Guidelines for the Manufacture of Advanced High...

Guidelines for the Manufacture of Advanced

Dr. Chris Lahaije, Sascha SikoraAachen, 2014-09-24

High-Strength Steel Vehicle Applications

Aachen, 2014 09 24

A t ti G f th W ld St l A i tiWorldAutoSteel

Automotive Group of the World Steel Association

MEMBER COMPANIES:

Ansteel NucorArcelorMittal POSCOBaosteel SeverstalChina Steel SSABJFE T t St lJFE Tata Steel JSW Steel ThyssenKruppHyundai Steel USIMINASyKobe U. S. SteelNippon Steel & Sumitomo voestalpine

Lightweighting with AHSS: A li ti G id li 5 0

3

Application Guidelines 5.0

A li ti G id li 5 011 Application Guidelines 5.01

2 Key Challenges with AHSS - Forming

1

Key Challenges with AHSS - Joining

2

3

y g g

Case study; CP800 for high energy absorption44

Case study; HF1900 for hot forming5

Lightweighting with AHSS: Application Guidelines 5.0

AHSS METALLURGY, FORMINGOur Technical Editors

Key Enablers: y• Development of new grades of AHSS that meet

today’s functional performance and lightweighting needs

Dr. Stu Keeler,Keeler Technologies

• Information that allows our stakeholders to successfully apply these highly sophisticated materials

AHSS JOINING

DMS 1150/1400

Professor M KimchiD

D

/

MS 950/1200

DP 700/1000 Professor M. Kimchi,Ohio State University

Lightweighting with AHSS

Can Steel Continue to Provide Competitive MaterialsSolutions for the Automotive Industry?

FutureSteelVehicle (FSV)

A2mac1 benchmarking

Cadillac ATS, VW Golf


Key Elements of Version 5.0


1. New Materials• Building on FSV our materials• Building on FSV, our materials

portfolio now includes 50 steel grades, compared with 28 in Version 4 0 And still growingVersion 4.0. And still growing...

• Exposed surface quality successachieved with DP steels up to 600 Mpa

• Greater ductility in DP, CP and HSLA (based on nano precipitation) grades for lighter gage forming

Available at www.worldautosteel.org


Materials PortfolioApplication Guidelines 5.0

DP 210/440 IF 260/410 BH 280/400 IF 300/420

HSLA 490/600DP 500/800CP 500/800HSLA 550/650

TRIP 750/980 TWIP 750/1000CP 800/1000DP 800/1180

ULSAB AVC GradesFutureSteelVehicleV5 0 New GradesIF 300/420

DP 300/500FB 330/450DP 350/600

HSLA 550/650CP 600/900TWIP 600/900DP 600/980

DP 800/1180CP 850/1180MS 950/1200TWIP 950/1200

V5.0 New Grades

TRIP 350/600TRIP 400/700HSLA 420/500FB 450/600

TRIP 600/980CP 680/780HSLA 700/780DP 700/1000

CP 1000/1200MS 1050/1470CP 1050/1470HF 1050/1500FB 450/600

TRIP 450/800TWIP 480/900

DP 700/1000CP 750/900DP 750/980

HF 1050/1500DP 1150/1270HF 1200/1900






2. Updated Fabrication Technologies• Servo presses for programmable forming

• Press-hardened steels (hot forming)

• Tool & die maintenance practices

• Laser welded blanks, roll forming, , g,hydroforming, etc.






3. Significant Joining RevisionF 30 t 110• From 30 pages to 110 pages

• Partnership with automotive OEMs, technical i tiorganizations

• New joining processes with unique qualities li bl t AHSS d l ldiapplicable to AHSS grades – laser welding,

hybrid welding, mechanical joining and adhesive bonding


Key Challenges with AHSS

MaterialsMaterials Understanding of material behavior Development of qualification procedures Develop materials specifications F i Forming Predictable make-ability, e.g.Springback, edge cracking Process robustness Joiningg Process and parameters development Design for AHSS Static and dynamic weld performance Development of accurate FEA toolsDevelopment of accurate FEA tools Successful plant implementation

Key Challenges with AHSS - FormingSpring-back in AHSS

Open-ended Section Comparison

Key Challenges with AHSS – Forming

Low r-value might prompt larger die clearance, to avoid jamming….

Draw die clearance in AHSSg g j g

But too large a clearance will cause materials to reverse bend over a large area increasing severity of side wall curl


Conventional HSS can be folded without issues.

Bendability

This is not the case with AHSS

Two ways of characterising the performance of the material Minimum bend radius Bend angle in VDA-238 test


The forming of sheared edges is more challenging than in mild steel

Edge ductilityg g g g

or HSS E.g. stretch flanging

Because the process is more critical the sensitivity to tool wear also Because the process is more critical the sensitivity to tool wear also becomes a concern


AHSS present a compromise

Formability = Stretchability & Bendability

Improving both aspects a bit or one aspect a lot.

Stretch-DP800 DHDP800 DH

Stretchability

DP1000 DH

DP1000 DH

DP600 DP800DP800Form-ability

DP1000

CP1000

DP1000

CP1000

CP800CP800

Increasing Rm

Bend-ability

CP1000CP1000

P d t d l tKey Challenges with AHSS - Joining

Process and parameter development

Possible solutions to Improve Peel behavior on AHSS Spot Welds

Passive methods Long weld time

Electrode Force

p p

Pre/post pulsing Short hold time

I d i i Increased minimum weld size

Active methodsWeld

Down Slope Quench Temper Hold

DilutionActive methodsWeld and temper Dilution (AHSS to Mild

Dilution Weld

Steel, HSLA)

P d d l

Key Challenges with AHSS - JoiningProcess and parameter development

Effect of Temper and dilution on fracture mode

5

No Temp, No Diln Temp OnlyDiln Only Temp & Diln

0%

actu

re

3

4

pear

ance

10%

rfac

ial F

ra

1

2

3

ctur

e A

pp20%

50%Are

a In

ter

0

1

Frac

Tensile Stat X Dyn X Chisel100%

% A

TensileShear

Stat XTensile

Dyn XTensile

Chisel

S f

Key Challenges with AHSS - JoiningSelection of joining technique

Body-in-White joining processes

Resistance spot Projection welding GMAW MIG brazing Laser welding (TWB) Mechanical fastening Magnetic pulse welding Deformation resistance

welding

S f

Key Challenges with AHSS - Joining

• Comparison between spot welds and 20 mm laser welds• Laser weld performance varies with width / sheet thickness ratio

Selection of joining technique

Max. Tensile Load

DP-Wide

• Laser weld performance varies with width / sheet thickness ratio

TP-Remote

TP-Wide

DP-Spot

DP-Narrow

DP-Remote

Laser - 2.5 m/min (wide)

MS-Narrow

MS-Remote

MS-Wide

TP-Spot

TP-Narrow

All G id d

Laser - Remote 4.8 m/min

0 500 1000 1500 2000 2500 3000 3500 4000

MS-Spot

MS-Spot MS-Narrow MS-Remote MS-WideTP-Spot TP-Narrow TP-Remote TP-Wide

All Guided

Laser 10 m/min (narrow)DP-Spot DP-Narrow DP-Remote DP-Wide

Laser - 10 m/min (narrow)

P t l d lit it iKey Challenges with AHSS - Joining

Process monitoring Nondestructive evaluation

Process control and quality monitoring

g

Strain Gauge

PressureTransducers

LVDTs

Current Toroid

VoltageLeadsToroid Leads

W ld lit it iKey Challenges with AHSS - Joining

Planar Metallographic Imaging Criteria

Destructive testing – fracture modeWeld quality monitoring

Peel and Chisel Criteria - Failure ModesButton pulled without evidence of interfacial fracture

Partial thickness fracture with button pull

Partial thickness fracture with no button pull

Interfacial fracture with button pull and partial thickness fracture

Full interfacial Fracture No fusionInterfacial fracture with button pull

Interfacial fracture with partial thickness fracture

22Study of fracture behaviour Closed-Top-Hat

In crushing of Closed-Top-Hat, bending is very apparent fracture occurs next to the original cornersfracture occurs next to the original corners few cracks seen in zones with only bending cracks in relatively flat areasCl t d f f t l ti d f t Closer study of fracture location and fracture appearance indicated that shear fractureis very important

Bending and shear properties 23

Failure strain in 3 point bend test Failure strain in shear test

0.50

0.60

0.70

strain

0.25

0.30

0.35

rain

0.10

0.20

0.30

0.40

Bend

ing failure s

0.05

0.10

0.15

0.20

Shear failure str

• CP800HE significant better shear• CP grades better bending

0.00DP800HpF CP800 CP800HE

0.00DP800HpF CP800 CP800HE

CP800HE significant better shear performance

CP grades better bending performance compared to DP

Combination of high bending and high shear failure strain for CP800HE Combination of high bending and high shear failure strain for CP800HE results in good crash behaviour

The value of crash-ability: CP800 High Energy absorption

24

CP800 High Energy absorptionCP800 HE

High strength level with good crashability

• CP800 HE is within specifications of CP800 grade but with improved crash properties:

CP800HE DP800HpFCP800

The improved crash-ability of CP800HE create value in terms of weight The improved crash-ability of CP800HE create value in terms of weight saving compared to DP800 for crash structures

Hot Formed Steels

Material behaviour at the manufacturing process Exemplary benefits of Hot Forming:- Springback issues

eliminated, which is remarkable considering the extremely high final part strength. 2part strength.

- Very high strength resists stamping deformation

- Hot-forming has the 1

3g

highest potential for weight reduction of crash components.

- Controlling the 1

3

32Controlling the temperature in various locations of the forming die can create zones with different strength levels in th fi l t i

25

the final stamping.

Structural Elements of Passenger Compartment

Lightweight solutions by using hot formed components Used for safety critical parts, especially for maintaining a passenger

i l i h l tsurvival space in crash elements

140

+15%to

25%

A-pillar upperB-pillarC-pillar

1 2 3

80

100

120

140 +25% -5%to

-10%

-10%to

-15%-20%

to-30%

-25%to

-35%

C pillarSide impact beamTunnelCrossmemberrear seat

4 5 6

REF

0

20

40

60rear seatCrossmemberfirewallLong memberA-pillar lower

7

8 9 0A-pillar lower

SillBumperLong member rear

9 101112

26

Crossmember roof13

HF 1200/1900: increased strength for lightweight potentialincreased strength for lightweight potential Improvement of crash

performanceQuasistatic bending test

After following tempering process to increase ductility High deformation resistance

Potential processes Cataphoretic painting process / paint

shopshop Separated tempering process

Typical temperatures and process times 160° C to 190° C / 20 to 30 minutes 200° C to 250° C / 15 to 30 minutes

HF 1050/1500 HF 1200/1900

HF 1200/1900 HF 1200/1900200 C to 250 C / 15 to 30 minutes

27

Guidelines for the Manufacture of Advanced High...

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