high-strength steels for chassis and exhaust...

Werkstoff-Forum auf der Hannover Messe 2013

Dr. Lackmann, 09.04.2013 1

High -strength steels for chassis and exhaust components –Application related developments and materials at Benteler Automotive

J. Lackmann, H-G. Lambers, A. Frehn

Benteler Automobiltechnik GmbH, Paderborn

Outline


Dr. Lackmann, 09.04.2013 2

• Benteler Group

• Materials at Benteler Automotive

• Application related materials and developments - Chassis

• Application related materials and developments - Structure

• Application related materials and developments - Exhaust

• Summary

Under the strategic management holding, Benteler International AG, the operative business is organized into the three legally independent business divisions within Benteler Deutschland GmbH.


Dr. Lackmann, 09.04.2013 3

Benteler International AG

Benteler Deutschland GmbH

Benteler Automotive Benteler Stahl/Rohr Benteler Distribution

Worldwide activity – Benteler Automotive 2012


Dr. Lackmann, 09.04.2013 4

� Sales: 5,530 million euros� 22,400 employees� 74 plants, 20 engineering and

sales offices in 29 countries(Status 12/2011)

Status October 2012


Dr. Lackmann, 09.04.2013 5


Dr. Lackmann, 09.04.2013 6

Mat

eria

l-Str

engt

h : R

m /

UT

S [M

Pa] 2000

1000

1500

500

250 App

licat

ion

in s

erie

s pr

oduc

tion

App

licat

ion

appr

oval

in P

PR

Armoring Steel BSEC510

Armoring Steel BSEC610

Boron Steels /

Surface finished

Multi Phase Steels

Micro Alloyed Steels

Stainless Steels

DDQ Steels

AluminiumSheet / Forged

Boronsteels

High manganese

steel

MG-Forged

MG-Sheet

Plastic-Steel-Hybrid

Plastic Foams

Ultra High Strength Alloys

2500

Carbon Fibre

Al-Profile6000-7000-Alloys

Glass Fibre

Armoring Steels

Carbon Fibre

Materials overview


Dr. Lackmann, 09.04.2013 7

Overall application related material requirements

Mechanical – technologicalproperties- Strenght- Hardening behavior- Formability- Modulus- Ductility- Thermo-mechanical properties- Quench propertries

Fatique behavior- Fatique strength- Wöhler diagramms- Crack initiation and - growth

High strain rate behavior- Dynamic strength- Remaining strain- Ballistic resistance

Surface properties- Surface defects- Roughness

Material price- Basic price- Alloying costs

Joining properties- Weldability- Brazeability- Other joining technologies

Corrosion resistance / Coatability- Zinc-coating- Cataphoretic painting- Plasma nitriding- Hot- / wet corrosion properties

„Logistic“ propterties- Available dimensions- Tolerances- Available semi-finished parts- Worldwide availability and quality

Machinability- Die-cutting- Laser-cutting- Drilling


Dr. Lackmann, 09.04.2013 8

Requirement – Formability of high strenght steels

- Formability (including thinning) is a key parameter regardingthe produceability of Benteler Automotive products

- Consistently determined characteristic values are needed forfor forming simulations

- Influence of material characteristics along die- or laser-cuttedholes and edges has to be considered for lifetime prediction

- Increasing the formability of high strength steels desired

- Reduction of the variance of mechanical properties (heat dependend)

Dr. Lackmann, 09.04.2013 9

Requirement – Dimenional tolerances of high strenght stee ls

Example: Roll-rate of compound crank rear axles

• Influencing factors:• Axle kinematics• Shear center of the torsion profile• Effective torsion lenght• Thickness of the torsion element

Influence of thickness torenances

Basis for analytical estimation: B-segment vehicle (VW) (closed profile, D=115mm, t=2,4mm)

t [mm] ∆∆∆∆2,40 -2,45 4,04%2,50 8,19%2,55 12,43%2,60 16,77%2,65 21,21%

Increasing the sheet thickness of the torsion elementresults in highly variing roll-rates and thereforeconsiderable effects on the vehicle dynamics (over-/ understeering)


Dr. Lackmann, 09.04.2013 10

Requirement – Weldability of high strength steels


0

50

100

150

200

250

300

350

400

450

500

0 5 10 15 20 25 30

Messpunkt Nr.

Här

te n

ach

Vic

kers

, H

V0,

5

S420MC-S420MC BAS100(+A)-BAS100 (+A) BAS100 (+QT)-BAS100 (+QT) TRIP800

Grundmaterial GrundmaterialWEZ WEZSchweißgut

MAG-weldseamConsumables:G4Si1 (S420MC/TRIP800)ESAB13.31 (BAS100)

• Maximum allowable hardness within weldseam and heat affected zone is limited by OEMs• Reduction of hardness steps by changing chemical compositions or annealing parameters• Further examination of hydrogen embrittlement required

Dr. Lackmann, 09.04.2013 11

Requirement – Corrosion resistance of high strength steel s


Increasing requirements regarding corrosion resistance andweight reduction

� Standard cataphoretic painting not allways sufficitent

Possible alternatives� Zinc coating (strip)

� Weldseams highly affected

� Zinc coating (part)� Reduction of fatique strength� Weight increase� Hydrogen embrittlement?� LME-risk?

3 years / ca. 95.000 km

TWIP

Austenitic stainless steel

TRIP

DPMagn.

Alum.

CP 22MnB5MS

IFDDQ

IF-HSBH und P

HSLA

IsotropeStähle

Tensile strenght R m, MPa

Elo

ngat

ion

atst

rain

A, %


Dr. Lackmann, 09.04.2013 12

76

1

11

93 HSLA/Baustähle

Austenitischenichtrostende Stähle

Mehrphasenstähle

Benteler-Stahlsorten(BTR165, BAS100)

Andere Stahlsorten

BAS100+A

BAS100+QT

BTR165HR

BTR165+QT

Steel grades used for chassis components

%

Requirement – mechanical properties of high strength stee ls


Dr. Lackmann, 09.04.2013 13

Steel grades used for chassis components – HSLA / mild s teels

Grades:Micro-alloyed and mild steels (Re: 315 – 650 MPa)

Products:Cross member, suspension arms, compound crank rear axles, tube components

Advantages / Disadvantages:+ Low carbon content (weldability – hardness steps)+ Strength / formability ratio+ Minimal variation of mechanical properties within rolled strip+ Different strength levels available+ Worldwide available (Hot- and cold rolled strip)- Reduced formability and springback for high-strentgh grades

Development trends:- Further reduction of grain- and precipitation size (Nano-Hiten)- Perlite-free variants showing increased formability(HSM650HD)


Dr. Lackmann, 09.04.2013 14

Steel grades used for chassis components – multiphase ste els

Grades:F/B540, F/B590, F/B780, SZBS800, CP-W800, DP450

Products:Suspension arms, reinforcements

Vorteile/Nachteile:Similar to HSLA / mild steel+ Improved formability and hardening potential+ Significant bake-hardening effect+ Improved hole expensionalbility (FB)- Wordwide availability(different concepts DP/TRIP)- Springback for HSS-grades- Weldeability for TRIP-steel- Hot rolled strip availability for DP/TRIP

Development trends:- Further optimization of F/B-grades- Reduction of C-content of TRIP-steels


Dr. Lackmann, 09.04.2013 15

Steel grades used for chassis components – air hardening s teels

Grades:BAS100, BNX120 (Re: 700 Mpa – 850 MPa)

Komponenten:Front subframe

Vorteile/Nachteile:+ High formability in the not hardenend condition combined with

high strength of hardened parts+ No significant hardness steps within the heat affected zone- Alloying costs (Mo und V)- Wordwide availability

Development trends at Benteler:- Optimization of mechanical properties and availability


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Competitor to steel - Aluminium grades used for chassis co mponentsComponent Alloys Condition Strenght Elongation at break

Extruded profiles EN AW-6060EN AW-6005AEN AW-6063

T6 bzw. T5 Re > 225 MPaRm > 270 MPa

A5 > 8%

HF welded tubes EN AW-5454EN AW-5457

H111 Re > 100 MPaRm > 230 MPa

A5 > 20%

Casted parts EN AC-42100 T6 Re > 190 MPaRm > 230 MPa

A5 > 2%

Sheets for pressedparts

EN AW-5454EN AW-5457

H111, H22 and higher

Re > 200 MPaRm > 270 MPa

A5 > 11%

Forged parts EN AW-6062EN AW-6110(Cu limited)

T6 Re > 370 MPaRm > 400 MPa

A5 > 9%

High strength: 300-400 MPa (Rm)Ultra high strenght: > 400 MPa (Rm)


Dr. Lackmann, 09.04.2013 17

Potential future steel grades for chassis components

? ? ?

NANO-HITEN, TWIP - steels Steels showing increased elas tic modulus

Reference: JFE, Japan Reference: ArcelorMittal

„Low cost“- air hardening steel, Bainite

Reference: Microstructure of the BSR05-10 (air hardened)


Dr. Lackmann, 09.04.2013 18

High strength steels for hot formed structural components and ballisticprotection systems

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

0 5 10 15 20 25 30 35 40 45 50

Bruchdehnung [%]

Zug

fest

igke

it [M

pa]

DDQ, UDDQ

P, BH, IFHSHSLA

FB

DPTRIP

CPPM BTR165 hot formed

BTR165

hot rolledHS

SU

HS

SP

HS

BSEC510 hot formed

BSEC610 hot formed

Strain [%]

Tesi

le s

tres

s [M

Pa]

Perlite

Bainite

Martensite

Martensite

Time (0 -1000 s, log)

Tem

pera

ture

(0

-10

00 C

)

TTT-Diagramm

Ac3

Cooling

Transformation

Ferrite

Ms

Mf


Dr. Lackmann, 09.04.2013 19

Partial hardening of high strength steels for structural components

transition T2

duct

ile

T3

high

str

engt

h

T1

0Vickers hardness

dist

ance

•HV0,5

500

Martensite

Ferrite + Perlite

Martensite + Bainite

advantage:strength optimized design properties:

quenched sec.: soft sec.:Rm: 1450 MPa 550 MPa

Re: 1100 MPa 400 MPa

ε (A5): > 6 % > 20%

� good crash performance

� weight reduction

� Part integration

T3

T2Temp 3

Direction of material flow

Temp 1 Temp 2


Dr. Lackmann, 09.04.2013 20

Hot formable ultra high strength steels for ballistic pro tection components

Benteler Security Steel (BSEC) // C – Cr – Ni – Mn base d

Benteler steel plant Lingen

BSEC-grades available

BSEC450

Hardness [HB] Impact work [J] Application

410 - 480 40 - 60 Floor parts

BSEC510 480 - 550 25 - 40 Vehicle protection up to STANAG I

BSEC610 570 - 640 10 - 15 Vehicle protection up to STANAG III

BSEC+ Surface hardened BSEC-grades for additional ballistic resistance


Dr. Lackmann, 09.04.2013 21

Hot formable ultra high strength steels for ballistic pro tection components

Ballistic protection up to t = 20 mm by fully martensitic microstructure

Parts integration / avoidance of constructional vulnerabilities

Development trends at Benteler:- Reduction of alloying costs- Reduction of CEV


Dr. Lackmann, 09.04.2013 22

High Temperature Resistant Ferritic Steel for Exhaus t Application

Reference: ThyssenKrupp Nirosta

BMBF-Project

RUB

Objective: Development of high temperature resistant (quasistatic and thermo mechanical fatique) ferritic stainless steel for exhaust applications, based on Laves – phase precipitation� Close the gap regarding high temperature mechanical properties betweenaustenitic and ferritic stainless steel at cost of ferritc steels

Idea: Manipulation of laves phase andcarbonitride precipitation behavior and solvustemperatures by molybdenum-, tungsten-, silicon- and niobium content � Reliable grain stabilization up to applicationtemperatures of 950°C


Dr. Lackmann, 09.04.2013 23

High Temperature Resistant Ferritic Steel for Exhaus t Application

Ferrite950 C Si Mn Cr Mo W V Nb Ti N

ma-% < 0,02 ≈ 0,6 ≈ 0,4 ≈ 18 ≈ 0,5 ≈ 1,5 ≈ 0,1 ≈ 0,8 < 0,1 < 0,05

Laves-phase -(Fe, Cr, Si) 2(Nb, W, Mo)

415

488

548

0 100 200 300 400 500 600 700Zyklen Nf

Ferrite 950

1.4521

1.4509

Ferrite 950 grade: Laves phase and carbonitrides precipitates stabilize grains up to 1000°CThermo-mechanical properties significantly improvedExcellent wet- and hot corrosion resistance� Potential material for components exposed to high exhaust temperatures (downsized engines)

Development activities at Benteler:- Further validation tests on prototypes (manifolds, pipes, converter)


Dr. Lackmann, 09.04.2013 24

Summary

Chassis componentsSteel grades with different mechanical strenght will b e the first choice for many chassis componentsHSLA and mulitphase steel are predominantly usedFor components, where rigidity is most important, an inc rease of the elastic modulus is desired

Hot formed structural components and ballistic protectio n systemsPartial hardening of MnB – steel grades allows for tailori ng mechanical propteries within a wide rangeHot formable ultra high strength steels are used for balli stic protection systemsThe reduction of alloying costs while maintaining strengh t-ductility characteristics is attempted

Exhaust componentsChromium oxide based austenitic and ferritic stainless ste el grades are predominantly used for exhaustcomponentsFerritic stainless steel Ferrite 950 is a potential mat erial for closing the gap between austenitic and ferriticstainless steels

FVK / AluminiumFVK (glass / carbon) are getting more and more important f or chassis (e.g. leave-spring) as well as structuralcomponents (e.g. reinforcements) – Joint venture Bente ler – SGLAluminium (5xxx / 6xxx ) is increasingly used for chass is and strucutral components– Benteler Aluminium Systems

high-strength steels for chassis and exhaust...

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