Alloys & Billet Process

Paul A. Rometsch, Rio Tinto – Aluminium, Canada; and Jerome Fourmann, Rio Tinto – Aluminium, USA

Scandium (Sc) can offer many benefits to aluminum alloys, such as significant strengthening, grain structure control and corrosion inhibition. However, Sc has rarely been used in extrusions due to cost and supply issues. Another somewhat related challenge is that there are metallurgical aspects to be understood and exploited if maximum benefits are to be achieved from minimal Sc additions.

This work explores the effects of small Sc additions (~0.1 wt%) on selected extrusion alloys from among the 1xxx-, 3xxx-, 5xxx- and 6xxx-series. The addition of Sc to 6xxx-series extrusion alloys is particularly challenging due to the potential loss of Sc to coarse non-hardening AlSiSc particles and due to the mismatch in aging temperatures between the Al3Sc and MgSi hardening precipitates. This work reveals possible pathways for processing different types of extrusion alloys to achieve maximum microstructure and property benefits per unit Sc addition.

Ulf H. Tundal, Hydro Aluminium Metal and Oddvin Reiso, Retired, Hydro Aluminium Metal; Jorgen Li, Raufoss Technology, Norway; Stephane Briau, Raufoss Technology, Canada; Ola Jensrud, Benedikte Myrold and Jon Holmestad, SINTEF Manufacturing AS, Norway

A novel method for producing high-strength extruded profiles has been developed and implemented in production of a rear spring link for a battery electric vehicle coming for sale in 2025. The method, named HyperAl, is based on a high-strength 6xxx-series alloy and a new thermal treatment process for the billets. With this processing it is possible to increase the extrusion speed by 150-200% as compared to standard processed billets and still obtain the same strength level in the final product.

Hydro Aluminium Metal and Raufoss Technology have worked closely together for about three years to optimize the alloy and the processing from the cast billets to the end-product. This has resulted in an alloy that is produced with a low carbon footprint, reduced processing cost in extrusion, better formability of the extruded profile, and very attractive properties in the final product.

Borja Lopez, David Mann and Syed Ali, Innerspec Technologies, USA

This paper covers the development and implementation of an automated inline ultrasonic inspection system for aluminum ingots using Electromagnetic Acoustic Transducers (EMAT).

Ultrasonic testing (UT) of aluminum ingots ensures that billets with cracks are not used in production. Traditionally, UT inspection is performed manually on each ingot using coupling gel, or automatically with a stand-alone station and water-column UT transducers. Manual inspections are time consuming, rely on trained operators, and leave no electronic records of the inspection. Automated stations require additional floor space, dedicated handling equipment, and time-consuming maintenance of couplant-management systems.

The EMAT solution implemented provides a dry ultrasonic system that can be added to an existing material handling conveyor, such as leading into the billet saw. The final system provides the same records obtained by a stand-alone system in a more compact and cost-efficient package. The paper explains the steps taken during the development of the technique.

Giovanni Magarotto, T.T. Tomorrow Technology S.p.A., Italy

The future is to go green, save energy and comply with increasingly demanding safety rules. T.T. Tomorrow Technology, a leading company in the aluminum industry, supplies furnace tending vehicles with the aim of replacing the current state-of-the-art in cast house equipment, where the presence of forklifts and standard loaders is massive.

For more than two decades, T.T. Tomorrow Technology has been studying, designing, and manufacturing customized tailored vehicles and systems to support the melting process in order to increase furnace efficiency and productivity. Excellent results have been achieved in terms of reducing the time for operations, as well as in energy cost savings.

Not less important is to enhance the safety level: hundreds of cast houses use forklifts, but this practice reduces the benefits and increases the risks for operators.  Choosing a dedicated vehicle for charging, cleaning, and skimming the aluminum furnaces is the right choice to improve productivity and to reduce risks and injuries for the people that work in a dangerous area such as a cast house.

Jan Flesch, Johannes Gebhard and A. Erman Tekkaya, Institute of Forming Technology and Lightweight Components (IUL), TU Dortmund University, Germany

Longitudinal weld seams are unavoidable in the extrusion process of hollow profiles when a porthole die is used. The weld seam becomes visible after the anodization of the profiles but is influenced by every step of the process chain. To investigate the influence of the billet’s composition, resulting microstructure and different heat treatment methods on the visibility of the weld seam, homogenization, extrusion, artificial aging, and anodization of multiple batches of AA6060 is performed. Microstructure is investigated during every step of the process chain with light-scanning electron and transmission electron microscopy, to analyze the relation between dislocations, precipitations and streaking. The chemical composition and homogenization of the billets have the highest influence on the visibility of the weld seams. Slightly higher amounts of magnesium, copper and iron, as well as insufficient homogenization lead to more pronounced streaks, while the extrusion parameters only have a minor influence.

Martha Indriyati, Oddvin Reiso, Jostein Røyset, and Ulf H. Tundal, Hydro Aluminium R&D, Norway

For AlMgSi extrusion alloys it is common knowledge that increasing additions of Mg and Si give an increase in strength of the age hardened extrudate but also a decrease in the extrudability. The reduced extrudability is due to two factors: 1) an increase in deformation resistance; and 2) a reduction in the solidus temperature. In the present work, these two effects are quantified for Mg and Si individually. For Mg, the main effect is the increase in deformation resistance, whereas for Si the main effect is the reduction in solidus temperature. The effect on maximum extrusion speed per wt.% added is approximately equal for both alloying elements.

Microstructure and mechanical properties as a function of Mg and Si content and of extrusion speed are also measured, and the effects of adding Mn for recrystallization resistance are demonstrated. This combined knowledge gives a sound basis for making optimal alloy selections.

Knut Omdal Tveito, Hydro Aluminium Metal; and Arild Håkonsen, Hycast AS, Norway

Control of process parameters and especially casting temperature remains key to ensure process stability and quality for Direct Chill (DC) casting of extrusion ingots. A Digital Twin based on reduced order models is developed to simulate the temperature evolution and filling process during DC casting. Its application towards design of new casting centers and optimization of existing casting processes is demonstrated. The Digital Twin is capable of running in real-time and can be used to optimize the casting process for a wide range of alloys and diameters and as a training tool.

Aybars Guven, Isik Kaya and Emrah Ozdogru, TRI Metalurji A.S., Turkey

This study investigates the effects of two different mold types on the metallurgical properties of aluminum billets produced through direct chill casting. Microstructure characterization was performed using optical and scanning electron microscopy following homogenization heat treatment. The billets were analyzed in both transverse and longitudinal sections to determine the effect of mold type on the microstructure, grain size, and shell zone. The results demonstrate that both mold types are capable of producing billets with a high industrial standard microstructure.  Therefore, the choice of mold type significantly affects the metallurgical properties of the final product. This study provides valuable insights into optimizing the casting process to produce high-quality aluminum billets with superior metallurgical properties.

James Tomkinson, RiA Cast House Engineering, Germany; and David Roth, GPS Global Solutions, USA

Automation of the scrap charging and skimming operations with in-furnace camera systems gives advantages that are unique, in an environment where keeping well-trained operators in the cast house is difficult. This technology can reduce cycle times by up to 50%, while saving up to 30% in energy with reduced CO2 generation. Automated skimming with video optimization has a significant impact on melt yield, energy use and the final amount of salt cake waste created. Taking the skimming out of the hands of the operator makes total dross removal a thorough practice every time. Automation of the process allows for no dross to remain in the furnace between cycles, eliminating the generation of more dross and lowering recoveries. Precise skimming operations keeps the molten and alloyed aluminum in the furnace where it belongs. Automated skimming also shortens skim cycles, further reducing door open time and wasted energy.

Marco Tarabini, Yuvan Sathya Ravi, Fabio Conti, and Paolo Chiariotti, Politecnico di Milano, Italy; Pietro Palini and Maurizio Colombo, One-Off America LLC, USA

Adoption of a camera inside the furnace for the identification of the aluminum level and for the detection of the aluminothermic reaction is proposed. An RGB camera produced by Canty is installed in three different production systems and continuously acquired videos. The camera calibration and the 3D model of the melting furnace allows detection of aluminum levels during the melting process. Three different computer vision algorithms are developed to identify the aluminothermic flames. Algorithms are developed based on image processing techniques on RGB, HSV and Grey scale of images extracted from video frames. The system detects conditions inside the furnace and sends feedback controls to the auxiliary machines (loader, skimming machine and stirrer). Advantages and limitations of the different algorithms are presented and discussed.

Keaton Schmidt, Thomas Wood, and Paul Sanders, Michigan Technological University, USA; and Tim Langan, Sunrise Energy Metals, Australia

Extrusion at high temperatures and strains followed by post-extrusion heat treating can lead to undesirable surface recrystallization such as peripheral coarse grains (PCG), which can reduce fatigue and corrosion resistance. Scandium (Sc) additions produce nano-sized Sc-core/Zr-shell dispersoids that resist recrystallization. Baseline 7050 billet (Zr only) and two Sc additions (0.02wt% and 0.05wt%) are extruded with a die that produces surface strains of 8-12.5% to assess dispersoid effects on PCG formation after standard heat treating. The low Sc addition reduced PCG by 15% at low strains and 50% at high strains. High Sc prevented PCG formation at low strains and reduced PCG volume by 90% at high strains. Adding 0.1wt% Sc doubles the alloy cost, but this may be offset by improved extrusion quality and reduced extrusion process costs.

Isik Kaya, Aleyna Gumussov, Aybars Guven, and Emrah Ozdogru, TRI Metalurji A.S., Turkey

When DC casting for 6xxx-, 7xxx- and 2xxx-series aluminum alloys, billet homogenization treatment is required to ensure microstructural and mechanical properties for later processing such as extrusion and forging. The homogenization recipe should be perfectly designed. Traditional 7xxx-series alloys such as 7075, 7050 and 7020 have not been a big headache for the engineers to define homogenization parameters. However, in the last decades, by introducing the new 7xxx-series, with high Zn (over 8%), the behavior of incipient phases starts to change during homogenization. The aim of this study is to determine the optimum homogenization system for extrusion process on 7055 aluminum alloys with an 8% Zn content. In experimental studies, different temperature and soaking time are applied to the billet. Microstructure of 7055 aluminum billet during homogenization is investigated by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and differential scanning calorimetry (DSC).

Sunil Soni, Pritam Kumar, and Vinay Maggu, Pranav Vikas India Pvt. Ltd., India

OEMs are focusing more on developing products with long life and high reliability in the current market scenario. The focus is more on components having long life in different vehicle operating conditions. One such requirement is to have SWAAT life for automotive condensers and evaporators of more than 40 days. The current alloy used in automotive condensers and evaporators is A1050/A1100/A3102 with SWAAT life of around 25 days.

This study focuses on benchmarking the current need of the automotive condenser and evaporator to achieve better SWAAT life in different vehicle operating conditions, and suggests an alternate aluminum alloy for multi-port aluminum tubes that meets SWAAT life of more than 40 days. Detailed testing for durability and SWAAT life are done on an alternate alloy, referred to as a long-life alloy, and are proven to use the same in the automotive condensers and evaporators.

Marcos A. Varayud, Xinquan Zhang, Rio Tinto – Aluminium, Australia; Saurabh Sedha, Rio Tinto – Aluminium, USA; and Nick C. Parson, Rio Tinto – Aluminium, Canada

Significant progress in the field of aluminum alloy development in the last three decades has resulted in the extensive use of alloy 6060 in the Australasian region. The alloy exhibits superior extrudability compared to alloy 6063 while still achieving 6063-T6 mechanical properties under normal production conditions. The lower magnesium content in the alloy offers the potential for greatly enhanced extrusion performance and improved mill and anodized surface finishes of extruded products. This paper reviews the key steps in the development of 6060 alloys by Rio Tinto, starting with the discovery of the Mg:Si ratio in the precipitates at the peak-age condition and subsequent work on various alloy variants tailored for specific customer requirements. The experience in the Australasian region with two 6060 alloys is presented, showing the benefits of using customer-tailored alloys for optimized performance considering the process capabilities at each extrusion plant.

Alex W. Lowery, Wise Chem LLC, USA

No other hazard in our industry has the potential of shuttering a workplace as a molten metal explosion. There are four hazards that many workplaces fail to address that commonly lead to explosions. This gap in knowledge is very dangerous, leading to workplaces needlessly suffering explosions injuring and killing workers. A review is presented of how molten metal explosions occur. The four hazards that cause countless explosions and how to prevent them are discussed. The case is presented that molten metal explosions are like no other hazard in the aluminum extrusion industry. Because of a lack of awareness and education, companies allow these four hazards to exist in their workplaces, leading to explosions. Failure to learn how to identify and correct these four hazards will result in the industry suffering more explosions.

John D. Schloz, Schloz Technologies LLC, USA

As we continue to improve our knowledge of the casting process, we must not limit our focus to the technology of the process or the parent equipment, but also to the materials that make up the consumables—casting rings. transition plates, lubricants and others. The consumable components of a casting technology are arguably the most critical to understand, in that it is these components that are in direct contact with the aluminum. This paper explores the technological aspects of consumables as well as how to properly install, prepare, and maintain them, thus assisting in optimizing the performance of the casting operation.