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
NEF
Z-G
as C
onsu
mpt
ion
[gC
O2/k
m]
N
EFZ-
Gas
NEF
Z-G
as C
onsu
mpt
ion
Con
sum
ptio
n [g
CO
[gC
O22/k
m]
/k
m]
Gas
Con
sum
ptio
n * [
l/100
km
]G
asG
as C
onsu
mpt
ion
Con
sum
ptio
n * [
l/100
km
] *
[l/10
0 km
]
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”