Great Designs in Steel

Advanced High-Strength Steels in Mercedes-Benz Passenger Cars

Wolfgang Staufner Feb. 19th, 2003

Advanced High Strength Steels in Mercedes-Benz Passenger Cars

• Introduction

• New High Strength Steels

• Application in Mercedes-Benz Cars

• Multi-Material Concept

• Conclusion

• Improvement of crash resistance

• Reduction of fuel consumption

• Optimization of recycling, emission etc.

• Robust processes for high volume production at reduced costs

Ojectives for Material Evolution

Motivation for Weight Savings

120120

140140

160160

180180

200200

220220

240240

5,005,00

6,006,00

7,007,00

8,008,00

9,009,00

10,0010,00

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as C

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ion

[gC

O2/k

m]

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Gas

NEF

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as C

onsu

mpt

ion

Con

sum

ptio

n [g

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[gC

O22/k

m]

/k

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Con

sum

ptio

n * [

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sum

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19921992 19941994 19961996 19981998 20002000 20022002 20042004 20062006 20082008 20102010 20122012

DC-AG Self Commitment : -30%

ACEA Self Commitment: -25%

** Percentage of Percentage of Diesel Diesel Engines approximately Engines approximately ~ 20% ~ 20%

Reduction of Fuel Consumption

020406080

100%

140

C-Class S-Class S-ClassCoupé

Weight Increase of BIW

126 % 109 % 103 %

202

203

140

220

140

215

Overview of Different Steel GradesFo

rmab

ility

Yield Strength0 100 200 300 400 500 600 700 800 900 1000 1100

Low

High

Deep Drawing Steel

Structural Steel

HSLA SteelComplex Phase Steel

Dual Phase Steel

Hot Stamped SteelTRIP Steel

Dual Phase Steel (DP 500/600)

Current applications:• Former E-Class: Reinforcement shocktower

Hinge reinforcement door• C-Class: Engine cross member• E-Class/SLK: Engine cradle rear cross member

Properties:Ferrite, Martensite • Good stretch forming properties due to high

strainhardening

• Good fatigue resistance• Possible for visible parts (continous yielding)

USAB

Current application:•S-class coupé: B-post reinforcement

cross member

Complex Phase Steel (CP 800)

Properties:Ferrite, Martensite and Bainite• Only hot rolled available• High yield strength• Limited formability• Hardened and coated dies necessary• Special steels for cutting necessary• High press forces necessary

TRIP Steel (Transformation Induced Plasticity)

PropertiesRetained Austenite, Ferrite & Martensite• High workhardening potential• Good formability (relative to tensile

strength)• High springback• High press forces necessary• Problems with secondary forming

Will be used:Next A-class, S-class, C-class

For optimum weight savings, simulation of stamping process is necessary

Stre

ss σ

in M

Pa

Strain ε [%]10 20 30 40 500

200

400

600

800

180 AT

050XK

DP500TRIP800

DDQSK

TRIP Steel High Workhardening Potential

TRIP Steel Stamping Try-out

Cracks

• High forces for cutting necessary.

• Cracks after secondary forming.

• Cracks in areas of rectangular blank-cutting after first forming.

• Springback:Mild Steel +0%DP500 +250%TRIP 700 +310%TRIP 800 +420%

Weight reductioncompared to tube1,2kg/vehicle

Martensitic SteelSide Impact Beam

Advantage

Martensitic Steel, Cold Stamped

ThyssenKruppStahl, MSW 1200

Martensitic Steel Hot Stamped

Will be used:Next M-class, S-class, C-class

Properties:• Martensite structure (after hot forming and

quenching in the die)• Forming at 900 °C in one step with no blank

holder• Little forming forces necessary• Relatively complex parts can be formed• Maximum strength through martensitic

structure• No springback due to cooling in the closed

die

TRIP 700 ZE 75/75 PH

DP 500 ZE 75/75

THM 280 Z140

ZStE 340 ZE 75/0

ZStE 180 BH ZE 75/75

Hot Stamping ProcessProduction Line of Sofedit, France

Verstärkungen B-Säule(Usibor 1500 P)

Längsträger(Usibor 1500 P)

Verstärkung B-Säuleunten (ZStE 340)

Possible Applications

1

1. 22MnB5, Hot Dip Aluminized

2

2. Heating 900°C

3

3. Forming and Hardening

4

4. Punching

PSK

KCLK

Better Performance Through Adhesive Bonding

PS

CL

ClinchingClinching

ClinchClinch--bondingbonding

mm

0

5

10

15

0 5 10 15 20

Forc

e F

Elongation s

kN

v = 10 mm/min

Adhesive: BM 1494 Substrat: Mild Steel

Bonazinc/Elo-Zink

ClinchingSpotweldingAdhesive BondingSpotwelding+ABClinching+AB

Multi-Material Concept S-Class Coupe

SteelAluminium

Al-SheetAl-Die-Casting

Al-Extrusions

Al-Die-Casting

Al-Die-CastingAl-ExtrusionsAl-Sheet

Magnesium

Mg-Die-Casting

Plastic

Strong Increase of Aluminum UsageIntroduction of New E-Class

0

5

10

15

20

25

1999 2000 2001 2002 2003

Anu

al A

lum

inum

Usa

ge/ 1

000

t

andere

C-Class

E-Class

SL

S-Class

S-Class, Coupe

Conclusion

•Strong Increase of Advanced High Strength Steels in Future Mercedes-Benz Cars Means:

•Weight Savings with Moderat Cost Increase•Higher Tolerances for Press Parts (High Springback)•Higher Forming Forces•Adopted Joining and Corrosion Protection Technologies Necessary

•Challenging Objectives for Weight-Savings Can Only be Met With Multi-Material Concept

„How much further are these new ideas going

to take us?“

“GREAT DESIGNS IN STEEL”