pushing the limits of formability: a new aluminium outer skin sheet product for most demanding car...

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




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


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




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


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


� 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)


� 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


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




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


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


* 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


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


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


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


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


� 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


� 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


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

pushing the limits of formability: a new aluminium outer skin sheet product for most demanding car...

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