BRIQUETTING OF ALUMINUM ALLOY CHIPS WITH
CONTROLLED IMPACT
Todor Penchev, Stanislav Gyoshev, Dimitar Karastoianov
In this paper is investigated the possible to produce brackets from chips of two
types of aluminum alloys. Chips of different shapes and sizes are compared, some
of which are free of water and oil (cleaned chips), while the rest are left without
cleaning (soiled chips). It has been found that the density of the briquettes
produced by the cleaned and uncleaned chips is the same, and is about 93 % of
density of the solid alloy. This high density allows obtaining a workpieces by
subsequent plastic deformation. Upsetting and reverse extrusion of the briquettes
were studded. The results show that may be accomplished a large extent of
deformation of the briquettes when using processes with predominant compressive
stresses.
Keywords— briquetting, chips briquetting, impact briquetting.
1. INTRODUCTION
For briquetting of metal chips are used mechanical and hydraulic presses with
nominal force of several hundred to several thousands of kN. To obtain briquettes
with good density the ratio H/D for different materials vary within wide limits (H /
D = 0,8-0,25), where H is the height, and D is the diameter of the briquette. The
greater is the density of the briquettes, the smaller are the losses in the transport
and melting. Basic data used to evaluate the effect of briquetting operation are
specific density of the briquette (ρ), g/sm3, and specific contact pressure for
briquetting (p), MPa.
At briquetting with hydraulic presses it is achieved 60% - 75% briquette’s
density in comparison with solid material density. The specific pressure reaches
values p = 200-400 MPa, in briquetting of steel chips [1, 2].
Due to the large size of briquetting presses, large power consumption, and
relatively low productivity, methods are searching to improve the efficiency of this
process. One such method is high velocity impact briquetting [3, 4].
In [5] are presented the results of use of high velocity explosive presses for
briquetting of metal chips. The obtained briquette’s density is (g/sm3): aluminum
alloy - 2.2 to 2.4 (2.7 to 2.75); carbon steel - 5.0 to 5.5 (7.85); alloyed steel - 5.0 to
5.5 (7.48 to 8.0). In parenthesis is given the density of the respective solid metal.
As a major drawback of this briquetting method is the impossibility of process
control.
1
In [6] is described construction of die forging hammer propelled by industrial
rocket engine. Whit this machine is possible to work with controlled impact and
with impact velocities from 4,5 m/s up to 20 m/s. Laboratory set-up for controlled
impact, and the results of experimental study of metal chips briquetting by
controlled impact with impact speed of 7 m/s are presented in [7].
Before briquetting chips are cleaned from residues of water and oil, which
raises the cost of the production process. In this paper the possibility of briquetting
of uncleaned chips is studied.
It is shown in [7] that it is possible to obtain briquettes from aluminum alloy
chips with density close to density of the solid alloy. The potentiality to produce
parts using such briquettes is also investigated.
2. Laboratory set-up
The laboratory set-up is shown in Fig.1. The falling part 13 is accelerated by
cold rocket engine 12, working with compressed air. The trust R of the engine is R
= 226 N. Maximum height of fall and impact speed with 9.12 kg falling part mass
are 1.1m and 7 m/s respectively. Largest impact energy is 223 J. In Fig.2 are
presented controlled impact schemes of the device. Specific scheme of work is set
by the control unit 16 and is performed by sensors 4, 5, 10, 11, 15.
a)
b)
Fig. 1a. A laboratory set up for studying of collision processes: 1 – base plate
with a mass of 235 kg; 2 – lower fixed body for elastic impact; 3 – lower fixed tool
2
for plastic impact; 4 – induction speed sensors; 5 – air on/off induction sensor; 6 –
guides for the falling part; 7 – trigger mechanism; 8 electro-magnetic valve; 9 – air
pressure control valve; 10 - air ‘On’ sensor; 11 – receiver of the light sensor for
speed; 12 – cold rocket engine; 13 – 6,17 kg mass falling part; 14 – plate for
activation of sensors 4, 5 and 11; 15 – light speed sensor emitter; 16 – electronic
control board; Fig. 1b. Impact schemes of the device from Fig.1a: 1- free fall
(max.Vi =4.5 m/s ); 2 – free fall with additional force R at the time of impact
(controlled impact with max.Vi =4.5 m/s); 3 – fall with acceleration by a rocket
engine, without additional force in the time of impact (max.Vi = 8.5 m/s); 4 - fall
with acceleration by rocket engine + additional force R in the time of impact
(controlled impact with max.Vi = 8.5 m/s )
3. Methods
In Fig.3 are shown the chips used in the experiments. To account for the
influence of the size and type of chips used in the present work (type A) are
compared with those of work [7] (type B). In order to investigate the influence of
the residual water and oil on the density of the briquettes produced by the impact
briquetting part of the type A chips were cleaned (type AC) while others had been
left uncleaned (type AUC). Table 1 shows data on chips chemical composition.
Fig.3. a- chips used in present paper (type A); b – chips used in [7] (type B).
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Diameter of the produced briquettes is 20 mm, as it is the hole of the die for
briquetting. Diameter of the punch is 19.6 mm. The gap between the die and the
punch is left out to ensure exit of the air that remains between the chips in the
filling into the die.
Table 1. Chemical composition of Al-alloy
Alloy
Al
Mg
Mn
Ni
Si
type
A
91.0
2.0
5.0
2.0
B
97.9
1.2
0.90
ρs is the density of solid Al-alloy
ρs
2.78
2.71
Briquetting is carried out using controlled impact (regime 4 in Fig.2) and with
maximum impact energy of 223 J. In order to investigate their density and
structure the obtained briquettes are measured, weighed on an analytical balances
and pictured on 3D X-ray tomography (Nikon XTH 225 Compact Industrial CT
Scаnner).
Impact process is recorded with a high-speed camera. The video is processed
with the software Vicsasso 2009 which defines impact speed (Vi) and acceleration
(ai). The impact force Pi and impact energy Ei are calculated by formulas
, N,
(1)
, J,
(2)
where m is the mass of the falling part, in kg.
The specific impact energy for briquetting is calculated by the formula
, J/sm3,
(3)
3
where Θ, sm , is the briquette volume. The use of this indicator makes it possible
to compare the results obtained under different conditions of briquetting.
3. Results
3.1. Briquetting
In Fig.4 are shown the diagrams for velocity and acceleration by one of the
experiments. It can be seen from Fig.4c that acceleration is very high - 1610 m/s2
4
(164 g, were g is the acceleration of gravity). Due to the action of the thrust of the
rocket engine during the impact, the rebound is small – 28 mm (the coefficient of
restitution e = 0.158) – Fig.4a.
a)
b)
Fig.4. Diagrams for: a – velocity; b –acceleration in controlled impact briquetting
Fig.5. A1-A4 - briquettes from cleaned chips (type AC); AM1-AM4 – briquettes
from uncleaned chips (type AUC)
Briquettes shown in Figure 5 are further processed by removing the protrusions,
weighting and scanning. In Table 2 are shown the obtained data from the
experiments. The average density for the briquettes received from cleaned and
uncleaned chips is the same and is approximately 2.53 gr/sm3. The average impact
acceleration is about 1600 m/s2 (164 g).
Table 2. Parameters of controlled impact briquetting process
Vi,
Briquette
A1
A2
A3
A4
average
AM1
AM2
AM3
m/s
7.12598
7.16733
6.80936
7.17096
7.068408
7.1024
7.1563
6.95581
ai,
m/s2
1609.823
1611.719
1494.162
1631.31
1586.754
1654.62
1695.654
1609.755
Hreb,
mm
1.597
1.862
1.743
2.242
1.861
1.713
1.795
1.398
Нbriq,
sm
0.461
0.474
0.488
0.506
0.48225
0.461
0.482
0.474
Dbriq,
sm
2.013
2.013
2.011
2.008
2.01125
2.011
2.012
2.012
ϴ,
sm3
1.466419
1.507772
1.549222
1.601576
1.531247
1.463507
1.531696
1.506274
5
mbriq, gr
3.7346
3.7771
3.8545
4.1275
3.8734
3.7687
3.8364
3.8442
ρ, gr/sm3
2.546748
2.505088
2.488023
2.577149
2.529252
2.575116
2.504674
2.552125
Ei,
J
231.5549
234.25
211.4353
234.4874
227.9319
230.025
233.5296
220.6278
Es , J/sm3
157.905
155.3617
136.4784
146.4104
149.0389
157.1739
152.4647
146.4726
Рi,
N
14681.59
14698.88
13626.76
14877.55
14471.19
15090.13
15464.36
14680.97
AM4
average
7.19591
1640.078
1.927
0.478
2.01
1.515967
3.7891
2.499461
236.1219
155.7567
14957.51
7.102605
1650.027
1.70825
0.47375
2.01125
1.504361
3.8096
2.532844
230.0761
152.967
15048.24
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Hreb – rebound of the punch; mbriq – mass of the briquette
In Fig.6 is shown the scanned picture of an Al-alloy briquette. It is seen from
Fig.6a that the highest density is in the middle area which covers about 0.5 D briq.
From the vertical sections (Fig.6b, Fig.6c) it can be seen that the density is the
lowest in the peripheral areas of the briquette. Because of the little impact time the
air cannot be forced out of the briquette and remains in these areas. When using a
large thrust R of the engine and it acts for a longer time, this air can be removed to
obtain a briquette having a density of solid alloy. Such a briquette may be used to
prepare parts by machining or by plastic deformation. This subject will be
discussed below.
In Fig.6b, Fig.6c in the middle of the briquette heights there is a line which
shows the material stratification. This defect in our opinion, is caused by the
distribution of tensile plastic waves and has no bearing on the quality of briquettes.
In the manufacturing of parts from such briquettes it can be removed by
subsequent plastic deformation.
Fig.6. Photos of X-ray tomography briquette of Al - alloy: a - cross-section in the
middle of the briquette height; b, c - orthogonal vertical sections through the center
of the briquette; d - 3-D image
3.2. Plastic deformation of the obtained briquettes
Due to the high density of the obtained briquettes the possibility of plastic
deformation was studied. Three of the briquettes were deformed by upsetting on
Instron test machine with maximum force 100 kN. On Fig.7 is shown one of the
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resulting specimens with relative deformation ε = 17 %. None significant defects
are seen in the surrounding surface and in the volume of the deformed briquette.
Fig.7. X-ray tomography of vertical section of deformed by upsetting briquette
Four of the briquettes (two AC and two AUC) were deformed by reverse
extrusion – Fig.8. In this case for deformation is used Hydraulic press with
maximum force 400 kN. Wall thickness of the specimen is 2 mm. It can be seen
that the bottom aria, which is deformed by pressure, is realized very large
a)
b)
c)
Fig.8. Photos of X-ray tomography of deformed by reverse extrusion briquette:
a - cross-section in the middle of the briquette height; a - vertical section through
the center of the briquette; b - cross-section in the middle of the specimen height; c
- 3-D image
deformation without defects. On the walls of the specimen are noted transverse
defects, which are obtained by the action of the tensile stresses. From these results
it can be concluded that the schemes of deformation with predominantly
compressive stresses can obtain parts without defects, while the schemes of
deformation with predominantly tensile stresses are obtained parts with poor
quality. It is necessary to be carried further and more extensive research in this
field.
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4. CONCLUSIONS
The studies reveal that it is possible to obtain high-quality briquettes from
aluminum alloys chips by controlled impact, regardless of the type and size of the
chips. The advantages of this method are as follows:
• Allows to obtain briquettes with a high density using chips which are not
cleaned from residues of water and oil. Dropping out of the cleaning operations
will reduce production costs for briquetting. This technology can be used only in
cases where the briquettes will be used for melting.
• The density of the obtained in this work and in [7] briquettes is 93% - 96% of
the density of the respective solid materials. Applied specific impact energy is Es =
150 J/sm3 and the thrust of a rocket engine, which provides additional pressure
during briquetting is R = 224 N. Using industrial hammer propelled by a rocket
engine described in [6], can be achieved much larger values of Es and R, which
makes it possible to produce briquettes from aluminum alloys chips with a density
very close to the density of solid metal.
• Greater density of the briquettes from Al - alloys allows obtaining a
workpieces by subsequent plastic deformation when using processes with
predominant compressive stresses (upsetting, die forging, extrusion). In this case,
for obtaining of briquettes should be used free of water and oil chips. These
options require further research for each separate workpiece type.
Acknowledgments
This research was performed with the support of the Bulgarian Scientific
Fund Grant ID 02- 262/2008 and by the project AComIn "Advanced Computing
for Innovation", grant 316087, funded by the FP7 Capacity Programme (Research
Potential of Convergence Regions).
References
[1]. Stepanskii L.V., Metal waste briquetting, Mashgis, 1975, (in Russian).
[2]. http://www.johnhartinternational.com/briquetting/
[3]. Poljakov A.P., Zalazinskaja E.A., Impact extrusion of powder material billets,
Zvetnaja metallurgia, 2003, 1, 30-35, (in Russian).
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[4]. Wang J., Yn H., Qu X., Analysis of density and mechanical properties of high
velocity compacted iron powder, Acta Metallurgica Sinica (English Letters), v.22,
6, 2009, 447 – 453.
[5]. Stepanov W.G., Shavrov I.A., High energy impulse methods for metal
working processes, Mashinostroenie, 1975, (in Russian).
[6]. P. Bodurov, T. Penchev, Industrial rocket engine and its application for
propelling of forging hammers, Journal of Materials Processing Technology, 2005,
161, 504-508.
[7]. T.Penchev, I.Altaparmakov, Experimental Investigations on “Controlled
Impact” Effect, International Conference METAL 2013, Brno, 15-17.05.2013.
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