High-Shear De-Gassing and De-Ironing of an Aluminum Casting Alloy Made Directly from Aluminum End-of-Life Vehicle Scrap

Abstract

High-shear melt conditioning (HSMC) technology was used for degassing and de-ironing of an aluminum alloy recovered from the Zorba cast fraction of the non-ferrous scrap from shredded end-of-life vehicles. The results showed that the recovery of aluminum alloys from the Zorba cast fraction was more than 80%. High-shear melt conditioning improved the degassing process during melt treatment in comparison with the adding of degassing tablets. The efficiency of the de-ironing process using HSMC increased by up to 24% after, increasing the Mn content to 0.8% in the melt. Adding Mn to Zorba melt enhanced the de-ironing process and eliminated the formation of β-AlFeSi intermetallic particles, which have a detrimental effect on both the mechanical and corrosion properties of the alloy.

Degassing of Aluminum Alloy Melts by High Shear Melt Conditioning Technology: An Overview

“…The main studies during the technology's development and testing have been conducted on the secondary aluminum alloy, with an approximate composition of Al-(6.8-7.5)Si-(0.3-0.5)Mg-(0.12-0.25)Fe, i.e., an A356/LM25-type alloy [24,32]. However, the technology has also been successfully tested on other aluminum alloys such as the A380/LM24 [42] and Silafont-36 (AlSi10MnMg) [43] HPDC alloys, the Zorba cast fraction scrap (~LM27) [44], the 7032 [31,45], 7075 [9,40], and 2024 [46] wrought alloys, and also for recycling the A20X alloy (Aeromet [47]) prepared from recovered scrap material. In all these cases, a significant reduction in hydrogen and in oxide bifilm content were found, when compared to conventional rotary degassing.…”

“…The cooling rate is an important mechanism to refine the microstructure. Besides, the mechanism including degassing melting has also refined the resulting microstructural array [26,44]; consequently, it has an important role upon the distinctive material's properties [53][54][55].…”

“…The cooling rate is an important mechanism to refine the microstructure. Besides, the mechanism including degassing melting has also refined the resulting microstructural array [26,44]; consequently, it has an important role upon the distinctive material's properties [53][54][55]. Figure 8 shows an example of the typical fracture surfaces of postmortem tensile bars and how they change depending on the effectiveness of the degassing method used.…”

Aluminum Melt Degassing Process Evaluation Depending on the Design and the Degree of the FDU Unit Graphite Rotor Wear

“…This method involves injecting a rinsing gas into a liquid alloy through a rotating impeller [ 21 , 22 ]. Currently, the rinsing gas is usually nitrogen or argon; however, active gases such as chlorine, freon, fluorine or mixtures thereof with nitrogen or argon have also been used in the past [ 23 ]. Rotary degassing provides smaller and more evenly distributed rinsing gas bubbles, which is advantageous in terms of removing dissolved hydrogen as well as removing inclusions.…”

“…On the other hand, the process window, in which the processing produces a better melt quality, is small and particularly sensitive to small changes in process parameters. When fluxes are not used, the operating parameters of rotary degassing units are usually optimized for efficient removal of dissolved hydrogen [ 23 , 24 , 25 , 26 ]. These parameters include (and are not limited to) rotor geometry, retaining vessel and rotor dimensions, amount of metal, rinsing gas flow rate, impeller speed, treatment time, use of deflectors, initial and planned volume of hydrogen, melt temperature, chemical composition of melt and other environmental factors (such as atmospheric humidity and gas pipelines used) [ 27 , 28 ].…”