenhouse gas emissions. Recycling of aluminum alloy is a key issue for decreasing the carbon footprint of aluminum products. To recycle aluminum scrap, impurity elements such as silicon, copper, etc. will become an obstacle. In this study, removing impurity elements from casting aluminum alloy which includes silicon higher than 7% was attempted by using a fractional crystallization method with electromagnetic stirring (EMS). EMS was implemented during cooling from the liquid phase to the solid-liquid coexistence temperature. Then the semi-solid aluminum slurry was obtained. After that by squeezing aluminum slurry, α-aluminum phase particles and the liquid phase were separated, and the number of α-phase particles were increased by applying EMS. The Si contains in α-phase was less than 2.0%. After squeezing, Si contains could be reduced from the original material.
10:30 AM
NatureAlu: Manufacturing High Purity Aluminum from the Concept Idea to the Production Plant: Jean Francois Desmeules1; Denis Mazerolle2; 1Dynamic Concept; 2NatureAlu
NatureAlu produces high purity aluminium (4N or 99.99% and more) using a process known as Fractional Crystallisation. The idea of starting such a company initiated a few years ago when two retired metallurgical engineers saw an opportunity for a North-American based 4N aluminium producer. A team was built and the design of a purification equipment began. Resources from research centers were used to help improve the process parameters. A pilot plant was built to test the equipment in real production size. Using results from experiments made with the pilot plant helped streamline the whole production process and optimize the full-size plant layout and budget. The plant is starting production in Q3 2020. The purpose of this paper is to present the many interdependent steps and actions required to achieve the goal of opening a production plant starting with a project idea, including market assessment, technology development, financing and project management.
10:50 AM Question and Answer Period