Recycling light metals: Optimal thermal de-coating

Kvithyld, Anne; Meskers, Christina; Gaal, Sean; Reuter, M.A.; Engh, Thorvald Abel

doi:10.1007/s11837-008-0107-y

Cited by 25 publications

(15 citation statements)

References 6 publications

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“…These reactions can lead to the formation of carbides in the alloy. The recycling-friendly coating removal practices proposed by the authors of [30], which involve the thermal treatment (pyrolysis) of scrap before it is smelted, may avoid this problem.…”

Section: Discussionmentioning

confidence: 99%

Analysis of Inclusions and Impurities Present in Typical HPDC, Stamping and Extrusion Alloys Produced with Different Scrap Levels

da Silva,

Pujante,

Hrabia-Wiśnios

et al. 2024

Metals

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The European Green Deal poses a two-pronged challenge for the automotive industry: migrating to solutions based on light structures, requiring lightweight concepts and light materials, while at the same time avoiding dependence on the importation of these advanced materials. Aluminium alloys are lightweight and cost-effective materials that can successfully meet the requirements of many structural applications; however, their production requires bauxite and other Critical Raw Materials (CRMs), such as Si and Mg. Aluminium alloys are fully recyclable, but scrap is usually contaminated and its use is related to an increment of impurities, tramp elements and undesired inclusions. Traditionally, the use of secondary alloys has been restricted to low-performance applications. The present work analyses the effect that the use of scrap has on the quantity of inclusions present in the alloy and on other properties relevant for material processing. This study was carried out using common alloys associated with three of the most common aluminium processes used in the car manufacturing industry: high-pressure die casting (HPDC) (AB-43500), extrusion (6063) and sheet metal forming (5754 and 6181). The reference alloys were mixed with different levels of scrap (0, 20, 40, 60, 80 and 100%), with an aim to keep the chemical composition as unaffected as possible. The inclusion level of the alloy was characterized using the Prefil Footprinter® test. In addition, the obtained materials, after being cast in an open mould, were subjected to metallographic characterization. Relevant properties were measured to assess the processability of the alloys for the corresponding transforming process using the flowability test for the HPDC alloy and high-temperature compression for the extrusion alloys. The results obtained suggest that the number of inclusions present in the melt highly increase with the amount of scrap used to produce the alloy. These inclusions are also related to a significant loss of flowability, but do not have a noticeable impact on microstructure.

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Section: Discussionmentioning

confidence: 99%

Analysis of Inclusions and Impurities Present in Typical HPDC, Stamping and Extrusion Alloys Produced with Different Scrap Levels

da Silva,

Pujante,

Hrabia-Wiśnios

et al. 2024

Metals

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“…In an incomplete combustion scenario with an oxygen-depleted atmosphere one can expect to find a mixture of all these molecules. [7] Increasing in the order CH4, CO, C4H10, CO2 have been shown to significantly increase oxidation of an aluminium melt compared to 5% O2 in Argon or pure Argon atmospheres [8]. Incomplete decoating where remnant pyrolysis products are left on aluminium samples have also been shown to reduce metal coalescence, increase dross formation and reduce yield compared to complete decoating process in which the coating and plastics are completely removed.…”

Section: Theorymentioning

confidence: 99%

Recycling of Aluminium from Mixed Household Waste

Eggen

Sandaunet

Kolbeinsen

et al. 2020

The Minerals, Metals &Amp; Materials Series

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Aluminium is used in packaging due to its density, strength and preservative capabilities. This paper outlines a methodology to evaluate the recyclability of aluminium waste, where parameters of scrap type, pre-treatment and remelting conditions are alternated in a factorial design, with measurements of yield and analysis of metal quality. In preliminary experiments three aluminium waste materials were evaluated for recyclability. The methodology was tested on one of the waste materials from mixed household waste, named Cans, and will be described in detail. Cans was decoated at 300 °C and 550 °C. The decoated material was then remelted, 4 separate additions of ∼ 2 kg per experiment, by submerging the sample material in molten aluminium. Porosity, oxide inclusion content and alloy composition were analysed to determine metal quality. The experimental results show that the yield of remelting, dross formation relative to melted sample material and the alloy composition of the remelted metal is dependent on decoating temperature. In conclusion: Cans is recyclable, with good quality and yield, when decoated before melting. Decoating at 550 °C improves metal yield and oxide inclusion content compared to decoating at 300 °C, however it also reduces magnesium content in the resulting alloy. Hopefully the methodology was useful for assessing the recyclability of an aluminiumrich waste and for evaluating the effects of various process parameters during recycling on metal yield and quality.

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“…The aim of the thermal de-coating process is to combust the carbonaceous materials without oxidizing the metal [63]. Firstly, the scission occurs where the coating decomposes, releasing hydrocarbons and leaving pigment/fillers/carbon residue.…”

Section: Decoatingmentioning

confidence: 99%

Preparation and Melting of Scrap in Aluminum Recycling: A Review

Capuzzi

Timelli

2018

Metals

182

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Abstract:This work provides an overview of the aluminum (Al) recycling process, from the scrap upgrading to the melting process. Innovations and new trends regarding the Al recycling technologies are highlighted. Aluminum recycling offers advantages in terms of environmental and economic benefits. The presence of deleterious impurities in recycled Al alloys is increasing and this is the main drawback if compared to primary alloys. The continuous growth of undesired elements can be mitigated by different technologies, preliminary operations and treatments, and by the optimization of the melting process. Downgrading and dilution are possible solutions to reduce the rate of impurities, but they are not sustainable if the final use of Al alloy continuously increases. The main objectives in the development of the Al recycling are shown and discussed. In particular, the evolution of preliminary treatments of the scrap, as sorting, comminution and de-coating, is reported and a review of the melting technologies is also presented. However, the choice of performing preliminary operations to the melting stage, thus improving the operating conditions during the furnace running, is a trade-off between costs and process efficiency.

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Recycling light metals: Optimal thermal de-coating

Cited by 25 publications

References 6 publications

Analysis of Inclusions and Impurities Present in Typical HPDC, Stamping and Extrusion Alloys Produced with Different Scrap Levels

Analysis of Inclusions and Impurities Present in Typical HPDC, Stamping and Extrusion Alloys Produced with Different Scrap Levels

Recycling of Aluminium from Mixed Household Waste

Preparation and Melting of Scrap in Aluminum Recycling: A Review

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