Research Article :
The study on the
extraction of Aluminium metal from industrial waste like aluminium dross (black
dross) to be used in the production of aluminium silicon hypereutectic alloy
and testing the resulted hypereutectic alloy chemically, physically, and
mechanically has been carried out. The amount of the black dross used undergoes
pretreatment by immersion the dross samples in tap water and settled overnight
to assure the maximum separation of nonmetallic, aluminium nitride, aluminium
carbide and aluminium oxide, the properties of tap water used for pretreatment
dross samples was recorded to see the effect of dross content on the tap water.
The pretreated dross samples were dried in electric furnace at 60ₒc
for 2hrs then samples of 60 gm remelted in a graphite crucible and amount of
flux(sodium chloride, potassium chloride, cryolite and calcium fluoride) (1:1)
is added, then different quantities of silicon lumps are added too. The
graphite crucible is put in the carbolite furnace at 800ₒc for 30 minutes.
The molten aluminium silicon is poured in specific moulds for the chemical and
physical examination, which shows the formation of aluminium silicon
hypereutectic alloys with good chemical, physical and mechanical properties.
Thus the dross is a great source for both aluminium metal high grade and
aluminium silicon hypereutectic alloy. Aluminium dross identifies as a
by-product forms during the aluminium production industry which contains
significant quantities of aluminium metal (up to around 70%). Most drosses are
a heterogeneous mixture of large lumps, fine oxides and small pieces of metal.
Aluminium dross is a combination of free metal and nonmetallic substances (e.g.
aluminium oxide and salts). Aluminium nitrides and carbides may
also be present, as well as metal oxides derived from the molten alloy [1]. It
has also been documented that dross should be stored in a dry environment since
reactions of carbide or nitride of aluminium and calcium can form acetylene and
ammonia [2]. Drosses may be classified by means of their metal content. Drosses
with a high metal content (white, or wet, dross that is rich in free metal)
typically occur as a compact material in large clotted lumps or blocks. A low
metal content typically occurs when scrap is remelted with salts in an open
hearth furnace. This black, or dry, dross is usually granular with a high metal
content in the coarse fraction and chiefly oxides and salt in the fines [1]. General
discussions of the treatment of drosses and related products have been given by
Bahr and Kues [3] and Shen and Forssberg [4]. Characterisation work has been
reported by Hagni [5], Manfredi, Wuth, and Bohlinger [6], and Bruckard and
Woodcock [7]. Data on the recovery of aluminium by comminution and sizing have
been presented by Fair et al. [8] and by electrostatic separation by Mah,
Toguri, and Smith [9]. Flotation
of aluminium from dross has been reported by Soto and Toguri [10] and Bruckard
and Woodcock [7]. The present paper discusses the production of aluminium metal
high grade as the aluminium metal high grade produced from alumina
electrolysis, the aluminium metal from dross is then used to produce aluminium silicon hypereutectic
alloy
with good chemical, mechanical and physical properties. Sample
preparation Black
dross samples (6063 alloys black dross) are taken from the Aluminium company of Egypt, these samples
immersed in tap water (PH = 7.5 & Conductivity = 0.35 µ Mohs & T.D.S =
178 mg /L) to get rid of the nonmetallic oxides then settled overnight to
assure the maximum removing of these nonmetallic oxides, the treated
samples were dried in an electric furnace at 60ₒc for 2hrs (Figures 1 & 2). Procedures The
treated dried black dross samples are re-melted in graphite crucibles in the presence
of flux with adding amounts of pure silicon lumps in carbolite furnace at 800oc
for 30 minutes. The molten Al-Si hypereutectic alloy poured into specific
moulds for chemical and physical examination. Tensile test Standard
tensile test specimens were also prepared in accordance to ASTM B557M “Methods for Tensile Testing of
Metals”
and their tensile strengths determined using ZWICK / ROELL Z 150 TL. The elongation
was determined for each sample. Hardness test By Wolpert DIA –
TESTOR 3 b:
An indenter (hard metal ball with diameter D) is forced into the surface of a
test piece and, after removal of the force F, the diameter of the indentation d
left in the surface is measured. The Brinell hardness is proportional to the
quotient obtained by dividing the test force by the curved surface area of the
indentation. The indentation is assumed to retain the shape of the ball, and
its surface area is calculated from the mean indentation diameter and the ball
diameter. Microstructural
analysis The
microstructures of the samples were observed and taken using Olympus E330 – ADU1.2X. The
chemical composition of 6063 alloy that black dross samples were taken from to
recover aluminium metal and produce aluminium silicon hypereutectic alloy (Table 1). The
aluminium metal recovered from
black dross samples that could react with silicon lumps is up to 82% of the
immersed and dried samples, the presence of the flux and the lumps shape of the
silicon used increase the reactivity of the silicon with aluminium molten and
the flux also protects both of silicon lumps and aluminium metal from
oxidation, the lumps shape of the silicon causes the silicon to sink in the
molten aluminium and thus protects the silicon from oxidation too (Table 2). The chemical composition of the Al-Si
hypereutectic alloy in Table 2 shows the silicon content in the alloy which indicates the
success in formation of the Al-Si hypereutectic alloy from the aluminium metal
recovered from 6063 alloys black dross and pure silicon lumps, the presence of
flux plays an important role to protect both aluminium metal and silicon from
oxidation, and saves a good barrier to prevent the recontamination of the alloy
with the nonmetallic presents surrounding the hypereutectic
alloy. The flux reduces the impurity
elements, like Na, Ca, and shows a great decrease in the Mg content in the
hypereutectic Al-Si alloy. The mechanical examination, tensile strength,
elongation and the microstructural images show good properties, and the microstructural
images show the hypereutectic Al-Si alloys
without the presence of flux particles in their layers after solidification due
to difference in densities between the alloy formed and the flux with
nonmetallic oxides. Conclusion It is established that 6063 alloys black dross is a
great source for aluminium metal high grade instead of being dumped and
landfilled which affects the environment, the soil, the underground water and
the aluminium
industry itself, this dross is used to produce
aluminium silicon hypereutectic alloy with the presence of flux to get rid of nonmetallic
oxides and to protect the aluminium metal and silicon
lumps from oxidation. The Al-Si hypereutectic
alloy produced shows good mechanical and microstructural properties. The flux
reduces the impurity elements, like Na, Ca, and shows a great decrease in the
Mg content in the hypereutectic Al-Si alloy. Acknowledgments This
work was financially supported by the Future Science for Waste Disposal &
Treatment. (FSC) Egypt Grant number 1 R01 FSC 656376-02A1.
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Aluminium Silicon Hypereutectic Alloys from 6063 Alloy’s Black Dross Using Silicon Lumps and Flux
Abstract
Full-Text
Introduction
Experimental
Results
Discussion
References
*Corresponding author
Ahmed S Aadli, Chemistry labs, Aluminium company of Egypt, Egyptalum, E-mail:Ahmed.S.Aadli@sci.aswu.edu.eg
Citation
Aadli AS. Aluminium silicon hypereutectic alloys from 6063 alloys black dross using silicon lumps and flux (2018) Edelweiss Chem Sci J 1: 21-23
