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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
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
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
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
� 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
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
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
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
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
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
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
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
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
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
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:
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
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
18
Improved formability validated experimentally…S
urfa
lex
®
Sur
fale
x® H
F
� Constellium in-house stamping trials using difficult door inner tooling
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016
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
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016
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
Additional relevant forming properties
A new aluminium outer skin sheet product for most d emanding car body parts 11.05.2016 21
� 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°
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
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
Automoti
ve Circl
e International09/05/201624www.constellium.com
�THANK YOU VERY MUCH
�VIELEN DANK FUR IHRE AUFMERKSAMKEIT
�MERCI BEAUCOUP POUR VOTRE ATTENTION