07 - The Application of Multiphase Steel in the Body in White

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w w w . a u t o s t e e l . o r g

The Application of Multiphase Steel

in the Body-in-White

Dr.-Ing. Markus PfestorfBMW AG

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1. Demands on materials

2. Functionality

3. Mechanical data of sheet materials

4. Material grade application

5. Forming

6. Joining

7. Summary and outlook

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Forming

•Formability•Punch force•Forming limit diagram

•Cutting•Cutting forces•Spring back

Joining

•Spot Welding•Adhesive Bonding

•MIG welding •MIG brazing•Laser welding•Riveting

Surface/Corrosion•Class A surface•Adhesive bonding

•Paint adhesion•Contact corrosion

Functionality

•Ductility during crash (Rp0,2, Rm, A80, …)

•Fatigue strength•E-Modulus (stiffness)•Weight (density)•Frequency attenuation

•Acoustics

Process: Press-Shop Body-in-White Paint Product

Demands on MaterialProcess and Product

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– EURO-NCAP, 64,4 km/h, 40 %– US-NCAP, 56,3 km/h, 100%– Pole (front), 50 km/h, middle

- IIHS low speed, 8 km/h, others,- AZT-front/rear, 15 km/h, 40%- FMVSS 201- FMVSS 208- Roof hitting test- Roll over

– JAPAN-NCAP, 55 km/h, 90°– US-LINCAP, 62 km/h– Pole (side), 29 km/h– IIHS side, 50 km/h

– BMW rear, 50 km/h, 40 %– US-FMVSS 301, 80 km/h, 70 %

FunctionalityParameters for Crash Performance

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Data for rear crash– Car weight: 1978 kg

– Barrier weight: 1365 kg

– Barrier speed: 81,7 km/h

Results:– No impact of fuel tank

– No impact in passenger cabin

– No brittle fracture of trunk lid

FunctionalityCrash Testing (BMW 6 series coupé)

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FunctionalityStiffness

BendingTorsion

f ~ cm

Inflated scale

22,8

24,8

2929,8

22

24

26

28

Hz

32

E28(1981)

E34(1988)

E39(1995)

E60(2003)

1. T

orsi

on28

20,621,8

2626,5

20

22

24

Hz

1. B

endi

ng

E28(1981)

E34(1988)

E39(1995)

E60(2003)

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Bending

Torsion

FunctionalityStiffness

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Yield strength Rp0,2

Elo

ngat

ion

at fr

actu

re A

80

Mechanical DataSheet Steel

0

5

10

15

20

25

30

35

40

%

50

0 200 400 600 800 1000 N/mm² 1400

TWIP-steel

Work hardened

Stainlesssteel

deep drawing steel

6xxx(T4)

5xxx

6xxx(T6)

Micro alloyed

IF

BakeHardening

phosphorus alloyed steel

MS

CPDP

TRIP

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0

200

400

600

800

1200

0 0,1 0,2 0,3 0,4Forming rate

Yie

ld s

treng

thR

p0,2

H400T(TRIP700)

H420LA (ZSTE420)

Nmm²

Mechanical DataComparison: H400T H420LA

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Yie

ld s

treng

th R

p0,2

0

200

400

Nmm²

800

(Supplier data)

Forming

Work hardening

Paint oven

Bake hardening

Final value of finished products

Delivery values before forming

H300LA (Micro-alloyed)

H300B (Bake-hardening steel)H300X (Dual-phase steel)

Mechanical DataWork and Bake Hardening Effects

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BMW 3 Series(SOP 1997)

Deep Draw Steels

180 N/mm²

200 -220 N/mm²

260 N/mm²

300-340 N/mm²

380-420 N/mm²

500-680 N/mm²

> 900 N/mm²

AlMg aluminum

AlSi aluminum

Plastics

Others




Percentage of material (body in white incl. hang on parts)

Material Grade ApplicationIncreasing Utilization of HS Steels

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Material Grade ApplicationDetailed Case Study: BMW 3 Series

Others1%

Deep drawing steel19%

180 N/mm²19%

200 -220 N/mm²11%

260 N/mm²9%

300-340 N/mm²22%

380-420 N/mm²12%

500-800 N/mm²6%

SteelOther steelDC 03/04DX 54DX 56H180B, H180YH220B, H220YH260B, H260Y, H260LAH300B, H300LA, H300XH340LA, H340XH400TH420LAD680CDocol1000Plastics/othersPlasticsOthers

>900 N/mm²1%

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Multi-phase steel grades

Load path for frontal impact

• Deformable front• Rigid passenger

cabin

Load path for side impact

Material grade applicationImpact load path at the BMW 3 series

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Material grade application Benefit of Multiphase steel

0

50

100

150

200

kg

300

Previous 3 seriesweight: 284 kg,functionality ´98(size of new 3 series)

Wei

ght b

ody

in w

hite

Multiphase steelHigh strength steelLow strength steel < 180N/mm²

55%

45%

Weight saving by multiphase steel and high strength steel: 29 kg

0 1

Wei

ght

savi

ng + 12 kg

- 17 kg

aver

aged

min

. yie

ld

stre

ngth

: 178

N/m

m²

New 3 seriesweight: 267 kg,functionality: 2004

32%

42%

26%

Ave

rage

d m

in. y

ield

st

reng

th: 2

94 N

/mm

²

New 3 seriesweight: 296 kg,functionality: 2004

31%

69%

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H420LA (ZStE 420) H400T (TRIP700)

Severe risk of cracks Formable without cracks

Rp0,2: 420 – 560 N/mm²A80: > 17%

Rp0,2: 400 – 500 N/mm²A80: > 24%

FormingFormability

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Spring back and buckling Steps to preventspring back and buckling(required increase in package volume)

stiffeningbead

Opening of the profile by a certain angle

stiffeningbead

FormingSpring Back and Buckling

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Conventional deep drawing tool

– material: GGG70– insert not essential– not hardened interactive surface

Deep drawing tool for TRIP 700

– inserts essential– CVD coated + hardened inserts– cooling system– increased stiffness

FormingDeep Draw Tooling Considerations

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Multiphase steel:

• increase the diameter of the electrodes

• increase the electrode forces

• adaptation of the weld-ability range

5,5 mm

0 – 15°

Normal steel:

≈ 6-7 mm

0°

Multiphase steel:

t

JoiningElectrode Considerations

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JoiningAdhesive Spot Welding

Vibration test with H400T + Z100 (hot dip galvanized)

1000

10000

1,0E+04 1,0E+05 1,0E+06 1,0E+07

Number of cycles

Am

plitu

de k=4,27

2000

4000

6000

N

07 - The Application of Multiphase Steel in the Body in White

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