Advanced High Strength Steels: an economical solution for Automotive Lightweight Structures

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Advanced High Strength Steels: inside an extended steel grade offer for Automotive

Automotive Steel Families

Advanced High Strength Steels: Massive and Growing use in the Automotive Industry

AHSS usage will grow from 7% in 2006 to 11% in 2010, mainly at HSS expenses

A long term potential of 35% of AHSS in a BIW has been estimated through a model study Advanced High Strength SteelsEstimated Market needs> 1 Mt in Europe> 3 Mt in Europe

Car ExampleSource: Eurocarbody46% AHSSEu 4x4 previous modelEu 4x4 new model32% AHSSSource EuroCarBody 2007

Advanced High Strength SteelsWHY?

WHY DOES THE NEED OF AHSS INCREASE ? Reduce CO2 emissions Reduce fuel consumption Safety requirements Equipment & ComfortCar structuremass reduction Downgauging

compensate by higher crash performances of steel Cost effectiveAHSSAHSS are dedicated to Structural partsA-frame reinf.Bumper Beam

Roof bowFront side membersB-pillar reinforcementFloor side reinf. - sill innerRear side member

Example in BrazilFRONTAL Crash regulation in 2010 => would increase need of AHSSEuroncap test as illustration

Car crash situationsSituation where need is to control absorbed energySituation where need is to control intrusion (displacement)

AM test for: Energy absorption under compressive loadClosed-Top-HatSampletest conditionsRecordsFinal specimen observation

Average crushing force for 1.5mm thicknessEnergy Absorption Increased energy absorption with higher UTS Ranking made at iso-part geometry ArcelorMittal 04H260DP450DP500DP600TRIP590HSLA500TRIP690DP780TRIP780MP800DP980LCE TRIP980MP1000 DP1180HY MS1200

AM test for: Maximal Load under 3P bending.Impact speed: 8 m/sKinetic energy : 10 kJ700100140307545f50f50480300SupportImpactor200Sampletest conditions: 3 point bendingrecordsFinal specimen observationDisplacement (mm)Force (kN)Yield forceMaximum force (ulitmate failure stress)

max crushing force for 1.5mm thickness

Strategic Interest in Advanced High Strength Steels (AHSS) for Automotive business is no more a questionBecause it is the most economically efficient solution to reach: Lightweighting goals in structural areas of the car Safety goals in the safety-critical parts Reduce complexity of stamped parts

Example of weight saving potential

Example of Weight saving in Automotive parts: AM generic steel solution catalogue for BodysideReference : 5 doors European vehicle Bodyside Scope

In the solutions catalogue: 1 very efficient proposal for weight savingThis solutionCost : +10%Weight saving : -25%ReferenceA-PILLAR Lower INNER DP600 0.8mm

A-PILLAR R/F Usibor 0.9mm

ROCKER R/F RR + ROCKER R/F FR : DP980 HY 0.85mmA-PILLAR Upper INNER :Trip 780 1.25mmA-PILLAR Upper R/F :Usibor 0.9mmROOF RAIL INNER : DP980HY 0.7mmROOF RAIL R/F DP780 0.6mmB-PILLAR TWB INNER :DP980 HY 1.0 (up)ARC04 0.7 (low)B-PILLAR R/F TWB Usibor 2mm (up) Ductibor 1.6mm (low)ROCKER INNER DP980HY 0.85mm

What kind of steels are AHSS?

AHSS = MULTIPHASE STEELSConventional = ferriticDPTRIPMartensitic1000 : 1 Le Pera20 mStrengthening by quenching generated hard phases: martensite, bainite, retained austeniteFerrite BainiteMP or CP

Steelmaking230 tContinous casting Slabs 25 tHot Rolling millCoils, 25t, length 1000 mRun out tableCooling and coilingCold rolling millHot DipGalvaninzinglineHot Dip galvaninzingproduct(coils, length 2000 m) AHSS = produced by conventional process

Metallurgy of ArcelorMittal AHSSMULTIPHASE structure Manage phase transformation Coupled key factors: PROCESS and CHEMICAL COMPOSITIONPROCESS = control the structure at high temperature + the continuous cooling strip temperatureConventional steels DP steelsTRIP steelstime (s)Area of ferrite formation during coolingArea of Bainite formation during coolingArea of Martensite formation during coolingAdjusted by chemical composition and processingCGL or CAL

DPDPMartTRIPDPMPTRIPFBDPDPFBFBDPFBPHPHPHDPDPTRIPXIPFBFBFBDPMPArcelorMittal WW AHSS offerDP FB MPDP FBFBMPMart : Martensitic gradeDP : Dual Phase (&CP)FB : Ferrite bainiteMP: MultiPhase (CP)PH: Press Hardening gradeTRIP : Transformation Induced PlasticityEURSAMNAMEUR: EuropeSAM: South AmericaNAM: North America

Example of WW offer processus: ArcelorMittal AHSS in Brazil GenericUCEGGIGAASZA/AZEUR & SAM GradeNAM GradeY/TDP450Dual PhaseDP500DP590DP590DP590 HHEDP690 HHEDP780DP780 HHEEURNAMEURNAMEURNAMEURNAMEUREUREUREUREUREUREURNAMNAMEURNAMEUREURNAMNAMEURNAMEURNAMEURNAMEURNAMEUREURTTTTTTTT450500600600600 HHE780780 HHE490590-600590-600590RHFT690780EURDP780 LCET780 LCE780 LCENAMNAMSAMSAMSAMSAMSAMSAMNAMDP780HFLT780HFLEURNAMFB450Ferrite-BainiteFB540FB560FB590FB590 HHEEUREUREUREUREUREUREURTTTTT450540560590590 HHE540SF590SFSAMSAMSAMNAMNAMNAMMP800Multi-PhaseEUREURT800NAMSAMConcept and Know-How are transfered from original region (Eu, US) to Brazil Plant with total technical support => OEM gets locally an equivalent product compared to the original regionHFL: High Fatigue Life, HHE: High Hole Expansion, LCE:Low Carbon Equivalent

Example of WW offer processus: ArcelorMittal AHSS in BrazilExample: Transfer DP600GI from Europe to Brazil (VEGA do Sul)

ArcelorMittal keeps on developing the AHSS familyBecause: OEM needs are already growing for 1000MPa and above grades. At these levels, Steelmaker and OEM must, together, overcome increasing difficulties in part forming, part welding and other in-use properties.

CR DP 980

DP980 with excellent formability/bending combination + good weldabilityDevelopment in Europe and America with Low C/Low CEQof a new DP980 with low C content & improved drawability :Toward low Ceq ~ 0.28-> ~ 0.23Increase drawability : min 0.5t Bendability, +30% Hole Expansion, Robust Weldability

Excellent Combination of Properties:YS 650 MPa, TS 1020 MPa, TE 12-17% (Gauge dependent)Qualified at Multiple Auto ManufacturersUtilized in Vehicles beginning Model Year 2009Applications include B-Pillars, Cross-members, Seat PartsB-Pillar Cross-members

MP800HY, a HR 800MPa steel with good stretch flangeability

MP800HY, a HR 800MPa steel with good stretch flangeabilityM800HYFerrite + Granular bainite

MP800HY, a HR 800MPa steel with good stretch flangeability

MP800HY, a HR 800MPa steel with good stretch flangeabilityGood bendability:Whatever the thickness issimilar behaviour in rolling and transverse direction

Conical hole expansion :Around 60% in averageDevelopment of 85% HE

Dome stretching underlines good formability.

Very good weldabilityPunch diameter : 75mm

MP800HY 3mmHeight without crack25mm

MP800HY 3mmHE at cracking60%

AHSS for roll-forming

ArcelorMittal AHSS Steels 1000 MPa for Roll Forming & bendingDP 1180HY Mid-carbon steel YS ~950MPa, TS ~1200MPa, TE ~5% (ISO)Minimum bend radius of 2t

Martensite 1100 / 1300 / 1500 Lean alloying (C, 0.5Mn)YS ~1000/1150/1300MPa, TS ~1180/1380/1550MPa, TE >3%Minimum bend radius of 4t

Industrial Applications include bumper beams, door beams, rails in multiple vehicle platforms

Press-Hardened Steel: USIBOR1500P a special AHSS

Typical hot-stamping lines

Metallurgical structure after hot-stamping100% martensiticHardness : 400 to 500 HV1Homogeneous mechanical properties in any point of the parts : Ys 1100 MPa, Ts 1500 MPa, E (ISO) 6%USIBOR 1500P

AlSi Coating after hot-stamping

Parts in Usibor 1500P

ArcelorMittal AHSS: ConclusionArcelorMittal has in market an extended and Worldwide Advanced High Strength Steels offer in order toProvide the most effective solution for car structure weight reductionwhere the OEM select and validate material to imagine new cars.where the OEM builds cars.ArcelorMittal keeps on developing new AHSS with further improvementsIn lightweighting potential (higher Grades)In manufacturing properties

Thank you for you Attention

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Le march AUTO est demandeur de AHSS pour des raisons bien claires.La progression des AHSS va continuerIl faut donc fabriquer des AHSS mais sassurer de leur bonne rentabilitExemple pour illustrer sur un vhicule la progression des AHSSLe march AUTO est demandeur de AHSS pour des raisons bien claires.La progression des AHSS va continuerIl faut donc fabriquer des AHSS mais sassurer de leur bonne rentabilit