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Pushing the limits of formability: A new aluminium outer skin sheet product for most demanding car body parts
Dr. Sabine Philippe, Dr. Petar RatchevBad Nauheim, May 11, 2016
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Agenda
1. Constellium
2. Drivers and strategy for skin alloy development
3. A new aluminium outer skin sheet product
2A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016
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Agenda
1. Constellium
2. Drivers and strategy for skin alloy development
3. A new aluminium outer skin sheet product
3A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016
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An introduction to Constellium 2015
Constellium is a leader in innovative aluminium -based solutions
Over 10,000 full-time employees
€5.2 billion in sales
22 manufacturing sites
C-TEC, our world-class Technology Center
Headquartered in Amsterdam , The Netherlands.
Corporate offices in Paris , France, Zurich , Switzerland and
New York , USA
2015 key figures
411.05.2016A new aluminium outer skin sheet product for most d emanding car body parts
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� Second largest-volume, fully integrated rolling mill in Europe
� World-class recycling center
� Integrated hot/cold-rolling line
� Joint venture with UACJ (Japan), majority owned by Constellium
NEUF-BRISACH, F SINGEN, D
Bowling Green , KY, US (under construction)
Expanding our automotive body sheet capacity
5A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016
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Our auto body sheet portfolio with increasing performance
6
Strongalex®Ultralex®
Securalex®Securalex® HS
Surfalex®Surfalex® HSSurfalex® HF
Formalex®Plus
Strength/Mech.Resistance Crash Design & Style
SurfaceAspect
PRODUCT PERFORMANCE
For replacement of high strength steel parts
and further down gauging
For parts which need energy absorption
For all visible parts
For parts with complex design
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016
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Agenda
1. Constellium
2. Drivers and strategy for skin alloy development
3. A new aluminium outer skin sheet product
7A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016
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Challenges for skin alloy development
surface quality :orange peel,
roping defects
hemming
corrosion resistance
in-service strength(dent resistance)
deep drawing, stretch forming
sharp lines
In-service performance Ability to form the part
Improving formability, while maintaining a high level of in-service properties
8A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016
edge-cracking
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Edge-cracking improvement
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016 9
� Optimized hole geometry:
� Significant improvement by increasing local curvatures in critical areas
� Material optimization:
� Higher elongations lead to higher crack resistance
0
0,1
0,2
0,3
0,4
0,5
5182 6016
Hol
e E
xpan
sion
Rat
io
HE
R =
(D
f-D
0)/D
f
die-cut laser-cut� Cutting quality:
� Significant influence of the cutting process and parameters
� Laser cutting results in higher max. edge strain than press trimming process
old holegeometry
new holegeometry
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Formability improvement� Material optimization:
� Higher FLC0 to delay cracks
� Higher work hardening at high strains
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016 10
� Reduced friction:
� To allow material to flow and more homogeneously distributed deformation
� Design optimization:
� The height to radius ratio is important when designing for aluminium
28
32
36
40
44
0,060,080,10,120,140,16
dept
h at
1st
cra
ck (
mm
)
friction coefficient
oil-based drylube
ester-based drylube
red = previous designblue = modified design to solve formability issues
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Current design requires sharp character lines
� Sharp character line on the part = small external radius (internal tool radius + ~sheet thickness)
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016 11
� Material optimization:
� Higher work hardening at high strains
� Stretch-bending tests
� We test the alloy ability to form sharp lines on laboratory scale using stretch-bending
� Optical measurement of the outer radius
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Development strategy of new aluminium skin alloys
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016 12
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,00 0,10 0,20 0,30
n-va
lue
true strain
current alloy targeted alloy� We use numerical simulation to define the
material needs for real parts. From virtual alloys that allows a given part to be formed we have developed the chemical composition and process route to achieve mechanical properties
� Several traditional target material properties (n5, r10, ∆r, A80, etc) are insufficient indicators of the ability to form real, complex part in 6xxx-series aluminium alloys
� Key development target for us is enhanced work hardening at high strains
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Agenda
1. Constellium
2. Drivers and strategy for skin alloy development
3. A new aluminium outer skin sheet product
13A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016
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New aluminium skin alloy: Surfalex® HF
Surfalex® HF gives an improved formability of 10-15% vs. incumbent skin alloys, without compromising any other requirement of outer skins
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016 14
In-service strength(dent resistance)
Corrosion resistance
Roping
Orange peel
Stretch forming & Stretch bending (sharp lines)
Deep drawing
Hemming
Hole expansion
Ability to form the partIn-service performance
Surfalex®
Surfalex® HF
conventional 6016
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New aluminium skin alloy: Surfalex® HF
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016 15
* 2% + 20’@185°C
Si Fe Cu Mn Mg Cr Zn TiSi Fe Cu Mn Mg Cr Zn Ti
1,0 – 1,5 <0,50 <0,20 <0,20 0,25 – 0,60 <0,10 <0,20 <0,15
Ag% A80%Surfalex® 22 25Surfalex® HF 26 29
16
18
20
22
24
26
28
30
elon
gatio
n (%
)
Typical average of Ag and A80 Typical in-service* strength
Rp0.2Surfalex® 210Surfalex® HF 210
50
70
90
110
130
150
170
190
210
230
in-s
ervi
ce s
tren
gth
(MP
a)
� Composition range within AA6016:
� Significant increase of elongations while maintaining the same in-service strength:
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0,18
0,2
0,22
0,24
0,26
0,28
0,3
0,32
0,34
-0,2 -0,1 0 0,1 0,2 0,3 0,4
maj
or s
trai
n
minor strain
Surfalex
SurfalexHF
Optimized for forming of complex parts
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016 16
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0 0,05 0,1 0,15 0,2 0,25
n va
lue
true strain
Surfalex
SurfalexHF
� Higher strain hardening at high strains, for improved stamping and better ability to form sharp “character” lines
� Forming limit curve is improved, particularly in plane strain, enabling the forming of complex and deep parts
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17
Improved formability validated experimentally …� The LDH (Limiting Dome Height) test aims to reproduce press conditions in a simple,
fast laboratory procedure
� This test shows good correlation with plane-strain industrial failures
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016
120 mm
160 mm
0° or 90°
24
25
26
27
28
29
30
Surfalex® Surfalex®HF
Lim
iting
dom
e he
ight
=
hei
ght a
t fai
lure
(m
m)
0°
90°
hemispherical punch + lock beads
sample dimensions
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18
Improved formability validated experimentally…S
urfa
lex
®
Sur
fale
x® H
F
� Constellium in-house stamping trials using difficult door inner tooling
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19
… and numericallyS
urfa
lex
®
Sur
fale
x® H
F
� Surfalex® HF gives clear formability improvement both in simulation and in prototype stamping trials of difficult parts
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2
3
4
5
6
7
10 15 20 25 30
oute
r ra
dii (
mm
)
punch displacement (mm)
Surfalex® -r=1
Surfalex®HF -r=1
Surfalex® -r=2
Surfalex®HF -r=2Surfalex®
/r=1
“Sharper” lines can be achieved
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016 20
� In this stretch-bending test, a high punch displacement is the key indicator of the ability to form sharp lines. The given outer radii values depend on the tool geometry & setup.
� Lower outer radii can be obtained with Surfalex® HF
Interrupted stretch-bending tests at different punch displacements
(up to failure) & opticalmeasurement
Surfalex®HF /r=1
Surfalex®HF /r=2
Surfalex® /r=2Max. punch displacement before
failure is indicated by an arrow
/r=1
/r=1
/r=2
/r=2
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Additional relevant forming properties
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� Surfalex® HF also shows a lower in-plane anisotropy, that means a more similar forming behavior in the 3 directions, and good hemming aptitude
► r-value
153 155
0
20
40
60
80
100
120
140
160
180
Surfalex Surfalex HFbe
ndin
g an
gle
(°)
► bending angle:
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
Surfalex Surfalex HF
r-va
lue
(8-1
2%)
0° 45° 90°
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Perfect surface aspect and corrosion resistance complying with skin products
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016 22
NOK OK
� Trend towards thinner paints mean less tolerance for surface disturbance and/or roping lines after forming: excellent surface quality of Surfalex® HF
� Good corrosion resistance: IGC results within specifications
� IGC:
4
� roping:Surfalex® HF
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 100 200 300 400 500
Cum
ulat
ive
dist
ribut
ion
of 2
5 m
easu
rem
ents
Depth of attacks (µm)
Surfalex®
Surfalex®HF
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Summary
� Key trend for skin alloy developments = very few design compromises when converting from steel to aluminium.
� High formability is required (more complex and deep parts, sharp lines, …)
� Key forming parameter is strain hardening at high strains
� We now offer a new skin outer alloy: Surfalex® HF with significant improvements vs incumbent Al alloys
� improved stamping of complex parts, including bodysidepanels
� better ability to form sharp “character” lines
� and with no compromise in
� in-service strength
� hemming performance
� surface aspect quality
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Automoti
ve Circl
e International09/05/201624www.constellium.com
�THANK YOU VERY MUCH
�VIELEN DANK FUR IHRE AUFMERKSAMKEIT
�MERCI BEAUCOUP POUR VOTRE ATTENTION